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PubMed1997

Interactions between germ cells and extracellular matrix glycoproteins during migration and gonad assembly in the mouse embryo.

Cells are known to bind to individual extracellular matrix glycoproteins in a complex and poorly understood way. Overall strength of adhesion is thought to be mediated by a combinatorial mechanism, involving adhesion of a cell to a variety of binding sites on the target glycoproteins. During migration in embryos, cells must alter their overall adhesiveness to the substrate to allow locomotion. The mechanism by which this is accomplished is not well understood. During early development, the cells destined to form the gametes, the primordial germ cells (PGCs), migrate from the developing hind gut to the site where the gonad will form. We have used whole-mount immunocytochemistry to study the changing distribution of three extracellular matrix glycoproteins, collagen IV, fibronectin, and laminin, during PGC migration and correlated this with quantitative assays of adhesiveness of PGCs to each of these. We show that PGCs change their strength of adhesion to each glycoprotein differentially during these stages. Furthermore, we show that PGCs interact with a discrete tract of laminin at the end of migration. Closer analysis of the adhesion of PGCs to laminin revealed that PGCs adhere particularly strongly to the E3 domain of laminin, and blocking experiments in vitro suggest that they adhere to this domain using a cell surface proteoglycan.

Animals↗

PubMed1998

Recombinant latent transforming growth factor beta-binding protein 2 assembles to fibroblast extracellular matrix and is susceptible to proteolytic processing and release.

Latent transforming growth factor beta-binding protein 2 (LTBP-2) belongs to the fibrillin-LTBP gene family and is a component of 10-nm microfibrils. LTBP-2 consists mainly of domains of 8-cysteine and EGF-like repeats linked by proline-rich regions. To characterize the biochemical properties of LTBP-2, its assembly to the extracellular matrix, and its proteolytic release from the matrix, LTBP-2 was expressed recombinantly in Chinese hamster ovary cells and purified to homogeneity under nondenaturing conditions. Purified LTBP-2 bound calcium and was glycosylated at the central domain of EGF-like repeats. Antibodies made against the recombinant LTBP-2 decorated fibrillar structures in fibroblast extracellular matrix. Treatment of matrices with plasmin or elastase released a soluble approximately 160-kDa LTBP-2 fragment. Processing of LTBP-2 was studied by treating purified LTBP-2 with plasmin or porcine pancreatic elastase. LTBP-2 was processed with these proteases initially to a approximately 160-kDa fragment, and with higher concentrations to a protease-resistant approximately 120-kDa fragment. Processing sites were localized by amino acid sequencing to proline-rich regions at the N-terminal part of LTBP-2, suggesting that the matrix binding sites locate to the N-terminal approximately 500 amino acids of LTBP-2. Purified and biotinylated LTBP-2 could be assembled to fibrillar structures in fibroblast extracellular matrix during cell cultivation, indicating that LTBP-2 assembly to the matrix is not strictly linked to cells that make it and suggesting that microfibril assembly may involve soluble intermediates.

Adaptor Proteins, Signal Transducing↗

PubMed2003

Presentation of galectin-1 by extracellular matrix triggers T cell death.

Apoptotic elimination of T cells at sites of inflammation or infiltration into tumors limits an effective immune response. T cell apoptosis can be initiated by a variety of triggers, including galectin-1, a soluble, secreted lectin that binds to oligosaccharide ligands on cell surface glycoproteins, or to oligosaccharide ligands on extracellular matrix glycoproteins in tissue stroma. Although galectin-1 has no transmembrane domain and is secreted from cells that make it, it is not clear if galectin-1 functions as a soluble death trigger in vivo. We examined the ability of stromal cells secreting galectin-1 to kill T cells. Although the stromal cells synthesized abundant galectin-1, the majority of the galectin-1 remained bound to the cell surface, and stromal cell-associated galectin-1 killed bound T cells. In contrast, insufficient amounts of functional galectin-1 were released from the stromal cells into the media to kill T cells in the absence of contact with stromal cells. However, when stromal cells were grown on Matrigel, a mixture of extracellular matrix proteins, or on permeable membranes above Matrigel, secreted galectin-1 bound to Matrigel and killed T cells without stromal cell contact. Ten-fold less galectin-1 on Matrigel was sufficient to kill adherent T cells compared with soluble galectin-1. These results demonstrate that galectin-1 in extracellular matrix is able to directly kill susceptible T cells. Because increased galectin-1 deposition in tumor stroma occurs with tumor progression in various types of cancer, galectin-1 in stroma may act locally in the apoptotic elimination of infiltrating T cells during an immune response.

Animals↗

PubMed1994

Triflavin, an antiplatelet peptide, inhibits tumor cell-extracellular matrix adhesion through an arginine-glycine-aspartic acid-dependent mechanism.

The interaction of tumor cells with extracellular matrix components such as laminin, fibronectin, and collagen has been shown to be mediated through a family of cell-surface receptors that specifically recognize an arginine-glycine-aspartic acid amino acid sequence within each protein. Triflavin, a 7.5 kDa cysteine-rich polypeptide purified from Trimeresurus flavoviridis snake venom, belongs to a family of arginine-glycine-aspartic acid-containing peptides termed disintegrins that have been isolated from the venoms of various vipers and shown to be potent inhibitors of platelet aggregation. In this study, we showed that triflavin inhibited adhesion of human hepatoma J-5 cells to extracellular matrices (fibronectin, vitronectin, fibrinogen, and collagen type I) in a dose-dependent manner. On the other hand, triflavin exerted a limited inhibitory effect on cell attachment to collagen type IV and laminin (< or = 40%). Triflavin is approximately 1000 times more potent than glycine-arginine-glycine-aspartic acid-serine at inhibiting cell adhesion. When immobilized on plate, triflavin promoted J-5 cell attachment; this attachment was inhibited by glycine-arginine-glycine-aspartic acid-serine. In addition, triflavin labeled with iodine 125 binds to J-5 cells in a saturable manner and its binding was also inhibited by glycine-arginine-glycine-aspartic acid-serine. Its Kd value was estimated to be 3.9 x 10(-7) mol/L and the number of binding sites was around 60,000 per cell. Furthermore, triflavin did not affect tritiated thymidine uptake during a 3-day incubation.(ABSTRACT TRUNCATED AT 250 WORDS)

Binding Sites↗

PubMed1998

Effect of alignment of the transplanted graft extracellular matrix on cellular repopulation and newly synthesized collagen.

This study examines the effect of alignment of the transplanted graft extracellular matrix on cellular repopulation and new collagen synthesis. The lateral half of the patellar tendon was harvested as a tendon graft from Lewis rats and frozen at -80 degrees C. In order to maintain the original alignment of the graft extracellular matrix, the graft was transplanted to a same size defect in the patellar tendon of other Lewis rats (group I). For controls, the graft was transplanted in a lax condition after excision of only the distal half of the lateral side of a patellar tendon (group II). After transplantation, six animals in each group were killed at 3, 7, 14, and 28 days. Cellular repopulation was assessed by using fibrillar-actin (F-actin) labeling with rhodamine-phalloidin, and new collagen synthesis was detected by means of a polyclonal antibody against type III collagen aminopropeptide (pN collagen III). Collagen fibril profiles were observed under the transmission electron microscope. On the 3rd day after transplantation, no specific fluorescence was detected in either group. Specific labeling for F-actin and pN collagen III, however, was observed at both ends of the graft in both groups at 1 week and throughout the graft at 2 weeks after transplantation. Consistent with the actin bundles' orientation, pN collagen III was aligned parallel to the longitudinal axis of the graft in group I. Collagen fibrils with a smaller diameter, mixed evenly and everywhere with a larger diameter, increased gradually in group I. However, smaller collagen fibrils in group II increased more slowly and were distributed unevenly. In summary, the dense collagen arrangement in the native patellar tendon determined the alignment of the repopulating cells, and the distribution of newly synthesized collagen might be affected by the actin cytoskeleton within the repopulating cells.

Actins↗

PubMed1992

Chondrocytes in agarose culture synthesize a mechanically functional extracellular matrix.

The ability of chondrocytes from calf articular cartilage to synthesize and assemble a mechanically functional cartilage-like extracellular matrix was quantified in high cell density (approximately 10(7) cells/ml) agarose gel culture. The time evolution of chondrocyte proliferation, proteoglycan synthesis and loss to the media, and total deposition of glycosaminoglycan (GAG)-containing matrix within agarose gels was characterized during 10 weeks in culture. To assess whether the matrix deposited within the agarose gel was mechanically and electromechanically functional, we measured in parallel cultures the time evolution of dynamic mechanical stiffness and oscillatory streaming potential in uniaxial confined compression, and determined the intrinsic equilibrium modulus, hydraulic permeability, and electrokinetic coupling coefficient of the developing cultures. Biosynthetic rates were initially high, but by 1 month had fallen to a level similar to that found in the parent calf articular cartilage from which the cells were extracted. The majority of the newly synthesized proteoglycans remained in the gel. Histological sections showed matrix rich in proteoglycans and collagen fibrils developing around individual cells. The equilibrium modulus, dynamic stiffness, and oscillatory streaming potential rose to many times (>5x) their initial values at the start of the culture; the hydraulic permeability decreased to a fraction (approximately 1/10) that of the cell-laden porous agarose at the beginning of the culture. By day 35 of culture, DNA concentration (cell density), GAG concentration, stiffness, and streaming potential were all approximately 25% that of calf articular cartilage. The frequency dependence of the dynamic stiffness and potential was similar to that of calf articular cartilage. Together, these results suggested the formation of a mechanically functional matrix.

Animals↗

PubMed1993

The extracellular matrix proteins laminin and fibronectin contain binding domains for human plasminogen and tissue plasminogen activator.

This study describes the binding of plasminogen and tissue-type plasminogen activator (t-PA) to the extracellular matrix proteins fibronectin and laminin. Plasminogen bound specifically and saturably to both fibronectin and laminin immobilized on microtiter wells, with Kd(app) values of 115 and 18 nM, respectively. Limited proteolysis by endoproteinase V8 coupled with ligand blotting analysis showed that both plasminogen and t-PA preferentially bind to a 55-kDa fibronectin fragment and a 38-kDa laminin fragment. Amino acid sequence analysis demonstrated that the 5-kDa fragment originates with the fibronectin amino terminus whereas the laminin fragment was derived from the carboxyl-terminal globular domain of the laminin A chain. Ligand blotting experiments using isolated plasminogen domains were also used to identify distinct regions of the plasminogen molecule involved in fibronectin and laminin binding. Solution phase fibronectin binding to immobilized plasminogen was mediated primarily via lysine binding site-dependent interactions with plasminogen kringles 1-4. Lysine binding site-dependent binding of soluble laminin to immobilized plasminogen kringles 1-5 as well as an additional lysine binding site-independent interaction between mini-plasminogen and the 38-kDa laminin A chain fragment were also observed. These studies demonstrate binding of plasminogen and tissue-type plasminogen activator to specific regions of the extracellular matrix glycoproteins laminin and fibronectin and provide further insight into the mechanism of regulation of plasminogen activation by components of the extracellular matrix.

Amino Acid Sequence↗

PubMed1998

Influence of extracellular matrix proteins on membrane potentials and excitability in NG108-15 cells.

Previous studies have demonstrated that components of the extracellular matrix can induce neurite extension and cell adhesion in the neuroblastoma x glioma hybrid cell line, NG108-15. Using standard intracellular recording techniques, we examined the resting membrane potential (RMP) and membrane excitability of NG108-15 cells differentiated under serum-free media with representative extracellular matrix (ECM) protein components as the substrate. Surfaces coated with collagen IV and a laminin-1 synthetic peptide induced a significantly (P < 0.05) more hyperpolarized RMP than control polystyrene surfaces. For example, after > or =8 days in culture NG108-15 cells plated on polystyrene exhibited a RMP of -33.2+/-0.8 mV (mean+/-SEM, n=158 cells) whereas cells cultured on the laminin-1 peptide C16 and collagen IV showed a RMP of -37.6+/-0.7 mV (n=157) and -37.5+/-1.5 mV (n=68), respectively. Furthermore, the proportions of cells on ECM substrates showing membrane excitability, i.e. evoked action potentials (APs) and the capability for regular firing, were significantly greater compared to those cells cultured on polystyrene. Among excitable cells cultured on the different substrates, characteristics of the action potentials, such as AP duration, amplitude, and the maximum rate of rise, dV/dtMAX, were examined in detail. While little or no differences were observed between polystyrene and the laminin-1 peptide groups, significant differences in the AP parameters were apparent for collagen IV. For example, dV/dtMAX for polystyrene and the laminin-1 peptide C16 were only 71.7+/-24.5 V/s (n=11) and 59.0+/-8.9 V/s (n=9), respectively, whereas cells cultured on collagen IV surfaces exhibited a dV/dtMAX reaching 156.1+/-22.0 V/s (n=7). These data support a role for ECM components in the maintenance of the RMP and membrane excitability in NG108-15 cells.

Action Potentials↗

PubMed1992

Distribution patterns of extracellular matrix components and adhesion receptors are intricately modulated during first trimester cytotrophoblast differentiation along the invasive pathway, in vivo.

Development of the human embryo depends on the ability of first trimester cytotrophoblastic stem cells to differentiate and invade the uterus. In this process, transient expression of an invasive phenotype is part of normal cytotrophoblast differentiation. Morphologically, this process begins when polarized chorionic villus cytotrophoblasts form multilayered columns of nonpolarized cells, and invade the uterus. Using immunocytochemistry, we compared the presence of adhesion receptors and extracellular matrix ligands on cytotrophoblasts in villi, cell columns, and the uterine wall. Villus cytotrophoblasts, anchored to basement membrane, stained for alpha 6 and beta 4 integrin subunits and both merosin and A-chain-containing laminin. Nonpolarized cytotrophoblasts in columns expressed primarily alpha 5 and beta 1 integrin subunits and a fibronectin-rich matrix. Cytotrophoblast clusters in the uterine wall stained for alpha 1, alpha 5, and beta 1 integrins, but not for most extracellular matrix antigens, suggesting that they interact primarily with maternal cells and matrices. Tenascin staining was restricted to stroma at sites of transition in cytotrophoblast morphology, suggesting that tenascin influences cytotrophoblast differentiation. Our results suggest that regulation of adhesion molecule expression contributes to acquisition of an invasive phenotype by cytotrophoblasts and provide a foundation for studying pathological conditions in which insufficient or excessive trophoblast invasion occurs, such as preeclampsia or choriocarcinoma.

Basement Membrane↗

PubMed1993

Extracellular matrix components induce endocrine differentiation in vitro in NCI-H716 cells.

Endocrine cells occur in +/- 30% of colorectal adenocarcinomas. The significance of this phenomenon in terms of tumor behavior is still controversial. Endocrine differentiation in colorectal cancer cell lines is almost confined to tumor xenografts in vivo, suggesting that endocrine differentiation might be regulated by epithelial-stromal interactions. This hypothesis was studied in the cecal adenocarcinoma-derived cell line NCI-H716 by comparing the expression of chromogranin A protein and messenger RNA in vivo and in vitro and by attempts to induce differentiation in vitro. We found that chromogranin A expression, which was strongest in vivo, could be significantly enhanced in vitro by culturing tumor cells in the presence of native extracellular matrix, on fibroblast feeder layers, and in a defined medium with basic fibroblast growth factor. The results suggest that the extracellular matrix induces endocrine differentiation through factors (e.g., basic fibroblast-growth factor) that may be produced by stromal cells and after secretion bind to the extracellular matrix.

Adenocarcinoma↗

PubMed1992

Adhesion of T and B lymphocytes to extracellular matrix and endothelial cells can be regulated through the beta subunit of VLA.

Investigating the regulation of very late antigen (VLA)-mediated functions, we found that TS2/16, a mAb directed against the beta chain of the VLA group of integrins, can induce binding of resting peripheral blood lymphocytes, cloned T lymphocytes, and Epstein Barr virus-transformed B cells to extracellular matrix components, fibronectin, laminin, and collagen, but not to fibrinogen. The antibody stimulates VLA-4-, VLA-5-, and VLA-6-mediated binding. Furthermore, it induces VLA-4-mediated binding to vascular cell adhesion molecule-1 expressed by rTNF-alpha-stimulated endothelial cells, but it does not stimulate homotypic aggregation of cells as described for a number of anti-VLA-4 alpha antibodies (Bednarczyk, J.L., and B. W. McIntyre. 1990. J. Immunol. 144: 777-784; Campanero, M. R., R. Pulido, M. A. Ursa, M. Rodríguez-Moya, M. O. de Landázuri, and F. Sánchez-Madrid. 1990. J. Cell Biol. 110:2157-2165). Therefore, the stimulating activity of this anti-beta 1 antibody clearly contrasts with that of the anti-VLA-4 alpha antibodies, which induce homotypic cell aggregation, but not binding of cells to extracellular matrix components or endothelial cells, indicating that TS2/16 may generate different signals. The observation that also F(ab')2 or Fab fragments of this anti-beta 1 antibody stimulate binding to extracellular matrix components and endothelial cells excludes the possibility that binding requires receptor crosslinking, or is Fc receptor mediated. Induction of this adhesion is cation and energy dependent and requires an intact cytoskeleton. Although changes in the conformation of VLA integrins induced by this antibody may regulate their functional activity, the dependence on metabolic energy indicates that intracellular processes may also play a role.

Antibodies, Monoclonal↗

PubMed1996

[Cellular adhesion molecules and components of the extracellular matrix as target structures of autoimmunity].

Cell-cell and cell-matrix adhesion molecules as well as extracellular matrix components are target structures of antibody-mediated autoimmunity that have recently been well characterized at the molecular biological level. Pathogenic autoantibodies against these molecules are causally related to disturbances of cell and tissue adhesion that become apparent as various (muco-)cutaneous blistering diseases. Desmosomal cadherins (desmogleins and desmocollins) mediate epidermal intercellular adhesion. Among these, desmoglein 1 and desmoglein 3 are the autoantigens of pemphigus foliaceus and pemphigus vulgaris, respectively, exhibiting intraepidermal blistering. The pathogenic relevance of autoantibodies against desmocollins. (IgA pemphigus) and desmoplakins (paraneoplastic pemphigus) still remains unclear. Hemidesmosomes contain the plaque protein BPAG1 and the partly collagen-like transmembrane protein BPAG2, representing the autoantigens of bullous pemphigoid and pemphigoid gestationis with subepidermal blistering. A certain subtype of cicatricial (benign mucous membrane) pemphigoid is characterized by autoantibodies against laminin 5 present in the subhemidesmosomal anchoring filaments, while epidermolysis bullosa acquisita and bullous SLE exhibit autoantibodies against collagen type VII constituting the anchoring fibrils. In addition, autoantibodies against a particular collagen type IV chain of the glomerular basement membrane are responsible for the manifestation of Goodpasture's syndrome. These recent molecular biological findings might be the basis for the development of novel therapeutic strategies.

Autoantibodies↗

PubMed1993

Sulfated proteoglycans in the extracellular matrix of human breast tissues with infiltrating carcinoma.

The size, content and distribution of sulfated proteoglycans, constituents of the extracellular matrix, were investigated in non-neoplastic human breast tissues and in tissues with infiltrating carcinoma. Sulfated proteoglycans were identified as cuprolinic-blue-positive elements on electron microscopy preparations by the method of the critical electrolyte concentration. Morphometric data indicated that the numerical density of PG per surface area (NA) in normal tissues was about 2 to 7 times higher respectively in dense or loose connective zone then that found in the corresponding zones of malignant tissues. By referring to the unit volume of tissue, the overall PG content (Nv) was found to be increased about 5 fold in nonneoplastic tissues. However, in tissues with carcinoma the average length of sulfated proteoglycans was about twice as long in dense and loose connective layers than in the corresponding connective zones of non-neoplastic breast tissues. Our findings provide evidence of profound structural alterations of non-collagenous constituents in the extracellular matrix of human mammary tissues concerned with infiltrating carcinoma.

Adult↗

PubMed1990

[Proteolytic potential of fibronectin and degradation of extracellular matrix].

Fibronectin is one of the major adhesive glycoproteins and bears interaction sites for both cell receptors and the extracellular matrix. Disappearance of fibronectin is the first step of cellular transformation in carcinogenesis. This phenomenon has been ascribed to increased proteolysis of fibronectin or of its cellular receptor. Results obtained during previous studies by the authors have shown that the fibronectin molecule has latent proteolytic activities which become apparent only after the action of other external proteases. Two proteinases, FN-gelatinase and FN-laminase, were identified in cathepsin D fibronectin digest. The acute activity of these two proteases is responsible for degradation of the extracellular matrix. Furthermore, the sequences and functions of both enzymes share a number of features with retroviral proteases.

Amino Acid Sequence↗

PubMed1990

Ultrastructural localization of the major components of the extracellular matrix in normal mouse liver.

We have investigated the extracellular and intracellular distribution of the major components of the hepatic extracellular matrix: types I and IV collagen (CI and CIV), type III procollagen (PCIII), fibronectin (FN) and laminin (LM) in the normal mouse liver by electron microscopy, using the indirect immunoperoxidase method. Extracellular localization of CI and PCIII revealed the typical collagen fibrils and small bundles in portal tracts and Disse's space. Faint extracellular deposition of CIV was detectable in basement membranes of portal structures and as discontinuous precipitates in Disse's space. FN strongly reacted in Disse's space and formed a continuous layer as well as strands between hepatocytes and endothelial cells. Moderate LM reaction was seen along the sinusoids in discrete spots and in basement membranes surrounding bile ducts and blood vessels. The cellular source of these components was demonstrated to be of mixed origin. Hepatocytes synthesized very little CI and large amounts of FN. Additionally, CI was produced by periportal fibroblasts. Fat-storing cells clearly participated in the production of PCIII, CIV and LM. LM synthesis was also found in bile duct cells and the cells of Hering's canal.

Animals↗

PubMed2003

Trypanosoma cruzi infection: a continuous invader-host cell cross talk with participation of extracellular matrix and adhesion and chemoattractant molecules.

Several lines of evidence have shown that Trypanosoma cruzi interacts with host extracellular matrix (ECM) components producing breakdown products that play an important role in parasite mobilization and infectivity. Parasite-released antigens also modulate ECM expression that could participate in cell-cell and/or cell-parasite interactions. Increased expression of ECM components has been described in the cardiac tissue of chronic chagasic patients and diverse target tissues including heart, thymus, central nervous system and skeletal muscle of experimentally T. cruzi-infected mice. ECM components may adsorb parasite antigens and cytokines that could contribute to the establishment and perpetuation of inflammation. Furthermore, T. cruzi-infected mammalian cells produce cytokines and chemokines that not only participate in the control of parasitism but also contribute to the establishment of chronic inflammatory lesions in several target tissues and most frequently lead to severe myocarditis. T. cruzi-driven cytokines and chemokines may also modulate VCAM-1 and ICAM-1 adhesion molecules on endothelial cells of target tissues and play a key role in cell recruitment, especially of activated VLA-4+LFA-1+CD8+ T lymphocytes, resulting in a predominance of this cell population in the inflamed heart, central nervous system and skeletal muscle. The VLA-4+-invading cells are surrounded by a fine network of fibronectin that could contribute to cell anchorage, activation and effector functions. Since persistent "danger signals" triggered by the parasite and its antigens are required for the establishment of inflammation and ECM alterations, therapeutic interventions that control parasitism and selectively modulate cell migration improve ECM abnormalities, paving the way for the development of new therapeutic strategies improving the prognosis of T. cruzi-infected individuals.

Animals↗

PubMed2002

Extracellular matrix and matrix metalloproteinase changes in human corneas after complicated laser-assisted in situ keratomileusis (LASIK).

PURPOSE: To characterize extracellular matrix (ECM) and nine matrix metalloproteinase (MMP) changes in two corneas that underwent a complicated laser-assisted in situ keratomileusis (LASIK) procedure. METHODS: The first patient underwent bilateral LASIK. The flap on the left eye was transected in several locations and placed back. This cornea later developed edema, and the removed flap was analyzed after lamellar keratoplasty. The second patient had a LASIK flap lifted, replaced twice, and then completely removed. The epithelium grew over the stroma, but haze and severe ectasia occurred. After penetrating keratoplasty, the recipient cornea was analyzed. An autopsy cornea from a person who underwent uneventful LASIK and ten normal autopsy corneas served as controls. Corneas were analyzed by immunohistochemistry. RESULTS: Both flap regions in the treated corneas had marked alterations of ECM components and MMPs. Stromal deposits of various ECM proteins, including those normally absent in the central cornea (tenascin-C, fibrillin-1, type XIV collagen), were found. Rare myofibroblasts and inflammatory cells were present. The epithelial basement membrane (BM) was altered in both cases. The most dramatic change was poor or no staining for alpha3-alpha6 type IV collagen chains and thrombospondin. The limbal alpha1-alpha2 type IV collagen and laminin-2 (alpha2beta1gamma1) appeared in the central epithelial BM. Other components were altered to a lesser extent. The anterior stroma was positive for MMP-1 and MMP-2, and some MMP-7 was seen in the epithelium. These ECM and MMP patterns were not seen in uneventful LASIK or normal corneas. CONCLUSIONS: In the flaps of LASIK-treated corneas, fibrosed areas of anterior stroma had increased levels of MMP-1 and MMP-2 that may have caused loss of specific type IV collagen isoforms in the epithelial BM. These changes may reflect an ongoing wound healing process and contribute to the development of ectasia.

Adult↗

PubMed1997

Degradation of human subendothelial extracellular matrix by proteinase-secreting Candida albicans.

Candida albicans infections in severely immunocompromized patients are not confined to mucosal surfaces; instead the fungus can invade through epithelial and endothelial layers into the bloodstream and spread to other organs, causing disseminated infections with often fatal outcome. We investigated whether secretion of the C. albicans acid proteinase facilitates invasion into deeper tissues by degrading the subendothelial basement membrane. After cultivation under conditions that induce the secretion of the acid proteinase, C. albicans degraded radioactively metabolically labeled extracellular matrix proteins from a human endothelial cell line. The degradation was inhibited in the presence of pepstatin A, an inhibitor of acid proteinases. Pepstatin A-sensitive degradation of the soluble and immobilized extracellular matrix proteins fibronectin and laminin by proteinase-producing C. albicans was also detected, whereas no degradation was observed when the expression of the acid proteinase was repressed. Our results demonstrate that the C. albicans acid proteinase degrades human subendothelial extracellular matrix; this may be of importance in the penetration of C. albicans into circulation and deep organs.

Aspartic Acid Endopeptidases↗