Collagen type I modulates the platelet-derived growth factor (PDGF) regulation of the growth and expression of beta1 integrins by rat mesangial cells

Decellularized peripheral nerve grafts by a modified protocol for repair of rat sciatic nerve injury

Studies have shown that acellular nerve xenografts do not require immunosuppression and use of acellular nerve xenografts for repair of peripheral nerve injury is safe and effective. However, there is currently no widely accepted standard chemical decellularization method. The purpose of this study is to investigate the efficiency of bovine-derived nerves decellularized by the modified Hudson’s protocol in the repair of rat sciatic nerve injury. In the modified Hudson’s protocol, Triton X-200 was replaced by Triton X-100, and DNase and RNase were used to prepare accelular nerve xenografts. The efficiency of bovine-derived nerves decellularized by the modified Hudson’s protocol was tested in vitro by hematoxylin & eosin, Alcian blue, Masson’s trichrome, and Luxol fast blue staining, immunohistochemistry, and biochemical assays. The decellularization approach excluded cells, myelin, and axons of nerve xenografts, without affecting the organization of nerve xenografts. The decellularized nerve xenograft was used to bridge a 7 mm-long sciatic nerve defect to evaluate its efficiency in the repair of peripheral nerve injury. At 8 weeks after transplantation, sciatic function index in rats subjected to transplantation of acellular nerve xenograft was similar to that in rats undergoing transplantation of nerve allograft. Morphological analysis revealed that there were a large amount of regenerated myelinated axons in acellular nerve xenograft; the number of Schwann cells in the acellular nerve xenograft was similar to that in the nerve allograft. These findings suggest that acellular nerve xenografts prepared by the modified Hudson’s protocol can be used for repair of peripheral nerve injury. This study was approved by the Research Ethics Committee, Research and Technology Chancellor of Guilan University of Medical Sciences, Iran (approval No. IR.GUMS.REC.1395.332) on February 11, 2017.

Effects of a Matrix Metalloproteinase Inhibitor-Eluting Stent on In-Stent Restenosis

Background

The aim of this study was to compare changes in the extracellular matrix after implantation of a stent that elutes a matrix metalloproteinase (MMP) inhibitor (GM6001); and to determine the effects of the GM6001-eluting stent upon prevention of in-stent restenosis (ISR).

Material/Methods

We included 48 Guangxi Bama mini-pigs in this study. A GM6001-eluting stent was placed in one iliac artery and a stent that did not elute GM6001 was placed in the contralateral iliac artery. The iliac arteries were removed at 6 hours as well as 1, 7, 14, 56, 84, and 336 days after stent placement. Arteries were analyzed for morphometry, gelatinase content, different phenotypes of vascular smooth muscle cells (VSMCs), collagen content, apoptotic rate, and cell density.

Results

The vascular lumen areas of the GM6001 group were significantly increased and the neointimal areas were significantly reduced compared with the control group from the 7 days to the 336 days. In the 2 groups, expression of MMP-2 and MMP-9 peaked simultaneously, but GM6001-eluting stents inhibited expression of MMP-2 and MMP-9 in the vascular media and neointima (especially around the struts) significantly. In the GM6001 group, expression of tissue inhibitor of matrix metalloproteinase (TIMP)-1, TIMP-2, myosin heavy chain 10 (MYH-10, marker of the proliferative phenotype of VSMCs), collagen content, percentage of apoptotic cells, and cell density were also decreased significantly compared with those in the control group.

Conclusion

Use of GM6001-eluting stents resulted in persistent and potent inhibition of intimal hyperplasia, an increase in luminal area, and no obvious thrombosis in the arteries of the mini-pigs.

Review : The Role of Schwann cells in Neural Regeneration

The difference in regenerative capacity between the PNS and the CNS is not due to an intrinsic inability of central neurons to extend fibers. Rather, it is probably related to the environment in the CNS that is either repulsive to axonal outgrowth and/or nonsupportive of axonal elongation. In contrast, the PNS both supports and allows for axonal elongation after injury. The Schwann cell, which is the glial cell of the PNS, is strictly required for peripheral regeneration. Here we discuss recent work describing the biology of Schwann cell- dependent regeneration, discuss what is known of the molecular basis of this phenomenon, and how it might apply to the damaged CNS. NEUROSCIENTIST 5:208-216, 1999

Proteins mediating collagen biosynthesis and accumulation in arterial repair: novel targets for anti-restenosis therapy

Events contributing to restenosis after coronary interventions include platelet aggregation, inflammatory cell infiltration, growth factor release, and accumulation of smooth muscle cells (SMCs) and extracellular matrix (ECM). The ECM is composed of various collagen subtypes and proteoglycans and over time constitutes the major component of the mature restenotic plaque. The pathophysiology of collagen accumulation in the ECM during arterial restenosis is reviewed. Factors regulating collagen synthesis and degradation, including various cytokines and growth factors involved in the process, may be targets for therapies aimed at prevention of in-stent restenosis.

Growth of human embryonic stem cells using derivates of human fibroblasts

The majority of human embryonic stem cell (hESC) lines have been derived and grown using mouse or human feeder cells, or using Matrigel, an animal derivative rich in extracellular matrix (ECM) proteins. However, reliance on feeder layers and animal products limits the manipulation and clinical application of hESC. Alternatively, human fibroblasts produce an ECM which could be employed to coated plates and be easily sterilized. We have shown that hESC grown on this matrix and in the presence of medium conditioned by fibroblast cells maintain markers of pluripotency, including expression of cell surface proteins (SSEA3, SSEA4, TRA-1-60, TRA-1-81), alkaline phosphatase activity, and specific intracellular markers (NANOG, OCT, REX1). Moreover, hESC cultured on this novel human-derived ECM display a normal karyotype. This growth system reduces exposure of hESC to feeder layers and animal ingredients, thereby limiting the risk of pathogenic contamination and additionally facilitating manipulation of hESCs.

The bioactivity of transforming growth factor-beta1 can be regulated via binding to dermal collagens in mink lung epithelial cells

BACKGROUND

The bioactivity of transforming growth factor-beta1 (TGF-beta1) is known to be regulated by some components of the extracellular matrix (ECM), but the possibility that it might be regulated by collagen, the richest ECM component, has never been previously reported.

OBJECTIVE

This study was designed to investigate the possible role that different types of collagens might play on the bioactivity of TGF-beta1.

METHODS

The interaction of 125I-TGF-beta1 and various types of collagen was examined by a solid-phase assay and by a co-precipitation assay. The bioactivity of TGF-beta1 was assessed by a proliferation assay in which mink lung epithelial cells were examined in the presence and absence of collagens.

RESULTS

Activated native dimeric TGF-beta1 bound to type I collagen in a dose-dependent manner, while monomeric TGF-beta1 bound poorly to the collagen. Type III collagen, and type I gelatin, a heat-denatured type I collagen, also showed a similar interaction with TGF-beta1, however, type IV collagen showed a weak interaction. In the presence of types I and III collagens, the inhibitory effect of TGF-beta1 on the proliferation of mink lung epithelial cells was sustained, thus suggesting that the bioactivity of TGF-beta1 had been enhanced. Type I gelatin also enhanced the inhibition of cell growth, but its effect was weak in comparison with that of type I collagen. The amount of TGF-beta1 which remained intact in the conditioned medium after incubation with MLEC in the presence of types I and III collagens was more than that incubated without collagen.

CONCLUSIONS

Our results suggest that types I and III collagens, the two most abundant components of the interstitial collagens, can potentially bind to activated TGF-beta1 and regulate the bioactivity of this growth factor, thereby possibly maintaining the biologically available TGF-beta1 level.

Xenogeneic extracellular matrix as a scaffold for tissue reconstruction

Bioscaffolds derived from xenogeneic extracellular matrix (ECM) have been used in numerous tissue engineering applications. The safety and efficacy of such scaffolds when used for the repair and reconstruction of numerous body tissues including musculoskeletal, cardiovascular, urogenital and integumentary structures has been shown in both preclinical animal studies and in human clinical studies. More than 200,000 human patients have been implanted with xenogeneic ECM scaffolds. These ECM scaffolds are typically prepared from porcine organs such as small intestine or urinary bladder, which are subjected to decellularization and terminal sterilization without significant loss of the biologic effects of the ECM. The composition of these bioscaffolds includes the structural and functional proteins that are part of native mammalian extracellular matrix. The three-dimensional organization of these molecules distinguishes ECM scaffolds from synthetic scaffold materials and is associated with constructive tissue remodeling instead of scar tissue. The biologic response to these xenogeneic bioscaffolds, including the immune response, is discussed herein.

Low-molecular-weight peptides derived from extracellular matrix as chemoattractants for primary endothelial cells

The development of synthetic and naturally occurring scaffolds for tissue engineering applications has included strategies to promote attachment of specific cell types, control the rate of scaffold degradation, encourage angiogenesis, or otherwise modulate the host response. We have reported that bioscaffolds developed from porcine small intestinal submucosa (SIS) facilitate the constructive remodeling of tissues and recruit marrow-derived cells that persist long after the acute inflammatory stages have resolved. We have not yet determined which cells are recruited, the eventual fate of these cells, or via what mechanisms the events occur. We now have analyzed various molecular weight fractions of acid-hydrolyzed SIS by both functional and morphologic methods and have determined that fraction 4 (5 to 16 kDa) possesses chemoattractant activity for primary murine adult liver, heart, and kidney endothelial cells in vitro. Addition of fraction 4 to Matrigel plugs promoted in vivo vascularization when the plugs were implanted subcutaneously in mice. These results indicate that small-molecular-weight peptides derived from the degradation of porcine SIS are biologically active in the recruitment of murine endothelial cells in vitro and in vivo.

The role of very late antigen-1 in immune-mediated inflammation

The alpha1beta1 integrin, also known as "very late antigen" (VLA)-1, is normally expressed on mesenchymal cells, some epithelial cells, activated T cells, and macrophages, and interacts, via the I-domain of the extracellular domain of the alpha1 subunit, with collagen molecules in the extracellular matrix (ECM). By "outside-in" transmembranal signaling to the interior of the cell, it mediates adhesion, migration, proliferation, remodeling of the ECM, and cytokine secretion by endothelial cells, mesangial cells, fibroblasts, and immunocytes. Importantly, its expressions and functions are enhanced by inflammatory cytokines including interferon (IFN)gamma and tumor necrosis factor (TNF)alpha, thus augmenting angiogenesis and fibrosis linked, in particular, to inflammation. Moreover, within the immune system, VLA-1 marks effector memory CD4+ and CD8+ T cells that are retained in extralymphatic tissues by interactions of the integrin with collagen and produce high levels of IFNgamma. Thus, immune-mediated inflammation in vivo is inhibited by blockade of the VLA-1-collagen interaction in experimental animal models of arthritis, colitis, nephritis, and graft versus host disease (GVHD), suggesting that inhibiting the interaction of the alpha1 I-domain with its ligands or modulating "outside-in" signaling by VLA-1 would be a useful approach in the human diseases simulated by these experimental models.

beta1-Integrins mediate enhancement of airway smooth muscle proliferation by collagen and fibronectin

Airway smooth muscle (ASM) accumulation and enrichment of the extracellular matrix (ECM) with type I collagen and fibronectin are major pathologic features of airway remodeling in asthma. These ECM components confer enhanced ASM proliferation in vitro, but a requirement for specific integrin ECM receptors has not been examined. Here, we examined the mitogen platelet-derived growth factor (PDGF)-BB on beta1-integrin expression on human ASM cells cultured on these ECM substrates and defined the involvement of specific integrins in cell attachment and proliferation using integrin-neutralizing antibodies. PDGF-BB-dependent proliferation was enhanced two- to threefold by monomeric type I collagen or fibronectin and to a lesser extent by vitronectin; other interstitial ECM components (fibrillar type I and III collagen and tenascin-C) had no effect. Except for increased alpha3 expression induced by PDGF-BB and monomeric type I collagen or fibronectin, alpha1, alpha2, alpha4, alpha5, alphav, and alphavbeta3 integrins were unchanged compared with unstimulated cells on plastic. Blocking antibodies revealed alpha2beta1- and alphavbeta3-mediated attachment to monomeric type I collagen, whereas attachment to fibronectin required alpha5beta1. In contrast, enhancement of PDGF-BB-dependent proliferation by either monomeric type I collagen or fibronectin required alpha2beta1, alpha4beta1, and alpha5beta1 integrins. These data suggest multiple beta1-integrins regulate enhanced ASM proliferative responses.

Transforming growth factor-β1 stimulates collagen matrix remodeling through increased adhesive and contractive potential by human renal fibroblasts

Renal tubulointerstitial fibrosis is the common final pathway leading to end-stage renal failure. Tubulointerstitial fibrosis is characterized by fibroblast proliferation and excessive matrix accumulation. Transforming growth factor-beta1 (TGF-beta1) has been implicated in the development of renal fibrosis accompanied by alpha-smooth muscle actin (alpha-SMA) expression in renal fibroblasts. To investigate the molecular and cellular mechanisms involved in tubulointerstitial fibrosis, we examined the effect of TGF-beta1 on collagen type I (collagen) gel contraction, an in vitro model of scar collagen remodeling. TGF-beta1 enhanced collagen gel contraction by human renal fibroblasts in a dose- and time-dependent manner. Function-blocking anti-alpha1 or anti-alpha2 integrin subunit antibodies significantly suppressed TGF-beta1-stimulated collagen gel contraction. Scanning electron microscopy showed that TGF-beta1 enhanced the formation of the collagen fibrils by cell attachment to collagen via alpha1beta1 and alpha2beta1 integrins. Flow cytometry and cell adhesion analyses revealed that the stimulation of renal fibroblasts with TGF-beta1 enhanced cell adhesion to collagen via the increased expression of alpha1 and alpha2 integrin subunits within collagen gels. Fibroblast migration to collagen was not up-regulated by TGF-beta1. Furthermore, TGF-beta1 increased the expression of a putative contractile protein, alpha-SMA, by human renal fibroblasts in collagen gels. These results suggest that TGF-beta1 stimulates fibroblast-collagen matrix remodeling by increasing both integrin-mediated cell attachment to collagen and alpha-SMA expression, thereby contributing to pathological tubulointerstitial collagen matrix reorganization in renal fibrosis.

β1-integrins and glomerular injury

The renal glomerulus is composed of three types of glomerular cells (mesangial cell (MC), endothelial cell and podocyte) and extracellular matrix (ECM) consisting of the glomerular basement membrane (GBM) and mesangial matrix. It constitutes a highly specialized microcirculation in which the permeability characteristics of the capillary wall allow its unique filtration function. The proliferation of MCs, an increase of mesangial ECM and detachment podocyte from GBM are key biological features of progressive glomerulonephritis (GN), leading to glomerular scarring and dysfunction. Thus, the study of the molecular and cellular mechanisms responsible for pathological glomerular alterations may help to elucidate the pathogenesis of progressive glomerular diseases. A growing body of evidence indicates that beta1 integrin family (beta1 integrins), that mainly mediates cell adhesion to ECM, controls cell behaviors such as cell migration, proliferation, apoptosis and ECM assembly. In addition, a correlation between glomerular expression of beta1 integrins and their ligand ECM components is observed in various human and experimental GN, suggesting that altered beta1 integrins-mediated cell behaviors may contribute to the progression of GN. It is now becoming apparent that the expression of glomerular beta1 integrins is not only critical for maintaining the glomerular capillary permeability but it modulates cell signaling pathways regulating the cell phenotypes involved in the progression of glomerular diseases.

Collagen content and growth factor immunoexpression in uterine lower segment of type IA osteogenesis imperfecta: Relationship with recurrent uterine rupture in pregnancy

OBJECTIVE

The purpose of this study was to evaluate collagen content and platelet-derived growth factor, vascular endothelial growth factor, and connective tissue growth factor expression in the myometrium of the uterine lower segment from a patient with type IA osteogenesis imperfecta with recurrent uterine rupture and to evaluate the existence of a relationship between the rare recurrent uterine rupture and the tissue disorders of type IA osteogenesis imperfecta.

STUDY DESIGN

Collagen content and platelet-derived growth factor, vascular endothelial growth factor, and connective tissue growth factor expression in the uterine lower segment were assessed in the patient with type IA osteogenesis imperfecta and in eight otherwise healthy ("control") patients.

RESULTS

Type IA osteogenesis imperfecta contained less total collagen amount, with no difference in type III collagen expression and showed increased levels of platelet-derived growth factor and vascular endothelial growth factor in myometrial smooth muscle cells. No difference was observed in connective tissue growth factor expression.

CONCLUSION

These findings confirm the diminished collagen amount in myometrium from osteogenesis imperfecta and show the presence of additional pathogenetic mechanisms. A relationship is hypothesized between the underlying myometrial biochemical modifications and the recurrent uterine rupture.

Blocking of alpha 5 integrin stimulates production of TGF-beta and PAI-1 by human mesangial cells

Expression of integrin, which mediates cell-matrix interaction, is affected by several cytokines, in particular by transforming growth factor-beta (TGF-beta). However, it is unknown whether, in an opposite way, a specific integrin is involved in cytokine synthesis. We tested this hypothesis. Function-blocking anti-alpha 5 integrin (fibronectin receptor) antibody increased TGF-beta secretion in growth-arrested human mesangial cells (2.3-fold) compared with control IgG or anti-alpha v beta 3 integrin (receptor for several matrix proteins) antibody. It also increased the secretion of plasminogen activator inhibitor-1 (PAI-1), a protein associated with matrix increase, by 3.2-fold. The increase in PAI-1 secretion induced by anti-alpha 5 integrin antibody was not abrogated by anti-TGF-beta neutralizing antibody. These results indicate that function-blocking of anti-alpha 5 integrin stimulates TGF-beta as well as PAI-1 production, suggesting that alpha 5 integrin is involved in fibrotic process. Function-modulation of a specific integrin thus appears to play a role in glomerular remodeling.

The extracellular matrix as a scaffold for tissue reconstruction

The extracellular matrix (ECM) consists of a complex mixture of structural and functional proteins and serves an important role in tissue and organ morphogenesis, maintenance of cell and tissue structure and function, and in the host response to injury. Xenogeneic and allogeneic ECM has been used as a bioscaffold for the reconstruction of many different tissue types in both pre-clinical and human clinical studies. Common features of ECM-associated tissue remodeling include extensive angiogenesis, recruitment of circulating progenitor cells, rapid scaffold degradation and constructive remodeling of damaged or missing tissues. The ECM-induced remodeling response is a distinctly different phenomenon from that of scar tissue formation.

Requirement for tyrosine kinase-ERK1/2 signaling in alpha 1 beta 1 integrin-mediated collagen matrix remodeling by rat mesangial cells

Abnormal mesangial extracellular matrix remodeling by mesangial cells (MCs) is the hallmark of progressive glomerulonephritis (GN). We recently showed, using a type I collagen gel contraction assay, that alpha 1 beta 1 integrin-dependent MC adhesion and migration are necessary cell behaviors for collagen matrix remodeling. To further determine the mechanism of alpha 1 beta 1 integrin-mediated collagen remodeling, we studied the signaling pathways of MCs that participate in the regulation of collagen gel contraction. Immunoprecipitation and phosphotyrosine detection revealed that gel contraction is associated with the enhanced activity and phosphorylation of ERK1/2 by MCs. The tyrosine kinase inhibitors herbimycin and genistein inhibited collagen gel contraction dose dependently. Furthermore, targeting ERK1/2 activity with a MEK inhibitor, PD98059, and antisense ERK1/2 hindered gel contraction in a dose-dependent manner. Similar inhibitory effects on gel contraction and ERK1/2 phosphorylation were observed when MC-mediated gel contraction was performed in the presence of function-blocking anti-alpha1 or anti-beta1 integrin antibodies. However, cell adhesion and migration assays indicated that PD98059 and antisense ERK1/2 blocked alpha 1 beta 1 integrin-dependent MC migration, but did not interfere with collagen adhesion, although there was a marked decrease in ERK1/2 phosphorylation and ERK1/2 protein expression in cell adhesion on type I collagen. None of the above could affect membrane expression of alpha 1 beta 1 integrin. These results suggested that ERK1/2 activation is critical for the alpha 1 beta 1 integrin-dependent MC migration necessary for collagen matrix reorganization. We therefore conclude that ERK1/2 may serve as a possible target for pharmacological inhibition of pathological collagen matrix formation in GN.

Role of mast cell tryptase in renal interstitial fibrosis

Renal interstitial fibrosis is characterized by increased proliferation of fibroblasts and excessive accumulation of extracellular matrix. Mast cell tryptase has been implicated in the development of tissue fibrosis in skin and lungs. However, the significance of mast cell tryptase in human renal diseases has not been investigated. The potential role of mast cell-derived tryptase in the development of renal fibrosis was studied using immunohistochemical techniques and cultured human renal fibroblast cell lines. Semiquantitative immunostaining analysis of samples from 70 patients with several renal diseases, including IgA glomerulonephritis (GN) (n = 30), non-IgA GN (n = 5), membranous GN (n = 5), focal segmental glomerulosclerosis (n = 4), minor glomerular abnormalities (n = 5), lupus nephritis (n = 3), and acute or chronic tubulointerstitial nephritis (n = 18), revealed that the degree of renal interstitial fibrosis was well correlated with the number of infiltrating tryptase-positive mast cells (P < 0.01). Mast cells could not be detected in damaged glomeruli in any form of renal disease. [(3)H]Thymidine uptake experiments demonstrated that DNA synthesis by cultured renal fibroblasts was increased with the concentration of tryptase (0.5 to 5 nM) coincubated with heparin and was suppressed by coincubation with the protease inhibitors leupeptin and benzamidine hydrochloride. Tryptase alone also increased DNA synthesis by fibroblasts but exhibited less effectiveness, compared with the combination of tryptase and heparin. Conversely, heparin alone suppressed DNA synthesis by fibroblasts. Metabolic [(35)S]methionine-labeling experiments with cultured renal fibroblasts indicated that tryptase increased the synthesis of fibronectin and collagen type I, in a dose-dependent manner. These findings suggest that mast cell tryptase plays a role in the proliferation and extracellular matrix protein production of renal interstitial fibroblasts and thus contributes to the development of renal interstitial fibrosis.

Overexpression of alpha1beta1 integrin directly affects rat mesangial cell behavior

BACKGROUND

Glomerular mesangial cell (MC) proliferation, hypertrophy, and abnormal matrix remodeling characterized by increased expression of fibronectin, laminin and collagen type IV, and neoexpression of collagen I and III are the main biological features of progressive glomerulonephritis (GN). Especially, persistent pathological matrix remodeling may lead to glomerular scar formation (glomerular scarring). We reported recently that alpha1beta1 integrin, a major collagen receptor for MCs, may be a potential adhesion molecule for MC-mediated pathological collagen matrix remodeling in GN.

METHODS

To address further the direct role of alpha1beta1 integrin in MC behavior, such as cell growth and matrix remodeling, alpha1beta1 integrin was overexpressed in MCs by transfecting an expression vector containing a full-length rat alpha1 integrin cDNA. Flow cytometry and immunoprecipitation analysis were applied for selection of transfectants with a stable expression of the alpha1 integrin subunit. The effect of alpha1beta1 integrin overexpression on MC biology was examined with a 3H-thymidine incorporation assay, flow cytometric analysis of cell size and DNA content, Western blot analysis of a cyclin-dependent-kinase inhibitor, p27Kip1, alpha-smooth muscle actin expression, and a collagen gel contraction assay.

RESULTS

The alpha1 transfectants displayed a dramatic inhibition of 3H-thymidine incorporation as compared with the mock transfectants. Increased expression of the alpha1 subunit inversely correlated with cell cycle progression and paralleled the expression of p27Kip1 and alpha-smooth muscle actin, as well as the cell size in MCs. In addition, the alpha1-transfectants were able to enhance collagen matrix reorganization effectively.

CONCLUSION

These results indicate that MC-alpha1beta1 integrin expression is a critical determinant of MC phenotypes, including cell growth, cell size, and collagen matrix remodeling ability, and thereby contributes to scar matrix remodeling (sclerosis) in GN.