1
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Altundemir S, Lashkarinia SS, Pekkan K, Uğuz AK. Interstitial flow, pressure and residual stress in the aging carotid artery model in FEBio. Biomech Model Mechanobiol 2024; 23:179-192. [PMID: 37668853 DOI: 10.1007/s10237-023-01766-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2023] [Accepted: 08/16/2023] [Indexed: 09/06/2023]
Abstract
Vascular smooth muscle cells (VSMCs) are subject to interstitial flow-induced shear stress, which is a critical parameter in cardiovascular disease progression. Transmural pressure loading and residual stresses alter the hydraulic conductivity of the arterial layers and modulate the interstitial fluid flux through the arterial wall. In this paper, a biphasic multilayer model of a common carotid artery (CCA) with anisotropic fiber-reinforced soft tissue and strain-dependent permeability is developed in FEBio software. After the verification of the numerical predictions, age-related arterial thickening and stiffening effects on arterial deformation and interstitial flow are computed under physiological geometry and physical parameters. We found that circumferential residual stress shifts outward in each layer and its gradient increases up to 6 times with aging. Internally pressurized CCA displays nonlinear deformation. In the aged artery, the circumferential stress becomes greater on the media layer (82-158 kPa) and lower on the intima and adventitia (19-23 kPa and 25-28 kPa, respectively). The radial compression of the intima reduces the total hydraulic conductivity by 48% in the young and 16% in the aged arterial walls. Consequently, the average radial interstitial flux increases with pressure by 14% in the young and 91% in the aged arteries. Accordingly, the flow shear stress experienced by the VSMCs becomes more significant for aged arteries, which may accelerate cardiovascular disease progression compared to young arteries.
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Affiliation(s)
- Sercan Altundemir
- Department of Chemical Engineering, Boğaziçi University, Istanbul, 34342, Turkey.
| | - S Samaneh Lashkarinia
- Department of Bioengineering, Imperial College London, London, SW7 2AZ, UK
- Department of Mechanical Engineering, Koç University, Istanbul, 34450, Turkey
| | - Kerem Pekkan
- Department of Mechanical Engineering, Koç University, Istanbul, 34450, Turkey
| | - A Kerem Uğuz
- Department of Chemical Engineering, Boğaziçi University, Istanbul, 34342, Turkey.
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2
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Li GJ, Yang QH, Yang GK, Yang G, Hou Y, Hou LJ, Li ZX, Du LJ. MiR-125b and SATB1-AS1 might be shear stress-mediated therapeutic targets. Gene 2023; 857:147181. [PMID: 36623676 DOI: 10.1016/j.gene.2023.147181] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2022] [Revised: 12/20/2022] [Accepted: 01/04/2023] [Indexed: 01/09/2023]
Abstract
The aim of the study was to explore the potential molecular mechanism associated with shear stress on abdominal aortic aneurysm (AAA) progression. This study performed RNA sequencing on AAA patients (SQ), AAA patients after endovascular aneurysm repair (EVAR, SH), and normal controls (NC). Furthermore, we identified the differentially expressed microRNAs (miRNAs), long noncoding RNAs (lncRNAs), and circular RNA (cirRNAs) and constructed competing endogenous RNA (ceRNA) networks. Finally, 164 differentially expressed miRNAs, 179 co-differentially expressed lncRNAs, and 440 co-differentially expressed circRNAs among the three groups were obtained. The differentially expressed miRNAs mainly enriched in 325 Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. Target genes associated with co-differentially expressed genes among the group of SH, SQ, and NC mainly enriched in 66 KEGG pathways. LncRNA-miRNA-mRNA interactions, including 15 lncRNAs, 63 miRNAs and 57 mRNAs, was constructed. CircRNA-miRNA-mRNA ceRNA network included 79 circRNAs, 21 miRNAs, and 49 mRNAs. Among them, KLRC2 and CSTF1, targeted by miR-125b, participated in cell-mediated immunity regulation. MiR-320-related circRNAs and SATB1-AS1 serving as the sponge of miRNAs, such as has-circ-0129245, has-circ-0138746, and has-circ-0139786, were hub genes in ceRNA network. In conclusion, AAA patients might be benefit from EVAR based on various pathways and some molecules, such as miR-125b and SATB1-AS1, related with shear stress.
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Affiliation(s)
- Guo-Jian Li
- Department of Vascular Surgery, Affiliated Hospital of Yunnan University, Kunming 650021, Yunnan, China
| | - Qiong-Hui Yang
- Department of Pharmaceutical, The Third People's Hospital of Yunnan Province, Kunming 650011, Yunnan, China
| | - Guo-Kai Yang
- Department of Vascular Surgery, Affiliated Hospital of Yunnan University, Kunming 650021, Yunnan, China
| | - Guang Yang
- Department of Radiology, the First People's Hospital of Anning, China
| | - Yi Hou
- Department of Vascular Surgery, Affiliated Hospital of Yunnan University, Kunming 650021, Yunnan, China
| | - Li-Juan Hou
- Department of Vascular Surgery, Affiliated Hospital of Yunnan University, Kunming 650021, Yunnan, China
| | - Zhao-Xiang Li
- Department of Vascular Surgery, Affiliated Hospital of Yunnan University, Kunming 650021, Yunnan, China
| | - Ling-Juan Du
- Department of Vascular Surgery, Affiliated Hospital of Yunnan University, Kunming 650021, Yunnan, China.
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3
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Kozakova M, Palombo C. Vascular Ageing and Aerobic Exercise. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2021; 18:10666. [PMID: 34682413 PMCID: PMC8535583 DOI: 10.3390/ijerph182010666] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Revised: 10/06/2021] [Accepted: 10/07/2021] [Indexed: 12/15/2022]
Abstract
Impairment of vascular function, in particular endothelial dysfunction and large elastic artery stiffening, represents a major link between ageing and cardiovascular risk. Clinical and experimental studies identified numerous mechanisms responsible for age-related decline of endothelial function and arterial compliance. Since most of these mechanisms are related to oxidative stress or low-grade inflammation, strategies that suppress oxidative stress and inflammation could be effective for preventing age-related changes in arterial function. Indeed, aerobic physical activity, which has been shown to improve intracellular redox balance and mitochondrial health and reduce levels of systemic inflammatory markers, also improves endothelial function and arterial distensibility and reduces risk of cardiovascular diseases. The present paper provides a brief overview of processes underlying age-related changes in arterial function, as well as the mechanisms through which aerobic exercise might prevent or interrupt these processes, and thus attenuate vascular ageing.
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Affiliation(s)
- Michaela Kozakova
- Department of Clinical and Experimental Medicine, University of Pisa, 56124 Pisa, Italy;
| | - Carlo Palombo
- Department of Surgical, Medical, Molecular Pathology and Critical Care Medicine, University of Pisa, 56124 Pisa, Italy
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4
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Grégory Franck. Role of mechanical stress and neutrophils in the pathogenesis of plaque erosion. Atherosclerosis 2020; 318:60-69. [PMID: 33190807 DOI: 10.1016/j.atherosclerosis.2020.11.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Revised: 10/05/2020] [Accepted: 11/03/2020] [Indexed: 02/05/2023]
Abstract
Mechanical stress is a well-recognized driver of plaque rupture. Likewise, investigating the role of mechanical forces in plaque erosion has recently begun to provide some important insights, yet the knowledge is by far less advanced. The most significant example is that of shear stress, which has early been proposed as a possible driver for focal endothelial death and denudation. Recent findings using optical coherence tomography, computational sciences and mechanical models show that plaque erosion occurs most likely around atheromatous plaque throats with specific stress pattern. In parallel, we have recently shown that neutrophil-dependent inflammation promotes plaque erosion, possibly through a noxious action on ECs. Most importantly, spontaneous thrombosis - associated or not with EC denudation - can be impacted by hemodynamics, and it is now established that neutrophils promote thrombosis and platelet activation, highlighting a potential relationship between, mechanical stress, inflammation, and EC loss in the setting of coronary plaque erosion. Here, we review our current knowledge regarding the implication of both mechanical stress and neutrophils, and we discuss their implication in the promotion of plaque erosion via EC loss and thrombosis.
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Affiliation(s)
- Grégory Franck
- Inserm LVTS U1148. CHU Bichat, 46 Rue Henri Huchard, 75018, Paris, France.
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5
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Jeong Y, Yao Y, Yim EKF. Current understanding of intimal hyperplasia and effect of compliance in synthetic small diameter vascular grafts. Biomater Sci 2020; 8:4383-4395. [PMID: 32643723 PMCID: PMC7452756 DOI: 10.1039/d0bm00226g] [Citation(s) in RCA: 42] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Despite much effort, synthetic small diameter vascular grafts still face limited success due to vascular wall thickening known as intimal hyperplasia (IH). Compliance mismatch between graft and native vessels has been proposed to be one of a key mechanical factors of synthetic vascular grafts that could contribute to the formation of IH. While many methods have been developed to determine compliance both in vivo and in vitro, the effects of compliance mismatch still remain uncertain. This review aims to explain the biomechanical factors that are responsible for the formation and development of IH and their relationship with compliance mismatch. Furthermore, this review will address the current methods used to measure compliance both in vitro and in vivo. Lastly, current limitations in understanding the connection between the compliance of vascular grafts and the role it plays in the development and progression of IH will be discussed.
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Affiliation(s)
- YeJin Jeong
- Department of Chemical engineering, University of Waterloo, 200 University Ave W, Waterloo, ON N2L 3G1, Canada.
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6
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van Haaften EE, Wissing TB, Kurniawan NA, Smits AIPM, Bouten CVC. Human In Vitro Model Mimicking Material-Driven Vascular Regeneration Reveals How Cyclic Stretch and Shear Stress Differentially Modulate Inflammation and Matrix Deposition. ACTA ACUST UNITED AC 2020; 4:e1900249. [PMID: 32390338 DOI: 10.1002/adbi.201900249] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2019] [Revised: 03/12/2020] [Accepted: 04/15/2020] [Indexed: 12/12/2022]
Abstract
Resorbable synthetic scaffolds designed to regenerate living tissues and organs inside the body have emerged as a clinically attractive technology to replace diseased blood vessels. However, mismatches between scaffold design and in vivo hemodynamic loading (i.e., cyclic stretch and shear stress) can result in aberrant inflammation and adverse tissue remodeling, leading to premature graft failure. Yet, the underlying mechanisms remain elusive. Here, a human in vitro model is presented that mimics the transient local inflammatory and biomechanical environments that drive scaffold-guided tissue regeneration. The model is based on the coculture of human (myo)fibroblasts and macrophages in a bioreactor platform that decouples cyclic stretch and shear stress. Using a resorbable supramolecular elastomer as the scaffold material, it is revealed that cyclic stretch initially reduces proinflammatory cytokine secretion and, especially when combined with shear stress, stimulates IL-10 secretion. Moreover, cyclic stretch stimulates downstream (myo)fibroblast proliferation and matrix deposition. In turn, shear stress attenuates cyclic-stretch-induced matrix growth by enhancing MMP-1/TIMP-1-mediated collagen remodeling, and synergistically alters (myo)fibroblast phenotype when combined with cyclic stretch. The findings suggest that shear stress acts as a stabilizing factor in cyclic stretch-induced tissue formation and highlight the distinct roles of hemodynamic loads in the design of resorbable vascular grafts.
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Affiliation(s)
- Eline E van Haaften
- Dr. E. E. van Haaften, Dr. T. B. Wissing, Dr. N. A. Kurniawan, Dr. A. I. P. M. Smits, Prof. C. V. C. Bouten, Department of Biomedical Engineering, Eindhoven University of Technology, P.O. Box 513, Eindhoven, 5600 MB, the Netherlands.,Dr. E. E. van Haaften, Dr. T. B. Wissing, Dr. N. A. Kurniawan, Dr. A. I. P. M. Smits, Prof. C. V. C. Bouten, Institute for Complex Molecular Systems (ICMS), Eindhoven University of Technology, P.O. Box 513, Eindhoven, 5600 MB, the Netherlands
| | - Tamar B Wissing
- Dr. E. E. van Haaften, Dr. T. B. Wissing, Dr. N. A. Kurniawan, Dr. A. I. P. M. Smits, Prof. C. V. C. Bouten, Department of Biomedical Engineering, Eindhoven University of Technology, P.O. Box 513, Eindhoven, 5600 MB, the Netherlands.,Dr. E. E. van Haaften, Dr. T. B. Wissing, Dr. N. A. Kurniawan, Dr. A. I. P. M. Smits, Prof. C. V. C. Bouten, Institute for Complex Molecular Systems (ICMS), Eindhoven University of Technology, P.O. Box 513, Eindhoven, 5600 MB, the Netherlands
| | - Nicholas A Kurniawan
- Dr. E. E. van Haaften, Dr. T. B. Wissing, Dr. N. A. Kurniawan, Dr. A. I. P. M. Smits, Prof. C. V. C. Bouten, Department of Biomedical Engineering, Eindhoven University of Technology, P.O. Box 513, Eindhoven, 5600 MB, the Netherlands.,Dr. E. E. van Haaften, Dr. T. B. Wissing, Dr. N. A. Kurniawan, Dr. A. I. P. M. Smits, Prof. C. V. C. Bouten, Institute for Complex Molecular Systems (ICMS), Eindhoven University of Technology, P.O. Box 513, Eindhoven, 5600 MB, the Netherlands
| | - Anthal I P M Smits
- Dr. E. E. van Haaften, Dr. T. B. Wissing, Dr. N. A. Kurniawan, Dr. A. I. P. M. Smits, Prof. C. V. C. Bouten, Department of Biomedical Engineering, Eindhoven University of Technology, P.O. Box 513, Eindhoven, 5600 MB, the Netherlands.,Dr. E. E. van Haaften, Dr. T. B. Wissing, Dr. N. A. Kurniawan, Dr. A. I. P. M. Smits, Prof. C. V. C. Bouten, Institute for Complex Molecular Systems (ICMS), Eindhoven University of Technology, P.O. Box 513, Eindhoven, 5600 MB, the Netherlands
| | - Carlijn V C Bouten
- Dr. E. E. van Haaften, Dr. T. B. Wissing, Dr. N. A. Kurniawan, Dr. A. I. P. M. Smits, Prof. C. V. C. Bouten, Department of Biomedical Engineering, Eindhoven University of Technology, P.O. Box 513, Eindhoven, 5600 MB, the Netherlands.,Dr. E. E. van Haaften, Dr. T. B. Wissing, Dr. N. A. Kurniawan, Dr. A. I. P. M. Smits, Prof. C. V. C. Bouten, Institute for Complex Molecular Systems (ICMS), Eindhoven University of Technology, P.O. Box 513, Eindhoven, 5600 MB, the Netherlands
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7
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Cai C, Zhao C, Kilari S, Sharma A, Singh AK, Simeon ML, Misra A, Li Y, Misra S. Effect of sex differences in treatment response to angioplasty in a murine arteriovenous fistula model. Am J Physiol Renal Physiol 2019; 318:F565-F575. [PMID: 31813252 DOI: 10.1152/ajprenal.00474.2019] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Failure to mature and venous neointimal hyperplasia formation are the two major causes of hemodialysis arteriovenous fistula (AVF) vascular access failure. Percutaneous transluminal angioplasty (PTA) is the firstline treatment for both of these conditions, but, clinically, women have decreased patency rates compared with men. The hypothesis to be tested in the present study was that female mice after PTA of venous areas of higher intimal thickening have increased gene expression of transforming growth factor-β1 (TGF-β1) and TGF-β receptor 1 (TGFβ-R1) accompanied with histological changes of fibrosis compared with male mice. Seventeen male and eighteen female C57BL/6J mice were used in this study. Chronic kidney disease was induced by partial nephrectomy, and, 28 days later, an AVF was created to connect the left carotid artery to the right jugular vein. Two weeks later, the higher intimal thickening area was treated with PTA, and mice were euthanized 3 days later for gene expression analysis or 14 days later for histopathological analysis. Doppler ultrasound was performed weekly after AVF creation. At day 3, female AVF had significantly higher average gene expression of TGF-β1 and TGFβ-R1 compared with male AVF. At day 14, female outflow veins had a smaller venous diameter, lumen vessel area, decreased wall shear stress, lower average peak systolic velocity, and an increased neointima area-to-media area ratio. Moreover, female outflow veins showed a significant increase in α-smooth muscle actin and fibroblast-specific protein-1. There was a decrease in M1/M2 with an increase in CD68.
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Affiliation(s)
- Chuanqi Cai
- Department of Vascular Surgery, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.,Vascular and Interventional Radiology Translational Laboratory, Department of Radiology, Mayo Clinic, Rochester, Minnesota
| | - Chenglei Zhao
- Vascular and Interventional Radiology Translational Laboratory, Department of Radiology, Mayo Clinic, Rochester, Minnesota.,Department of Vascular Surgery, The Second Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Sreenivasulu Kilari
- Vascular and Interventional Radiology Translational Laboratory, Department of Radiology, Mayo Clinic, Rochester, Minnesota
| | - Amit Sharma
- Vascular and Interventional Radiology Translational Laboratory, Department of Radiology, Mayo Clinic, Rochester, Minnesota
| | - Avishek K Singh
- Vascular and Interventional Radiology Translational Laboratory, Department of Radiology, Mayo Clinic, Rochester, Minnesota
| | - Michael L Simeon
- Vascular and Interventional Radiology Translational Laboratory, Department of Radiology, Mayo Clinic, Rochester, Minnesota
| | - Avanish Misra
- Vascular and Interventional Radiology Translational Laboratory, Department of Radiology, Mayo Clinic, Rochester, Minnesota
| | - Yiqing Li
- Department of Vascular Surgery, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Sanjay Misra
- Vascular and Interventional Radiology Translational Laboratory, Department of Radiology, Mayo Clinic, Rochester, Minnesota.,Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, Minnesota.,Department of Radiology, Vascular and Interventional Radiology, Mayo Clinic Rochester, Minnesota
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8
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Katz MG, Fargnoli AS, Gubara SM, Chepurko E, Bridges CR, Hajjar RJ. Surgical and physiological challenges in the development of left and right heart failure in rat models. Heart Fail Rev 2019; 24:759-777. [PMID: 30903356 PMCID: PMC6698228 DOI: 10.1007/s10741-019-09783-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Rodent surgical animal models of heart failure (HF) are critically important for understanding the proof of principle of the cellular alterations underlying the development of the disease as well as evaluating therapeutics. Robust, reproducible rodent models are a prerequisite to the development of pharmacological and molecular strategies for the treatment of HF in patients. Due to the absence of standardized guidelines regarding surgical technique and clear criteria for HF progression in rats, objectivity is compromised. Scientific publications in rats rarely fully disclose the actual surgical details, and technical and physiological challenges. This lack of reporting is one of the main reasons that the outcomes specified in similar studies are highly variable and associated with unnecessary loss of animals, compromising scientific assessment. This review details rat circulatory and coronary arteries anatomy, the surgical details of rat models that recreate the HF phenotype of myocardial infarction, ischemia/reperfusion, left and right ventricular pressure, and volume overload states, and summarizes the technical and physiological challenges of creating HF. The purpose of this article is to help investigators understand the underlying issues of current HF models in order to reduce variable results and ensure successful, reproducible models of HF.
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Affiliation(s)
- Michael G Katz
- Cardiovascular Research Center, Department of Cardiology, Icahn School of Medicine at Mount Sinai, 1470 Madison Ave., Box 1030, New York, NY, 10029-6574, USA.
| | - Anthony S Fargnoli
- Cardiovascular Research Center, Department of Cardiology, Icahn School of Medicine at Mount Sinai, 1470 Madison Ave., Box 1030, New York, NY, 10029-6574, USA
| | - Sarah M Gubara
- Cardiovascular Research Center, Department of Cardiology, Icahn School of Medicine at Mount Sinai, 1470 Madison Ave., Box 1030, New York, NY, 10029-6574, USA
| | - Elena Chepurko
- Cardiovascular Research Center, Department of Cardiology, Icahn School of Medicine at Mount Sinai, 1470 Madison Ave., Box 1030, New York, NY, 10029-6574, USA
| | - Charles R Bridges
- Cardiovascular Research Center, Department of Cardiology, Icahn School of Medicine at Mount Sinai, 1470 Madison Ave., Box 1030, New York, NY, 10029-6574, USA
| | - Roger J Hajjar
- Cardiovascular Research Center, Department of Cardiology, Icahn School of Medicine at Mount Sinai, 1470 Madison Ave., Box 1030, New York, NY, 10029-6574, USA
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9
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Abstract
Objective: Invasive coronary interventions can fail due to intimal hyperplasia and restenosis.
Endothelial cell (EC) seeding to the vessel lumen, accelerating re-endothelialization,
or local release of mTOR pathway inhibitors have helped reduce intimal hyperplasia after
vessel injury. While animal models are powerful tools, they are complex and expensive,
and not always reflective of human physiology. Therefore, we developed an in
vitro 3D vascular model validating previous in vivo animal
models and utilizing isolated human arteries to study vascular remodeling after injury.
Approach: We utilized a bioreactor that enables the control of intramural
pressure and shear stress in vessel conduits to investigate the vascular response in
both rat and human arteries to intraluminal injury. Results: Culturing rat aorta segments in vitro, we show that vigorous removal
of luminal ECs results in vessel injury, causing medial proliferation by Day-4 and
neointima formation, with the observation of SCA1+ cells (stem cell
antigen-1) in the intima by Day-7, in the absence of flow. Conversely, when
endothelial-denuded rat aortae and human umbilical arteries were subjected to arterial
shear stress, pre-seeding with human umbilical ECs decreased the number and
proliferation of smooth muscle cell (SMC) significantly in the media of both rat and
human vessels. Conclusion: Our bioreactor system provides a novel platform for correlating ex
vivo findings with vascular outcomes in vivo. The present
in vitro human arterial injury model can be helpful in the study of
EC-SMC interactions and vascular remodeling, by allowing for the separation of
mechanical, cellular, and soluble factors.
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Affiliation(s)
- Mehmet H Kural
- 1 Vascular Biology and Therapeutics Program, Yale University School of Medicine, New Haven, CT, USA.,2 Department of Anesthesiology, Yale University, New Haven, CT, USA
| | - Guohao Dai
- 3 Department of Bioengineering, Northeastern University, Boston, MA, USA
| | - Laura E Niklason
- 1 Vascular Biology and Therapeutics Program, Yale University School of Medicine, New Haven, CT, USA.,2 Department of Anesthesiology, Yale University, New Haven, CT, USA.,4 Department of Biomedical Engineering, Yale University, New Haven, CT, USA
| | - Liqiong Gui
- 1 Vascular Biology and Therapeutics Program, Yale University School of Medicine, New Haven, CT, USA.,2 Department of Anesthesiology, Yale University, New Haven, CT, USA
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10
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Garbey M, Casarin S, Berceli SA. A versatile hybrid agent-based, particle and partial differential equations method to analyze vascular adaptation. Biomech Model Mechanobiol 2018; 18:29-44. [PMID: 30094656 PMCID: PMC6373284 DOI: 10.1007/s10237-018-1065-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2018] [Accepted: 07/26/2018] [Indexed: 11/27/2022]
Abstract
Peripheral arterial occlusive disease is a chronic pathology affecting at least 8–12 million people in the USA, typically treated with a vein graft bypass or through the deployment of a stent in order to restore the physiological circulation. Failure of peripheral endovascular interventions occurs at the intersection of vascular biology, biomechanics, and clinical decision making. It is our hypothesis that the majority of endovascular treatment approaches share the same driving mechanisms and that a deep understanding of the adaptation process is pivotal in order to improve the current outcome of the procedure. The postsurgical adaptation of vein graft bypasses offers the perfect example of how the balance between intimal hyperplasia and wall remodeling determines the failure or the success of the intervention. Accordingly, this work presents a versatile computational model able to capture the feedback loop that describes the interaction between events at cellular/tissue level and mechano-environmental conditions. The work here presented is a generalization and an improvement of a previous work by our group of investigators, where an agent-based model uses a cellular automata principle on a fixed hexagonal grid to reproduce the leading events of the graft’s restenosis. The new hybrid model here presented allows a more realistic simulation both of the biological laws that drive the cellular behavior and of the active role of the membranes that separate the various layers of the vein. The novel feature is to use an immersed boundary implementation of a highly viscous flow to represent SMC motility and matrix reorganization in response to graft adaptation. Our implementation is modular, and this makes us able to choose the right compromise between closeness to the physiological reality and complexity of the model. The focus of this paper is to offer a new modular implementation that combines the best features of an agent-based model, continuum mechanics, and particle-tracking methods to cope with the multiscale nature of the adaptation phenomena. This hybrid method allows us to quickly test various hypotheses with a particular attention to cellular motility, a process that we demonstrated should be driven by mechanical homeostasis in order to maintain the right balance between cells and extracellular matrix in order to reproduce a distribution similar to histological experimental data from vein grafts.
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Affiliation(s)
- Marc Garbey
- Houston Methodist Research Institute, Houston, TX, USA. .,Department of Surgery, Houston Methodist Hospital, Houston, TX, USA. .,LaSIE, UMR CNRS 7356, University of la Rochelle, La Rochelle, France.
| | - Stefano Casarin
- Houston Methodist Research Institute, Houston, TX, USA.,LaSIE, UMR CNRS 7356, University of la Rochelle, La Rochelle, France
| | - Scott A Berceli
- Department of Surgery, University of Florida, Gainesville, FL, USA.,Malcom Randall VAMC, Gainesville, FL, USA
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11
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Vatankhah E, Prabhakaran MP, Ramakrishna S. Biomimetic microenvironment complexity to redress the balance between biodegradation and de novo matrix synthesis during early phase of vascular tissue engineering. MATERIALS SCIENCE & ENGINEERING. C, MATERIALS FOR BIOLOGICAL APPLICATIONS 2017; 81:39-47. [DOI: 10.1016/j.msec.2017.06.021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2017] [Revised: 05/29/2017] [Accepted: 06/28/2017] [Indexed: 01/12/2023]
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12
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Lin PH, Bush RL, Nguyen L, Guerrero MA, Chen C, Lumsden AB. Anastomotic Strategies to Improve Hemodialysis Access Patency—A Review. Vasc Endovascular Surg 2016; 39:135-42. [PMID: 15806274 DOI: 10.1177/153857440503900202] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The number of patients with end-stage renal disease (ESRD) who require maintenance hemodialysis has risen sharply in the past 2 decades. It is estimated that more than 60% of all patients with ESRD who require chronic hemodialysis are accessed through an arteriovenous fistula (AVF) or graft (AVG), and the incidence is increasing at a rate of 2% to 4% per year. The long-term patency rate of an upper extremity AVF or AVG for hemodialysis access remains suboptimal owing in part to progressive stenosis at the venous anastomosis. This article reviews the causative factors of dialysis access-related anastomotic stenosis, or intimal hyperplasia. This article also reviews the clinical experience of various anastomotic strategies to ameliorate the hemodynamic environment in an effort to improve the clinical outcome of hemodialysis access. These strategies include the use of (1) vein cuff at the expanded polytetrafluoroethylene (ePTFE)-venous anastomosis of AVG, (2) cuffed ePTFE dialysis AVG, and (3) anastomotic devices that create an interrupted anastomosis with staples or clips.
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Affiliation(s)
- Peter H Lin
- Division of Vascular Surgery and Endovascular Therapy, Michael E. DeBakey Department of Surgery, Baylor College of Medicine, Houston VAMC (112), 2002 Holcomb Blvd, Houston, TX 77030, USA.
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13
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Yamamoto K, Protack CD, Kuwahara G, Tsuneki M, Hashimoto T, Hall MR, Assi R, Brownson KE, Foster TR, Bai H, Wang M, Madri JA, Dardik A. Disturbed shear stress reduces Klf2 expression in arterial-venous fistulae in vivo. Physiol Rep 2015; 3:3/3/e12348. [PMID: 25780089 PMCID: PMC4393175 DOI: 10.14814/phy2.12348] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Laminar shear stress (SS) induces an antiproliferative and anti-inflammatory endothelial phenotype and increases Klf2 expression. We altered the diameter of an arteriovenous fistula (AVF) in the mouse model to determine whether increased fistula diameter produces disturbed SS in vivo and if acutely increased disturbed SS results in decreased Klf2 expression. The mouse aortocaval fistula model was performed with 22, 25, or 28 gauge needles to puncture the aorta and the inferior vena cava. Duplex ultrasound was used to examine the AVF and its arterial inflow and venous outflow, and SS was calculated. Arterial samples were examined with western blot, immunohistochemistry, and immunofluorescence analysis for proteins and qPCR for RNA. Mice with larger diameter fistulae had diminished survival but increased AVF patency. Increased SS magnitudes and range of frequencies were directly proportional to the needle diameter in the arterial limb proximal to the fistula but not in the venous limb distal to the fistula, with 22-gauge needles producing the most disturbed SS in vivo. Klf2 mRNA and protein expression was diminished in the artery proximal to the fistula in proportion to increasing SS. Increased fistula diameter produces increased SS magnitude and frequency, consistent with disturbed SS in vivo. Disturbed SS is associated with decreased mRNA and protein expression of Klf2. Disturbed SS and reduced Klf2 expression near the fistula are potential therapeutic targets to improve AVF maturation.
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Affiliation(s)
- Kota Yamamoto
- Veterans Affairs Connecticut Healthcare Systems, West Haven, Connecticut Vascular Biology & Therapeutics Program, Yale University School of Medicine, New Haven, Connecticut Department of Surgery, Yale University School of Medicine, New Haven, Connecticut Division of Vascular Surgery, Department of Surgery, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | - Clinton D Protack
- Vascular Biology & Therapeutics Program, Yale University School of Medicine, New Haven, Connecticut Department of Surgery, Yale University School of Medicine, New Haven, Connecticut
| | - Go Kuwahara
- Vascular Biology & Therapeutics Program, Yale University School of Medicine, New Haven, Connecticut Department of Surgery, Yale University School of Medicine, New Haven, Connecticut
| | - Masayuki Tsuneki
- Vascular Biology & Therapeutics Program, Yale University School of Medicine, New Haven, Connecticut Department of Pathology, Yale University School of Medicine, New Haven, Connecticut Division of Cancer Biology, National Cancer Center Research Institute, Tokyo, Japan
| | - Takuya Hashimoto
- Vascular Biology & Therapeutics Program, Yale University School of Medicine, New Haven, Connecticut Department of Surgery, Yale University School of Medicine, New Haven, Connecticut Division of Vascular Surgery, Department of Surgery, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | - Michael R Hall
- Vascular Biology & Therapeutics Program, Yale University School of Medicine, New Haven, Connecticut Department of Surgery, Yale University School of Medicine, New Haven, Connecticut
| | - Roland Assi
- Vascular Biology & Therapeutics Program, Yale University School of Medicine, New Haven, Connecticut Department of Surgery, Yale University School of Medicine, New Haven, Connecticut
| | - Kirstyn E Brownson
- Vascular Biology & Therapeutics Program, Yale University School of Medicine, New Haven, Connecticut Department of Surgery, Yale University School of Medicine, New Haven, Connecticut
| | - Trenton R Foster
- Vascular Biology & Therapeutics Program, Yale University School of Medicine, New Haven, Connecticut Department of Surgery, Yale University School of Medicine, New Haven, Connecticut
| | - Hualong Bai
- Vascular Biology & Therapeutics Program, Yale University School of Medicine, New Haven, Connecticut Department of Surgery, Yale University School of Medicine, New Haven, Connecticut
| | - Mo Wang
- Vascular Biology & Therapeutics Program, Yale University School of Medicine, New Haven, Connecticut Department of Surgery, Yale University School of Medicine, New Haven, Connecticut
| | - Joseph A Madri
- Vascular Biology & Therapeutics Program, Yale University School of Medicine, New Haven, Connecticut Department of Pathology, Yale University School of Medicine, New Haven, Connecticut
| | - Alan Dardik
- Veterans Affairs Connecticut Healthcare Systems, West Haven, Connecticut Vascular Biology & Therapeutics Program, Yale University School of Medicine, New Haven, Connecticut Department of Surgery, Yale University School of Medicine, New Haven, Connecticut
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14
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Novel modular anastomotic valve device for hemodialysis vascular access: preliminary computational hemodynamic assessment. J Vasc Access 2014; 15:448-60. [PMID: 25198822 DOI: 10.5301/jva.5000284] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/13/2014] [Indexed: 11/20/2022] Open
Abstract
PURPOSE Arteriovenous graft patency is limited by terminal occlusion caused by intimal hyperplasia (IH). Motivated by evidence that flow disturbances promote IH progression, a modular anastomotic valve device (MAVD) was designed to isolate the graft from the circulation between dialysis periods (closed position) and enable vascular access during dialysis (open position). The objective of this study was to perform a preliminary computational assessment of the device ability to normalize venous flow between dialysis periods and potentially limit IH development and thrombogenesis. METHODS Computational fluid dynamics simulations were performed to compare flow and wall shear stress (WSS) in a native vein and MAVD prototypes featuring anastomotic angles of 90° and 30°. Low WSS (LWSS) regions prone to IH development were characterized in terms of temporal shear magnitude (TSM), oscillatory shear index (OSI), and relative residence time (RRT). Thrombogenic potential was assessed by investigating the loading history of fluid particles traveling through the device. RESULTS The closed MAVD exhibited the same flow characteristics as the native vein (0.3% difference in pressure drop, 3.5% difference in surface-averaged WSS). The open MAVD generated five LWSS regions (TSM <0.5 Pa) exhibiting different degrees of flow reversal (surface-averaged OSI: 0.03-0.36) and stagnation (max RRT: 2.50-37.16). Reduction in anastomotic angle resulted in the suppression of three LWSS regions and overall reductions in flow reversal (surface-averaged OSI <0.21) and stagnation (max RRT <18.05). CONCLUSIONS This study suggests the ability of the MAVD to normalize venous flow between dialysis periods while generating the typical hemodynamics of end-to-side vein-graft anastomoses during dialysis.
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15
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Mitogenesis of vascular smooth muscle cell stimulated by platelet-derived growth factor-bb is inhibited by blocking of intracellular signaling by epigallocatechin-3-O-gallate. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2013; 2013:827905. [PMID: 24307927 PMCID: PMC3836374 DOI: 10.1155/2013/827905] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/19/2013] [Revised: 08/19/2013] [Accepted: 09/09/2013] [Indexed: 01/04/2023]
Abstract
Epigallocatechin gallate (EGCG) is known to exhibit antioxidant, antiproliferative, and antithrombogenic effects and reduce the risk of cardiovascular diseases. Key events in the development of cardiovascular disease are hypertrophy and hyperplasia according to vascular smooth muscle cell proliferation. In this study, we investigated whether EGCG can interfere with PDGF-bb stimulated proliferation, cell cycle distribution, and the gelatinolytic activity of MMP and signal transduction pathways on RAOSMC when it was treated in two different ways-cotreatment with PDGF-bb and pretreatment of EGCG before addition of PDGF-bb. Both cotreated and pretreated EGCG significantly inhibited PDGF-bb induced proliferation, cell cycle progression of the G0/G1 phase, and the gelatinolytic activity of MMP-2/9 on RAOSMC. Also, EGCG blocked PDGF receptor-β (PDGFR-β) phosphorylation on PDGF-bb stimulated RAOSMC under pretreatment with cells as well as cotreatment with PDGF-bb. The downstream signal transduction pathways of PDGFR-β, including p42/44 MAPK, p38 MAPK, and Akt phosphorylation, were also inhibited by EGCG in a pattern similar to PDGFR-β phosphorylation. These findings suggest that EGCG can inhibit PDGF-bb stimulated mitogenesis by indirectly and directly interrupting PDGF-bb signals and blocking the signaling pathway via PDGFR-β phosphorylation. Furthermore, EGCG may be used for treatment and prevention of cardiovascular disease through blocking of PDGF-bb signaling.
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16
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Yamamoto K, Protack CD, Tsuneki M, Hall MR, Wong DJ, Lu DY, Assi R, Williams WT, Sadaghianloo N, Bai H, Miyata T, Madri JA, Dardik A. The mouse aortocaval fistula recapitulates human arteriovenous fistula maturation. Am J Physiol Heart Circ Physiol 2013; 305:H1718-25. [PMID: 24097429 DOI: 10.1152/ajpheart.00590.2013] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Several models of arteriovenous fistula (AVF) have excellent patency and help in understanding the mechanisms of venous adaptation to the arterial environment. However, these models fail to exhibit either maturation failure or fail to develop stenoses, both of which are critical modes of AVF failure in human patients. We used high-resolution Doppler ultrasound to serially follow mice with AVFs created by direct 25-gauge needle puncture. By day 21, 75% of AVFs dilate, thicken, and increase flow, i.e., mature, and 25% fail due to immediate thrombosis or maturation failure. Mature AVF thicken due to increased amounts of smooth muscle cells. By day 42, 67% of mature AVFs remain patent, but 33% of AVFs fail due to perianastomotic thickening. These results show that the mouse aortocaval model has an easily detectable maturation phase in the first 21 days followed by a potential failure phase in the subsequent 21 days. This model is the first animal model of AVF to show a course that recapitulates aspects of human AVF maturation.
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Affiliation(s)
- Kota Yamamoto
- Veterans Affairs Connecticut Healthcare Systems, West Haven, Connecticut
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17
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Hwang M, Garbey M, Berceli SA, Wu R, Jiang Z, Tran-Son-Tay R. Rule-based model of vein graft remodeling. PLoS One 2013; 8:e57822. [PMID: 23533576 PMCID: PMC3606352 DOI: 10.1371/journal.pone.0057822] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2012] [Accepted: 01/26/2013] [Indexed: 11/18/2022] Open
Abstract
When vein segments are implanted into the arterial system for use in arterial bypass grafting, adaptation to the higher pressure and flow of the arterial system is accomplished thorough wall thickening and expansion. These early remodeling events have been found to be closely coupled to the local hemodynamic forces, such as shear stress and wall tension, and are believed to be the foundation for later vein graft failure. To further our mechanistic understanding of the cellular and extracellular interactions that lead to global changes in tissue architecture, a rule-based modeling method is developed through the application of basic rules of behaviors for these molecular and cellular activities. In the current method, smooth muscle cell (SMC), extracellular matrix (ECM), and monocytes are selected as the three components that occupy the elements of a grid system that comprise the developing vein graft intima. The probabilities of the cellular behaviors are developed based on data extracted from in vivo experiments. At each time step, the various probabilities are computed and applied to the SMC and ECM elements to determine their next physical state and behavior. One- and two-dimensional models are developed to test and validate the computational approach. The importance of monocyte infiltration, and the associated effect in augmenting extracellular matrix deposition, was evaluated and found to be an important component in model development. Final model validation is performed using an independent set of experiments, where model predictions of intimal growth are evaluated against experimental data obtained from the complex geometry and shear stress patterns offered by a mid-graft focal stenosis, where simulation results show good agreements with the experimental data.
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Affiliation(s)
- Minki Hwang
- Departments of Mechanical & Aerospace Engineering, University of Florida, Gainesville, Florida, United States of America
| | - Marc Garbey
- Department of Computer Science, University of Houston, Houston, Texas, United States of America
| | - Scott A. Berceli
- Department of Surgery, University of Florida College of Medicine, Gainesville, Florida, United States of America
- Malcom Randall Veterans Affairs Medical Center, Gainesville, Florida, United States of America
| | - Rongling Wu
- Center for Statistical Genetics, Division of Biostatistics, Pennsylvania State University, Hershey, Pennsylvania, United States of America
| | - Zhihua Jiang
- Department of Surgery, University of Florida College of Medicine, Gainesville, Florida, United States of America
- Malcom Randall Veterans Affairs Medical Center, Gainesville, Florida, United States of America
| | - Roger Tran-Son-Tay
- Departments of Mechanical & Aerospace Engineering, University of Florida, Gainesville, Florida, United States of America
- * E-mail:
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18
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Involvement of large conductance Ca2+-activated K+ channel in laminar shear stress-induced inhibition of vascular smooth muscle cell proliferation. Pflugers Arch 2012. [DOI: 10.1007/s00424-012-1182-z] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
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19
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Hsu S, Chu JS, Chen FF, Wang A, Li S. Effects of Fluid Shear Stress on a Distinct Population of Vascular Smooth Muscle Cells. Cell Mol Bioeng 2011; 4:627-636. [PMID: 22924082 DOI: 10.1007/s12195-011-0205-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
Vascular smooth muscle cells (SMCs) are a major cell type involved in vascular remodeling. The various developmental origins of SMCs such as neural crest and mesoderm result in heterogeneity of SMCs, which plays an important role in the development of vascular remodeling and diseases. Upon vascular injury, SMCs are exposed to blood flow and subjected to fluid shear stress. Previous studies have shown that fluid shear stress inhibits SMC proliferation. However, the effect of shear stress on the subpopulation of SMCs from specific developmental origin and vascular bed is not well understood. Here we investigated how shear stress regulates human aortic SMCs positive for neural crest markers. DNA microarray analysis showed that shear stress modulates the expression of genes involved in cell proliferation, matrix synthesis, cell signaling, transcription and cytoskeleton organization. Further studies demonstrated that shear stress induced SMC proliferation and cyclin D1, downregulated cell cycle inhibitor p21, and activated Akt pathway. Inhibition of PI-3 kinase blocked these shear stress-induced changes. These results suggest that SMCs with neural crest characteristics may respond to shear stress in a different manner. This finding has significant implications in the remodeling and diseases of blood vessels.
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Affiliation(s)
- Steven Hsu
- Department of Bioengineering, University of California, Berkeley, Berkeley, CA, USA
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20
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Hsiao JF, Chou HH, Hsu LA, Wu LS, Yang CW, Hsu TS, Chang CJ. Vascular changes at the puncture segments of arteriovenous fistula for hemodialysis access. J Vasc Surg 2010; 52:669-73. [DOI: 10.1016/j.jvs.2010.03.032] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2010] [Revised: 03/17/2010] [Accepted: 03/20/2010] [Indexed: 11/26/2022]
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21
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Kanjickal D, Lopina S, Evancho-Chapman MM, Schmidt S, Donovan D. Sustained local drug delivery from a novel polymeric ring to inhibit intimal hyperplasia. J Biomed Mater Res A 2010; 93:656-65. [PMID: 19610053 DOI: 10.1002/jbm.a.32307] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The long-term clinical success of autologous vein and synthetic vascular grafts are limited because of the development of anastomotic intimal hyperplasia (IH). We have previously published data suggesting that cyclosporine (CyA) may reduce the development of IH in a canine model (Hirko et al., J Vasc Surg 1993;17:877-887). However, systemic administration of CyA could create serious adverse effects. Therefore, it is our long-term goal to test the hypothesis that the controlled local release of CyA from a polymeric vascular wrap would prevent the development of IH. To test this hypothesis, we developed a controlled release polymeric ring that could be placed around anastomotic sites to deliver therapeutic drugs locally. The ring is a composite polymeric device consisting of poly(DL-lactide-co-glycolide) (PLGA) microspheres embedded in a poly(ethylene glycol) hydrogel. Several in vitro studies were conducted to evaluate the effects of different sterilization procedures on the properties of the device. It was determined that gamma sterilization was the preferred sterilization method of choice for this device. In vivo studies were conducted on a swine model to evaluate the biocompatibility of the ring. The histological findings of the ring implants at 2 and 4 weeks demonstrate the biocompatibility of this device.
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Affiliation(s)
- Deenu Kanjickal
- Department of Chemical Engineering, University of Akron, Akron, Ohio 44325, USA
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22
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Computational study of pulsatile blood flow in prototype vessel geometries of coronary segments. Phys Med 2010; 26:140-56. [PMID: 20400349 DOI: 10.1016/j.ejmp.2009.03.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/25/2008] [Revised: 01/26/2009] [Accepted: 03/17/2009] [Indexed: 02/02/2023] Open
Abstract
The spatial and temporal distributions of wall shear stress (WSS) in prototype vessel geometries of coronary segments are investigated via numerical simulation, and the potential association with vascular disease and specifically atherosclerosis and plaque rupture is discussed. In particular, simulation results of WSS spatio-temporal distributions are presented for pulsatile, non-Newtonian blood flow conditions for: (a) curved pipes with different curvatures, and (b) bifurcating pipes with different branching angles and flow division. The effects of non-Newtonian flow on WSS (compared to Newtonian flow) are found to be small at Reynolds numbers representative of blood flow in coronary arteries. Specific preferential sites of average low WSS (and likely atherogenesis) were found at the outer regions of the bifurcating branches just after the bifurcation, and at the outer-entry and inner-exit flow regions of the curved vessel segment. The drop in WSS was more dramatic at the bifurcating vessel sites (less than 5% of the pre-bifurcation value). These sites were also near rapid gradients of WSS changes in space and time - a fact that increases the risk of rupture of plaque likely to develop at these sites. The time variation of the WSS spatial distributions was very rapid around the start and end of the systolic phase of the cardiac cycle, when strong fluctuations of intravascular pressure were also observed. These rapid and strong changes of WSS and pressure coincide temporally with the greatest flexion and mechanical stresses induced in the vessel wall by myocardial motion (ventricular contraction). The combination of these factors may increase the risk of plaque rupture and thrombus formation at these sites.
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23
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Owens CD. Adaptive changes in autogenous vein grafts for arterial reconstruction: clinical implications. J Vasc Surg 2009; 51:736-46. [PMID: 19837532 DOI: 10.1016/j.jvs.2009.07.102] [Citation(s) in RCA: 111] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2009] [Revised: 07/20/2009] [Accepted: 07/24/2009] [Indexed: 01/22/2023]
Abstract
For patients with the most severe manifestations of lower extremity arterial occlusive disease, bypass surgery using autogenous vein has been the most durable reconstruction. However, the incidence of bypass graft stenosis and graft failure remains substantial and wholesale improvements in patency are lacking. One potential explanation is that stenosis arises not only from over exuberant intimal hyperplasia, but also due to insufficient adaptation or remodeling of the vein to the arterial environment. Although in vivo human studies are difficult to conduct, recent advances in imaging technology have made possible a more comprehensive structural examination of vein bypass maturation. This review summarizes recent translational efforts to understand the structural and functional properties of human vein grafts and places it within the context of the rich existing literature of vein graft failure.
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Affiliation(s)
- Christopher D Owens
- Division of Vascular and Endovascular Surgery, University of California San Francisco, San Francisco, CA 94143, USA.
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24
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Pantos I, Patatoukas G, Efstathopoulos EP, Katritsis D. In vivo wall shear stress measurements using phase-contrast MRI. Expert Rev Cardiovasc Ther 2008; 5:927-38. [PMID: 17867922 DOI: 10.1586/14779072.5.5.927] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
There is growing evidence to suggest that endothelial biology and atherosclerosis depend on arterial wall shear stress (WSS). We review the existing literature on in vivo measurements of WSS in healthy individuals using phase-contrast MRI, which is a promising, noninvasive technique for determining various blood flow characteristics. WSS data exist for the following arteries: carotid, brachial, aorta and femoral. Measured values indicate that WSS is site specific, a finding which opposes the notion that physiological WSS values are maintained at a constant magnitude in all parts of the arterial system. Among the WSS values obtained at the same site by different investigators there is qualitative agreement; however, differences exist in absolute values mainly due to the dependence on the method used to obtain WSS values from velocity data.
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Affiliation(s)
- Ioannis Pantos
- Athens Euroclinic, Department of Cardiology, 9 Athanassiadou St, Athens 11521, Greece.
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25
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Xiong FL, Chong CK. A parametric numerical investigation on haemodynamics in distal coronary anastomoses. Med Eng Phys 2008; 30:311-20. [PMID: 17616426 DOI: 10.1016/j.medengphy.2007.04.013] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2006] [Revised: 01/23/2007] [Accepted: 04/19/2007] [Indexed: 11/20/2022]
Abstract
Anastomotic haemodynamics, which plays an important role in the performance of bypass graft, is known to be profoundly affected by the diameter ratio (Phi) and angle (alpha) between the graft and host artery in the peripheral region. We hypothesize that these geometric factors would play similar roles in distal coronary anastomoses and that they could be improved for clinical applications through parametric studies. Anastomotic models covering a range of Phi (1:1, 1.5:1 and 2:1) and alpha (15 degrees , 30 degrees , 45 degrees and 60 degrees ) were investigated numerically in physiological coronary flow conditions. The transient flow patterns, cycle-averaged wall shear stress (WSS), oscillatory shear index (OSI), spatial and temporal WSS gradients (SWSSG and TWSSG) were compared. Results show a stronger influence of Phi than alpha on haemodynamics in distal coronary artery anastomoses. Substantially higher SWSSG and TSSWG occur on the artery floor when Phi=1:1 compared to larger Phi. High levels of OSI occur in critical regions when Phi=1:1 and 2:1. The largest area of high OSI is found in the anastomotic region when alpha=15 degrees , whereas the highest level of SWSSG appears on the artery floor when alpha=60 degrees . The study suggests the clinical relevance of optimizing geometric parameters of coronary anastomoses to improve their haemodynamic performance. We speculate that for a distal coronary anastomosis with a 20:80 proximal-distal flow division ratio maintained in the host artery, Phi=1.5 and alpha=30-45 degrees would enhance its long-term performance.
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Affiliation(s)
- F L Xiong
- School of Mechanical and Aerospace Engineering, Nanyang Technological University, 62 Nanyang Drive, Singapore
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26
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Effect of external stents on prevention of intimal hyperplasia in a canine vein graft model. Chin Med J (Engl) 2007. [DOI: 10.1097/00029330-200712020-00021] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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27
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Abstract
Atherosclerosis is a systemic, multifocal disease leading to a various symptoms and clinical events. Beyond disparities related to the organs involved, some differences might exist according to whether the lesions occur in the large (proximal) or small (distal) arteries. Atherosclerotic lesions occur predominantly in the large vessels first, and more distal lesions occur with aging. Proximal lesions are usually more evolving, especially with higher rates of unstable plaques in the proximal segments of coronary arteries. Racial differences regarding lesion distribution exist, with higher rates of distal lesions observed in races other than caucaians. Despite conflicting results found in each vascular territory, there is a suggestion of a stronger association between large vessel disease and smoking and dyslipidemia, whereas diabetes appears more specific for small vessel disease. Hypertension is more frequently reported in intracranial than in extracranial cerebrovascular disease. Preliminary studies report inflammatory markers preferably associated to large-vessel atherosclerosis. Proximal lesions in 1 territory are more frequently associated with concomitant lesions in other territories. Geometric, hemodynamic, and histologic particularities in large and small vessels may at least partially explain these differences, and some recent data point out different biologic properties of the endothelium according to its location.
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Affiliation(s)
- Victor Aboyans
- Department of Thoracic and Cardiovascular Surgery and Angiology, Dupuytren University Hospital, Limoges, France.
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28
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Dajnowiec D, Langille BL. Arterial adaptations to chronic changes in haemodynamic function: coupling vasomotor tone to structural remodelling. Clin Sci (Lond) 2007; 113:15-23. [PMID: 17536999 DOI: 10.1042/cs20060337] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Healthy mature arteries are usually extremely quiescent tissues with cell proliferation rates much below 1%/day and with extracellular matrix constituents exhibiting half-lives of years to decades. However, chronic physiological or pathological changes in haemodynamic function elicit arterial remodelling processes that may involve substantial tissue synthesis, degradation or turnover. Although these remodelling processes accommodate changing demands placed upon the cardiovascular system by physiological adaptations, they can compromise further perfusion in the context of arterial occlusive disease and they entrench hypertension and may exacerbate its progression. Recent findings indicate that some of the most important such remodelling responses involve the integrated effects of persistently altered vascular tone that feed into restructuring responses, with common signalling pathways frequently interacting in the control of both phases of the response. Current efforts to define these signals and their targets may provide new directions for therapeutic interventions to treat important vascular disorders.
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Affiliation(s)
- Dorota Dajnowiec
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada
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29
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Zhang HS, Wang SQ. Notoginsenoside R1 inhibits TNF-alpha-induced fibronectin production in smooth muscle cells via the ROS/ERK pathway. Free Radic Biol Med 2006; 40:1664-74. [PMID: 16632126 DOI: 10.1016/j.freeradbiomed.2006.01.003] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/12/2005] [Revised: 12/23/2005] [Accepted: 01/03/2006] [Indexed: 11/21/2022]
Abstract
The matrix fibronectin protein plays an important role in vascular remodeling. Notoginsenoside R1 is the main ingredient with cardiovascular activity in Panax notoginseng; however, its molecular mechanisms are poorly understood. We report that notoginsenoside R1 significantly decreased TNF-alpha-induced activation of fibronectin mRNA, protein levels, and secretion in human arterial smooth muscle cells (HASMCs) in a dose-dependent manner. Notoginsenoside R1 scavenged hydrogen peroxide (H2O2) in a dose-dependent manner in the test tube. TNF-alpha significantly increased intracellular ROS generation and then ERK activation, which was blocked by notoginsenoside R1 or DPI and apocynin, inhibitors of NADPH oxidase, or the antioxidant NAC. Our data demonstrated that TNF-alpha-induced upregulation of fibronectin mRNA and protein levels occurs via activation of ROS/ERK, which was prevented by treatment with notoginsenoside R1, DPI, apocynin, NAC, or MAPK/ERK inhibitors PD098059 and U0126. Notoginsenoside R1 significantly inhibited H2O2-induced upregulation of fibronectin mRNA and protein levels and secretion; it also significantly inhibited TNF-alpha and H2O2-induced migration. These results suggest that notoginsenoside R1 inhibits TNF-alpha-induced ERK activation and subsequent fibronectin overexpression and migration in HASMCs by suppressing NADPH oxidase-mediated ROS generation and directly scavenging ROS.
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Affiliation(s)
- Hong-Sheng Zhang
- Department of Biotechnology, Beijing Institute of Radiation Medicine, Taiping Road 27#, Beijing 100850, People's Republic of China
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30
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Pfeiffer T, Wallich M, Sandmann W, Schrader J, Gödecke A. Lipoplex gene transfer of inducible nitric oxide synthase inhibits the reactive intimal hyperplasia after expanded polytetrafluoroethylene bypass grafting. J Vasc Surg 2006; 43:1021-7. [PMID: 16678699 DOI: 10.1016/j.jvs.2006.01.014] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2005] [Accepted: 01/05/2006] [Indexed: 10/24/2022]
Abstract
OBJECTIVE Intimal hyperplasia (IH) is most commonly the cause of graft occlusion in infrainguinal bypass grafting for arterial occlusive disease. We investigated the influence of nitric oxide on the IH of the arterial vessel wall at the region of prosthetic bypass anastomoses. METHODS Experiments were performed in 10 Foxhound dogs. We used a technique of inducible nitric oxide synthase (iNOS) overexpression by a non-virus-mediated, liposome-based iNOS gene transfer. The plasmid pSCMV-iNOS, which drives the expression of iNOS under control of the cytomegalovirus promoter, was complexed with cationic liposomes (lipoplexes). Segments of both carotid arteries were pretreated by intramural injection of a lipoplex solution by using an infiltrator balloon catheter (Infiltrator Drug Delivery Balloon System). In each dog, iNOS was administered at one side, and a control vector (pSCMV2) was administered at the contralateral side. Carotid arteries were ligated, and bypass grafts (expanded polytetrafluoroethylene, 6-mm, ring enforced) were implanted on both sides. The proximal and distal anastomoses (end-to-side fashion; running nonabsorbable sutures) were placed in the pretreated regions. After 6 months, the prostheses were excised, and the intimal thicknesses of 50 cross sections (orcein staining) of each anastomosis were measured planimetrically. RESULTS The average reduction of the neointima thickness of the iNOS side in proximal anastomoses at the prosthetic wall, suture region, and arterial wall was 43%, 52%, and 81%, respectively. In distal anastomoses, the average reduction was 40%, 47%, and 52%, respectively. All differences of neointima thickness between the iNOS and control sides were statistically significant (Wilcoxon test; P < or = .05). CONCLUSIONS Inducible NOS expression is an efficient approach for inhibition of IH. In contrast to earlier studies, which investigated the efficacy of gene therapeutic NOS expression at 3 to 4 weeks after intervention, the novelty of our findings is that a single local lipoplex-mediated transfection of the vascular wall with iNOS-expressing plasmids leads to a reduction of IH in a prosthetic in vivo model even after 6 months. Because all components can be manufactured under Good Manufacturing Practice conditions (the quality-management system of the European pharmaceutical industry based on ISO 9000), this approach is also amenable to human therapy.
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Affiliation(s)
- Tomas Pfeiffer
- Department of Vascular Surgery and Kidney Transplantation, University Hospital Medical School, Heinrich-Heine-University Düsseldorf, Germany.
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Li XM, Rittgers SE. Computational simulation of biomechanics in e-PTFE and venous Miller's cuffs: implications for intimal hyperplasia. J Med Eng Technol 2005; 29:187-96. [PMID: 16012071 DOI: 10.1080/03091900412331286387] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
A computational distal end-to-side Miller's cuff anastomotic model was used to analyse the possible difference in intimal hyperplasia (IH) formed between e-PTFE and venous cuffs. A large strain FEA model was used to compute the strain after physiological loading and the deformed geometries used as wall boundaries for CFD analysis. Regression analysis was performed to investigate relationships between mechanical factors and prior IH. The results showed that the venous Miller's cuff anastomosis deformed twice as much as the e-PTFE cuff and that the expansion of both cuffs generated elevated strains in the artery floor while the fluid shear indices were qualitatively similar in each case. In the e-PTFE cuff, the strain and OSI correlated with IH in a proportional and equivalent manner; however, these regressions grossly over-estimated the predicted IH in the vein cuff. Thus, biomechanical effects may be important in synthetically cuffed anastomoses, but do not account for the reduced IH in venous cuffed anastomoses.
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Affiliation(s)
- X-M Li
- Department of Biomedical Engineering, Duke University, Durham, NC, 27708-0281, USA.
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Garanich JS, Pahakis M, Tarbell JM. Shear stress inhibits smooth muscle cell migration via nitric oxide-mediated downregulation of matrix metalloproteinase-2 activity. Am J Physiol Heart Circ Physiol 2005; 288:H2244-52. [PMID: 15637127 DOI: 10.1152/ajpheart.00428.2003] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Vascular smooth muscle cell (SMC) migration is a hallmark of intimal hyperplasia (IH), the progression of which is affected by hemodynamic conditions at the diseased site. The realization that SMCs are exposed to blood flow in both denuded vessels (direct blood flow) and intact vessels (interstitial blood flow) motivated this study of the effects of fluid flow shear stress (SS) on SMC migration. Rat aortic SMCs were seeded onto Matrigel-coated cell culture inserts, and their migratory activity toward PDGF-BB when exposed to SS in a rotating disk apparatus was quantified. Four hours of either 10 or 20 dyn/cm2 SS significantly inhibited SMC migration to the bottom side of the insert. This inhibition was associated with downregulation of SMC matrix metalloproteinase (MMP)-2 activation. Four hours of 10 dyn/cm2 SS also drastically increased SMC production of NO. A NO synthase inhibitor (N(G)-nitro-L-arginine methyl ester; 100 microM) abolished the shear-induced increase in SMC NO production as well as the inhibition of migration and MMP-2 activity. A NO donor (S-nitroso-N-acetyl-penicillamine; 500 microM) suppressed SMC migration via the reduction of both total and active MMP-2 levels. Addition of 10 microM MMP-2 inhibitor I to inserts significantly reduced SMC migration. Western blots showed no effect of 4 h of 20 dyn/cm2 SS on SMC production of PDGF-AA, another chemical known to suppress SMC migration. Thus it appears that SS acts to suppress SMC migration by upregulating the cellular production of NO, which in turn inhibits MMP-2 activity.
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Affiliation(s)
- Jeffrey S Garanich
- Biomolecular Transport Dynamics Laboratory, Department of Bioengineering, Pennsylvania State University, University Park, Pennsylvania, USA
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Abstract
Platelet-derived growth factor (PDGF) was identified in a search for serum factors that stimulate smooth muscle cell (SMC) proliferation. During the development of lesions of atherosclerosis that can ultimately lead to vessel occlusion, SMC are stimulated by inflammatory factors to migrate from their normal location in the media. They accumulate within the forming lesion where they contribute to lesion expansion by proliferation and deposition of extracellular matrix. Different genetic manipulations in vascular cells combined with various inhibitory strategies have provided strong evidence for PDGF playing a prominent role in the migration of SMC into the neointima following acute injury and in atherosclerosis. Other activities of PDGF identified in vivo suggest additional functions for PDGF in the pathogenesis of cardiovascular disease.
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Affiliation(s)
- Elaine W Raines
- Department of Pathology, Harborview Medical Center, University of Washington, Box 359675, 325 9th Avenue, Seattle, WA 98104, USA.
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Allaire E, Muscatelli-Groux B, Guinault AM, Pages C, Goussard A, Mandet C, Bruneval P, Méllière D, Becquemin JP. Vascular smooth muscle cell endovascular therapy stabilizes already developed aneurysms in a model of aortic injury elicited by inflammation and proteolysis. Ann Surg 2004; 239:417-27. [PMID: 15075661 PMCID: PMC1356242 DOI: 10.1097/01.sla.0000114131.79899.82] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVE To investigate the efficiency of endovascular smooth muscle cell (VSMC) seeding in promoting healing and stability in already-developed aneurysms obtained by matrix metalloproteases (MMPs)-driven injury. SUMMARY BACKGROUND DATA VSMCs are instrumental in arterial healing after injury and are in decreased number in arterial aneurysms. This cellular deficiency may account for poor healing capabilities and ongoing expansion of aneurysms. METHODS Aneurysmal aortic xenografts in rats displaying extracellular matrix injury by inflammation and proteolysis were seeded endoluminally with syngeneic VSMCs, with controls receiving culture medium only. Diameter, structure, and the destruction/reconstruction balance were assessed. RESULTS Eight weeks after endovascular infusion, aneurysmal diameter had increased further, from 3.0 +/- 0.3 mm to 10.9 +/- 6.5 mm (P = 0.009), and medial elastin content had decreased from 36.5 +/- 8.5 to 5.2 +/- 5.5 surface-percent (S%; P = 0.009) in controls, whereas these parameters remained stable in the seeded group (3.0 +/- 0.3 to 2.7 +/- 0.2 mm, P = 0.08; 36.5 +/- 8.4 to 31.6 +/- 9.7 S%, P = 0.22). VSMC seeding was followed by a decrease in mononuclear infiltration. MMP-1, -3, -7, -9, and -12 mRNA contents were sharply decreased in the diseased wall in response to seeding. Tissue inhibitor of metalloproteinase-1, -2, and -3 mRNAs in the intima were increased in a 2 to 10 magnitude in comparison with controls. Gelatin zymography showed the disappearance of MMP-9 activity and reverse zymography a strong increase in tissue inhibitor of metalloproteinase-3 activity in the seeded group. VSMC-seeded aneurysms were rich in collagen and lined with an endothelium instead of a thrombus in controls. CONCLUSIONS VSMCs endovascular seeding restores the healing capabilities of proteolytically injured extracellular matrix in aneurysmal aortas, and stops expansion.
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Affiliation(s)
- Eric Allaire
- CNRS UMR 7054, Centre de Recherches Chirurgicales, Université Paris XII, UFR de médecine, Hôpital H. Mondor, AP-HP Créteil, France.
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Fisher RK, How TV, Bakran A, Brennan JA, Harris PL. Outflow distribution at the distal anastomosis of infrainguinal bypass grafts. J Biomech 2004; 37:417-20. [PMID: 14757463 DOI: 10.1016/s0021-9290(03)00262-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Outflow distribution at the distal anastomosis of infrainguinal bypass grafts remains unquantified in vivo, but is likely to influence flow patterns and haemodynamics, thereby impacting upon graft patency. This study measured the ratio of distal to proximal outflow in 30 patients undergoing infrainguinal bypass for lower limb ischaemia, using a flow probe and a transit-time ultrasonic flow meter. The mean outflow distribution was approximately 75% distal to 25% proximal, with above knee anastomoses having a greater proportion of distal flow (84%) compared to below knee grafts (73%). These in vivo flow characteristics differ significantly from those used in theoretical models studying flow phenomena (50:50 and/or 100:0), and should be incorporated into future research.
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Affiliation(s)
- R K Fisher
- Department of Clinical Engineering, Royal Liverpool University Hospital, Duncan Building, Daulby Street, Liverpool L69 3GA, UK
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36
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Haga M, Yamashita A, Paszkowiak J, Sumpio BE, Dardik A. Oscillatory shear stress increases smooth muscle cell proliferation and Akt phosphorylation. J Vasc Surg 2003; 37:1277-84. [PMID: 12764276 DOI: 10.1016/s0741-5214(03)00329-x] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
PURPOSE Hemodynamic forces affect smooth muscle cell (SMC) proliferation and migration both in vitro and in vivo. However, the effects of oscillatory shear stress (SS) on SMC proliferation and signal transduction pathways that control survival are not well described. METHODS Bovine aortic SMC were exposed to arterial levels of oscillatory SS (14 dyne/cm(2)) with an orbital shaker; control cells were exposed to static conditions (0 dyne/cm(2)). Cell number and (3)[H]thymidine incorporation were measured after 1, 3, or 5 days of SS. Activation of the Akt pathway was assessed with the Western blot technique. Specificity of the phosphatidylinositol 3-kinase (PI3K) pathway was determined with the Western blot technique with the inhibitors LY294002 (10 micromol/L) or wortmannin (25 nmol/L). RESULTS Arterial levels of oscillatory SS increased SMC cell number by 20.1 +/- 3.7% and (3)[H]thymidine incorporation by 33.4% +/- 6.8% at 5 days. To identify whether SS increased activity of the SMC survival pathway, Akt activation was measured. SMC exposed to SS demonstrated increased Akt phosphorylation compared with control cells, with maximal phosphorylation at 60 minutes. Both PI3K inhibitors specifically inhibited the increase in Akt phosphorylation in SMC exposed to oscillatory SS. CONCLUSION SMC directly respond to oscillatory SS by increasing DNA synthesis, proliferation, and activation of the PI3K-Akt signal transduction pathway. These results suggest a mechanism of SMC survival and proliferation in response to endothelial-denuding arterial injury.
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Affiliation(s)
- Masae Haga
- Department of Surgery, Section of Vascular Surgery, Yale University School of Medicine, 333 Cedar St, FMB 137, New Haven, CT 06520-8062, USA
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Fisher RK, Kirkpatrick UJ, How TV, Brennan JA, Gilling-Smith GL, Harris PL. The distaflo graft: a valid alternative to interposition vein? Eur J Vasc Endovasc Surg 2003; 25:235-9. [PMID: 12623335 DOI: 10.1053/ejvs.2002.1840] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
INTRODUCTION the rationale behind the Distaflo graft is inhibition of myointimal hyperplasia through optimisation of haemodynamic forces at the distal anastomosis. This prospective study reports our early clinical results. METHOD patients with critical limb ischaemia, but no autologous vein, underwent infrainguinal bypass using Distaflo. Clinical and Duplex assessment provided prospective data from which one year cumulative patency, limb salvage and survival rates were calculated using Kaplan-Meier analysis. Log rank test enabled comparison with an historical control group of Miller cuff grafts. RESULTS fifty Distaflo were inserted over 29 months into 46 patients, median age 68.5 years, 27 male (59%), of which 27 (54%) were re-do procedures. Proximal anastomoses were to common femoral arteries in 40 cases (80%); distal anastomoses were to popliteal vessels in 20 (40%), and tibial vessels in 30 (60%). The Distaflo graft had patency, limb salvage and survival rates of 39, 50 and 82% respectively compared to 49, 56 and 85% respectively in the control group, with no statistical difference (p = 0.39; 0.65; 0.67 respectively; log rank). CONCLUSION in this non-randomised study, the Distaflo has similar one year patency, limb salvage and survival rates to the Miller cuff, potentially justifying its use an alternative in distal prosthetic arterial reconstruction for critical limb ischaemia.
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Affiliation(s)
- R K Fisher
- Regional Vascular Unit, Royal Liverpool University Hospital, UK
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Paszkowiak JJ, Dardik A. Arterial wall shear stress: observations from the bench to the bedside. Vasc Endovascular Surg 2003; 37:47-57. [PMID: 12577139 DOI: 10.1177/153857440303700107] [Citation(s) in RCA: 212] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Shear stress is the tangential force of the flowing blood on the endothelial surface of the blood vessel. Shear is described mathematically or ideal fluids, and in vitro models have enabled researchers to describe the effects of shear on endothelial cells. High shear stress, as found in laminar flow, promotes endothelial cell survival and quiescence, alignment in the direction of flow, and secretion of substances that promote vasodilation and anticoagulation. Low shear stress, or changing shear stress direction as found in turbulent flow, promotes endothelial proliferation and apoptosis, shape change, and secretion of substances that promote vasoconstriction, coagulation, and platelet aggregation. The precise pathways by which endothelial cells sense shear stress to promote their quiescent or activated pathways are currently unknown. Clinical applications include increasing shear stress via creation of an arteriovenous fistula or vein cuff to promote bypass graft flow and patency. Since an abnormal level of shear stress is implicated in the pathogenesis of atherosclerosis, neointimal hyperplasia, and aneurysmal disease, additional research to understand the effects of shear stress on the blood vessel may provide insight to prevent vascular disease.
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Ojha M, Leask RL, Butany J, Johnston KW. Distribution of intimal and medial thickening in the human right coronary artery: a study of 17 RCAs. Atherosclerosis 2001; 158:147-53. [PMID: 11500185 DOI: 10.1016/s0021-9150(00)00759-0] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
OBJECTIVE To quantify the distribution of intimal and medial thickening in human right coronary arteries (RCAs) obtained at autopsy. BACKGROUND The shear and tensile stresses created by arterial bifurcation are believed to result in eccentric fibromuscular intimal thickening that leads to atherosclerosis. Vascular curvature has been cited as a cause of atherosclerosis; however, details of the location and extent of intimal and medial thickness in the largely curved human RCA are not adequately documented. METHODS The right coronary arteries were obtained from 40 postmortem hearts and cut into 20-30 segments, each being 3-4 mm in length. Microscopic sections from the proximal, acute margin, and distal regions of the RCA were digitized around the circumference of the vessel. Seventeen arteries showed insignificant stenosis (<50%) and were selected for detailed examination. RESULTS Seventy-one percent (12/17) of proximal sections displayed eccentric intimal thickening. Normalized ensemble averaging revealed a preferential thickening on the myocardial side of the artery. At the acute margin region where curvature is most pronounced and at the distal region, 51% (8/17) of the samples showed eccentric thickening, but the ensemble average thickening in these regions showed no preferential location. In these mildly diseased arteries, the thickened intima comprised of mainly smooth muscle cells with an extracellular matrix of collagen and some elastin. A relatively uniform medial smooth muscle layer was seen at all three locations. CONCLUSIONS The proximal region of the RCA appears to be a site of intrinsic eccentric intimal thickening with maximum thickness on the myocardial side of the artery. Eccentric thickening does occur in the acute margin and distal regions; however, no distinct pattern or location was evident.
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Affiliation(s)
- M Ojha
- Institute of Biomaterials & Biomedical Engineering, University of Toronto, 4 Taddle Creek Road, Toronto, Ontario, Canada M55 3G9.
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40
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Jackson ZS, Ishibashi H, Gotlieb AI, Langille BL. Effects of anastomotic angle on vascular tissue responses at end-to-side arterial grafts. J Vasc Surg 2001; 34:300-7. [PMID: 11496283 DOI: 10.1067/mva.2001.115815] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
OBJECTIVE Hemodynamics has been implicated in the late failure of arterial bypass grafts, which frequently occurs at the distal anastomosis site. This study was designed to assess the relationship between local hemodynamics and pathologic responses of the distal anastomosis by manipulation of the angle of anastomosis of the graft, a major determinant of local hemodynamics. METHODS End-to-side anastomoses of the right carotid to the left carotid arteries of rabbits were performed at anastomotic angles of less than 10 degrees (acute), 45 degrees (intermediate), or 90 degrees (right angle), and then the upstream left carotid arteries were ligated to simulate pathologic occlusion. We examined tissue responses on the wall of the recipient vessel opposite the anastomosis site (the bed), where unusual hemodynamic forces are imposed. RESULTS Three months after surgery, intimal thickening was observed on the upstream portion of the acute, and more rarely, the intermediate anastomoses only. Medial thinning caused by loss of cells and matrix, and an aneurysm-like dilation, was observed in the right angle and some intermediate anastomoses, but not in the acute anastomoses. En face confocal microscopy at 3 weeks after surgery revealed severe disruption of the internal elastic lamina in all anastomotic models. Zymography and Western immunoblotting demonstrated gelatinolytic activity, caused by expression and activation of MMP-2, that was lowest in the acute anastomoses, higher in the intermediate anastomoses, and highest in the right-angle anastomoses. CONCLUSIONS We infer that very different pathologic changes to the vessel wall are elicited when local hemodynamics is manipulated by altering the anastomotic branch angle.
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Affiliation(s)
- Z S Jackson
- Department of Laboratory Medicine and Pathobiology, University of Toronto, and the Toronto General Research Institute, Ontario, Canada
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41
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Hoedt MT, van Urk H, Hop WC, van der Lugt A, Wittens CH. A Comparison of Distal End-to-side and End-to-end Anastomoses in Femoropopliteal Bypasses. Eur J Vasc Endovasc Surg 2001; 21:266-70. [PMID: 11352686 DOI: 10.1053/ejvs.2000.1283] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
OBJECTIVES to compare end-to-side (ETS) and end-to-end (ETE) distal anastomoses. Design retrospective cohort study. METHODS retrospective cohort study. Between 1988 and 1992, 204 femoropopliteal bypasses (188 patients) were performed for claudication (55%), rest pain (22%) and tissue loss (23%). One hundred and eighteen ETS were compared with 86 ETE in terms of patency or a mean (range) follow-up of 68 (0.5-120) months. RESULTS overall patency was 86%, 66% and 57% at 1, 5 and 8 years, respectively. Multivariate analysis showed ETE anastomoses (p =0.04), and also knee bypass ( p =0.05) and venous conduit ( p =0.004) to be significantly associated with impaired patency. CONCLUSIONS ETE may improve femoropopliteal bypass patency.
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Affiliation(s)
- M T Hoedt
- Department of Vascular Surgery, Erasmus University Medical Centre Rotterdam, P.O. Box 2040, Rotterdam, The Netherlands
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Fisher RK, How TV, Carpenter T, Brennan JA, Harris PL. Optimising Miller Cuff Dimensions. The Influence of Geometry on Anastomotic Flow Patterns. Eur J Vasc Endovasc Surg 2001; 21:251-60. [PMID: 11352685 DOI: 10.1053/ejvs.2000.1273] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
OBJECTIVES since cuff dimensions are variable, we studied the influence of cuff geometry on flow mechanics, in an attempt to identify the optimum configuration. MATERIALS AND METHODS bench studies involved the manufacture of anatomically accurate models of varying cuff dimensions, perfused in a specifically designed flow rig, simulating physiological conditions. Flow visualisation studies incorporating laser illumination of tracer particles enabled accurate analysis of flow patterns. RESULTS the vortex created within the proximal cuff of each model during the deceleration phase of the cardiac cycle was strongly influenced by the aspect ratio (AR=cuff height:length). The standard and high cuffs (AR=1.63 and 1.18, respectively) demonstrated cohesive vortices and stable flow patterns. Low and long cuffs (AR=2.6 and 2.25, respectively) created more complex vortices with large areas of flow separation and low velocities. CONCLUSIONS aspect ratio has an important influence on flow within the distal anastomosis, with cuff dimensions of 13 mm long and 8-11 mm high (standard and high cuffs) creating beneficial flow patterns anticipated to optimise wall shear stress and inhibit myointimal hyperplasia.
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Affiliation(s)
- R K Fisher
- Regional Vascular Unit and Department of Clinical Engineering, Royal Liverpool University Hospital, Daulby Street, Liverpool L69 3GA, U.K
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Shigematsu K, Yasuhara H, Shigematsu H. Topical application of antiangiogenic agent AGM-1470 suppresses anastomotic intimal hyperplasia after ePTFE grafting in a rabbit model. Surgery 2001; 129:220-30. [PMID: 11174715 DOI: 10.1067/msy.2001.110769] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
BACKGROUND Anastomotic intimal hyperplasia (AIH) remains an unsolved problem. Angiogenesis around the anastomosis is one of the important mechanisms accelerating AIH. In this study, we investigated the effects of an antiangiogenic agent AGM-1470 (O-[chloroacetyl-carbamoyl] fumagillol: AGM) on the thickness of AIH after expanded polytetrafluoroethylene grafting. METHODS Study 1: Smooth muscle cells (SMCs) were cultured to form 3-mm-side square colonies by using 4 kinds of culture medium, containing AGM at concentrations of 0, 0.1, 1.0, and 10 ng/mL. The SMC colony spreading distance in each group was measured as an index of mitogenic activity. The isolated proliferative activity of SMCs was also assessed. Study 2: Male New Zealand white rabbits underwent inlay expanded polytetrafluoroethylene grafting of the carotid arteries. They were divided in 4 groups (control, vehicle, AGM [0.5], and AGM [5]) in which no topical application, Vaseline ointment, Vaseline ointment containing 0.5 mg AGM, or Vaseline ointment containing 5 mg AGM was applied to the anastomoses, respectively. Rabbits were fed a high-cholesterol diet for 2 weeks before and 8 weeks after the operation. AIH thickness was measured and capillary formation and SMC accumulation around the anastomoses were examined with immunohistochemical staining. RESULTS Study 1: AGM suppressed SMC migratory activity in a cytostatic, but not cytotoxic, manner. Study 2: AGM ointment inhibited AIH in proportion to its concentration and also suppressed new capillary formation around the anastomoses and SMC accumulation in AIH. CONCLUSIONS Topical application of the antiangiogenic agent AGM may become an important strategy for preventing AIH.
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Affiliation(s)
- K Shigematsu
- Department of Surgery, The University of Tokyo, Tokyo, Japan
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44
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Freischlag JA. Regarding "the effect of venous anastomosis Tyrell vein patch collar on the primary patency of arteriovenous grafts in patients undergoing hemodialysis" and "effects of a venous cuff at the venous anastomosis of polytetrafluoroethylene grafts for hemodialysis vascular access". J Vasc Surg 2000; 32:1235-6. [PMID: 11107101 DOI: 10.1067/mva.2000.109205] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- J A Freischlag
- UCLA Gonda Goldschmied Vascular Center, Los Angeles, CA 90095-6908, USA.
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45
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Lipton MJ, Boxt LM, Hijazi ZM. Role of the radiologist in cardiac diagnostic imaging. AJR Am J Roentgenol 2000; 175:1495-506. [PMID: 11090363 DOI: 10.2214/ajr.175.6.1751495] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Affiliation(s)
- M J Lipton
- Department of Radiology, University of Chicago, MC 2026, Chicago, IL 60637, USA
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46
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Patel RP, Moellering D, Murphy-Ullrich J, Jo H, Beckman JS, Darley-Usmar VM. Cell signaling by reactive nitrogen and oxygen species in atherosclerosis. Free Radic Biol Med 2000; 28:1780-94. [PMID: 10946220 DOI: 10.1016/s0891-5849(00)00235-5] [Citation(s) in RCA: 166] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The production of reactive oxygen and nitrogen species has been implicated in atherosclerosis principally as means of damaging low-density lipoprotein that in turn initiates the accumulation of cholesterol in macrophages. The diversity of novel oxidative modifications to lipids and proteins recently identified in atherosclerotic lesions has revealed surprising complexity in the mechanisms of oxidative damage and their potential role in atherosclerosis. Oxidative or nitrosative stress does not completely consume intracellular antioxidants leading to cell death as previously thought. Rather, oxidative and nitrosative stress have a more subtle impact on the atherogenic process by modulating intracellular signaling pathways in vascular tissues to affect inflammatory cell adhesion, migration, proliferation, and differentiation. Furthermore, cellular responses can affect the production of nitric oxide, which in turn can strongly influence the nature of oxidative modifications occurring in atherosclerosis. The dynamic interactions between endogenous low concentrations of oxidants or reactive nitrogen species with intracellular signaling pathways may have a general role in processes affecting wound healing to apoptosis, which can provide novel insights into the pathogenesis of atherosclerosis.
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Affiliation(s)
- R P Patel
- Center for Free Radical Biology, University of Alabama, Birmingham, AL 35294-0019, USA
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47
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How TV, Rowe CS, Gilling-Smith GL, Harris PL. Interposition vein cuff anastomosis alters wall shear stress distribution in the recipient artery. J Vasc Surg 2000; 31:1008-17. [PMID: 10805893 DOI: 10.1067/mva.2000.105961] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
OBJECTIVE Interposition of a vein cuff between a prosthetic infrainguinal bypass graft and a recipient infrageniculate artery can improve graft patency. There is evidence that the improved performance may be explained by a redistribution of myointimal hyperplasia (MIH) away from the critical areas at the heel and toe of the cuff-artery anastomosis. It is widely accepted that there is an association between hemodynamic forces, more specifically, low wall shear stress (WSS), and the development of MIH. The aim of this study was to determine whether the reported redistribution of MIH in the interposition vein cuff (IVC) may be explained by differences in magnitude and distribution of WSS. Design of Study and Method: Detailed flow velocity measurements were made in life-size models of conventional end-to-side (ETS) and IVC anastomoses using a two-component laser Doppler anemometer under pulsatile flow conditions. Velocity vectors were determined in the plane of symmetry of the anastomosis, and the variation of WSS was estimated from near-wall velocity measurements on the floor and upper wall of the artery. RESULTS The main flow features in the ETS anastomosis were flow separation at the graft hood, strong radial velocity at the heel, and a stagnation point on the floor of the artery that moved slightly during the flow cycle. In the IVC anastomosis, a coherent vortex that occupied most of the cuff volume was present from the systolic deceleration phase to end diastole. A stagnation point on the anastomosis floor was found to oscillate by about 4 mm. Critical regions of low mean WSS (ie, below 0.5 N/m(2)) were identified. In the ETS anastomosis, they were found at the heel and along the floor. In the IVC anastomosis, low mean WSS was found only on the floor, and it was generally less extensive than in the ETS anastomosis. CONCLUSION The vein cuff anastomosis alters the mean WSS distribution within the recipient artery and removes the area of low WSS at the heel. This may explain the redistribution of MIH away from important sites in the recipient artery.
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Affiliation(s)
- T V How
- Department of Clinical Engineering, University of Liverpool, Regional Vascular Unit, Royal Liverpool University Hospital, United Kingdom
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48
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Kaiura TL, Itoh H, Kubaska SM, McCaffrey TA, Liu B, Kent K. The effect of growth factors, cytokines, and extracellular matrix proteins on fibronectin production in human vascular smooth muscle cells. J Vasc Surg 2000. [DOI: 10.1067/mva.2000.103692] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
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49
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Abstract
PURPOSE Intimal hyperplasia at the venous anastomosis of dialysis access grafts causes early failure, although increased flow inhibits intimal hyperplasia in arterial grafts and after vessel injury. We designed a sheep model to study this process. METHODS Polytetrafluoroethylene (PTFE) grafts were placed in the necks of sheep from the carotid artery to the external jugular vein. Grafts were harvested after perfusion fixation at 4, 8, and 12 weeks and submitted for histologic and immunohistochemical examination, including morphometry of neointimal lesions. RESULTS The venous anastomoses developed thick neointima within the PTFE graft by 4 weeks. Lesions at the venous end were significantly thicker than those at the arterial end by 8 weeks (1.2 +/- 0.1 vs 0.38 +/- 0.05 mm, P <.02) and had greater cross-sectional area at both 4 (0.32 +/- 0.21 vs 3.6 +/- 0.8 mm(2), n = 7, P <.02) and 8 weeks (9.8 +/- 1.9 vs 1.1 +/- 0.7 mm(2), n = 7, P <.02). Only one of the four grafts (25%) in the 12-week group remained patent. Lesions were composed of smooth muscle cells, matrix, and thrombus of various ages. Cellular proliferation was prominent in neointima adjacent to thrombus and in granulation tissue surrounding the graft. Organizing thrombus contributed significantly to luminal narrowing. CONCLUSION The sheep model of dialysis access reliably produces venous stenosis within 4 weeks. Lesions develop in the absence of uremia, graft puncture, or dialysis, suggesting that these factors are not necessary for graft failure. The continued presence of thrombus and high rates of cellular proliferation suggest ongoing injury is an important cause of lesion formation. This model allows study of the cellular mechanisms of dialysis failure.
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Affiliation(s)
- T R Kohler
- Department of Surgery, University of Washington, the VA Puget Sound Health Care System, Seattle 98108, USA
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50
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Masuda H, Zhuang YJ, Singh TM, Kawamura K, Murakami M, Zarins CK, Glagov S. Adaptive remodeling of internal elastic lamina and endothelial lining during flow-induced arterial enlargement. Arterioscler Thromb Vasc Biol 1999; 19:2298-307. [PMID: 10521357 DOI: 10.1161/01.atv.19.10.2298] [Citation(s) in RCA: 117] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Gaps in the internal elastic lamina (IEL) have been observed in arteries exposed to high blood flow. To characterize the nature and consequences of this change, blood flow was increased in the carotid arteries of 56 adult, male, Japanese white rabbits by creating an arteriovenous fistula between the common carotid artery and the external jugular vein. The common carotid artery proximal to the arteriovenous fistula was studied at intervals from 1 hour to 8 weeks after exposure to high flow. In the controls, the IEL showed only the usual, small, physiological holes, 2 to 10 microm in diameter. At 3 days, some of the holes in the IEL had become enlarged, but they could not be detected by scanning electron microscopy, despite manifest endothelial cell proliferation. At 4 days, gaps in the IEL appeared as small, luminal surface depressions, 15 to 50 microm wide. At 7 days, the gaps in the IEL had enlarged and formed circumferential, luminal depressions occupying 15+/-5% of the lumen surface. Endothelial cell proliferation persisted in the gaps while proliferative activity decreased where the IEL remained intact. At 4 weeks, as the artery became elongated and dilated, the gaps in the IEL widened as intercommunicating circumferential and longitudinal luminal depressions occupying 64+/-5% of the lumen surface. At 8 weeks, the rate of elongation and dilatation of the artery slowed and the widening of the gaps in the IEL diminished. Endothelial cells covered the gaps throughout. We conclude that flow-induced arterial dilatation is accompanied by an adaptive remodeling of the intima. The gaps in the IEL permit an increase in lumen surface area while endothelial cell proliferation assures a continuous cell lining throughout.
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MESH Headings
- Animals
- Antimetabolites/metabolism
- Antimetabolites/pharmacology
- Blood Flow Velocity/physiology
- Blood Pressure/physiology
- Bromodeoxyuridine/metabolism
- Bromodeoxyuridine/pharmacology
- Carotid Artery, Common/pathology
- Carotid Artery, Common/physiology
- Carotid Artery, Common/ultrastructure
- Cell Count
- Cell Division/physiology
- Elastic Tissue/pathology
- Elastic Tissue/physiology
- Endothelium, Vascular/cytology
- Endothelium, Vascular/physiology
- Endothelium, Vascular/ultrastructure
- Male
- Microscopy, Electron, Scanning
- Muscle, Smooth, Vascular/pathology
- Muscle, Smooth, Vascular/physiology
- Muscle, Smooth, Vascular/ultrastructure
- Rabbits
- Vasodilation/physiology
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Affiliation(s)
- H Masuda
- Second Department of Pathology, Akita University School of Medicine, Hondo, Japan.
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