Dermatopontin interacts with fibronectin, promotes fibronectin fibril formation, and enhances cell adhesion

Single-Cell RNA Sequencing Reveals Cardiac Fibroblast-Specific Transcriptomic Changes in Dilated Cardiomyopathy

Dilated cardiomyopathy (DCM) is the most common cause of heart failure, with a complex aetiology involving multiple cell types. We aimed to detect cell-specific transcriptomic alterations in DCM through analysis that leveraged recent advancements in single-cell analytical tools. Single-cell RNA sequencing (scRNA-seq) data from human DCM cardiac tissue were subjected to an updated bioinformatic workflow in which unsupervised clustering was paired with reference label transfer to more comprehensively annotate the dataset. Differential gene expression was detected primarily in the cardiac fibroblast population. Bulk RNA sequencing was performed on an independent cohort of human cardiac tissue and compared with scRNA-seq gene alterations to generate a stratified list of higher-confidence, fibroblast-specific expression candidates for further validation. Concordant gene dysregulation was confirmed in TGFβ-induced fibroblasts. Functional assessment of gene candidates showed that AEBP1 may play a significant role in fibroblast activation. This unbiased approach enabled improved resolution of cardiac cell-type-specific transcriptomic alterations in DCM.

leptin b and its regeneration enhancer illustrate the regenerative features of zebrafish hearts

BACKGROUND

Zebrafish possess a remarkable regenerative capacity, which is mediated by the induction of various genes upon injury. Injury-dependent transcription is governed by the tissue regeneration enhancer elements (TREEs). Here, we utilized leptin b (lepb), an injury-specific factor, and its TREE to dissect heterogeneity of noncardiomyocytes (CMs) in regenerating hearts.

RESULTS

Our single-cell RNA sequencing (scRNA-seq) analysis demonstrated that the endothelium/endocardium(EC) is activated to induce distinct subpopulations upon injury. We demonstrated that lepb can be utilized as a regeneration-specific marker to subset injury-activated ECs. lepb+ ECs robustly induce pro-regenerative factors, implicating lepb+ ECs as a signaling center to interact with other cardiac cells. Our scRNA-seq analysis identified that lepb is also produced by subpopulation of epicardium (Epi) and epicardium-derived cells (EPDCs). To determine whether lepb labels injury-emerging non-CM cells, we tested the activity of lepb-linked regeneration enhancer (LEN) with chromatin accessibility profiles and transgenic lines. While nondetectable in uninjured hearts, LEN directs EC and Epi/EPDC expression upon injury. The endogenous LEN activity was assessed using LEN deletion lines, demonstrating that LEN deletion abolished injury-dependent expression of lepb, but not other nearby genes.

CONCLUSIONS

Our integrative analyses identify regeneration-emerging cell-types and factors, leading to the discovery of regenerative features of hearts.

Extracellular Matrix Proteomics: The mdx-4cv Mouse Diaphragm as a Surrogate for Studying Myofibrosis in Dystrophinopathy

The progressive degeneration of the skeletal musculature in Duchenne muscular dystrophy is accompanied by reactive myofibrosis, fat substitution, and chronic inflammation. Fibrotic changes and reduced tissue elasticity correlate with the loss in motor function in this X-chromosomal disorder. Thus, although dystrophinopathies are due to primary abnormalities in the DMD gene causing the almost-complete absence of the cytoskeletal Dp427-M isoform of dystrophin in voluntary muscles, the excessive accumulation of extracellular matrix proteins presents a key histopathological hallmark of muscular dystrophy. Animal model research has been instrumental in the characterization of dystrophic muscles and has contributed to a better understanding of the complex pathogenesis of dystrophinopathies, the discovery of new disease biomarkers, and the testing of novel therapeutic strategies. In this article, we review how mass-spectrometry-based proteomics can be used to study changes in key components of the endomysium, perimysium, and epimysium, such as collagens, proteoglycans, matricellular proteins, and adhesion receptors. The mdx-4cv mouse diaphragm displays severe myofibrosis, making it an ideal model system for large-scale surveys of systematic alterations in the matrisome of dystrophic fibers. Novel biomarkers of myofibrosis can now be tested for their appropriateness in the preclinical and clinical setting as diagnostic, pharmacodynamic, prognostic, and/or therapeutic monitoring indicators.

Extracellular Matrix Expression in Human Pancreatic Fat Cells of Patients with Normal Glucose Regulation, Prediabetes and Type 2 Diabetes

Previously, we found that human pancreatic preadipocytes (PPAs) and islets influence each other and that the crosstalk with the fatty liver via the hepatokine fetuin-A/palmitate induces inflammatory responses. Here, we examined whether the mRNA-expression of pancreatic extracellular matrix (ECM)-forming and -degrading components differ in PPAs from individuals with normal glucose regulation (PPAs-NGR), prediabetes (PPAs-PD), and type 2 diabetes (PPAs-T2D), and whether fetuin-A/palmitate impacts ECM-formation/degradation and associated monocyte invasion. Human pancreatic resections were analyzed (immuno)histologically. PPAs were studied for mRNA expression by real-time PCR and protein secretion by Luminex analysis. Furthermore, co-cultures with human islets and monocyte migration assays in Transwell plates were conducted. We found that in comparison with NGR-PPAs, TIMP-2 mRNA levels were lower in PPAs-PD, and TGF-β1 mRNA levels were higher in PPAs-T2D. Fetuin-A/palmitate reduced fibronectin, decorin, TIMP-1/-2 and TGF-ß1 mRNA levels. Only fibronectin was strongly downregulated by fetuin-A/palmitate independently of the glycemic status. Co-culturing of PPAs with islets increased TIMP-1 mRNA expression in islets. Fetuin-A/palmitate increased MMP-1, usherin and dermatopontin mRNA-levels in co-cultured islets. A transmigration assay showed increased monocyte migration towards PPAs, which was enhanced by fetuin-A/palmitate. This was more pronounced in PPAs-T2D. The expression of distinct ECM components differs in PPAs-PD and PPAs-T2D compared to PPAs-NGR, suggesting that ECM alterations can occur even in mild hyperglycemia. Fetuin-A/palmitate impacts on ECM formation/degradation in PPAs and co-cultured islets. Fetuin-A/palmitate also enhances monocyte migration, a process which might impact on matrix turnover.

Effect of dermatopontin on osteogenic differentiation of periodontal ligament stem cells

Human periodontal ligament stem cells (hPDLSCs) are promising seed cells for oral bone tissue engineering. Dermatopontin (DPT) is a small-molecule protein recognized as a non-collagenous component of the extracellular matrix and is associated with a variety of biological processes. In this study, we first determined that DPT was elevated during the osteogenic differentiation of hPDLSCs. HPDLSCs interfering with DPT expression were established by lentiviral infection. It was found that the proliferation and osteogenic differentiation ability of hPDLSCs were inhibited after interfering DPT with lentivirus. Exogenous recombinant DPT treatment could not alter the proliferation of hPDLSCs. Coincidentally, exogenous DPT can only enhance the osteogenic differentiation of hPDLSCs in the control lentivirus group, but had no significant effect on the DPT interference group. This study expands the understanding of DPT function and implicates DPT as an important target for enhancing osteogenic differentiation of hPDLSCs.

Single-cell transcriptomics of hepatic stellate cells uncover crucial pathways and key regulators involved in non-alcoholic steatohepatitis

Background

Fibrosis is an important pathological process in the development of non-alcoholic steatohepatitis (NASH), and the activation of hepatic stellate cell (HSC) is a central event in liver fibrosis. However, the transcriptomic change of activated HSCs (aHSCs) and resting HSCs (rHSCs) in NASH patients has not been assessed. This study aimed to identify transcriptomic signature of HSCs during the development of NASH and the underlying key functional pathways.

Methods

NASH-associated transcriptomic change of HSCs was defined by single-cell RNA-sequencing (scRNA-seq) analysis, and those top upregulated genes were identified as NASH-associated transcriptomic signatures. Those functional pathways involved in the NASH-associated transcriptomic change of aHSCs were explored by weighted gene co-expression network analysis (WGCNA) and functional enrichment analyses. Key regulators were explored by upstream regulator analysis and transcription factor enrichment analysis.

Results

scRNA-seq analysis identified numerous differentially expressed genes in both rHSCs and aHSCs between NASH patients and healthy controls. Both scRNA-seq analysis and in-vivo experiments showed the existence of rHSCs (mainly expressing a-SMA) in the normal liver and the increased aHSCs (mainly expressing collagen 1) in the fibrosis liver tissues. NASH-associated transcriptomic signature of rHSC (NASHrHSCsignature) and NASH-associated transcriptomic signature of aHSC (NASHaHSCsignature) were identified. WGCNA revealed the main pathways correlated with the transcriptomic change of aHSCs. Several key upstream regulators and transcription factors for determining the functional change of aHSCs in NASH were identified.

Conclusion

This study developed a useful transcriptomic signature with the potential in assessing fibrosis severity in the development of NASH. This study also identified the main pathways in the activation of HSCs during the development of NASH.

Regenerative Medicine-Based Treatment for Vitiligo: An Overview

Vitiligo is a complex disorder with an important effect on the self-esteem and social life of patients. It is the commonest acquired depigmentation disorder characterized by the development of white macules resulting from the selective loss of epidermal melanocytes. The pathophysiology is complex and involves genetic predisposition, environmental factors, oxidative stress, intrinsic metabolic dysfunctions, and abnormal inflammatory/immune responses. Although several therapeutic options have been proposed to stabilize the disease by stopping the depigmentation process and inducing durable repigmentation, no specific cure has yet been defined, and the long-term persistence of repigmentation is unpredictable. Recently, due to the progressive loss of functional melanocytes associated with failure to spontaneously recover pigmentation, several different cell-based and cell-free regenerative approaches have been suggested to treat vitiligo. This review gives an overview of clinical and preclinical evidence for innovative regenerative approaches for vitiligo patients.

Tyrosine-sulfated dermatopontin shares multiple binding sites and recognition determinants on triple-helical collagens with proteins implicated in cell adhesion and collagen folding, fibrillogenesis, cross-linking, and degradation

Dermatopontin (DPT), a small extracellular matrix protein that stimulates collagen fibrillogenesis, contains sulfotyrosine residues but neither its level of sulfation nor its binding sites on fibrillar collagens are known. Here, we discovered that DPT is present in a relatively high mass concentration (~ 0.02%) in porcine corneal stroma, from which we purified five DPT charge variants (A-E) containing up to six sulfations. The major variant (C), containing four sulfotyrosine residues, was used to locate binding sites for DPT on triple-helical collagens II and III using the Collagen Toolkits. DPT-binding loci included the triple helix crosslinking sites and collagenase cleavage site. We find that strong DPT-binding sites on triple-helical collagen comprise an arginine-rich, positively-charged sequence that also contains hydrophobic residues. This collagen-binding signature of DPT is similar to that of the chaperone HSP47. Thus, we propose that DPT assumes the role of HSP47 as a collagen chaperone during and after the secretion. Peptide II-44, harbouring the conserved collagenase cleavage site, shows the strongest DPT-binding of the Collagen Toolkit II peptides. Substituting any of the three arginine residues (R) with alanine in the sequence GLAGQRGIVGLOGQRGER of II-44 resulted in almost complete loss of DPT binding. Since osteogenesis imperfecta, spondyloepiphyseal dysplasia, and spondyloepimetaphyseal dysplasia congenita are associated with missense mutations that substitute the corresponding arginine residues in collagens alpha-1(I) and alpha-1(II), we suggest that disrupted DPT binding to fibrillar collagens may contribute to these connective tissue disorders. In conclusion, the present work provides a cornerstone for further elucidation of the role of DPT.

Extracellular Matrix and the Production of Cultured Meat

Cultured meat production is an evolving method of producing animal meat using tissue engineering techniques. Cells, chemical factors, and suitable biomaterials that serve as scaffolds are all essential for the cultivation of muscle tissue. Scaffolding is essential for the development of organized meat products resembling steaks because it provides the mechanical stability needed by cells to attach, differentiate, and mature. In in vivo settings, extracellular matrix (ECM) ensures substrates and scaffolds are provided for cells. The ECM of skeletal muscle (SM) maintains tissue elasticity, creates adhesion points for cells, provides a three-dimensional (3D) environment, and regulates biological processes. Consequently, creating mimics of native ECM is a difficult task. Animal-derived polymers like collagen are often regarded as the gold standard for producing scaffolds with ECM-like properties. Animal-free scaffolds are being investigated as a potential source of stable, chemically defined, low-cost materials for cultured meat production. In this review, we explore the influence of ECM on myogenesis and its role as a scaffold and vital component to improve the efficacy of the culture media used to produce cultured meat.

Inhibition of the interaction between fibronectin and dermatopontin by Clostridium perfringens fibronectin-binding proteins

Fibronectin (Fn) is an approximately 450 kDa glycoprotein that consists of 12 type I, 2 type II, and 15-17 type III modules. Fibrillation of Fn is important for tissue reconstitution and wound healing. We previously reported that Clostridium perfringens produces several Fn-binding proteins (Fbps), two of which, FbpA and FbpB, bind to III₁ -C (a fragment of Fn derived from the carboxyl-terminal two-thirds of the first-type III module). Dermatopontin (DPT), a 22 kDa noncollagenous extracellular matrix protein, accelerates normal collagen fibrillation and induces Fn fibrillation. DPT interacts with Fn-type III_12-14 (III_12-14 ), leading to a change in Fn conformation and promoting Fn fibrillation. Here, we investigated the effects of FbpA and FbpB on the binding of Fn and the III_12-14 fragment to DPT and on the DPT-induced Fn fibrillation. Both recombinant FbpA (rFbpA) and recombinant FbpB (rFbpB) significantly inhibited Fn binding to DPT and recombinant III_12-14 (rIII_12-14 ) binding, and inhibited DPT-induced Fn fibrillation. Furthermore, it was found that both rFbpA and rFbpB significantly bound to coated DPT in an enzyme-linked avidin-biotin complex system, whereas rIII_12-14 did not bind to either coated rFbpA or rFbpB. In conclusion, both FbpA and FbpB inhibited DPT-induced Fn fibrillation via their interaction with DPT. Both FbpA and FbpB released from lysed C. perfringens cells in wounds and/or infected tissue may prevent Fn fibrillation and delay the wound healing process, subsequently exacerbating infection.

The role of dermatopontin in cell adhesion in bovine placenta during early-mid pregnancy and parturition - Pilot study

Dermatopontin (DPT) is a small protein molecule thought to have a role in the formation of the extracellular architecture and adhesion. The aim of the study was to confirm the presence of DPT and to examine its role in placental cell adhesion during pregnancy, at parturition and postpartum in cows. Placental tissue samples were obtained at abattoir from healthy pregnant cows (n = 6) while parturient samples were collected during caesarian section and retrospectively divided into released up to 6 h (R; n = 5) and not released up to 6 h (NR; n = 4) foetal membranes. Maternal epithelial cells were isolated from pregnant samples and were used for the examination of the influence of DPT (5, 50 and 100 ng/mL) on cell adhesion. Parturient samples were manually divided into maternal and foetal part and individually homogenized for Western blotting and ELISA analysis. Western blotting confirmed the presence of DPT in examined tissues. ELISA test showed significant (p < 0.05) decrease in DPT concentration within examined pregnancy period with higher concentrations in maternal part (p < 0.05). Moreover, at parturition DPT concentration further decreased in maternal (p < 0.05) but increased (p < 0.05) in fetal part. The examination of not released samples showed opposite relationship in comparison to parturient samples - the increase in maternal (p < 0.05) and the decrease in fetal (p < 0.05) part of placenta. DPT facilitated the adhesion of epithelial cells in examined periods of pregnancy in increasing manner with pregnancy course. The presence of DPT in bovine placenta during pregnancy and parturition was confirmed. This protein may influence cell adhesion during attachment and detachment of placenta. Further studies on mechanisms of action of DPT in bovine placenta are necessary.

Cloning, expression and purification of recombinant dermatopontin in Escherichia coli

Dermatopontin (DPT) is an extracellular matrix (ECM) protein with diversified pharmaceutical applications. It plays important role in cell adhesion/migration, angiogenesis and ECM maintenance. The recombinant production of this protein will enable further exploration of its multifaceted functions. In this study, DPT protein has been expressed in Escherichia coli (E.coli) aiming at cost effective recombinant production. The E.coli GJ1158 expression system was transformed with constructed recombinant vector (pRSETA-DPT) and protein was expressed as inclusion bodies on induction with NaCl. The inclusion bodies were solubilised in urea and renaturation of protein was done by on-column refolding procedure in Nickel activated Sepharose column. The refolded Histidine-tagged DPT protein was purified and eluted from column using imidazole and its purity was confirmed by analytical techniques. The biological activity of the protein was confirmed by collagen fibril assay, wound healing assay and Chorioallantoic Membrane (CAM) angiogenesis assay on comparison with standard DPT. The purified DPT was found to enhance the collagen fibrillogenesis process and improved the migration of human endothelial cells. About 73% enhanced wound closure was observed in purified DPT treated endothelial cells as compared to control. The purified DPT also could induce neovascularisation in the CAM model. At this stage, scaling up the production process for DPT with appropriate purity and reproducibility will have a promising commercial edge.

Review of Integrin-Targeting Biomaterials in Tissue Engineering

The ability to direct cell behavior has been central to the success of numerous therapeutics to regenerate tissue or facilitate device integration. Biomaterial scientists are challenged to understand and modulate the interactions of biomaterials with biological systems in order to achieve effective tissue repair. One key area of research investigates the use of extracellular matrix-derived ligands to target specific integrin interactions and induce cellular responses, such as increased cell migration, proliferation, and differentiation of mesenchymal stem cells. These integrin-targeting proteins and peptides have been implemented in a variety of different polymeric scaffolds and devices to enhance tissue regeneration and integration. This review first presents an overview of integrin-mediated cellular processes that have been identified in angiogenesis, wound healing, and bone regeneration. Then, research utilizing biomaterials are highlighted with integrin-targeting motifs as a means to direct these cellular processes to enhance tissue regeneration. In addition to providing improved materials for tissue repair and device integration, these innovative biomaterials provide new tools to probe the complex processes of tissue remodeling in order to enhance the rational design of biomaterial scaffolds and guide tissue regeneration strategies.

Glucocorticoid regulates mesenchymal cell differentiation required for perinatal lung morphogenesis and function

While antenatal glucocorticoids are widely used to enhance lung function in preterm infants, cellular and molecular mechanisms by which glucocorticoid receptor (GR) signaling influences lung maturation remain poorly understood. Deletion of the glucocorticoid receptor gene (Nr3c1) from fetal pulmonary mesenchymal cells phenocopied defects caused by global Nr3c1 deletion, while lung epithelial- or endothelial-specific Nr3c1 deletion did not impair lung function at birth. We integrated genome-wide gene expression profiling, ATAC-seq, and single cell RNA-seq data in mice in which GR was deleted or activated to identify the cellular and molecular mechanisms by which glucocorticoids control prenatal lung maturation. GR enhanced differentiation of a newly defined proliferative mesenchymal progenitor cell (PMP) into matrix fibroblasts (MFBs), in part by directly activating extracellular matrix-associated target genes, including Fn1, Col16a4, and Eln and by modulating VEGF, JAK-STAT, and WNT signaling. Loss of mesenchymal GR signaling blocked fibroblast progenitor differentiation into mature MFBs, which in turn increased proliferation of SOX9+ alveolar epithelial progenitor cells and inhibited differentiation of mature alveolar type II (AT₂) and AT₁ cells. GR signaling controls genes required for differentiation of a subset of proliferative mesenchymal progenitors into matrix fibroblasts, in turn, regulating signals controlling AT₂/AT₁ progenitor cell proliferation and differentiation and identifying cells and processes by which glucocorticoid signaling regulates fetal lung maturation.

The role of extracellular matrix in the pathophysiology of diabetic wounds

Impaired healing leading to the formation of ulcerated wounds is a critical concern in patients with diabetes. Abnormalities in extracellular matrix (ECM) production and remodeling contribute to tissue dysfunction and delayed healing. Specifically, diabetes-induced changes in the expression and/or activity of structural proteins, ECM-modifying enzymes, proteoglycans, and matricellular proteins have been reported. In this review, we provide a summary of the key ECM molecules and associated changes in skin and diabetic wounds. Such information should allow for new insights in the understanding of impaired wound healing and lead to the development of ECM-based therapeutic strategies.

Dermatopontin, A Novel Adipokine Promoting Adipose Tissue Extracellular Matrix Remodelling and Inflammation in Obesity

Compelling evidence suggests that dermatopontin (DPT) regulates collagen and fibronectin fibril formation, the induction of cell adhesion and the prompting of wound healing. We aimed to evaluate the role of DPT on obesity and its associated metabolic alterations as well as its impact in visceral adipose tissue (VAT) inflammation and extracellular matrix (ECM) remodelling. Samples obtained from 54 subjects were used in a case-control study. Circulating and VAT expression levels of DPT as well as key ECM remodelling- and inflammation-related genes were analysed. The effect of pro- and anti-inflammatory mediators on the transcript levels of DPT in visceral adipocytes was explored. The impact of DPT on ECM remodelling and inflammation pathways was also evaluated in cultured adipocytes. We show that obesity and obesity-associated type 2 diabetes (T2D) increased (p < 0.05) circulating levels of DPT. In this line, DPT mRNA in VAT was increased (p < 0.05) in obese patients with and without T2D. Gene expression levels of DPT were enhanced (p < 0.05) in human visceral adipocytes after the treatment with lipopolysaccharide, tumour growth factor (TGF)-β and palmitic acid, whereas a downregulation (p < 0.05) was detected after the stimulation with interleukin (IL)-4 and IL-13, critical cytokines mediating anti-inflammatory pathways. Additionally, we revealed that DPT increased (p < 0.05) the expression of ECM- (COL6A3, ELN, MMP9, TNMD) and inflammation-related factors (IL6, IL8, TNF) in human visceral adipocytes. These findings provide, for the first time, evidence of a novel role of DPT in obesity and its associated comorbidities by influencing AT remodelling and inflammation.

Cross-Talk Between Extracellular Matrix and Skeletal Muscle: Implications for Myopathies

Skeletal muscle (SM) comprises around 40% of total body weight and is among the most important plastic tissues, as it supports skeletal development, controls body temperature, and manages glucose levels. Extracellular matrix (ECM) maintains the integrity of SM, enables biochemical signaling, provides structural support, and plays a vital role during myogenesis. Several human diseases are coupled with dysfunctions of the ECM, and several ECM components are involved in disease pathologies that affect almost all organ systems. Thus, mutations in ECM genes that encode proteins and their transmembrane receptors can result in diverse SM diseases, a large proportion of which are types of fibrosis and muscular dystrophy. In this review, we present major ECM components of SMs related to muscle-associated diseases, and discuss two major ECM myopathies, namely, collagen myopathy and laminin myopathies, and their therapeutic managements. A comprehensive understanding of the mechanisms underlying these ECM-related myopathies would undoubtedly aid the discovery of novel treatments for these devastating diseases.

In Depth Quantification of Extracellular Matrix Proteins from Human Pancreas

Extracellular matrix (ECM) is an important component of the pancreatic microenvironment which regulates β cell proliferation, differentiation, and insulin secretion. Protocols have recently been developed for the decellularization of the human pancreas to generate functional scaffolds and hydrogels. In this work, we characterized human pancreatic ECM composition before and after decellularization using isobaric dimethylated leucine (DiLeu) labeling for relative quantification of ECM proteins. A novel correction factor was employed in the study to eliminate the bias introduced during sample preparation. In comparison to the commonly employed sample preparation methods (urea and FASP) for proteomic analysis, a recently developed surfactant and chaotropic agent assisted sequential extraction/on pellet digestion (SCAD) protocol has provided an improved strategy for ECM protein extraction of human pancreatic ECM matrix. The quantitative proteomic results revealed the preservation of matrisome proteins while most of the cellular proteins were removed. This method was compared with a well-established label-free quantification (LFQ) approach which rendered similar expressions of different categories of proteins (collagens, ECM glycoproteins, proteoglycans, etc.). The distinct expression of ECM proteins was quantified comparing adult and fetal pancreas ECM, shedding light on the correlation between matrix composition and postnatal β cell maturation. Despite the distinct profiles of different subcategories in the native pancreas, the distribution of matrisome proteins exhibited similar trends after the decellularization process. Our method generated a large data set of matrisome proteins from a single tissue type. These results provide valuable insight into the possibilities of constructing a bioengineered pancreas. It may also facilitate better understanding of the potential roles that matrisome proteins play in postnatal β cell maturation.

Dermatopontin in Skeletal Muscle Extracellular Matrix Regulates Myogenesis

Dermatopontin (DPT) is an extensively distributed non-collagenous component of the extracellular matrix predominantly found in the dermis of the skin, and consequently expressed in several tissues. In this study, we explored the role of DPT in myogenesis and perceived that it enhances the cell adhesion, reduces the cell proliferation and promotes the myoblast differentiation in C2C12 cells. Our results reveal an inhibitory effect with fibronectin (FN) in myoblast differentiation. We also observed that DPT and fibromodulin (FMOD) regulate positively to each other and promote myogenic differentiation. We further predicted the 3D structure of DPT, which is as yet unknown, and validated it using state-of-the-art in silico tools. Furthermore, we explored the in-silico protein-protein interaction between DPT-FMOD, DPT-FN, and FMOD-FN, and perceived that the interaction between FMOD-FN is more robust than DPT-FMOD and DPT-FN. Taken together, our findings have determined the role of DPT at different stages of the myogenic process.

Gene profiling involved in fate determination of salivary gland type in mouse embryogenesis

Salivary gland (SG) development involves dynamic epithelial-mesenchymal interactions resulting in the formation of highly branched epithelial structures that produce and secrete saliva. The SG epithelium differentiates into saliva-producing terminal buds, i.e., acini, and transporting ducts. Most studies on the salivary gland have focused on branching morphogenesis; however, acinar cell differentiation underlying the determination of serous or mucous salivary glands is unclear. The objective of this study was to identify the mesenchymal signaling molecules involved in the epithelial differentiation of the salivary gland type as serous or mucous. Salivary glands undergoing stage-specific development, including the parotid gland (PG) and the sublingual gland (SLG) at embryonic day 14.5 (E14.5) were dissected. The glands were treated with dispase II to separate the epithelium and the mesenchyme. RNA from mesenchyme was processed for microarray analysis. Thereafter, microarray data were analyzed to identify putative candidate molecules involved in salivary gland differentiation and confirmed via quantitative reverse transcription polymerase chain reaction. The microarray analysis revealed the expression of 31,873 genes in the PG and SLG mesenchyme. Of the expressed genes 21,026 genes were found to be equally expressed (Fold change 1.000) in both PG and SLG mesenchyme. The numbers of genes expressed over onefold in the PG and SLG mesenchyme were found to be 5247 and 5600 respectively. On limiting the fold-change cut off value over 1.5 folds, only 214 and 137 genes were expressed over 1.5 folds in the PG and the SLG mesenchyme respectively. Our findings suggest that differential expression patterns of the mesenchymal signaling molecules are involved in fate determination of the salivary acinar cell types during mouse embryogenesis. In the near future, functional evaluation of the candidate genes will be performed using gain- and loss-of-function mutation studies during in vitro organ cultivation.

Transcriptomic Profiling of Obesity-Related Nonalcoholic Steatohepatitis Reveals a Core Set of Fibrosis-Specific Genes

Nonalcoholic steatohepatitis (NASH) is strongly associated with obesity and type 2 diabetes. The molecular factors underlying the development of inflammation and severe fibrosis in NASH remain largely unknown. The purpose of this study was to identify gene expression patterns related to obesity-related NASH inflammation and fibrosis. We performed sequencing-based mRNA profiling analysis of liver samples from individuals with normal histology (n = 24), lobular inflammation (n = 53), or bridging fibrosis, incomplete cirrhosis, or cirrhosis (n = 65). Hepatic expression of a subset of mRNAs was validated using an orthogonal method, analyzed in a hepatic stellate cell line, and used to identify transcriptional patterns shared by other forms of cirrhosis. We observed evidence for differential levels of 3820 and 2980 transcripts in lobular inflammation and advanced fibrosis, respectively, compared with normal histology (false discovery rate ≤0.05), including 176 genes specific to fibrosis. Functional enrichment analysis of these genes revealed participation in pathways involving cytokine-cytokine receptor interaction, PI3K-Akt signaling pathway, focal adhesion, and extracellular matrix-receptor interaction. We identified 34 differentially expressed transcripts in comparisons of lobular inflammation and fibrosis, a proportion of which were also upregulated during activation of hepatic stellate cells. A set of 16 genes from a previous independent study of NASH bridging fibrosis/cirrhosis were replicated, several of which have also been associated with advanced fibrosis/cirrhosis due to hepatitis viruses or alcohol in human patients. Dysregulated mRNA expression is associated with inflammation and fibrosis in NASH. Advanced NASH fibrosis is characterized by distinct set of molecular changes that are shared with other causes of cirrhosis.

The composition of prostate core matrisome in vivo and in vitro unveiled by mass spectrometric analysis

BACKGROUND

The composition and organization of extracellular matrix (ECM) are important regulators of cell behavior. In particular in the prostate, this central role of the ECM is further stressed by the fact that several potential markers of prostate stem cells are matrix receptors.

METHODS

We established 12 fibroblastic cell lines from cancerous and non-cancerous areas of six prostates and allowed the cells to produce ECM under cell culture conditions. We also performed a proteome wide analysis of the ECM components by mass spectrometry. To study the in vitro activation of fibroblastic cells we compared the differences between the ECM produced in cell culture by six non-cancerous-tissue-derived fibroblasts and the in vivo matrisome from the corresponding non-cancerous tissue of prostate.

RESULTS

Our results suggest that at tissue level the ECM is mainly produced by fibroblastic cells and that it contains standard collagen I fibrils and fibril-associated proteins. Beaded-filament forming collagen VI is also abundant and basement membranes potentially contain five laminin subtypes and collagens XV and XVIII. As the main finding, we also detected differences when in vivo and in vitro matrisomes were compared. Only 65 out of 206 proteins were found to be common for both in vivo and in vitro samples. Majority of the 55 proteins, which were solely detected in in vivo samples, were considered to be plasma derived. Eighty-six proteins were solely found from in vitro fibroblast-derived ECM, and most of them were related to matrix remodeling or growth factor action, proposing that the activation of fibroblasts in cell culture may remarkably modify their gene expression profile. Finally, in comparison to traditional 2D in vitro cell culture, the ECM composition of 3D spheroid culture was analyzed. The matrisome in spheroid culture did not resemble the in vivo ECM more closely than in monolayer culture.

CONCLUSIONS

Artificial activation of ECM remodeling seems to be a distinctive feature in in vitro models. In conclusion the constitution of ECM produced by prostate derived fibroblasts in vitro is similar, but not identical to the prostate ECM in vivo as shown here by mass spectrometric analysis.

Integrins in wound healing, fibrosis and tumor stroma: High potential targets for therapeutics and drug delivery

Wound healing is a complex process, which ultimately leads to fibrosis if not repaired well. Pathologically very similar to fibrosis is the tumor stroma, found in several solid tumors which are regarded as wounds that do not heal. Integrins are heterodimeric surface receptors which control various physiological cellular functions. Additionally, integrins also sense ECM-induced extracellular changes during pathological events, leading to cellular responses, which influence ECM remodeling. The purpose and scope of this review is to introduce integrins as key targets for therapeutics and drug delivery within the scope of wound healing, fibrosis and the tumor stroma. This review provides a general introduction to the biology of integrins including their types, ligands, means of signaling and interaction with growth factor receptors. Furthermore, we highlight integrins as key targets for therapeutics and drug delivery, based on their biological role, expression pattern within human tissues and at cellular level. Next, therapeutic approaches targeting integrins, with a focus on clinical studies, and targeted drug delivery strategies based on ligands are described.

Effects of Dermatopontin gene silencing on apoptosis and proliferation of osteosarcoma MG‑63 cells

The present study aimed to investigate the effect of Dermatopontin (DPT) gene silencing on the apoptosis and proliferation of osteosarcoma MG‑63 cells. Three eukaryotic expression vectors of short hairpin (sh)RNA fragments targeting different loci of DPT were designed and transfected into an osteosarcoma cell line MG‑63. The cells were assigned to a blank, shRNA‑control, DPT‑shRNA‑a, DPT‑shRNA‑b or DPT‑shRNA‑c group. The shRNA with the highest silencing efficiency was screened using reverse transcription‑quantitative polymerase chain reaction and western blotting. The screened shRNA was transfected into MG‑63 cells. The proliferation, cell cycle and apoptosis of MG‑63 cells were measured using a Cell Counting Kit‑8 assay, flow cytometry and Annexin V‑fluorescein isothiocyanate assay. The recombinant plasmids containing DPT shRNA were successfully constructed. DPT gene silencing was able to significantly reduce the proliferation rate of MG‑63 cells (P<0.05). The proportion of cells in the G0/G1 phase and in the G2/M phase increased significantly (both P<0.05), while the proportion of cells in the S phase decreased (P<0.05). Furthermore, the cell apoptosis rate increased significantly (P<0.05). These results demonstrate that DPT gene silencing is able to reduce the proliferation of MG‑63 cells, slow down cell cycle progression and promote apoptosis, hence may become a novel target for the treatment of osteosarcoma.

Proteomic characterization of platelet gel releasate from adult peripheral and cord blood

PURPOSE

Activated platelet gel (PG) derived from adult peripheral blood (APB) has been extensively used for topical therapy of various clinical conditions. Conversely, few observations on PG from umbilical cord blood (CB) have been reported so far. Although PG preparations are known to contain a high concentration of a large number of biological factors involved in inflammation and tissue repair, their comprehensive characterization is still missing. The innovative goal of our research was to use proteomics technologies in order to profile biologically active components in these blood derivatives.

EXPERIMENTAL DESIGN

Supernatants recovered from three independent APB and CB-derived PGs, prepared using batroxobin, were enriched for low-abundance proteins with ProteoMiner and subsequently analyzed by GeLC-MS/MS.

RESULTS

The 751 and 760 proteins were identified in the APB and CB-derived PG releasates, respectively. A core dataset including only proteins found in 2/3 and 3/3 biological replicates was generated and functionally characterized by gene ontology. Searching against Vesiclepedia database showed that 33% of our dataset consists of novel releasate proteins. Comparison between the two types of PG secretomes revealed that 117 proteins are present only in the APB-derived samples, 104 proteins are distinctive of the CB-derived samples, and 229 are in common.

CONCLUSION AND CLINICAL RELEVANCE

Our study highlighted a differential content of proteins supporting tissue repair and regeneration between APB and CB-derived PGs. These findings may help better identifying future appropriate clinical applications.

Interspecies NASH disease activity whole-genome profiling identifies a fibrogenic role of PPARα-regulated dermatopontin

Nonalcoholic fatty liver disease prevalence is soaring with the obesity pandemic, but the pathogenic mechanisms leading to the progression toward active nonalcoholic steatohepatitis (NASH) and fibrosis, major causes of liver-related death, are poorly defined. To identify key components during the progression toward NASH and fibrosis, we investigated the liver transcriptome in a human cohort of NASH patients. The transition from histologically proven fatty liver to NASH and fibrosis was characterized by gene expression patterns that successively reflected altered functions in metabolism, inflammation, and epithelial-mesenchymal transition. A meta-analysis combining our and public human transcriptomic datasets with murine models of NASH and fibrosis defined a molecular signature characterizing NASH and fibrosis and evidencing abnormal inflammation and extracellular matrix (ECM) homeostasis. Dermatopontin expression was found increased in fibrosis, and reversal of fibrosis after gastric bypass correlated with decreased dermatopontin expression. Functional studies in mice identified an active role for dermatopontin in collagen deposition and fibrosis. PPARα activation lowered dermatopontin expression through a transrepressive mechanism affecting the Klf6/TGFβ1 pathway. Liver fibrotic histological damages are thus characterized by the deregulated expression of a restricted set of inflammation- and ECM-related genes. Among them, dermatopontin may be a valuable target to reverse the hepatic fibrotic process.

Extracellular matrix proteins in healthy and retained placentas, comparing hemochorial and synepitheliochorial placentas

The placenta expresses structural and biologically active proteins. Their synthesis is mainly regulated by genomic or nongenomic signals and modulated by hormones. These protein profiles are altered during different stages of pregnancy. The biological properties of extracellular matrix (ECM) proteins were defined and described in a number of tissues including placenta. These properties enable them to be the main players in the processes of attachment or invasion into the endometrium during initial placenta formation and its timely separation after delivery and detachment. In this review, we focused on the role of ECM proteins during attachment of the placenta to the uterine wall, its timely separation, and the implications of this process on retained or pathologically attached placenta. Although the amount of published information in this area is relatively scant, some of the key proteins and processes are well defined. We focused on the available data detailing the ECM protein profiles of human (histologically thin; hemochorial) and bovine (histologically thick; epitheliochorial) placentas and compared the shared and unique ECM proteins that are relevant to placental attachment and separation.

Variable expressivity and genetic heterogeneity involving DPT and SEMA3D genes in autosomal dominant familial Meniere's disease

Autosomal dominant (AD) familial Meniere's disease (FMD) is a rare disorder involving the inner ear defined by sensorineural hearing loss, tinnitus and episodic vertigo. Here, we have identified two novel and rare heterozygous variants in the SEMA3D and DPT genes segregating with the complete phenotype that have variable expressivity in two pedigrees with AD-FMD. A detailed characterization of the phenotype within each family illustrates the clinical heterogeneity in the onset and progression of the disease. We also showed the expression of both genes in the human cochlea and performed in silico analyses of these variants. Three-dimensional protein modelling showed changes in the structure of the protein indicating potential physical interactions. These results confirm a genetic heterogeneity in FMD with incomplete penetrance and variable expressivity.

Normal human mitral valve proteome: A preliminary investigation by gel-based and gel-free proteomic approaches

The mitral valve is a highly complex structure which regulates blood flow from the left atrium to the left ventricle (LV) avoiding a significant forward gradient during diastole or regurgitation during systole. The integrity of the mitral valve is also essential for the maintenance of normal LV size, geometry, and function. Significant advances in the comprehension of the biological, functional, and mechanical behavior of the mitral valve have recently been made. However, current knowledge of protein components in the normal human mitral valve is still limited and complicated by the low cellularity of this tissue and the presence of high abundant proteins from the extracellular matrix. We employed here an integrated proteomic approach to analyse the protein composition of the normal human mitral valve and reported confident identification of 422 proteins, some of which have not been previously described in this tissue. In particular, we described the ability of pre-MS separation technique based on liquid-phase IEF and SDS-PAGE to identify the largest number of proteins. We also demonstrated that some of these proteins, e.g. αB-Crystallin, septin-11, four-and-a-half LIM domains protein 1, and dermatopontin, are synthesised by interstitial cells isolated from human mitral valves. These initial results provide a valuable basis for future studies aimed at analysing in depth the mitral valve protein composition and at investigating potential pathogenetic molecular mechanisms. Data are available via ProteomeXchange with identifier PXD004397.

RNA sequencing reveals differentially expressed genes as potential diagnostic and prognostic indicators of gallbladder carcinoma

Gallbladder carcinoma (GBC) is a rare tumor with a dismal survival rate overall. Hence, there is an urgent need for exploring more specific and sensitive biomarkers for the diagnosis and treatment of GBC. At first, amplified total RNAs from two paired GBC tumors and adjacent non-tumorous tissues (ANTTs) were subjected to RNA sequencing. 161 genes were identified differentially expressed between tumors and ANTTs. Functional enrichment analysis indicated that the up-regulated genes in tumor were primarily associated with signaling molecules and enzyme modulators, and mainly involved in cell cycles and pathways in cancer. Twelve differentially expressed genes (DEGs) were further confirmed in another independent cohort of 35 GBC patients. Expression levels of BIRC5, TK1, TNNT1 and MMP9 were found to be positively related to postoperative relapse. There was also a significant correlation between BIRC5 expression and tumor-node-metastasis (TNM) stage. Besides, we observed a positive correlation between serum CA19-9 concentration and the expression levels of TNNT1, MMP9 and CLIC3. Survival analysis revealed that GBC patients with high TK1 and MMP9 expression levels had worse prognosis. These identified DEGs might not only be promising biomarkers for GBC diagnosis and prognosis, but also expedite the discovery of novel therapeutic strategies.

Characteristic adaptations of the extracellular matrix in dilated cardiomyopathy

Dilated cardiomyopathy (DCM) is a relatively common heart muscle disease characterized by the dilation and thinning of the left ventricle accompanied with left ventricular systolic dysfunction. Myocardial fibrosis is a major feature in DCM and therefore it is inevitable that corresponding extracellular matrix (ECM) changes are involved in DCM onset and progression. Increasing our understanding of how ECM adaptations are involved in DCM could be important for the development of future interventions. This review article discusses the molecular adaptations in ECM composition and structure that have been reported in both animal and human studies of DCM. Furthermore, we provide a transcriptome-based catalogue of ECM genes that are associated with DCM, generated by using NCBI Gene Expression Omnibus database sets for DCM. Based on this in silico analysis, many novel ECM components involved in DCM are identified and discussed in this review. With the information gathered, we propose putative pathways of ECM adaptations in onset and progression of DCM.

Extracellular Matrix and Dermal Fibroblast Function in the Healing Wound

Significance: Fibroblasts play a critical role in normal wound healing. Various extracellular matrix (ECM) components, including collagens, fibrin, fibronectin, proteoglycans, glycosaminoglycans, and matricellular proteins, can be considered potent protagonists of fibroblast survival, migration, and metabolism. Recent Advances: Advances in tissue culture, tissue engineering, and ex vivo models have made the examination and precise measurements of ECM components in wound healing possible. Likewise, the development of specific transgenic animal models has created the opportunity to characterize the role of various ECM molecules in healing wounds. In addition, the recent characterization of new ECM molecules, including matricellular proteins, dermatopontin, and FACIT collagens (Fibril-Associated Collagens with Interrupted Triple helices), further demonstrates our cursory knowledge of the ECM in coordinated wound healing. Critical Issues: The manipulation and augmentation of ECM components in the healing wound is emerging in patient care, as demonstrated by the use of acellular dermal matrices, tissue scaffolds, and wound dressings or topical products bearing ECM proteins such as collagen, hyaluronan (HA), or elastin. Once thought of as neutral structural proteins, these molecules are now known to directly influence many aspects of cellular wound healing. Future Directions: The role that ECM molecules, such as CCN2, osteopontin, and secreted protein, acidic and rich in cysteine, play in signaling homing of fibroblast progenitor cells to sites of injury invites future research as we continue investigating the heterotopic origin of certain populations of fibroblasts in a healing wound. Likewise, research into differently sized fragments of the same polymeric ECM molecule is warranted as we learn that fragments of molecules such as HA and tenascin-C can have opposing effects on dermal fibroblasts.

Pathoproteomic profiling of the skeletal muscle matrisome in dystrophinopathy associated myofibrosis

The gradual accumulation of collagen and associated proteins of the extracellular matrix is a crucial myopathological parameter of many neuromuscular disorders. Progressive tissue damage and fibrosis play a key pathobiochemical role in the dysregulation of contractile functions and often correlates with poor motor outcome in muscular dystrophies. Following a brief introduction into the role of the extracellular matrix in skeletal muscles, we review here the proteomic profiling of myofibrosis and its intrinsic role in X-linked muscular dystrophy. Although Duchenne muscular dystrophy is primarily a disease of the membrane cytoskeleton, one of its most striking histopathological features is a hyperactive connective tissue and tissue scarring. We outline the identification of novel factors involved in the modulation of the extracellular matrix in muscular dystrophy, such as matricellular proteins. The establishment of novel proteomic markers will be helpful in improving the diagnosis, prognosis, and therapy monitoring in relation to fibrotic substitution of contractile tissue. In the future, the prevention of fibrosis will be crucial for providing optimum conditions to apply novel pharmacological treatments, as well as establish cell-based approaches or gene therapeutic interventions. The elimination of secondary abnormalities in the matrisome promises to reduce tissue scarring and the loss of skeletal muscle elasticity.

DNA methylation-mediated silencing of matricellular protein dermatopontin promotes hepatocellular carcinoma metastasis by α3β1 integrin-Rho GTPase signaling

Dermatopontin (DPT), a tyrosine-rich, acidic matricellular protein, has been implicated in several human cancers. However, its biological functions and molecular mechanisms in cancer progression, particular hepatocellular carcinoma (HCC), remain unknown. We demonstrated that DPT was significantly down-regulated in 202 HCC clinical samples and that its expression level was closely correlated with cancer metastasis and patient prognosis. The overexpression of DPT dramatically suppressed HCC cell migration in vitro and intrahepatic metastasis in vivo. We further revealed that the down-regulation of DPT in HCC was due to epigenetic silencing by promoter DNA methylation. And the inhibitory effects of DPT on HCC cell motility were associated with dysregulated focal adhesion assembly, decreased RhoA activity and reduced focal adhesion kinase (FAK) and c-Src tyrosine kinase (Src) phosphorylation, and all of these alterations required the involvement of integrin signaling. Furthermore, we determined that the inhibitory effects of DPT on HCC cell motility were primarily mediated through α3β1 integrin. Our study provides new evidence for epigenetic control of tumor microenvironment, and suggests matricellular protein DPT may serve as a novel prognostic marker and act as a HCC metastasis suppressor.

Quantitative chemical proteomics for investigating the biomarkers of dioscin against liver fibrosis caused by CCl4 in rats

2D-DIGE technology was used for screening the biomarkers and drug-targets of dioscin against liver fibrosis in rats caused by CCl₄.

Role of dermatopontin in re-epithelialization: implications on keratinocyte migration and proliferation

Re-epithelialization is a key event in wound healing and any impairment in that process is associated with various pathological conditions. Epidermal keratinocyte migration and proliferation during re-epithelialization is largely regulated by the cytokines and growth factors from the provisional matrix and dermis. Extracellular matrix consists of numerous growth factors which mediate cell migration via cell membrane receptors. Dermatopontin (DPT), a non-collagenous matrix protein highly expressed in dermis is known for its striking ability to promote cell adhesion. DPT also enhances the biological activity of transforming growth factor beta 1 which plays a central role in the process of wound healing. This study was designed to envisage the role of DPT in keratinocyte migration and proliferation along with its mRNA and protein expression pattern in epidermis. The results showed that DPT promotes keratinocyte migration in a dose dependant fashion but fail to induce proliferation. Further, PCR and immunodetection studies revealed that the mRNA and protein expression of DPT is considerably negligible in the epidermis in contrast to the dermis. To conclude, DPT has a profound role in wound healing specifically during re-epithelialization by promoting keratinocyte migration via paracrine action from the underlying dermis.

Integrins in Wound Healing

Significance: Regulation of cell adhesions during tissue repair is fundamentally important for cell migration, proliferation, and protein production. All cells interact with extracellular matrix proteins with cell surface integrin receptors that convey signals from the environment into the nucleus, regulating gene expression and cell behavior. Integrins also interact with a variety of other proteins, such as growth factors, their receptors, and proteolytic enzymes. Re-epithelialization and granulation tissue formation are crucially dependent on the temporospatial function of multiple integrins. This review explains how integrins function in wound repair. Recent Advances: Certain integrins can activate latent transforming growth factor beta-1 (TGF-β1) that modulates wound inflammation and granulation tissue formation. Dysregulation of TGF-β1 function is associated with scarring and fibrotic disorders. Therefore, these integrins represent targets for therapeutic intervention in fibrosis. Critical Issues: Integrins have multifaceted functions and extensive crosstalk with other cell surface receptors and molecules. Moreover, in aberrant healing, integrins may assume different functions, further increasing the complexity of their functionality. Discovering and understanding the role that integrins play in wound healing provides an opportunity to identify the mechanisms for medical conditions, such as excessive scarring, chronic wounds, and even cancer. Future Directions: Integrin functions in acute and chronic wounds should be further addressed in models better mimicking human wounds. Application of any products in acute or chronic wounds will potentially alter integrin functions that need to be carefully considered in the design.

Plasticity of fibroblasts demonstrated by tissue-specific and function-related proteome profiling

Background

Fibroblasts are mesenchymal stromal cells which occur in all tissue types. While their main function is related to ECM production and physical support, they are also important players in wound healing, and have further been recognized to be able to modulate inflammatory processes and support tumor growth. Fibroblasts can display distinct phenotypes, depending on their tissue origin, as well as on their functional state.

Results

In order to contribute to the proteomic characterization of fibroblasts, we have isolated primary human fibroblasts from human skin, lung and bone marrow and generated proteome profiles of these cells by LC-MS/MS. Comparative proteome profiling revealed characteristic differences therein, which seemed to be related to the cell’s tissue origin. Furthermore, the cells were treated in vitro with the pro-inflammatory cytokine IL-1beta. While all fibroblasts induced the secretion of Interleukins IL-6 and IL-8 and the chemokine GRO-alpha, other inflammation-related proteins were up-regulated in an apparently tissue-dependent manner. Investigating fibroblasts from tumorous tissues of skin, lung and bone marrow with respect to such inflammation-related proteins revealed hardly any conformity but rather individual and tumor type-related variations. However, apparent up-regulation of IGF-II, PAI-1 and PLOD2 was observed in melanoma-, lung adenocarcinoma- and multiple myeloma-associated fibroblasts, as well as in hepatocellular carcinoma-associated fibroblasts.

Conclusions

Inflammation-related proteome alterations of primary human fibroblasts were determined by the analysis of IL-1beta treated cells. Tumor-associated fibroblasts from different tissue types hardly showed signs of acute inflammation but displayed characteristic functional aberrations potentially related to chronic inflammation. The present data suggest that the state of the tumor microenvironment is relevant for tumor progression and targeted treatment of tumor-associated fibroblasts may support anti-cancer strategies.

Electronic supplementary material

The online version of this article (doi:10.1186/1559-0275-11-41) contains supplementary material, which is available to authorized users.

Expression and integrity of dermatopontin in chronic cutaneous wounds: a crucial factor in impaired wound healing

Chronic cutaneous wound (CCW) is a major health care burden wherein the healing process is slow or rather static resulting in anatomical and functional restriction of the damaged tissue. Dysregulated expression and degradation of matrix proteins, growth factors and cytokines contribute to the disrupted and uncoordinated healing process of CCW. Therefore, therapeutic approaches for effective management of CCW should be focused towards identifying and manipulating the molecular defects, such as reduced bioavailability of the pro-healing molecules and elevated activity of proteases. This study essentially deals with assessing the expression and integrity of an extracellular matrix protein, Dermatopontin (DPT), in CCW using real-time quantitative reverse transcriptase PCR and immunological techniques. The results indicate that, despite DPT's high mRNA expression, the protein levels are markedly reduced in both CCW tissue and its exudate. To elucidate the cause for this contradiction in mRNA and protein levels, the stability of DPT is analyzed in the presence of wound exudates and various proteases that are naturally elevated in CCW. DPT was observed to be degraded at higher rates when incubated with certain recombinant proteases or chronic wound exudate. In conclusion, the susceptibility of DPT protein to specific proteases present at high levels in the wound milieu resulted in the degradation of DPT, thus leading to impaired healing response in CCW.

Functional peptide of dermatopontin produces fibrinogen fibrils and modifies its biological activity

BACKGROUND

Dermatopontin (DP), a small extracellular matrix protein, interacts with both fibrinogen and fibrin. DP accelerates fibrin fibril formation and enhances cell adhesion to fibrin fibrils but DP does not influence fibrinogen fibril formation. We have previously demonstrated that DP-4 (PHGQVVVAVRS) is a functional dermatopontin peptide (Wu et al., 2014).

OBJECTIVE

Identification of biological functions of DP-4.

METHODS

Protein-protein interactions were examined by solid-phase assay. The kinetics of fibrinogen/fibrin polymer formation was monitored by turbidity change, SDS-PAGE, and electron microscopy. A cell adhesion assay was performed using human umbilical vein endothelial cells.

RESULTS

Although DP promoted fibrin formation, the DP-4 peptide promoted fibrinogen polymerization but did not apparently affect fibrin formation. The polymerized fibrinogen formed straight solid fibrils comparable to the normally formed fibrin fibrils. A minimum functional sequence of the DP-4 peptide was determined to be VVVAVRS. An αC domain in fibrinogen was involved in the fibril formation. Fibrinogen fibrils made by DP-4 enhanced endothelial cell adhesion and spreading in a dose-dependent manner. This cell adhesion was inhibited by heparin and by anti-αvβ3 and β1 integrin antibodies.

CONCLUSION

DP-4 did not reproduce the full functional biological activities of DP with fibrin but DP-4 did promote fibrinogen fibril formation. The fibrinogen fibrils produced by DP-4 are useful as a novel synthetic biomaterial for therapeutic applications.

Proteomic analysis of equine amniotic membrane: characterization of proteins

INTRODUCTION

Human amniotic membrane (AM) has been used as a biomaterial for surgical wound skin and ocular surface reconstruction for several years. Currently, equine AM has been used for corneal reconstruction in several animal species, and appears to have the same properties as human AM. Despite the observed positive healing abilities of this tissue in horses with ulcerative keratitis the proteins of equine AM have not been described.

OBJECTIVE

To identify proteins known to be associated with corneal healing from frozen equine AM.

PROCEDURES

Placentas were acquired from healthy live foal births from a local Thoroughbred breeding farm. The amnion was removed from the chorion by blunt dissection, washed with phosphate-buffered saline (PBS), and treated with 0.05% trypsin and 0.02% ethylene diaminetetraacetic acid in PBS. Amnion was attached to nitrocellulose paper (epithelial side up), and cut into 4 × 4 cm pieces. The sheets were frozen at -80 °C. The protein samples were solubilized, and analyzed by 2D gel electrophoresis and shotgun proteomics.

RESULTS

A reference identification map of the equine AM proteins was produced and 149 different proteins were identified. From gel-based proteomics, 49 spots were excised and 43 proteins identified by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). Shotgun proteomics identified 116 proteins with an overlap of 10 proteins in both analyses.

CONCLUSIONS

We have described a reference map for equine AM proteins that may provide a background to explain the positive results found in horses with ulcerative keratopathies using this biomaterial.

Gene expression in superior temporal cortex of schizophrenia patients

We investigated gene expression pattern obtained from microarray data of 10 schizophrenia patients and 10 control subjects. Brain tissue samples were obtained postmortem; thus, the different ages of the patients at death also allowed a study of the dynamic behavior of the expression patterns over a time frame of many years. We used statistical tests and dimensionality reduction methods to characterize the subset of genes differentially expressed in the two groups. A set of 10 genes were significantly downregulated, and a larger set of 40 genes were upregulated in the schizophrenia patients. Interestingly, the set of upregulated genes includes a large number of genes associated with gene transcription (zinc finger proteins and histone methylation) and apoptosis. We furthermore identified genes with a significant trend correlating with age in the control (MLL3) or the schizophrenia group (SOX5, CTRL). Assessments of correlations of other genes with the disorder (RRM1) or with the duration of medication could not be resolved, because all patients were medicated. This hypothesis-free approach uncovered a series of genes differentially expressed in schizophrenia that belong to a number of distinct cell functions, such as apoptosis, transcriptional regulation, cell motility, energy metabolism and hypoxia.

Dermatopontin regulates fibrin formation and its biological activity

Dermatopontin (DP) is a small extracellular matrix component in the dermis. Fibrin is a major component of a provisional matrix that is formed just after wounding. Previously, we found that DP was present in the provisional matrix, and it interacted with fibrin. Here, we examined the role of DP on fibrin function. DP interacted with both the fibrin monomer and fibrils, and was incorporated into the fibrils during fibrin formation. A DP sequence, PHGQVVVAVRS, was identified as a fibrin-binding site, and a globular D domain of fibrin was the binding site for DP. DP accelerated fibrin fibril formation into structurally modified fibrils. Fibrin fibrils formed in the presence of DP enhanced both endothelial cell attachment and cell spreading. The attached cells developed a more organized cytoskeleton when compared with those that attached to fibrin fibrils only. The main receptor for cell adhesion was identified as αvβ3 integrin, and a cooperating receptor was a β1-containing integrin species, probably α5β1 integrin. These results indicate that DP can modify certain biological functions of fibrin, and thus a another function of this extracellular matrix protein was revealed. In addition, the fibrin-DP complex might become useful for developing an improved artificial matrix for improving wound healing.

Spatiotemporal expression of the dermatopontin gene in zebrafish Danio rerio

There has been significant interest in the expression and function of dermatopontin (DPT) in mammals owing to recent evidence pointing to its critical role in collagen fibrillogenesis. Despite this interest, limited information is available about the site/s of DPT mRNA expression or changes in expression in vivo. We used reverse-transcription polymerase chain reaction and in situ hybridization to evaluate the spatial and temporal pattern of DPT mRNA expression in zebrafish, Danio rerio, a widely used vertebrate model. We observed that DPT transcripts were expressed in zebrafish embryos at all developmental stages in a range of tissues, including the brain and optic neuron cells. Based on our results, we hypothesize that DPT may also play a role in neural functions in vivo.