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Abstract
Background High frequency ultrasound has facilitated in vivo measurements of murine ascending aortas, allowing aortic strains to be gleaned from two-dimensional images. Thoracic aortic aneurysms associated with mutations in fibrillin-1 (FBN1) display elastin fragmentation, which may impact aortic strain. In this study, we determined the relationship between elastin fragmentation and aortic circumferential strain in wild type and fibrillin-1 hypomorphic (FBN1 mgR/mgR) mice. Methods and Results Luminal diameters of the ascending aorta from wild type and FBN1 hypomorphic (FBN1 mgR/mgR) mice were measured in systole and diastole. Expansion of the ascending aorta during systole in male and female wild type mice was 0.21±0.02 mm (16.3%) and 0.21±0.01 mm (17.0%) respectively, while expansion in male and female FBN1 mgR/mgR mice was 0.11±0.04 mm (4.9%) and 0.07±0.02 mm (4.5%) respectively. Reduced circumferential strain was observed in FBN1 mgR/mgR mice compared to wild type littermates. Elastin fragmentation was inversely correlated to circumferential strain (R^2 = 0.628 p = 0.004) and significantly correlated with aortic diameter. (R^2 = 0.397, p = 0.038 in systole and R^2 = 0.515, p =0.013 in diastole). Conclusions FBN1 mgR/mgR mice had increased aortic diameters, reduced circumferential strain, and increased elastin fragmentation. Elastin fragmentation in FBN1 mgR/mgR and their wild type littermates was correlated with reduced circumferential strain.
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Affiliation(s)
- Jeff Z Chen
- Saha Cardiovascular Research Center.,Department of Physiology
| | | | | | | | - Alan Daugherty
- Saha Cardiovascular Research Center.,Department of Physiology
| | - Mary B Sheppard
- Saha Cardiovascular Research Center.,Department of Physiology.,Department of Family and Community Medicine.,Department of Surgery, University of Kentucky, Lexington, KY
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Jiménez-Altayó F, Siegert AM, Bonorino F, Meirelles T, Barberà L, Dantas AP, Vila E, Egea G. Differences in the Thoracic Aorta by Region and Sex in a Murine Model of Marfan Syndrome. Front Physiol 2017; 8:933. [PMID: 29187826 PMCID: PMC5694786 DOI: 10.3389/fphys.2017.00933] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2017] [Accepted: 11/03/2017] [Indexed: 12/27/2022] Open
Abstract
Marfan syndrome (MFS) is a hereditary disorder of the connective tissue that causes life-threatening aortic aneurysm, which initiates at the aortic root and can progress into the ascending portion. However, analysis of ascending aorta reactivity in animal models of MFS has remained elusive. Epidemiologic evidence suggests that although MFS is equally prevalent in men and women, men are at a higher risk of aortic complications than non-pregnant women. Nevertheless, there is no experimental evidence to support this hypothesis. The aim of this study was to explore whether there are regional and sex differences in the thoracic aorta function of mice heterozygous for the fibrillin 1 (Fbn1) allele encoding a missense mutation (Fbn1C1039G/+), the most common class of mutation in MFS. Ascending and descending thoracic aorta reactivity was evaluated by wire myography. Ascending aorta mRNA and protein levels, and elastic fiber integrity were assessed by qRT-PCR, Western blotting, and Verhoeff-Van Gieson histological staining, respectively. MFS differently altered reactivity in the ascending and descending thoracic aorta by either increasing or decreasing phenylephrine contractions, respectively. When mice were separated by sex, contractions to phenylephrine increased progressively from 3 to 6 months of age in MFS ascending aortas of males, whereas contractions in females were unchanged. Endothelium-dependent relaxation was unaltered in the MFS ascending aorta of either sex; an effect related to augmented endothelium-dependent hyperpolarization-type dilations. In MFS males, the non-selective cyclooxygenase (COX) inhibitor indomethacin prevented the MFS-induced enhancement of phenylephrine contractions linked to increased COX-2 expression. In MFS mice of both sexes, the non-selective nitric oxide synthase inhibitor L-NAME revealed negative feedback of nitric oxide on phenylephrine contractions, which was associated with upregulation of eNOS in females. Finally, MFS ascending aortas showed a greater number of elastic fiber breaks than the wild-types, and males exhibited more breaks than females. These results show regional and sex differences in Fbn1C1039G/+ mice thoracic aorta contractility and aortic media injuries. The presence of more pronounced aortic alterations in male mice provides experimental evidence to support that male MFS patients are at increased risk of suffering aortic complications.
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Affiliation(s)
- Francesc Jiménez-Altayó
- Departament de Farmacologia, de Terapèutica i de Toxicologia, Institut de Neurociències, Facultat de Medicina, Universitat Autònoma de Barcelona, Bellaterra, Spain
| | - Anna-Maria Siegert
- Departament de Biomedicina, Facultat de Medicina i Ciències de la Salut, Universitat de Barcelona, Barcelona, Spain.,Institut d'Investigacions Biomèdiques August Pi i Sunyer, Barcelona, Spain
| | - Fabio Bonorino
- Departament de Biomedicina, Facultat de Medicina i Ciències de la Salut, Universitat de Barcelona, Barcelona, Spain
| | - Thayna Meirelles
- Departament de Biomedicina, Facultat de Medicina i Ciències de la Salut, Universitat de Barcelona, Barcelona, Spain
| | - Laura Barberà
- Departament de Biomedicina, Facultat de Medicina i Ciències de la Salut, Universitat de Barcelona, Barcelona, Spain
| | - Ana P Dantas
- Institut Clínic del Tòrax, Institut d'Investigacions Biomèdiques August Pi i Sunyer, Barcelona, Spain
| | - Elisabet Vila
- Departament de Farmacologia, de Terapèutica i de Toxicologia, Institut de Neurociències, Facultat de Medicina, Universitat Autònoma de Barcelona, Bellaterra, Spain
| | - Gustavo Egea
- Departament de Biomedicina, Facultat de Medicina i Ciències de la Salut, Universitat de Barcelona, Barcelona, Spain
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Gibson C, Nielsen C, Alex R, Cooper K, Farney M, Gaufin D, Cui JZ, van Breemen C, Broderick TL, Vallejo-Elias J, Esfandiarei M. Mild aerobic exercise blocks elastin fiber fragmentation and aortic dilatation in a mouse model of Marfan syndrome associated aortic aneurysm. J Appl Physiol (1985) 2017; 123:147-160. [PMID: 28385916 DOI: 10.1152/japplphysiol.00132.2017] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [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: 02/13/2017] [Revised: 03/29/2017] [Accepted: 04/03/2017] [Indexed: 11/22/2022] Open
Abstract
Regular low-impact physical activity is generally allowed in patients with Marfan syndrome, a connective tissue disorder caused by heterozygous mutations in the fibrillin-1 gene. However, being above average in height encourages young adults with this syndrome to engage in high-intensity contact sports, which unfortunately increases the risk for aortic aneurysm and rupture, the leading cause of death in Marfan syndrome. In this study, we investigated the effects of voluntary (cage-wheel) or forced (treadmill) aerobic exercise at different intensities on aortic function and structure in a mouse model of Marfan syndrome. Four-week-old Marfan and wild-type mice were subjected to voluntary and forced exercise regimens or sedentary lifestyle for 5 mo. Thoracic aortic tissue was isolated and subjected to structural and functional studies. Our data showed that exercise improved aortic wall structure and function in Marfan mice and that the beneficial effect was biphasic, with an optimum at low intensity exercise (55-65% V̇o2max) and tapering off at a higher intensity of exercise (85% V̇o2max). The mechanism underlying the reduced elastin fragmentation in Marfan mice involved reduction of the expression of matrix metalloproteinases 2 and 9 within the aortic wall. These findings present the first evidence of potential beneficial effects of mild exercise on the structural integrity of the aortic wall in Marfan syndrome associated aneurysm. Our finding that moderate, but not strenuous, exercise protects aortic structure and function in a mouse model of Marfan syndrome could have important implications for the medical care of young Marfan patients.NEW & NOTEWORTHY The present study provides conclusive scientific evidence that daily exercise can improve aortic health in a mouse model of Marfan syndrome associated aortic aneurysm, and it establishes the threshold for the exercise intensity beyond which exercise may not be as protective. These findings establish a platform for a new focus on promoting regular exercise in Marfan patients at an optimum intensity and create a paradigm shift in clinical care of Marfan patients suffering from aortic aneurysm complications.
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Affiliation(s)
| | - Cory Nielsen
- Department of Biomedical Sciences, College of Health Sciences
| | - Ramona Alex
- Department of Biomedical Sciences, College of Health Sciences
| | - Kimbal Cooper
- Department of Biomedical Sciences, College of Health Sciences
| | - Michael Farney
- Department of Biomedical Sciences, College of Health Sciences
| | - Douglas Gaufin
- Department of Biomedical Sciences, College of Health Sciences
| | - Jason Z Cui
- Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, British Columbia, Canada
| | - Cornelis van Breemen
- Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, British Columbia, Canada
| | - Tom L Broderick
- Department of Physiology, Arizona College of Osteopathic Medicine, Midwestern University, Glendale, Arizona; and
| | - Johana Vallejo-Elias
- Department of Physiology, Arizona College of Osteopathic Medicine, Midwestern University, Glendale, Arizona; and
| | - Mitra Esfandiarei
- Department of Biomedical Sciences, College of Health Sciences; .,Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, British Columbia, Canada
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Gotschy A, Bauer E, Schrodt C, Lykowsky G, Ye YX, Rommel E, Jakob PM, Bauer WR, Herold V. Local arterial stiffening assessed by MRI precedes atherosclerotic plaque formation. Circ Cardiovasc Imaging 2013; 6:916-23. [PMID: 24100044 DOI: 10.1161/circimaging.113.000611] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
BACKGROUND Atherosclerosis is known to impair vascular function and cause vascular stiffening. The aim of this study was to evaluate the potential predictive role of vascular stiffening in the early detection of atherosclerosis. Therefore, we investigated the time course of early functional and morphological alterations of the vessel wall in a murine atherosclerosis model. Because initial lesions are distributed inhomogeneously in early-stage atherosclerosis, MR microscopy was performed to measure vascular elasticity locally, specifically the local pulse wave velocity and the arterial wall thickness. METHODS AND RESULTS Local pulse wave velocity and the mean arterial wall thickness were determined in the ascending and the abdominal aortae of ApoE(-/-) and wild-type mice. In vivo MRI revealed that baseline pulse wave velocity and morphology were similar in 6-week-old ApoE(-/-) and WT mice, whereas at the age of 18 weeks, local pulse wave velocity was significantly elevated in ApoE(-/-) mice. Significantly increased vessel wall thickness was not found in ApoE(-/-) mice until the age of 30 weeks. Histological analysis of the aortae of ApoE(-/-) and WT mice showed that increased pulse wave velocity coincided with the fragmentation of the elastic laminae in the arterial wall, which is hypothesized to induce early vascular stiffening and may be promoted by macrophage-mediated matrix degradation. CONCLUSIONS We newly report that the assessment of local pulse wave velocity via MRI provides early information about the local progression of atherosclerosis before macroscopic alterations of the vessel wall occur.
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Affiliation(s)
- Alexander Gotschy
- Department of Internal Medicine I, University Hospital Würzburg, Würzburg, Germany
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