Heparin-II domain of fibronectin is a vascular endothelial growth factor-binding domain: enhancement of VEGF biological activity by a singular growth factor/matrix protein synergism

The role of extracellular matrix in angiogenesis: Beyond adhesion and structure

While the extracellular matrix (ECM) has long been recognized for its structural contributions, anchoring cells for adhesion, providing mechanical support, and maintaining tissue integrity, recent efforts have elucidated its dynamic, reciprocal, and diverse properties on angiogenesis. The ECM modulates angiogenic signaling and mechanical transduction, influences the extent and degree of receptor activation, controls cellular behaviors, and serves as a reservoir for bioactive macromolecules. Collectively, these factors guide the formation, maturation, and stabilization of a functional vascular network. This review aims to shed light on the versatile roles of the ECM in angiogenesis, transcending its traditional functions as a mere structural material. We will explore its engagement and synergy in signaling modulation, interactions with various angiogenic factors, and highlight its importance in both health and disease. By capturing the essence of the ECM's diverse functionalities, we highlight the significance in the broader context of vascular biology, enabling the design of novel biomaterials to engineer vascularized tissues and their potential therapeutic implications.

Simulation of Soluble and Bound VEGF-stimulated in vitro Capillary-like Network Formation on Deformed Substrate

Capillary plexus cultivation is crucial in tissue engineering and regenerative medicine. Theoretical simulations have been conducted to supplement the expensive experimental works. However, the mechanisms connecting mechanical and chemical stimuli remained undefined, and the functions of the different VEGF forms in the culture environment were still unclear. In this paper, we developed a hybrid model for simulating short-term in vitro capillary incubations. We used the Cellular Potts model to predict individual cell migration, morphology change, and continuum mechanics to quantify biogel deformation and VEGF transport dynamics. By bridging the mechanical regulation and chemical stimulation in the model, the results showed good agreement between the predicted network topology and experiments, in which elongated cells connected, forming the network cords and round cells gathered, creating cobblestone-like aggregates. The results revealed that the capillary-like networks could develop in high integrity only when the mechanical and chemical couplings worked adequately, with the cell morphology and haptotaxis driven by the soluble and bound forms of VEGF, respectively, functioning simultaneously.

Formation of vascular-like structures using a chemotaxis-driven multiphase model

We propose a continuum model for pattern formation, based on the multiphase model framework, to explore in vitro cell patterning within an extracellular matrix (ECM). We demonstrate that, within this framework, chemotaxis-driven cell migration can lead to the formation of cell clusters and vascular-like structures in 1D and 2D respectively. The influence on pattern formation of additional mechanisms commonly included in multiphase tissue models, including cell-matrix traction, contact inhibition, and cell-cell aggregation, are also investigated. Using sensitivity analysis, the relative impact of each model parameter on the simulation outcomes is assessed to identify the key parameters involved. Chemoattractant-matrix binding is further included, motivated by previous experimental studies, and found to reduce the spatial scale of patterning to within a biologically plausible range for capillary structures. Key findings from the in-depth parameter analysis of the 1D models, both with and without chemoattractant-matrix binding, are demonstrated to translate well to the 2D model, obtaining vascular-like cell patterning for multiple parameter regimes. Overall, we demonstrate a biologically-motivated multiphase model capable of generating long-term pattern formation on a biologically plausible spatial scale both in 1D and 2D, with applications for modelling in vitro vascular network formation.

Shaping Oncogenic Microenvironments: Contribution of Fibronectin

The extracellular matrix (ECM) is a complex network of proteins and glycans, dynamically remodeled and specifically tailored to the structure/function of each organ. The malignant transformation of cancer cells is determined by both cell intrinsic properties, such as mutations, and extrinsic variables, such as the mixture of surrounding cells in the tumor microenvironment and the biophysics of the ECM. During cancer progression, the ECM undergoes extensive remodeling, characterized by disruption of the basal lamina, vascular endothelial cell invasion, and development of fibrosis in and around the tumor cells resulting in increased tissue stiffness. This enhanced rigidity leads to aberrant mechanotransduction and further malignant transformation potentiating the de-differentiation, proliferation and invasion of tumor cells. Interestingly, this fibrotic microenvironment is primarily secreted and assembled by non-cancerous cells. Among them, the cancer-associated fibroblasts (CAFs) play a central role. CAFs massively produce fibronectin together with type I collagen. This review delves into the primary interactions and signaling pathways through which fibronectin can support tumorigenesis and metastasis, aiming to provide critical molecular insights for better therapy response prediction.

Interactions between neural cells and blood vessels in central nervous system development

The sophisticated function of the central nervous system (CNS) is largely supported by proper interactions between neural cells and blood vessels. Accumulating evidence has demonstrated that neurons and glial cells support the formation of blood vessels, which in turn, act as migratory scaffolds for these cell types. Neural progenitors are also involved in the regulation of blood vessel formation. This mutual interaction between neural cells and blood vessels is elegantly controlled by several chemokines, growth factors, extracellular matrix, and adhesion molecules such as integrins. Recent research has revealed that newly migrating cell types along blood vessels repel other preexisting migrating cell types, causing them to detach from the blood vessels. In this review, we discuss vascular formation and cell migration, particularly during development. Moreover, we discuss how the crosstalk between blood vessels and neurons and glial cells could be related to neurodevelopmental disorders.

Evaluation of GHK peptide-heparin interactions in multifunctional liposomal covering

Small biospecific peptides with defined chemical structure and cellular responses are promising alternatives to full-length therapeutic proteins. Identification of these peptides solely or in combination with other bioactive factors and determination of their targets are of substantial interest in current drug delivery research. This study is aimed at the development of new liposomal formulations of ECM-derived GHK peptide known for its multiple regeneration-related activities but poorly recognized cellular targets. In situ association of membranotropic GHK derivative with unilamellar liposomes was performed to prepare GHK-modified liposomes with defined properties. According to DLS, the GHK component on the liposomal surface interacted with heparin in a specific manner compared to other polysaccharides and RGD counterpart, whereas ITC analysis of such interactions was complicated. The results provide a useful tool for screening of bio-interactions of synthetic peptide-presenting liposomes by the DLS technique. They were also employed to produce a multi-functional nanosized GHK-heparin covering for liposomes. The resulting composite liposomes possessed low size dispersity, increased anionic charge, and mechanical rigidity. The heparin component significantly promoted the accumulation of GHK-modified liposomes in 3T3 fibroblasts so that the composite liposomes exhibited the highest cell-penetrating activity. Furthermore, the latter formulation stimulated cell proliferation and strongly inhibited ROS production and GSH depletion under oxidative stress conditions. Together, the results support that cell-surface glycosaminoglycans can be involved in GHK-mediated liposomal delivery, which can be further greatly enhanced by association with heparin. The composite liposomes with GHK-heparin covering can be considered as an advanced GHK-based formulation for therapeutic and cosmeceutical applications.

The collagen matrix regulates the survival and function of pancreatic islets

The extracellular matrix (ECM) provides an appropriate microenvironment for many kinds of cells, including pancreatic cells. Collagens are the most abundant components of the ECM. Type I, IV, V and VI collagen has been detected in pancreatic islets, and each type plays important role in the proliferation, survival, function and differentiation of pancreatic cells. In some cases, collagens show behaviours similar to those of growth factors and regulate the biological behaviour of β cells by binding with certain growth factors, including IGFs, EGFs and FGFs. The transcriptional coactivator YAP/TAZ has been widely recognised as a mechanosensor that senses changes in the physical characteristics of the ECM and inhibition of YAP/TAZ enhances insulin production and secretion. Type 1 diabetes mellitus (T1DM) is an autoimmune disease characterised by the destruction of insulin-producing β cells. The crosstalk between collagens and immune cells plays a key role in the development and differentiation of immune cells. Further, Supplementation with collagens during islet transplantation is a promising strategy for improving the quality of the islets. But, excessive collagen deposition results in pancreatic fibrosis and pancreatic carcinoma. Targeting inhibit Piezo, autophagy or IL-6 may reduce excessive collagen deposition-induced pancreatic fibrosis and pancreatic carcinoma. This review provides insights into the treatment of T1DM to prolong life expectancy and provides the potential targets for treating collagen deposition-induced pancreatic fibrosis and pancreatic carcinoma.

Spatial-temporal order-disorder transition in angiogenic NOTCH signaling controls cell fate specification

Angiogenesis is a morphogenic process resulting in the formation of new blood vessels from pre-existing ones, usually in hypoxic micro-environments. The initial steps of angiogenesis depend on robust differentiation of oligopotent endothelial cells into the Tip and Stalk phenotypic cell fates, controlled by NOTCH-dependent cell-cell communication. The dynamics of spatial patterning of this cell fate specification are only partially understood. Here, by combining a controlled experimental angiogenesis model with mathematical and computational analyses, we find that the regular spatial Tip-Stalk cell patterning can undergo an order-disorder transition at a relatively high input level of a pro-angiogenic factor VEGF. The resulting differentiation is robust but temporally unstable for most cells, with only a subset of presumptive Tip cells leading sprout extensions. We further find that sprouts form in a manner maximizing their mutual distance, consistent with a Turing-like model that may depend on local enrichment and depletion of fibronectin. Together, our data suggest that NOTCH signaling mediates a robust way of cell differentiation enabling but not instructing subsequent steps in angiogenic morphogenesis, which may require additional cues and self-organization mechanisms. This analysis can assist in further understanding of cell plasticity underlying angiogenesis and other complex morphogenic processes.

Construction of an Exudative Age-Related Macular Degeneration Diagnostic and Therapeutic Molecular Network Using Multi-Layer Network Analysis, a Fuzzy Logic Model, and Deep Learning Techniques: Are Retinal and Brain Neurodegenerative Disorders Related?

Neovascular age-related macular degeneration (nAMD) is a leading cause of irreversible visual impairment in the elderly. The current management of nAMD is limited and involves regular intravitreal administration of anti-vascular endothelial growth factor (anti-VEGF). However, the effectiveness of these treatments is limited by overlapping and compensatory pathways leading to unresponsiveness to anti-VEGF treatments in a significant portion of nAMD patients. Therefore, a system view of pathways involved in pathophysiology of nAMD will have significant clinical value. The aim of this study was to identify proteins, miRNAs, long non-coding RNAs (lncRNAs), various metabolites, and single-nucleotide polymorphisms (SNPs) with a significant role in the pathogenesis of nAMD. To accomplish this goal, we conducted a multi-layer network analysis, which identified 30 key genes, six miRNAs, and four lncRNAs. We also found three key metabolites that are common with AMD, Alzheimer's disease (AD) and schizophrenia. Moreover, we identified nine key SNPs and their related genes that are common among AMD, AD, schizophrenia, multiple sclerosis (MS), and Parkinson's disease (PD). Thus, our findings suggest that there exists a connection between nAMD and the aforementioned neurodegenerative disorders. In addition, our study also demonstrates the effectiveness of using artificial intelligence, specifically the LSTM network, a fuzzy logic model, and genetic algorithms, to identify important metabolites in complex metabolic pathways to open new avenues for the design and/or repurposing of drugs for nAMD treatment.

A bronchial gene signature specific for severe COPD that is retained in the nose

Introduction

A subset of COPD patients develops advanced disease with severe airflow obstruction, hyperinflation and extensive emphysema. We propose that the pathogenesis in these patients differs from mild-moderate COPD and is reflected by bronchial gene expression. The aim of the present study was to identify a unique bronchial epithelial gene signature for severe COPD patients.

Methods

We obtained RNA sequencing data from bronchial brushes from 123 ex-smokers with severe COPD, 23 with mild-moderate COPD and 23 non-COPD controls. We identified genes specific to severe COPD by comparing severe COPD to non-COPD controls, followed by removing genes that were also differentially expressed between mild-moderate COPD and non-COPD controls. Next, we performed a pathway analysis on these genes and evaluated whether this signature is retained in matched nasal brushings.

Results

We identified 219 genes uniquely differentially expressed in severe COPD. Interaction network analysis identified VEGFA and FN1 as the key genes with the most interactions. Genes were involved in extracellular matrix regulation, collagen binding and the immune response. Of interest were 10 genes (VEGFA, DCN, SPARC, COL6A2, MGP, CYR61, ANXA6, LGALS1, C1QA and C1QB) directly connected to fibronectin 1 (FN1). Most of these genes were lower expressed in severe COPD and showed the same effect in nasal brushings.

Conclusions

We found a unique severe COPD bronchial gene signature with key roles for VEGFA and FN1, which was retained in the upper airways. This supports the hypothesis that severe COPD, at least partly, comprises a different pathology and supports the potential for biomarker development based on nasal brushes in COPD.

Estrogen Actions in Placental Vascular Morphogenesis and Spiral Artery Remodeling: A Comparative View between Humans and Mice

Estrogens, mainly 17β-estradiol (E2), play a critical role in reproductive organogenesis, ovulation, and fertility via estrogen receptors. E2 is also a well-known regulator of utero-placental vascular development and blood-flow dynamics throughout gestation. Mouse and human placentas possess strikingly different morphological configurations that confer important reproductive advantages. However, the functional interplay between fetal and maternal vasculature remains similar in both species. In this review, we briefly describe the structural and functional characteristics, as well as the development, of mouse and human placentas. In addition, we summarize the current knowledge regarding estrogen actions during utero-placental vascular morphogenesis, which includes uterine angiogenesis, the control of trophoblast behavior, spiral artery remodeling, and hemodynamic adaptation throughout pregnancy, in both mice and humans. Finally, the estrogens that are present in abnormal placentation are also mentioned. Overall, this review highlights the importance of the actions of estrogens in the physiology and pathophysiology of placental vascular development.

Landscape of Well-Coordinated Fracture Healing in a Mouse Model Using Molecular and Cellular Analysis

The success of fracture healing relies on overlapping but coordinated cellular and molecular events. Characterizing an outline of differential gene regulation throughout successful healing is essential for identifying crucial phase-specific markers and may serve as the basis for engineering these in challenging healing situations. This study analyzed the healing progression of a standard closed femoral fracture model in C57BL/6N (age = 8 weeks) wild-type male mice. The fracture callus was assessed across various days post fracture (D = days 0, 3, 7, 10, 14, 21, and 28) by microarray, with D0 serving as a control. Histological analyses were carried out on samples from D7 until D28 to support the molecular findings. Microarray analysis revealed a differential regulation of immune response, angiogenesis, ossification, extracellular matrix regulation, mitochondrial and ribosomal genes during healing. In-depth analysis showed differential regulation of mitochondrial and ribosomal genes during the initial phase of healing. Furthermore, the differential gene expression showed an essential role of Serpin Family F Member 1 over the well-known Vascular Endothelial Growth Factor in angiogenesis, especially during the inflammatory phase. The significant upregulation of matrix metalloproteinase 13 and bone sialoprotein from D3 until D21 asserts their importance in bone mineralization. The study also shows type I collagen around osteocytes located in the ossified region at the periosteal surface during the first week of healing. Histological analysis of matrix extracellular phosphoglycoprotein and extracellular signal-regulated kinase stressed their roles in bone homeostasis and the physiological bone-healing process. This study reveals previously unknown and novel candidates, that could serve as a target for specific time points in healing and to remedy cases of impaired healing.

Macrophage-derived GPNMB trapped by fibrotic extracellular matrix promotes pulmonary fibrosis

Pulmonary fibrosis (PF) is a form of progressive lung disease characterized by chronic inflammation and excessive extracellular matrix (ECM) deposition. However, the protein changes in fibrotic ECM during PF and their contribution to fibrosis progression are unclear. Here we show that changes in expression of ECM components and ECM remodeling had occurred in silica-instilled mice. The macrophage-derived glycoprotein nonmetastatic melanoma protein B (GPNMB) captured by fibrotic ECM may activate resident normal fibroblasts around the fibrotic foci. Functional experiments demonstrated the activation of fibroblasts in fibrotic ECM, which was alleviated by GPNMB-neutralizing antibodies or macrophage deletion in the ECM of silica-instilled mice. Moreover, the Serpinb2 expression level was increased in fibroblasts in fibrotic ECM, and the expression of CD44 was increased in silica-instilled mice. In conclusion, macrophage-derived GPNMB is trapped by fibrotic ECM during transport and may activate fibroblasts via the CD44/Serpinb2 pathway, thus leading to the further development of fibrosis.

Beyond target cell death - Granzyme serine proteases in health and disease

Granzymes are a family of small (∼32 kDa) serine proteases with a range of substrate specificities that are stored in, and released from, the cytoplasmic secretory vesicles ('granules') of cytotoxic T lymphocytes and natural killer cells. Granzymes are not digestive proteases but finely tuned processing enzymes that target their substrates in specific ways to activate various signalling pathways, or to inactivate viral proteins and other targets. Great emphasis has been placed on studying the pro-apoptotic functions of granzymes, which largely depend on their synergy with the pore-forming protein perforin, on which they rely for penetration into the target cell cytosol to access their substrates. While a critical role for granzyme B in target cell apoptosis is undisputed, both it and the remaining granzymes also influence a variety of other biological processes (including important immunoregulatory functions), which are discussed in this review. This includes the targeting of many extracellular as well as intracellular substrates, and can also lead to deleterious outcomes for the host if granzyme expression or function are dysregulated or abrogated. A final important consideration is that granzyme repertoire, biochemistry and function vary considerably across species, probably resulting from the pressures applied by viruses and other pathogens across evolutionary time. This has implications for the interpretation of granzyme function in preclinical models of disease.

Crosstalk between Blood Vessels and Glia during the Central Nervous System Development

The formation of proper blood vessel patterns in the central nervous system (CNS) is crucial to deliver oxygen and nutrient to neurons efficiently. At the same time, neurons must be isolated from the outer blood circulation by a specialized structure, the blood-brain barrier (BBB), to maintain the microenvironment of brain parenchyma for the survival of neurons and proper synaptic transmission. To develop this highly organized structure, glial cells, a major component of the brain, have been reported to play essential roles. In this review, the crosstalk between the macroglia, including astrocytes and oligodendrocytes, and endothelial cells during the development of CNS will be discussed. First, the known roles of astrocytes in neuro-vascular unit and its development, and then, the requirements of astrocytes for BBB development and maintenance are shown. Then, various genetic and cellular studies revealing the roles of astrocytes in the growth of blood vessels by providing a scaffold, including laminins and fibronectin, as well as by secreting trophic factors, including vascular endothelial growth factor (VEGF) and transforming growth factor-β (TGF-β) are introduced. Finally, the interactions between oligodendrocyte progenitors and blood vessels are overviewed. Although these studies revealed the necessity for proper communication between glia and endothelial cells for CNS development, our knowledge about the detailed cellular and molecular mechanisms for them is still limited. The questions to be clarified in the future are also discussed.

Molecular Advances in MAFLD—A Link between Sphingolipids and Extracellular Matrix in Development and Progression to Fibrosis

Metabolic-Associated Fatty Liver Disease (MAFLD) is a major cause of liver diseases globally and its prevalence is expected to grow in the coming decades. The main cause of MAFLD development is changed in the composition of the extracellular matrix (ECM). Increased production of matrix molecules and inflammatory processes lead to progressive fibrosis, cirrhosis, and ultimately liver failure. In addition, increased accumulation of sphingolipids accompanied by increased expression of pro-inflammatory cytokines in the ECM is closely related to lipogenesis, MAFLD development, and its progression to fibrosis. In our work, we will summarize all information regarding the role of sphingolipids e.g., ceramide and S1P in MAFLD development. These sphingolipids seem to have the most significant effect on macrophages and, consequently, HSCs which trigger the entire cascade of overproduction matrix molecules, especially type I and III collagen, proteoglycans, elastin, and also tissue inhibitors of metalloproteinases, which as a result cause the development of liver fibrosis.

The interactions between integrin α5β1 of liver cancer cells and fibronectin of fibroblasts promote tumor growth and angiogenesis

Hepatocellular carcinoma (HCC) progression is closely related to pathological fibrosis, which involves heterotypic intercellular interactions (HIIs) between liver cancer cells and fibroblasts. Here, we studied them in a direct coculture model, and identified fibronectin from fibroblasts and integrin-α₅β₁ from liver cancer cells as the primary responsible molecules utilizing CRISPR/Cas9 gene-editing technology. Coculture led to the formation of 3D multilayer microstructures, and obvious fibronectin remodeling was caused by upregulated integrin-α₅β₁, which greatly promoted cell growth in 3D microstructures. Integrin-α₅ was more sensitive and specific than integrin-β₁ in this process. Subsequent mechanistic exploration revealed the activation of integrin-Src-FAK, AKT and ERK signaling pathways. Importantly, the growth-promoting effect of HIIs was verified in a xenograft tumor model, in which more blood vessels were observed in bigger tumors derived from the coculture group than that derived from monocultured groups. Hence, we conducted triculture by introducing human umbilical vein endothelial cells, which aligned to and differentiated along multilayer microstructures in an integrin-α₅β₁ dependent manner. Furthermore, fibronectin, integrin-α₅, and integrin-β₁ were upregulated in 52 HCC tumors, and fibronectin was related to microvascular invasion. Our findings identify fibronectin, integrin-α₅, and integrin-β₁ as tumor microenvironment-related targets and provide a basis for combination targeted therapeutic strategies for future HCC treatment.

Functionalized 3D scaffolds for engineering the hematopoietic niche

Hematopoietic stem cells (HSCs) reside in a subzone of the bone marrow (BM) defined as the hematopoietic niche where, via the interplay of differentiation and self-renewal, they can give rise to immune and blood cells. Artificial hematopoietic niches were firstly developed in 2D in vitro cultures but the limited expansion potential and stemness maintenance induced the optimization of these systems to avoid the total loss of the natural tissue complexity. The next steps were adopted by engineering different materials such as hydrogels, fibrous structures with natural or synthetic polymers, ceramics, etc. to produce a 3D substrate better resembling that of BM. Cytokines, soluble factors, adhesion molecules, extracellular matrix (ECM) components, and the secretome of other niche-resident cells play a fundamental role in controlling and regulating HSC commitment. To provide biochemical cues, co-cultures, and feeder-layers, as well as natural or synthetic molecules were utilized. This review gathers key elements employed for the functionalization of a 3D scaffold that demonstrated to promote HSC growth and differentiation ranging from 1) biophysical cues, i.e., material, topography, stiffness, oxygen tension, and fluid shear stress to 2) biochemical hints favored by the presence of ECM elements, feeder cell layers, and redox scavengers. Particular focus is given to the 3D systems to recreate megakaryocyte products, to be applied for blood cell production, whereas HSC clinical application in such 3D constructs was limited so far to BM diseases testing.

Targeting Fibronectin to Overcome Remyelination Failure in Multiple Sclerosis: The Need for Brain- and Lesion-Targeted Drug Delivery

Multiple sclerosis (MS) is a neuroinflammatory and neurodegenerative disease with unknown etiology that can be characterized by the presence of demyelinated lesions. Prevailing treatment protocols in MS rely on the modulation of the inflammatory process but do not impact disease progression. Remyelination is an essential factor for both axonal survival and functional neurological recovery but is often insufficient. The extracellular matrix protein fibronectin contributes to the inhibitory environment created in MS lesions and likely plays a causative role in remyelination failure. The presence of the blood-brain barrier (BBB) hinders the delivery of remyelination therapeutics to lesions. Therefore, therapeutic interventions to normalize the pathogenic MS lesion environment need to be able to cross the BBB. In this review, we outline the multifaceted roles of fibronectin in MS pathogenesis and discuss promising therapeutic targets and agents to overcome fibronectin-mediated inhibition of remyelination. In addition, to pave the way for clinical use, we reflect on opportunities to deliver MS therapeutics to lesions through the utilization of nanomedicine and discuss strategies to deliver fibronectin-directed therapeutics across the BBB. The use of well-designed nanocarriers with appropriate surface functionalization to cross the BBB and target the lesion sites is recommended.

Cardiac differentiation of human pluripotent stem cells using defined extracellular matrix proteins reveals essential role of fibronectin

Research and therapeutic applications using human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs) require robust differentiation strategies. Efforts to improve hPSC-CM differentiation have largely overlooked the role of extracellular matrix (ECM). The present study investigates the ability of defined ECM proteins to promote hPSC cardiac differentiation. Fibronectin (FN), laminin-111, and laminin-521 enabled hPSCs to attach and expand. However, only addition of FN promoted cardiac differentiation in response to growth factors Activin A, BMP4, and bFGF in contrast to the inhibition produced by laminin-111 or laminin-521. hPSCs in culture produced endogenous FN which accumulated in the ECM to a critical level necessary for effective cardiac differentiation. Inducible shRNA knockdown of FN prevented Brachyury+ mesoderm formation and subsequent hPSC-CM generation. Antibodies blocking FN binding integrins α4β1 or αVβ1, but not α5β1, inhibited cardiac differentiation. Furthermore, inhibition of integrin-linked kinase led to a decrease in phosphorylated AKT, which was associated with increased apoptosis and inhibition of cardiac differentiation. These results provide new insights into defined matrices for culture of hPSCs that enable production of FN-enriched ECM which is essential for mesoderm formation and efficient cardiac differentiation.

Granzyme B in Epithelial Barrier Dysfunction and Related Skin Diseases

The predominant function of the skin is to serve as a barrier - to protect against external insults and to prevent water loss. Junctional and structural proteins in the stratum corneum, the outermost layer of the epidermis, are critical to the integrity of the epidermal barrier as it balances ongoing outward migration, differentiation, and desquamation of keratinocytes in the epidermis. As such, epidermal barrier function is highly susceptible to upsurges of proteolytic activity in the stratum corneum and epidermis. Granzyme B is a serine protease scarce in healthy tissues but present at high levels in tissues encumbered by chronic inflammation. Discovered in the 1980s, Granzyme B is currently recognized for its intracellular roles in immune cell-mediated targeted apoptosis as well as extracellular roles in inflammation, chronic injuries, tissue remodeling, and processing of cytokines, matrix proteins, and autoantigens. Increasing evidence has emerged in recent years supporting a role for Granzyme B in promoting barrier dysfunction in the epidermis by direct cleavage of barrier proteins and eliciting immunoreactivity. Likewise, Granzyme B contributes to impaired epithelial function of the airways, retina, gut and vessels. In the present review, the role of Granzyme B in cutaneous epithelial dysfunction is discussed in the context of specific conditions with an overview of underlying mechanisms as well as utility of current experimental and therapeutic inhibitors.

A Nanocoating Co-Localizing Nitric Oxide and Growth Factor onto Individual Endothelial Cells Reveals Synergistic Effects on Angiogenesis

The delivery of nitric oxide (NO)-an intrinsic cellular signaling molecule-is promising for disease treatment, in particular to vascular diseases, due to its endothelial-derived inherent nature. The limited diffusion distance of labile NO prompts researchers to develop various carriers and targeting methods for specific sites. In contrast to the apoptotic effect of NO, such as anticancer, delivering low NO concentration at the desired targeting area is still intricate in a physiological environment. In this study, the layer-by-layer assembled nanocoating is leveraged to develop a direct NO delivery platform to individual endothelial cells (ECs). NO can be localized to individual ECs via S-nitrosothiol-bound polyacrylic acid which is a polymer directly providing an endothelial-like constant level of NO. To increase angiogenic activation along with NO, VEGF is additionally applied to specific receptors on the cell surface. Notably, the survival and proliferation of ECs are significantly increased by a synergistic effect of NO and VEGF co-localized via nanocoating. Furthermore, the nanocoating remarkably promoted cell migration and tubule formation-prerequisites of angiogenesis. The proposed unique technology based on nanocoating demonstrates great potential for conferring desired angiogenic functions to individual ECs through efficient NO delivery.

Pathogenesis of glaucoma: Extracellular matrix dysfunction in the trabecular meshwork-A review

The trabecular meshwork regulates aqueous humour outflow from the anterior chamber of the eye. It does this by establishing a tunable outflow resistance, defined by the interplay between cells and their extracellular matrix (ECM) milieu, and the molecular interactions between ECM proteins. During normal tissue homeostasis, the ECM is remodelled and trabecular cell behaviour is modified, permitting increased aqueous fluid outflow to maintain intraocular pressure (IOP) within a relatively narrow physiological pressure. Dysfunction in the normal homeostatic process leads to increased outflow resistance and elevated IOP, which is a primary risk factor for glaucoma. This review delineates some of the changes in the ECM that lead to gross as well as some more subtle changes in the structure and function of the ECM, and their impact on trabecular cell behaviour. These changes are discussed in the context of outflow resistance and glaucoma.

Basement membrane proteins improve human islet survival in hypoxia: Implications for islet inflammation

Enzymatic digestion of the pancreas during islet isolation is associated with disintegration of the islet basement membrane (IBM) that can cause reduction of functional and morphological islet integrity. Attempts to re-establish IBM by coating the surface of culture vessels with various IBM proteins (IBMP) have resulted in loss of islet phenotype and function. This study investigated the capability of Collagen-IV, Laminin-521 and Nidogen-1, utilised as single or combined media supplements, to protect human islets cultured in hypoxia. When individually supplemented to media, all IBMP significantly improved islet survival and in-vitro function, finally resulting in as much as a two-fold increase of islet overall survival. In contrast, combining IBMP enhanced the production of chemokines and reactive oxygen species diminishing all positive effects of individually added IBMP. This impact was concentration-dependent and concerned nearly all parameters of islet integrity. Predictive extrapolation of these findings to data from 116 processed human pancreases suggests that more than 90% of suboptimal pancreases could be rescued for clinical islet transplantation increasing the number of transplantable preparations from actual 25 to 40 when adding Nidogen-1 to pretransplant culture. This study suggests that media supplementation with essential IBMP protects human islets from hypoxia. Amongst those, certain IBMP may be incompatible when combined or applied at higher concentrations. STATEMENT OF SIGNIFICANCE: Pancreatic islet transplantation is a minimally-invasive treatment that can reverse type 1 diabetes in certain patients. It involves infusing of insulin-producing cell-clusters (islets) from donor pancreases. Unfortunately, islet extraction is associated with damage of the islet basement membrane (IBM) causing reduced islet function and cell death. Attempts to re-establish the IBM by coating the surface of culture vessels with IBM proteins (IBMP) have been unsuccessful. Instead, we dissolved the most relevant IBM components Collagen-IV, Laminin-521 and Nidogen-1 in media routinely used for clinical islet culture and transplantation. We found human islet survival and function was substantially improved by IBMP, particularly Nidogen-1, when exposed to a hypoxic environment as found in vivo. We also investigated IBMP combinations. Our present findings have important clinical implications.

Mechanics of 3D Cell-Hydrogel Interactions: Experiments, Models, and Mechanisms

Hydrogels are highly water-swollen molecular networks that are ideal platforms to create tissue mimetics owing to their vast and tunable properties. As such, hydrogels are promising cell-delivery vehicles for applications in tissue engineering and have also emerged as an important base for ex vivo models to study healthy and pathophysiological events in a carefully controlled three-dimensional environment. Cells are readily encapsulated in hydrogels resulting in a plethora of biochemical and mechanical communication mechanisms, which recapitulates the natural cell and extracellular matrix interaction in tissues. These interactions are complex, with multiple events that are invariably coupled and spanning multiple length and time scales. To study and identify the underlying mechanisms involved, an integrated experimental and computational approach is ideally needed. This review discusses the state of our knowledge on cell-hydrogel interactions, with a focus on mechanics and transport, and in this context, highlights recent advancements in experiments, mathematical and computational modeling. The review begins with a background on the thermodynamics and physics fundamentals that govern hydrogel mechanics and transport. The review focuses on two main classes of hydrogels, described as semiflexible polymer networks that represent physically cross-linked fibrous hydrogels and flexible polymer networks representing the chemically cross-linked synthetic and natural hydrogels. In this review, we highlight five main cell-hydrogel interactions that involve key cellular functions related to communication, mechanosensing, migration, growth, and tissue deposition and elaboration. For each of these cellular functions, recent experiments and the most up to date modeling strategies are discussed and then followed by a summary of how to tune hydrogel properties to achieve a desired functional cellular outcome. We conclude with a summary linking these advancements and make the case for the need to integrate experiments and modeling to advance our fundamental understanding of cell-matrix interactions that will ultimately help identify new therapeutic approaches and enable successful tissue engineering.

Clinical and Pathological Correlations in Chronic Venous Disease

BACKGROUND

Chronic Venous Disease (CVD) has a high prevalence in the western world. Varicose veins (VVs) are the main signs of this disease that is characterized by important pathological vessel wall changes. The aim of this study is to correlate the main histopathological abnormalities with related clinical issues of CVD.

METHODS

A cohort of patients with VVs scheduled for open surgical treatment namely stab avulsion of VVs was recruited. Subsequently, venous tissue from stab avulsion was collected in order to evaluate the following biomarkers: Vascular-Endothelial Growth Factor (VEGF), Protein Gene Product 9.5 (PGP 9.5), Fibronectin (FN), and Matrix Metalloproteinase-9 (MMP-9). The Clinical-Etiology-Anatomy-Pathophysiology (CEAP) criteria were used to classify CVD.

RESULTS

Fourteen tissue fragments were processed for histological and immunohistochemical studies. Of these, 43% were from CEAP C2 patients, 36% from CEAP C3 patients, and 21% from CEAP C4 patients. CEAP Class C2 had few to moderate structures positive to VEGF; occasional structures positive to Fibronectin, numerous structures positive to MMP9, few to moderate structures positive to PGP 9.5. CEAP Class C3 had moderate structures positive to VEGF; few to moderate structures positive to Fibronectin; many structures positive to MMP9; few to moderate structures positive to PGP 9.5. CEAP Class C4 had numerous structures positive to VEGF; numerous structures positive to Fibronectin; abundant structures positive to MMP-9; few structures positive to PGP 9.5.

CONCLUSIONS

In this study, positive VEGF, FN, and MMP-9 structures were found with increasing trends in relation to the disease staging. VEGF and FN are associated with a progressive increase from C2 to C4. The MMP-9 marker has an important positivity even at early stage of the disease, being higher in CEAP C4 patients. PGP 9.5 decreases in CEAP C4 patients and this is concordant to decreased vein wall innervation.

Connecting different heart diseases through intercellular communication

Well-orchestrated intercellular communication networks are pivotal to maintaining cardiac homeostasis and to ensuring adaptative responses and repair after injury. Intracardiac communication is sustained by cell-cell crosstalk, directly via gap junctions (GJ) and tunneling nanotubes (TNT), indirectly through the exchange of soluble factors and extracellular vesicles (EV), and by cell-extracellular matrix (ECM) interactions. GJ-mediated communication between cardiomyocytes and with other cardiac cell types enables electrical impulse propagation, required to sustain synchronized heart beating. In addition, TNT-mediated organelle transfer has been associated with cardioprotection, whilst communication via EV plays diverse pathophysiological roles, being implicated in angiogenesis, inflammation and fibrosis. Connecting various cell populations, the ECM plays important functions not only in maintaining the heart structure, but also acting as a signal transducer for intercellular crosstalk. Although with distinct etiologies and clinical manifestations, intercellular communication derailment has been implicated in several cardiac disorders, including myocardial infarction and hypertrophy, highlighting the importance of a comprehensive and integrated view of complex cell communication networks. In this review, I intend to provide a critical perspective about the main mechanisms contributing to regulate cellular crosstalk in the heart, which may be considered in the development of future therapeutic strategies, using cell-based therapies as a paradigmatic example. This Review has an associated Future Leader to Watch interview with the author.

Predicting hyperbaric oxygen therapy success using the decision tree approach

Introduction

Hyperbaric oxygen therapy (HBOT), a procedure that involves the patient inhaling 100% oxygen gas under pressure, is currently used as an adjunctive treatment option for certain inflammatory conditions. HBOT can improve wound healing by increasing the rate of angiogenesis in injured tissue by increasing levels of vascular endothelial growth factor (VEGF). VEGF causes re-epithelialization, the migration of endothelial cells, and the formation of granulation tissue, which are involved in the wound healing process.

Methods

This study contains secondary data analyses of information previously collected in two separate studies, each concerning the effects of HBOT on diabetic foot ulcers and crush injury fractures at Prof. Dr. R. D. Kandou Hospital Manado and Siloam Hospital Manado from 2019 to early 2020.

Results

Based on the classification tree analysis, the predictors of HBOT success were leukocytes level (34%), platelet count (32%), and age (26%). The conditional inference tree analysis also indicated significant leukocyte levels, age, and platelet counts (p < 0.001), with which the interpretation of these results was the same as the classification tree analysis method. The results obtained from the random forest analysis revealed that the mean value of Gini reduction for leukocytes (207.3), platelets (110.2), age (97.9), and hemoglobin (57.9) can be used as indicators of successful HBOT. These three methods support that age, leukocytes, and platelets are determinants of HBOT success, while hemoglobin levels were only significant in one analysis method. Therefore, a new, proposed algorithm containing these factors was assembled from the results of this study.

Conclusion

HBOT cannot be separated from specific variables that contribute to and can predict its success.

Extracellular Matrices and Cancer-Associated Fibroblasts: Targets for Cancer Diagnosis and Therapy?

Solid cancer progression is dictated by neoplastic cell features and pro-tumoral crosstalks with their microenvironment. Stroma modifications, such as fibroblast activation into cancer-associated fibroblasts (CAFs) and extracellular matrix (ECM) remodeling, are now recognized as critical events for cancer progression and as potential therapeutic or diagnostic targets. The recent appreciation of the key, complex and multiple roles of the ECM in cancer and of the CAF diversity, has revolutionized the field and raised innovative but challenging questions. Here, we rapidly present CAF heterogeneity in link with their specific ECM remodeling features observed in cancer, before developing each of the impacts of such ECM modifications on tumor progression (survival, angiogenesis, pre-metastatic niche, chemoresistance, etc.), and on patient prognosis. Finally, based on preclinical studies and recent results obtained from clinical trials, we highlight key mechanisms or proteins that are, or may be, used as potential therapeutic or diagnostic targets, and we report and discuss benefits, disappointments, or even failures, of recently reported stroma-targeting strategies.

Contribution of Syndecans to the Cellular Entry of SARS-CoV-2

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a novel emerging pathogen causing an unprecedented pandemic in 21st century medicine. Due to the significant health and economic burden of the current SARS-CoV-2 outbreak, there is a huge unmet medical need for novel interventions effectively blocking SARS-CoV-2 infection. Unknown details of SARS-CoV-2 cellular biology hamper the development of potent and highly specific SARS-CoV-2 therapeutics. Angiotensin-converting enzyme-2 (ACE2) has been reported to be the primary receptor for SARS-CoV-2 cellular entry. However, emerging scientific evidence suggests the involvement of additional membrane proteins, such as heparan sulfate proteoglycans, in SARS-CoV-2 internalization. Here, we report that syndecans, the evolutionarily conserved family of transmembrane proteoglycans, facilitate the cellular entry of SARS-CoV-2. Among syndecans, the lung abundant syndecan-4 was the most efficient in mediating SARS-CoV-2 uptake. The S1 subunit of the SARS-CoV-2 spike protein plays a dominant role in the virus's interactions with syndecans. Besides the polyanionic heparan sulfate chains, other parts of the syndecan ectodomain, such as the cell-binding domain, also contribute to the interaction with SARS-CoV-2. During virus internalization, syndecans colocalize with ACE2, suggesting a jointly shared internalization pathway. Both ACE2 and syndecan inhibitors exhibited significant efficacy in reducing the cellular entry of SARS-CoV-2, thus supporting the complex nature of internalization. Data obtained on syndecan specific in vitro assays present syndecans as novel cellular targets of SARS-CoV-2 and offer molecularly precise yet simple strategies to overcome the complex nature of SARS-CoV-2 infection.

Extracellular matrix and its therapeutic potential for cancer treatment

The extracellular matrix (ECM) is one of the major components of tumors that plays multiple crucial roles, including mechanical support, modulation of the microenvironment, and a source of signaling molecules. The quantity and cross-linking status of ECM components are major factors determining tissue stiffness. During tumorigenesis, the interplay between cancer cells and the tumor microenvironment (TME) often results in the stiffness of the ECM, leading to aberrant mechanotransduction and further malignant transformation. Therefore, a comprehensive understanding of ECM dysregulation in the TME would contribute to the discovery of promising therapeutic targets for cancer treatment. Herein, we summarized the knowledge concerning the following: (1) major ECM constituents and their functions in both normal and malignant conditions; (2) the interplay between cancer cells and the ECM in the TME; (3) key receptors for mechanotransduction and their alteration during carcinogenesis; and (4) the current therapeutic strategies targeting aberrant ECM for cancer treatment.

VEGF and VEGFR2 bind to similar pH-sensitive sites on fibronectin, exposed by heparin-mediated conformational changes

Physical interactions between vascular endothelial growth factor (VEGF), a central player in blood endothelial cell biology, and fibronectin, a major fibrillar protein of the extracellular matrix, are important determinants of angiogenic activity in health and disease. Conditions signaling the need for new blood vessel growth, such as hypoxia and low extracellular pH, increase VEGF–fibronectin interactions. These interactions can be further fine-tuned through changes in the availability of the VEGF-binding sites on fibronectin, regulated by conformational changes induced by heparin and heparan sulfate chains within the extracellular matrix. These interactions may alter VEGF bioavailability, generate gradients, or alter the way VEGF is recognized by and activates its cell-surface receptors. Here, using equilibrium and kinetic studies, we discovered that fibronectin can also interact with the extracellular domain of the VEGF receptor 2 (VEGFR2). The VEGFR2-binding sites on fibronectin show great similarity to the VEGF-binding sites, as they were also exposed upon heparin-induced conformational changes in fibronectin, and the interaction was enhanced at acidic pH. Kinetic parameters and affinities for VEGF and VEGFR2 binding to fibronectin were determined by surface plasmon resonance measurements, revealing two populations of fibronectin-binding sites for each molecule. Our data also suggest that a VEGF/VEGFR2/fibronectin triple complex may be formed by VEGF or VEGFR2 first binding to fibronectin and subsequently recruiting the third binding partner. The formation of such a complex may lead to the activation of distinct angiogenic signaling pathways, offering new possibilities for clinical applications that target angiogenesis.

Fibronectin as a multiregulatory molecule crucial in tumor matrisome: from structural and functional features to clinical practice in oncology

Deciphering extracellular matrix (ECM) composition and architecture may represent a novel approach to identify diagnostic and therapeutic targets in cancer. Among the ECM components, fibronectin and its fibrillary assembly represent the scaffold to build up the entire ECM structure, deeply affecting its features. Herein we focus on this extraordinary protein starting from its complex structure and defining its role in cancer as prognostic and theranostic marker.

Granzyme B mediates impaired healing of pressure injuries in aged skin

Pressure injuries (PIs), also known as bedsores or pressure ulcers, are a major cause of death and morbidity in the elderly. The serine protease, Granzyme B (GzmB), contributes to skin aging and impaired wound healing. Aging is a major risk factor for PIs; thus, the role of GzmB in PI pathogenesis was investigated. GzmB levels in human PI tissue and wound fluids were markedly elevated. A causative role for GzmB was assessed in GzmB knockout (GzmB−/−) and wild-type (WT) mice using a murine model of PI. An apolipoprotein E knockout (ApoE−/−) model of aging and vascular dysfunction was also utilized to assess GzmB in a relevant age-related model better resembling tissue perfusion in the elderly. PI severity displayed no difference between young GzmB−/− and WT mice. However, in aged mice, PI severity was reduced in mice lacking GzmB. Mechanistically, GzmB increased vascular wall inflammation and impaired extracellular matrix remodeling. Together, GzmB is an important contributor to age-dependent impaired PI healing.

Molecular and cellular mechanisms of liver fibrosis and its regression

Chronic liver injury leads to liver inflammation and fibrosis, through which activated myofibroblasts in the liver secrete extracellular matrix proteins that generate the fibrous scar. The primary source of these myofibroblasts are the resident hepatic stellate cells. Clinical and experimental liver fibrosis regresses when the causative agent is removed, which is associated with the elimination of these activated myofibroblasts and resorption of the fibrous scar. Understanding the mechanisms of liver fibrosis regression could identify new therapeutic targets to treat liver fibrosis. This Review summarizes studies of the molecular mechanisms underlying the reversibility of liver fibrosis, including apoptosis and the inactivation of hepatic stellate cells, the crosstalk between the liver and the systems that orchestrate the recruitment of bone marrow-derived macrophages (and other inflammatory cells) driving fibrosis resolution, and the interactions between various cell types that lead to the intracellular signalling that induces fibrosis or its regression. We also discuss strategies to target hepatic myofibroblasts (for example, via apoptosis or inactivation) and the myeloid cells that degrade the matrix (for example, via their recruitment to fibrotic liver) to facilitate fibrosis resolution and liver regeneration.

Extracellular Matrix in Ischemic Heart Disease, Part 4/4: JACC Focus Seminar

Myocardial ischemia and infarction, both in the acute and chronic phases, are associated with cardiomyocyte loss and dramatic changes in the cardiac extracellular matrix (ECM). It has long been appreciated that these changes in the cardiac ECM result in altered mechanical properties of ischemic or infarcted myocardial segments. However, a growing body of evidence now clearly demonstrates that these alterations of the ECM not only affect the structural properties of the ischemic and post-infarct heart, but they also play a crucial and sometimes direct role in mediating a range of biological pathways, including the orchestration of inflammatory and reparative processes, as well as the pathogenesis of adverse remodeling. This final part of a 4-part JACC Focus Seminar reviews the evidence on the role of the ECM in relation to the ischemic and infarcted heart, as well as its contribution to cardiac dysfunction and adverse clinical outcomes.

Granzymes in cardiovascular injury and disease

Chronic inflammation and impaired wound healing play important roles in the pathophysiology of cardiovascular diseases. Moreover, the aberrant secretion of proteases plays a critical role in pathological tissue remodeling in chronic inflammatory conditions. Human Granzymes (Granule secreted enzymes - Gzms) comprise a family of five (GzmA, B, H, K, M) cell-secreted serine proteases. Although each unique in function and substrate specificities, Gzms were originally thought to share redundant, intracellular roles in cytotoxic lymphocyte-induced cell death. However, an abundance of evidence has challenged this dogma. It is now recognized, that individual Gzms exhibit unique substrate repertoires and functions both intracellularly and extracellularly. In the extracellular milieu, Gzms contribute to inflammation, vascular dysfunction and permeability, reduced cell adhesion, release of matrix-sequestered growth factors, receptor activation, and extracellular matrix cleavage. Despite these recent findings, the non-cytotoxic functions of Gzms in the context of cardiovascular disease pathogenesis remain poorly understood. Minimally detected in tissues and bodily fluids of normal individuals, GzmB is elevated in patients with acute coronary syndromes, coronary artery disease, and myocardial infarction. Pre-clinical animal models have exemplified the importance of GzmB in atherosclerosis, aortic aneurysm, and cardiac fibrosis as animals deficient in GzmB exhibit reduced tissue remodeling, improved disease phenotypes and increased survival. Although a role for GzmB in cardiovascular disease is described, further work to elucidate the mechanisms that underpin the remaining human Gzms activity in cardiovascular disease is necessary. The present review provides a summary of the pre-clinical and clinical evidence, as well as emerging areas of research pertaining to Gzms in tissue remodeling and cardiovascular disease.

Biomaterial Based Strategies for Engineering New Lymphatic Vasculature

The lymphatic system is essential for tissue regeneration and repair due to its pivotal role in resolving inflammation, immune cell surveillance, lipid transport, and maintaining tissue homeostasis. Loss of functional lymphatic vasculature is directly implicated in a variety of diseases, including lymphedema, obesity, and the progression of cardiovascular diseases. Strategies that stimulate the formation of new lymphatic vessels (lymphangiogenesis) could provide an appealing new approach to reverse the progression of these diseases. However, lymphangiogenesis is relatively understudied and stimulating therapeutic lymphangiogenesis faces challenges in precise control of lymphatic vessel formation. Biomaterial delivery systems could be used to unleash the therapeutic potential of lymphangiogenesis for a variety of tissue regenerative applications due to their ability to achieve precise spatial and temporal control of multiple therapeutics, direct tissue regeneration, and improve the survival of delivered cells. In this review, the authors begin by introducing therapeutic lymphangiogenesis as a target for tissue regeneration, then an overview of lymphatic vasculature will be presented followed by a description of the mechanisms responsible for promoting new lymphatic vessels. Importantly, this work will review and discuss current biomaterial applications for stimulating lymphangiogenesis. Finally, challenges and future directions for utilizing biomaterials for lymphangiogenic based treatments are considered.

Resident macrophages as potential therapeutic targets for cardiac ageing and injury

Cardiac‐resident macrophages (CRMs) play critical roles in maintaining cardiac homoeostasis and removing senescent and dying cells. Recent preclinical data have re‐energised the area of cardioimmunology and provided improved understanding of the modulation of compositional and functional phenotypes of CRMs. These data can aid in achieving improved cardiac regeneration, repair and functional remodelling following cardiac injury. In this review, we discuss the composition and renewal of various subsets of CRMs. Specific attention has been given to delineate the roles of various CRM subsets with respect to (1) facilitation of cardiac development and maintenance of physiological function such as electrical conduction and rhythm; (2) promotion of cardiac regeneration, inflammation resolution and functional remodelling following a cardiac injury; and (3) therapeutic potential. We have also highlighted the relationship between CRM replenishment and cardiomyocyte senescence as well as cardiovascular diseases development. Finally, we have addressed future perspectives and directions in basic research and potentially clinical applications of CRMs.

Peroxidasin is essential for endothelial cell survival and growth signaling by sulfilimine crosslink-dependent matrix assembly

Peroxidasin (PXDN) has been reported to crosslink the C-terminal non-collagenous domains of collagen IV (Col IV) by forming covalent sulfilimine bond. Here, we explored the physiological role of PXDN and its mechanism of action in endothelial cell survival and growth. Silencing of PXDN using siRNAs decreased cell proliferation without increase of the number of detached cells and decreased cell viability under serum-starved condition with increased fragmented nuclei and caspase 3/7 activity. Conditioned medium (CM) containing wild-type PXDN restored the proliferation of PXDN-depleted cells, but CM containing mutant PXDN with deletion of either N-terminal extracellular matrix (ECM) motifs or peroxidase domain failed to restore PXDN function. Accordingly, anti-PXDN antibody [raised against IgC2 (3-4) subdomain within ECM motifs] and peroxidase inhibitor phloroglucinol prevented the rescue of the PXDN-depleted cells by PXDN-containing CM. PXDN depletion resulted in loss of sulfilimine crosslinks, and decreased dense fibrillar network assembly of not only Col IV, but also fibronectin and laminin like in Col IV knockdown. Exogenous PXDN-containing CM restored ECM assembly as well as proliferation of PXDN-depleted cells. Accordingly, purified recombinant PXDN protein restored the proliferation and ECM assembly, and prevented cell death of the PXDN-depleted cells. PXDN depletion also showed reduced growth factors-induced phosphorylation of FAK and ERK1/2. In addition, siPXDN-transfected cell-derived matrix failed to provide full ECM-mediated activation of FAK and ERK1/2. These results indicate that both the ECM motifs and peroxidase activity are essential for the cellular function of PXDN and that PXDN is crucial for ECM assembly for survival and growth signaling.

Glycation of fibronectin inhibits VEGF-induced angiogenesis by uncoupling VEGF receptor-2-c-Src crosstalk

Glycation of extracellular matrix proteins has been demonstrated to contribute to the pathogenesis of vascular complications. However, no previous report has shown the role of glycated fibronectin (FN) in vascular endothelial growth factor (VEGF)‐induced angiogenesis. Thus, this study aimed to investigate the effects of glycated FN on VEGF signalling and to clarify the molecular mechanisms involved. FN was incubated with methylglyoxal (MGO) in vitro to synthesize glycated FN, and human umbilical vein endothelial cells (HUVECs) were seeded onto unmodified and MGO‐glycated FN. Then, VEGF‐induced angiogenesis and VEGF‐induced VEGF receptor‐2 (VEGFR‐2) signalling activation were measured. The results demonstrated that normal FN‐positive bands (260 kD) vanished and advanced glycation end products (AGEs) appeared in MGO‐glycated FN and glycated FN clearly changed to a higher molecular mass. The glycation of FN inhibited VEGF‐induced VEGF receptor‐2 (VEGFR‐2), Akt and ERK1/2 activation and VEGF‐induced cell migration, proliferation and tube formation. The glycation of FN also inhibited the recruitment of c‐Src to VEGFR‐2 by sequestering c‐Src through receptor for AGEs (RAGE) and the anti‐RAGE antibody restored VEGF‐induced VEGFR‐2, Akt and ERK1/2 phosphorylation, endothelial cell migration, proliferation and tube formation. Furthermore, the glycation of FN significantly inhibited VEGF‐induced neovascularization in the Matrigel plugs implanted into subcutaneous tissue of mice. Taken together, these data suggest that the glycation of FN may inhibit VEGF signalling and VEGF‐induced angiogenesis by uncoupling VEGFR‐2‐c‐Src interaction. This may provide a novel mechanism for the impaired angiogenesis in diabetic ischaemic diseases.

Collagen microarchitecture mechanically controls myofibroblast differentiation

Altered microarchitecture of collagen type I is a hallmark of wound healing and cancer that is commonly attributed to myofibroblasts. However, it remains unknown which effect collagen microarchitecture has on myofibroblast differentiation. Here, we combined experimental and computational approaches to investigate the hypothesis that the microarchitecture of fibrillar collagen networks mechanically regulates myofibroblast differentiation of adipose stromal cells (ASCs) independent of bulk stiffness. Collagen gels with controlled fiber thickness and pore size were microfabricated by adjusting the gelation temperature while keeping their concentration constant. Rheological characterization and simulation data indicated that networks with thicker fibers and larger pores exhibited increased strain-stiffening relative to networks with thinner fibers and smaller pores. Accordingly, ASCs cultured in scaffolds with thicker fibers were more contractile, expressed myofibroblast markers, and deposited more extended fibronectin fibers. Consistent with elevated myofibroblast differentiation, ASCs in scaffolds with thicker fibers exhibited a more proangiogenic phenotype that promoted endothelial sprouting in a contractility-dependent manner. Our findings suggest that changes of collagen microarchitecture regulate myofibroblast differentiation and fibrosis independent of collagen quantity and bulk stiffness by locally modulating cellular mechanosignaling. These findings have implications for regenerative medicine and anticancer treatments.

A porcine acellular dermal matrix induces human fibroblasts to secrete hyaluronic acid by activating JAK2/STAT3 signalling

Human facial skin undergoes continuous ageing over a lifespan. At present, facial skin rejuvenation is mainly achieved by injecting filling materials. However, conventional materials lack long-term beneficial effects and can only rejuvenate the skin temporarily by physical filling. To overcome this shortcoming, this study developed a porcine acellular dermal matrix with a porous three-dimensional scaffold structure and containing natural growth factors (3D-GF-PADM). The average size of the 3D-GF-PADM particles was 33.415 μm, and the dynamic viscosity and elastic modulus were within ranges suitable for clinical applications. Our study revealed that the 3D-GF-PADM exhibited an extremely low α-gal epitope number (3.15 ± 0.84 × 10¹¹/mg) and DNA content, and no immunotoxicity, but contained abundant TGF-β1, VEGF and other growth factors. More importantly, this 3D-GF-PADM actively induced the synthesis of hyaluronic acid by fibroblasts of the host skin. Study at the molecular level further demonstrated that the 3D-GF-PADM activated the JAK2/STAT3 pathway, resulting in the upregulation of HAS2 expression, which led to an increase in hyaluronic acid synthesis. Our study developed a novel 3D-GF-PADM that can actively induce hyaluronic acid synthesis, which may be used clinically as a skin filling material to achieve long-term skin rejuvenation.

By activating the JAK2/STAT3 pathway, 3D-GF-PADM induces the production of hyaluronic acid in human fibroblasts.

Shaping Up the Tumor Microenvironment With Cellular Fibronectin

Normal tissue homeostasis and architecture restrain tumor growth. Thus, for a tumor to develop and spread, malignant cells must overcome growth-repressive inputs from surrounding tissue and escape immune surveillance mechanisms that curb cancer progression. This is achieved by promoting the conversion of a physiological microenvironment to a pro-tumoral state and it requires a constant dialog between malignant cells and ostensibly normal cells of adjacent tissue. Pro-tumoral reprogramming of the stroma is accompanied by an upregulation of certain extracellular matrix (ECM) proteins and their cognate receptors. Fibronectin (FN) is one such component of the tumor matrisome. This large multidomain glycoprotein dimer expressed over a wide range of human cancers is assembled by cell-driven forces into a fibrillar array that provides an obligate scaffold for the deposition of other matrix proteins and binding sites for functionalization by soluble factors in the tumor microenvironment. Encoded by a single gene, FN regulates the proliferation, motile behavior and fate of multiple cell types, largely through mechanisms that involve integrin-mediated signaling. These processes are coordinated by distinct isoforms of FN, collectively known as cellular FN (as opposed to circulating plasma FN) that arise through alternative splicing of the FN1 gene. Cellular FN isoforms differ in their solubility, receptor binding ability and spatiotemporal expression, and functions that have yet to be fully defined. FN induction at tumor sites constitutes an important step in the acquisition of biological capabilities required for several cancer hallmarks such as sustaining proliferative signaling, promoting angiogenesis, facilitating invasion and metastasis, modulating growth suppressor activity and regulating anti-tumoral immunity. In this review, we will first provide an overview of ECM reprogramming through tumor-stroma crosstalk, then focus on the role of cellular FN in tumor progression with respect to these hallmarks. Last, we will discuss the impact of dysregulated ECM on clinical efficacy of classical (radio-/chemo-) therapies and emerging treatments that target immune checkpoints and explore how our expanding knowledge of the tumor ECM and the central role of FN can be leveraged for therapeutic benefit.

Fibronectin Adsorption on Electrospun Synthetic Vascular Grafts Attracts Endothelial Progenitor Cells and Promotes Endothelialization in Dynamic In Vitro Culture

Appropriate mechanical properties and fast endothelialization of synthetic grafts are key to ensure long-term functionality of implants. We used a newly developed biostable polyurethane elastomer (TPCU) to engineer electrospun vascular scaffolds with promising mechanical properties (E-modulus: 4.8 ± 0.6 MPa, burst pressure: 3326 ± 78 mmHg), which were biofunctionalized with fibronectin (FN) and decorin (DCN). Neither uncoated nor biofunctionalized TPCU scaffolds induced major adverse immune responses except for minor signs of polymorph nuclear cell activation. The in vivo endothelial progenitor cell homing potential of the biofunctionalized scaffolds was simulated in vitro by attracting endothelial colony-forming cells (ECFCs). Although DCN coating did attract ECFCs in combination with FN (FN + DCN), DCN-coated TPCU scaffolds showed a cell-repellent effect in the absence of FN. In a tissue-engineering approach, the electrospun and biofunctionalized tubular grafts were cultured with primary-isolated vascular endothelial cells in a custom-made bioreactor under dynamic conditions with the aim to engineer an advanced therapy medicinal product. Both FN and FN + DCN functionalization supported the formation of a confluent and functional endothelial layer.

Role of Fibronectin in Primary Open Angle Glaucoma

Primary open angle glaucoma (POAG) is the most common form of glaucoma and the 2nd most common cause of irreversible vision loss in the United States. Nearly 67 million people have the disease worldwide including >3 million in the United States. A major risk factor for POAG is an elevation in intraocular pressure (IOP). The increase in IOP is believed to be caused by an increase in the deposition of extracellular matrix proteins, in particular fibronectin, in a region of the eye known as the trabecular meshwork (TM). How fibronectin contributes to the increase in IOP is not well understood. The increased density of fibronectin fibrils is thought to increase IOP by altering the compliance of the trabecular meshwork. Recent studies, however, also suggest that the composition and organization of fibronectin fibrils would affect IOP by changing the cell-matrix signaling events that control the functional properties of the cells in the trabecular meshwork. In this article, we will discuss how changes in the properties of fibronectin and fibronectin fibrils could contribute to the regulation of IOP.

Hypoxia Induced Heparan Sulfate Primes the Extracellular Matrix for Endothelial Cell Recruitment by Facilitating VEGF-Fibronectin Interactions

Vascular endothelial growth factor-A (VEGF) is critical for the development, growth, and survival of blood vessels. Retinal pigmented epithelial (RPE) cells are a major source of VEGF in the retina, with evidence that the extracellular matrix (ECM)-binding forms are particularly important. VEGF associates with fibronectin in the ECM to mediate distinct signals in endothelial cells that are required for full angiogenic activity. Hypoxia stimulates VEGF expression and angiogenesis; however, little is known about whether hypoxia also affects VEGF deposition within the ECM. Therefore, we investigated the role of hypoxia in modulating VEGF-ECM interactions using a primary retinal cell culture model. We found that retinal endothelial cell attachment to RPE cell layers was enhanced in cells maintained under hypoxic conditions. Furthermore, we found that agents that disrupt VEGF-fibronectin interactions inhibited endothelial cell attachment to RPE cells. We also found that hypoxia induced a general change in the chemical structure of the HS produced by the RPE cells, which correlated to changes in the deposition of VEGF in the ECM, and we further identified preferential binding of VEGFR2 over VEGFR1 to VEGF laden-fibronectin matrices. Collectively, these results indicate that hypoxia-induced HS may prime fibronectin for VEGF deposition and endothelial cell recruitment by promoting VEGF-VEGFR2 interactions as a potential means to control angiogenesis in the retina and other tissues.

Extracellular Matrix-Associated Factors Play Critical Roles in Regulating Pancreatic β-Cell Proliferation and Survival

This review describes formation of the islet basement membrane and the function of extracellular matrix (ECM) components in β-cell proliferation and survival. Implications for islet transplantation are discussed. The insulin-producing β-cell is key for maintaining glucose homeostasis. The islet microenvironment greatly influences β-cell survival and proliferation. Within the islet, β-cells contact the ECM, which is deposited primarily by intraislet endothelial cells, and this interaction has been shown to modulate proliferation and survival. ECM-localized growth factors, such as vascular endothelial growth factor and cellular communication network 2, signal through specific receptors and integrins on the β-cell surface. Further understanding of how the ECM functions to influence β-cell proliferation and survival will provide targets for enhancing functional β-cell mass for the treatment of diabetes.