Fibronectin Matrix Research Articles

Regulation of Vascular Smooth Muscle Cell Stiffness and Adhesion by [Ca2+]i: An Atomic Force Microscopy-Based Study - CORRIGENDUM.

The intracellular concentration of calcium ion ([Ca2+]i) is a critical regulator of cell signaling and contractility of vascular smooth muscle cells (VSMCs). In this study, we employed an atomic force microscopy (AFM) nanoindentation-based approach to investigate the role of [Ca2+]i in regulating the cortical elasticity of rat cremaster VSMCs and the ability of rat VSMCs to adhere to fibronectin (Fn) matrix. Elevation of [Ca2+]i by ionomycin treatment increased rat VSMC stiffness and cell adhesion to Fn-biofunctionalized AFM probes, whereas attenuation of [Ca2+]i by 1,2-Bis (2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid tetrakis (acetoxymethyl ester) (BAPTA-AM) treatment decreased the mechanical and matrix adhesive properties of VSMCs. Furthermore, we found that ionomycin/BAPTA-AM treatments altered expression of α 5 integrin subunits and α smooth muscle actin in rat VSMCs. These data suggest that [Ca2+]i regulates VSMC elasticity and adhesion to the extracellular matrix by a potential mechanism involving changing dynamics of the integrin-actin cytoskeleton axis.

The effect of substrate bulk stiffness on focal and fibrillar adhesion formation in human abdominal aortic endothelial cells

Endothelial cell (EC) dysfunction contributes to atherosclerosis, which is associated with arterial stiffening and fibronectin (FN) deposition, by ECs and smooth muscle cells (SMCs). The effect of stiffness on the EC/FN interaction and fibrillar adhesion formation has been poorly studied. An in vitro model was prepared that included FN-coated polydimethylsiloxane (PDMS) films with similar hydrophobicity and roughness but distinct Young's modulus values, mimicking healthy (1.0 MPa) and atherosclerotic (2.8 MPa) arteries. Human aortic abdominal endothelial cells (HAAECs) seeded on 1.0 MPa PDMS films spread over time and reached their maximum surface area faster than on 2.8 MPa PDMS films. In addition, HAAECs appeared to organize focal adhesion more rapidly on 1.0 MPa PDMS films, despite the similar cell binding domain accessibility to adsorbed FN. Interestingly, we also observed up to a ~5-fold increase in the percentage of HAAECs that had a well-developed fibrillar adhesion on 1.0 MPa compared to 2.8 MPa PDMS films as verified by integrin α5 subunits, tensin, and FN staining. This variation did not affect EC migration. These results suggest that there are favourable conditions for FN matrix assembly by ECs in early atherosclerosis rather than at advanced stages. Our in vitro model will therefore be helpful to understand the influence of bulk stiffness on cells involved in atherosclerosis.

Regulation of Vascular Smooth Muscle Cell Stiffness and Adhesion by [Ca2+]i: An Atomic Force Microscopy-Based Study.

The intracellular concentration of calcium ion ([Ca2+]i) is a critical regulator of cell signaling and contractility of vascular smooth muscle cells (VSMCs). In this study, we employed an atomic force microscopy (AFM) nanoindentation-based approach to investigate the role of [Ca2+]i in regulating the cortical elasticity of rat cremaster VSMCs and the ability of rat VSMCs to adhere to fibronectin (Fn) matrix. Elevation of [Ca2+]i by ionomycin treatment increased rat VSMC stiffness and cell adhesion to Fn-biofunctionalized AFM probes, whereas attenuation of [Ca2+]i by 1,2-Bis (2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid tetrakis (acetoxymethyl ester) (BAPTA-AM) treatment decreased the mechanical and matrix adhesive properties of VSMCs. Furthermore, we found that ionomycin/BAPTA-AM treatments altered expression of α 5 integrin subunits and α smooth muscle actin in rat VSMCs. These data suggest that [Ca2+]i regulates VSMC elasticity and adhesion to the extracellular matrix by a potential mechanism involving changing dynamics of the integrin-actin cytoskeleton axis.

Astragaloside IV ameliorates high glucose‑induced renal tubular epithelial‑mesenchymal transition by blocking mTORC1/p70S6K signaling in HK‑2 cells.

Astragaloside IV (AST) is the major active saponin in Astragalus membranaceus and, reportedly, has a variety of pharmacological activities. However, the potential of AST to ameliorate high glucose-mediated renal tubular epithelial-mesenchymal transition (EMT) remains undetermined. The aim of the present research was to explore the effect and mechanism of AST in EMT of renal tubular epithelial cells, as an underlying mechanism of renal fibrosis and a vital feature involved in diabetic nephropathy. The effect of AST on the EMT of renal tubular epithelial cells (HK-2) stimulated by high glucose was investigated and it was attempted to elucidate the potential underlying mechanism. The expression of E-cadherin and α-smooth muscle actin were determined by western blotting and immunofluorescence assays. The expression of the mammalian target of rapamycin complex 1 (mTORC1)/ ribosomal protein S6 kinase β-1 (p70S6K) signaling pathway and protein levels of four transcriptional factors (snail, slug, twist and zinc finger E-box-binding homeobox 1) were also determined by western blotting. Additionally, extracellular matrix components, including fibronectin (FN) and collagen type IV (Col IV) were detected by ELISA. The results suggested that the EMT of HK-2 cells and the mTORC1/p70S6K pathway were activated by high glucose. The expression of snail and twist in HK-2 cells was elevated by high glucose. Furthermore, extracellular matrix components, FN and Col IV, were increased in HK-2 cells cultured with high glucose. In turn, treatment with AST reduced EMT features in HK-2 cells, inhibited mTORC1/p70S6K pathway activation, downregulated expression of snail and twist, and reduced secretion of FN and Col IV. In summary, the findings suggested that AST ameliorates high glucose-mediated renal tubular EMT by blocking the mTORC1/p70S6K signaling pathway in HK-2 cells.

Whole rat stomach decellularisation using a detergent-enzymatic protocol

BackgroundConditions leading to reduced gastric volume are difficult to manage and are associated to poor quality-of-life. Stomach augmentation using a tissue-engineered stomach is a potential solution to restore adequate physiology and food reservoir. Aim of this study was to evaluate the decellularisation of whole rat stomach using a detergent-enzymatic protocol.MethodsStomachs harvested from rats were decellularised through luminal and vascular cannulation using 24-h detergent-enzymatic treatment and completely characterized by appropriate staining, DNA and Extracellular matrix -component quantifications.ResultsThe detergent-enzymatic protocol allows a complete decellularisation of the gastric tissue, with a complete removal of the DNA with two cycles as confirmed by both quantifications and histological analysis. Extracellular matrix components, collagen, fibronectin, laminin and elastin, were optimally preserved by the treatment, while glycosaminoglycans were reduced.ConclusionGastric tissue can be efficiently decellularised. Scaffolds retained original structure and important components that could enhance integration with other tissues for in vivo transplant. The use of naturally derived material could be potentially considered for the treatment of both congenital and acquired conditions.

Assembly of fibronectin fibrils selectively attenuates platelet-derived growth factor–induced intracellular calcium release in fibroblasts

Cellular responses to platelet-derived growth factor (PDGF) are altered in a variety of pathological conditions, including cancers, fibroses, and vascular diseases, making PDGF-induced signaling pathways important therapeutic targets. The limited success of therapies designed to impact PDGF pathways may be overcome with a clearer understanding of how cells integrate signals from PDGF and the extracellular matrix (ECM). Here, we assessed the effects of fibronectin matrix assembly on the responsiveness of mesenchymal cells to PDGF. Our results indicate that fibroblast-mediated assembly of fibronectin fibrils attenuates intracellular calcium release in response to PDGF. The dose-dependent inhibition of PDGF-induced intracellular calcium release was specific to the ECM form of fibronectin. Further, a recombinant protein engineered to mimic ECM fibronectin similarly attenuated intracellular calcium release in response to PDGF. Of note, fibronectin attenuated the PDGF-calcium signaling axis at the level of phosphoinositide 3-kinase (PI3K) activation. Interestingly, ECM fibronectin did not alter other intracellular signals activated by PDGF, including activation of PDGF receptor β, AKT Ser/Thr kinase, phospholipase Cγ1, and extracellular signal-regulated kinase 1/2 (ERK1/2). Rather, fibronectin inhibited activation of the p55 regulatory subunit of PI3K in response to a variety of stimuli, indicating that ECM fibronectin selectively attenuates the intracellular calcium release cascade while leaving intact other PDGF signaling pathways. Selective regulation of calcium signaling by ECM fibronectin via the p55 regulatory subunit of PI3K represents a mechanism by which cells tune their response to PDGF and may therefore serve as a target to selectively regulate one branch of PDGF signaling.

Autocrine Fibronectin Inhibits Breast Cancer Metastasis.

Both epithelial-mesenchymal transition (EMT) and mesenchymal-epithelial transition (MET) are linked to metastasis via their ability to increase invasiveness and enhance tumor-initiating capacity. Growth factors, cytokines, and chemotherapies present in the tumor microenvironment (TME) are capable of inducing EMT, but the role of the extracellular matrix (ECM) in this process remains poorly understood. Here, a novel tessellated three-dimensional (3D) polymer scaffolding is used to produce a fibrillar fibronectin matrix that induces an EMT-like event that includes phosphorylation of STAT3 and requires expression of β1 integrin. Consistent with these findings, analysis of the METABRIC dataset strongly links high-level fibronectin (FN) expression to decreased patient survival. In contrast, in vitro analysis of the MCF-10A progression series indicated that intracellular FN expression was associated with nonmetastatic cells. Therefore, differential bioluminescent imaging was used to track the metastasis of isogenic epithelial and mesenchymal cells within heterogeneous tumors. Interestingly, mesenchymal tumor cells do not produce a FN matrix and cannot complete the metastatic process, even when grown within a tumor containing epithelial cells. However, mesenchymal tumor cells form FN-containing cellular fibrils capable of supporting the growth and migration of metastatic-competent tumor cells. Importantly, depletion of FN allows mesenchymal tumor cells to regain epithelial characteristics and initiate in vivo tumor growth within a metastatic microenvironment.Implications: In contrast to the tumor-promoting functions of fibronectin within the ECM, these data suggest that autocrine fibronectin production inhibits the metastatic potential of mesenchymal tumor cells. Mol Cancer Res; 16(10); 1579-89. ©2018 AACR.

Tetraspanin CD82 represses Sp1-mediated Snail expression and the resultant E-cadherin expression interrupts nuclear signaling of β-catenin by increasing its membrane localization

Tetraspanin membrane proteins form physical complexes with signaling molecules and have been suggested to influence the signaling events of associated molecules. Of the tetraspanin proteins, CD82 has been shown to promote homotypic cell-cell adhesion, which partially accounts for its role in suppressing cancer invasion and metastasis. We found here that CD82-induced cell-cell adhesion is attributed to increased E-cadherin expression through CD82-mediated downregulation of the E-cadherin repressor Snail. The Snail repression by CD82 resulted from the reduced binding of the Sp1 transcription factor to the Snail gene promoter. Notably, high CD82 expression did not allow the fibronectin matrix to induce Sp1 phosphorylation, implicating CD82 inhibition of the fibronectin-integrin signaling-dependent Sp1 activation. Meanwhile, E-cadherin upregulated by CD82 pulled β-catenin up to the membrane region, and consequently reduced the amount of cytoplasmic β-catenin that was able to move into to the nucleus. The Wnt signal-induced nuclear translocation of β-catenin was also inhibited by the CD82 function of upregulating E-cadherin. Overall, high CD82 expression was likely to suppress fibronectin adhesion-induced Sp1 activation signaling for Snail expression, resulting in continuous E-cadherin expression, which contributed not only to the maintenance of strong cell-cell adhesion but also to the blockage of nuclear β-catenin signaling.

ADAM8 localizes to extravillous trophoblasts within the maternal-fetal interface and potentiates trophoblast cell line migration through a β1 integrin-mediated mechanism.

Does A Disintegrin And Metalloproteinase 8 (ADAM8) control extravillous trophoblast (EVT) differentiation and migration in early human placental development? ADAM8 mRNA preferentially localizes to invasive HLA-G-positive trophoblasts, associates with the acquirement of an EVT phenotype and promotes trophoblast migration through a mechanism requiring β1-integrin. Placental establishment in the first trimester of pregnancy requires the differentiation of progenitor trophoblasts into invasive EVTs that produce a diverse repertoire of proteases that facilitate matrix remodeling and activation of signaling pathways important in controlling cell migration. While multiple ADAM proteases, including ADAM8, are highly expressed by invasive trophoblasts, the role of ADAM8 in controlling EVT-related processes is unknown. First trimester placental villi and decidua (6-12 weeks' gestation), primary trophoblasts and trophoblastic cell lines (JEG3, JAR, Bewo, HTR8/SVNeo) were used to examine ADAM8 expression, localization and function. All experiments were performed on at least three independent occasions (n = 3). Placental villi and primary trophoblasts derived from IRB approved first trimester placental (n = 24) and decidual (n = 4) were used to examine ADAM8 localization and expression by in situ RNAScope hybridization, flow cytometry, quantitative PCR and immunoblot analyses. Primary trophoblasts were differentiated into EVT-like cells by plating on fibronectin and were assessed by immunofluorescence microscopy and immunoblot analysis of keratin-7, vimentin, epidermal growth factor receptor (EGFR), HLA-G and ADAM8. ADAM8 function was examined in primary EVTs and trophoblastic cell lines utilizing siRNA-directed silencing and over-expression strategies. Trophoblast migration was assessed using Transwell chambers, cell-matrix binding was tested using fibronectin-adhesion assays, and ADAM8-β1-integrin interactions were determined by immunofluorescence microscopy, co-immunoprecipitation experiments and function-promoting/inhibiting antibodies. Within first trimester placental tissues, ADAM8 preferentially localized to HLA-G+ trophoblasts residing within anchoring columns and decidua. Functional experiments in primary trophoblasts and trophoblastic cell lines show that ADAM8 promotes trophoblast migration through a mechanism independent of intrinsic protease activity. We show that ADAM8 localizes to peri-nuclear and cell-membrane actin-rich structures during cell-matrix attachment and promotes trophoblast binding to fibronectin matrix. Moreover, ADAM8 potentiates β1-integrin activation and promotes cell migration through a mechanism dependent on β1-integrin function. The primary limitation of this study was the use of in vitro experiments in examining ADAM8 function, as well as the implementation of immortalized trophoblastic cell lines. Histological localization of ADAM8 within placental and decidual tissue sections was limited to mRNA level analysis. Further, patient information corresponding to tissues obtained by elective terminations was not available. The novel non-proteolytic pro-migratory role for ADAM8 in controlling trophoblast migration revealed by this study sheds insight into the importance of ADAM8 in EVT biology and placental development. This work was supported by grants from the Natural Sciences and Engineering Research Council of Canada (NSERC-Discovery Grant) and the Canadian Institutes of Health Research (CIHR-Open Operating Grant). There are no conflicts or competing interests. NA.

Abstract A25: Tissue transglutaminase interacts with Frizzled 7 in ovarian cancer stem cells

Abstract Increasing evidence correlates the metastatic progression and post-chemotherapy recurrence of ovarian cancer (OC) to a small population of cancer stem cells (CSCs), resistant to traditional chemotherapy and responsible for tumor relapse. Tissue transglutaminase (TG2) is a multifunctional protein, with enzymatic and scaffold functions, overexpressed in ovarian carcinomas, where it promotes metastasis. Independently of its enzymatic function, TG2 can be secreted in the extracellular compartment where it increases cell adhesion to the fibronectin (FN) matrix by regulating integrins clustering and matrix reorganization. We hypothesized that by binding to the integrins and FN, TG2 promotes survival of CSCs and supports OC spheroid formation. Our data demonstrate that TG2, β1 integrin, and FN1 expression are markedly increased in OC spheroids compared with monolayers and are enriched in successive sphere generations. Immunofluorescence (IF) staining supports that TG2 forms abundant complexes with β1 integrin and FN in cells grown as spheroids. TG2 expression is strongly correlated with β1 integrin (ITGB1) (R=0.23, P<0.0001) and with FN1 (R=0.39, P<0.0001) in the TCGA ovarian cancer database, which houses gene expression data of 560 clinically annotated HGSOC tumors. Patients with high TG2 and ITGB1 expression levels had an increased estimated risk of death when compared to those with low TG2 and ITGB1 expression levels (P=0.00652). Use of function-inhibiting antibody against the FN-binding domain of TG2 (4G3) dramatically suppressed TG2/FN/β1 integrin complex formation, spheroid proliferation, and tumor growth in a xenograft model. Furthermore, disruption of TG2/FN complex formation altered key oncogenic signaling pathways, and in particular blocked the canonical Wnt/β-catenin signaling pathway essential to sustaining cancer cell stemness. The Wnt receptor Frizzled genes (Fzd1, Fzd7 and Fzd8) showed the greatest difference in gene expression, indicating a direct correlation between TG2/FN complex and Wnt pathway activation. By co-immunoprecipitation and IF staining we demonstrated that TG2 colocalizes and directly binds to Fzd7 receptor. In conclusion, our data support that TG2/FN/β1 integrin complex formation is essential to promoting ovarian CSCs survival by acting as coreceptor complex with Fzd7 in regulating β-catenin signaling and represents a new target to eradicate chemotherapy-resistant tumors. Citation Format: Salvatore Condello, Livia Sima, Cristina Ivan, Horacio Cardenas, Gary Schiltz, Rama K Mishra, Daniela Matei. Tissue transglutaminase interacts with Frizzled 7 in ovarian cancer stem cells. [abstract]. In: Proceedings of the AACR Conference: Addressing Critical Questions in Ovarian Cancer Research and Treatment; Oct 1-4, 2017; Pittsburgh, PA. Philadelphia (PA): AACR; Clin Cancer Res 2018;24(15_Suppl):Abstract nr A25.

Triptolide inhibits TGF-β-induced matrix contraction and fibronectin production mediated by human Tenon fibroblasts.

To determine if triptolide influences the contractility and fibronectin production in human Tenon fibroblasts (HTFs). HTFs were cultured in type I collagen gels with or without transforming growth factor beta (TGF-β) and/or triptolide. The diameter of the collagen gel was used to measure contraction. Immunoblot analysis was used to quantify myosin light chain (MLC) phosphorylation and integrin expression. Laser confocal fluorescence microscopy was used to monitor the formation of actin stress fibers. Fibronectin production was measured with an enzyme immunoassay. Triptolide inhibition of contraction in TGF-β-induced collagen gel mediated by HTFs was dose-dependent and statistically significant at 3 nmol/L (P<0.05) and maximal at 30 nmol/L and significantly time dependent at 2d (P<0.05). Triptolide reduced TGF-β-induced expression of integrins α5 and β1, phosphorylation of MLC, and formation of stress fibers in HTFs. Furthermore, the inhibition of triptolide on the attenuated TGF-β-induced production of fibronectin by HTFs was concentration-dependent and significant at 1 nmol/L (P<0.05) and maximal at 30 nmol/L. Triptolide suppress the contractility of HTFs induced by TGF-β and the production of fibronectin by these cells. It is promising that triptolide treatment may possibly inhibit scar formation after glaucoma filtration surgery.

Fibronectin Produced by Cerebral Endothelial and Vascular Smooth Muscle Cells Contributes to Perivascular Extracellular Matrix in Late-Delayed Radiation-Induced Brain Injury.

Late-delayed radiation-induced brain injury (RIBI) is a major adverse effect of fractionated whole-brain irradiation (fWBI). Characterized by progressive cognitive dysfunction, and associated cerebrovascular and white matter injury, RIBI deleteriously affects quality of life for cancer patients. Despite extensive morphological characterization of the injury, the pathogenesis is unclear, thus limiting the development of effective therapeutics. We previously reported that RIBI is associated with increased gene expression of the extracellular matrix (ECM) protein fibronectin (FN1). We hypothesized that fibronectin contributes to perivascular ECM, which may impair diffusion to the dependent parenchyma, thus contributing to the observed cognitive decline. The goal of this study was to determine the localization of fibronectin in RIBI and further characterize the composition of perivascular ECM, as well as identify the cell of origin for FN1 by in situ hybridization. Briefly, fibronectin localized to the vascular basement membrane of morphologically normal blood vessels from control comparators and animals receiving fWBI, and to the perivascular space of edematous and fibrotic vascular phenotypes of animals receiving fWBI. Additional mild diffuse parenchymal staining in areas of vascular injury suggested blood-brain-barrier disruption and plasma fibronectin extravasation. Perivascular ECM lacked amyloid and contained lesser amounts of collagens I and IV, which localized to the basement membrane. These changes occurred in the absence of alterations in microvascular area fraction or microvessel density. Fibronectin transcripts were rarely expressed in control comparators, and were most strongly induced within cerebrovascular endothelial and vascular smooth muscle cells after fWBI. Our results demonstrate that fibronectin is produced by cerebrovascular endothelial and smooth muscle cells in late-delayed RIBI and contributes to perivascular ECM, which we postulate may contribute to diffusion barrier formation. We propose that pathways that antagonize fibronectin deposition and matrix assembly or enhance degradation may serve as potential therapeutic targets in RIBI.

HtrA of Borrelia burgdorferi Leads to Decreased Swarm Motility and Decreased Production of Pyruvate.

ABSTRACTBorrelia burgdorferi HtrA (HtrABb) is a serine protease that targets damaged or improperly folded proteins. In our previous studies, HtrABb specifically degraded basic membrane protein BmpD, chemotaxis phosphatase CheX, and outer membrane protein P66. In addition, HtrABb degrades virulence factor BB0323 and components of the extracellular matrix fibronectin and aggrecan. A proteomics-based analysis (two-dimensional difference gel electrophoresis [2-D DIGE], liquid chromatography-mass spectrometry [LC-MS]) of an HtrABb-overexpressing strain of B. burgdorferi (A3HtrAOE) revealed that protein levels of P66 were reduced in comparison to wild-type B. burgdorferi, confirming its status as an HtrABb substrate. Hbb, a P66-DNA-binding transcription factor, was specifically degraded by HtrABb, providing supportive evidence for a role for both in the regulation of P66. A3HtrAOE exhibited reduced motility in swarm assays, a possible link between overabundance of HtrABb and its enzymatic specificity for P66. However, the ΔP66 strain did not have reduced motility in the swarm assays, negating a role for this protein. The proteomics analyses also identified three enzymes of the glycolytic pathway, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), glycerol-3-phosphate dehydrogenase (GPDH), and glycerol kinase (GK), and one enzyme involved in carbohydrate metabolism, diphosphate-fructose-6-phosphate 1-phosphotransferase, which were reduced in A3HtrAOE. Consistent with its reduced protein levels of these glycolytic enzymes, A3HtrAOE was also deficient in production of pyruvate. We propose a model for a role for HtrABb in contributing to a decrease in metabolic activity of B. burgdorferi.

Abstract 4500: BET proteins regulate hyaluronan synthases in pancreatic ductal adenocarcinoma

Abstract Background: Pancreatic ductal adenocarcinoma (PDAC) is associated with an extensive desmoplasia which is composed of multiple extracellular matrix components, including collagen, fibronectin, laminin, and hyaluronan (HA). Inhibitors targeting bromodomain and extra-terminal (BETi) proteins have emerged as potential therapeutic agents and are in clinical trials for a range of malignancies. We have previously shown that BETi attenuate fibrosis in vivo by decreasing collagen expression; however, the effect of BETi on HA has not been previously evaluated. Increased HA, which is synthesized by HA synthases (HAS), is associated with poor outcome in PDAC. Targeting HA has been postulated to provide a potential therapeutic opportunity to overcome PDAC chemo-resistance. Preclinical data have demonstrated that enzymatic degradation of HA with PEGPH20 remodels the tumor microenvironment, decreases the interstitial pressure and enhance the drug entry in tumors. Several ongoing clinical trials are evaluating PEGPH20 in combination with chemotherapies. We now report that BET inhibitors markedly decrease expression of HAS2 and HAS3, which are overexpressed in PDAC. Purpose: The aim of this study is to investigate the role of BET proteins in HA synthesis. Methods: mRNA expression levels HAS2 and HAS3 were determined in a panel of 7 PDAC cell lines by quantitative real-time RT-PCR. Protein expression was determined by western blotting. Results: We found that treatment with BET inhibitors decrease the expression of HAS2 and HAS3 in all cell lines. Furthermore, siRNA mediated knockdown of individual BET proteins demonstrated that HAS2 is primarily regulated by BRD2, while HAS3 is primarily regulated by BRD4. Conclusion: Our results demonstrate that BET proteins play a role in HA synthesis by regulating expression of HAS2 and HAS3 enzymes. Citation Format: Krishan Kumar, Kazumi Ebine, Thao Pham, Meng Shang, Hidayatullah G. Munshi. BET proteins regulate hyaluronan synthases in pancreatic ductal adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4500.

The Role of MicroRNA-181a in Myocardial Fibrosis Following Myocardial Infarction in a Rat Model.

BackgroundThe role of miR-181a in the development of cardiac disease and in particular, myocardial fibrosis following myocardial infarction (MI) remains unknown. The aim of this study was to explore the role of miR-181a in myocardial fibrosis in a rat model of MI and the expression of TGF-β receptor III (TβRIII).Material/MethodsForty adult male Wistar rats were randomly divided into an MI model group (n=30) and a control group with (n=10). The rat MI model involved ligating the left anterior descending (LAD) coronary artery in the model group; the control group was treated with a sham operation. Cardiac function was assessed using cardiac ultrasound. Myocardial fibroblasts were extracted from the rat hearts and transfected with a miR-mimic or miR-inhibitor, and cell growth was measured using an MTT assay. The level of miR-181a expression was detected using quantitative reverse transcription polymerase chain reaction (qRT-PCR) and Western blots.ResultsmiR-181a expression was significantly increased during the progression of MI (P<0.05). Over-expression of miR-181a was associated with increased deposition of extracellular matrix (ECM) components, collagen I and fibronectin. This effect was reversed with the use of a miR-181a inhibitor (P<0.05). Upregulation of miR-181a suppressed the expression of TGF-β receptor III (TβRIII) by binding with 3′-UTR.ConclusionsIn this rat model of MI, the findings were that miR-181a had a role in the progression of myocardial fibrosis. The findings require further studies to determine whether miR-181a might provide a novel therapeutic target to limit myocardial fibrosis following MI.

HiPIMS carbon coatings show covalent protein binding that imparts enhanced hemocompatibility

Magnetron sputtering is an established coating process rarely used for carbon films due to low deposition rates and poor adhesion. Substantial ion fluxes with tunable energies can be added by converting the process to high power impulse magnetron sputtering (HiPIMS) using a high voltage pulsed power supply. Here, we use a mixed mode (HiPIMS with transition to arc) process to deposit carbon coatings for applications in blood-contacting devices. Films produced at negative substrate bias in the range 0–350 V covalently bind protein molecules directly from buffer solution, making them biologically functionalisable, unlike coatings deposited with conventional magnetron sputtering. The HiPIMS coatings showed strikingly low thrombogenicity. A proof of principle application was demonstrated by deposition onto a stainless steel cardiovascular stent. Adhesion and toughness sufficient to withstand the extreme deformation, that accompanies surgical insertion, was achieved with negative bias in the range 100–350 V. Covalently immobilized, cell-adhesive extracellular matrix (ECM) proteins, tropoelastin and fibronectin, significantly increased the proliferation of endothelial cells on the HiPIMS coatings. Optimum proliferation was observed in the negative bias range 200–350 V. These results suggest that HiPIMS carbon coatings have great potential for biomedical devices where functionalization with active biomolecules can accelerate tissue integration.

Exploring the role of defective fibronectin matrix assembly in the VHL-associated CNS hemangioblastoma

Abstract Background: Central nervous system (CNS) hemangioblastoma (HB) is the most common tumor in the von Hippel Lindau (VHL) disorder, the hereditary tumor syndrome caused by the biallelic mutations of the VHL gene. The disrupted VHL and Elongin protein interaction on hypoxia-inducible factor-1α (HIF-1α) induces a set of hypoxia-inducible genes, resulting in an unchecked endothelial cell proliferation that then leads to hemangioblastoma formation. However, recent studies have shown that disruptive germline mutations of VHL need not result in hemangioblastoma, though it can cause other manifestations of the VHL syndrome. Similarly, sporadic hemangioblastoma can occur rarely without a somatic biallelic VHL mutation. The VHL protein was earlier found to be associated with the deposition of matrix fibronectin (FN) protein in the renal extracellular matrix. Methods: The present study was designed to investigate the deposition of the matrix FN protein in VHL-associated hemangioblastoma. Results: Seven HB tumor samples from the VHL syndrome had lower expressions of tissue FN compared to the control cerebellum samples or the control blood vessel sample. On comparing the VHL and FN protein expressions in a timed endothelial tube assay, the VHL protein expression was absent during the initial phase of tube formation but started expressing after 6 h. The levels of matrix form of FN gradually increased along with the VHL expression during the maturation of tube formation. Tube formation was found to be enhanced with extraneously added soluble FN and inhibited by matrix FN. Similarly, tube formation was inhibited by a modified tripeptide (RGD) inhibitor of integrin (-αVβ3), namely, Cyclo-Ala-Arg-Gly-Asp-3-aminomethylbenzoyl. Conclusions: Our study implicates that the extracellular deposition and matrix formation of FN is important for vascular endothelial proliferation, and that its absence has roles in the development of hemangioblastoma in the VHL syndrome.

Promotion of mammalian angiogenesis by neolignans derived from soybean extracellular fluids.

Excessive or insufficient angiogenesis is associated with major classes of chronic disease. Although less studied, small molecules which can promote angiogenesis are being sought as potential therapeutics for cardiovascular and peripheral arterial disease and stroke. Here we describe a bioassay-directed discovery approach utilising size exclusion and liquid chromatography to purify components of soybean xylem sap that have pro-angiogenic activity. Using high resolution accurate mass spectrometry and nuclear magnetic resonance spectroscopy, the structure of two pro-angiogenic molecules (FK1 and FK2) were identified as erythro-guaiacylglycerol-8-O-4'-(coniferyl alcohol) ether (eGGCE), and threo-guaiacylglycerol-8-O-4'-(coniferyl alcohol) ether (tGGCE). These two molecules, which are coniferyl neolignan stereoisomers, promoted in vitro angiogenesis in the μM to nM range. Independently sourced samples of eGGCE and tGGCE exhibited comparable pro-angiogenic activity to the soybean derived molecules. The cellular mode of action of these molecules was investigated by studying their effect on endothelial cell proliferation, migration, tube formation and adhesion to the extracellular matrix (ECM) components, fibronectin and vitronectin. They were found to enhance endothelial cell proliferation and endothelial cell tube formation on Matrigel, but did not affect endothelial cell migration or adhesion to fibronectin and vitronectin. Thus, this study has identified two coniferyl neolignan stereoisomers, eGGCE and tGGCE, as pro-angiogenic molecules, with eGGCE being less active than tGGCE.

P-41 - Myeloperoxidase-derived chlorination and oxidation human plasma fibronectin

Immune system cells are a major source of oxidants. Leukocyte activation generates O2•- and H2O2, and results in myeloperoxidase (MPO) release. MPO uses H2O2 and Cl- to generate the powerful oxidant HOCl. This mediates pathogen killing, but misplaced formation is linked with extracellular matrix damage (via MPO binding) and human disease. In this study, we have quantified chlorination (3-chloroTyr) and oxidation of human extracellular matrix fibronectin (FN) induced by HOCl and an enzymatic MPO system, and its consequences for human coronary artery smooth muscle cell adhesion, proliferation, migration and gene expression. 3-ChloroTyr and oxidation are detected at multiple sites on FN, including within functionally-important heparin-, cell- and collagen-binding domains, in a dose-dependent manner. Damage is localized to specific residues and occurs to markedly different extents. Heparin-binding and cell adhesion to HOCl-modified FN is decreased in a dose-dependent manner. Cell proliferation on HOCl-damaged FN is modulated, and migration attenuated. Expression of matrix proteins and matrix metalloproteinases in cells exposed to modified FN is significantly altered. These data indicate that FN modification by HOCl and MPO markedly affects matrix properties and cell behaviour.

Fibronectin EDA forms the chronic fibrotic scar after contusive spinal cord injury

Gliosis and fibrosis after spinal cord injury (SCI) lead to formation of a scar that is an impediment to axonal regeneration. Fibrotic scarring is characterized by the accumulation of fibronectin, collagen, and fibroblasts at the lesion site. The mechanisms regulating fibrotic scarring after SCI and its effects on axonal elongation and functional recovery are not well understood. In this study, we examined the effects of eliminating an isoform of fibronectin containing the Extra Domain A domain (FnEDA) on both fibrosis and on functional recovery after contusion SCI using male and female FnEDA-null mice. Eliminating FnEDA did not reduce the acute fibrotic response but markedly diminished chronic fibrotic scarring after SCI. Glial scarring was unchanged after SCI in FnEDA-null mice. We found that FnEDA was important for the long-term stability of the assembled fibronectin matrix during both the subacute and chronic phases of SCI. Motor functional recovery was significantly improved, and there were increased numbers of axons in the lesion site compared to wildtype mice, suggesting that the chronic fibrotic response is detrimental to recovery. Our data provide insight into the mechanisms of fibrosis after SCI and suggest that disruption of fibronectin matrix stability by targeting FnEDA represents a potential therapeutic strategy for promoting recovery after SCI.