Proportion Of Elastin Research Articles

Aortic Leaflet Stresses Are Substantially Lower Using Pulmonary Visceral Pleura Than Pericardial Tissue.

Background: Porcine heart and bovine pericardium valves, which are collagen-based with relatively little elastin, have been broadly utilized to construct bioprosthetic heart valves (BHVs). With a larger proportion of elastin, the pulmonary visceral pleura (PVP) has greater elasticity and could potentially serve as an advantageous biomaterial for the construction/repair of BHVs. The question of how the aortic valve’s performance is affected by its bending rigidity has not been well studied. Methods: Based on the stress–strain relationships of the pericardium and PVP determined by planar uni-axial tests, a three-dimensional (3D) computational fluid–structure interaction (FSI) framework is employed to numerically investigate the aortic valve’s performance by considering three different cases with Young’s modulus as follows: , , and kPa, respectively. Results: The stroke volumes are 112, 99.6, and 91.4 ml as Young’s modulus increases from 375 to 750 and 1500 kPa, respectively. Peak geometric opening area (GOA) values are 2.3, 2.2, and 2.0 cm2 for , 750, and 1500 kPa, respectively. The maximum value of the aortic leaflet stress is about 271 kPa for kPa, and it increases to about 383 and 540 kPa for and 1500 kPa in the belly region at the peak systole, while it reduces from 550 kPa to 450 and 400 kPa for , 750, and 1500 kPa, respectively, at the instant of peak “water-hammer”. Conclusion: A more compliant PVP aortic leaflet valve with a smaller Young’s modulus, , has a higher cardiac output, larger GOA, and lower hemodynamic resistance. Most importantly, the aortic leaflet stresses are substantially lower in the belly region within the higher compliance PVP aortic valve tissue during the systole phase, even though some stress increase is also found during the fast-closing phase due to the “water-hammer” effect similar to that in the pericardial tissue. Future clinical studies will be conducted to test the hypothesis that the PVP-based valve leaflets with higher compliance will have lower fatigue or calcification rates due to the overall lower stress.

Pulmonary Visceral Pleura Biomaterial: Elastin- and Collagen-Based Extracellular Matrix.

Objective: The goal of the study is to determine the structural characteristics, mechanical properties, cytotoxicity, and biocompatibility of the pulmonary visceral pleura (PVP). Background: Collagen and elastin are the major components of the extracellular matrix. The PVP has an abundance of elastin and collagen that can serve as a potential biomaterial for clinical repair and reconstructions. Methods: The PVP was processed from swine and bovine lungs. Chemical analyses were used to determine collagen and elastin contents in the PVPs. Immunofluorescence microscopy was used to analyze the structure of the PVP. The stress–strain relationships and stress relaxation were determined by using the planar uniaxial test. The cytotoxicity of the PVP was tested in cultured cells. In in vivo evaluations, the PVP was implanted in the sciatic nerve and skin of rats. Results: Collagen and elastin contents are abundant in the PVP with larger proportions of elastin than in the bovine pericardium and porcine small intestinal submucosa. A microstructural analysis revealed that the elastin fibers were distributed throughout the PVP and the collagen was distributed mainly in the mesothelial basal lamina. The incremental moduli in stress–strain curves and relaxation moduli in the Maxwell–Wiechert model of PVP were approximately one-tenth of the bovine pericardium and small intestinal submucosa. The minimal cytotoxicity of the PVP was demonstrated. The axons proliferated in the PVP conduit guidance from proximal to distal sciatic nerves of rats. The neo-skin regenerated under the PVP skin substitute within 4 weeks. Conclusions: The PVP is composed of abundant collagen and elastin. The structural characteristics and mechanical compliance of the PVP render a suitable biological material for repair/reconstruction.

Spatiotemporal changes in mechanical matrisome components of the human ovary from prepuberty to menopause.

Spatiotemporal changes in mechanical matrisome components of the human ovary from prepuberty to menopause.

Collagenase mRNA Overexpression and Decreased Extracellular Matrix Components Are Early Events in the Pathogenesis of Emphysema.

To describe the progression of parenchymal remodeling and metalloproteinases gene expression in earlier stages of emphysema, mice received porcine pancreatic elastase (PPE) instillation and Control groups received saline solution. After PPE instillation (1, 3, 6 hours, 3 and 21 days) we measured the mean linear intercept, the volume proportion of types I and III collagen, elastin, fibrillin and the MMP-1, -8, -12 and -13 gene expression. We observed an initial decrease in type I (at the 3rd day) and type III collagen (from the 6th hour until the 3rd day), in posterior time points in which we detected increased gene expression for MMP-8 and -13 in PPE groups. After 21 days, the type III collagen fibers increased and the type I collagen values returned to similar values compared to control groups. The MMP-12 gene expression was increased in earlier times (3 and 6 hours) to which we detected a reduced proportion of elastin (3 days) in PPE groups, reinforcing the already established importance of MMP-12 in the breakdown of ECM. Such findings will be useful to better elucidate the alterations in ECM components and the importance of not only metalloelastase but also collagenases in earlier emphysema stages, providing new clues to novel therapeutic targets.

Porcine vena cava as an alternative to bovine pericardium in bioprosthetic percutaneous heart valves

Percutaneous heart valves are revolutionizing valve replacement surgery by offering a less invasive treatment option for high-risk patient populations who have previously been denied the traditional open chest procedure. Percutaneous valves need to be crimped to accommodate a small-diameter catheter during deployment, and they must then open to the size of heart valve. Thus the material used must be strong and possess elastic recoil for this application. Most percutaneous valves utilize bovine pericardium as a material of choice. One possible method to reduce the device delivery diameter is to utilize a thin, highly elastic tissue. Here we investigated porcine vena cava as an alternative to bovine pericardium for percutaneous valve application. We compared the structural, mechanical, and in vivo properties of porcine vena cava to those of bovine pericardium. While the extracellular matrix fibers of pericardium are randomly oriented, the vena cava contains highly aligned collagen and elastin fibers that impart strength to the vessel in the circumferential direction and elasticity in the longitudinal direction. Moreover, the vena cava contains a greater proportion of elastin, whereas the pericardium matrix is mainly composed of collagen. Due to its high elastin content, the vena cava is significantly less stiff than the pericardium, even after crosslinking with glutaraldehyde. Furthermore, the vena cava’s mechanical compliance is preserved after compression under forces similar to those exerted by a stent, whereas pericardium is significantly stiffened by this process. Bovine pericardium also showed surface cracks observed by scanning electron microscopy after crimping that were not seen in vena cava tissue. Additionally, the vena cava exhibited reduced calcification (46.64 ± 8.15 μg Ca/mg tissue) as compared to the pericardium (86.79 ± 10.34 μg/mg). These results suggest that the vena cava may provide enhanced leaflet flexibility, tissue resilience, and tissue integrity in percutaneous heart valves, ultimately reducing the device profile while improving the durability of these valves.

DOES ELASTIN CONTRIBUTE TO THE PERSISTENCE OF CORPORA ALBICANTIA IN THE OVARY OF THE COMMON DOLPHIN (DELPHINUS DELPHIS)

AbstractThe corpora albicantia (CAs) from the ovaries of 39 common dolphins (Delphinus delphis) caught in driving fisheries were used, and histologically and immunohistochemically examined. The area of each corpus albicans (CA) and the proportion of that area occupied by elastin were measured using NIH‐image software. In all CAs, elastoid material (EM) was apparent although EM area varied in each CA. CAs increased in number with dolphin age. Smaller CAs contained a higher proportion of EM. EM was completely digested by elastase, but not by collagenase. Furthermore, EM was immunostained with anti‐α‐elastin antibody. These results demonstrated that EM was elastin. The present study is the first to describe the presence of elastin in cetacean CAs. The higher proportion of elastin in small‐sized CAs of common dolphins is suggested as the likely cause of the persistence of CA.

Localization of Aortic Disease Is Associated with Intrinsic Differences in Aortic Structure

Purpose. While localization of atherosclerosis and aneurysms to the infrarenal aorta has been attributed, in part, to hemodynamic factors, anatomic differences between the proximal and the distal aorta may also be important. Our purpose was to determine the changes in content and organization of major structural proteins (elastin and collagen) throughout the normal human aorta. Methods . Biochemical analysis for desmosine-isodesmosine (elastin) and hydroxyproline (collagen) content was done by HPLC on complete 1-cm transverse rings removed from the ascending and descending thoracic aorta and abdominal supraceliac, suprarenal, and midinfrarenal aorta. Elastin and collagen content was normalized to lumenal surface area and compared by ANOVA. Light microscopy and optical micrometry were used to determine changes in intimal, medial, and adventitial thickness and number of elastin lamellae at each level. Results . Both collagen/cm 2 and elastin/cm 2 decrease from the proximal to distal aorta. Collagen content did not differ among the three abdominal segments, but there was a 58% decrease in elastin between the suprarenal and the infrarenal aorta. The proportion of elastin and collagen does not differ throughout the aorta except in the infrarenal aorta where there is decreased elastin relative to collagen. Conclusion. Collagen and elastin in the distal aorta hear an increased load as compared to the proximal aorta. The infrarenal aorta differs biochemically and histologically from the remainder of the aorta. A decrease in infrarenal elastin without a corresponding decrease in collagen may effect the compliance and integrity of the distal aorta. These anatomic differences may be important in predisposing the infrarenal aorta to atherosclerosis and aneurysm formation.

Smoke-induced emphysema in guinea pigs is associated with morphometric evidence of collagen breakdown and repair

We have previously shown that chronic cigarette smoke exposure produces emphysema and airflow obstruction in the guinea pig. To further examine the changes in the connective tissue matrix associated with emphysema in this model, we used ultrastructural morphometry to determine the volume proportions of collagen and elastin in the alveolar walls of animals exposed to smoke or air (control) for 1, 3, 6, and 12 mo. After 1 mo of smoke exposure, there was a statistically significant (P < 0.001) decrease in the volume proportion of collagen in the smoke-exposed animals, whereas by 6 and 12 mo of smoke exposure, the proportion of collagen had significantly (P < 0.02, P < 0.03, respectively) increased. The volume proportion of elastin was increased in the smoke-exposed animals at the 12-mo time period. While our results do not exclude reorganization of elastin within the alveolar wall, we conclude that, in this model, cigarette smoke-induced emphysema appears to be associated with collagen breakdown and repair. We suggest that the currently accepted proteolysis-antiproteolysis theory is too narrow in its focus on elastin destruction as the major contributor to emphysema and should be broadened to the concept that smoke-induced emphysema reflects breakdown and resynthesis (possibly overproduction in the form of scarring) of a variety of connective tissue proteins in addition to elastin.

Alterations in elastin and collagen related to the mechanism of progressive pulmonary venous obstruction in a piglet model. A hemodynamic, ultrastructural, and biochemical study.

We created an animal model to understand better the pathogenesis and underlying mechanism of progressive central pulmonary venous (PV) obstruction, a condition not amenable to current therapy. Twenty piglets underwent banding of their PVs, 18 had a sham operation, and 12 were nonoperated controls. After 1, 3, and 6 weeks hemodynamic data were obtained and correlated with ventricular weights, PV and pulmonary artery (PA) distensibilities (at 1 week), morphometric structural and ultrastructural analyses, and biochemical assessment of elastin determined gravimetrically (and by desmosine level at 1 week), collagen, and elastase activity. At 1 week, PV banding was associated with increased PV compliance (p less than 0.05). At 3 weeks, an increased PA pressure (Ppa) (p less than 0.05) was observed, unaccompanied by a rise in PV pressure (Pcw). In the PV, however, there was breakdown of the internal elastic lamina with apparent migration of smooth muscle cells from media to subendothelium. At 6 weeks, a rise in Pcw (p less than 0.01), a further rise in Ppa (p less than 0.01), and right ventricular hypertrophy (p less than 0.005) were observed. We also observed mild PV intimal thickening (p less than 0.01), complete degradation of elastic laminae (p less than 0.05), and an increase in collagen assessed morphometrically (p less than 0.01). The banding procedure resulted in an overall increase in PV elastin synthesis and in the proportion of elastin determined gravimetrically (p less than 0.05 for both) but not by desmosine level, suggesting the possibility of poor cross-linking of elastin, which might account for the early increased distensibility of the PV. However, our assay could not detect an increase in elastase activity associated with either the increased distensibility or the ultrastructural changes of elastin degradation. The increased Ppa was not associated with significant PA biochemical or structural changes. We speculate that in response to distal venous obstruction, early remodeling of the PVs increases distensibility, protecting the lung from venous congestion and blunting a rise in Pcw. PA hypertension precedes the rise in Pcw, likely because of reflex vasoconstriction. The subsequent modest rise in Pcw is already associated with extensive fibrosis of the PV, suggesting a reason for unsuccessful current therapy and a need for consideration of earlier assessment and intervention.

Structural composition of central pulmonary arteries: Growth potential after surgical shunts

Failure to achieve adequate pulmonary artery growth in patients with cyanotic congenital heart disease is a major obstacle to surgical correction. To assess whether differences in structural composition of central pulmonary arteries influence their growth potential after surgically created shunts, we obtained full-thickness biopsy specimens from the hilar pulmonary arteries of eight patients with pulmonary atresia or tetralogy of Fallot undergoing modified Blalock-Taussig shunts under 1 year of age. Tissue was processed for electron microscopic studies and a morphometric assessment was made of the volume proportions of smooth muscle, collagen, ground substance, and elastin. Initial pulmonary artery size was determined angiographically during the diagnostic cardiac catheterization. Pulmonary artery size was determined by cross-sectional echocardiograms 7 to 27 months later (mean 19 months). Pulmonary artery growth did not correlate with the interval between examinations but did correlate with the volume proportion of elastin (r = 0.73, standard error of the estimate = 1.45, p less than 0.05). Thus the structural composition of pulmonary arteries may influence their potential for growth after surgical shunts. In particular, an inadequate proportion of elastin may be a hindrance to growth.

Elastin content of normal and emphysematous lung parenchyma

Elastin destruction has been recognized as a crucial factor in the development of experimental pulmonary emphysema. However, no consistent alterations in lung elastin have as yet been demonstrated in human subjects with diffuse panacinar emphysema. In this study elastin content was measured in pulmonary parenchyma obtained by surgical biopsy and postmortem from eight patients with clinical, physiologic and morphologic criteria for panacinar emphysema, and postmortem from six normal adults. Concentrations of the elastin-specific amino acids, desmosine and isodesmosine, were determined both in the crude connective tissue of lung parenchyma and separately in elastin isolated by a modification of the Lansing method. Elastin proportions were then expressed as percent of lung parenchymal crude connective tissue. In lungs of six normal control subjects mean elastin was 30.5 percent standard deviation (SD) ± 3.69 (range 25.1 to 35.0 percent). In five patients the proportions of lung elastin were all below control: mean 12.1 percent SD ± 3.7 (range 9.0 to 17.5 percent). Three patients of this group had Pi phenotype MM; one had ZZ and one had MZ. In three additional patients (one with Pi MZ; two with Pi MM), all of whom had received glucocorticoid therapy (21 months to nine years), elastin proportions were similar to those observed in normal subjects: mean 36.8 percent SD ± 5.98 (range 31.7 to 43.4 percent). The amino acid composition of isolated elastin did not differ significantly between any of the groups. Results demonstrate reduced proportions of lung elastin in pulmonary emphysema except in patients treated with glucocorticoids which may decrease collagen synthesis and increase the relative proportions of elastin.

Effect of papain-induced emphysema on canine pulmonary elastin.

AbstractExperimental emphysema was induced in eight beagles by repeated administration of crude papain via aerosol and intratracheal instillation. Significant increases in mean linear intercept in the lungs of the papain treated dogs were consistent with morphological evidence of ruptured alveolar septa. The proportions of elastin in the parenchymal connective tissue were calculated from the desmosine and isodesmosine content of the total connective tissue and of purified elastin from the same specimens. Mean pulmonary elastin proportions determined 2 weeks after the last dose of papain in four dogs with experimental emphysema were only 4.52% ± 1.84 whereas mean pulmonary elastin proportions in four control dogs were 14.42% ± 3.55. In two dogs sacrificed 3 months after the termination of the insult, mean pulmonary elastin proportions were not significantly different from those in the control dogs. Since the elastolytic activity of papain is very low these data suggest that the elastin may be degraded in v...

The role of the fibrous components and ground substance in the mechanical properties of biological tissues: A preliminary investigation

Stress-strain and relaxation tests were conducted on human tendon, aorta and bovine ligamentum nuchae which have different arrangements and proportions of elastin, collagen and ground substance. The removal of the ground substance with an enzyme or a chelating agent induced a decrease in stress level, stiffness, relaxation, hysteresis and other time-dependent effects in all three tissues. These changes could be largely explained by a reduction in the effective viscosity of the interfibre matrix although some other factor seemed to be present in the case of tendon, possibly a change in the relationship between the collagen fibres and the glycoproteins in the matrix. Treating aorta and nuchal ligament with formic acid to remove collagen and other material produced a marked decrease in stress level and time-dependence and also a decrease in the stress and strain at rupture which may be due to the removal of collagen that normally prevents premature rupture at weak points in the elastic network.

The collagen and elastin content of the arterial wall in the dog.

A survey has been made in adult dogs of the collagen and elastin content of the walls of arteries varying in size from the thoracic aorta to the saphenous artery. In all arteries, except the smallest, collagen and elastin together formed about 50% of the dry weight. In the smallest the proportion was somewhat higher. On the basis of relative proportions of elastin and collagen the systemic arterial tree was found to be divided rather sharply into two regions: in the intrathoracic aorta there was about twice as much elastin as collagen in the wall; in all other vessels the relation was reversed, there being about twice as much collagen as elastin. The transition between the more elastic intrathoracic aorta and the more collagenous extrathoracic vessels was abrupt and took place over a distance of only 5 cm or so. The pulmonary artery resembled the extrathoracic vessels rather than the thoracic aorta in ratio of elastin to collagen. Newborn and young puppies showed a similar difference to adults between thoracic and abdominal aorta, although we did not investigate the relation between the two vessels in detail.