The collαgen III fibril has a "flexi-rod" structure of flexible sequences interspersed with rigid bioactive domains including two with hemostatic roles

Impact of vascular Ehlers-Danlos Syndrome-associated Gly substitutions on structure, function, and mechanics using bacterial collagen

Vascular Ehlers-Danlos syndrome (vEDS) arises from mutations in collagen-III, a major structural component of the extracellular matrix (ECM) in vascularized tissues, including blood vessels. Fibrillar collagens form a triple-helix that is characterized by a canonical (Gly-X-Y)n sequence. The substitution of another amino acid for Gly within this conserved repeating sequence is associated with several hereditary connective tissue disorders, including vEDS. The clinical severity of vEDS depends on the identity of the substituted amino acid and its location. In this study, we engineered recombinant bacterial collagen-like proteins (CLPs) with previously reported Gly→X (X=Ser or Arg) vEDS substitutions within the integrin-binding site. Employing a combination of biophysical techniques, enzymatic digestion assays, integrin binding affinity assays, and computational modeling, we assessed the impact of Gly→X substitutions on structure, stability, function, and mechanical properties. While constructs with Ser or Arg substitutions maintained a triple-helix structure, Arg substitution significantly reduced global thermal stability, heightened susceptibility to trypsin digestion, and altered integrin α2-inserted (α2I) domain binding. Molecular dynamics (MD) simulations also demonstrated distinct effects of different Gly substitutions on the triple-helix structure - Arg substitutions induced notable bulging at the substitution site and disrupted interchain hydrogen bonds compared to Ser substitutions. Additionally, steered MD simulations revealed that Arg substitution led to a significant decrease in the Young's modulus of the triple-helix. Bacterial CLPs have proved to be a powerful model for studying the underlying mechanisms of vEDS-causing mutations in collagen-III. Serine and arginine substitutions differentially perturb cell-matrix interactions and ECM in a manner consistent with clinical vEDS severity.

Echocardiographic Assessment in Patients with Vascular Ehlers-Danlos Syndrome: Insights from an Unexplored Field

INTRODUCTION

Vascular Ehlers-Danlos syndrome (vEDS) is an inherited connective tissue disorder characterized by arterial fragility. Celiprolol is a β1-adrenoceptor antagonist with partial β2 agonist activity that has been shown to reduce rates of vascular events in this setting, though the underlying mechanisms are not yet fully understood. Moreover, very few echocardiographic data are available in patients with vEDS.

AIM

To perform a comprehensive echocardiographic assessment of a cohort of patients with vEDS with or without celiprolol therapy compared with healthy subjects.

METHODS

Twenty patients with genetically confirmed diagnosis of vEDS followed at our Institution (University Hospital of Brescia, Italy) were divided into two groups according to whether or not they were on celiprolol therapy at the maximum recommended dose (400 mg daily) for at least 12 months. Both groups were compared to 10 healthy individuals matched for sex, age, body mass index (BMI), and office blood pressure (BP) values. Each participant underwent transthoracic echocardiography with tissue Doppler analysis (TDI) for a comprehensive evaluation of cardiac structure and function.

RESULTS

Mean age was 35 years and mean BMI was 21.6 kg/m2. Female sex was prevalent (60%). Left ventricular (LV) internal diameter values tended to be lower in patients with untreated vEDS than in healthy controls (4.33 vs 4.74 cm, respectively), though this difference was not statistically significant. Similar data were observed for LV mass index (56.9 vs 68.6 g/m2), stroke volume (56.6 vs 71.6 mL), and E/A ratio (1.26 vs 1.66), whereas an opposite trend was observed for e' lateral (13.2 vs 12.2 cm/s). No statistically significant difference was found between groups in terms of other parameters of LV mass, systolic and diastolic function. A normal LV geometry was found in all the cases. Indices of mechano-energetic efficiency and ventricular-arterial coupling were also similar between groups. No patient presented with aortic root dilation, mitral valve prolapse, valve insufficiency of more than mild degree, or valve stenosis of any degree.

CONCLUSION

Our study suggests that patients with vEDS have normal cardiac mass and geometry, as well as normal systolic and diastolic function. Celiprolol therapy does not seem to significantly influence such aspects. Compared with vascular imaging, less stringent follow-up with echocardiography seems reasonable in this setting. Future studies with prospective design should confirm these aspects.

Preparation and characterization of a novel humanized collagen III with repeated fragments of Gly300-Asp329

Recombinant human collagens have attracted intensive interest in the past two decades, demonstrating considerable potential in medicine, tissue engineering, and cosmetics. Several humanized recombinant collagens have been produced, exhibiting similar characteristics as the native species. To get insight into the structural and bioactive properties of different parts of collagen, in this study, the segment of Gly300-Asp329 of type III collagen was first adopted and repeated 18 times to prepare a novel recombinant collagen (named rhCLA). RhCLA was successfully expressed in E. coli, and a convenient separation procedure was established through reasonably combining alkaline precipitation and acid precipitation, yielding crude rhCLA with a purity exceeding 90%. Additionally, a polishing purification step utilizing cation exchange chromatography was developed, achieving rhCLA purity surpassing 98% and an overall recovery of approximately 120 mg/L culture. Simultaneously, the contents of endotoxin, nucleic acids, and host proteins were reduced to extremely low levels. This fragmented type III collagen displayed a triple-helical structure and gel-forming capability at low temperatures. Distinct fibrous morphology was also observed through TEM analysis. In cell experiments, rhCLA exhibited excellent biocompatibility and cell adhesion properties. These results provide valuable insights for functional studies of type III collagen and a reference approach for the large-scale production of recombinant collagens.

Molecular Phenotyping and Mechanisms of Myocardial Fibrosis in Advanced Chronic Kidney Disease

Key Points

Myocardial fibrosis in hearts from patients with CKD is characterized by increased trimeric tensile collagen type I and decreased elastic collagen type III compared with hearts from hypertensive or healthy donors, suggesting a unique fibrotic phenotype. Myocardial fibrosis in CKD is driven by alterations in extracellular matrix proteostasis, including dysregulation of metalloproteinases and cross-linking enzymes. CKD-associated mineral stressors uniquely induce a fibronectin-independent mechanism of fibrillogenesis characterized by formation of trimeric collagen compared with proinflammatory/fibrotic cytokines.

Background

Myocardial fibrosis is a major life-limiting problem in CKD. Despite this, the molecular phenotype and metabolism of collagen fibrillogenesis in fibrotic hearts of patients with advanced CKD have been largely unstudied.

Methods

We analyzed explanted human left ventricular (LV) heart tissues in a three-arm cross-sectional cohort study of deceased donor patients on hemodialysis (HD, n =18), hypertension with preserved renal function (HTN, n =8), and healthy controls (CON, n =17), ex vivo . RNA-seq and protein analysis was performed on human donor hearts and cardiac fibroblasts treated with mineral stressors (high phosphate and high calcium). Further mechanistic studies were performed using primary cardiac fibroblasts, in vitro treated with mineral stressors, proinflammatory and profibrotic cytokines.

Results

Of the 43 donor participants, there was no difference in age (P > 0.2), sex (P > 0.8), or body mass index (P > 0.1) between the groups. Hearts from the HD group had extensive fibrosis (P < 0.01). All LV tissues expressed only the trimeric form of collagen type I. HD hearts expressed increased collagen type I (P < 0.03), elevated collagen type I:III ratio (P < 0.05), and decreased MMP1 (P < 0.05) and MMP2 (P < 0.05). RNA-seq revealed no significant differential gene expression of extracellular matrix proteins of interest in HD hearts, but there was significant upregulation of LH2, periostin, α -SMA, and TGF-β 1 gene expression in mineral stressor–treated cardiac fibroblasts. Both mineral stressors (P < 0.009) and cytokines (P < 0.03) increased collagen type I:III ratio. Mineral stressors induced trimeric collagen type I, but cytokine treatment induced only dimeric collagen type I in cardiac fibroblasts. Mineral stressors downregulated fibronectin (P < 0.03) and MMP2 zymogen (P < 0.01) but did not significantly affect expression of periostin, MMP1, or cross-linking enzymes. TGF-β upregulated fibronectin (P < 0.01) and periostin (P < 0.02) only.

Conclusions

Myocardial fibrosis in advanced CKD hearts is characterized by increased trimeric collagen type I and dysregulated collagen metabolism, and is differentially regulated by components of uremia.

Bowel Perforation in Vascular Ehlers-Danlos Syndrome: Case Report and Comprehensive Review

INTRODUCTION

Ehlers-Danlos syndromes (EDS) comprise a rare variety of genetic disorders, affecting all types of collagen. Herein, we describe a case of the vascular type of EDS, with coexisting segmental absence of intestinal musculature, while simultaneously performing a narrative review of the existing literature.

CASE PRESENTATION

A 23-year-old male patient with a history of multiple abdominal operations due to recurrent bowel perforations and the presence of a high-output enterocutaneous fistula was admitted to our surgical department for further evaluation and treatment. After detailed diagnostic testing, the diagnosis of vascular-type EDS (vEDS) was made and a conservative therapeutic approach was adopted. In addition, a comprehensive review of the international literature was carried out by applying the appropriate search terms.

RESULTS

The diagnosis of vEDS was molecularly confirmed by means of genetic testing. The patient was treated conservatively, with parenteral nutrition and supportive methods. Thirty-four cases of bowel perforation in vEDS have been reported so far. Interestingly, this case is the second one ever to report co-existence of vEDS with Segmental Absence of Intestinal Musculature.

CONCLUSIONS

Establishing the diagnosis of vEDS promptly is of vital significance in order to ensure that patients receive appropriate treatment. Due to initial non-specific clinical presentation, EDS should always be included in the differential diagnoses of young patients with unexplained perforations of the gastrointestinal tract.

Machine learning-based prediction of candidate gene biomarkers correlated with immune infiltration in patients with idiopathic pulmonary fibrosis

Objective

This study aimed to identify candidate gene biomarkers associated with immune infiltration in idiopathic pulmonary fibrosis (IPF) based on machine learning algorithms.

Methods

Microarray datasets of IPF were extracted from the Gene Expression Omnibus (GEO) database to screen for differentially expressed genes (DEGs). The DEGs were subjected to enrichment analysis, and two machine learning algorithms were used to identify candidate genes associated with IPF. These genes were verified in a validation cohort from the GEO database. Receiver operating characteristic (ROC) curves were plotted to assess the predictive value of the IPF-associated genes. The cell-type identification by estimating relative subsets of RNA transcripts (CIBERSORT) algorithm was used to evaluate the proportion of immune cells in IPF and normal tissues. Additionally, the correlation between the expression of IPF-associated genes and the infiltration levels of immune cells was examined.

Results

A total of 302 upregulated and 192 downregulated genes were identified. Functional annotation, pathway enrichment, Disease Ontology and gene set enrichment analyses revealed that the DEGs were related to the extracellular matrix and immune responses. COL3A1, CDH3, CEBPD, and GPIHBP1 were identified as candidate biomarkers using machine learning algorithms, and their predictive value was verified in a validation cohort. Additionally, ROC analysis revealed that the four genes had high predictive accuracy. The infiltration levels of plasma cells, M0 macrophages and resting dendritic cells were higher and those of resting natural killer (NK) cells, M1 macrophages and eosinophils were lower in the lung tissues of patients with IPF than in those of healthy individuals. The expression of the abovementioned genes was correlated with the infiltration levels of plasma cells, M0 macrophages and eosinophils.

Conclusion

COL3A1, CDH3, CEBPD, and GPIHBP1 are candidate biomarkers of IPF. Plasma cells, M0 macrophages and eosinophils may be involved in the development of IPF and may serve as immunotherapeutic targets in IPF.

The Effects of Aging on the Intramuscular Connective Tissue

The intramuscular connective tissue plays a critical role in maintaining the structural integrity of the muscle and in providing mechanical support. The current study investigates age-related changes that may contribute to passive stiffness and functional impairment of skeletal muscles. Variations in the extracellular matrix in human quadriceps femoris muscles in 10 young men, 12 elderly males and 16 elderly females, and in the hindlimb muscles of 6 week old, 8 month old and 2 year old C57BL/6J male mice, were evaluated. Picrosirius red, Alcian blue and Weigert Van Gieson stainings were performed to evaluate collagen, glycosamynoglycans and elastic fibers. Immunohistochemistry analyses were carried out to assess collagen I, collagen III and hyaluronan. The percentage area of collagen was significantly higher with aging (p < 0.01 in humans, p < 0.001 in mice), mainly due to an increase in collagen I, with no differences in collagen III (p > 0.05). The percentage area of elastic fibers in the perimysium was significantly lower (p < 0.01) in elderly men, together with a significant decrease in hyaluronan content both in humans and in mice. No significant differences were detected according to gender. The accumulation of collagen I and the lower levels of hyaluronan and elastic fibers with aging could cause a stiffening of the muscles and a reduction of their adaptability.

Using sequence data to predict the self-assembly of supramolecular collagen structures

Collagen fibrils are the major constituents of the extracellular matrix, which provides structural support to vertebrate connective tissues. It is widely assumed that the superstructure of collagen fibrils is encoded in the primary sequences of the molecular building blocks. However, the interplay between large-scale architecture and small-scale molecular interactions makes the ab initio prediction of collagen structure challenging. Here, we propose a model that allows us to predict the periodic structure of collagen fibers and the axial offset between the molecules, purely on the basis of simple predictive rules for the interaction between amino acid residues. With our model, we identify the sequence-dependent collagen fiber geometries with the lowest free energy and validate the predicted geometries against the available experimental data. We propose a procedure for searching for optimal staggering distances. Finally, we build a classification algorithm and use it to scan 11 data sets of vertebrate fibrillar collagens, and predict the periodicity of the resulting assemblies. We analyzed the experimentally observed variance of the optimal stagger distances across species, and find that these distances, and the resulting fibrillar phenotypes, are evolutionary well preserved. Moreover, we observed that the energy minimum at the optimal stagger distance is broad in all cases, suggesting a further evolutionary adaptation designed to improve the assembly kinetics. Our periodicity predictions are not only in good agreement with the experimental data on collagen molecular staggering for all collagen types analyzed, but also for synthetic peptides. We argue that, with our model, it becomes possible to design tailor-made, periodic collagen structures, thereby enabling the design of novel biomimetic materials based on collagen-mimetic trimers.

Cosmetic Potential of a Recombinant 50 kDa Protein

Collagen and its derivative proteins have been widely used as a major component for cosmetic formulations as a natural ingredient and moisturizer. Most commercially available collagens are animal-derived collagen type I and other forms of collagen, such as type III collagen, are far less prevalent in animals, making extraction and purification extremely difficult and expensive. Here, we report the production of a 50 kDa protein produced in yeast that is 100% identical to the N-terminus of the human type III collagen. This recombinant protein has a larger molecular weight than most incumbent recombinant collagen proteins available for personal care applications. We report the industrialization of both the fermentation and purification processes to produce a final recombinant protein product. This final protein product was shown to be safe for general applications to human skin and compatible with common formulation protocols, including ethanol-based formulations. This recombinant collagen type III protein was also shown to uniquely stimulate both collagen type I and type III production and secretion by primary human dermal fibroblasts. The unique combination of biostimulation, compatibility with beauty product formulations and demonstrated commercial production, make this novel recombinant type III collagen a good candidate for broad application in the cosmetics industry.

Four decades in the making: Collagen III and mechanisms of vascular Ehlers Danlos Syndrome

Vascular Ehlers Danlos (vEDS) syndrome is a severe multi-systemic connective tissue disorder characterized by risk of dissection and rupture of the arteries, gastro-intestinal tract and gravid uterus. vEDS is caused by mutations in COL3A1, that encodes the alpha 1 chain of type III collagen, which is a major extracellular matrix component of the vasculature and hollow organs. The first causal mutations were identified in the 1980s but progress in our understanding of the pathomolecular mechanisms has been limited. Recently, the application of more refined animal models combined with global omics approaches has yielded important new insights both in terms of disease mechanisms and potential for therapeutic intervention. However, it is also becoming apparent that vEDS is a complex disorder in terms of its molecular disease mechanisms with a poorly understood allelic and mechanistic heterogeneity. In this brief review we will focus our attention on the disease mechanisms of COL3A1 mutations and vEDS, and recent progress in therapeutic approaches using animal models.

Platelet derived growth factor-A (Pdgf-a) gene transfer modulates scar composition and improves left ventricular function after myocardial infarction

BACKGROUND

Novel therapies that can limit or reverse damage caused by myocardial infarction (MI) could ease the increasing burden of heart failure. In this regard Platelet Derived Growth Factor (PDGF) has been previously shown to contribute to cardiac repair after MI. Here, we use a rodent model of MI and recombinant adeno-associated virus 9 (rAAV9)-mediated gene transfer to overexpress Pdgf-a in the injured heart and assess its therapeutic potential.

METHODS AND RESULTS

Sprague Dawley rats underwent temporary occlusion of the left anterior descending coronary artery, followed immediately by systemic delivery of 1 × 10^11 vector genomes of either rAAV9 Pdgf-a or rAAV9 Empty vector (control). At day 28 post-MI echocardiography showed significantly improved left ventricular (LV) function (fractional shortening) after rAAV9 Pdgf-a (0.394 ± 0.019%) treatment vs control (0.304 ± 0.018%). Immunohistochemical analysis demonstrated significantly increased capillary and arteriolar density in the infarct border zone of rAAV9 Pdgf-a treated hearts together with a significant reduction in infarct scar size (rAAV9 Pdgf-a 6.09 ± 0.94% vs Empty 12.45 ± 0.92%). Western blot and qPCR analyses confirmed overexpression of PDGF-A and showed upregulation of smooth muscle alpha actin (Acta2), collagen type III alpha 1 (Col3a1) and lysyl oxidase (Lox) genes in rAAV9 Pdgf-a treated infarcts.

CONCLUSION

Overexpression of Pdgf-a in the post-MI heart can modulate scar composition and improve LV function. Our study highlights the potential of rAAV gene transfer of Pdgf-a as a cardio-reparative therapy.

Oxidative Stress and Vascular Damage in the Context of Obesity: The Hidden Guest

The vascular system plays a central role in the transport of cells, oxygen and nutrients between different regions of the body, depending on the needs, as well as of metabolic waste products for their elimination. While the structure of different components of the vascular system varies, these structures, especially those of main arteries and arterioles, can be affected by the presence of different cardiovascular risk factors, including obesity. This vascular remodeling is mainly characterized by a thickening of the media layer as a consequence of changes in smooth muscle cells or excessive fibrosis accumulation. These vascular changes associated with obesity can trigger functional alterations, with endothelial dysfunction and vascular stiffness being especially common features of obese vessels. These changes can also lead to impaired tissue perfusion that may affect multiple tissues and organs. In this review, we focus on the role played by perivascular adipose tissue, the activation of the renin-angiotensin-aldosterone system and endoplasmic reticulum stress in the vascular dysfunction associated with obesity. In addition, the participation of oxidative stress in this vascular damage, which can be produced in the perivascular adipose tissue as well as in other components of the vascular wall, is updated.

Collagen Structure-Function Mapping Informs Applications for Regenerative Medicine

Type I collagen, the predominant protein of vertebrates, assembles into fibrils that orchestrate the form and function of bone, tendon, skin, and other tissues. Collagen plays roles in hemostasis, wound healing, angiogenesis, and biomineralization, and its dysfunction contributes to fibrosis, atherosclerosis, cancer metastasis, and brittle bone disease. To elucidate the type I collagen structure-function relationship, we constructed a type I collagen fibril interactome, including its functional sites and disease-associated mutations. When projected onto an X-ray diffraction model of the native collagen microfibril, data revealed a matrix interaction domain that assumes structural roles including collagen assembly, crosslinking, proteoglycan (PG) binding, and mineralization, and the cell interaction domain supporting dynamic aspects of collagen biology such as hemostasis, tissue remodeling, and cell adhesion. Our type III collagen interactome corroborates this model. We propose that in quiescent tissues, the fibril projects a structural face; however, tissue injury releases blood into the collagenous stroma, triggering exposure of the fibrils' cell and ligand binding sites crucial for tissue remodeling and regeneration. Applications of our research include discovery of anti-fibrotic antibodies and elucidating their interactions with collagen, and using insights from our angiogenesis studies and collagen structure-function model to inform the design of super-angiogenic collagens and collagen mimetics.

Granzyme B Degraded Type IV Collagen Products in Serum Identify Melanoma Patients Responding to Immune Checkpoint Blockade

Simple Summary

Novel biomarkers that can identify melanoma patients responding to immune checkpoint inhibitor therapy are urgently needed. As high T-cell infiltration and low fibrotic activity are associated with response, we aimed to examine the serum biomarker potential of granzyme B degraded type IV collagen (C4G) products in combination with the fibrosis biomarker PRO-C3. We found that high C4G combined with low PRO-C3 has the potential to identify patients responding to immune checkpoint inhibitor therapy suggesting that these biomarkers may provide a non-invasive tool for patient selection and therapeutic decision-making in the future.

Abstract

A T-cell permissive tumor microenvironment, characterized by the presence of activated T cells and low fibrotic activity is crucial for response to immune checkpoint inhibitors (ICIs). Granzyme B has been shown to promote T-cell migration through the basement membrane by the degradation of type IV collagen. In this study, we evaluated the biomarker potential of measuring granzyme B-mediated degradation of type IV collagen (C4G) in combination with a fibroblast activation biomarker (PRO-C3) non-invasively for identifying metastatic melanoma patients responding to the ICI ipilimumab. A monoclonal antibody was generated against C4G and used to develop a competitive electro-chemiluminescence immunoassay. C4G and PRO-C3 were measured in pretreatment serum from metastatic melanoma patients (n = 54). The C4G assay was found specific for a granzyme B-generated neo-epitope on type IV collagen. The objective response rate (ORR) was 2.6-fold higher (18% vs. 7%) in patients with high C4G levels (>25th percentile) vs. low levels (≤25th percentile). Likewise, high C4G levels at baseline were associated with longer overall survival (OS) (log-rank, p = 0.040, and hazard ratio (HR) = 0.48, 95%CI: 0.24–0.98, p = 0.045). Combining high C4G with low PRO-C3 correlated with improved OS with a median OS of 796 days vs. 273 days (p = 0.0003) and an HR of 0.30 (95%CI: 0.15–0.60, p = 0.0006). In conclusion, these results suggest that high granzyme B degraded type IV collagen (C4G) combined with low PRO-C3 quantified non-invasively has the potential to identify the responders to ICI therapy.

Regenerative Scar-Free Skin Wound Healing

IMPACT STATEMENT

Millions of people every year develop scars in response to skin injuries after surgery, trauma, or burns with significant undesired physical and psychological effects. This review provides an update on engineering strategies for scar-free wound healing and discusses the role of different cell types, growth factors, cytokines, and extracellular components in regenerative wound healing. The use of pro-regenerative matrices combined with engineered cells with less intrinsic potential for fibrogenesis is a promising strategy for achieving scar-free skin tissue regeneration.

Molecular underpinnings of integrin binding to collagen-mimetic peptides containing vascular Ehlers-Danlos syndrome-associated substitutions

Collagens carry out critical extracellular matrix (ECM) functions by interacting with numerous cell receptors and ECM components. Single glycine substitutions in collagen III, which predominates in vascular walls, result in vascular Ehlers-Danlos syndrome (vEDS), leading to arterial, uterine, and intestinal rupture and an average life expectancy of <50 years. Collagen interactions with integrin α₂β₁ are vital for platelet adhesion and activation; however, how these interactions are impacted by vEDS-associated mutations and by specific amino acid substitutions is unclear. Here, we designed collagen-mimetic peptides (CMPs) with previously reported Gly → Xaa (Xaa = Ala, Arg, or Val) vEDS substitutions within a high-affinity integrin α₂β₁-binding motif, GROGER. We used these peptides to investigate, at atomic-level resolution, how these amino acid substitutions affect the collagen III-integrin α₂β₁ interaction. Using a multitiered approach combining biological adhesion assays, CD, NMR, and molecular dynamics (MD) simulations, we found that these substitutions differentially impede human mesenchymal stem cell spreading and integrin α₂-inserted (α₂I) domain binding to the CMPs and were associated with triple-helix destabilization. Although an Ala substitution locally destabilized hydrogen bonding and enhanced mobility, it did not significantly reduce the CMP-integrin interactions. MD simulations suggested that bulkier Gly → Xaa substitutions differentially disrupt the CMP-α₂I interaction. The Gly → Arg substitution destabilized CMP-α₂I side-chain interactions, and the Gly → Val change broke the essential Mg²⁺ coordination. The relationship between the loss of functional binding and the type of vEDS substitution provides a foundation for developing potential therapies for managing collagen disorders.

From genetics to response to injury: vascular smooth muscle cells in aneurysms and dissections of the ascending aorta

Vascular smooth muscle cells (vSMCs) play a crucial role in both the pathogenesis of Aneurysms and Dissections of the ascending thoracic aorta (TAAD) in humans and in the associated adaptive compensatory responses, since thrombosis and inflammatory processes are absent in the majority of cases. Aneurysms and dissections share numerous characteristics, including aetiologies and histopathological alterations: vSMC disappearance, medial areas of mucoid degeneration, and extracellular matrix (ECM) breakdown. Three aetiologies predominate in TAAD in humans: (i) genetic causes in heritable familial forms, (ii) an association with bicuspid aortic valves, and (iii) a sporadic degenerative form linked to the aortic aging process. Genetic forms include mutations in vSMC genes encoding for molecules of the ECM or the TGF-β pathways, or participating in vSMC tone. On the other hand, aneurysms and dissections, whatever their aetiologies, are characterized by an increase in wall permeability leading to transmural advection of plasma proteins which could interact with vSMCs and ECM components. In this context, blood-borne plasminogen appears to play an important role, because its outward convection through the wall is increased in TAAD, and it could be converted to active plasmin at the vSMC membrane. Active plasmin can induce vSMC disappearance, proteolysis of adhesive proteins, activation of MMPs and release of TGF-β from its ECM storage sites. Conversely, vSMCs could respond to aneurysmal biomechanical and proteolytic injury by an epigenetic phenotypic switch, including constitutional overexpression and nuclear translocation of Smad2 and an increase in antiprotease and ECM protein synthesis. In contrast, such an epigenetic phenomenon is not observed in dissections. In this context, dysfunction of proteins involved in vSMC tone are interesting to study, particularly in interaction with plasma protein transport through the wall and TGF-β activation, to establish the relationship between these dysfunctions and ECM proteolysis.

Atypical COL3A1 variants (glutamic acid to lysine) cause vascular Ehlers-Danlos syndrome with a consistent phenotype of tissue fragility and skin hyperextensibility

PURPOSE

The Ehlers-Danlos syndromes (EDS) are a group of rare inherited connective tissue disorders. Vascular EDS (vEDS) is caused by pathogenic variants in COL3A1, most frequently glycine substitutions. We describe the phenotype of the largest series of vEDS patients with glutamic acid to lysine substitutions (Glu>Lys) in COL3A1, which were all previously considered to be variants of unknown significance.

METHODS

Clinical and molecular data for seven families with three different Glu>Lys substitutions in COL3A1 were analyzed.

RESULTS

These Glu>Lys variants were reclassified from variants of unknown significance to either pathogenic or likely pathogenic in accordance with American College of Medical Genetics and Genomics guidelines. All individuals with these atypical variants exhibited skin hyperextensibility as seen in individuals with classical EDS and classical-like EDS and evidence of tissue fragility as seen in individuals with vEDS.

CONCLUSION

The clinical data demonstrate the overlap between the different EDS subtypes and underline the importance of next-generation sequencing gene panel analysis. The three different Glu>Lys variants point toward a new variant type in COL3A1 causative of vEDS, which has consistent clinical features. This is important knowledge for COL3A1 variant interpretation. Further follow-up data are required to establish the severity of tissue fragility complications compared with patients with other recognized molecular causes of vEDS.

Solubilized eggshell membrane supplies a type III collagen-rich elastic dermal papilla

Signs of aging in facial skin correlate with lifespan and chronic disease; however, the health of aging skin has not been extensively studied. In healthy young skin, the dermis forms a type III collagen-rich dermal papilla, where capillary vessels supply oxygen and nutrients to basal epidermal cells. Chicken eggshell membranes (ESMs) have been used as traditional medicines to promote skin wound healing in Asian countries for many years. Previously, we designed an experimental system in which human dermal fibroblasts (HDFs) were cultured on a dish with a solubilized ESM (S-ESM) bound to an artificial phosphorylcholine polymer; we found that genes that promoted the health of the papillary dermis, such as those encoding type III collagen, were induced in the S-ESM environment. The present study found that a gel with a ratio of 20% type III/80% type I collagen, similar to that of the baby skin, resulted in a higher elasticity than 100% type I collagen (p < 0.05) and that HDFs in the gel showed high mitochondrial activity. Thus, we decided to perform further evaluations to identify the effects of S-ESM on gene expression in the skin of hairless mice and found a significant increase of type III collagen in S-ESM. Picrosirius Red staining showed that type III collagen significantly increased in the papillary dermis after S-ESM treatment. Moreover, S-ESM application significantly improved human arm elasticity and reduced facial wrinkles. ESMs may have applications in extending lifespan by reducing the loss of tissue elasticity through the increase of type III collagen.

Transcriptome analysis of skin fibroblasts with dominant negative COL3A1 mutations provides molecular insights into the etiopathology of vascular Ehlers-Danlos syndrome

Vascular Ehlers-Danlos syndrome (vEDS) is a dominantly inherited connective tissue disorder caused by mutations in the COL3A1 gene that encodes type III collagen (COLLIII), which is the major expressed collagen in blood vessels and hollow organs. The majority of disease-causing variants in COL3A1 are glycine substitutions and in-frame splice mutations in the triple helix domain that through a dominant negative effect are associated with the severe clinical spectrum potentially lethal of vEDS, characterized by fragility of soft connective tissues with arterial and organ ruptures.

To shed lights into molecular mechanisms underlying vEDS, we performed gene expression profiling in cultured skin fibroblasts from three patients with different structural COL3A1 mutations. Transcriptome analysis revealed significant changes in the expression levels of several genes involved in maintenance of cell redox and endoplasmic reticulum (ER) homeostasis, COLLs folding and extracellular matrix (ECM) organization, formation of the proteasome complex, and cell cycle regulation. Protein analyses showed that aberrant COLLIII expression is associated with the disassembly of many structural ECM constituents, such as fibrillins, EMILINs, and elastin, as well as with the reduction of the proteoglycans perlecan, decorin, and versican, all playing an important role in the vascular system. Furthermore, the altered distribution of the ER marker protein disulfide isomerase PDI and the strong reduction of the COLLs-modifying enzyme FKBP22 are consistent with the disturbance of ER-related homeostasis and COLLs biosynthesis and post-translational modifications, indicated by microarray analysis. Our findings add new insights into the pathophysiology of this severe vascular disorder, since they provide a picture of the gene expression changes in vEDS skin fibroblasts and highlight that dominant negative mutations in COL3A1 also affect post-translational modifications and deposition into the ECM of several structural proteins crucial to the integrity of soft connective tissues.

Revealing Accessibility of Cryptic Protein Binding Sites within the Functional Collagen Fibril

Fibrillar collagens are the most abundant proteins in the extracellular matrix. Not only do they provide structural integrity to all of the connective tissues in the human body, but also their interactions with multiple cell receptors and other matrix molecules are essential to cell functions, such as growth, repair, and cell adhesion. Although specific binding sequences of several receptors have been determined along the collagen monomer, processes by which collagen binding partners recognize their binding sites in the collagen fibril, and the critical driving interactions, are poorly understood. The complex molecular assembly of bundled triple helices within the collagen fibril makes essential ligand binding sites cryptic or hidden from the molecular surface. Yet, critical biological processes that require collagen ligands to have access to interaction sites still occur. In this contribution, we will discuss the molecular packing of the collagen I fibril from the perspective of how collagen ligands access their known binding regions within the fibril, and we will present our analysis of binding site accessibility from the fibril surface. Understanding the basis of these interactions at the atomic level sets the stage for developing drug targets against debilitating collagen diseases and using collagen as drug delivery systems and new biomaterials.