Deposition Of Vitronectin Research Articles

HIV Modulates Osteoblast Differentiation via Upregulation of RANKL and Vitronectin.

Bone loss is a prevalent characteristic among people with HIV (PWH). We focused on mesenchymal stem cells (MSCs) and osteoblasts, examining their susceptibility to different HIV strains (R5- and X4-tropic) and the subsequent effects on bone tissue homeostasis. Our findings suggest that MSCs and osteoblasts are susceptible to R5- and X4-tropic HIV but do not support productive HIV replication. HIV exposure during the osteoblast differentiation process revealed that the virus could not alter mineral and organic matrix deposition. However, the reduction in runt-related transcription factor 2 (RUNX2) transcription, the increase in the transcription of nuclear receptor activator ligand kappa B (RANKL), and the augmentation of vitronectin deposition strongly suggested that X4- and R5-HIV could affect bone homeostasis. This study highlights the HIV ability to alter MSCs' differentiation into osteoblasts, critical for maintaining bone and adipose tissue homeostasis and function.

Plasma vitronectin is reduced in patients with myasthenia gravis: Diagnostic and pathophysiological potential.

Myasthenia gravis (MG) is an autoimmune disease leading to varying degrees of skeletal muscle weakness. It is caused by specific antibodies directed against definite components in the postsynaptic membrane at the neuromuscular junction (NMJ), such as the acetylcholine receptor (AChR) and the muscle-specific kinase (MUSK) receptor. In clinical practice, MG patients may be classified into three main subgroups based on the occurrence of serum autoantibodies directed against AChR or MUSK receptor or antibody-negative. As the MG subgroups differ in terms of clinical characteristics, disease pathogenesis, prognosis, and response to therapies, they could benefit from targeted treatment as well as the detection of other possible disease biomarkers. We performed proteomics on plasma fractions enriched in low-abundance proteins to identify potential biomarkers according to different autoimmune responses. By this approach, we evidenced a significant reduction of vitronectin in MG patients compared to healthy controls, irrespective of the autoantibodies NMJ target. The obtained results were validated by mono- and two-dimensional Western blotting analysis. Vitronectin is a multifunctional glycoprotein involved in the regulation of several pathophysiological processes, including complement-dependent immune response, coagulation, fibrinolysis, pericellular proteolysis, cell attachment, and spreading. The pathophysiological significance of the reduction of plasma vitronectin in MG patients has yet to be fully elucidated. It could be related either to a possible deposition of vitronectin at NMJ to counteract the complement-mediated muscle damage at this level or to a parallel variation of this glycoprotein in the muscle extracellular matrix with secondary induced alteration in clustering of AChRs at NMJ, as it occurs with variation in concentrations of agrin, another extracellular matrix component. The clinical value of measuring plasma vitronectin has yet to be defined. According to present findings, significantly lower plasma values of this glycoprotein might be indicative of an impaired complement-dependent immune response.

Vitronectin deposition on bandage contact lenses: The influence of clinical condition

Purpose: There is a growing interest in the biomarkers involved in the inflammation and immunoregulation of the ocular environment in bandage contact lens (BCL) wear. One such candidate is vitronectin, a prominent inflammatory regulatory glycoprotein and adhesion molecule. Vitronectin deposition on the lens surface can influence plasmin upregulation. This work, as part of a wider study, compares vitronectin deposition on lenses worn for the treatment of two different chronic ocular conditions; Sjogren's syndrome (SS) and bullous keratopathy (BK).

Fibronectin- and vitronectin-induced microglial activation and matrix metalloproteinase-9 expression is mediated by integrins alpha5beta1 and alphavbeta5.

Early in the pathogenesis of multiple sclerosis, the blood-brain barrier is compromised, which leads to deposition of the plasma proteins fibronectin and vitronectin in cerebral parenchyma. In light of our previous finding that microglial activation in vitro is strongly promoted by fibronectin and vitronectin, we set out to examine the possibility that modulation of microglial activation by fibronectin or vitronectin is an important regulatory mechanism in vivo. In an experimental autoimmune encephalomyelitis mouse model of demyelination, total brain levels of fibronectin and vitronectin were strongly increased and there was a close relationship between fibronectin and vitronectin deposition, microglial activation, and microglial expression of matrix metalloproteinase-9. In murine cell culture, flow cytometry for MHC class I and gelatin zymography revealed that microglial activation and expression of pro-matrix metalloproteinase-9 were significantly increased by fibronectin and vitronectin. Function-blocking studies showed that the influence of fibronectin and vitronectin was mediated by the alpha(5)beta(1) and alpha(v)beta(5) integrins, respectively. Taken together, this work suggests that fibronectin and vitronectin deposition during demyelinating disease is an important influence on microglial activation state. Furthermore, it provides the first evidence that the alpha(5)beta(1) and alpha(v)beta(5) integrins are important mediators of microglial activation.

Changes in Matrix Composition during the Growth and Regression of Human Hemangiomas

Background.Hemangiomas offer an uncommon opportunity to study rapid vessel growth and spontaneous regression of a vascular human tumor. In contrast, venous malformations are another type of vascular tumor that grows slowly without spontaneous involution. Extracellular matrix (ECM) molecules modulate the responsiveness of endothelial cells to mitogenic stimuli such as basic fibroblast growth factor (bFGF), a well-recognized stimulant of angiogenesis. In this study we hypothesized that in hemangiomas, sites of angiogenesis may have a different ECM composition than sites of vascular regression.Materials and methods.Using immunohistochemistry, we analyzed proliferating hemangiomas, regressing hemangiomas, venous malformations, and normal skin for the basement membrane ECM molecules collagen IV and laminin and plasma-borne ECM molecules fibronectin and vitronectin. We used metabolic labeling to determine whether primary human dermal microvascular endothelial cells regulated FGFR-1 or FGFR-2 when grown on these different matrices.Results.We found that proliferating hemangiomas showed extensive deposition of vitronectin in the subendothelial space. In contrast, regressing hemangiomas or venous malformations did not show vitronectin deposition. Venous malformations, which are composed of ectatic lakes of venous channels, also lacked laminin in their basement membranes. We also found that cultured microvascular endothelial cells grown on vitronectin increased synthesis of FGFR-1 and FGFR-2 protein.Conclusions.Changes in the ECM environment occur in conjunction with the angiogenic state of a vascular human tumor. Furthermore, changes in the ECM environment alone can directly regulate synthesis of angiogenic growth factor receptors.

Localization of urokinase to focal adhesions by human fibrosarcoma cells synthesizing recombinant vitronectin.

Cell surface plasminogen activators have been proposed to participate in cell migration and invasion by activating both intracellular signaling pathways and extracellular proteolysis. Urokinase-type plasminogen activator (uPA) is secreted from many cell types and localizes to focal contact areas when cells are seeded onto the plasma protein vitronectin. Induction of vitronectin synthesis during migration of neural crest cells and growth of certain tumors suggests that the de novo synthesis and deposition of vitronectin into the tissue matrix may remodel the matrix to provide an environment suitable for cell migration and (or) tumor invasion. To investigate the effects of vitronectin secretion and matrix deposition on the localization and activity of cell-associated uPA, HT-1080 fibrosarcoma cells were transfected with the Rc/CMV expression vector containing a vitronectin cDNA insert and stable cell lines expressing vitronectin were selected. Vitronectin-secreting cells were allowed to attach and spread on collagen- and fibronectin-coated substrates. Within 6 h, vitronectin was detected on the substrate; vitronectin synthesis was accompanied by the clustering of both the alpha v beta 5 vitronectin receptor and uPA into vinculin-containing focal adhesions. Although mock transfected cells formed small focal adhesions on both collagen and fibronectin, no co-localization of uPA or alpha v beta 5 to focal adhesions was evident in these cells. Vitronectin-secreting cells also exhibited decreased levels of plasminogen activation and increased levels of cell adhesion as compared with the mock transfected cells. These data demonstrate that the synthesis of vitronectin and its matrix association by transfected HT-1080 fibrosarcoma cells results in localization of uPA to alpha v beta 5 containing focal adhesions, decreased cell surface uPA activity, and an increase in cell adhesion.

Vitronectin in Colorectal Adenocarcinoma—Synthesis by Stromal Cells in Culture

We have investigated the expression and cellular source of vitronectin in colorectal adenocarcinoma. Immunofluorescence staining of tissue sections revealed the presence of vitronectin in the stroma of the 11 tumors studied, but not in adjacent normal colon. A method was devised for the isolation from colorectal adenocarcinomas of fibroblast-like cells that stained positive for vimentin but negative for cytokeratin. These tumor-derived stromal cells synthesized and secreted vitronectin, as revealed by metabolic labeling and immunoprecipitation. This was confirmed by Southern blot analysis of polymerase chain reaction amplification products from reverse-transcribed RNA. Normal skin fibroblasts did not synthesize vitronectin. Immunofluorescence staining showed vitronectin deposited at focal contact sites in the tumor-derived cells, where it colocalized with vinculin and the αv integrin subunit. The deposition of vitronectin into focal contact sites was not dependent on the presence of serum. The finding that vitronectin can be synthesized and secreted by tumor-derived fibroblast-like cells in culture indicates that vitronectin expression can be promoted by as yet unknown signals provided in disease states, such as cancer.

An immunohistochemical study of extracellular matrix components and integrins in human glomerular diseases.

The localization of extracellular matrix components and their cell surface receptors (integrins) was studied in 130 subjects in order to clarify their participation in the progression and aggravation of various types of nephritis. Included in the study were 2 normal subjects, 14 patients with minimal change disease, 2 patients with minimal change nephrotic syndrome, 65 patients with IgA nephropathy, 18 patients with mesangial proliferative glomerulonephritis, 15 patients with membranous glomerulonephritis, 5 patients with membranoproliferative glomerulonephritis and 9 patients with systemic lupus erythematosus (SLE). The distribution of fibronectin (FN), vitronectin (VN), laminin (LN), heparan sulfate proteoglycan (HSPG), type III, IV, V, VI collagen, fibronectin receptor (FNR) and vitronectin receptor (VNR) in the glomerulus was studied employing the indirect immunoperoxidase method. FN, LN, type IV, V and VI collagen, FNR and VNR were found to be distributed in the expanded mesangial region in IgA nephropathy, mesangial proliferative glomerulonephritis and membranoproliferative glomerulonephritis. Deposition of VN was observed in some of the patients. In membranous glomerulonephritis and membranoproliferative glomerulonephritis, the distribution of FN, LN, type IV collagen, FNR and VNR was increased in the thickened loop wall and VN deposition was also observed. Quantitative and functional changes in the extracellular matrix and integrins, therefore, appear to participate in the progression and aggravation of glomerulonephritis.

Enhancement of vitronectin expression in human HepG2 hepatoma cells by transforming growth factor‐β1

Liver cells are considered the principal source of plasma vitronectin. The human hepatoma cell line HepG2 produces vitronectin into its culture medium. In the current work we have analyzed the regulation of vitronectin by transforming growth factor-beta 1 (TGF beta 1) in this hepatoma cell line by Northern hybridization, polypeptide and immunoprecipitation analyses and compared the response to another TGF beta-regulated gene, plasminogen activator inhibitor (PAI-1). Rabbit antibodies raised against human plasma-derived vitronectin were used in immunodetection. Polypeptide and immunoprecipitation analyses of the medium and cells, as well as immunoblotting analysis of the cells and their extracellular matrices, indicated enhanced TGF beta 1-induced production and extracellular deposition of vitronectin. Accordingly, TGF beta 1 enhanced the expression of vitronectin mRNA at picomolar concentrations (2-20 ng/ml) as shown by Northern hybridization analysis. Comparison of the temporal TGF beta induction profiles of vitronectin and PAI-1 mRNAs showed that vitronectin was induced more slowly but the vitronectin mRNAs persisted longer. In addition, platelet-derived and epidermal growth factors had an effect on vitronectin expression, but it was of lower magnitude. TGF beta 1 enhanced the expression of PAI-1 but, unlike previous reports, epidermal growth factor did not have any notable effect on PAI-1 in these cells. The results indicate that TGF beta 1 is an efficient regulator of the production of vitronectin by HepG2 cells and that PAI-1 and vitronectin are not coordinately regulated. In addition, with affinity purified antibodies to vitronectin receptor, we observed strong enhancement of the alpha subunit of the receptor in response to TGF beta 1. These effects of TGF beta are probably involved in various processes of the liver where matrix induction and controlled pericellular proteolysis is needed, as in tissue repair.

Deposition of C3, C9 neoantigen and vitronectin (S-protein of complement) in lichen planus pemphigoides

We have compared the distribution of C3, C9 neoantigen (C9n) and vitronectin at the dermoepidermal junction in lichen planus pemphigoides with that in bullous pemphigoid. Eight out of 30 biopsies from patients with lichenoid lesions had linear C3 deposition at the basement membrane zone (BMZ); four of these patients had bullae and fulfilled the criteria for lichen planus pemphigoides. C9n immunoreactivity was detected as a linear or an intermittent linear/granular band at the BMZ only in these four patients, suggesting a role for the membrane attack complex of complement (MAC) in the pathogenesis of blister formation in lichen planus pemphigoides. Faint linear deposition of vitronectin, in addition to C9n, at the BMZ was seen in two of the four cases of lichen planus pemphigoides and three of six cases of bullous pemphigoid. This suggests that vitronectin may be deposited in association with C9n not only as part of the non-lytic SC5b-9 complex, but also as a regulatory step following the lytic action of MAC. A regulatory function for vitronectin in limiting tissue damage following activation of MAC is supported by our finding of a heavy deposition of vitronectin in association with C9n in a lichen planus pemphigoides patient in whom bulla formation had ceased.

Vitronectin colocalizes with Ig deposits and C9 neoantigen in discoid lupus erythematosus and dermatitis herpetiformis, but not in bullous pemphigoid

C9 neoantigen immunoreactivity has been found to colocalize with C3 immunoreactivity at the dermal-epidermal junction zone (DEZ) in skin specimens from patients with bullous pemphigoid, lupus erythematosus and dermatitis herpetiformis. The present study was designed to elucidate whether the C9 neoantigen immunoreactivity represents deposition of membrane attack complexes or non-lytic SC5b-9 complexes. Skin specimens from 11 patients with pemphigoid, five patients with discoid lupus erythematosus and from nine patients with dermatitis herpetiformis were studied with immunofluorescence using both monoclonal and polyclonal antibodies against C9 neoantigen and against vitronectin (S-protein), an inhibitor to the membrane attack complex of complement. Specimens from the pemphigoid patients demonstrated C9 neoantigen reactivity along the DEZ without detectable colocalized vitronectin. This suggests deposition of membrane attack complexes in the pemphigoid lesions. Immunoreactivity of both C9 neoantigen and vitronectin was detected in the DEZ in specimens of discoid lupus erythematosus and in the tips of dermal papillae in specimens of dermatitis herpetiformis. The combined presence of C9 neoantigen- and vitronectin immunoreactivity may indicate deposition of C9 as part of the non-lytic SC5b-9 complex. The finding reported here of differential deposition of vitronectin and C9 in different diseases indicates that the presence of C9 neoantigen immunoreactivity in tissue per se does not represent the deposition of membrane attack complexes, but that it may also be C9 deposited as part of the nonlytic SC5b-9 complex.

Immunohistochemical demonstration of age-related deposition of vitronectin (S-protein of complement) and terminal complement complex on dermal elastic fibers

Immunoreactivity of vitronectin was investigated in 100 skin specimens from different body regions in 87 individuals of different ages using monoclonal and polyclonal anti-vitronectin antibodies in an avidin-biotin-peroxidase complex technique. Vitronectin immunoreactivity was found in conjunction with dermal elastic fibers in all subjects older than 13 years. No vitronectin immunostaining was detected in subjects younger than six years, suggesting deposition of vitronectin during late childhood or early adolesence. Using an immunogold staining procedure, vitronectin immunoreactivity was ultrastructurally localized to the periphery of elastic fibers. The blood level of vitronectin in 20 healthy newborns was 67% of the adult level, suggesting active biosynthesis already in the fetus. To investigate whether vitronectin is deposited as part of the SC5b-9 complex or as uncomplexed protein, the immunoreactivity of vitronectin was compared with that of C9, using monoclonal and polyclonal antibodies against the C9 neoantigen. Distinct C9 neoantigen immunoreactivity was demonstrated in association with dermal elastic fibers in human skin in adults but only in subjects older than 30 years. The intensity of C9 neoantigen immunoreactivity appeared to increase with age and was found to be stronger in sun-exposed skin than in sun-protected skin. These findings indicate that uncomplexed vitronectin is deposited during childhood or early adolescence and that terminal complement complexes (C5b-9 and/or SC5b-9) are deposited on elastic fibers later on in life. Hypothetically, the tissue form of vitronectin may be involved in the prevention of tissue damage in proximity to local complement activation. In addition, it may be physiologically important as substratum for cells, stimulating cell migration and anchorage.

Immunohistochemical Demonstration of Age-related Deposition of Vitronectin (S-protein of Complement) and Terminal Complement Complex on Dermal Elastic Fibers.

Immunoreactivity of vitronectin was investigated in 100 skin specimens from different body regions in 87 individuals of different ages using monoclonal and polyclonal anti-vitronectin antibodies in an avidin-biotin-peroxidase complex technique. Vitronectin immunoreactivity was found in conjunction with dermal elastic fibers in all subjects older than 13 years. No vitronectin immunostaining was detected in subjects younger than six years, suggesting deposition of vitronectin during late childhood or early adolescence. Using an immunogold staining procedure, vitronectin immunoreactivity was ultrastructurally localized to the periphery of elastic fibers. The blood level of vitronectin in 20 healthy newborns was 67% of the adult level, suggesting active biosynthesis already in the fetus. To investigate whether vitronectin is deposited as part of the SC5b-9 complex or as uncomplexed protein, the immunoreactivity of vitronectin was compared with that of C9, using monoclonal and polyclonal antibodies against the C9 neoantigen. Distinct C9 neoantigen immunoreactivity was demonstrated in association with dermal elastic fibers in human skin in adults but only in subjects older than 30 years. The intensity of C9 neoantigen immunoreactivity appeared to increase with age and was found to be stronger in sun-exposed skin than in sun-protected skin. These findings indicate that uncomplexed vitronectin is deposited during childhood or early adolescence and that terminal complement complexes (C5b-9 and/or SC5b-9) are deposited on elastic fibers later on in life. Hypothetically, the tissue form of vitronectin may be involved in the prevention of tissue damage in proximity to local complement activation. In addition, it may be physiologically important as substratum for cells, stimulating cell migration and anchorage.