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.

Tropoelastin Improves Post-Infarct Cardiac Function.

BACKGROUND: Myocardial infarction (MI) is among the leading causes of death worldwide. Following MI, necrotic cardiomyocytes are replaced by a stiff collagen-rich scar. Compared to collagen, the extracellular matrix protein elastin has high elasticity and may have more favorable properties within the cardiac scar. We sought to improve post-MI healing by introducing tropoelastin, the soluble subunit of elastin, to alter scar mechanics early after MI. METHODS AND RESULTS: We developed an ultrasound-guided direct intramyocardial injection method to administer tropoelastin directly into the left ventricular anterior wall of rats subjected to induced MI. Experimental groups included shams and infarcted rats injected with either PBS vehicle control or tropoelastin. Compared to vehicle treated controls, echocardiography assessments showed tropoelastin significantly improved left ventricular ejection fraction (64.7±4.4% versus 46.0±3.1% control) and reduced left ventricular dyssynchrony (11.4±3.5 ms versus 31.1±5.8 ms control) 28 days post-MI. Additionally, tropoelastin reduced post-MI scar size (8.9±1.5% versus 20.9±2.7% control) and increased scar elastin (22±5.8% versus 6.2±1.5% control) as determined by histological assessments. RNA sequencing (RNAseq) analyses of rat infarcts showed that tropoelastin injection increased genes associated with elastic fiber formation 7 days post-MI and reduced genes associated with immune response 11 days post-MI. To show translational relevance, we performed immunohistochemical analyses on human ischemic heart disease cardiac samples and showed an increase in tropoelastin within fibrotic areas. Using RNA-seq we also demonstrated the tropoelastin gene ELN is upregulated in human ischemic heart disease and during human cardiac fibroblast-myofibroblast differentiation. Furthermore, we showed by immunocytochemistry that human cardiac fibroblast synthesize increased elastin in direct response to tropoelastin treatment. CONCLUSIONS: We demonstrate for the first time that purified human tropoelastin can significantly repair the infarcted heart in a rodent model of MI and that human cardiac fibroblast synthesize elastin. Since human cardiac fibroblasts are primarily responsible for post-MI scar synthesis, our findings suggest exciting future clinical translation options designed to therapeutically manipulate this synthesis.

Liquid to solid transition of elastin condensates.

Liquid-liquid phase separation of tropoelastin has long been considered to be an important early step in the complex process of elastin fiber assembly in the body and has inspired the development of elastin-like peptides with a wide range of industrial and biomedical applications. Despite decades of study, the material state of the condensed liquid phase of elastin and its subsequent maturation remain poorly understood. Here, using a model minielastin that mimics the alternating domain structure of full-length tropoelastin, we examine the elastin liquid phase. We combine differential interference contrast (DIC), fluorescence, and scanning electron microscopy with particle-tracking microrheology to resolve the material transition occurring within elastin liquids over time in the absence of exogenous cross-linking. We find that this transition is accompanied by an intermediate stage marked by the coexistence of insoluble solid and dynamic liquid phases giving rise to significant spatial heterogeneities in material properties. We further demonstrate that varying the length of the terminal hydrophobic domains of minielastins can tune the maturation process. This work not only resolves an important step in the hierarchical assembly process of elastogenesis but further contributes mechanistic insight into the diverse repertoire of protein condensate maturation pathways with emerging importance across biology.

Directed Assembly of Elastic Fibers via Coacervate Droplet Deposition on Electrospun Templates.

Elastic fibers provide critical elasticity to the arteries, lungs, and other organs. Elastic fiber assembly is a process where soluble tropoelastin is coacervated into liquid droplets, cross-linked, and deposited onto and into microfibrils. While much progress has been made in understanding the biology of this process, questions remain regarding the timing of interactions during assembly. Furthermore, it is unclear to what extent fibrous templates are needed to guide coacervate droplets into the correct architecture. The organization and shaping of coacervate droplets onto a fiber template have never been previously modeled or employed as a strategy for shaping elastin fiber materials. Using an in vitro system consisting of elastin-like polypeptides (ELPs), genipin cross-linker, electrospun polylactic-co-glycolic acid (PLGA) fibers, and tannic acid surface coatings for fibers, we explored ELP coacervation, cross-linking, and deposition onto fiber templates. We demonstrate that integration of coacervate droplets into a fibrous template is primarily influenced by two factors: (1) the balance of coacervation and cross-linking and (2) the surface energy of the fiber templates. The success of this integration affects the mechanical properties of the final fiber network. Our resulting membrane materials exhibit highly tunable morphologies and a range of elastic moduli (0.8-1.6 MPa) comparable to native elastic fibers.

Stochastic simulations of self-organized elastogenesis in the developing lung.

In the normal lung, the dominant cable is an elastic "line element" composed of elastin fibers bound to a protein scaffold. The cable line element maintains alveolar geometry by balancing surface forces within the alveolus and changes in lung volume with exercise. Recent work in the postnatal rat lung has suggested that the process of cable development is self-organized in the extracellular matrix. Early in postnatal development, a blanket of tropoelastin (TE) spheres appear in the primitive lung. Within 7 to 10 days, the TE spheres are incorporated into a distributed protein scaffold creating the mature cable line element. To study the process of extracellular assembly, we used cellular automata (CA) simulations. CA simulations demonstrated that the intermediate step of tropoelastin self-aggregation into TE spheres enhanced the efficiency of cable formation more than 5-fold. Similarly, the rate of tropoelastin production had a direct impact on the efficiency of scaffold binding. The binding affinity of the tropoelastin to the protein scaffold, potentially reflecting heritable traits, also had a significant impact on cable development. In contrast, the spatial distribution of TE monomer production, increased Brownian motion and variations in scaffold geometry did not significantly impact simulations of cable development. We conclude that CA simulations are useful in exploring the impact of concentration, geometry, and movement on the fundamental process of elastogenesis.

Determining the Sequence Dependency of Self-Assembly of Elastin-Like Peptides Using Short Peptide Analogues with Shuffled Repetitive Sequences.

Synthetic elastin-like peptides (ELPs) that possess characteristic tropoelastin-derived hydrophobic repetitive sequences, such as (VPGVG)n, exhibit thermoresponsive reversible self-assembly. Although their thermoresponsive properties have been well-studied, the sequence-dependent and structural requirements for self-assembly remain ambiguous. In particular, it is still unclear whether the amino acid sequences derived from tropoelastin are necessary for self-assembly. In this study, 11 sequence-shuffled ELP analogues based on (FPGVG)5, which is a previously developed short ELP (sELP), were designed to elucidate the sequence-dependent and structural requirements for their self-assembly. Among them, eight shuffled peptides exhibited self-assembling properties, whereas the other three peptides were difficult to dissolve in water. Structural analyses revealed that the structural characteristics of the three insoluble peptides were different from those of their thermoresponsive analogues. Furthermore, the secondary structures of the peptide analogues possessing the self-assembly abilities were different from each other. These results suggest that the potential for self-assembly and water solubility of sELPs depend on the primary structure in each repeated unit. Moreover, several shuffled analogues exhibited more potent self-assembling properties than the original (FPGVG)5, indicating that shorter ELPs can be obtained using their novel motifs as repetitive units. We also observed that the presence of Pro-Gly sequence in the repeating units was advantageous in terms of peptide solubility. Although further analysis will be necessary to elucidate the molecular mechanism underlying the self-assembly of these sELPs, this study provides insights into the relationship between the amino acid sequence and the self-assembling ability of the peptides for developing new sELPs for various applications.

Elastases and elastokines: elastin degradation and its significance in health and disease.

Elastin is an important protein of the extracellular matrix of higher vertebrates, which confers elasticity and resilience to various tissues and organs including lungs, skin, large blood vessels and ligaments. Owing to its unique structure, extensive cross-linking and durability, it does not undergo significant turnover in healthy tissues and has a half-life of more than 70 years. Elastin is not only a structural protein, influencing the architecture and biomechanical properties of the extracellular matrix, but also plays a vital role in various physiological processes. Bioactive elastin peptides termed elastokines - in particular those of the GXXPG motif - occur as a result of proteolytic degradation of elastin and its non-cross-linked precursor tropoelastin and display several biological activities. For instance, they promote angiogenesis or stimulate cell adhesion, chemotaxis, proliferation, protease activation and apoptosis. Elastin-degrading enzymes such as matrix metalloproteinases, serine proteases and cysteine proteases slowly damage elastin over the lifetime of an organism. The destruction of elastin and the biological processes triggered by elastokines favor the development and progression of various pathological conditions including emphysema, chronic obstructive pulmonary disease, atherosclerosis, metabolic syndrome and cancer. This review gives an overview on types of human elastases and their action on human elastin, including the formation, structure and biological activities of elastokines and their role in common biological processes and severe pathological conditions.

Globule and fiber formation with elastin-like polypeptides: a balance of coacervation and crosslinking.

Elastic fiber assembly is a complex process that requires the coacervation and cross-linking of the protein building block tropoelastin. To date, the order, timing, and interplay of coacervation and crosslinking is not completely understood, despite a great number of advances into understanding the molecular structure and functions of the many proteins involved in elastic fiber assembly. With a simple in vitro model using elastin-like polypeptides and the natural chemical crosslinker genipin, we demonstrate the strong influence of the timing and kinetics of crosslinking reaction on the coacervation, crosslinking extent, and resulting morphology of elastin. We also outline a method for analyzing elastin droplet network formation as a heuristic for measuring the propensity for elastic fiber formation. From this we show that adding crosslinker during peak coacervation dramatically increases the propensity for droplet network formation.

Fibulin-4 exerts a dual role in LTBP-4L-mediated matrix assembly and function.

Elastogenesis is a hierarchical process by which cells form functional elastic fibers, providing elasticity and the ability to regulate growth factor bioavailability in tissues, including blood vessels, lung, and skin. This process requires accessory proteins, including fibulin-4 and -5, and latent TGF binding protein (LTBP)-4. Our data demonstrate mechanisms in elastogenesis, focusing on the interaction and functional interdependence between fibulin-4 and LTBP-4L and its impact on matrix deposition and function. We show that LTBP-4L is not secreted in the expected extended structure based on its domain composition, but instead adopts a compact conformation. Interaction with fibulin-4 surprisingly induced a conformational switch from the compact to an elongated LTBP-4L structure. This conversion was only induced by fibulin-4 multimers associated with increased avidity for LTBP-4L; fibulin-4 monomers were inactive. The fibulin-4-induced conformational change caused functional consequences in LTBP-4L in terms of binding to other elastogenic proteins, including fibronectin and fibrillin-1, and of LTBP-4L assembly. A transient exposure of LTBP-4L with fibulin-4 was sufficient to stably induce conformational and functional changes; a stable complex was not required. These data define fibulin-4 as a molecular extracellular chaperone for LTBP-4L. The altered LTBP-4L conformation also promoted elastogenesis, but only in the presence of fibulin-4, which is required to escort tropoelastin onto the extended LTBP-4L molecule. Altogether, this study provides a dual mechanism for fibulin-4 in 1) inducing a stable conformational and functional change in LTBP-4L, and 2) promoting deposition of tropoelastin onto the elongated LTBP-4L.

Soluble matrix protein is a potent modulator of mesenchymal stem cell performance.

We challenge the conventional designation of structural matrix proteins primarily as supporting scaffolds for resident cells. The extracellular matrix protein tropoelastin is classically regarded as a structural component that confers mechanical strength and resilience to tissues subject to repetitive elastic deformation. Here we describe how tropoelastin inherently induces a range of biological responses, even in cells not typically associated with elastic tissues and in a manner unexpected of typical substrate-dependent matrix proteins. We show that tropoelastin alone drives mesenchymal stem cell (MSC) proliferation and phenotypic maintenance, akin to the synergistic effects of potent growth factors such as insulin-like growth factor 1 and basic fibroblast growth factor. In addition, tropoelastin functionally surpasses these growth factors, as well as fibronectin, in allowing substantial media serum reduction without loss of proliferative potential. We further demonstrate that tropoelastin elicits strong mitogenic and cell-attractive responses, both as an immobilized substrate and as a soluble additive, via direct interactions with cell surface integrins αvß3 and αvß5. This duality of action converges the long-held mechanistic dichotomy between adhesive matrix proteins and soluble growth factors and uncovers the powerful, untapped potential of tropoelastin for clinical MSC expansion and therapeutic MSC recruitment. We propose that the potent, growth factor-like mitogenic and motogenic abilities of tropoelastin are biologically rooted in the need for rapid stem cell homing and proliferation during early development and/or wound repair.

Elastic Fibre Proteins in Elastogenesis and Wound Healing.

As essential components of our connective tissues, elastic fibres give tissues such as major blood vessels, skin and the lungs their elasticity. Their formation is complex and co-ordinately regulated by multiple factors. In this review, we describe key players in elastogenesis: fibrillin-1, tropoelastin, latent TGFß binding protein-4, and fibulin-4 and -5. We summarise their roles in elastogenesis, discuss the effect of their mutations on relevant diseases, and describe their interactions involved in forming the elastic fibre network. Moreover, we look into their roles in wound repair for a better understanding of their potential application in tissue regeneration.

The "Elastic Perspective" of SARS-CoV-2 Infection and the Role of Intrinsic and Extrinsic Factors.

Elastin represents the structural component of the extracellular matrix providing elastic recoil to tissues such as skin, blood vessels and lungs. Elastogenic cells secrete soluble tropoelastin monomers into the extracellular space where these monomers associate with other matrix proteins (e.g., microfibrils and glycoproteins) and are crosslinked by lysyl oxidase to form insoluble fibres. Once elastic fibres are formed, they are very stable, highly resistant to degradation and have an almost negligible turnover. However, there are circumstances, mainly related to inflammatory conditions, where increased proteolytic degradation of elastic fibres may lead to consequences of major clinical relevance. In severely affected COVID-19 patients, for instance, the massive recruitment and activation of neutrophils is responsible for the profuse release of elastases and other proteolytic enzymes which cause the irreversible degradation of elastic fibres. Within the lungs, destruction of the elastic network may lead to the permanent impairment of pulmonary function, thus suggesting that elastases can be a promising target to preserve the elastic component in COVID-19 patients. Moreover, intrinsic and extrinsic factors additionally contributing to damaging the elastic component and to increasing the spread and severity of SARS-CoV-2 infection are reviewed.

An acellular tissue engineered biomimetic wound healing device created using collagen and tropoelastin accelerates wound healing.

AIM: Tissue engineering has historically involved research combining scaffolds, cells, and active biomolecules to treat multiple pathologies. The current research seeks to determine if the wound healing cascade can be modulated using acellular scaffolds, engineered to create an acellular electrospun dermal biomimetic. METHODS: The dermal biomimetic has a similar architecture to the dermis, porosity and fiber diameter, as well as physiologically relevant ratios of the primary structural dermal proteins, collagen and tropoelastin. This biomimetic wound healing device (BMWHD) was implanted into a full thickness dermal wound murine model for six days. RESULTS: WHD-treated wounds had 30% greater re-epithelialization with a thicker epidermis, new elastin fibers in the wound bed, and healed architecture that matched unwounded extracellular matrix. CONCLUSIONS: Using these WHDs that closely match the native architecture and protein concentrations, accelerated the wound through the wound healing cascade and supports the hypothesis that structure alone can influence function when engineering acellular dermal biomimetic devices.

Fuzzy binding model of molecular interactions between tropoelastin and integrin alphaVbeta3.

Tropoelastin is the highly flexible monomer subunit of elastin, required for the resilience of the extracellular matrix in elastic tissues. To elicit biological signaling, multiple sites on tropoelastin bind to cell surface integrins in a poorly understood multifactorial process. We constructed a full atomistic molecular model of the interactions between tropoelastin and integrin αvß3 using ensemble-based computational methodologies. Conformational changes of integrin αvß3 associated with outside-in signaling were more frequently facilitated in an ensemble in which tropoelastin bound the integrin's α1 helix rather than the upstream canonical binding site. Our findings support a model of fuzzy binding, whereby many tropoelastin conformations and defined sites cooperatively interact with multiple αvß3 regions. This model explains prior experimental binding to distinct tropoelastin regions, domains 17 and 36, and points to the cooperative participation of domain 20. Our study highlights the utility of ensemble-based approaches in helping to understand the interactive mechanisms of functionally significant flexible proteins.

Dynamics in natural and designed elastins and their relation to elastic fiber structure and recoil.

Elastin fibers assemble in the extracellular matrix from the precursor protein tropoelastin and provide the flexibility and spontaneous recoil required for arterial function. Unlike many proteins, a structure-function mechanism for elastin has been elusive. We have performed detailed NMR relaxation studies of the dynamics of the minielastins 24x' and 20x' using solution NMR, and of purified bovine elastin fibers in the presence and absence of mechanical stress using solid state NMR. The low sequence complexity of the minielastins enables us to determine average dynamical timescales and degrees of local ordering in the cross-link and hydrophobic modules separately using NMR relaxation by taking advantage of their residue-specific resolution. We find an extremely high degree of disorder, with order parameters for the entirety of the hydrophobic domains near zero, resembling that of simple chemical polymers and less than the order parameters that have been observed in other intrinsically disordered proteins. We find that average backbone order parameters in natural, purified elastin fibers are comparable to those found in 24x' and 20x' in solution. The difference in dynamics, compared with the minielastins, is that backbone correlation times are significantly slowed in purified elastin. Moreover, when elastin is mechanically stretched, the high chain disorder in purified elastin is retained, showing that any change in local ordering is below that detectable in our experiment. Combined with our previous finding of a 10-fold increase in the ordering of water when fully hydrated elastin fibers are stretched by 50%, these results support the hypothesis that stretch induced solvent ordering, i.e., the hydrophobic effect, is a key player in the elastic recoil of elastin as opposed to configurational entropy loss.

The evolutionary background and functional consequences of the rs2071307 polymorphism in human tropoelastin.

Elastin is a major polymeric protein of the extracellular matrix, providing critical properties of extensibility and elastic recoil. The rs2071307 genomic polymorphism, resulting in the substitution of a serine for a glycine residue in a VPG motif in tropoelastin, has an unusually high minor allele frequency in humans. A consequence of such allelic heterozygosity would be the presence of a heterogeneous elastin polymer in up to 50% of the population, a situation which appears to be unique to Homo sapiens. VPG motifs are extremely common in hydrophobic domains of tropoelastins and are the sites of transient ß-turns that are essential for maintaining the conformational flexibility required for its function as an entropic elastomer. Earlier data demonstrated that single amino acid substitutions in tropoelastin can have functional consequences for polymeric elastin, particularly when present in mixed polymers. Here, using NMR and molecular dynamics approaches, we show the rs2071307 polymorphism reduces local propensity for ß-turn formation, with a consequent increase in polypeptide hydration and an expansion of the conformational ensemble manifested as an increased hydrodynamic radius, radius of gyration and asphericity. Furthermore, this substitution affects functional properties of polymeric elastin, particularly in heterogeneous polymers mimicking allelic heterozygosity. We discuss whether such effects, together with the unusually high minor allele frequency of the polymorphism, could imply some some evolutionary advantage for the heterozygous state.

Elastic tissue disruption is a major pathogenic factor to human vascular disease.

Elastic fibers are essential components of the arterial extracellular matrix. They consist of the protein elastin and an array of microfibrils that support the protein and connect it to the surrounding matrix. The elastin gene encodes tropoelastin, a protein that requires extensive cross-linking to become elastin. Tropoelastin is expressed throughout human life, but its expression levels decrease with age, suggesting that the potential to synthesize elastin persists during lifetime although declines with aging. The initial abnormality documented in human atherosclerosis is fragmentation and loss of the elastic network in the medial layer of the arterial wall, suggesting an imbalance between elastic fiber injury and restoration. Damaged elastic structures are not adequately repaired by synthesis of new elastic elements. Progressive collagen accumulation follows medial elastic fiber disruption and fibrous plaques are formed, but advanced atherosclerosis lesions do not develop in the absence of prior elastic injury. Aging is associated with arterial extracellular matrix anomalies that evoke those present in early atherosclerosis. The reduction of elastic fibers with subsequent collagen accumulation leads to arterial stiffening and intima-media thickening, which are independent predictors of incident hypertension in prospective community-based studies. Arterial stiffening precedes the development of hypertension. The fundamental role of the vascular elastic network to arterial structure and function is emphasized by congenital disorders caused by mutations that disrupt normal elastic fiber production. Molecular changes in the genes coding tropoelastin, lysyl oxidase (tropoelastin cross-linking), and elastin-associated microfibrils, including fibrillin-1, fibulin-4, and fibulin-5 produce severe vascular injury due to absence of functional elastin.

Molecular model of human tropoelastin and implications of associated mutations.

Protein folding poses unique challenges for large, disordered proteins due to the low resolution of structural data accessible in experiment and on the basis of short time scales and limited sampling attainable in computation. Such molecules are uniquely suited to accelerated-sampling molecular dynamics algorithms due to a flat-energy landscape. We apply these methods to report here the folded structure in water from a fully extended chain of tropoelastin, a 698-amino acid molecular precursor to elastic fibers that confer elasticity and recoil to tissues, finding good agreement with experimental data. We then study a series of artificial and disease-related mutations, yielding molecular mechanisms to explain structural differences and variation in hierarchical assembly observed in experiment. The present model builds a framework for studying assembly and disease and yields critical insight into molecular mechanisms behind these processes. These results suggest that proteins with disordered regions are suitable candidates for characterization by this approach.

Pathological investigations and correlation research of microfibrillar-associated protein 4 and tropoelastin in oral submucous fibrosis.

BACKGROUND: Oral submucous fibrosis (OSF), distinguished by abnormal collagen deposition, is a potentially malignant disorder with 4.2% (95% CI 2.7-5.6%) of malignant transformation and rising global prevalence. However, the precise pathogenesis and effective treatment remain elusive and controversial despite the abundance of literature on this topic. Therefore, it is crucial to explore the clinicopathological characteristics and potential markers for the diagnosis and prognosis of OSF. The objective of this study was to evaluate the influence and correlation of Microfibrillar-associated protein 4 (MFAP4) and tropoelastin (TE) in the development of OSF patients. MATERIAL AND METHODS: Clinicopathological factors, hematoxylin-eosin (HE) and Masson trichome staining, immunohistochemical characteristics and the correlation between MFAP4 and TE were recorded and compared among different stages of OSF progression among cases (n = 60) and controls (n = 10). Student's t test, ANOVA analysis, and the chi-square test were performed to compare the categorical variables for clinicopathological characteristics and the expression level of MFAP4 and TE between the fibrotic and normal tissues. Correlation analysis of MFAP4 and TE was performed using Pearson's correlation test and linear regression. RESULTS: MFAP4 and TE proteins are upregulated and increased gradually in patients with varying stages of OSF, relative to the control group. Furthermore, statistical analyses revealed that the expression level of MFAP4 was positively associated with TE, with a Pearson correlation coefficient of 0.3781 (p = 0.0048). Clinically, we found that OSF affected more males than females, with a ratio of 29:1. The age range was 16-60 years, and the mean age was 36.25 ± 10.25 years. In patients younger than 40 years, the positive expression rate of MFAP4 and TE was higher than in those over 40 years. All OSF cases had chewed areca nut, with 51.67% smoking tobacco. CONCLUSIONS: Our study elucidates that the accumulation of MFAP4 and TE proteins may play a vital role in the occurrence and development of OSF and may be promising candidate moleculars for prevention, diagnosis, and treatment strategies for OSF in the future.

Association between single nucleotide polymorphisms of tropoelastin gene and aortic dissection. / å¼¹åŠ›è›‹ç™½åŽŸåŸºå› å•æ ¸è‹·é ¸å¤šæ€æ€§ä¸Žä¸»åŠ¨è„‰å¤¹å±‚çš„å ³ç³».

OBJECTIVES: To evaluate the relation between single nucleotide polymorphisms (SNPs) of tropoelastin gene and aortic dissection (AD) via identifying SNPs in the tropoelastin gene, and to detect the level of tropoelastin mRNA, elastin and elastic fibers. METHODS: The specimens of the AD group (n=96) and the control group (n=95), including their blood and aortic wall tissues, were collected. DNA was extracted from the blood samples in the 2 groups, and the SNPs in the tropoelastin gene were examined by the MassARRAY genotyping technique, and their haplotypes were constructed by PHASE software. The expression of tropoelastin mRNA and elastin in the aortic tunica media was respectively detected by real-time PCR or Western blotting. Elastin Van Gieson (EVG) staining was used to observe the shape of aortic tunica media and clarify the distribution of elastic fibers. The frequency of genotypes and haplotypes of SNP loci in the tropoelastin gene was analyzed and compared between the 2 groups, and the expression of tropoelastin mRNA, elastin and elastic fibers were also compared. RESULTS: Seven SNP loci of the tropoelastin gene were detected in these samples. Among them, 5 SNP loci were polymorphic. The frequency of 3 SNP loci[rs2071307 (G/A), rs34945509 (C/T) and rs17855988 (G/C)] was significantly different between the AD group and the control group (all P<0.05). There were significantly different in the haplotypes frequency of rs2071307 (G/A), rs34945509 (C/T) and rs17855988 (G/C) between the 2 groups (all P<0.01). Real-time PCR and Western blotting showed that the relative expression of tropoelastin mRNA and elastin in the aortic tunica media in the AD group was significantly lower than that in the control group (P<0.05). EVG staining showed that the aortic tunica media was torn, the morphology and structure of elastic fibers were broken, cracked, and disordered in the AD group, while the aortic tunica media was in complete structure and well arrangement.The elastic fibers were presented closely and orderly in the control group. CONCLUSIONS: The polymorphisms of rs2071307 (G/A), rs34945509 (C/T), and rs17855988(G/C) in the tropoelastin gene may eventually affect the synthesis of elastic fibers and they may play an important role in the occurrence of AD.