Integrating multiple microarray datasets on oral squamous cell carcinoma to reveal dysregulated networks.

BACKGROUND: Oral squamous cell carcinoma (OSCC) is the sixth most common type of carcinoma worldwide. The pathogenic pathways involved in this cancer are mostly unknown; therefore, a better characterization of the OSCC gene expression profile would represent a considerable advance. The public availability of gene expression datasets was meant to obtain new insights on biological processes. METHODS: We integrated 4 public microarray datasets on OSCC to evaluate the degree of consistency among the biological results obtained in these different studies and to identify common regulatory pathways that could be responsible for tumor growth. RESULTS: Twelve altered cellular pathways implicated in OSCC and 4 genes altered in the extracellular matrix (ECM) receptor pathway were validated by quantitative real-time polymerase chain reaction (qRT-PCR). CONCLUSION: Using 4 expression array datasets, we have developed a robust method for analyzing pathways altered in OSCC.

Cell-matrix interactions in aging: role of receptors and matricryptins.

Extracellular matrix (ECM) has been a central topic in aging research for several years. Cell-matrix interactions extend the interest in this topic both for normal tissue homeostatic regulation as well as for its dysregulation in age-related diseases. A relatively new extension of this ever-increasing field of aging research concerns the recognition of the original biological activities exhibited by proteolytic fragments of matrix macromolecules. A number of such matricryptins were recently identified, some of them endowed with harmful effects for tissue function. Some of the breakdown products exert a positive feedback effect by upregulating the biosynthesis of the original macromolecule synthesis and/or the expression of degrading enzymes. This results in vicious circles which might well be involved in tissue aging. The examples detailed in this review concern fibronectin (FN) and elastin. A number of fibronectin fragments (Fn-fr) were shown to exhibit diverse activities including increasing tissue degradation, inflammation and tumor progression. Elastin degradation products acting as agonists on the elastin-laminin receptor can trigger harmful effects such as up-regulation of proteases and free radical production. Both macromolecules are at the center of autoamplifying vicious circles of potential importance for age-dependent modification of tissue function.

Glow discharge plasma treatment of titanium plates enhances adhesion of osteoblast-like cells to the plates through the integrin-mediated mechanism.

PURPOSE: Initial adhesion of cells to implant surfaces and subsequent behavior of the cells are important determinants for biocompatibility of the implants. It was previously reported that both adhesion of MC3T3-E1 osteoblast-ike cells to titanium (Ti) plates and their differentiation into more mature cells on the plates were stimulated by treatment of the plates with glow discharge plasma (GDP). However, the mechanisms of these processes have not yet been identified. In this study, the adhesion and differentiation mechanism of osteoblast-like cells to Ti with and without GDP were investigated. MATERIALS AND METHODS: The adhesion and differentiation mechanism of MC3T3-E1 osteoblast-like cells to Ti, with and without GDP, were investigated by cultivation in serum-free medium and use of a competitive inhibition test to examine the influence of extracellular matrix proteins contained in the serum and to identify cell binding proteins. In addition, the amount of fibronectin adsorption on each Ti plate was investigated by enzyme-linked immunosorbent assay and fluorescein isothiocyanate labeling. Furthermore, the stress fiber formation and morphology of cells on each plate were evaluated microscopically. RESULTS: Adherent cells on Ti plates, with and without GDP, were significantly reduced in serum-free conditions and the presence of RGDS (Arg-Gly-Asp-Ser) peptides. Fibronectin adsorption on titanium plates was increased by GDP. Furthermore, stress fiber formation of cells was extremely progressive on the Ti plates treated with GDP and was not observed on the cells inhibited by RGDS peptide. DISCUSSION: These results suggest that RGDS containing serum proteins have a major role in regulating specific adhesion of cells to Ti, and GDP promoted cell adhesion and differentiation on Ti by increasing the adsorption of proteins. CONCLUSION: According to this study, the adhesion and differentiation mechanism of osteoblast-like cells to Ti, with and without GDP, can be obtained.

Integrin cell adhesion receptors and the concept of agonism.

Most cells are adherent and rely on adhesive interactions to regulate their shape, motility and growth. These interactions are critical for tissue integrity and homeostasis but they also contribute to many of the most common diseases in humans. The integrins are a key family of cell-surface receptors that mediate the downstream consequences of cell adhesion and are therefore prime targets for the development of therapeutic agents. In addition to their adhesive activity, integrins also exhibit several other classical features of signalling receptors. Sufficient evidence is now available to pose the question of whether integrins should be classified as true signalling receptors; this article both reviews this evidence and attempts to identify remaining gaps.

Moléculas de adhesión y su importancia en odontología: revisión de la literatura / Adhesion molecules and its importance in dentistry

En la actualidad se reconoce que las interacciones que se suceden entre las células entre sí y de éstas con los componentes de la matriz extracelular se producen por la intervención de las Moléculas de Adhesión. Las Moléculas de adhesión son glucoproteínas distribuidas en gran cantidad de células que le permiten al organismo realizar funciones tanto fisiológicas, como la adhesión entre las células epiteliales, como fisiopatológicas, por ejemplo la inflamación. Es por ello que se hace imperativo conocer estas familias, para así entender los procesos que se desarrollan en las diversas actividades, normales o patológicas, de la cavidad bucal

Adhesive interactions in peri-implantation morphogenesis and placentation.

Antibody perturbation and gene knockout studies show that adhesion receptor modulation plays a critical role in peri-implantation mouse embryo and human cytotrophoblast differentiation. Deletion of beta 1 integrins leads to cell death in the inner cell mass of mouse embryos shortly after implantation in vivo or blastocyst outgrowth in vitro. In F9 embryonal carcinoma cells, deleting beta 1 also affects migration of parietal endoderm even on substrates for which the mutant cells express alternative receptors. Human cytotrophoblasts switch their integrin repertoire as they differentiate and invade the uterine interstitium and vasculature. Interestingly, cytotrophoblasts also transform their cell-cell adhesion molecule phenotype, expressing additional cadherins and immunoglobulin family members as they differentiate. Many of these modulations in adhesion phenotype are initiated early in the pre- and/or peri-implantation periods in human and mouse embryos. Therefore, they constitute important markers of normal progression for evaluating effects of environmental stress and for testing the hypothesis that abnormal switching of adhesion molecules characterizes a significant proportion of conceptuses that fail early in development.

Glioma invasion in the central nervous system.

Invading glioma cells seem to follow distinct anatomic structures within the central nervous system. Tumor cell dissemination may occur along structures, such as the basement membranes of blood vessels or the glial limitans externa, that contain extracellular matrix (ECM) proteins. Frequently, invasive glioma cells are also found to migrate along myelinated fiber tracts of white matter. This behavior is most likely a consequence of using constitutive extracellular ligands expressed along the pathways of preferred dissemination. The extracellular space in anatomic structures, such as blood vessel basement membranes or between myelinated axons, is profoundly different, thus suggesting that glioma cells may be able to use a multiplicity of matrix ligands, possibly activating separate mechanisms for invasion. In addition, enzymatic modification of the extracellular space or deposition of ECM by the tumor cells may also create a more permissive environment for tumor spread into the adjacent brain. Tumor cell invasion is defined as translocation of neoplastic cells through host cellular and ECM barriers. This process has been studied in other cancers, in which a cascade of events has been described that involves receptor-mediated matrix adhesion, degradation of matrix by tumor-secreted metalloproteinases, and, subsequently, active cell locomotion into the newly created space. Although some of these mechanisms may play an important role in glioma invasion, there are some significant differences that are mainly the result of the profoundly different composition of the extracellular environment within the brain. This review focuses on the composition of central nervous system ECM and the recent evidence for the use by glioma cells of multiple invasion mechanisms in response to this unique environment.

Uremic patients have decreased shear-induced platelet aggregation mediated by decreased availability of glycoprotein IIb-IIIa receptors.

Bleeding and platelet dysfunction are prominent features of uremia. Sh ear-induced platelet aggregation (SIPA) involves the interaction of von Willebrand factor (vWF) with platelet membrane glycoproteins (GP) Ib and IIb-IIIa, the same receptor-ligand pair involved in in vivo adhesion and aggregation of platelets in the arterial circulation. We have used a modified rotational cone-plate viscometer to measure SIPA and calcium flux in platelets. Flow cytometric analysis of the surface expression of GP Ib and IIb-IIIa was performed using flourescein isothiocyanate-conjugated monoclonal antibodies CD42b and CD41a, respectively. Uremic patients showed decreased SIPA (controls, 43% +/- 2% [mean +/- SEM]; chronic renal failure patients, 36% +/- 3%; chronic hemodialysis patients, 26% +/- 2%; P < 0.001) along with a decrease in GP IIb-IIIa (controls, chronic renal failure patients, and chronic hemodialysis patients, 840 +/- 25, 649 +/- 42, 661 +/- 38 mean flourescence intensity, respectively; P < 0.0001). Glycoprotein Ib in uremic patients was not significantly different from normal. Chronic hemodialysis patients also demonstrated increased platelet-bound fibrinogen (P < 0.001) and platelet-bound vWF (p < 0.01). Calcium flux and thromboxane B(2) generation during SIPA of uremic platelets was normal. However, uremic plasma showed twice the normal concentration of vWF (P < 0.001) and sodium dodecyl sulfate agarose gel electrophoresis revealed the presence of fibrinogen fragments. Mixing experiments demonstrated an inhibitory effect of uremic plasma on SIPA of normal platelets (decreased from 39% +/- 3% at baseline to 31% +/- 3% after incubation in uremic plasma) along with an activation-independent increase in platelet-bound fibrinogen and platelet-bound vWF. When uremic platelets were incubated in normal plasma, their SIPA increased from 12% +/- 5% at baseline to 18% +/- 4% after incubation in normal plasma; (P = 0.002), although it did not return to normal. These results suggest that the uremic platelet dysfunction results from decreased GP IIb-IIa availability due to receptor occupancy by fibrinogen fragments (and possibly vWF fragments).

Loss of the tumorigenic phenotype with in vitro, but not in vivo, passaging of a novel series of human bronchial epithelial cell lines: possible role of an alpha 5/beta 1-integrin-fibronectin interaction.

We established an immortalized, nontumorigenic human bronchial epithelial cell line by transfection with the origin of replication-defective SV40 large T plasmid. This line spontaneously became tumorigenic at passage 184 (NL20T), although subsequent passages (passages 189, 200, and 205) failed to form tumors. The tumorigenic cell line NL20T was reinoculated back into athymic nude mice, and the two subsequently derived cell lines (NL20T-A and NL20T-B) have been passaged 85 times in vitro and remain tumorigenic. However, late-passage NL20T cells consistently lose their tumorigenicity when passaged in vitro on tissue culture plastic dishes (NL20T-n cells). Thus, two of the cell lines, NL20 and NL20T, reverted to the nontumorigenic phenotype reproducibly and spontaneously following serial passage on plastic tissue culture plates, whereas cells passaged in mice (NL20T-A and -B) did not. We used these nontumorigenic (NL20 and NL20T-n) and tumorigenic (early passage NL20T, NL20T-A, and NL20T-B) cells to study the role of the alpha 5/beta 1-integrin and attachment to fibronectin in tumorigenicity. The two nontumorigenic cell lines (NL20 and NL20T-n) attached slower to fibronectin-coated plates than the two tumorigenic cell lines in a cellular-extracellular matrix adhesion assay. Attachment was abrogated by exposure to a blocking antibody to the alpha 5/beta 1-integrin, the fibronectin receptor, in the two tumorigenic cell lines. Cell surface expression of the alpha 5/beta 1 cell surface protein by flow cytometry was highest in the tumorigenic NL20T and NL20T-A cells. NL20T-A cells were cultured with an antibody to alpha 5/beta 1 and inoculated s.c. into athymic nude mice; tumorigenicity of the NL20T-A cells was inhibited in a dose-dependent manner. Tumorigenicity was also inhibited partially with monoclonal antibodies to either alpha 5 or beta 1. A mixture of 10% tumorigenic NL20T-A cells and 90% nontumorigenic NL20 cells was cultured on plastic, type IV collagen, laminin, and fibronectin for 9 weeks. Only cells cultured on fibronectin formed tumors when inoculated s.c. into athymic nude mice. We conclude that these data are consistent with the hypothesis that neoplastic transformation in our original cell line arose from in vivo selection of a small mutant clone, which had arisen in culture and was selected subsequently in vivo but was lost with in vitro culture in NL20 cells, and that alpha 5/beta 1-integrin interaction with the extracellular matrix may play a role in tumorigenicity in our system.

Beta 3 integrin-mediated fibrin clot retraction by nucleated cells: differing behavior of alpha IIb beta 3 and alpha v beta 3.

Fibrin clot retraction may be important in resolution of thrombi and, in platelets, is mediated by integrin alpha IIb beta 3 (GPIIb-IIIa). Nucleated cells that lack alpha IIb beta 3 can retract fibrin clots, and we now report that integrin alpha v beta 3 can support this process. In addition, we compared the capacities of recombinant beta 3 integrins to mediate clot retraction in Chinese hamster ovary and M21 melanoma cells. We found that alpha v beta 3, but not alpha IIb beta 3, could spontaneously support retraction. Transferring the cytoplasmic domain of alpha v to alpha IIb enabled the resulting chimeric alpha IIb beta 3 to support clot retraction. The capacity of the alpha v cytoplasmic domain to support clot retraction was not caused by activation of the ligand binding function of alpha IIb beta 3 or by enhancement of alpha IIb beta 3's capacity to stimulate the formation of focal adhesions or the tyrosine phosphorylation of pp125FAK. These experiments define requirements for alpha IIb beta 3-mediating clot retraction, establish the capacity of alpha v beta 3 to mediate this process, and suggest differing functional roles of the alpha v and alpha IIb cytoplasmic domains.

Platelet phospholipase D is activated by protein kinase C via an integrin alpha IIb beta 3-independent mechanism.

Blood platelets contain phospholipase D (PLD) that is rapidly activated following platelet stimulation. It is currently unclear, however, where PLD fits into the signalling cascade that leads to aggregation and secretion. Therefore we investigated the mechanism of activation of PLD in human platelets, using the formation of the PLD-specific product phosphatidylethanol as a measure of PLD activity. PLD was activated by a number of platelet agonists that also cause the activation of protein kinase C, including thrombin, collagen, the Ca2+ ionophore A23187 and the thromboxane A2-mimetic U46619. Phorbol 12-myristate 13-acetate (PMA), a direct activator of protein kinase C, also increased PLD activity. A selective inhibitor of protein kinase C, Ro-31-8220, totally blocked the stimulation of PLD by thrombin or PMA under conditions in which it also inhibited phosphorylation of pleckstrin, the major protein kinase C substrate in platelets. Ro-31-8220 additionally inhibited A23187-stimulated PLD activity, indicating that Ca2+ activation of PLD also occurs via a protein kinase C-dependent pathway. In the presence of the fibrinogen antagonist peptide RGDS, which inhibits fibrinogen binding to integrin alpha IIb beta 3 and allows little or no aggregation to occur, thrombin- and PMA-stimulated PLD activity was still observed, indicating that PLD activation is not simply a consequence of platelet aggregation. Furthermore, these agonists were able to stimulate PLD in platelets from a Glanzmann's thrombasthenia type I patient lacking the integrin alpha IIb beta 3 complex, which indicates that activation of PLD is also independent of the recruitment of integrin alpha IIb beta 3. Taken together, our results show that PLD is activated by a pathway involving protein kinase C, and suggest that PLD might be involved in signal transduction events occurring upstream of integrin alpha IIb beta 3 activation and fibrinogen binding, which are prerequisites for full platelet aggregation.

Structural determinants of calcium signaling by RGD peptides in rat osteoclasts: integrin-dependent and -independent actions.

Extensive characterization of the vitronectin receptor (VNR), a member of the integrin group of cell adhesion molecules, which is abundantly expressed in osteoclasts, has revealed a role for this receptor in osteoclast adhesion as well as bone resorption. Earlier evidence from our laboratory suggests that VNR is also capable of transducing intracellular signals following receptor ligand interaction, although this function is poorly understood. Thus, addition of peptides containing the minimal tripeptide Arg-Gly-Asp (RGD) integrin recognition sequence elicits transient increases in intracellular free calcium ions, with maximal responses seen with a bone sialoprotein peptide, BSP-IIA. In the present study we have attempted to determine some of the structural requirements for calcium signaling in osteoclasts using derivatives of the peptide PRGDN/T sequence found in bone sialoprotein. While some peptides, such as the parent sequence PRGDN, can induce both signaling and retractile events, it was found that minor structural modifications yielded peptides such as PRADN which elicited a transient increase in intracellular free calcium ions without promoting a reduction in osteoclast spread area (retraction). Conversely, certain other modifications resulted in peptides, such as PrGDN and benzoyl-RGDN, which effect osteoclast retraction, while having minimal Ca2+ signaling capabilities. Osteoclast adhesion, and hence retraction, are known to be RGD-dependent and integrin-dependent events. However, intracellular Ca2+ signaling is RGD-independent and, based on lack of inhibition by an anti-beta 3 integrin antibody F11 and echistatin, very likely integrin-independent. These data suggest that signaling is not always via VNR and as yet unknown receptors on the osteoclast membrane play a role in osteoclast signaling and hence function.

Expression and function of beta 1 and alpha v beta 3 integrins in ovarian cancer.

Ovarian cancer cells disseminate by implanting onto the peritoneal mesothelial cell surface of the abdominal cavity. A common feature of these peritoneal implants is the presence of tumor cell invasion into the submesothelial extracellular matrix (ECM). In view of the important role of integrins in ECM recognition and cell migration, we were interested in defining the pattern of integrin expression and function in ovarian cancer cell lines and primary tissue samples. The beta 1 integrin chain was expressed by CAOV-3, SKOV-3, OVCAR-3, and SW626 ovarian cancer cell lines, associated with expression of alpha 1, -2, -3, -5, and -6 chains. The alpha 4 chain was also expressed by two of the four lines. In addition to beta 1 integrins, the alpha v beta 3 integrin was also expressed, although there was no expression of beta 2, -4, and -7 chains. Immunoprecipitation of surface-labeled CAOV-3 cells with an anti-beta 1 antibody revealed a band at approximately 110-130 kDa consistent with the known molecular mass of the beta 1 chain, as well as several associated bands consistent with noncovalently linked integrin alpha chains. A similar pattern of beta 1 and alpha v beta 3 integrin expression was observed for primary ovarian cancer tissue samples. Ovarian cancer cell lines exhibited significant binding to collagen type I and laminin which was primarily mediated by beta 1 integrins. In contrast, ovarian cancer cell binding to fibronectin was mediated by both alpha 5 beta 1 and alpha v beta 3 integrins. Even though mesothelial cells were observed to express fibronectin mRNA and protein, binding of ovarian cancer cells to peritoneal mesothelium was not blocked by neutralizing antibodies to beta 1 or alpha v beta 3 integrins. These data suggest that functional integrins are commonly expressed by ovarian cancer cells, although they do not appear to mediate ovarian cancer cell implantation onto peritoneal mesothelium. The role that integrins play in the invasion of ovarian cancer cells into the submesothelial ECM deserves further investigation.

Fibrin II induces endothelial cell capillary tube formation.

We studied the formation of capillary tubes by endothelial cells which were sandwiched between two fibrin gels under serum-free conditions. After formation of the overlying fibrin gel, the endothelial cell monolayer rearranged into an extensive net of capillary tubes. Tube formation was apparent at 5 h and was fully developed by 24 h. The capillary tubes were vacuolated, and both intracellular and intercellular lumina were present. Maximal tube formation was observed with fibrin II (which lacks both fibrinopeptide A and B), minimal tube formation with fibrin I (which lacks only fibrinopeptide A), and complete absence of tube formation with fibrin 325 (which lacks the NH2-terminal beta 15-42 sequence, in addition to fibrinopeptides A and B). The inability of fibrin 325 to stimulate capillary tube formation supports the idea that beta 15-42 plays an important role in this process, and its importance was confirmed by the finding that exogenous soluble beta 15-42 inhibited fibrin II-induced capillary tube formation. This effect was specific for fibrin, since beta 15-42 did not inhibit tube formation by endothelial cells sandwiched between collagen gels. The interaction of the apical surface of the endothelial cell with the overlying fibrin II gel, as opposed to the underlying fibrin gel upon which the cells were seeded, was necessary for capillary tube formation. These studies suggest that the beta 15-42 sequence of fibrin interacts with a component of the apical cell surface and that this interaction plays a fundamental role in the induction of endothelial capillary tube formation.

Requirement of the NPXY motif in the integrin beta 3 subunit cytoplasmic tail for melanoma cell migration in vitro and in vivo.

The NPXY sequence is highly conserved among integrin beta subunit cytoplasmic tails, suggesting that it plays a fundamental role in regulating integrin-mediated function. Evidence is provided that the NPXY structural motif within the beta 3 subunit, comprising residues 744-747, is essential for cell morphological and migratory responses mediated by integrin alpha v beta 3 in vitro and in vivo. Transfection of CS-1 melanoma cells with a cDNA encoding the wild-type integrin beta 3 subunit, results in de novo alpha v beta 3 expression and cell attachment, spreading, and migration on vitronectin. CS-1 cells expressing alpha v beta 3 with mutations that disrupt the NPXY sequence interact with soluble vitronectin or an RGD peptide, yet fail to attach, spread, or migrate on immobilized ligand. The biological consequences of these observations are underscored by the finding that CS-1 cells expressing wild-type alpha v beta 3 acquire the capacity to form spontaneous pulmonary metastases in the chick embryo when grown on the chorioallantoic membrane. However, migration-deficient CS-1 cells expressing alpha v beta 3 with mutations in the NPXY sequence lose this ability to metastasize. These findings demonstrate that the NPXY motif within the integrin beta 3 cytoplasmic tail is essential for alpha v beta 3-dependent post-ligand binding events involved in cell migration and the metastatic phenotype of melanoma cells.

Soluble ligands of the alpha v beta 3 integrin mediate enhanced tyrosine phosphorylation of multiple proteins in adherent bovine pulmonary artery endothelial cells.

Binding of substrate-bound extracellular matrix proteins to cell surface integrins results in a variety of cellular responses including adhesion, cytoskeletal reorganization, and gene expression. We have previously shown that addition of soluble SC5b-9, the complement-vitronectin complex, resulted in an RGD-dependent increase in lung venular hydraulic conductivity (Ishikawa, S., Tsukada, H., and Bhattacharya, J. (1993) J. Clin. Invest. 91, 103-109). To identify specific integrin(s) and signal transduction pathways that are responsive to soluble vitronectin-containing ligands, we exposed confluent bovine pulmonary artery cells to purified soluble human mono- or multimeric vitronectin, or SC5b-9, and determined the extent of endothelial cell protein tyrosine phosphorylation. Monomeric vitronectin (Vn) did not induce enhanced protein tyrosine phosphorylation. However, multimeric Vn and SC5b-9 elicited time- and concentration-dependent increases in tyrosine phosphorylation of numerous proteins. Antiserum against vitronectin, RGD peptides, and monoclonal and polyclonal antibodies against the alpha v beta 3 integrin blocked the vitronectin- or SC5b-9-induced enhanced accumulation of tyrosine phosphoproteins, while antibodies against beta 1 integrins and the alpha v beta 5 integrin did not. Clustering of the alpha v beta 3 integrin using monoclonal antibody LM609 caused a pattern of enhanced tyrosine phosphorylation similar to that caused by multimeric Vn and SC5b-9, suggesting that aggregation of alpha v beta 3 was critical for signaling. Among the proteins that underwent enhanced tyrosine phosphorylation in response to vitronectin were the cytoskeletal proteins paxillin, cortactin, and ezrin, as well as the SH2 domain-containing protein Shc, and p125FAK. We conclude that ligation of the alpha v beta 3 integrin by soluble ligands promotes enhanced phosphorylation of several proteins implicated in tyrosine kinase signaling and suggest that this pathway may be important in inflammatory states which are accompanied by accumulation of SC5b-9.

Extracellular matrix proteins and leukocyte function.

Extracellular matrix (ECM) proteins profoundly affect physiological functioning at the cellular level. Cell growth and differentiation, as well as cell shape and migration via the cytoskeleton, are all affected by ECM proteins. Leukocyte interactions with matrices have recently become an exciting field of research because a number of different leukocyte functions are significantly affected by their binding to ECM proteins. This may be especially important in inflammatory responses where leukocytes are primed for inflammatory mediator and cytokine production by binding to ECM proteins during extravasation. Because activated leukocytes produce potentially damaging substances, the progress of an inflammatory response can be profoundly affected by the ECM proteins encountered by leukocytes during their migration from within the peripheral circulation to sites of inflammation. This review summarizes recent publications describing components of the ECM that influence leukocyte function, the receptors involved in leukocyte binding to ECM proteins, and focuses on the effects of ECM proteins on the production of inflammatory mediators and cytokines by human peripheral blood leukocytes.

Osteopontin expression in cardiovascular diseases.

Adhesive interactions are recognized requirements for cellular proliferation, migration and differentiation during normal morphogenesis as well as disease. By differential cloning, osteopontin was identified as an adhesive protein upregulated during vascular remodeling and neointima formation in both rat models and human vascular diseases including atherosclerosis and restenosis. In functional studies, purified osteopontin promoted adhesion, focal contact formation, and migration of vascular smooth muscle and endothelial cells. Utilizing neutralizing antibodies, three integrin-type receptors, alpha v beta 3, alpha v beta 1, and alpha v beta 5 were found to support cellular adhesion to osteopontin. In contrast, only cells containing the alpha v beta 3 integrin could migrate towards an osteopontin gradient, demonstrating for the first time that different functions of osteopontin are mediated via distinct receptors. These results suggest a model whereby osteopontin, via its integrin-type receptors, contributes to vascular remodeling during development and disease by facilitating smooth muscle migration and simultaneously promoting endothelial coverage of the affected area.