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Weitzel WF, Kim K, Rubin JM, Xie H, O'Donnell M. Renal advances in ultrasound elasticity imaging: measuring the compliance of arteries and kidneys in end-stage renal disease. Blood Purif 2005; 23:10-7. [PMID: 15627731 DOI: 10.1159/000082005] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
BACKGROUND/AIMS Ultrasound elasticity imaging visually represents tissue hardness measurements using high-resolution ultrasound speckle-tracking algorithms. This method has recently been applied in the renal setting to measure arterial compliance in end-stage renal disease (ESRD) and the mechanical properties of transplant kidneys in vivo. METHODS Ultrasound radio-frequency signal measurements were made of the brachial artery in 5 ESRD subjects and 5 healthy controls and renal transplant measurements in 2 subjects, 1 with chronic allograft nephropathy (CAN) and 1 with normal graft function. RESULTS Maximal brachial artery percent strain measurements for healthy controls were 32.9 +/- 10.2% (mean +/- SD) and for ESRD subjects maximal percent strains were 4.9 +/- 1.8%. Transplant renal cortical strain for the subject with CAN was approximately one third that of the healthy transplant recipient. CONCLUSION Ultrasound elasticity imaging offers the potential to noninvasively measure the mechanical properties of structures within the body.
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Affiliation(s)
- W F Weitzel
- Department of Internal Medicine, University of Michigan, Ann Arbor, MI, USA.
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102
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Wei HJ, Liang HC, Lee MH, Huang YC, Chang Y, Sung HW. Construction of varying porous structures in acellular bovine pericardia as a tissue-engineering extracellular matrix. Biomaterials 2005; 26:1905-13. [PMID: 15576164 DOI: 10.1016/j.biomaterials.2004.06.014] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2004] [Accepted: 06/14/2004] [Indexed: 10/26/2022]
Abstract
In the study, a cell extraction process was used to remove the cellular components from bovine pericardia. Varying pore sizes and porosities of the acellular tissues were then created using acetic acid and collagenase and subsequently fixed with genipin. Biochemical analyses found that these acellular tissues with distinct porous structures consisted primarily of insoluble collagen, elastin, and tightly bound glycosaminoglycans. The thermal stability, mechanical properties, and capability against enzymatic degradation of the bovine pericardial tissue remained unaltered after cell extraction. However, following further treatment with acetic acid and collagenase, the thermal stability and capability against enzymatic degradation of the acellular tissues declined. The porous structures of the implanted samples seem to determine whether successful microvessel-ingrowth takes place. The acetic-acid- and collagenase-treated tissues, due to their high pore size and porosity, showed a large number of microvessels infiltrating into the interstices of the implanted samples. In contrast, a low density of microvessels was observed infiltrating into the acellular tissue and penetration of microvessels into the cellular tissue was never encountered.
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Affiliation(s)
- Hao-Ji Wei
- Division of Cardiovascular Surgery, Veterans General Hospital-Taichung, and College of Medicine, National Yang-Ming University, Taipei, Taiwan, ROC
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103
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Bouzeghrane F, Reinhardt DP, Reudelhuber TL, Thibault G. Enhanced expression of fibrillin-1, a constituent of the myocardial extracellular matrix in fibrosis. Am J Physiol Heart Circ Physiol 2005; 289:H982-91. [PMID: 15849235 DOI: 10.1152/ajpheart.00151.2005] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Fibrillin-1 localization in the myocardium and the modulation of its expression in cardiac fibrosis were examined. In normal rat hearts, fibrillin-1 was abundant throughout the myocardium as thin fibers that crossed over the perimysium and around arteries. After cardiac fibrosis was induced in rats by either 14-day ANG II infusion or 21-day DOCA-salt treatment [a high endothelin-1 (ET-1) model], fibrillin-1 immunostaining was stronger in the interstitium (2.8-fold and 4.4-fold increases, respectively, in each model), extended between myocytes, and accumulated in microscopic scars and in the perivascular area of both ventricles. mRNA analysis confirmed its enhanced ventricular expression in both groups of rats (2.5-fold and 6.6-fold increments, respectively, in each model). In 1B normotensive and 2C hypertensive transgenic mice, two lines expressing an ANG II fusion protein in cardiac myocytes, strong fibrillin-1 immunoreactivity was observed in the interstitium and around arteries (3.7-fold and 7-fold increases, respectively). ANG II and transforming growth factor-beta1 enhanced fibrillin-1 synthesis by cardiac fibroblasts. Some fibrillin-1 fragments interacted with RGD-dependent integrins, including alpha(8)beta(1)-integrin, of cardiac fibroblasts but not necessarily through the RGD motif. Our findings illustrate that fibrillin-1 is an important constituent of the myocardium. In vitro and in vivo evidence suggests that ANG II can directly induce fibrillin-1 expression in cardiac fibroblasts. This protein can thus contribute to reactive and reparative processes.
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Affiliation(s)
- Fatiha Bouzeghrane
- Institut de Recherches Cliniques de Montréal, Montréal, Québec, Canada H2W 1R7
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104
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Abstract
Elastin is a key extracellular matrix protein that is critical to the elasticity and resilience of many vertebrate tissues including large arteries, lung, ligament, tendon, skin, and elastic cartilage. Tropoelastin associates with multiple tropoelastin molecules during the major phase of elastogenesis through coacervation, where this process is directed by the precise patterning of mostly alternating hydrophobic and hydrophilic sequences that dictate intermolecular alignment. Massively crosslinked arrays of tropoelastin (typically in association with microfibrils) contribute to tissue structural integrity and biomechanics through persistent flexibility, allowing for repeated stretch and relaxation cycles that critically depend on hydrated environments. Elastin sequences interact with multiple proteins found in or colocalized with microfibrils, and bind to elastogenic cell surface receptors. Knowledge of the major stages in elastin assembly has facilitated the construction of in vitro models of elastogenesis, leading to the identification of precise molecular regions that are critical to elastin-based protein interactions.
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Affiliation(s)
- Suzanne M Mithieux
- School of Molecular and Microbial Biosciences, University of Sydney, New South Wales 2006, Australia
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105
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Zieman SJ, Kass DA. Advanced glycation endproduct crosslinking in the cardiovascular system: potential therapeutic target for cardiovascular disease. Drugs 2004; 64:459-70. [PMID: 14977384 DOI: 10.2165/00003495-200464050-00001] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Advanced glycation endproducts (AGEs) are formed by a reaction between reducing sugars and biological amines. Because of their marked stability, glycated proteins accumulate slowly over a person's lifespan, and can contribute to age-associated structural and physiological changes in the cardiovascular system such as increased vascular and myocardial stiffness, endothelial dysfunction, altered vascular injury responses and atherosclerotic plaque formation. The mechanisms by which AGEs affect the cardiovascular system include collagen crosslinking, alteration of low-density lipoprotein molecules and impairment of cellular nitric oxide signalling through their interaction with AGE receptors (RAGEs). Thus, the accumulation of AGEs may help to explain the increased cardiac risk associated with aging as well as diabetes mellitus and hypertension, two conditions that accelerate and enhance AGE formation. A variety of new pharmacological approaches are being developed to reduce the pathophysiological impact of AGEs. These agents can prevent AGE and AGE crosslink formation, break pre-existing AGE crosslinks, and block the interaction between AGEs and RAGEs. Such agents have been shown to reduce vascular and myocardial stiffness, inhibit atherosclerotic plaque formation and improve endothelial function in animal models. Improvement in vascular compliance has also been demonstrated with AGE crosslink breakers in clinical trials. These studies offer promise to reduce the cardiac risk associated with isolated systolic hypertension, diastolic dysfunction and diabetes.
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Affiliation(s)
- Susan J Zieman
- Division of Cardiology, Johns Hopkins Medical Institutions, Baltimore, Maryland 21287, USA.
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106
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Ramirez F, Dietz HC. Therapy Insight: aortic aneurysm and dissection in Marfan's syndrome. ACTA ACUST UNITED AC 2004; 1:31-6. [PMID: 16265257 DOI: 10.1038/ncpcardio0020] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2004] [Accepted: 09/09/2004] [Indexed: 11/09/2022]
Abstract
Aortic dissection and aneurysm are common clinical problems with life-threatening consequences; they are also the hallmark of several genetic diseases, including Marfan's syndrome (MFS). In spite of clinical and surgical advances that have increased life expectancy for affected patients, cardiovascular manifestations remain significant contributors to morbidity and mortality in MFS. Dissecting aortic aneurysm in this disorder is accounted for by mutations in fibrillin-1, the major component of the microfibrils associated with elastin in the elastic fibers of the aortic media. Genetic studies of human patients and murine models have yielded invaluable insights into the pathophysiology of aneurysm formation and progression in MFS. They have also revealed a previously unappreciated role of microfibrils in regulating transforming growth factor and bone morphogenetic protein signaling. As a result, exciting new hypotheses have emerged regarding the pathogenesis of MFS, as well as opportunities to explore translational applications of this information that may be relevant to various manifestations of the disease.
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Affiliation(s)
- Francesco Ramirez
- Laboratory of Genetics and Organogenesis, Hospital for Special Surgery at the Weill Medical College of Cornell University, 535 East 70th Street, New York, NY 10021, USA.
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107
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Kim K, Weitzel WF, Rubin JM, Xie H, Chen X, O'Donnell M. Vascular intramural strain imaging using arterial pressure equalization. ULTRASOUND IN MEDICINE & BIOLOGY 2004; 30:761-771. [PMID: 15219956 DOI: 10.1016/j.ultrasmedbio.2004.04.003] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2003] [Revised: 04/08/2004] [Accepted: 04/15/2004] [Indexed: 05/24/2023]
Abstract
Peripheral vascular strain imaging has limited strain dynamic range because arterial wall deformations only exhibit small strains under physiologic pressures. A noninvasive freehand ultrasound (US) scanning procedure was performed to apply external force, comparable to the force generated in measuring a subject's blood pressure, to achieve higher strains by equalizing the internal arterial baseline pressure. When the applied pressure matched the internal baseline diastolic pressure, intramural strain and strain rate increased by a factor of 10 over a cardiac cycle. Radial arterial strain was assessed within the vessel wall over the entire deformation procedure using a phase-sensitive 2-D speckle-tracking algorithm. The feasibility of this technique to assess vascular nonlinear elastic properties is demonstrated in an ex vivo experiment and further supported by in vivo measurements. With some uncertainty associated with the elastic properties of surrounding tissue, an elastic modulus reconstruction procedure was developed to estimate the nonlinear elastic properties of the vascular wall.
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Affiliation(s)
- Kang Kim
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, 48109-2099, USA.
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108
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Abstract
Knowledge of blood vessel mechanical properties is fundamental to the understanding of vascular function in health and disease. Analytic results can help physicians in the clinic, both in designing and in choosing appropriate therapies. Understanding the mechanical response of blood vessels to physiologic loads is necessary before ideal therapeutic solutions can be realized. For this reason, blood vessel constitutive models are needed. This article provides a critical review of recent blood vessel constitutive models, starting with a brief overview of the structure and function of arteries and veins, followed by a discussion of experimental techniques used in the characterization of material properties. Current models are classified by type, including pseudoelastic, randomly elastic, poroelastic, and viscoelastic. Comparisons are presented between the various models and existing experimental data. Applications of blood vessel constitutive models are also briefly presented, followed by the identification of future directions in research.
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Affiliation(s)
- Raymond P Vito
- Woodruff School of Mechanical Engineering, Atlanta, Georgia 30332-0405, USA.
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109
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Chang Y, Liang HC, Wei HJ, Chu CP, Sung HW. Tissue regeneration patterns in acellular bovine pericardia implanted in a canine model as a vascular patch. ACTA ACUST UNITED AC 2004; 69:323-33. [PMID: 15058005 DOI: 10.1002/jbm.a.30003] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
It was noted in our previous study that acellular tissues can provide a natural microenvironment for host cell migration and proliferation to accelerate tissue regeneration. The purpose of this study was to further investigate the tissue regeneration patterns in acellular bovine pericardia fixed with glutaraldehyde or genipin as a biological patch to repair a defect in the pulmonary trunk in a canine model. The implanted samples were retrieved at distinct durations postoperatively. The structural remodeling of retrieved samples was then examined. It was found that the degree of inflammatory reaction observed for the genipin-fixed acellular patch was significantly less than its glutaraldehyde-fixed counterpart. At 1 month postoperatively, intimal thickening was found on the inner surfaces of both studied groups. The intimal thickening observed on the glutaraldehyde-fixed acellular patch was significantly thicker than its genipin-fixed counterpart. An intact layer of endothelial cells was found on the intimal thickening of the genipin-fixed acellular patch, whereas endothelial cells did not universally and totally cover the entire surface of the glutaraldehyde-fixed acellular patch. Additionally, fibroblasts with neocollagen fibrils and myofibroblasts were observed in the acellular patches for both studied groups, an indication of tissue regeneration. This phenomenon was more prominent for the genipin-fixed acellular patch than its glutaraldehyde-fixed counterpart. At 6 months postoperatively, foci of chondroid and/or bony metaplasia were found in each retrieved sample for both studied groups. The observed adverse response of chondroid metaplasia may be attributed to a compliance mismatch at the implanted site of the canine pulmonary trunk after implantation or a lack of angiogenesis in the regenerated tissue observed at 1 month postoperatively. Bony metaplasia may then develop as in other chondroid tissues. It was reported that ischemia is a usual cause of metaplasia.
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Affiliation(s)
- Yen Chang
- Division of Cardiovascular Surgery, Veterans General Hospital-Taichung, Taiwan, Republic of China
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110
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Sherratt MJ, Baldock C, Haston JL, Holmes DF, Jones CJP, Shuttleworth CA, Wess TJ, Kielty CM. Fibrillin microfibrils are stiff reinforcing fibres in compliant tissues. J Mol Biol 2003; 332:183-93. [PMID: 12946356 DOI: 10.1016/s0022-2836(03)00829-5] [Citation(s) in RCA: 115] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Fibrillin-rich microfibrils have endowed tissues with elasticity throughout multicellular evolution. We have used molecular combing techniques to determine Young's modulus for individual microfibrils and X-ray diffraction of zonular filaments of the eye to establish the linearity of microfibril periodic extension. Microfibril periodicity is not altered at physiological zonular tissue extensions and Young's modulus is between 78 MPa and 96 MPa, which is two orders of magnitude stiffer than elastin. We conclude that elasticity in microfibril-containing tissues arises primarily from reversible alterations in supra-microfibrillar arrangements rather than from intrinsic elastic properties of individual microfibrils which, instead, act as reinforcing fibres in fibrous composite tissues.
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Affiliation(s)
- Michael J Sherratt
- Wellcome Trust Centre for Cell-Matrix Research, School of Biological Sciences, University of Manchester, 2.205 Stopford Building, Manchester M13 9PT, UK.
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111
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Cheng KS, Tiwari A, Boutin A, Denton CP, Black CM, Morris R, Seifalian AM, Hamilton G. Differentiation of primary and secondary Raynaud's disease by carotid arterial stiffness. Eur J Vasc Endovasc Surg 2003; 25:336-41. [PMID: 12651172 DOI: 10.1053/ejvs.2002.1845] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
INTRODUCTION primary Raynaud's disease may be difficult to differentiate clinically from the secondary form with an underlying connective tissue, haematological, neurovascular or drug-induced disorder. We undertook a study to determine the elastic carotid and muscular femoral arterial biomechanical properties and intima-media thickness (IMT) in subjects with primary and secondary Raynaud's disease, to assess whether these parameters could differentiate the two conditions. METHODS twenty patients with primary Raynaud's disease and 53 subjects with secondary Raynaud's associated with scleroderma (systemic sclerosis, SSc) had measurements of their carotid and femoral wall mechanics with a duplex scanner coupled to a Wall Track system. Their age, gender, body mass index, heart rate, systolic and diastolic blood pressures, presumed cardiovascular load, plasma creatinine, fasting cholesterol, triglyceride and glucose concentrations were also measured. RESULTS the carotid elastic properties [mean (SD): elastic modulus: 560 (180) vs 1204 (558) mmHg,p <0.001 and stiffness index: 5.69 (1.35) vs 11.92 (6.4), p<0.001 for primary and secondary Raynaud's respectively] were significantly impaired in patients with secondary Raynaud's disease even after adjustment for potentially influencing physiological and biochemical variables. There were no statistical differences in the femoral elastic properties or the carotid and femoral IMTs between the two groups. CONCLUSION Duplex determination of the carotid elasticity or stiffness is different in primary Raynaud's phenomenon compared with secondary Raynaud's associated with SSc. This may be a useful non-invasive tool, in addition to autoantibody markers and nail-fold capillaroscopy, to differentiate between the two forms of Raynaud's phenomenon.
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Affiliation(s)
- K-S Cheng
- University Department of Primary Care and Population Sciences, Royal Free and University College Medical School, University College London and The Royal Free Hospital, London, NW3 2QG, UK
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112
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Abstract
Elastic fibres are essential extracellular matrix macromolecules comprising an elastin core surrounded by a mantle of fibrillin-rich microfibrils. They endow connective tissues such as blood vessels, lungs and skin with the critical properties of elasticity and resilience. The biology of elastic fibres is complex because they have multiple components, a tightly regulated developmental deposition, a multi-step hierarchical assembly and unique biomechanical functions. However, their molecular complexity is at last being unravelled by progress in identifying interactions between component molecules, ultrastructural analyses and studies of informative mouse models.
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Affiliation(s)
- Cay M Kielty
- School of Medicine, University of Manchester, UK.
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113
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Abstract
"Somatic" angiotensin I-converting enzyme (ACE) appears to be one of the evolutionary advances that made a closed circulation possible, and may have contributed to the Cambrian "explosion" of species approximately 540 million years ago. It also appears to be at the origin of a large number of common human diseases. A model is proposed in which the duplicated form of ACE ("somatic" ACE) functions as a mechanotransducer, defending downstream vessels and tissues from an increase in pressure. In the model, ACE senses shear stress (blood velocity) in regions of turbulent blood flow. An increase in shear stress strips an autoinhibitor tripeptide, FQP, from the N-terminal active site, thereby activating it. The C-terminal domain is constitutively activated by chloride. This model explains the clinical superiority of hydrophobic ACE inhibitors relative to hydrophilic ones.
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