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Louwagie T, Wagner M, Li R, Yu G, Petersen A, Hubel A. Characterizing cellular membrane partitioning of DMSO using low-temperature Raman spectroscopy. Front Mol Biosci 2023; 10:1144059. [PMID: 36911529 PMCID: PMC9994731 DOI: 10.3389/fmolb.2023.1144059] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2023] [Accepted: 02/10/2023] [Indexed: 02/24/2023] Open
Abstract
Additives that help cells survive the stresses of freezing and thawing are known as cryoprotective agents (CPAs). Two different types of CPAs have been identified: penetrating and non-penetrating. Common penetrating CPAs include dimethylsulfoxide (DMSO) and glycerol. The location of a CPA (intracelluar or extracellular) is important for understanding the molecular mechanisms of action for the agent. Low-temperature Raman spectroscopy is a label-free method of detecting the location of CPAs at low temperature with high spatial resolution and chemical specificity. To this end, cells cryopreserved in DMSO using a variety of cooling rates and DMSO concentrations and imaged using Raman spectroscopy were analyzed using automated image analysis to determine the partitioning ratio (concentration of DMSO outside/concentration of DMSO inside the cell). The partitioning ratio was roughly 1 for Jurkat cells frozen at 1°C/min in varying concentrations of DMSO with the exception of 1% DMSO which had a partitioning ratio of 0.2. The partitioning ratio increased from 1 to 1.3 as the cooling rate increased from 1°C to 5°C/min. Different cell types, specifically sensory neurons cells and human induced pluripotent stem cells, exhibited differences in partitioning ratio when frozen in 10% DMSO and 1°C/min suggesting that differences in freezing response may result from differences in solute partitioning. The presence of intracellular ice changed the distribution of DMSO inside the cell and also the partitioning ratio.
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Affiliation(s)
- Troy Louwagie
- Department of Mechanical Engineering, University of Minnesota Twin Cities, Minneapolis, MN, United States
| | - Madeline Wagner
- Department of Mechanical Engineering, University of Minnesota Twin Cities, Minneapolis, MN, United States
| | - Rui Li
- Department of Biomedical Engineering, University of Minnesota Twin Cities, Minneapolis, MN, United States
| | - Guanglin Yu
- Department of Mechanical Engineering, University of Minnesota Twin Cities, Minneapolis, MN, United States
| | - Ashley Petersen
- Division of Biostatistics, University of Minnesota Twin Cities, Minneapolis, MN, United States
| | - Allison Hubel
- Department of Mechanical Engineering, University of Minnesota Twin Cities, Minneapolis, MN, United States
- Department of Biomedical Engineering, University of Minnesota Twin Cities, Minneapolis, MN, United States
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2
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Luo RH, Tram NK, Parekh AM, Puri R, Reilly MA, Swindle-Reilly KE. The Roles of Vitreous Biomechanics in Ocular Disease, Biomolecule Transport, and Pharmacokinetics. Curr Eye Res 2023; 48:195-207. [PMID: 35179421 DOI: 10.1080/02713683.2022.2033271] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
PURPOSE The biomechanical properties of the vitreous humor and replication of these properties to develop substitutes for the vitreous humor have rapidly become topics of interest over the last two decades. In particular, the behavior of the vitreous humor as a viscoelastic tissue has been investigated to identify its role in a variety of processes related to biotransport, aging, and age-related pathologies of the vitreoretinal interface. METHODS A thorough search and review of peer-reviewed publications discussing the biomechanical properties of the vitreous humor in both human and animal specimens was conducted. Findings on the effects of biomechanics on vitreoretinal pathologies and vitreous biotransport were analyzed and discussed. RESULTS The pig and rabbit vitreous have been found to be most mechanically similar to the human vitreous. Age-related liquefaction of the vitreous creates two mechanically unique phases, with an overall effect of softening the vitreous. However, the techniques used to acquire this mechanical data are limited by the in vitro testing methods used, and the vitreous humor has been hypothesized to behave differently in vivo due in part to its swelling properties. The impact of liquefaction and subsequent detachment of the vitreous humor from the posterior retinal surface is implicated in a variety of tractional pathologies of the retina and macula. Liquefaction also causes significant changes in the biotransport properties of the eye, allowing for significantly faster movement of molecules compared to the healthy vitreous. Recent developments in computational and ex vivo models of the vitreous humor have helped with understanding its behavior and developing materials capable of replacing it. CONCLUSIONS A better understanding of the biomechanical properties of the vitreous humor and how these relate to its structure will potentially aid in improving clinical metrics for vitreous liquefaction, design of biomimetic vitreous substitutes, and predicting pharmacokinetics for intravitreal drug delivery.
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Affiliation(s)
- Richard H Luo
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, USA
| | - Nguyen K Tram
- Center for Regenerative Medicine, The Research Institute at Nationwide Children's Hospital, Columbus, OH, USA
| | - Ankur M Parekh
- William G. Lowrie Department of Chemical and Biomolecular Engineering, The Ohio State University, Columbus, OH, USA
| | - Raima Puri
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, USA
| | - Matthew A Reilly
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, USA.,Department of Ophthalmology and Visual Sciences, The Ohio State University, Columbus, OH, USA
| | - Katelyn E Swindle-Reilly
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, USA.,William G. Lowrie Department of Chemical and Biomolecular Engineering, The Ohio State University, Columbus, OH, USA.,Department of Ophthalmology and Visual Sciences, The Ohio State University, Columbus, OH, USA
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3
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Habib M, Hussien S, Jeon O, Lotz JC, Wu PIK, Alsberg E, Fields AJ. Intradiscal treatment of the cartilage endplate for improving solute transport and disc nutrition. Front Bioeng Biotechnol 2023; 11:1111356. [PMID: 36923455 PMCID: PMC10008947 DOI: 10.3389/fbioe.2023.1111356] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Accepted: 02/09/2023] [Indexed: 03/03/2023] Open
Abstract
Poor nutrient transport through the cartilage endplate (CEP) is a key factor in the etiology of intervertebral disc degeneration and may hinder the efficacy of biologic strategies for disc regeneration. Yet, there are currently no treatments for improving nutrient transport through the CEP. In this study we tested whether intradiscal delivery of a matrix-modifying enzyme to the CEP improves solute transport into whole human and bovine discs. Ten human lumbar motion segments harvested from five fresh cadaveric spines (38-66 years old) and nine bovine coccygeal motion segments harvested from three adult steers were treated intradiscally either with collagenase enzyme or control buffer that was loaded in alginate carrier. Motion segments were then incubated for 18 h at 37 °C, the bony endplates removed, and the isolated discs were compressed under static (0.2 MPa) and cyclic (0.4-0.8 MPa, 0.2 Hz) loads while submerged in fluorescein tracer solution (376 Da; 0.1 mg/ml). Fluorescein concentrations from site-matched nucleus pulposus (NP) samples were compared between discs. CEP samples from each disc were digested and assayed for sulfated glycosaminoglycan (sGAG) and collagen contents. Results showed that enzymatic treatment of the CEP dramatically enhanced small solute transport into the disc. Discs with enzyme-treated CEPs had up to 10.8-fold (human) and 14.0-fold (bovine) higher fluorescein concentration in the NP compared to site-matched locations in discs with buffer-treated CEPs (p < 0.0001). Increases in solute transport were consistent with the effects of enzymatic treatment on CEP composition, which included reductions in sGAG content of 33.5% (human) and 40% (bovine). Whole disc biomechanical behavior-namely, creep strain and disc modulus-was similar between discs with enzyme- and buffer-treated CEPs. Taken together, these findings demonstrate the potential for matrix modification of the CEP to improve the transport of small solutes into whole intact discs.
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Affiliation(s)
- Mohamed Habib
- Department of Orthopaedic Surgery, University of California, San Francisco, San Francisco, CA, United States.,Department of Mechanical Engineering, Al Azhar University, Cairo, Egypt
| | - Shayan Hussien
- Department of Orthopaedic Surgery, University of California, San Francisco, San Francisco, CA, United States
| | - Oju Jeon
- Department of Biomedical Engineering, University of Illinois, Chicago, IL, United States
| | - Jeffrey C Lotz
- Department of Orthopaedic Surgery, University of California, San Francisco, San Francisco, CA, United States
| | - Peter I-Kung Wu
- Department of Orthopaedic Surgery, University of California, San Francisco, San Francisco, CA, United States
| | - Eben Alsberg
- Department of Biomedical Engineering, University of Illinois, Chicago, IL, United States
| | - Aaron J Fields
- Department of Orthopaedic Surgery, University of California, San Francisco, San Francisco, CA, United States
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Ruan G, Huang P, Mei L, Rao SS. Editorial: Biological Delivery: Bridging Fundamental Research With the Clinic and Industry. Front Bioeng Biotechnol 2022; 10:948064. [PMID: 35757792 PMCID: PMC9214196 DOI: 10.3389/fbioe.2022.948064] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2022] [Accepted: 05/20/2022] [Indexed: 11/13/2022] Open
Affiliation(s)
- Gang Ruan
- Wisdom Lake Academy of Pharmacy, Xi'an Jiaotong-Liverpool University, Suzhou, China
| | - Peng Huang
- School of Biomedical Engineering, Shenzhen University, Shenzhen, China
| | - Lin Mei
- School of Pharmaceuticals Sciences (Shenzhen), Sun Yat-Sen University, Guangzhou, China
| | - Shreyas S Rao
- Department of Chemical and Biological Engineering, The University of Alabama, Tuscaloosa, AL, United States
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5
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Zhong Y, Caplan AI, Welter JF, Baskaran H. Glucose Availability Affects Extracellular Matrix Synthesis During Chondrogenesis In Vitro. Tissue Eng Part A 2021; 27:1321-1332. [PMID: 33499734 PMCID: PMC8610032 DOI: 10.1089/ten.tea.2020.0144] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2020] [Accepted: 01/22/2021] [Indexed: 01/09/2023] Open
Abstract
Understanding in vitro chondrogenesis of human mesenchymal stem cells (hMSCs) is important as it holds great promise for cartilage tissue engineering and other applications. The current technology produces the end tissue quality that is highly variable and dependent on culture conditions. We investigated the effect of nutrient availability on hMSC chondrogenesis in a static aggregate culture system by varying the medium-change frequency together with starting glucose levels. Glucose uptake and lactate secretion profiles were obtained to monitor the metabolism change during hMSC chondrogenesis with different culture conditions. Higher medium-change frequency led to increases in cumulative glucose uptake for all starting glucose levels. Furthermore, increase in glucose uptake by aggregates led to increased end tissue glycosaminoglycan (GAG) and hydroxyproline (HYP) content. The results suggest that increased glucose availability either through increased medium-change frequency or higher initial glucose levels lead to improved chondrogenesis. Also, cumulative glucose uptake and lactate secretion were found to correlate well with GAG and HYP content, indicating both molecules are promising biomarkers for noninvasive assessment of hMSC chondrogenesis. Collectively, our results can be used to design optimal culture conditions and develop dynamic assessment strategies for cartilage tissue engineering applications. Impact statement In this study, we investigated how culture conditions, medium-change frequency and glucose levels, affect chondrogenesis of human mesenchymal stem cells in an aggregate culture model. Doubling the medium-change frequency significantly increased the biochemical quality of the resultant tissue aggregates, as measured by their glycosaminoglycan and hydroxyproline content. We attribute this to increased glucose uptake through the glycolysis pathway, as secretion of lactate, a key endpoint product of the glycolysis pathway, increased concurrently. These findings can be used to design optimal culture conditions for tissue engineering and regenerative medicine applications.
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Affiliation(s)
- Yi Zhong
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio, USA
- CWRU Center for Multimodal Evaluation of Engineered Cartilage, Case Western Reserve University, Cleveland, Ohio, USA
| | - Arnold I. Caplan
- CWRU Center for Multimodal Evaluation of Engineered Cartilage, Case Western Reserve University, Cleveland, Ohio, USA
- Department of Biology and Case Western Reserve University, Cleveland, Ohio, USA
| | - Jean F. Welter
- CWRU Center for Multimodal Evaluation of Engineered Cartilage, Case Western Reserve University, Cleveland, Ohio, USA
- Department of Biology and Case Western Reserve University, Cleveland, Ohio, USA
| | - Harihara Baskaran
- CWRU Center for Multimodal Evaluation of Engineered Cartilage, Case Western Reserve University, Cleveland, Ohio, USA
- Department of Chemical and Biomolecular Engineering, Case Western Reserve University, Cleveland, Ohio, USA
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6
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Tram NK, Maxwell CJ, Swindle-Reilly KE. Macro- and Microscale Properties of the Vitreous Humor to Inform Substitute Design and Intravitreal Biotransport. Curr Eye Res 2020; 46:429-444. [PMID: 33040616 DOI: 10.1080/02713683.2020.1826977] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Research on the vitreous humor and development of hydrogel vitreous substitutes have gained a rapid increase in interest within the past two decades. However, the properties of the vitreous humor and vitreous substitutes have yet to be consolidated. In this paper, the mechanical properties of the vitreous humor and hydrogel vitreous substitutes were systematically reviewed. The number of publications on the vitreous humor and vitreous substitutes over the years, as well as their respective testing conditions and testing techniques were analyzed. The mechanical properties of the human vitreous were found to be most similar to the vitreous of pigs and rabbits. The storage and loss moduli of the hydrogel vitreous substitutes developed were found to be orders of magnitude higher in comparison to the native human vitreous. However, the reported modulus for human vitreous, which was most commonly tested in vitro, has been hypothesized to be different in vivo. Future studies should focus on testing the mechanical properties of the vitreous in situ or in vivo. In addition to its mechanical properties, the vitreous humor has other biotransport mechanisms and biochemical functions that establish a redox balance and maintain an oxygen gradient inside the vitreous chamber to protect intraocular tissues from oxidative damage. Biomimetic hydrogel vitreous substitutes have the potential to provide ophthalmologists with additional avenues for treating and controlling vitreoretinal diseases while preventing complications after vitrectomy. Due to the proximity and interconnectedness of the vitreous humor to other ocular tissues, particularly the lens and the retina, more interest has been placed on understanding the properties of the vitreous humor in recent years. A better understanding of the properties of the vitreous humor will aid in improving the design of biomimetic vitreous substitutes and enhancing intravitreal biotransport.
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Affiliation(s)
- Nguyen K Tram
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, USA
| | - Courtney J Maxwell
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, USA
| | - Katelyn E Swindle-Reilly
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, USA.,William G. Lowrie Department of Chemical and Biomolecular Engineering, The Ohio State University, Columbus, OH, USA.,Department of Ophthalmology & Visual Science, The Ohio State University, Columbus, OH, USA
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Schoeman RM, Rana K, Danes N, Lehmann M, Di Paola JA, Fogelson AL, Leiderman K, Neeves KB. A microfluidic model of hemostasis sensitive to platelet function and coagulation. Cell Mol Bioeng 2016; 10:3-15. [PMID: 28529666 DOI: 10.1007/s12195-016-0469-0] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
Abstract
Hemostasis is the process of sealing a vascular injury with a thrombus to arrest bleeding. The type of thrombus that forms depends on the nature of the injury and hemodynamics. There are many models of intravascular thrombus formation whereby blood is exposed to prothrombotic molecules on a solid substrate. However, there are few models of extravascular thrombus formation whereby blood escapes into the extravascular space through a hole in the vessel wall. Here, we describe a microfluidic model of hemostasis that includes vascular, vessel wall, and extravascular compartments. Type I collagen and tissue factor, which support platelet adhesion and initiate coagulation, respectively, were adsorbed to the wall of the injury channel and act synergistically to yield a stable thrombus that stops blood loss into the extravascular compartment in ~7.5 min. Inhibiting factor VIII to mimic hemophilia A results in an unstable thrombus that was unable to close the injury. Treatment with a P2Y12 antagonist to reduce platelet activation prolonged the closure time two-fold compared to controls. Taken together, these data demonstrate a hemostatic model that is sensitive to both coagulation and platelet function and can be used to study coagulopathies and platelet dysfunction that result in excessive blood loss.
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Affiliation(s)
- R M Schoeman
- Chemical and Biological Engineering Department, Colorado School of Mines, Golden, CO
| | - K Rana
- Chemical and Biological Engineering Department, Colorado School of Mines, Golden, CO
| | - N Danes
- Applied Mathematics and Statistics Department, Colorado School of Mines, Golden, CO
| | - M Lehmann
- Chemical and Biological Engineering Department, Colorado School of Mines, Golden, CO
| | - J A Di Paola
- Department of Pediatrics, University of Colorado Denver, Aurora, CO
| | - A L Fogelson
- Departments of Mathematics and Bioengineering, University of Utah, Salt Lake City, Utah
| | - K Leiderman
- Department of Pediatrics, University of Colorado Denver, Aurora, CO
| | - K B Neeves
- Chemical and Biological Engineering Department, Colorado School of Mines, Golden, CO.,Department of Pediatrics, University of Colorado Denver, Aurora, CO
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8
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Abstract
Intravascular blood clots form in an environment in which hydrodynamic forces dominate and in which fluid-mediated transport is the primary means of moving material. The clotting system has evolved to exploit fluid dynamic mechanisms and to overcome fluid dynamic challenges to ensure that clots that preserve vascular integrity can form over the wide range of flow conditions found in the circulation. Fluid-mediated interactions between the many large deformable red blood cells and the few small rigid platelets lead to high platelet concentrations near vessel walls where platelets contribute to clotting. Receptor-ligand pairs with diverse kinetic and mechanical characteristics work synergistically to arrest rapidly flowing cells on an injured vessel. Variations in hydrodynamic stresses switch on and off the function of key clotting polymers. Protein transport to, from, and within a developing clot determines whether and how fast it grows. We review ongoing experimental and modeling research to understand these and related phenomena.
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Affiliation(s)
- Aaron L. Fogelson
- Departments of Mathematics and Bioengineering, University of Utah, Salt Lake City, Utah 84112
| | - Keith B. Neeves
- Department of Chemical and Biological Engineering, Colorado School of Mines, Golden, Colorado 80401
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9
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Kenney LA, von Hippel FA, Willacker JJ, O’Hara TM. Mercury concentrations of a resident freshwater forage fish at Adak Island, Aleutian Archipelago, Alaska. Environ Toxicol Chem 2012; 31:2647-2652. [PMID: 22912068 PMCID: PMC4433311 DOI: 10.1002/etc.1990] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2012] [Revised: 05/05/2012] [Accepted: 07/29/2012] [Indexed: 06/01/2023]
Abstract
The Aleutian Archipelago is an isolated arc of over 300 volcanic islands stretching 1,600 km across the interface of the Bering Sea and North Pacific Ocean. Although remote, some Aleutian Islands were heavily impacted by military activities from World War II until recently and were exposed to anthropogenic contaminants, including mercury (Hg). Mercury is also delivered to these islands via global atmospheric transport, prevailing ocean currents, and biotransport by migratory species. Mercury contamination of freshwater ecosystems is poorly understood in this region. Total Hg (THg) concentrations were measured in threespine stickleback fish (Gasterosteus aculeatus) collected from eight lakes at Adak Island, an island in the center of the archipelago with a long military history. Mean THg concentrations for fish whole-body homogenates for all lakes ranged from 0.314 to 0.560 mg/kg dry weight. Stickleback collected from seabird-associated lakes had significantly higher concentrations of THg compared to non-seabird lakes, including all military lakes. The δ(13)C stable isotope ratios of stickleback collected from seabird lakes suggest an input of marine-derived nutrients and/or marine-derived Hg.
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Affiliation(s)
- Leah A. Kenney
- Department of Biological Sciences, and Environment and Natural Resources Institute, University of Alaska Anchorage, Anchorage, Alaska, USA
| | - Frank A. von Hippel
- Department of Biological Sciences, and Environment and Natural Resources Institute, University of Alaska Anchorage, Anchorage, Alaska, USA
| | - James J. Willacker
- Department of Biological Sciences, and Environment and Natural Resources Institute, University of Alaska Anchorage, Anchorage, Alaska, USA
- Department of Biology and Wildlife, University of Alaska Fairbanks, Fairbanks, Alaska, USA
| | - Todd M. O’Hara
- Department of Biology and Wildlife, University of Alaska Fairbanks, Fairbanks, Alaska, USA
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Helm CLE, Fleury ME, Zisch AH, Boschetti F, Swartz MA. Synergy between interstitial flow and VEGF directs capillary morphogenesis in vitro through a gradient amplification mechanism. Proc Natl Acad Sci U S A 2005; 102:15779-84. [PMID: 16249343 PMCID: PMC1276047 DOI: 10.1073/pnas.0503681102] [Citation(s) in RCA: 195] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2005] [Accepted: 09/17/2005] [Indexed: 11/18/2022] Open
Abstract
Cell organization is largely orchestrated by extracellular gradients of morphogenetic proteins. VEGF, an essential factor for capillary formation, is stored in the extracellular matrix, but the mechanisms by which it and other matrix-bound morphogens are mobilized to form spatial gradients are poorly understood. Here, we suggest an efficient mechanism for morphogen gradient generation by subtle biophysical forces in an in vitro model of capillary morphogenesis. Using a fibrin-bound VEGF variant that is released proteolytically to mimic the in vivo situation, we report that low levels of interstitial flow act synergistically with VEGF to drive endothelial organization, whereas each stimulus alone has very little effect. To help account for this synergy, we show how these slow flows can bias the distribution of cell-secreted proteases, which leads, interestingly, to the creation of an increasing VEGF gradient relative to the cell and skewed in the direction of flow. In contrast, diffusion alone can only account for symmetric, decreasing autocrine gradients. Indeed, branching of capillary structures was biased in the direction of flow only with the combination of VEGF and flow. This work thus demonstrates a general mechanism of morphogen gradient generation and amplification by small ubiquitous mechanical forces that are known to exist in vivo.
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Affiliation(s)
- Cara-Lynn E Helm
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, IL 60208, USA
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