Structure Of Elastin Research Articles

Unravelling the mechanics of gastric tissue: A comparison of constitutive models, damage probability and microstructural insights

With the increasing prevalence of obesity worldwide, bariatric surgery is becoming increasingly common. However, the mechanic of the gastric wall related to bariatric surgery complications remains to be investigated. This study aims to understand mechanical behaviour of stomach by developing advanced material laws for gastric tissue incorporating microstructure. A multi-scale characterisation of the porcine stomach wall was performed in the fundus and corpus anatomical regions and in circumferential and longitudinal orientations The protocol included uniaxial tensile testing until damage, survival analysis to provide damage probability, comparison of phenomenological (Fung and Ogden order 1, 2 and 3) and structural (Holzapfel fibre-reinforced) computational models fitted to the experimental data, and quantitative analysis of elastin and collagen fibre structure from histological slides. All constitutive models fitted the experimental data well (r2 > 0.988 and RSME<3.8 kPa). Longitudinal and circumferential elastic modulus in quasi linear phase were respectively 1.75 ± 1.2 MPa, 0.76 ± 0.35 MPa for fundus, and 2.30 ± 0.66 MPa, 1.36 ± 0.89 MPa for corpus, highlighting significant differences between orientations in fundus and corpus, with an overall softer fundus in the circumferential direction. Microstructure analysis illustrated collagen and elastin fibre orientation, dispersion and density. As microstructure appears to play an important role in stomach biomechanics, model incorporating fibre structure such as Holzapfel fibre-reinforced model, seem best suited to describe the material behaviour of the stomach wall. Future research should complement these findings with an expanded sample set in human models.

Abstract 2040: Rapamycin Extends Life Of Matrix Gla Protein Knockout Mice Independent Of Vascular Calcification Content.

Background: Peripheral artery disease (PAD) is characterized by the narrowing and blockage of the vessels in lower extremities. While atherosclerosis has been the assumed culprit of PAD recent data now shows that medial arterial calcification (MAC) is the cause of below-the knee ischemia. MAC promotes thrombosis via inward remodeling, reduced elasticity, and arterial stiffness. The mechanisms driving MAC pathogenesis are unclear. Matrix Gla Protein (MGP) is an inhibitor of vascular calcification and present in arterial vessel walls. MGP -/- mice exhibit extensive MAC throughout their vasculature and die within 5-7 weeks due to aortic rupture or heart failure. The drug rapamycin functions as an inhibitor of cell proliferation and an activator of autophagy. Hypothesis: That rapamycin reduces MAC in MGP -/- mice via inhibiting inward remodeling and activating autophagy. Methods: MGP +/+ and MGP -/- mice treated with vehicle or rapamycin (5mg/kg, 3x weekly) starting at 10 days old for 2 weeks. Calcification was quantified via micro-computed tomography (uCT). Collagen structure and elastin quality were assessed histological staining. Markers of proliferation (Ki-67), cell death (Caspase 3), autophagy (LC3), and calcification (Runx2) were quantified via immunofluorescence staining. Western blot was used to assess autophagy flux and proliferation in smooth muscle cells (SMCs) isolated from MGP +/+ and MGP -/- mice. Results: While rapamycin treatment doubled the life-expectancy of MGP -/- mice, the calcification content was unchanged compared to the vehicle. However, rapamycin caused a significant decline in mineral density. Higher collagen content and improved elastin structure were observed in MGP -/- treated with rapamycin compared to vehicle. Runx2 and Ki-67 were elevated in MGP -/- mice compared to MGP +/+ , but there was no difference in response to rapamycin treatment. No difference was observed in caspase 3 levels. Under rapamycin treatment, MGP -/- SMCs exhibited higher autophagy flux than MGP +/+ SMCs. Conclusion: While rapamycin did not reduce MAC, our data suggest that rapamycin potentially preserves the integrity of the aortic vessel wall by inducing autophagy, which requires further investigation.

Structural and physical basis for the elasticity of elastin.

Elastin function is to endow vertebrate tissues with elasticity so that they can adapt to local mechanical constraints. The hydrophobicity and insolubility of the mature elastin polymer have hampered studies of its molecular organisation and structure-elasticity relationships. Nevertheless, a growing number of studies from a broad range of disciplines have provided invaluable insights, and several structural models of elastin have been proposed. However, many questions remain regarding how the primary sequence of elastin (and the soluble precursor tropoelastin) governs the molecular structure, its organisation into a polymeric network, and the mechanical properties of the resulting material. The elasticity of elastin is known to be largely entropic in origin, a property that is understood to arise from both its disordered molecular structure and its hydrophobic character. Despite a high degree of hydrophobicity, elastin does not form compact, water-excluding domains and remains highly disordered. However, elastin contains both stable and labile secondary structure elements. Current models of elastin structure and function are drawn from data collected on tropoelastin and on elastin-like peptides (ELPs) but at the tissue level, elasticity is only achieved after polymerisation of the mature elastin. In tissues, the reticulation of tropoelastin chains in water defines the polymer elastin that bears elasticity. Similarly, ELPs require polymerisation to become elastic. There is considerable interest in elastin especially in the biomaterials and cosmetic fields where ELPs are widely used. This review aims to provide an up-to-date survey of/perspective on current knowledge about the interplay between elastin structure, solvation, and entropic elasticity.

Photochemical Modification of the Extracellular Matrix to Alter the Vascular Remodeling Process.

Therapeutic interventions for vascular diseases aim at achieving long-term patency by controlling vascular remodeling. The extracellular matrix (ECM) of the vessel wall plays a crucial role in regulating this process. This study introduces a novel photochemical treatment known as Natural Vascular Scaffolding, utilizing a 4-amino substituted 1,8-naphthimide (10-8-10 Dimer) and 450 nm light. This treatment induces structural changes in the ECM by forming covalent bonds between amino acids in ECM fibers without harming vascular cell survival, as evidenced by our results. To further investigate the mechanism of this treatment, porcine carotid artery segments were exposed to 10-8-10 Dimer and light activation. Subsequent experiments subjected these segments to enzymatic degradation through elastase or collagenase treatment and were analyzed using digital image analysis software (MIPAR) after histological processing. The results demonstrated significant preservation of collagen and elastin structures in the photochemically treated vascular wall, compared to controls. This suggests that photochemical treatment can effectively modulate vascular remodeling by enhancing the resistance of the ECM scaffold to degradation. This approach shows promise in scenarios where vascular segments experience significant hemodynamic fluctuations as it reinforces vascular wall integrity and preserves lumen patency. This can be valuable in treating veins prior to fistula creation and grafting or managing arterial aneurysm expansion.

Synthesis of Ser-Ala-Ala Cyclic Desmosine

AbstractElastin is present in the extracellular matrix of various tissues, most abundantly in the aorta and major vascular vessels, and is formed by self-assembly followed by concomitant crosslinkers of tropoelastin, an elastin precursor. Desmosine is a pyridinium-based tetrafunctional amino acid that serves as an important crosslinker to bind the polymeric chains of peptides in the 3D network of elastin. Despite its significance, the detailed structure of elastin has not been elucidated. In this work, the synthesis of a cyclic desmosine peptide designed to mimic elastin, which could serve as a compound for mass spectrometric analysis to elucidate crosslinking structures is reported. The synthesis involved stepwise and regioselective palladium-catalyzed cross-couplings, and inter- and intramolecular condensations.

Association of NOTCH3 With Elastic Fiber Dispersion in the Infrarenal Abdominal Aorta of Cynomolgus Monkeys.

The regional heterogeneity of vascular components and transcriptomes is an important determinant of aortic biology. This notion has been explored in multiple mouse studies. In the present study, we examined the regional heterogeneity of aortas in nonhuman primates. Aortic samples were harvested from the ascending, descending thoracic, suprarenal, and infrarenal regions of young control monkeys and adult monkeys with high fructose consumption for 3 years. The regional heterogeneity of aortic structure and transcriptomes was examined by histological and bulk RNA sequencing analyses, respectively. Immunostaining of CD31 and αSMA (alpha-smooth muscle actin) revealed that endothelial and smooth muscle cells were distributed homogeneously across the aortic regions. In contrast, elastic fibers were less abundant and dispersed in the infrarenal aorta compared with other regions and associated with collagen deposition. Bulk RNA sequencing identified a distinct transcriptome related to the Notch signaling pathway in the infrarenal aorta with significantly increased NOTCH3 mRNA compared with other regions. Immunostaining revealed that NOTCH3 protein was increased in the media of the infrarenal aorta. The abundance of medial NOTCH3 was positively correlated with the dispersion of elastic fibers. Adult cynomolgus monkeys with high fructose consumption displayed vascular wall remodeling, such as smooth muscle cell loss and elastic fiber disruption, predominantly in the infrarenal region. The correlation between NOTCH3 and elastic fiber dispersion was enhanced in these monkeys. Aortas of young cynomolgus monkeys display regional heterogeneity of their transcriptome and the structure of elastin and collagens. Elastic fibers in the infrarenal aorta are dispersed along with upregulation of medial NOTCH3.

Effects of Investigational Moisturizers on the Skin Barrier and Microbiome following Exposure to Environmental Aggressors: A Randomized Clinical Trial and Ex Vivo Analysis.

The skin microbiota barrier participates in skin barrier function in addition to the physical, chemical, and immunological protective barriers, and is affected by environmental aggressors and skincare regimens. To better understand the exact effects of real-life environmental conditions on the skin and determine the protective methods, this study investigates the effects of three topical cosmetic moisturizers (water gel moisturizers with/without yeast extract (Moisturizers K and C) and a thick-emulsion cream moisturizer (Moisturizer L)) on clinical and skin microbiome endpoints in the presence of environmental aggressors during an 8-week, randomized controlled, triple-blind clinical trial with 110 participants, and molecular- as well as biomarker-level endpoints on ex vivo skin explants after exposure to simulate urban environmental conditions. The results show that all moisturizers are well-tolerated and improve skin barrier function and surface moisture content from the baseline, and the improvement is maintained at the last analysis point (3 days after trial completion). Compared with the untreated control areas (samples taken from the upper chest), treatment with Moisturizer K prevented a reduction in bacterial and fungal richness, and increased the change ratio of the relative abundance of commensal bacteria, such as Staphylococcus epidermidis and Ralstonia, at the treated sites (samples taken from the forehead). Moreover, Moisturizer K-treated ex vivo skin explants had higher levels of caspase 14 (a marker of skin barrier function), collagen I, and elastin (structure components), and lower levels of aryl hydrocarbon receptor (AHR; activated by air pollutants) and interleukin-6 (IL-6) than those in explants treated with other moisturizers and in the untreated areas of the skin. These results suggest that a skin postbiotic moisturizer with yeast extract supports the regulation of the skin's microbiome balance and may provide a holistic barrier (involving skin microbiome, physical, chemical, and immune barriers) to protect the skin against environmental aggressors.

Contribution of Elastic and Collagen Fibers to the Mechanical Behavior of Bovine Nuchal Ligament.

Ligamentum nuchae is a highly elastic tissue commonly used to study the structure and mechanics of elastin. This study combines imaging, mechanical testing, and constitutive modeling to examine the structural organization of elastic and collagen fibers and their contributions to the nonlinear stress-strain behavior of the tissue. Rectangular samples of bovine ligamentum nuchae cut in both longitudinal and transverse directions were tested in uniaxial tension. Purified elastin samples were also obtained and tested. It was observed that the stress-stretch response of purified elastin tissue follows a similar curve as the intact tissue initially, but the intact tissue shows a significant stiffening behavior for stretches above 1.29 with collagen engagement. Multiphoton and histology images confirm the elastin-dominated bulk of ligamentum nuchae interspersed with small bundles of collagen fibrils and sporadic collagen-rich regions with cellular components and ground substance. A transversely isotropic constitutive model that considers the longitudinal organization of elastic and collagen fibers was developed to describe the mechanical behavior of both intact and purified elastin tissue under uniaxial tension. These findings shed light on the unique structural and mechanical roles of elastic and collagen fibers in tissue mechanics and may aid in future use of ligamentum nuchae in tissue grafting.

Changes in elastin structure and extensibility induced by hypercalcemia and hyperglycemia.

Elastin is a key elastomeric protein responsible for the elasticity of many organs, including heart, skin, and blood vessels. Due to its intrinsic long life and low turnover rate, damage in elastin induced by pathophysiological conditions, such as hypercalcemia and hyperglycemia, accumulates during biological aging and in aging-associated diseases, such as diabetes mellitus and atherosclerosis. Prior studies have shown that calcification induced by hypercalcemia deteriorates the function of aortic tissues. Glycation of elastin is triggered by hyperglycemia and associated with elastic tissue damage and loss of mechanical functions via the accumulation of advanced glycation end products. To evaluate the effects on elastin's structural conformations and elasticity by hypercalcemia and hyperglycemia at the molecular scale, we perform classical atomistic and steered molecular dynamics simulations on tropoelastin, the soluble precursor of elastin, under different conditions. We characterize the interaction sites of glucose and calcium and associated structural conformational changes. Additionally, we find that elevated levels of calcium ions and glucose hinder the extensibility of tropoelastin by rearranging structural domains and altering hydrogen bonding patterns, respectively. Overall, our investigation helps to reveal the behavior of tropoelastin and the biomechanics of elastin biomaterials in these physiological environments. STATEMENT OF SIGNIFICANCE: Elastin is a key component of elastic fibers which endow many important tissues and organs, from arteries and veins, to skin and heart, with strength and elasticity. During aging and aging-associated diseases, such as diabetes mellitus and atherosclerosis, physicochemical stressors, including hypercalcemia and hyperglycemia, induce accumulated irreversible damage in elastin, and consequently alter mechanical function. Yet, molecular mechanisms associated with these processes are still poorly understood. Here, we present the first study on how these changes in elastin structure and extensibility are induced by hypercalcemia and hyperglycemia at the molecular scale, revealing the essential roles that calcium and glucose play in triggering structural alterations and mechanical stiffness. Our findings yield critical insights into the first steps of hypercalcemia- and hyperglycemia-mediated aging.

Fascicular elastin within tendon contributes to the magnitude and modulus gradient of the elastic stress response across tendon type and species.

Elastin, the main component of elastic fibers, has been demonstrated to significantly influence tendon mechanics using both elastin degradation studies and elastinopathic mouse models. However, it remains unclear how prior results differ between species and functionally distinct tendons and, in particular, how results translate to human tendon. Differences in function between fascicular and interfascicular elastin are also yet to be fully elucidated. Therefore, this study evaluated the quantity, structure, and mechanical contribution of elastin in functionally distinct tendons across species. Tendons with an energy-storing function had slightly more elastin content than tendons with a positional function, and human tendon had at least twice the elastin content of other species. While distinctions in the organization of elastic fibers between fascicles and the interfascicular matrix were observed, differences in structural arrangement of the elastin network between species and tendon type were limited. Mechanical testing paired with enzyme-induced elastin degradation was used to evaluate the contribution of elastin to tendon mechanics. Across all tendons, elastin degradation affected the elastic stress response by decreasing stress values while increasing the modulus gradient of the stress-strain curve. Only the contributions of elastin to viscoelastic properties varied between tendon type and species, with human tendon and energy-storing tendon being more affected. These data suggest that fascicular elastic fibers contribute to the tensile mechanical response of tendon, likely by regulating collagen engagement under load. Results add to prior findings and provide evidence for a more mechanistic understanding of the role of elastic fibers in tendon. STATEMENT OF SIGNIFICANCE: Elastin has previously been shown to influence the mechanical properties of tendon, and degraded or abnormal elastin networks caused by aging or disease may contribute to pain and an increased risk of injury. However, prior work has not fully determined how elastin contributes differently to tendons with varying functional demands, as well as within distinct regions of tendon. This study determined the effects of elastin degradation on the tensile elastic and viscoelastic responses of tendons with varying functional demands, hierarchical structures, and elastin content. Moreover, volumetric imaging and protein quantification were used to thoroughly characterize the elastin network in each distinct tendon. The results presented herein can inform tendon-specific strategies to maintain or restore native properties in elastin-degraded tissue.

2023 TERMIS – AMERICAS Conference &amp; Exhibition Boston Marriott Copley Place April 11–14, 2023

2023 TERMIS – AMERICAS Conference &amp; Exhibition Boston Marriott Copley Place April 11–14, 2023

MP27-14 ELASTIN STAINING OF THE VESTIBULE

You have accessJournal of UrologyCME1 Apr 2023MP27-14 ELASTIN STAINING OF THE VESTIBULE Alyssa Yee, Alain Dury, Johanne Ouellet, Barry Komisaruk, Sue W Goldstein, and Irwin Goldstein Alyssa YeeAlyssa Yee More articles by this author , Alain DuryAlain Dury More articles by this author , Johanne OuelletJohanne Ouellet More articles by this author , Barry KomisarukBarry Komisaruk More articles by this author , Sue W GoldsteinSue W Goldstein More articles by this author , and Irwin GoldsteinIrwin Goldstein More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000003255.14AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: The vestibule is an external genital structure lying 90° to the vaginal canal opening. The vestibule consists of non-keratinized squamous epithelium with numerous rete pegs, underlying lamina propria with nerves, blood vessels, glands, and extracellular matrix (ECM) proteins. During thrusting movements associated with penetrative sexual activity, the vestibule undergoes significant stretching during invagination/evagination. The vestibule also undergoes extreme stretching during childbirth. Elastin is an ECM protein in microfibrils that endows skin structures with ability to stretch, recoil, and have elasticity. Elastin has previously been shown to influence mechanical properties of tendons; degraded or abnormal elastin structures caused by aging or disease may contribute to pain and increased risk of injury. There are limited data on elastin in the vestibule in reproductive age patients and its role in vestibular elasticity/integrity. METHODS: 7 reproductive age patients with entrance dyspareunia from neuroproliferative vestibulodynia, with normal values of testosterone, estradiol, and progesterone, underwent complete vestibulectomy. Tissue blocks were created from the specimen, and 5 υm sections studied with IHC primary antibody. Finally, sections were counterstained with Gill-modified hematoxylin. RESULTS: In all vestibular specimen, there was very high density of elastin underneath the epithelium in rete pegs and throughout the entire lamina propria. There is a density gradient with the highest density immediately deep to the basement membrane of the epithelium. Elastin fibers were arranged in all orientations: coronal (frontal), sagittal (longitudinal), and transverse (axial) planes. CONCLUSIONS: The high density of elastin fibers in rete pegs and through the lamina propria in a multi-planar orientation is suggestive of extreme stretching capability in eugonadal vestibular tissues. The highest density of elastin staining was seen immediately below the basement membrane of the epithelium, which may provide tissue integrity and shear resilience to the epithelial layer. More research is needed on elastic fiber production, organization, and integration with other cutaneous extracellular matrix proteins, and how this may change during androgen insufficiency states such as menopause or with use of combined hormonal contraceptives. Source of Funding: None © 2023 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 209Issue Supplement 4April 2023Page: e367 Advertisement Copyright & Permissions© 2023 by American Urological Association Education and Research, Inc.MetricsAuthor Information Alyssa Yee More articles by this author Alain Dury More articles by this author Johanne Ouellet More articles by this author Barry Komisaruk More articles by this author Sue W Goldstein More articles by this author Irwin Goldstein More articles by this author Expand All Advertisement PDF downloadLoading ...

Synthesis of lysinonorleucine and mass spectrometric analysis of lysinonorleucine and merodesmosine in bovine ligament and eggshell membrane

Elastin is an important extracellular matrix protein that contributes to the elasticity of cells, tissues, and organs. Although crosslinking amino acids such as desmosine and isodesmosine have been identified in elastin, details regarding the structure remain unclear. In this study, an elastin crosslinker, lysinonorleucine, was chemically synthesized and detected in hydrolyzed bovine ligament and eggshell membrane samples utilizing tandem mass spectrometry. Merodesmosine, another crosslinker of elastin, was also measured in the same samples using the same analytical method. The resulting data should aid in the elucidating the crosslinking structure of elastin and eggshell membranes.

Automated Decellularization of the Rodent Epigastric Free Flap: A Comparison of Sodium Dodecyl Sulfate-Based Protocols.

Free tissue transfer to cover complex wounds with exposed critical structures results in donor-site morbidity. Perfusion decellularization and recellularization of vascularized composite tissues is an active area of research to fabricate complex constructs without a donor site. Sodium dodecyl sulfate (SDS)-based protocols remain the predominant choice for decellularization despite the deleterious effects on tissue ultrastructure and capillary networks. We aimed to develop an automated decellularization process and compare different SDS perfusion times to optimize the protocol. A three-dimensional-printed closed-system bioreactor capable of continuously perfusing fluid through the vasculature was used for decellularization. The artery and vein of rat epigastric fasciocutaneous free flaps were cannulated and connected to the bioreactor. Protocols had varying durations of 1% SDS solution (3, 5, and 10 days) followed by 1 day of 1% Triton X-100 and 1 day of 1x phosphate-buffered saline. The residual DNA was quantified. Microarchitecture of the constructs was assessed with histology, and the vascular network was visualized for qualitative assessment. The structural integrity and the microarchitecture of the extracellular matrix was preserved in the 3- and 5-day SDS perfusion groups; however, the subcutaneous tissue of the 10-day protocol lost its structure. Collagen and elastin structures of the pedicle vessels were not compromised by the decellularization process. Five-day SDS exposure group had the least residual DNA content (p < 0.001). Across all protocols, skin consistently had twice as much residual DNA over the subcutaneous tissues. A compact and integrated bioreactor can automate decellularization of free flaps to bioengineer regenerative constructs for future use in reconstruction of complex defects. A decellularization protocol with 5 days of 1% SDS exposure was the most successful to keep the residual DNA content at a minimum while preserving the structural integrity of the tissues.

Biological properties of self-assembled nanofibers of elastin-like block polypeptides for tissue-engineered vascular grafts: platelet inhibition, endothelial cell activation and smooth muscle cell maintenance.

Strategic materials design is essential for the development of small-diameter, tissue-engineered vascular grafts. Self-assembled nanofibers of elastin-like polypeptides represent promising vascular graft components as they replicate the organized elastin structure of native blood vessels. Further, the bioactivity of nanofibers can be modified by the addition of functional peptide motifs. In the present study, we describe the development of a novel nanofiber-forming elastin-like polypeptide (ELP) with an arginine-glutamic acid-aspartic acid-valine (REDV) sequence. The biological characteristics of the REDV-modified ELP nanofibers relevant to applications in vascular grafting were compared to ELP without ligands for integrin, ELP with arginine-glycine-aspartic acid (RGD) sequence, collagen and cell culture glass. Among them, REDV-modified ELP nanofibers met the preferred biological properties for vascular graft materials, i.e. (i) inhibition of platelet adhesion and activation, (ii) endothelial cell adhesion and proliferation and (iii) maintenance of smooth muscle cells in a contractile phenotype to prevent cell overgrowth. The results indicate that REDV-modified ELP nanofibers represent promising candidates for the further development of small-diameter vascular grafts.

Total synthesis of merodesmosine

Elastin is an important extracellular matrix protein responsible for the elasticity of tissues such as ligamentum, arteries, and lungs. Its three-dimensional crosslinking structure plays an important role in its elasticity. However, the precise structure has not yet been clarified since it is difficult to analyze due to its insoluble nature. Merodesmosine is one of the possible crosslinking amino acids in elastin. In this work, the first total synthesis of merodesmosine was achieved in five steps in 21% overall yield from protected allysine. This achievement will aid in the elucidation of the crosslinking structure of elastin.

The expression and role of tenascin C in abdominal aortic aneurysm formation and progression.

OBJECTIVESUp-regulation of tenascin C (TNC), a matricellular protein, produced mainly by vascular smooth muscle cells (VSMC), is associated with the progression and dilation of abdominal aortic aneurysms (AAA). The aims of this study were (i) to evaluate whether serum levels of TNC in patients with AAA patients correlate with aortic diameter and (ii) to clarify the role of TNC in formation and progression of AAA in a murine model.METHODSIn 15 patients with AAA serum levels of TNC were measured and correlated with aortic diameters. Moreover, in a murine calcium chloride AAA model, the impact of TNC deficiency on AAA diameter was evaluated. Finally, human VSMC were incubated with TNC to clarify its regulating potential.RESULTSIn the clinical cohort, there was a trend of correlation between serum TNC levels and AAA diameter (P = 0.055). TNC knock out mice with AAA showed significantly lower diameter ratios compared to the wild-type group (WT) 3 weeks (P < 0.05) and 10 weeks (P < 0.05) after AAA induction. Immunohistochemistry revealed increased TNC expression in aortic tissue from WT with AAA as compared sham-operated mice. Furthermore, WT with AAA showed a more disrupted Elastin structure than TNC knock out mice 10 weeks after AAA induction. In human aortic VSMC, TNC incubation induced expression of remodelling associated proteins.CONCLUSIONSTNC might play a causative role in the formation, dilation and progression of AAA. Our results indicate that TNC might be a biomarker as well as a potential therapeutic target in the treatment of AAA.

Elastic Laminar Reorganization Occurs with Outward Diameter Expansion during Collateral Artery Growth and Requires Lysyl Oxidase for Stabilization.

When a large artery becomes occluded, hemodynamic changes stimulate remodeling of arterial networks to form collateral arteries in a process termed arteriogenesis. However, the structural changes necessary for collateral remodeling have not been defined. We hypothesize that deconstruction of the extracellular matrix is essential to remodel smaller arteries into effective collaterals. Using multiphoton microscopy, we analyzed collagen and elastin structure in maturing collateral arteries isolated from ischemic rat hindlimbs. Collateral arteries harvested at different timepoints showed progressive diameter expansion associated with striking rearrangement of internal elastic lamina (IEL) into a loose fibrous mesh, a pattern persisting at 8 weeks. Despite a 2.5-fold increase in luminal diameter, total elastin content remained unchanged in collaterals compared with control arteries. Among the collateral midzones, baseline elastic fiber content was low. Outward remodeling of these vessels with a 10–20 fold diameter increase was associated with fractures of the elastic fibers and evidence of increased wall tension, as demonstrated by the straightening of the adventitial collagen. Inhibition of lysyl oxidase (LOX) function with β-aminopropionitrile resulted in severe fragmentation or complete loss of continuity of the IEL in developing collaterals. Collateral artery development is associated with permanent redistribution of existing elastic fibers to accommodate diameter growth. We found no evidence of new elastic fiber formation. Stabilization of the arterial wall during outward remodeling is necessary and dependent on LOX activity.

Elastin Structure, Synthesis, Regulatory Mechanism and Relationship With Cardiovascular Diseases.

As the primary component of elastic fibers, elastin plays an important role in maintaining the elasticity and tensile ability of cardiovascular, pulmonary and many other tissues and organs. Studies have shown that elastin expression is regulated by a variety of molecules that have positive and negative regulatory effects. However, the specific mechanism is unclear. Moreover, elastin is reportedly involved in the development and progression of many cardiovascular diseases through changes in its expression and structural modifications once deposited in the extracellular matrix. This review article summarizes the role of elastin in myocardial ischemia-reperfusion, atherosclerosis, and atrial fibrillation, with emphasis on the potential molecular regulatory mechanisms.

PI 3-kinase isoform PI3Kalpha controls smooth muscle cell functionality and protects against aortic aneurysm formation

Abstract Background Class I PI 3-kinase isoform PI3Kα is a lipid kinase and signals downstream of receptor tyrosine kinases. Smooth muscle cells (SMCs) lacking PI3Kα are characterized by impaired proliferation, migration and survival. Mice, harbouring a smooth muscle specific PI3Kα deficiency (SM-PI3Kα−/−), display reduced vascular wall thickness and impaired vascular remodeling in response to vessel injury. We hypothesize that SM-PI3Kα−/− mice are prone to aortic aneurysm (AA) formation due to impaired SMC functions. Herein, we investigated, how PI3Kα-dependent signaling in SMCs affect aortic aneurysm (AA) formation, aortic wall structure, and expression of extracellular matrix (ECM) components. Methods and results AA formation in SM-PI3Kα−/− mice and wild-type littermates was examined by means of the “porcine pancreatic elastase” (PPE) AA model. PPE was infused into the infrarenal aorta to induce AA formation. Ultrasound examination revealed a significantly increased aortic diameter in SM-PI3Kα−/− mice (1.22±0.12 mm) compared to wild-type animals (0.96±0.02 mm, p=0.014). These data indicate a protective function of SM-PI3Kα in AA formation. In addition, the media thickness in the abdominal aorta was significantly reduced in SM-PI3Kα−/− mice (29.0±3.1 vs. 42.5±4.1 μm). Ultrastructural analysis of aortic wall morphology in SM-PI3Kα−/−mice using transmission electron microscopy (TEM) showed a deranged tunica media with detached SMCs and increased apoptotic cell death. Consequently, SM-PI3Kα deficiency significantly diminished responsiveness of aortic rings to vasodilator acetylcholine and NO-donor nitroglycerin, further indicating impaired aortic wall structure. Western blots demonstrated a reduced elastin and fibrillin expression in SMCs from SM-PI3Kα−/− mice. Furthermore, immunofluorescence stainings of PI3Kα−/− and wild-type SMCs, cultured for seven days under 10% fetal calf serum containing DMEM medium, showed significantly disturbed structures of elastin-, fibrillin-1- and collagen-1-fibers. These data indicate that PI3Kα signaling contributes to elastic fiber homeostasis thus affecting SMC phenotypic modulation. Immunoblots demonstrated that PDGF and insulin induced phosphorylation and inactivation of key regulators of SMC differentiation and dedifferentiation including FoxO1, FoxO3a, Foxo4, and GSK3b, respectively, were reduced or even abrogated in PI3Kα−/− SMCs. Conclusion These data show that deficiency of PI3Kα in SMCs promotes the formation and progression of AA. Causative is a deranged aortic structure of SM-PI3Kα−/− aortae which can likely be attributed to an impaired production of elastic fiber components by PI3Kα−/− SMCs. Funding Acknowledgement Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Deutsche Forschungsgemeinschaft