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PubMed1997

Inhibition of RPE cell-mediated matrix adhesion and collagen gel contraction by crovidisin, a collagen-binding snake venom protein.

PURPOSE: Cell-mediated collagen gel contraction plays an important role in the pathogenesis of proliferative vitreoretinopathy (PVR). Anti-adhesion therapy has been suggested as a promising strategy in the treatment of PVR. Crovidisin, a snake venom protein isolated from Crotalus viridis, has been shown to bind selectively to collagen and to inhibit collagen-induced platelet aggregation. In the present study, the effectiveness of crovidisin in inhibiting the attachment of retinal pigment epithelial (RPE) cells to collagen, and RPE cell-mediated collagen gel contraction, was evaluated. METHODS: Fluorescein isothiocyanate (FITC)-conjugated crovidisin was prepared and used to evaluate its binding affinity for collagen type I, fibronectin, vitronectin, and laminin. The inhibitory effect of crovidisin on RPE cell-mediated extracellular matrix attachment and collagen gel contraction was evaluated by cell adhesion and type I collagen gel contraction assays. The cytotoxic effect of crovidisin was examined with a cell proliferation assay, using the Alamar blue method. Flavoridin, an Arg-Gly-Asp-containing peptide from viper venom, was used for comparison. RESULTS: FITC-conjugated crovidisin bound selectively to collagen type I with high affinity. It did not bind to other matrix proteins, including fibronectin, vitronectin and laminin, nor to RPE cells. Crovidisin inhibited RPE cell attachment to type I collagen in a dose-dependent manner. This inhibitory effect was enhanced by the presence of flavoridin. Crovidisin also dose-dependently inhibited RPE cell-mediated type I collagen gel contraction. Crovidisin was non-toxic to RPE cells. CONCLUSIONS: Crovidisin, a snake venom-derived collagen-binding protein, possessing an inhibitory activity on RPE cell-collagen interaction and RPE cell-mediated collagen gel contraction, may be a useful tool for studying cell-collagen interaction, and a potential anti-adhesion therapeutic agent for ocular disorders in which cell-collagen interaction in involved, such as PVR.

Animals↗
PubMedDate not supplied

Integrin alphaIIb-subunit cytoplasmic domain mutations demonstrate a requirement for tyrosine phosphorylation of beta3-subunits in actin cytoskeletal organization.

Using truncated or mutated alphaIIb integrin cytoplasmic domains fused to the alphaV extracellular domain and expressed with the beta3 integrin subunit, we demonstrate that the double mutation of proline residues 998 and 999 to alanine (PP998/999AA), previously shown to disturb the C-terminal conformation of the alphaIIb integrin cytoplasmic domain, prevents tyrosine phosphorylation of beta3 integrin induced by Arg-Gly-Asp peptide ligation. This mutation also inhibits integrin mediated actin assembly and cell adhesion to vitronectin. In contrast, progressive truncation of the alphaIIb-subunit cytoplasmic domain did not reproduce these effects. Interestingly, the PP998/999AA mutations of alphaIIb did not affect beta3 tyrosine phosphorylation, cell adhesion, or actin polymerization induced by manganese. Exogenous addition of manganese was sufficient to rescue beta3 phosphorylation, cell adhesion, and actin assembly in cells expressing the PP998/999AA mutation when presented with a vitronectin substrate. Further, induction of the high affinity conformation of this mutant beta3 integrin by incubation with either Arg-Gly-Asp peptide or exogenous manganese was equivalent. These results suggest that the extracellular structure of beta3 integrins in the high affinity conformation is not directly related to the structure of the cytoplasmic face of the integrin. Moreover, the requirement for beta3 phosphorylation is demonstrated without mutation of the beta3 subunit. In support of our previous hypothesis of a role for beta3 phosphorylation in adhesion, these studies demonstrate a strong correlation between beta3 tyrosine phosphorylation and assembly of a cytoskeleton competent to support firm cell adhesion.

Actins↗
PubMed1987

A cell surface receptor complex for collagen type I recognizes the Arg-Gly-Asp sequence.

To isolate collagen-binding cell surface proteins, detergent extracts of surface-iodinated MG-63 human osteosarcoma cells were chromatographed on affinity matrices of either type I collagen-Sepharose or Sepharose carrying a collagen-like triple-helical peptide. The peptide was designed to be triple helical and to contain the sequence Arg-Gly-Asp, which has been implicated as the cell attachment site of fibronectin, vitronectin, fibrinogen, and von Willebrand factor, and is also present in type I collagen. Three radioactive polypeptides having apparent molecular masses of 250 kD, 70 kD, and 30 kD were distinguishable in that they showed affinity toward the collagen and collagen-like peptide affinity columns, and could be specifically eluted from these columns with a solution of an Arg-Gly-Asp-containing peptide, Gly-Arg-Gly-Asp-Thr-Pro. These collagen-binding polypeptides associated with phosphatidylcholine liposomes, and the resulting liposomes bound specifically to type I collagen or the collagen-like peptide but not to fibronectin or vitronectin or heat-denatured collagen. The binding of these liposomes to type I collagen could be inhibited with the peptide Gly-Arg-Gly-Asp-Thr-Pro and with EDTA, but not with a variant peptide Gly-Arg-Gly-Glu-Ser-Pro. We conclude from these data that these three polypeptides are membrane molecules that behave as a cell surface receptor (or receptor complex) for type I collagen by interacting with it through the Arg-Gly-Asp tripeptide adhesion signal. The lack of binding to denatured collagen suggests that the conformation of the Arg-Gly-Asp sequence is important in the recognition of collagen by the receptor complex.

Amino Acid Sequence↗
PubMed1989

Von Willebrand factor promotes endothelial cell adhesion via an Arg-Gly-Asp-dependent mechanism.

Von Willebrand factor (vWF) is a constitutive and specific component of endothelial cell (EC) matrix. In this paper we show that, in vitro, vWF can induce EC adhesion and promote organization of microfilaments and adhesion plaques. In contrast, human vascular smooth muscle cells and MG63 osteosarcoma cells did not adhere and spread on vWF. Using antibodies to the beta chains of fibronectin (beta 1) and vitronectin (beta 3) receptors it was found that ECs adherent to vWF show clustering of both receptors. The beta 1 receptor antibodies are arranged along stress fibers at sites of extracellular matrix contact while the beta 3 receptor antibodies were sharply confined at adhesion plaques. ECs release and organize endogenous fibronectin early during adhesion to vWF. Upon blocking protein synthesis and secretion, ECs can equally adhere and spread on vWF but, while the beta 3 receptors are regularly organized, the beta 1 receptors remain diffuse. This suggests that the organization of the beta 1 receptors depend on the release of fibronectin and/or other matrix proteins operated by the same cell. Antibodies to the beta 3 receptors fully block EC adhesion to vWF and detach ECs seeded on this substratum. In contrast, antibodies to the beta 1 receptors are poorly active. Overall these results fit with an accessory role of beta 1 receptors and indicate a leading role for the beta 3 receptors in EC interaction with vWF. To identify the EC binding domain on vWF we used monoclonal antibodies produced against a peptide representing the residues Glu1737-Ser1750 of the mature vWF and thought to be important in mediating its binding to the platelet receptor glycoprotein IIb-IIIa. We found that the antibody that recognizes the residues 1,744-1,746, containing the Arg-Gly-Asp sequence, completely inhibit EC adhesion to vWF whereas a second antibody recognizing the adjacent residues 1,740-1,742 (Arg-Gly-Asp-free) is inactive. Both antibodies do not interfere with EC adhesion to vitronectin. This defines the molecular domain on vWF that is specifically recognized by ECs and reaffirms the direct role of the Arg-Gly-Asp sequence as the integrin receptor recognition site also in the vWF molecule.

Actin Cytoskeleton↗
PubMed1989

Analysis of fibronectin receptor function with monoclonal antibodies: roles in cell adhesion, migration, matrix assembly, and cytoskeletal organization.

We have developed two rat mAbs that recognize different subunits of the human fibroblast fibronectin receptor complex and have used them to probe the function of this cell surface heterodimer. mAb 13 recognizes the integrin class 1 beta polypeptide and mAb 16 recognizes the fibronectin receptor alpha polypeptide. We tested these mAbs for their inhibitory activities in cell adhesion, spreading, migration, and matrix assembly assays using WI38 human lung fibroblasts. mAb 13 inhibited the initial attachment as well as the spreading of WI38 cells on fibronectin and laminin substrates but not on vitronectin. Laminin-mediated adhesion was particularly sensitive to mAb 13. In contrast, mAb 16 inhibited initial cell attachment to fibronectin substrates but had no effect on attachment to either laminin or vitronectin substrates. When coated on plastic, both mAbs promoted WI38 cell spreading. However, mAb 13 (but not mAb 16) inhibited the radial outgrowth of cells from an explant on fibronectin substrates. mAb 16 also did not inhibit the motility of individual fibroblasts on fibronectin in low density culture and, in fact, substantially accelerated migration rates. In assays of the assembly of an extracellular fibronectin matrix by WI38 fibroblasts, both mAbs produced substantial inhibition in a concentration-dependent manner. The inhibition of matrix assembly resulted from impaired retention of fibronectin on the cell surface. Treatment of cells with mAb 16 also resulted in a striking redistribution of cell surface fibronectin receptors from a streak-like pattern to a relatively diffuse distribution. Concomitant morphological changes included decreases in thick microfilament bundle formation and reduced adhesive contacts of the streak-like and focal contact type. Our results indicate that the fibroblast fibronectin receptor (a) functions in initial fibroblast attachment and in certain types of adhesive contact, but not in the later steps of cell spreading; (b) is not required for fibroblast motility but instead retards migration; and (c) is critically involved in fibronectin retention and matrix assembly. These findings suggest a central role for the fibronectin receptor in regulating cell adhesion and migration.

Antibodies, Monoclonal↗
PubMed1995

Transforming growth factor-beta 1 modulates beta 1 and beta 5 integrin receptors and induces the de novo expression of the alpha v beta 6 heterodimer in normal human keratinocytes: implications for wound healing.

The molecular mechanism underlying the promotion of wound healing by TGF-beta 1 is incompletely understood. We report that TGF-beta 1 regulates the regenerative/migratory phenotype of normal human keratinocytes by modulating their integrin receptor repertoire. In growing keratinocyte colonies but not in fully stratified cultured epidermis, TGF-beta 1: (a) strongly upregulates the expression of the fibronectin receptor alpha 5 beta 1, the vitronectin receptor alpha v beta 5, and the collagen receptor alpha 2 beta 1 by differentially modulating the synthesis of their alpha and beta subunits; (b) downregulates the multifunctional alpha 3 beta 1 heterodimer; (c) induces the de novo expression and surface exposure of the alpha v beta 6 fibronectin receptor; (d) stimulates keratinocyte migration toward fibronectin and vitronectin; (e) induces a marked perturbation of the general mechanism of polarized domain sorting of both beta 1 and beta 4 dimers; and (f) causes a pericellular redistribution of alpha v beta 5. These data suggest that alpha 5 beta 1, alpha v beta 6, and alpha v beta 5, not routinely used by keratinocytes resting on an intact basement membrane, act as "emergency" receptors, and uncover at least one of the molecular mechanisms responsible for the peculiar integrin expression in healing human wounds. Indeed, TGF-beta 1 reproduces the integrin expression pattern of keratinocytes located at the injury site, particularly of cells in the migrating epithelial tongue at the leading edge of the wound. Since these keratinocytes are inhibited in their proliferative capacity, these data might account for the apparent paradox of a TGF-beta 1-dependent stimulation of epidermal wound healing associated with a growth inhibitory effect on epithelial cells.

3T3 Cells↗
PubMed2003

RPTP-alpha acts as a transducer of mechanical force on alphav/beta3-integrin-cytoskeleton linkages.

Cell motility on ECM critically depends on the cellular response to force from the matrix. We find that force-dependent reinforcement of alphav/beta3-integrin-mediated cell-matrix connections requires the receptor-like tyrosine phosphatase alpha (RPTPalpha). RPTPalpha colocalizes with alphav-integrins at the leading edge during early spreading, and coimmunoprecipitates with alphav-integrins during spreading on fibronectin and vitronectin. RPTPalpha-dependent activation of Src family kinases, in particular activation of Fyn, is required for the force-dependent formation of focal complexes and strengthening of alphav/beta3-integrin-cytoskeleton connections during the initial phase of ECM contact. These observations indicate that Src family kinases have distinct functions during adhesion site assembly, and that RPTPalpha is an early component in force-dependent signal transduction pathways leading to the assembly of focal complexes on both fibronectin and vitronectin.

Animals↗
PubMed2004

Down-regulation of plasminogen activator inhibitor 1 expression promotes myocardial neovascularization by bone marrow progenitors.

Human adult bone marrow-derived endothelial progenitors, or angioblasts, induce neovascularization of infarcted myocardium via mechanisms involving both cell surface urokinase-type plasminogen activator, and interactions between beta integrins and tissue vitronectin. Because each of these processes is regulated by plasminogen activator inhibitor (PAI)-1, we selectively down-regulated PAI-1 mRNA in the adult heart to examine the effects on postinfarct neovascularization and myocardial function. Sequence-specific catalytic DNA enzymes inhibited rat PAI-1 mRNA and protein expression in peri-infarct endothelium within 48 h of administration, and maintained down-regulation for at least 2 wk. PAI-1 inhibition enhanced vitronectin-dependent transendothelial migration of human bone marrow-derived CD34+ cells, and resulted in a striking augmentation of angioblast-dependent neovascularization. Development of large, thin-walled vessels at the peri-infarct region was accompanied by induction of proliferation and regeneration of endogenous cardiomyocytes and functional cardiac recovery. These results identify a causal relationship between elevated PAI-1 levels and poor outcome in patients with myocardial infarction through mechanisms that directly inhibit bone marrow-dependent neovascularization. Strategies that reduce myocardial PAI-1 expression appear capable of enhancing cardiac neovascularization, regeneration, and functional recovery after ischemic insult.

Adult↗
PubMed1991

Arg-Gly-Asp-containing peptides expose novel collagen receptors on fibroblasts: implications for wound healing.

Integrins are a family of cell-surface receptors intimately involved in the interactions of cells with their extracellular matrix. These receptors comprise an alpha and beta subunit in noncovalent association and many have been shown to recognize and bind an arginine-glycine-aspartate (RGD) sequence contained within their specific extracellular matrix ligand. Fibroblasts express integrin receptors belonging to two major subfamilies. Some of the members within the subfamily defined by beta 1 (VLA) are receptors for collagen but, perhaps surprisingly, the other major subfamily of integrins on fibroblasts--that defined by the alpha chain of the vitronectin receptor, alpha v--all appear to bind primarily vitronectin and/or fibronectin. In the present study we show that RGD-containing peptides expose cryptic binding sites on the alpha v-associated integrins enabling them to function as collagen receptors. The addition of RGD-containing peptides to fibroblasts cultured on type I collagen induced dramatic cell elongation and, when the cells were contained within collagen matrices, the peptides induced marked contraction of the gels. These processes were inhibited by Fab fragments of a monoclonal antibody against an alpha v integrin. Also, alpha v-associated integrins from cell lysates bound to collagen I affinity columns in the presence, but not in the absence, of RGD-containing peptides. These data suggest a novel regulatory control for integrin function. In addition, because the cryptic collagen receptors were shown to be implicated in the contraction of collagen gels, the generation of such binding forces suggests that this may be the major biological role for these integrins in processes such as wound healing.

Amino Acid Sequence↗
PubMed1993

Basic fibroblast growth factor modulates integrin expression in microvascular endothelial cells.

During angiogenesis capillary endothelial cells undergo a coordinated set of modifications in their interactions with extracellular matrix components. In this study we have investigated the effect of the prototypical angiogenic factor basic fibroblast growth factor (bFGF) on the expression and function of several integrins in microvascular endothelial cells. Immunoprecipitation experiments with antibodies to individual subunits indicated that microvascular cells express at their surface several integrins. These include the alpha 1 beta 1, alpha 2 beta 1, and alpha 3 beta 1 laminin/collagen receptors; the alpha 6 beta 1 laminin receptor; the alpha 5 beta 1 and alpha v beta 1 fibronectin receptors; the alpha 6 beta 4 basement membrane receptor; and the alpha v beta 3 and alpha v beta 5 vitronectin receptors. Treatment with bFGF caused a significant increase in the surface expression of the alpha 2 beta 1, alpha 3 beta 1, alpha 5 beta 1, alpha 6 beta 1, alpha 6 beta 4, and alpha v beta 5 integrins. In contrast, the level of expression of the alpha 1 beta 1 and alpha v beta 3 integrins was decreased in bFGF-treated cells. Immunoprecipitation of metabolically labeled cells indicated that bFGF increases the biosynthesis of the alpha 3, alpha 5, alpha 6, beta 4, and beta 5 subunits and decreases the production of the alpha v and beta 3 subunits. These results suggest that bFGF modulates integrin expression by altering the biosynthesis of individual alpha or beta subunits. In accordance with the upregulation of several integrins observed in bFGF-treated cells, these cells adhered better to fibronectin, laminin, vitronectin, and type I collagen than did untreated cells. The largest differences in beta 1 integrin expression occurred approximately 72 h after exposure to bFGF, at a time when the expression of the endothelial cell-to-cell adhesion molecule endoCAM was also significantly upregulated. In contrast, a shorter exposure to bFGF (24-48 h) was required for the maximal induction of plasminogen activator production in the same cells. Taken together, these results show that bFGF causes significant changes in the level of expression and function of several integrins in microvascular endothelial cells.

Adrenal Cortex↗
PubMed1998

Identification of osteopontin as a novel ligand for the integrin alpha8 beta1 and potential roles for this integrin-ligand interaction in kidney morphogenesis.

Epithelio-mesenchymal interactions during kidney organogenesis are disrupted in integrin alpha8 beta1-deficient mice. However, the known ligands for integrin alpha8 beta1-fibronectin, vitronectin, and tenascin-C-are not appropriately localized to mediate all alpha8 beta1 functions in the kidney. Using a method of general utility for determining the distribution of unknown integrin ligands in situ and biochemical characterization of these ligands, we identified osteopontin (OPN) as a ligand for alpha8 beta1. We have coexpressed the extracellular domains of the mouse alpha8 and beta1 integrin subunits as a soluble heterodimer with one subunit fused to alkaline phosphatase (AP) and have used the alpha8 beta1-AP chimera as a histochemical reagent on sections of mouse embryos. Ligand localization with alpha8 beta1-AP in developing bone and kidney was observed to be overlapping with the distribution of OPN. In "far Western" blots of mouse embryonic protein extracts, bands were detected with sizes corresponding to fibronectin, vitronectin, and unknown proteins, one of which was identical to the size of OPN. In a solid-phase binding assay we demonstrated that purified OPN binds specifically to alpha8 beta1-AP. Cell adhesion assays using K562 cells expressing alpha8 beta1 were used to confirm this result. Together with a recent report that anti-OPN antibodies disrupt kidney morphogenesis, our results suggest that interactions between OPN and integrin alpha8 beta1 may help regulate kidney development and other morphogenetic processes.

Alkaline Phosphatase↗
PubMed2005

Hypoxia-inducible factor regulates alphavbeta3 integrin cell surface expression.

Hypoxia-inducible factor (HIF)-deficient placentas exhibit a number of defects, including changes in cell fate adoption, lack of fetal angiogenesis, hypocellularity, and poor invasion into maternal tissue. HIF is a heterodimeric transcription factor consisting of alpha and beta aryl hydrocarbon receptor nuclear translocator or ARNT) subunits. We used undifferentiated trophoblast stem (TS) cells to characterize HIF-dependent adhesion, migration, and invasion. Arnt(-/-) and Hifalpha(-/-) TS cells exhibit reduced adhesion and migration toward vitronectin compared with wild-type cells. Furthermore, this defect is associated with decreased cell surface expression of integrin alphavbeta3 and significantly decreased expression of this integrin in focal adhesions. Because of the importance of adhesion and migration in tumor progression (in addition to placental development), we examined the affect of culturing B16F0 melanoma cells in 1.5% oxygen (O(2)). Culturing B16F0 melanoma cells at 1.5% O(2) resulted in increased alphavbeta3 integrin surface expression and increased adhesion to and migration toward vitronectin. Together, these data suggest that HIF and O(2) tension influence placental invasion and tumor migration by increasing cell surface expression of alphavbeta3 integrin.

Animals↗
PubMed1999

Interaction between collagens and glycosaminoglycans investigated using a surface plasmon resonance biosensor.

The interactions of glycosaminoglycans with collagens and other glycoproteins in extracellular matrix play important roles in cell adhesion and extracellular matrix assembly. In order to clarify the chemical bases for these interactions, glycosaminoglycan solutions were injected onto sensor surfaces on which collagens, fibronectin, laminin, and vitronectin were immobilized. Heparin bound to type V collagen, type IX collagen, fibronectin, laminin, and vitronectin; and chondroitin sulfate E bound to type II, type V, and type VII collagen. Heparin showed a higher affinity for type IX collagen than for type V collagen. On the other hand, chondroitin sulfate E showed the highest affinity for type V collagen. The binding of chondroitin sulfate E to type V collagen showed higher affinity than that of heparin to type V collagen. These data suggest that a novel characteristic sequence included in chondroitin sulfate E is involved in binding to type V collagen.

Animals↗
PubMed1995

Expression and function of fibronectin binding integrins on rat mast cells.

Adhesion molecules of the integrin family are implicated not only in leukocyte migration but also in leukocyte activation. Here we characterize the expression and function of fibronectin receptor integrins on rat mast cells. A rat basophilic leukemia cell line (RBL-2H3) and phorbol ester-stimulated rat peritoneal mast cells adhered to fibronectin (FN), vitronectin and fibrinogen. These mast cells expressed fibronectin receptor integrins, including very late antigen (VLA)-4, VLA-5 and vitronectin receptor (VNR), as estimated by immunofluorescent staining and inhibition of FN adherence by newly established mAbs reactive with the rat alpha 4 (MR alpha 4-1), alpha 5 (HM alpha 5-1) or beta 3 (HM beta 3-1) chains of the integrin molecules. The beta-hexosaminidase release, a marker for mast cell degranulation, triggered by high affinity IgE receptor (Fc epsilon RI)-mediated stimulation, was enhanced by adhesion of RBL-2H3 cells to either immobilized FN, MR alpha 4-1, HM alpha 5-1 or HM beta 3-1. This FN enhancement of beta-hexosaminidase release was inhibited by soluble MR alpha 4-1, HM alpha 5-1 and HM beta 3-1 as well as by GRGDSP and DELPQLVTLPHPNHLGPEILDVPST peptides which abrogate VLA-5/VNR and VLA-4 binding to FN respectively. In vivo, passive cutaneous anaphylaxis induced by IgE anti-DNP and DNP-BSA was inhibited by concurrent s.c. injection of MR alpha 4-1, HM alpha 5-1 and HM beta 3-1. These results demonstrate that FN receptor integrins expressed on rat mast cells play an important role in regulating mast cell activation both in vitro and in vivo.

Amino Acid Sequence↗
PubMed2004

Ptr ToxA requires multiple motifs for complete activity.

Ptr ToxA was the first proteinaceous necrosis-inducing toxin identified and cloned from the wheat pathogen, Pyrenophora tritici-repentis. How this protein causes necrosis in sensitive wheat cultivars is not known. In an effort to understand the structural features of Ptr ToxA required for induction of necrosis, we employed a combination of site-directed mutagenesis and peptide inhibition studies. Mutagenesis was carried out on conserved motifs within the active domain of Ptr ToxA. Proteins with mutations of potential casein kinase 2 phosphorylation sites but not protein kinase C phosphorylation sites have significantly reduced activity. Additionally, mutations in a region with high homology to amino acids surrounding and including the RGD cell attachment motif of vitronectin result in proteins with significantly less activity than Ptr ToxA. The importance of the vitronectin-like motif was confirmed by a decrease of Ptr ToxA-induced activity when coinfiltrated with peptides corresponding to amino acids within this motif. Reduction in Ptr ToxA activity by competition with mutant proteins demonstrates the necessity of multiple motifs for Ptr ToxA activity.

Alanine↗
PubMed1999

Differences between scar and dermal cultured fibroblasts derived from a patient with recurrent abdominal incision wound herniation.

Fibroblasts were derived from dermis and scar of a 47-year-old white man with a recurrent incisional hernia as a result of fractured ribs. The scar was thin and stretched, suggesting a defect in the maturation of granulation tissue. After surgical repair, biopsy specimens of discarded scar and skin were used to generate fibroblast cell lines. Fibroblasts maintained in medium containing 10% fetal bovine serum and antibiotic were studied between their third and eighth passage. By phase contrast microscopy, no structural differences were obvious, but it was noted that to pass scar fibroblasts, a more aggressive trypsin regimen was required. Immunohistologic and Western blot analysis of patient scar fibroblasts showed (1) more a smooth muscle actin within stress fibers, (2) increased expression of the vitronectin integrin receptor alpha(v) (CD 51), and (3) reduced expression of the collagen integrin receptor alpha2 (CD 49b). The expression of vinculin from focal adhesions or a tubulin from microtubules was the same among cell lines. Contractions of scar and dermal fibroblast-populated collagen lattice were compared. At 24 hours, contractions were 69 percent with newborn fibroblasts (normal); 68 percent for patient dermal fibroblasts; and only 48 percent for patient scar fibroblasts. The retarded contraction of scar fibroblast-populated collagen lattice was significant (p > or = 0.002). Myosin ATPase activity, critical for lattice contraction, and cell migration were equivalent among all cell lines. A plausible mechanism for the retardation of scar lattice contraction is disruption of fibroblasts and collagen interactions, for which the attachment of cells to collagen is altered. It is proposed that either the decrease in the expression of collagen integrin receptor alpha2 (CD 49b), an increase in the expression of the vitronectin receptor alpha(v) (CD 51), or a combination of both is responsible for disruption of collagen fibroblast interactions.

Actins↗
PubMed2004

Comparative analysis of extracellular matrix proteins in chronic pancreatitis: differences between pancreatic head and tail.

OBJECTIVES: In patients with chronic pancreatitis (cP) with an inflammatory mass in the pancreatic head, the degree of fibrosis in the pancreatic head compared with the tail should be determined and differences in the expression pattern of collagen types I, III, and IV; laminin; vitronectin; and fibronectin should be evaluated. METHODS: From 12 patients with alcohol-induced and idiopathic cP who underwent surgery due to local complications, 24 corresponding cP tissue samples from the pancreatic head and the resection margin were obtained. The degree of fibrosis was calculated using a computer-assisted method (Adobe Photo Shop). The expression pattern of extracellular matrix proteins (ECMPs) was investigated by immunostaining using the streptavidin-peroxidase technique. RESULTS: In each case, the degree of fibrosis was higher in the pancreatic head than in the resection margin. For alcohol-induced cP, the median degree of fibrosis in the head was 64% versus 47% in the resection margin, and for idiopathic cP, it was 40% versus 32%. Staining intensity of collagen type IV and laminin in the head was higher than in the resection surface. In degenerative tissue, collagen types I, III, and IV and laminin were moderately expressed, fibronectin was weakly expressed, and vitronectin was not expressed, with no differences between the head and resection margin. Basement membranes in the head and the resection margin predominantly consisted of collagen types I, III, and IV and laminin. In ductal epithelia, collagen type IV staining in the head was stronger than in the resection margin. CONCLUSIONS: In cP with an inflammatory mass in the head, the degree of fibrosis in the pancreatic head is higher than in the resection margin. Differences in the expression pattern of ECMPs could be detected for collagen type IV and laminin. These results underline the hypothesis of the pancreatic head being the pacemaker of cP in which collagen type IV and laminin may play an important role.

Adult↗
PubMed2004

Plasminogen activator inhibitor type 1: the two faces of the same coin.

PURPOSE OF REVIEW: Plasminogen activator inhibitor type 1 is the primary inhibitor of plasminogen activators. It is often bound to vitronectin, an abundant component of extracellular matrix in many tissues. The aim of this review is to discuss the contradictory results reported concerning the impact of plasminogen activator inhibitor type 1 expression in the kidney and in the vessel wall during pathological conditions. RECENT FINDINGS: First described as a 'bad guy' promoting the persistence of fibrin deposition and the evolution towards organ fibrosis, plasminogen activator inhibitor type 1 was recently reported to serve an unexpected protective role during fibrin-dependent diseases, such as experimental glomerulonephritis, and during aortic atherosclerosis. SUMMARY: Plasminogen activator inhibitor type 1 is not only an inhibitor of plasmin generation. Recent data suggest that plasminogen activator inhibitor type 1 is required for the regulation of plasminogen activator-dependent, plasmin-independent processes, and that its expression in vivo critically modulates inflammation, potentially by its capacity to occupy vitronectin binding sites.

Animals↗