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PubMed1996

Divalent cations regulate the organization of integrins alpha v beta 3 and alpha v beta 5 on the cell surface.

Extracellular divalent cations are important regulators of integrin ligand binding activity. In this study we evaluated how divalent cations affect the organization of integrins into focal adhesion sites. Integrins alpha v beta 3 and alpha v beta 5 were compared because they share a high degree of structural homology and because both integrins mediate cell adhesion to vitronectin. On MG-63 osteosarcoma cells, we found that both the extent and pattern of integrin organization was regulated by the type of extracellular divalent ion. Integrin alpha v beta 3 organized in focal contacts when Mn2+ or Mg2+ was present, but not in Ca2+. In contrast, alpha v beta 5 organized in focal contacts only when Ca2+ or Mg2+ was present. Integrin alpha v beta 5 clustered in a centrally located punctate field on the ventral surface of the cell in the presence of Mn2+. These observations reveal a previously unappreciated role for divalent ions in regulating the organization of integrins into focal adhesion sites.

Antigens, CD↗
PubMed1998

Inhibition of bone resorption by 17beta-estradiol in human bone marrow cultures.

Estrogen deficiency puts individuals at risk of developing osteoporosis because it causes increased bone resorption. However, the mechanism by which this occurs is not known. We have shown, using a recently described two-phase human bone marrow culture system, that estradiol (17beta-E2) added to phase I results in inhibition of bone resorption by reducing the number of osteoclasts (identified as vitronectin receptor and/or calcitonin receptor-positive cells) formed in the cultures. The addition of 17beta-E2 in phase II was without effect, indicating that it does not interfere with the bone resorptive process. 17Beta-E2 down-regulated mRNA expression and protein synthesis of the membrane form of macrophage colony-stimulating factor (M-CSF). 17Beta-E2 did not the alter the expression of the 4.0 kb M-CSF transcript. However, it increased protein synthesis of the proteoglycan form of M-CSF, but not the 85 kDa soluble form in the same cultures. Finally, addition of M-CSF to the cultures reversed the 17beta-E2-induced inhibitory effect. These observations suggest that regulation of the synthesis of membrane-bound M-CSF plays a role in 17beta-E2-induced inhibition of bone resorption.

Actins↗
PubMed1998

Bone sialoprotein supports breast cancer cell adhesion proliferation and migration through differential usage of the alpha(v)beta3 and alpha(v)beta5 integrins.

Bone sialoprotein (BSP), a secreted glycoprotein found in bone matrix, has been implicated in the formation of mammary microcalcifications and osteotropic metastasis of human breast cancer (HBC). BSP possesses an integrin-binding RGD (Arg-Gly-Asp) domain, which may promote interactions between HBC cells and bone extracellular matrix. Purified BSP, recombinant human BSP fragments and BSP-derived RGD peptides are shown to elicit migratory, adhesive, and proliferative responses in the MDA-MB-231 HBC cell line. Recombinant BSP fragment analysis localized a significant component of these activities to the RGD domain of the protein, and synthetic RGD peptides with BSP flanking sequences (BSP-RGD) also conferred these responses. The fibronectin-derived RGD counterpart, GRGDSP (Gly-Arg-Gly-Asp-Ser-Pro), could not support these cellular responses, emphasizing specificity of the BSP configuration. Although most of the proliferative and adhesive responses could be attributed to RGD interactions, these interactions were only partly responsible for the migrational responses. Experiments with integrin-blocking antibodies demonstrated that BSP-RGD-induced migration utilizes the alpha(v)beta3 vitronectin receptor, whereas adhesion and proliferation responses were alpha(v)beta5-mediated. Using fluorescence activated cell sorting, we selected two separate subpopulations of MDA-MB-231 cells enriched for alpha(v)beta3 or alpha(v)beta5 respectively. Although some expression of the alternate alpha(v) integrin was still retained, the alpha(v)beta5-enriched MDA-MB-231 cells showed enhanced proliferative and adhesive responses, whereas the alpha(v)beta3-enriched subpopulation was suppressed for proliferation and adhesion, but showed enhanced migratory responses to BSP-RGD. In addition, similar analysis of two other HBC cell lines showed less marked, but similar RGD-dependent trends in adhesion and proliferation to the BSP fragments. Collectively, these data demonstrate BSP effects on proliferative, migratory, and adhesive functions in HBC cells and that the RGD-mediated component differentially employs alpha(v)beta3 and alpha(v)beta5 integrin receptors.

Antibodies, Monoclonal↗
PubMed1999

ETS-1 converts endothelial cells to the angiogenic phenotype by inducing the expression of matrix metalloproteinases and integrin beta3.

The transcription factor ETS-1 is induced in endothelial cells (ECs) by angiogenic growth factors and the specific elimination of ETS-1 synthesis by antisense oligodeoxynucleotide inhibited angiogenesis in vitro (Iwasaka et al., 1996, J Cell Physiol 169:522-531). To understand the precise role of ETS-1 in angiogenesis, we established both high and low ETS-1 expression EC lines and compared angiogenic properties of these cell lines with those of the parental murine EC line, MSS-31. Although growth rate was almost identical for each cell line, the invasiveness was markedly enhanced in high ETS-1 expression cells and reduced in low ETS-1 expression cells compared with that of parental cells. The gene expressions of matrix metalloproteinases (MMP-1, MMP-3, and MMP-9) and gelatinolytic activity of MMP-9 were significantly increased in high ETS-1 expression cells. Low ETS-1 expression cells could not spread on a vitronectin substratum, and the phosphorylation of focal adhesion kinase was markedly impaired because of the reduced expression of integrin beta3. These results indicate that ETS-1 is a principal regulator that converts ECs to the angiogenic phenotype.

Actins↗
PubMed2001

Expression and activity of matrix metalloproteases in human malignant mesothelioma cell lines.

The extracellular matrix metalloproteases (MMPs) secreted by various human tumor cells play a crucial role in tumor cell invasion and metastasis, but their expression in malignant mesothelioma (MM) cells has not been examined. In this study, we have investigated the spectrum of MMPs and tissue inhibitors of metalloproteases (TIMPs) produced by 8 MM cell lines. Using RT-PCR, we found that all investigated MM cell lines expressed genes encoding mRNA for MMP-1 (interstitial collagenase), MMP-2 (gelatinase A), MMP-3 (stromelysin-1), MMP-9 (gelatinase B) and TIMPs 1, 2 and 3. We also found that 6/8 MM cell lines expressed MMP-7 (matrilysin) and 3/8 MM cell lines expressed MMP-10 (stromelysin-2). MMP-11 (stromelysin-3) was not detected in any of the MM cell lines. Production of MMP-2 and MMP-9 was confirmed using gelatin zymography. In addition, all MM cell lines secreted a 66 kDa metalloprotease, while 3/8 MM cell lines secreted 46, 48, 51 and 63 kDa metalloproteases which specifically degraded the extracellular matrix components fibronectin, vitronectin and laminin. The 66 kDa protease was identified as MMP-3 by Western blot. Our results reveal a broad spectrum of MMPs and TIMPs produced by MM cells and indicate that different substrate specificities of MMPs may play a role in MM cell invasion.

Blotting, Western↗
PubMed2000

Specific proteins mediate enhanced osteoblast adhesion on nanophase ceramics.

Osteoblast, fibroblast, and endothelial cell adhesion on nanophase (that is, materials with grain sizes less than 100 nm) alumina, titania, and hydroxyapatite (HA) was investigated using in vitro cellular models. Osteoblast adhesion was significantly (p < 0.01) greater after 4 h on nanophase alumina, titania, and HA than it was on conventional formulations of the same ceramics. In contrast, compared to conventional alumina, titania, and HA, after 4 h fibroblast adhesion was significantly (p < 0.01) less on nanophase ceramics. Examination of the underlying mechanism(s) of cell adhesion on nanophase ceramics revealed that these ceramics adsorbed significantly (p < 0.01) greater quantities of vitronectin, which, subsequently, may have contributed to the observed select enhanced adhesion of osteoblasts. Select enhanced osteoblast adhesion was independent of surface chemistry and material phase but was dependent on the surface topography (specifically on grain and pore size) of nanophase ceramics. The capability of synthesizing and processing nanomaterials with tailored (through, for example, specific grain and pore size) structures and topographies to control select subsequent cell functions provides the possibility of designing the novel proactive biomaterials (that is, materials that elicit specific, timely, and desirable responses from surrounding cells and tissues) necessary for improved implant efficacy.

Adsorption↗
PubMed2002

Characterization of plasma factors that alter the permeability to albumin within isolated glomeruli.

Focal segmental glomerulosclerosis (FSGS) is responsible for intractable proteinuria and has become the leading cause of renal insufficiency in children. Protenuria in FSGS is probably due to the effect of one or more permeability plasma factors which increase the glomerular permeability to proteins. We fractioned serum from children with FSGS using two mixed chromatographic-electrophoretic approaches and have purified ten proteins among several hundreds which maintained the original permeability activity after renaturation, utilizing an isolated rat glomeruli assay. Six proteins were successfully characterized by mass spectometry as fibulin, apolipoprotein J, vitronectin, albumin isoforms, gamma chain fibrinogen and mannan-binding lectin-associated serine protease. Both procedures utilized for purification were based on affinity chromatography with Protein A-Sepharose and ended with two-dimensional electrophoresis, whereas the intermediate steps were different. Cross inhibition with zinc and aprotinin of purified factors and whole FSGS serum indicate strong homology. These are the first data demonstrating permeability activity for serum proteins, an observation with important implications in pathogenesis of proteinuria. Determination of the serum levels of each protein and a careful differentiation of FSGS from normal serum could provide the basis for clarifying the mechanism of proteinuria.

Adolescent↗
PubMedDate not supplied

Variability in the expression of urokinase receptor (CD87) mutants on cells: relevance to cell adhesion.

The urokinase-type plasminogen activator receptor (uPAR, CD87) is a glycosylphosphatidylinositol (GPI)-anchored protein, containing three homologous Ly-6 domains, that mediates integrin-independent cell adhesion by directly binding to extracellular matrix protein vitronectin (VN). To elucidate the structural requirements for the uPAR-dependent cell adhesion on VN, several glycolipid-anchored variants of uPAR were expressed in BAF3 cells, (mouse pre B-lymphocytes) followed by functional analysis. The individual domains of uPAR were expressed at very low levels, the two domain mutants were expressed to a higher level and the wild type uPAR was expressed highly. Point mutations in domain 2 of uPAR have been shown to diminish cellular binding of the ligand urokinase and we observed a lack of VN binding to this mutant. Flow cytometry with a number of monoclonal antibodies indicated that the domain-specific antigenic determinants in these mutants were well preserved. Only the cells expressing the intact uPAR with all three domains adhered strongly to a VN substrate, whereas none of the other transfected cells showed significant cell adhesion. Hence, any alterations in the domain structure of uPAR reduce its expression and only the intact receptor can sustain the direct cell adhesion on VN-rich matrices found at sites of inflammation and injury.

Amino Acid Substitution↗
PubMed1991

Mechanisms of interaction between human skin fibroblasts and elastin: differences between elastin fibres and derived peptides.

3H-Labelled kappa-elastin peptides (kE:75 kDa molecular weight) were shown to bind to confluent human skin fibroblast (HSF) cultures in a time-dependent and saturable manner. Scatchard analysis indicated the presence of high affinity binding sites with kD = 2.7 x 10(-10) M and 19,000 sites per cell. Binding of kE to its receptor on HSF accelerates and intensifies the adhesion of insoluble elastin fibres (iE) to confluent HSF. Optimal effect was attained for a kE concentration of 0.3 x 10(-9) M close to kD. This stimulatory effect of kE on the binding of iE to HSF could be inhibited by neomycin, retinal and pertussis toxin, substances which act at different levels of the transduction mechanism following the activation of the receptor and the subsequent triggering of cell biological events (chemotaxis, modification of calcium fluxes). The stimulation of iE adhesion to HSF induced by kE as well as kE binding to the cells could be inhibited by lactose and laminin but not by Arg-Gly-Asp-Ser(RGDS) peptides. This indicates that the elastin peptide receptor on HSF possesses lectin-like properties and shares homology with the laminin receptor as also shown for other cell types. None of the substances tested, that is inhibitors of the transduction mechanism, lactose, laminin and Arg-Gly-Asp-Ser(RGDS) peptides were shown to interfere significantly with the binding of iE (in the absence of added kE) to confluent HSF. The proteins adhering strongly to elastin fibres were isolated by a sequential extraction procedure and the final hydrochloride guanidinium-DTT extract was analysed by SDS-PAGE under reducing conditions, Western blots using specific antibodies against several connective tissue proteins and affinity for [3H]-kE following nitrocellulose electro-transfer of proteins. Fibronectin, vitronectin, tropoelastin(s), and a 120 kDa cysteine rich glycoprotein previously designated as elastonectin were identified. Among these proteins, [3H]-kE was found to bind exclusively to a 65 kDa protein that could be eluted selectively from elastin fibres with a neutral buffer containing 100 mM lactose. Therefore the elastin peptide receptor on human skin fibroblasts shares properties with the elastin receptor characterized from other cell types. Conformational differences between elastin peptides and elastin fibres could explain the differences in the mechanisms of interactions between elastin fibres and elastin peptides with HSF in culture. The stimulatory effect of elastin-derived peptides on the adhesion of elastin fibres to HSF could have implications in the oriented biosynthesis of elastin fibres.

Adult↗
PubMed2004

Radial glia produce and align the ligand fibronectin during neuronal migration in the developing chick brain.

We demonstrated previously that alpha8beta1 integrin regulates the migration and survival of immature neurons during development of the chicken optic tectum; however, the potential extracellular ligand was unknown. We used immunohistochemistry to determine if several potential ligands (fibronectin, tenascin, vitronectin, and osteopontin) were expressed during neuronal migration along radial glia (RG). Fibronectin was localized in a pattern relevant to radial migration and survival of neurons; it was present before and during neuronal migration and appeared oriented along RG fibers by conventional fluorescence microscopy. Confocal microscopy confirmed that fibronectin was localized along RG cells during radial migration. It was more concentrated in some superficial laminae, which might support directional movement. Fibronectin was present after formation of definitive tectal laminae, but was diffuse and not aligned along RG, which persist. Flow cytometry analysis of dissociated optic tectum cells revealed that almost all RG were positive for fibronectin. Short-term cell culture experiments using an exocytosis inhibitor revealed that fibronectin accumulated in most RG cells. Thus, fibronectin is produced by RG and is aligned along their surfaces before and during migration. Fibronectin, therefore, is a potential ligand for general radial neuronal migration in the chick optic tectum. Its predominant source appears to be RG, in contrast with developing mammalian cortex, where fibronectin was not found in a pattern that could guide widespread radial migration and where neurons are the predominant producers of fibronectin during migration.

Animals↗
PubMed1991

Antigen-independent T cell activation mediated by a very late activation antigen-like extracellular matrix receptor.

Cell-cell and cell-extracellular matrix (ECM) binding mediated by integrin molecules has been implicated in lymphocyte migration and adhesion. We describe here that ECM binding triggers antigen-independent activation of T cell functions. Fibronectin and vitronectin, when coated on plates, not only acted synergistically on anti-CD3-induced serine esterase release in a murine cytotoxic T lymphocyte clone and interleukin 2 production in a murine helper T cell hybridoma but also could trigger these responses alone. All these stimulatory effects of ECM were abrogated by a monoclonal antibody which reacts with a unique very late activation antigen-like integrin and this monoclonal antibody, when coated on plates, exhibited a similar synergistic effect to that of ECM proteins. Therefore, ECM receptors expressed on activated T cells appear to play an important role in triggering T cell effector functions in localized tissues abundant in ECM proteins.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1994

Recognition of apoptotic cells by human macrophages: inhibition by a monocyte/macrophage-specific monoclonal antibody.

Cells undergoing death by apoptosis are rapidly engulfed by phagocytes in vivo, a highly efficient process which prevents leakage of potentially dangerous intracellular contents from dying cells to neighboring tissue. We have tested a panel of monoclonal antibodies (mAb) specifying a range of human monocyte/macrophage surface antigens for their capacity to inhibit the in vitro recognition of apoptotic cells by human peripheral blood monocyte-derived macrophages. The results identify the antigen defined by the 61D3 mAb, a widely-used marker of monocyte/macrophage lineage cells, as an important mediator of apoptotic cell recognition. In our system, apoptotic, but not viable, cells were recognized by the cultured macrophages and 61D3 was found to inhibit the recognition of all apoptotic cell types tested, including Ca2+ ionophore-treated or growth factor-depleted B and T lymphocyte lines, tonsillar germinal center B cells, irradiated peripheral blood lymphocytes and senescing neutrophils. Furthermore, the apoptotic cell recognition pathway specified by 61D3 could be distinguished from that involving the macrophage alpha v beta 3 vitronectin receptor which has been shown previously to play an important role in the recognition of apoptotic cells. These results provide further evidence that the mechanisms underlying rapid clearance of apoptotic cells involve multiple phagocyte receptors.

Animals↗
PubMed1997

Cross talk between alpha(v)beta3 and alpha4beta1 integrins regulates lymphocyte migration on vascular cell adhesion molecule 1.

Local inflammation leads to increased expression of the vascular cell adhesion molecule (VCAM)-1 on vascular endothelium which contributes to the encapture of leukocytes from the circulating blood through the leukocyte ligand alpha4beta1 integrin. Inflammatory vascular endothelium expresses VCAM-1 at high density. We found that the speed of locomotion of activated lymphocytes migrating along surfaces coated with recombinant VCAM-1 at a comparable density to that found on inflammatory endothelium was slow. However, lymphocytes do migrate and extravasate rapidly under inflammatory conditions, indicating that there must be mechanisms that regulate the interaction between alpha4beta1 and VCAM-1 in vivo. Here we show that the lymphocyte alpha(v)beta3 integrin and integrin-associated protein (IAP) is able to regulate this interaction. The occupancy of lymphocyte alpha(v)beta3 integrin by platelet cell adhesion molecule-1 or vitronectin regulated the speed of alpha4beta1 integrin-dependent locomotion of lymphocytes on recombinant VCAM-1. This allowed rapid lymphocyte migration at VCAM-1 densities which are typical of inflammatory vessels. This alpha(v)beta3-mediated enhanced migration of lymphocytes via alpha4beta1 is likely to depend on the interaction of alpha(v)beta3 integrin with the IAP. Furthermore, this motile process correlates with polarization of the actin cytoskeleton in lymphocytes. Our results suggest that cross talk between alpha(v)beta3 integrin and alpha4beta1 integrin is a mechanism in the regulation of lymphocyte locomotion along inflammatory endothelium and subsequent transendothelial migration. This can explain how lymphocytes overcome tight adhesion to the vascular endothelium and start rapid migration along and through the endothelial lining of blood vessels into inflammatory tissue.

Animals↗
PubMed2005

Transmigration of human ovarian adenocarcinoma cells through endothelial extracellular matrix involves alphav integrins and the participation of MMP2.

The growth of ovarian carcinoma is dependent upon their vascularistion, but the interaction of ovarian cancer cells with the endothelium and their invasion through an endothelial environment remain poorly understood at the molecular level. To investigate adhesive events underlying this process with focusing on the role of alphav integrins and MT1MMP-MMP2 proteinases, we used in vitro models of cocultures of human ovarian adenocarcinoma cell lines (IGROV1 and SKOV3) with human umbilical vein endothelial cells (HUVECs). Immunostaining of HUVECs revealed the network organisation of fibrillar fibronectin (Fn) and pericellular vitronectin (Vn). During coculture, IGROV1 and SKOV3 cells gain access to subendothelial basement membrane of HUVECs and dislocated endothelial Fn without affecting endothelial Vn. Transmigration assays revealed that tumour cells invade Vn and, with an higher efficiency, Fn. Our data also highlighted that ovarian carcinoma cells migrated through the Fn-rich HUVEC-ECM. The expression of MMP2 and MT1-MMP was revealed in tumour cells within an endothelial environment. Furthermore, we found that cell migration through the endothelial ECM was almost totally dependent on alphav integrin function, whereas beta1 integrins were not solicited. In addition, inhibitors of MMP2 activity (alone or combined with anti-alphav integrin MAb) or TSRI265 (which blocks MMP2-alphavbeta3 association) were found to impede this process. Finally, alphav integrins, MT1-MMP and MMP2 were found in ovarian carcinoma cells within the 3-dimensional architecture of intraperitoneal tumour nodes collected from nude mice xenografted with IGROV1 or SKOV3 cell lines or within human tumour tissues. alphav integrins therefore appear as essential to the migration properties of human ovarian carcinoma cells, especially in an endothelial environment, with MMP2 participating to this process.

Animals↗
PubMed2005

Alpha6 integrin subunit mediates laminin enhancement of cisplatin-induced apoptosis in testicular tumor germ cells.

Our study demonstrates that laminin potentiates cisplatin-induced apoptosis in NCCIT, a testicular tumor germ cell line. When cultured on laminin, NCCIT cells displayed a significantly higher susceptibility to cisplatin-induced apoptosis than on plastic or on other ECM components including fibronectin, Type IV collagen and vitronectin. This high cisplatin sensitivity observed on NCCIT cell cultured on laminin was mediated by the alpha6-integrin signaling. The knockdown of the alpha6-integrin subunit by small interfering RNAs suppressed the higher cisplatin-sensitivity supporting the existence of a crosstalk between laminin-alpha6-integrin signaling and cisplatin-induced apoptosis. Our findings indicate that in cisplatin-treated NCCIT cells, the laminin-alpha6-integrin signaling induces the activation of executioner procaspase-3 and -6 as well as apoptosis-inducing factor (AIF) transcription and expression. The ability of integrin-mediated specific stroma-tumor cell interactions to modulate the chemosensitive phenotype of a tumor cell might provide new insights to overcome cisplatin resistance of tumor cells.

Apoptosis↗
PubMed1993

Inhibition of metastatic cell colonization in murine lungs and tumor-induced morbidity by non-peptidic Arg-Gly-Asp mimetics.

The spreading and colonization of tumor cells require their migration to metastatic sites via blood vessels. To penetrate blood-vessel walls, cells, including malignant ones, must recognize and associate with the sub-endothelium extracellular matrix (ECM) and its glycoproteins. Recognition of ECM-glycoproteins, such as fibronectin (FN) and vitronectin (VN), is mediated by integrin receptors expressed on various cell types, including platelets, leukocytes and tumor cells. The Arg-Gly-Asp (RGD)-containing peptide, a major adhesive ligand of ECM, is present in various plasma and matrix glycoproteins, such as FN and VN. Non-peptidic mimetics of RGD, consisting of carboxylate and guanidinium groups of Asp and Arg divided by a linear atom spacer, express a high affinity for the alpha IIb-beta 3 integrin and inhibit platelet aggregation. Herein, the ability of RGD mimetics to inhibit adhesive interactions between tumor cells and RGD, and tumor progression in vivo, was examined. RGD-containing peptides and the RGD mimetic, compound SF-6,5, but not the Arg-Gly-Glu (RGE) peptide or the corresponding mimetic, specifically inhibited B16-F10 melanoma cell adhesion to immobilized VN and FN. Daily administration in vivo of SF-6,5 to mice inhibited the formation of B16-F10 colonies in experimental and spontaneous models of metastases. Moreover, SF-6,5 could prevent mouse death caused by massive colonization of tumor cells in the lungs. The therapeutic effect of RGD-containing peptides on tumor metastasis formation was marginal, probably due to the small amounts used, and its susceptibility to proteolysis in situ. Thus, non-peptidic mimetics of small adhesive epitopes may provide a novel therapeutic tool to prevent an adverse pathological event involving integrin-dependent cell-cell and cell-ECM interactions.

Animals↗
PubMed1995

Gelatinase A activity directly modulates melanoma cell adhesion and spreading.

Interaction of cells with the extracellular matrix (ECM) plays an important role in the regulation of cell behavior. Formation of adhesive contacts leads to transduction of signals into the cell and results in altered gene expression and modulation of the cellular phenotype. Specific adhesive interactions of the fibronectin and vitronectin receptors with their ligands in the matrix modulates expression of ECM-degrading metalloproteases. These proteases are involved in the acquisition of the invasive phenotype by a number of cell types. The activity of matrix metalloproteases (MMPs) is reduced by endogenous inhibitors referred to as tissue inhibitors of metalloproteases (TIMPs). Alterations in the balance between the activity of MMPs and TIMPs alters cellular invasion through effects on matrix degradation. In this study we demonstrate that inhibition of endogenous gelatinase A activity in A2058 human melanoma cells results in enhanced cellular adhesion. To further explore this phenomenon, we have used retroviral infection vectors to control the amount of the MMP inhibitor TIMP-2 in human melanoma A2058 cells. Altering the production of TIMP-2 modulates not only proteolysis of the extracellular matrix, but also the adhesive and spreading properties of the cells and results in altered cell morphology. These effects of TIMP-2 appear to be mediated by inhibition of gelatinase A activity. We conclude that gelatinase A, in addition to contributing to proteolysis of ECM components, also functions to proteolyse cell surface components that mediate attachment of A2058 cells to the ECM. Thus, gelatinase A may function to modulate cell attachment and facilitate cell migration and invasion.

Cell Adhesion↗
PubMed2002

Fluorinated surface-modifying macromolecules: modulating adhesive protein and platelet interactions on a polyether-urethane.

Polyether-urethanes (PEUs) have been the materials of choice for the manufacture of conventional blood-contacting devices. Nevertheless, biostability and blood compatibility are still among the principal limitations in their long-term application. Studies investigating the development of protective coatings for PEUs have shown that degradation can be reduced with the use of fluorinated surface-modifying macromolecules (SMMs). It has also been hypothesized that SMM-modified PEU surfaces may exhibit improved blood compatibility because other studies have shown a modulation in fibrinogen adsorption onto these surfaces. To determine the blood compatibility of a PEU-containing fluorinated SMMs, a series of in vitro experiments were designed to study the pattern of protein adsorption from plasma and then to assess the nature of platelet adhesion and activation on each substrate. Western blot analysis as well as single protein studies revealed that the dominant "adhesive proteins" [fibrinogen (Fg), fibronectin (Fnc), and vitronectin (Vnc)] were adsorbed on two of the SMM-containing PEUs in lower amounts relative to unmodified base. Platelet adhesion and activation data further highlighted the differences among the various substrates. It was shown that the unmodified base had a higher number of adhered platelets relative to the SMM-modified surfaces, and that of the SMM-containing substrates, which showed the lowest levels of adhesive proteins also, exhibited significantly lower platelet densities. Close morphological examination further revealed that platelets residing on these latter substrates were not appreciably activated. Based on the current evidence, it is believed that the fluorinated SMMs demonstrate good potential for the development of surfaces with minimal thrombogenic character in in vivo applications.

Adsorption↗