Cloning of murine early quiescence-1 gene: the murine counterpart of dermatopontin gene can induce and be induced by cell quiescence

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.

Age-Related Alterations in the Testicular Proteome of a Non-Human Primate

Aging of human testis and associated cellular changes is difficult to assess. Therefore, we used a translational, non-human primate model to get insights into underlying cellular and biochemical processes. Using proteomics and immunohistochemistry, we analyzed testicular tissue of young (age 2 to 3) and old (age 10 to 12) common marmosets (Callithrix jacchus). Using a mass spectrometry-based proteomics approach, we identified 63,124 peptides, which could be assigned to 5924 proteins. Among them, we found proteins specific for germ cells and somatic cells, such as Leydig and Sertoli cells. Quantitative analysis showed 31 differentially abundant proteins, of which 29 proteins were more abundant in older animals. An increased abundance of anti-proliferative proteins, among them CDKN2A, indicate reduced cell proliferation in old testes. Additionally, an increased abundance of several small leucine rich repeat proteoglycans and other extracellular matrix proteins was observed, which may be related to impaired cell migration and fibrotic events. Furthermore, an increased abundance of proteins with inhibitory roles in smooth muscle cell contraction like CNN1 indicates functional alterations in testicular peritubular cells and may mirror a reduced capacity of these cells to contract in old testes.

Tumour-promoting activity of polycyclic aromatic hydrocarbons and their oxygenated or nitrated derivatives

Various types of polycyclic aromatic compounds (PACs) in diesel exhaust particles are thought to contribute to carcinogenesis in mammals. Although the carcinogenicity, mutagenicity and tumour-initiating activity of these compounds have been evaluated, their tumour-promoting activity is unclear. In the present study, to determine the tumour-inducing activity of PACs, including previously known mutagenic compounds in atmospheric environments, a transformation assay for promoting activity mediated by the release of contact inhibition was conducted for six polycyclic aromatic hydrocarbons (PAHs), seven oxygenated PAHs (oxy-PAHs) and seven nitrated PAHs (nitro-PAHs) using mouse embryonic fibroblast cells transfected with the v-Ha-ras gene (Bhas 42 cells). Of these, two PAHs [benzo[k]fluoranthene (B[k]FA) and benzo[b]fluoranthene (B[b]FA)], one oxy-PAH [6H-benzo[cd]pyren-6-one (BPO)] and two nitro-PAHs (3-nitro-7H-benz[de]anthracen-7-one and 6-nitrochrysene) were found to exhibit particularly powerful tumour-promoting activity (≥10 foci following exposure to <100nM). In addition, clear mRNA expression of CYP1A1, which is associated with aryl hydrocarbon receptor (AhR)-mediated activation, was observed following the exposure of cells to two PAHs (B[k]FA and B[b]FA) and three oxy-PAHs (1,2-naphthoquinone, 11H-benzo[b]fluoren-11-one and BPO). Further, an HO-1 antioxidant response activation was observed following exposure to B[k]FA, B[b]FA and BPO, suggesting that the induction of tumour-promoting activity in these compounds is correlated with the dysfunction of signal transduction via AhR-mediated responses and/or oxidative stress responses.

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.

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.

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.

Dermatopontin promotes adhesion, spreading and migration of cardiac fibroblasts in vitro

Dermatopontin (DPT), an extracellular matrix (ECM) protein, has been previously shown to be upregulated in the infarct zone of experimentally induced myocardial infarction (MI) rats. However, the accurate role that DPT exerts in the ventricular remodeling process after MI remains poorly understood. In this study, we evaluated the expression pattern of DPT mRNA and protein as well as its secretion in cultured neonatal rat cardiomyocytes (CMs) and cardiac fibroblasts (CFs) under conditions of hypoxia and serum deprivation (hypoxia/SD). Further, we tested the possible roles of DPT in CFs adhesion, spreading, migration and proliferation, which greatly promote the ventricular remodeling process after MI. Results showed that hypoxia/SD stimulated DPT expression and secretion in CMs and CFs and that DPT promoted adhesion, spreading and migration of CFs whereas had no effect on CFs proliferation. In addition, functional blocking antibodies specific for integrin α3 and β1 significantly reduced CFs adhesion and migration that DPT induced, suggesting that integrin α3β1 is at least one receptor for CFs adhesion and migration to DPT. These results implicated that DPT participates in the ventricular remodeling process after MI and may act as a potential therapeutic target for ventricular remodeling.

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

We report that dermatopontin (DP), an abundant dermal extracellular matrix protein, is found in the fibrin clot and in the wound fluid, which comprise the provisional matrix at the initial stage of wound healing. DP was also found in the serum but at a lower concentration than that in wound fluid. DP co-localized with both fibrin and fibronectin on fibrin fibers and interacted with both proteins. Both normal fibroblast and HT1080 cell adhesion to the fibrin-fibronectin matrix were dose-dependently enhanced by DP, and the adhesion was mediated by α5β1 integrin. The cytoskeleton was more organized in the cells that adhered to the fibrin-fibronectin-DP complex. When incubated with DP, fibronectin formed an insoluble complex of fibronectin fibrils as visualized by electron microscopy. The interacting sites of fibronectin with DP were the first, thirteenth, and fourteenth type III repeats (III(1), III(13), and III(14)), with III(13) and III(14) assumed to be the major sites. The interaction between III(2-3) and III(12-14) was inhibited by DP, whereas the interaction between I(1-5) and III(12-14) was specifically and strongly enhanced by DP. Because the interaction between III(2-3) and III(12-14) is involved in forming a globular conformation of fibronectin, and that between I(1-5) and III(12-14) is required for forming fibronectin fibrils, DP promotes fibronectin fibril formation probably by changing the fibronectin conformation. These results suggest that DP has an accelerating role in fibroblast cell adhesion to the provisional matrix in the initial stage of wound healing.

Dermatopontin is expressed in human liver and is downregulated in hepatocellular carcinoma

Dermatopontin (DPT) was recently found as a downstream target of vitamin D receptor, which is a key molecule in the 1,25-dihydroxy-vitamin D(3) anti-hepatoma proliferation pathway. MCTx-1 from Millepora, a homolog of DPT, is identified as a cytotoxin towards leukemia cells. The aim of this study was to analyze DPT expression in hepatocellular carcinoma (HCC) based on the analysis for DPT gene in normal tissues in order to estimate its function in the progression of HCC. DPT mRNA expression was analyzed in normal tissues and HCC cell lines by RT-PCR, and in HCC tissue by RT-PCR and real-time PCR. Its protein was examined in HCC tissues by Western blot and immunohistochemistry assays. Meanwhile, transforming growth factor-beta1 (TGF-beta1) that is closely associated with HCC and DPT was observed by immunohistochemistry in HCC tissues. The results showed that DPT mRNA was strongly expressed in human fetal and adult liver, kidney, and spleen, weakly in ovary and heart, and absent in other tissues and HCC cell lines examined. Its mRNA was significantly downregulated in HCC tissues, while its protein was weakly expressed in tumor compared with non-tumor. DPT is located mainly in the cytoplasm of several cell types in the liver; it has been identified also in the extracellular matrix of the skin. TGF-beta1 was observed in extensive tumor tissue of HCC. This fact suggests that DPT can play various roles in different tissues and might be a molecule related to carcinogenesis and the progression of HCC via possible interaction with TGF-beta1 and other potential mechanisms.

Dermatopontin promotes epidermal keratinocyte adhesion via alpha3beta1 integrin and a proteoglycan receptor

Dermatopontin, an extracellular matrix component initially purified from bovine dermis, promoted cell adhesion of the human epidermal keratinocyte cell line (HaCaT cells). HaCaT cells spread on dermatopontin and formed actin fibers. Adhesion of HaCaT cells to dermatopontin was inhibited by both EDTA and heparin and was mediated in part by alpha3beta1 integrin. A synthetic peptide (DP-4, PHGQVVVAVRS; bovine dermatopontin residues 33-43) specifically inhibited adhesion of cells to dermatopontin, and when the DP-4 peptide was coated on the well, it promoted cell adhesion in a dose-dependent manner. An active core sequence of the DP-4 peptide was localized to an eight-amino acid sequence (GQVVVAVR). These results indicate that dermatopontin is a novel epidermal cell adhesion molecule and suggest that the DP-4 sequence is critical for the cell adhesive activity of dermatopontin. Adhesion of cells to DP-4 was strongly inhibited by heparin. When HaCaT cells were treated with heparitinase I, the cells failed to adhere to DP-4 but chondroitinase ABC treatment did not influence the adhesion activity. DP-4 specifically interacted with biotinylated heparin, and this interaction was inhibited by unlabeled heparin. DP-4 peptide significantly promoted the adhesion of cells overexpressing syndecans, and syndecan bound to a DP-4 peptide affinity column. These results suggest that HaCaT cells adhere to dermatopontin through alpha3beta1 integrin and a heparan sulfate proteoglycan-type receptor, which is likely a syndecan. We conclude that dermatopontin plays a role as a multifunctional adhesion molecule for epidermal cells.

Transcriptomic characterization of the long-term dihydrotestosterone effects in adipose tissue

OBJECTIVE

To study the long-term transcriptomic effects of dihydrotestosterone (DHT) in adipose tissue. Fat distribution is regulated by sexual hormones. It is still unclear if androgens are promoting or reducing intra-abdominal fat accumulation.

RESEARCH METHODS AND PROCEDURES

Retroperitoneal adipose tissue were isolated from each group of gonadectomized (GDX) C57BL6 male mice treated with vehicle or DHT for 21 days. Serial analysis of gene expression (SAGE) was performed to generate approximately 150,000 SAGE tags from each sample.

RESULTS

Among the numerous genes regulated by DHT, transcripts involved in glycolysis, such as aldolase 1 A isoform and pyruvate kinase muscle as well as lipogenic transcripts, such as malic enzyme supernatant and ELOVL family member 6 elongation of long chain fatty acids were down-regulated by androgen supplementation. In contrast, transcripts involved in lipolysis and fatty acid oxidation, such as carboxylesterase 3, acetyl-coenzyme A acyltransferase 1, 3-ketoacyl-CoA thiolase B and enoyl-coenzyme A hydratase/3-hydroxyacyl coenzyme A dehydrogenase were up-regulated by DHT. Pro-apoptotic transcripts such as cell death-inducing DFFA-like effector c, BCL2/adenovirus E1B 19 kDa-interacting protein 1 NIP3 and -interacting protein 3-like were up-regulated by DHT, whereas transcripts involved in promotion of cell cycle such as cyclin D2 were down-regulated by DHT.

DISCUSSION

These results suggest that chronic androgen treatment may help to improve metabolic profile by regulating various critical pathways involved in adipose tissue physiology. In addition, several genes associated with a healthier metabolic profile, such as adiponectin and CD36 antigen, were up-regulated by 21 days of DHT treatment.

Dermatopontin, a novel player in the biology of the extracellular matrix

Dermatopontin is a widely distributed small molecular weight protein in the extracellular matrix (ECM) and today its homologues are known in five mammals and several invertebrates. The structures of these homologues are relatively well conserved among the species. In the skin, dermatopontin is located mainly on the surface of the collagen fibers. It is found in the conditioned medium and also in the cytoplasm of cultured fibroblasts. Early studies focused on ECM assembly (collagen fibrillogenesis) and interactions (with the proteoglycan decorin). Subsequently, a targeted disruption of dermatopontin resulted in a phenotype similar to Ehlers-Danlos syndrome. In addition, a cell adhesion activity of this protein for dermal fibroblasts and several other cells was found, and this activity might suggest this protein's involvement in wound healing. The expression of dermatopontin around an infarct zone of experimental myocardial infarction may support this possibility. In invertebrates, dermatopontin homologues act mainly as adhesion/agglutination molecules. In addition, we found that transforming growth factor-beta1 interacts with dermatopontin and the function of this cytokine is modified by dermatopontin. Recently, the involvement of this protein in cell proliferation has been indicated. In this review we describe the reported functions of this protein and speculate on the multiple roles of this largely uncharacterized matrix molecule.