Elastic Fiber Formation Research Articles

Fibrillin-2 is a key mediator of smooth muscle extracellular matrix homeostasis during mouse tracheal tubulogenesis.

Epithelial tubes, comprised of polarised epithelial cells around a lumen, are crucial for organ function. However, the molecular mechanisms underlying tube formation remain largely unknown. Here, we report on the function of fibrillin (FBN)2, an extracellular matrix (ECM) glycoprotein, as a critical regulator of tracheal tube formation.We performed a large-scale forward genetic screen in mouse to identify regulators of respiratory organ development and disease. We identified Fbn2 mutants which exhibit shorter and narrowed tracheas as well as defects in tracheal smooth muscle cell alignment and polarity.We found that FBN2 is essential for elastic fibre formation and Fibronectin accumulation around tracheal smooth muscle cells. These processes appear to be regulated at least in part through inhibition of p38-mediated upregulation of matrix metalloproteinases (MMPs), as pharmacological decrease of p38 phosphorylation or MMP activity partially attenuated the Fbn2 mutant tracheal phenotypes. Analysis of human tracheal tissues indicates that a decrease in ECM proteins, including FBN2 and Fibronectin, is associated with tracheomalacia.Our findings provide novel insights into the role of ECM homeostasis in mesenchymal cell polarisation during tracheal tubulogenesis.

Genome sequence of walking catfish (Clarias batrachus) provides insights into terrestrial adaptation

BackgroundWalking catfish (Clarias batrachus) is a freshwater fish capable of air-breathing and locomotion on land. It usually inhabits various low-oxygen habitats, burrows inside the mudflat, and sometimes “walks” to search for suitable environments during summer. It has evolved accessory air-breathing organs for respiring air and corresponding mechanisms to survive in such challenging environments. Thereby, it serves as a great model for understanding adaptations to terrestrial life.ResultsComparative genomics with channel catfish (Ictalurus punctatus) revealed specific adaptations of C. batrachus in DNA repair, enzyme activator activity, and small GTPase regulator activity. Comparative analysis with 11 non-air-breathing fish species suggested adaptive evolution in gene expression and nitrogenous waste metabolic processes. Further, myoglobin, olfactory receptor related to class A G protein-coupled receptor 1, and sulfotransferase 6b1 genes were found to be expanded in the air-breathing walking catfish genome, with 15, 15, and 12 copies, respectively, compared to non-air-breathing fishes that possess only 1–2 copies of these genes. Additionally, we sequenced and compared the transcriptomes of the gill and the air-breathing organ to characterize the mechanism of aerial respiration involved in elastic fiber formation, oxygen binding and transport, angiogenesis, ion homeostasis and acid-base balance. The hemoglobin genes were expressed dramatically higher in the air-breathing organ than in the gill of walking catfish.ConclusionsThis study provides an important genomic resource for understanding the adaptive mechanisms of walking catfish to terrestrial environments. It is possible that the coupling of enhanced abilities for oxygen storage and oxygen transport through genomic expansion of myoglobin genes and transcriptomic up-regulation of hemoglobin and angiogenesis-related genes are important components of the molecular basis for adaptation of this aquatic species to terrestrial life.

Interactions between lysyl oxidases and ADAMTS proteins suggest a novel crosstalk between two extracellular matrix families

The extracellular matrix (ECM) regulates numerous cellular events in addition to providing structural integrity. Among several protein and enzyme families implicated in functions of the ECM, the lysyl oxidases and ADAMTS proteins are known to participate in microfibril and elastic fiber formation as well as ECM-associated signaling. A yeast two-hybrid screen to identify lysyl oxidase (LOX) binding proteins identified ADAMTSL4 as a potential interactor. We demonstrate here that several members of the LOX and ADAMTS families interact with one another. Upon investigating the interaction between LOX and ADAMTSL2 we found that the absence or inhibition of Lox affected ADAMTSL2 molecular forms and reduced its tissue levels. Thus, ADAMTSL2 stability and inter-molecular complexes may depend on the activity of lysyl oxidases.

Stereological and Morphometric Study of Type 3 Collagen Formation in the Cutaneous Wounds of Diabetic Mice Treated with Mesenchymal Stem Cells

Introduction: Wound healing is a progressive, essential and complex physiological process that occurs as a restorative response after a tissue injury. It involves three phases: inflammation, proliferation and maturation. Exogenous, endogenous and pathological factors may interfere in the cicatricial process in humans and animals by altering the balance between the synthesis, degradation and remodelling of collagen and elastic fibres. Diabetes mellitus is a progressive metabolic disease that alters elastogenesis and collagenesis and induces delays in the healing process. Scientific evidence suggests that mesenchymal stem cells modulate the cicatricial response. Thus the objective of this work was to perform stereological and morphometric analysis to determine the formation of dermal fibres in cutaneous fragments of a murine model of diabetes mellitus.Materials, Methods & Results: Histological sections were obtained from the cutaneous wounds of diabetic mice. The cutaneous wounds were previously treated with autogenous mesenchymal stem cells, physiological solution or polyurethane membrane. The histological sections were subsequently processed and stained for type 1 and 3 collagen fibres and elastic fibres using Picrosirius Red and Weigert staining, respectively. Histological sections stained with Picrosirius Red presented three types of birefringence under polarised light microscopy that corresponded to red colours for type 1 collagen and green and yellow colours for type 3 collagen. Weigert staining presented three colours for histological structures under white light microscopy that corresponded to black colours for elastic fibres, variations in colour from pink to purple for other structures and dermal attachments. The elastic fibres, represented by a black colour, presented in a heterogeneous form and were either identified as thin, punctiform or rectangular fibres or as elastic agglomerates. A greater volume of elastic fibres was observed in the superficial dermis than in the deep dermis, arranged irregularly. These fibres were organised longitudinally to the dermo-epidermal junction and surrounding the blood vessels and hair follicles. The images obtained were evaluated using the Cavalieri principle of stereology to obtain quantitative data in three-dimensions (3D), represented by the volume of the dermal fibres, and by the colour segmentation method. The K-means clustering plug-in in Image J® was used to quantify the area of the dermal fibres in the cutaneous wounds after the proposed dermatological treatments. A total of 90 images were obtained and analysed. No statistically significant differences (P > 0.01) were observed in the volume or area of type 1 collagen fibres between the treatment groups. Significant differences (P < 0.01) were only identified for the volumes and areas of type 3 collagen, with treated animals also presenting lower mean values for the volume and area of elastic fibres compared to the control group.Discussion: The preponderance of type 3 immature collagen in the cutaneous wounds of animals treated with stem cells indicates active collagenase and greater fibroblastic activity, which is probably induced by stem cells. Diametrically, the identification of lower levels of elastic fibres in the cutaneous fragments treated with stem cells suggests that cell therapy does not contribute satisfactorily to elastogenesis. Previous reports suggested that mesenchymal stem cells may decrease elastin synthesis, and such a situation may have occurred in this study. The autologous mesenchymal stem cells increased the formation of collagen fibres in diabetic mice at the detriment of the formation of elastic fibres, thus suggesting active early collagen in the first 2 weeks of the cicatricial process.

Infection of grass carp reovirus induced the expressional suppression of pro-viral Fibulin-4 in host cells

Fibulin-4 is not only involved in connective tissue development and elastic fiber formation, but also plays critical neoplastic roles in tumor growth by activating Wnt/β-Catenin signaling in human. Recently, Fibulin-4 was shown to associate with grass carp reovirus (GCRV) outer capsid proteins and might relate to viral hemorrhagic disease in grass carp Ctenopharyngodon idella. Here, we monitored the expression pattern of Fibulin-4 during the infection course of GCRV at both translational and transcriptional levels, and found that Fibulin-4 was significantly suppressed upon the viral challenge in grass cap GCO cells. Over expression of Fibulin-4 was achieved by transduction of pEGFP-Fibulin-4 plasmids into GCO cells, which was confirmed by both Western blot and Real time RT-PCR analysis. In GCO cells with over-expression of Fibulin-4, significantly increase of viral protein synthesis and progeny virus production was detected. Our study indicated that Fibulin-4 displayed pro-viral function and was inhibited during viral challenge. Thus, repression of Fibulin-4 expression seemed to be involved in anti-viral response in grass carp Ctenopharyngodon idella.

Pentagalloyl glucose increases elastin deposition, decreases reactive oxygen species and matrix metalloproteinase activity in pulmonary fibroblasts under inflammatory conditions

Emphysema is characterized by degradation of lung alveoli that leads to poor airflow in lungs. Irreversible elastic fiber degradation by matrix metalloproteinases (MMPs) and reactive oxygen species (ROS) activity leads to loss of elasticity and drives the progression of this disease. We investigated if a polyphenol, pentagalloyl glucose (PGG) can increase elastin production in pulmonary fibroblasts. We also studied the effect of PGG treatment in reducing MMP activity and ROS levels in cells. We exposed rat pulmonary fibroblasts to two different types of inflammatory environments i.e., tumor necrosis factor-α (TNF-α) and cigarette smoke extract (CSE) to mimic the disease. Parameters like lysyl oxidase (LOX) and elastin gene expression, MMP-9 activity in the medium, lysyl oxidase (LOX) activity and ROS levels were studied to assess the effect of PGG on pulmonary fibroblasts. CSE inhibited lysyl oxidase (LOX) enzyme activity that resulted in a decreased elastin formation. Similarly, TNF-α treated cells showed less elastin in the cell layers. Both these agents caused increase in MMP activity and ROS levels in cells. However, when supplemented with PGG treatment along with these two inflammatory agents, we saw a significant increase in elastin deposition, reduction in both MMP activity and ROS levels. Thus PGG, which has anti-inflammatory, anti-oxidant properties coupled with its ability to aid in elastic fiber formation, can be a multifunctional drug to potentially arrest the progression of emphysema.

Serum proteome profiling in canine idiopathic dilated cardiomyopathy using TMT-based quantitative proteomics approach

Idiopathic dilated cardiomyopathy (iDCM) is a primary myocardial disorder with an unknown aetiology, characterized by reduced contractility and ventricular dilation of the left or both ventricles. Naturally occurring canine iDCM was used herein to identify serum proteomic signature of the disease compared to the healthy state, providing an insight into underlying mechanisms and revealing proteins with biomarker potential. To achieve this, we used high-throughput label-based quantitative LC-MS/MS proteomics approach and bioinformatics analysis of the in silico inferred interactome protein network created from the initial list of differential proteins. To complement the proteomic analysis, serum biochemical parameters and levels of know biomarkers of cardiac function were measured. Several proteins with biomarker potential were identified, such as inter-alpha-trypsin inhibitor heavy chain H4, microfibril-associated glycoprotein 4 and apolipoprotein A-IV, which were validated using an independent method (Western blotting) and showed high specificity and sensitivity according to the receiver operating characteristic curve analysis. Bioinformatics analysis revealed involvement of different pathways in iDCM, such as complement cascade activation, lipoprotein particles dynamics, elastic fibre formation, GPCR signalling and respiratory electron transport chain. SignificanceIdiopathic dilated cardiomyopathy is a severe primary myocardial disease of unknown cause, affecting both humans and dogs. This study is a contribution to the canine heart disease research by means of proteomic and bioinformatic state of the art analyses, following similar approach in human iDCM research. Importantly, we used serum as non-invasive and easily accessible biological source of information and contributed to the scarce data on biofluid proteome research on this topic. Bioinformatics analysis revealed biological pathways modulated in canine iDCM with potential of further targeted research. Also, several proteins with biomarker potential have been identified and successfully validated.

PKCε Increases Extracellular Elastin and Fibulin-5/DANCE in Dermal Fibroblasts

Background/Aims: In the earlier study, the selective PKCε activator DCP-LA increased elastic fibres in the dermis of HR-1 hairless mice. As a process of elastic fibre formation, tropoelastin, an elastin monomer, is secreted into the extracellular space. Secreted tropoelastin is delivered to the microfibrils by fibulin-5/developmental arteries and neural crest epidermal growth factor-like (DANCE) and undergoes self-association. Then, tropoelastin assembles around the microfibrils, growing into elastin and elastic fibres by lysyl oxidase (LOX)- or LOX-like (LOXL)-mediated cross-linking. The present study was conducted to understand the mechanism underlying DCP-LA-induced increase in elastin/elastic fibre. Methods: Western blotting, immunocytochemistory, and real-time reverse transcription-polymerase chain reaction (RT-PCR) were carried out in cultured human dermal fibroblasts. PKCε, mammalian target of rapamycin complex (mTOR), and p70 S6 kinase (S6K) were knocked-down by transfecting each siRNA. Results: DCP-LA increased elastin and fibulin-5/DANCE in a treatment time (6-24 h)- and a bell-shaped concentration (1 nM-1 µM)-dependent manner in the culture medium of human dermal fibroblasts. DCP-LA markedly increased elastic fibres in the extracellular space of cultured fibroblasts. DCP-LA-induced increase in extracellular elastin and fibulin-5/DANCE was abolished by a PKC inhibitor or knocking-down PKCε. DCP-LA did not affect expression of mRNAs for tropoelastin and fiblin-5/DANCE in cultured fibroblasts. DCP-LA-induced increase in extracellular elastin and fibulin-5/DANCE was not inhibited by the protein synthesis inhibitor cycloheximide or by knocking-down mTOR and S6K. DCP-LA never increased extracellular elastin in the presence of elastase, that breaks down elastin. An inhibitor of matrix metalloproteinase 9, that degrades multiple extracellular matrix components including elastin, had no effect on the basal levels and the DCP-LA-induced increase levels of extracellular elastin. Conclusion: The results of the present study indicate that PKCε, activated by DCP-LA, increases elastin and fibulin-5/DANCE in the extracellular space of cultured fibroblasts by the mechanism independent of transcriptional and translational modulation or inhibition of elastolysis.

Abstract 368: The Effect of Long-term Administration of PGE1 on the Morphological Change of Ductus Arteriosus

Introduction: Plostagrandin E 1 (PGE 1 ) is essential for maintaining the ductus arteriosus (DA) in ductal-dependent congenital heart disease. Recently, relatively long-term administration of PGE 1 became common, especially in patient with hypoplastic left heart syndrome (HLHS) . Staged Norwood approach which consists of bilateral pulmonary artery banding, PGE 1 infusion, and Norwood procedure beyond newborn period provided excellent survival benefit. However, microstructural changes of DA after long-term PGE 1 administration remain unknown. Therefore, we sought to investigate their features of DA after long-term PGE 1 administration using synchrotron based X-ray phase-contrast tomography (XPCT), a novel modality to inspect biological soft tissue, and pathological scrutiny including DA specific immunostaining. Methods: Seventeen DA tissues of HLHS were obtained during Norwood procedure. The median duration of PGE 1 was 48 days (Range 3-123). Radiographic microstructural analysis of DA was performed using X-ray phase contrast tomography at SPring-8 (Hyogo, Japan). Histological changes focused on elastic fiber and smooth muscle formation were evaluated by Elastica van Gieson staining, and expression of prostaglandin E2 receptor EP4 was evaluated by immunohistochemical analysis. Results: XPCT study showed a sclerotic changes of ductal media. There was a significant correlation between the duration of PGE 1 infusion and the mass density of ductal media (R: 0.723, p=0.001). Histological study showed that the duration of PGE1 infusion was positively correlated with the elastic fiber formation (R: 0.795, P=0.002), and negatively correlated with smooth muscle formation (R: -0.83, P<0.001). The EP4 expression was disappeared in all DA. Conclusion: Long-term administration of PGE 1 induced elastogenesis and density growth of the ductal media. In addition, downregulation of EP4 was observed. These results suggested that dosage of PGE 1 could be decreased after definite period of administration.

GABA promotes elastin synthesis and elastin fiber formation in normal human dermal fibroblasts (HDFs).

The multiple physiological effects of γ-aminobutyric acid (GABA) as a functional food component have been recently reported. We previously reported that GABA upregulated the expression of type I collagen in human dermal fibroblasts (HDFs), and that oral administration of GABA significantly increased skin elasticity. However, details of the regulatory mechanism still remain unknown. In this study, we further examined the effects of GABA on elastin synthesis and elastin fiber formation in HDFs. Real-time PCR indicated that GABA significantly increased the expression of tropoelastin transcript in a dose-dependent manner. Additionally, the expression of fibrillin-1, fibrillin-2, and fibulin-5/DANCE, but not lysyl oxidase and latent transforming factor-β-binding protein 4, were also significantly increased in HDFs. Finally, immunohistochemical analysis confirmed that treatment with GABA dramatically increased the formation of elastic fibers in HDFs. Taken together, our results showed that GABA improves skin elasticity in HDFs by upregulating elastin synthesis and elastin fiber formation.

Arterial graft with elastic layer structure grown from cells

Shortage of autologous blood vessel sources and disadvantages of synthetic grafts have increased interest in the development of tissue-engineered vascular grafts. However, tunica media, which comprises layered elastic laminae, largely determines arterial elasticity, and is difficult to synthesize. Here, we describe a method for fabrication of arterial grafts with elastic layer structure from cultured human vascular SMCs by periodic exposure to extremely high hydrostatic pressure (HP) during repeated cell seeding. Repeated slow cycles (0.002 Hz) between 110 and 180 kPa increased stress-fiber polymerization and fibronectin fibrillogenesis on SMCs, which is required for elastic fiber formation. To fabricate arterial grafts, seeding of rat vascular SMCs and exposure to the periodic HP were repeated alternatively ten times. The obtained medial grafts were highly elastic and tensile rupture strength was 1451 ± 159 mmHg, in which elastic fibers were abundantly formed. The patch medial grafts were sutured at the rat aorta and found to be completely patent and endothelialized after 2.5 months, although tubular medial constructs implanted in rats as interpositional aortic grafts withstood arterial blood pressure only in early acute phase. This novel organized self-assembly method would enable mass production of scaffold-free arterial grafts in vitro and have potential therapeutic applications for cardiovascular diseases.

Fibulin-4 reduces extracellular matrix production and suppresses chondrocyte differentiation via DKK1- mediated canonical Wnt/β-catenin signaling

Fibulin-4 is an extracellular matrix (ECM) protein implicated in connective tissue development and elastic fiber formation. However, little is known about the underlying function of Fibulin-4 in cartilage development. The aim of this study was to investigate the role and probable mechanism of Fibulin-4 stimulation in ECM production and chondrocyte differentiation. Fibulin-4 has been observed to be abnormally elevated and matrix metalloproteinases 13 (MMP13) level was highly expressed in human osteoarthritis (OA) chondrocytes. In the chondrogenic cell line ATDC5, Fibulin-4 stimulation profoundly inhibited the expression of ECM gene type II collagen (Col2a1), aggrecan (Acan), and type X collagen (Col10a1). Overexpression of Fibulin-4 attenuated the expression of master transcription factors Sox6, Sox9 and Runx2, but had no effect on the expression of Sox5. Additionally, Fibulin-4 stimulation activated canonical Wnt pathway by reducing the expression of Wnt inhibitor DKK1 but not Sost. Moreover, Fibulin-4 augmented the expression of Wnt/β-catenin signaling target genes like β-catenin and Wnt-3a as well as diminished GSK-3β activation, and DKK1 abolished the effect of Fibulin-4 on chondrocyte differentiation, suggesting that Fibulin-4 is an important regulator of ECM production and chondrocyte differentiation through DKK1-mediated Wnt/β-catenin signaling. Our study provides evidence of a previously unknown link between Fibulin-4 and the canonical Wnt/β-catenin pathway that may contribute to our understanding of the molecular mechanisms of OA.

Lysyl Oxidase Enhances the Deposition of Tropoelastin through the Catalysis of Tropoelastin Molecules on the Cell Surface.

The cross-linking of elastin by lysyl oxidase (LOX) family members is essential for the integrity and elasticity of elastic fibers, which play an important role in the characteristic resilience of various tissues. However, the temporal sequence of oxidation by LOX during elastic fiber formation is still incompletely understood. Here, we demonstrate that the cross-linking of tropoelastin molecules by LOX occurs concurrent with elastin deposition. Our data show that LOX deficiency or the inhibition of LOX enzyme activity leads to the loss of elastin deposition in skin fibroblast. Moreover, overexpression of LOX promotes the deposition and alignment of tropoelastin, whereas the addition of recombinant active-form of LOX in culture medium caused abnormal elastic fiber assembly. Immunoblotting and immunofluorescence show that LOX and tropoelastin are present together with fibronectin on the cell surface of preconfluent cultures. Further, fluorescence activated cell sorting (FACS) analysis for the localization of LOX on the cell surface reveals that the transfer of LOX to the extracellular space occurs in association with elastic fiber formation. In conclusion, our results support the view that LOX and tropoelastin are present on the cell surface and suggests the possibility that lysine oxidation by LOX precedes tropoelastin deposition onto microfibrils.

Reduction and fragmentation of elastic fibers in the skin of obese mice is associated with altered mRNA expression levels of fibrillin-1 and neprilysin

ABSTRACTAim of the study: Our previous research suggested that obesity induces structural fragility in the skin. Elastic fibers impart strength and elasticity. In this study, we determined whether elastic fibers decrease in the skin of obese mice. Materials and Methods: To confirm alterations in elastic fiber content due to obesity, we used spontaneously obese model mice (TSOD) and control mice (TSNO). Furthermore, to evaluate the elastin structure and gene expression dependent on the severity of obesity, an obesity-enhanced mouse model was developed by feeding a high fat diet to TSOD (TSOD-HF). Back skin samples were stained with hematoxylin and eosin and Elastica van Gieson for microscopic examination, and the samples were stained for immunohistochemical analysis of neprilysin. Gene expression levels were determined using a real-time PCR system. Results: The abundance of elastic fibers beneath the epidermis was remarkably reduced and fragmented in TSOD as compared with TSNO. Fibrillin-1 mRNA levels in TSOD were significantly suppressed compared with those in TSNO, whereas neprilysin mRNA levels and immunohistochemical expression in TSOD were significantly increased, as compared with those in TSNO. The reduction of elastic fibers was enhanced and the expression levels of elastic fiber formed factors were significantly suppressed in TSOD-HF, as compared with those in the TSOD. Conclusions: The abundance of elastic fibers was reduced and fragmented in obesity, suggesting that the reduction in elastic fibers is initially caused by increased neprilysin and decreased fibrillin-1 expression, which may inhibit formation and stabilization of elastic fibers, resulting in skin fragility in obesity.

Pathology and molecular mechanisms of coarctation of the aorta and its association with the ductus arteriosus.

Coarctation of the aorta (CoA) is defined as a congenital stenosis of the thoracic aorta and is one of the most common congenital cardiovascular diseases. Despite successful surgical treatment for CoA, arterial abnormalities, including refractory hypertension, aortic aneurysm, and proatherogenic phenotypic changes, frequently affect patients' quality of life. Emerging evidence from morphological and molecular biological investigations suggest that the area of CoA is characterized by phenotypic modulation of smooth muscle cells, intimal thickening, and impaired elastic fiber formation. These changes extend to the pre-and post-stenotic aorta and impair arterial elasticity. The aim of this review is to present current findings on the pathology and molecular mechanisms of vascular remodeling due to CoA. In particular, we will discuss the association between CoA and the ductus arteriosus since the most common site for the stenosis is in the proximity of the ductus arteriosus.

Raman microspectroscopy as a diagnostic tool for the non-invasive analysis of fibrillin-1 deficiency in the skin and in the in vitro skin models.

Mutations in building blocks of the fibrillin microfibril/ elastic fiber network manifest in disease conditions such as aneurysms, emphysema or lax skin. Understanding how structural changes induced by fibrillin-1 mutation impact the architecture of fibrillin microfibrils, which then translates into an altered activation state of targeted growth factors, represents a huge challenge in elucidating the genotype-phenotype correlations in connective tissue disorders such as Marfan syndrome. This study shows that Raman microspectroscopy is able to reveal structural changes in fibrillin-1 microfibrils and elastic fiber networks and to discriminate between normal and diseased networks in vivo and in vitro. Therefore Raman microspectroscopy may be utilized as a non-invasive and sensitive diagnostic tool to identify connective tissue disorders and monitor their disease progression.

Targeted Modulation of Tropoelastin Structure and Assembly.

Tropoelastin, as the monomer unit of elastin, assembles into elastic fibers that impart strength and resilience to elastic tissues. Tropoelastin is also widely used to manufacture versatile materials with specific mechanical and biological properties. The assembly of tropoelastin into elastic fibers or biomaterials is crucially influenced by key submolecular regions and specific residues within these domains. In this work, we identify the functional contributions of two rarely occurring negatively charged residues, glutamate 345 in domain 19 and glutamate 414 in domain 21, in jointly maintaining the native conformation of the tropoelastin hinge, bridge and foot regions. Alanine substitution of E345 and/or E414 variably alters the positioning and interactive accessibility of these regions, as illustrated by nanostructural studies and detected by antibody and cell probes. These structural changes are associated with a lower propensity for monomer coacervation, cross-linking into morphologically and functionally atypical hydrogels, and markedly impaired and abnormal elastic fiber formation. Our work indicates the crucial significance of both E345 and E414 residues in modulating specific local structure and higher-order assembly of human tropoelastin.

Elastin structure and its involvement in skin photoageing

Skin aging is a complex process that may be caused by factors that are intrinsic and extrinsic to the body. Ultraviolet (UV) radiation represents one of the main sources of skin damage over the years and characterizes a process known as photoaging. Among the changes that affect cutaneous tissue with age, the loss of elastic properties caused by changes in elastin production, increased degradation and/or processing produces a substantial impact on tissue esthetics and health. The occurrence of solar elastosis is one of the main markers of cutaneous photoaging and is characterized by disorganized and non-functional deposition of elastic fibers. The occurrence of UV radiation-induced alternative splicing of the elastin gene, which leads to inadequate synthesis of the proteins required for the correct assembly of elastic fibers, is a potential explanation for this phenomenon. Innovative studies have been fundamental for the elucidation of rarely explored photoaging mechanisms and have enabled the identification of effective therapeutic alternatives such as cosmetic products. This review addresses cutaneous photoaging and the changes that affect elastin in this process.

Characterization and mechanisms of photoageing-related changes in skin. Damages of basement membrane and dermal structures.

Sun-exposed skin is characterized by superficial changes such as wrinkles, sagging and pigmentary changes, and also many internal changes in the structure and function of epidermis, basement membrane (BM) and dermis. These changes (so-called photoageing) are predominantly induced by the ultraviolet (UV) component of sunlight. Epidermis of UV-irradiated skin produced several enzymes such as matrix metalloproteinases (MMPs), urinary plasminogen activator (uPA)/plasmin and heparanase, which degrade dermal collagen fibres and elastic fibres in the dermis, and components of epidermal BM. The BM at the dermal-epidermal junction (DEJ) controls dermal-epidermal signalling and plays an important role in the maintenance of a healthy epidermis and dermis. BM is repetitively damaged in sun-exposed skin compared with unexposed skin, leading to epidermal and dermal deterioration and accelerated skin ageing. UV exposure also induces an increase in vascular endothelial growth factor (VEGF), an angiogenic factor, while thrombospondin-1 (TSP-1), an anti-angiogenic factor, is decreased; these changes induce angiogenesis in papillary dermis with increased migration of elastase-positive leucocytes, leading to dermal elastic fibre damage. Elastic fibres, such as oxytalan fibres in papillary dermis, are associated with not only skin resilience, but also skin surface texture, and elastic fibre formation by fibroblasts is facilitated by increased expression of fibulin-5. Thus, induction of fibulin-5 expression is a damage-repair mechanism, and fibulin-5 is an early marker of photoaged skin. UV-induced skin damage is cumulative and leads to premature ageing of skin. However, appropriate daily skincare may ameliorate photoageing by inhibiting processes causing damage and enhancing repair processes.

Long-lasting and bioactive hyaluronic acid-hydroxyapatite composite hydrogels for injectable dermal fillers: Physical properties and in vivo durability.

Hyaluronic acid (HAc)-hydroxyapatite (HAp) composite hydrogels were developed to improve the biostability and bioactivity of HAc for dermal filler applications. Two kinds of HAc-HAp composite fillers were generated: HAcmicroHAp and HAc-nanoHAp composites. HAc-microHAp was fabricated by mixing HAp microspheres with HAc hydrogels, and HAc-nanoHAp was made by in situ precipitation of nano-sized HAp particles in HAc hydrogels. Emphasis was placed on the effect of HAp on the durability and bioactivity of the fillers. Compared with the pure HAc filler, all of the HAc-HAp composite fillers exhibited significant improvements in volumetric maintenance based on in vivo tests owing to their reduced water content and higher degree of biointegration between the filler and surrounding tissues. HAc-HAp composite fillers also showed noticeable enhancement in dermis recovery, promoting collagen and elastic fiber formation. Based on their long-lasting durability and bioactivity, HAc-HAp composite fillers have great potential for soft tissue augmentation with multifunctionality.