Signal transduction through the fibronectin receptor induces collagenase and stromelysin gene expression

Specific fibronectin fragments as markers of periodontal disease status

BACKGROUND

The diagnosis of progressing periodontal disease typically relies on retrospective methods that detect changes in the amount of periodontal breakdown. Fibronectin (FN) fragments are found in vivo in association with periodontal disease, and specific FN fragments compromise periodontal ligament cell functions in vitro. The overall goal of this cross-sectional study was to determine whether specific FN fragments are present in gingival crevicular fluid (GCF) and can be used as markers for periodontal disease status. The eventual goal is to test these FN fragments in a longitudinal study as potential markers of disease activity.

METHODS

GCF was collected from 94 subjects with untreated periodontitis from clinically healthy, mild/moderate periodontitis, and severe periodontitis sites. Sites were defined on the basis of clinical criteria, including gingival bleeding index, probing depth, and clinical attachment level. Western immunoblotting was used to detect FN fragments in GCF using antibodies to specific FN domains, including the collagen/gelatin-, central cell-, and carboxyl terminal heparin-binding domains, plus the CS-1 site on the alternatively spliced V region and the EIIIA region. FN fragments identified by immunoblotting and analyzed by NIH image software were scored based on pixel intensity and an ordinal grade scale.

RESULTS

We identified several fragments highly associated with severe periodontitis sites, including 40-kDa, 120-kDa, and 68-kDa fragments.

CONCLUSIONS

This study demonstrates that specific FN fragments are markers for periodontal disease status and supports the role of FN fragments as potential components in the pathogenesis of periodontal disease.

Fibronectin fragments and blocking antibodies to alpha2beta1 and alpha5beta1 integrins stimulate mitogen-activated protein kinase signaling and increase collagenase 3 (matrix metalloproteinase 13) production by human articular chondrocytes

OBJECTIVE

To determine if integrin-mediated signaling results in activation of chondrocyte mitogen-activated protein (MAP) kinases that lead to increased expression of matrix metalloproteinase 13 (MMP-13; collagenase 3), a potent mediator of cartilage matrix degradation.

METHODS

Human articular chondrocytes isolated from normal ankle and knee cartilage obtained from tissue donors were cultured in monolayers. The cells were treated with a 120-kd fibronectin fragment (FN-f) that binds the alpha5beta1 integrin or with antibodies to specific integrin receptors. Activation of MAP kinases was determined by immunoblotting with phosphospecific antibodies. MMP production was measured by gelatin zymography, and MMP-13 production and activation were determined by immunoblotting and by a fluorogenic peptide assay.

RESULTS

Human articular chondrocytes were found to respond to the 120-kd FN-f and to adhesion-blocking antibodies to the alpha2beta1 and alpha5beta1 integrins with increased phosphorylation of the extracellular signal-regulated kinase 1 (ERK1)/ERK2, c-Jun N-terminal kinase (JNK), and p38 MAP kinases. Intact FN and integrin-blocking antibodies to alpha1, alpha3, and alphaVbeta3 and a nonblocking alpha5 antibody had no effect. After MAP kinase activation, increased phosphorylation of c-Jun and the nuclear factor kappaB inhibitor was noted, followed by increased pro- and activated MMP-13 in the conditioned media. Inhibitors of mitogen-activated protein kinase kinase, p38, and JNK were each able to inhibit increased MMP-13 production, while the interleukin-1 receptor antagonist (IL-1Ra) protein did not. However, the IL-1Ra partially inhibited FN-f-induced activation of MMP-13.

CONCLUSION

Integrin-mediated MAP kinase signaling stimulated by FN-f is associated with increased production and release of pro- and active MMP-13. Autocrine production of IL-1 appears to result in additional MMP-13 activation. These processes may play a key role in feedback loops responsible for progressive cartilage degradation in arthritis.

Molecular determinants of metalloproteinase substrate specificity: matrix metalloproteinase substrate binding domains, modules, and exosites

The function of ancillary domains and modules attatched to the catalytic domain of mutidomain proteases, such as the matrix metalloproteinases (MMPs), are not well understood. The importance of discrete MMP substrate binding sites termed exosites on domains located outside the catalytic domain was first demonstrated for native collagenolysis. The essential role of hemopexin carboxyl-domain exosites in the cleavage of noncollagenous substrates such as chemokines has also been recently revealed. This article updates a previous review of the role of substrate recognition by MMP exosites in both preparing complex substrates, such as collagen, for cleavage and for tethering noncollagenous substrates to MMPs for more efficient proteolysis. Exosite domain interaction and movements--"molecular tectonics"--that are required for native collagen triple helicase activity are discussed. The potential role of collagen binding in regulating MMP-2 (gelatinase A) activation at the cell surface reveals unexpected consequences of substrate interactions that can lead to collagen cleavage and regulation of the activation and activity of downstream proteinases necessary to complete the collagenolytic cascade.

Proximal tubular epithelial cell integrins respond to high glucose by altered cell-matrix interactions and differentially regulate matrixin expression

Thickening of the tubular basement membrane (TBM) occurs in diabetic nephropathy, but the effects of high glucose on the functional aspects of proximal tubular epithelial cells are not clearly understood. In the present study, we examined the effects of elevated glucose concentrations on (a) integrin expression by human proximal tubular epithelial cells (HK-2) and integrin-mediated interactions with type IV collagen (colIV) and laminin, major components of TBM; (b) the expression of matrixins/matrix metalloproteinases (MMPs), which is regulated by integrins; and (c) the expression of tissue inhibitors of metalloproteinases (TIMPs). HK-2 cells cultured in 25 mM glucose underwent a reduction of the expression of alpha3, beta1, alpha(v)beta3, and alpha5 integrin subunits, with a concomitant increase of the alpha2 subunit, compared with cells grown in 5 mM glucose. Adhesion experiments demonstrated that high glucose led to increased cell adhesion on either colIV or laminin. Experiments of competition of adhesion using anti-integrin antibodies indicated that HK-2 cells in 5 mM glucose used mainly alpha(v)beta3 and alpha5beta1 integrins to adhere to colIV, whereas in 25 mM glucose they additionally used alpha2beta1. In the case of laminin, a beta1-mediated adhesion was observed when HK-2 cells were in 5 mM glucose, whereas in 25 mM glucose, alpha2beta1 and alpha(v)beta3 were also involved. Elevated glucose concentrations resulted in decreased expression of MMP-9 and MMP-2, whereas an increase in TIMP-1 and a decrease in TIMP-2 expression were observed. We also examined which integrins mediated the expression and secretion of matrixins MMP-2 and MMP-9. Ligation of alpha3beta1 with mAbs resulted in induction of MMP-2 expression and secretion, whereas antibody ligation of alpha(v)beta3 led to down-regulation of MMP-9. The above data implicate integrins of proximal tubular epithelial cells in the regulation of MMPs and in the development of TBM thickening in diabetic nephropathy.

Matrix metalloproteinase-1 activates a pertussis toxin-sensitive signaling pathway that stimulates the release of matrix metalloproteinase-9

The matrix metalloproteinases (MMPs) are a family of structurally related metalloendopeptidases so named due to their propensity to target extracellular matrix (ECM) proteins. Accumulating evidence, however, suggests that these proteases cleave numerous non-ECM substrates including enzymes and cell surface receptors. MMPs may also bind to cell surface receptors, though such binding has typically been thought to mediate internalization and degradation of the bound protease. More recently, it has been shown that MMP-1 coimmunoprecipitates with the alpha2beta1 integrin, a receptor for collagen. This association may serve to localize the enzymatic activity of MMP-1 so that collagen is cleaved and cell migration is facilitated. In other studies, however, it has been shown that integrin engagement may be linked to the activation of signaling cascades including those mediated by Gialpha containing heterotrimers. As an example, alpha2beta1 can form a complex with CD47 that may associate with Gialpha. In the present study we have therefore investigated the possibility that MMP-1 may affect intracellular changes that are linked to the activation of a Gi protein-coupled receptor. We show that treatment of neural cells with MMP-1 is followed by a rapid reduction in cytosolic levels of cAMP. Moreover, MMP-1 potentiates proteinase activated receptor-1 (PAR-1) agonist-linked increases in intracellular calcium, an effect which is often observed when an agonist of a Gi protein-coupled receptor is administered in association with an agonist of a Gq coupled receptor. In addition, MMP-1 stimulates pertussis toxin sensitive release ofMMP-9 both from cultured neural cells and monocyte/macrophages. Together, these results suggest that MMP-1 signals through a pertussis toxin-sensitive G protein-coupled receptor.

Modeling extracellular matrix degradation balance with proteinase/transglutaminase cycle

Extracellular matrix mass balance is implied in many physiological and pathological events, such as metastasis dissemination. Widely studied, its destructive part is mainly catalysed by extracellular proteinases. Conversely, the properties of the constructive part are less obvious, cellular neo-synthesis being usually considered as its only element. In this paper, we introduce the action of transglutaminase in a mathematical model for extracellular matrix remodeling. This extracellular enzyme, catalysing intermolecular protein cross-linking, is considered here as a reverse proteinase as far as the extracellular matrix physical state is concerned. The model is based on a proteinase/transglutaminase cycle interconverting insoluble matrix and soluble proteolysis fragments, with regulation of cellular proteinase expression by the fragments. Under "closed" (batch) conditions, i.e. neglecting matrix influx and fragment efflux from the system, the model is bistable, with reversible hysteresis. Extracellular matrix proteins concentration abruptly switches from low to high levels when transglutaminase activity exceeds a threshold value. Proteinase concentration usually follows the reverse complementary kinetics, but can become apparently uncoupled from extracellular matrix concentration for some parameter values. When matrix production by the cells and fragment degradation are taken into account, the dynamics change to sustained oscillations because of the emergence of a stable limit cycle. Transitions out of and into oscillation areas are controlled by the model parameters. Biological interpretation indicates that these oscillations could represent the normal homeostatic situation, whereas the other exhibited dynamics can be related to pathologies such as tumor invasion or fibrosis. These results allow to discuss the insights that the model could contribute to the comprehension of these complex biological events.

The selective regulation of alpha Vbeta 1 integrin expression is based on the hierarchical formation of alpha V-containing heterodimers

The integrin beta1 subunit can form a heterodimer with 12 different alpha subunits. According to the present model, the expression level of any alphabeta complex is regulated by the availability of the specific alpha subunit, whereas beta1 subunit is constantly present in a large excess. The expression of several heterodimers containing the alphaV subunit seems to be regulated by an identical mechanism. The fact that many cells express alphaVbeta1 heterodimer, and that this fibronectin/vitronectin receptor may be selectively regulated, compromises the present model of the regulation of beta1 and alphaV integrins. We have tried to solve this problem by assuming that distinct alphabeta heterodimers are formed with different tendency. To test the hypothesis, we analyzed WM-266-4 melanoma cells transfected with a cDNA construct coding for an intracellular single-chain anti-alphaV integrin antibody. We could see 70-80% reduction in the cell surface expression of alphaV subunit. However, the only one of the alphaV integrins reduced on the cell surface was alphaVbeta1. This suggests that the cell surface expression level of alphaVbeta1 is dependent on the number of alphaV subunits available after the formation of other alphaV-containing heterodimers. Thus, there seems to be a hierarchy in the complex formation between alphaV and its different beta-partners. These observations explain how alphaVbeta1 can be specifically regulated without concomitant changes in the expression of other alphaV or beta1 integrins.

Function of laminins and laminin-binding integrins in gingival epithelial cell adhesion

BACKGROUND

In human gingiva, epithelial cells attach to their adjacent tissues by means of specialized molecular adhesion complexes and a basement membrane. Little is known about the synthesis of adhesion proteins by gingival keratinocytes; we, therefore, studied how cultured immortalized gingival epithelial cells produce laminins and express laminin-binding integrins. We presumed that different laminins and integrins would be involved in the adhesion of gingival epithelial cells.

METHODS

We cultured gingival keratinocytes and studied their production of laminins and expression of integrins using immunofluorescence microscopy, immunoprecipitation, and immunoblotting methods and by quantitative cell adhesion experiments. We also studied how gingival tissue expresses these adhesion proteins in vivo by using immunofluorescence microscopy.

RESULTS

In immunofluorescence microscopy, the cells were seen to organize chains of laminin-5 (alpha3beta03gamma2) to extracellular patches, whereas the alpha5 chain of laminin-10 (alpha5betalgamma1) could only be seen intracellularly. Of the laminin-binding integrin subunits, integrin a6 subunit was organized to dotted arrays, typical of prehemidesmosomal adhesions, whereas integrin alpha3 subunit was located at cell-cell junctions, in prehemidesmosomal structures, and at some locations also in small focal-contact like patches. Integrin beta1 subunit was found at cell-cell junctions and in focal contacts. Immunoprecipitation experiments showed that the cells synthesize and secrete chains of laminin-5 and laminin-10. In quantitative cell adhesion experiments, the cells adhered efficiently to these laminins by using cooperatively integrin alpha3beta1 and alpha6beta1 integrin complexes. None of the other known laminin-binding integrin subunits appeared to be significantly involved in cell adhesion to these laminin isoforms.

CONCLUSIONS

Our results provide new information on gingival epithelial cell adhesion and extracellular matrix production and may thus aid in the understanding of periodontal physiology.

Proprotein convertases in tumor progression and malignancy: novel targets in cancer therapy

The mammalian subtilisin/kexin-like proprotein convertase (PC) family has been implicated in the activation of a wide spectrum of proteins. These proteins are usually synthesized as inactive precursors before their conversion to fully mature bioactive forms. A large majority of these active proteins such as matrix metalloproteases, growth factors, and adhesion molecules are crucial in the processes of cellular transformation, acquisition of the tumorigenic phenotype, and metastases formation. Inhibition of PCs significantly affects the malignant phenotype of various tumor cells. In addition to direct tumor cell proliferation and migration blockade, PC inhibitors can also be used to target tumor angiogenesis. In this Review article we discuss a number of recent findings on the clinical relevance of PCs in cancer patients, their implication in the regulation of multiple cellular functions that impact on the invasive/metastatic potential of cancer cells. Thus, PC inhibitors may constitute new promising agents for the treatment of multiple tumors and/or in adjuvant therapy to prevent recurrence.

Enhanced expression of the osteoblastic phenotype on substrates that modulate fibronectin conformation and integrin receptor binding

Integrins represent the primary mechanism of cell-extracellular matrix interactions and control cell morphology, proliferation, and differentiation. We have previously shown that substrate-dependent modulation of adsorbed fibronectin (Fn) conformation alters alpha5beta1 integrin binding to Fn and directs C2C12 myoblast proliferation and differentiation (Mol. Biol. Cell 10 (1999) 785). The model substrates used in these experiments were bacteriological (untreated) polystyrene (B), tissue culture polystyrene (T), and type-I collagen-coated T (C). In the present study, we examined MC3T3-EI osteoblast-like cell differentiation on Fn-coated B, T, and C substrates. Immunofluorescence staining revealed substrate-dependent differences in integrin alpha5beta1 binding and clustering into focal adhesions (C > T > B), consistent with our previous integrin binding analysis. Alkaline phosphatase activity and matrix mineralization showed substrate-dependent differences (C > T > B, p < 0.05). Similar trends were observed for alkaline phosphatase, osteocalcin, and bone sialoprotein gene expression. Blocking experiments with antibodies directed against Fn completely inhibited matrix mineralization on Fn-coated C, indicating that Fn is critical to expression of the osteoblastic phenotype on this extracellular matrix component. These substrate-dependent differences in osteoblast differentiation correlated with differences in alpha5beta1 binding, suggesting that these differences arise from substrate modulation of integrin-matrix interactions. Substrate-dependent modulation of cell function may provide a versatile mechanism to control cell responses in numerous biomedical applications.

Fibronectin in malignancy

Fibronectin (Fn) was the first 'structural' glycoprotein intensively studied as an ubiquitous matrix component of early phylogenetic appearance. Its age-dependent increase in plasma and tissues may be accompanied in pathological states, especially in tumor growth, by its proteolytic breakdown by a number of neutral proteases. It was also shown that several of its proteolytic breakdown products exhibit unexpected and mostly harmful biological activities. The first of these effects was a potentiation of malignant transformation. Some fragments had proteolytic activity, others behaved as proinflammatory agents stimulating IL-1 and collagenolytic MMP up-regulation. This matricryptic potential of Fn was followed by several other examples of proteolytic production of biologically active peptides. The study of solid human tumors showed among the early signs of malignant transformation the fragmentation of pericellular Fn, concommitent with the increase of its production by the peritumoral stroma. These results should encourage further investigations concerning the potential importance of Fn production and breakdown during cancer progression.

Proteolytic events of wound-healing--coordinated interactions among matrix metalloproteinases (MMPs), integrins, and extracellular matrix molecules

During wound-healing, cells are required to migrate rapidly into the wound site via a proteolytically generated pathway in the provisional matrix, to produce new extracellular matrix, and, subsequently, to remodel the newly formed tissue matrix during the maturation phase. Two classes of molecules cooperate closely to achieve this goal, namely, the matrix adhesion and signaling receptors, the integrins, and matrix-degrading and -processing enzymes, the matrix metalloproteinases (MMPs). There is now substantial experimental evidence that blocking key molecules of either group will prevent or seriously delay wound-healing. It has been known for some time now that cell adhesion by means of the integrins regulates the expression of MMPs. In addition, certain MMPs can bind to integrins or other receptors on the cell surface involved in enzyme activation, thereby providing a mechanism for localized matrix degradation. By proteolytically modifying the existing matrix molecules, the MMPs can then induce changes in cell behavior and function from a state of rest to migration. During wound repair, the expression of integrins and MMPs is simultaneously up-regulated. This review will focus on those aspects of the extensive knowledge of fibroblast and keratinocyte MMPs and integrins in biological processes that relate to wound-healing.

The 45 kDa collagen-binding fragment of fibronectin induces matrix metalloproteinase-13 synthesis by chondrocytes and aggrecan degradation by aggrecanases

Fragments of fibronectin occur naturally in vivo and are increased in the synovial fluid of arthritis patients. We have studied the 45 kDa fragment (Fn-f 45), representing the N-terminal collagen-binding domain of fibronectin, for its ability to modulate the expression of metalloproteinases by porcine articular chondrocytes in vitro. We report that stimulation of cultured chondrocytes, or cartilage explants, with Fn-f 45 increased the levels of matrix metalloproteinase-13 (MMP-13; collagenase-3) released into the conditioned medium in a dose-dependent manner. Increased levels of MMP-13 were due to stimulation of MMP-13 synthesis, rather than release of MMP-13 from accumulated matrix stores. Fn-f 45 also stimulated the synthesis of MMP-3 (stromelysin-1) from cultured chondrocytes and cartilage cultures. The Fn-f 45-induced increase in MMP-3 and MMP-13 synthesis occurred via an interleukin 1-independent mechanism, since the receptor antagonist of interleukin-1 was unable to block the increased synthesis. The gelatinases, MMP-2 and MMP-9, were not modulated by Fn-f 45 in these culture systems. Fn-f 45 also stimulated the release of aggrecan from cartilage explants into conditioned medium. Neoepitope antibodies specific for aggrecan fragments generated by MMPs or aggrecanases showed that the Fn-f 45-induced aggrecan loss was mediated by aggrecanases, and not by MMPs. Extracts of cultured cartilage contained elevated levels of the aggrecanase-derived ITEGE(373)-G1 domain, whereas levels of the matrix metalloproteinase-derived DIPEN(341)-G1 domain were unchanged. These studies show that Fn-f 45 can induce a catabolic phenotype in articular chondrocytes by up-regulating the expression of metalloproteinases specific for the degradation of collagen and aggrecan.

Antisense oligonucleotides to the integrin receptor subunit alpha(5) decrease fibronectin fragment mediated cartilage chondrolysis

OBJECTIVE

To investigate involvement of the integrin alpha(5) subunit of the classical fibronectin receptor in cartilage chondrolytic activities of fibronectin fragments (Fn-f).

DESIGN

Bovine chondrocytes and cartilage explants were cultured in the presence of antisense oligonucleotide (ASO), or sense (SO) or scrambled sequence oligonucleotide (SCO) corresponding to the bovine alpha(5) subunit. The effects of the oligonucleotides on mRNA and protein expression of the alpha(5) subunit were analysed by rtPCR and Western blotting, respectively. To test effects on Fn-f activities, three different Fn-f were first added to serum or serum-free cultures, followed by addition of oligonucleotides and the effects on Fn-f mediated proteoglycan (PG) degradation, cartilage PG depletion and PG and general protein synthesis suppression were tested.

RESULTS

The ASO decreased alpha(5) mRNA and protein expression to 69% and 55%, respectively, in monolayer cultures and decreased protein expression 67% in cartilage explants, while SO and SCO were ineffective. The ASO partially reversed the ability of the Fn-fs to suppress PG and general protein synthesis in cartilage explant and high density chondrocyte cultures. Concentrations of ASO from 1 nM to 5 microM effectively suppressed Fn-f activities in particular assays and the effects were reversible, while SO and SCO were not significantly effective. ASO also suppressed, in a dose-dependent and reversible fashion, the ability of the Fn-fs to enhance degradation and release of PG from cartilage explants. The ASO were also effective in suppressing the ability of an antibody to the alpha(5) subunit to enhance PG degradation, but were ineffective in blocking endotoxin or IL-1beta enhanced degradation.

CONCLUSIONS

These data implicate the alpha(5) integrin subunit in Fn-f mediated activities, consistent with a role for the alpha(5)beta(1) integrin in this pathway.

Human Ly-6 antigen E48 (Ly-6D) regulates important interaction parameters between endothelial cells and head-and-neck squamous carcinoma cells

Selectin ligands are crucial components in the interaction between endothelial cells and extravasating cancer cells and, thus, play an important role in metastasis formation. Head-and-neck squamous cell carcinoma (HNSCC) variants expressing high levels of E48, a human Ly-6 protein (E48(hi)), expressed higher levels of the fucose-generating FX enzyme and of the fucosylated E-selectin ligand sLe(a) than cells expressing low levels of E48 (E48(lo)). Signaling through E48 upregulated expression levels of these molecules in HNSCC. In this work, we provide further evidence supporting the E48-FX-sLe(a) link by showing that FX antisense oligonucleotides reduced sLe(a) expression levels in HNSCC. We also show that E48 may be causally involved in regulating expression levels in HNSCC of 2 additional enzymes involved in the biosynthesis of sLe(a), namely, ST-30 and FucTIII. Also, selectin-mediated adhesion of E48(hi) variants to activated HUVECs was significantly higher than that of E48(lo) variants. Transfection experiments utilizing sense or antisense E48 cDNA indicated that E48 may be causally involved in this adhesion. Chemokines are involved in the extravasation process of tumor cells. The release of chemoattractants from HNSCC variants differing in E48 expression was therefore analyzed. HNSCC did not release any chemoattractants but induced the release of such factors from HUVECs. Supernatants from E48(hi) variants were significantly more efficient than E48(lo) cells at inducing the release of chemoattractants from HUVECs. Transfection experiments indicated that E48 may be causally involved in the induction of chemoattractant release from HUVECs. Angiogenesis is an important manifestation of cancer-endothelium interactions. We therefore assayed for the presence of angiogenic factors in culture supernatants of HNSCC. Supernatants from E48(lo) variants contained significantly higher amounts of PDGF than E48(hi) cells. Transfection experiments indicated that E48 may be causally involved. Taken together, our results suggest that E48 controls important interaction parameters between HNSCC and endothelial cells.

Stimulation of matrix metalloproteinase-9 expression in human fibrosarcoma cells by synthetic matrix metalloproteinase inhibitors

Enhanced expression and activation of matrix metalloproteinase-2 (MMP-2) and MMP-9 have been associated with tumor progression, invasion, and metastasis. The use of synthetic MMP inhibitors to block the proteolytic activity of these enzymes recently emerged as a potential therapeutic tool to treat cancer. In this study, we report that GI129471, a synthetic broad-spectrum MMP inhibitor, efficiently reduced the in vitro invasiveness of HT1080 cells through type IV collagen, a major component of basement membranes. This reduced invasion was paralleled by a complete inhibition of pro-MMP-2 activation; however, GI129471 strongly increased the amount of secreted pro-MMP-9, which could be subsequently activated through a plasminogen-dependent mechanism. Quantitative RT-PCR and northern blot analysis revealed that GI129471 specifically increased the MMP-9 mRNA steady-state level. Moreover, transient transfection of HT1080 cells with beta-galactosidase reporter vectors containing different lengths of the 5'-flanking region of the MMP-9 gene revealed an upregulation of the transcriptional activity of the corresponding promoter. Well-known modulators of MMP-9 expression such as Il-1beta and TNF-alpha were not involved in this upregulation. These findings emphasize the complexity of the regulation of MMP expression and the requirement for a detailed characterization of the potential adverse side effects associated with the use of broad-spectrum MMPIs.

Sensing the environment: a historical perspective on integrin signal transduction

Cell adhesion mediated by integrin receptors has a critical function in organizing cells in tissues and in guiding haematopoietic cells to their sites of action. However, integrin adhesion receptors have broader functions in regulating cell behaviour through their ability to transduce bi-directional signals into and out of the cell and to engage in reciprocal interactions with other cellular receptors. This historical perspective traces the key findings that have led to our current understanding of these important functions of integrins.

Expression of integrin beta 6 enhances invasive behavior in oral squamous cell carcinoma

Oral squamous cell carcinoma (SCC) is characterized by invasive growth and the propensity for distant metastasis. The expression of specific adhesion receptors promotes defined interactions with the specific components found within the extracellular matrix (ECM). We previously showed that the alpha v beta 6 fibronectin receptor is highly expressed in oral SCC. Here we forced expression of the beta 6 subunit into poorly invasive SCC9 cells to establish the SCC9 beta 6 cell line and compared these two cell lines in several independent assays. Whereas adhesion to fibronectin was unaffected by the expression of beta 6, migration on fibronectin and invasion through a reconstituted basement membrane (RBM) were both increased. Function-blocking antibodies to alpha v beta 6 (10D5) reduced both migration on fibronectin and invasion through an RBM, whereas anti-alpha 5 antibodies were effective only in suppressing migration on fibronectin, not invasion. Expression of beta 6 also promoted tumor growth and invasion in vivo and modulated fibronectin matrix deposition. When grown as a co-culture with SCC9 cells, peritumor fibroblasts (PTF) organized a dense fibronectin matrix. However, fibronectin matrix assembly was decreased in co-cultures of SCC9 beta 6 cells and PTF and this decrease was reversed by the addition of function-blocking anti-alpha v beta 6 antibodies. The expression of beta 6 also resulted in increased levels of matrix metalloproteinase 3. Addition of the general MMP inhibitor GM6001 to SCC9 beta 6/PTF co-cultures dramatically increased fibronectin matrix assembly in a similar fashion as incubation with anti-alpha v beta 6 antibodies. These results demonstrate that expression of beta 6 (1) increases oral SCC cell motility and growth in vitro and in vivo; (2) negatively affects fibronectin matrix assembly; and (3) stimulates the expression and activation of MMP3. We suggest that the integrin alpha v beta 6 is a key component of oral SCC invasion and metastasis through modulation of MMP-3 activity.

Differential integrin expression by cardiac fibroblasts from hypertensive and exercise-trained rat hearts

The cardiac fibroblast is the principal cell type responsible for extracellular matrix (ECM) synthesis in the heart during growth and pathophysiological conditions. A dynamic interaction exists between the cardiac ECM and fibroblasts that is sensitive to the local mechanical and chemical tissue environment. We propose here that cardiac fibroblasts structurally and functionally adapt to changing local environments by altering their expression of receptor integrins. Changes in the extracellular environment are communicated in part by integrins, which link the ECM to the cell and regulate phenotype and function. In this report, we analyze integrin protein expression, migration and gel contraction by cardiac fibroblasts from rats subjected to 10 weeks of treadmill exercise (XTR), experimental hypertension (HYP) or controls (CONT). Immunoprecipitation shows that beta1 protein increases in XTR and HYP. Also, alpha1 and alpha2 integrins are lower in XTR and HYP, and alpha5 integrin is higher in XTR and lower in HYP. Functional assays show that XTR and HYP migrate slower on collagen, while XTR migrate faster and HYP slower on fibronectin. Cell isolation procedure, population expansion number or a general adaptation to culture conditions does not explain the differences observed. No significant differences in collagen gel contraction are detected. These results indicate that cardiac fibroblasts retain their in vivo patterns in vitro for a limited number of population expansions. This tissue-specific phenotype is exhibited in early passage (< or =6). However, by late passage (>8), cells begin to show adaptation to the in vitro conditions. These results show that cardiac fibroblasts respond to changing environments in pathophysiological conditions by modulating integrin expression, which is associated with changes in cell migration. They also suggest a pragmatic use for primary cardiac fibroblasts as a model to study the cardiac matrix remodeled by physiological (exercise) and pathological (hypertension) stressors.

Overexpression of alpha(v)beta6 integrin in serous epithelial ovarian cancer regulates extracellular matrix degradation via the plasminogen activation cascade

Recent evidence suggests that integrins are involved in the multi-step process of tumour metastasis. The biological relevance of alpha(v) integrins and associated beta-subunits in ovarian cancer metastasis was examined by analysing the expression of these cell surface receptors in nine ovarian cancer cell lines and also in the primary human ovarian surface epithelial cell line (HOSE). beta1, beta3 and beta5 subunits were present in all ten ovarian cell lines. beta6 subunit was present at varying levels in eight out of nine cancer cell lines but was absent in the HOSE cell line. Immunohistochemical staining showed that beta6 was present in both non-invasive (borderline) and high-grade ovarian cancer tissues but was absent in benign and normal ovarian tissue. High alpha(v)beta6 integrin expressing ovarian cancer cell lines had high cell surface expression of uPA and uPAR. Ovarian cancer cell lines expressing high to moderate level of alpha(v)beta6 integrin demonstrated ligand-independent enhanced levels of high molecular weight (HMW)-uPA and pro-matrix metalloproteinase 2 and 9 (pro-MMP-2 and pro-MMP-9) expression in the tumour-conditioned medium. High and moderate expression of alpha(v)beta6 integrin correlated with increased plasminogen-dependent degradation of extracellular matrix which could be inhibited by inhibitors of plasmin, uPA and MMPs or by monoclonal antibody against uPA, MMP-9 or alpha(v)beta6 integrin. These results suggest that endogenous de novo expression of alpha(v)beta6 integrin in ovarian cancer cells may contribute to their invasive potential, and that alpha(v)beta6 expression may play a role in ovarian cancer progression and metastasis.

Hepatocyte growth factor induces collagenase (matrix metalloproteinase-1) via the transcription factor Ets-1 in human hepatic stellate cell line

BACKGROUND/AIMS

Although hepatocyte growth factor recently has been shown to decrease hepatic fibrosis in animal models, the molecular mechanisms of this effects remain to be elucidated. We investigated regulation of collagenase expression by hepatocyte growth factor in hepatic stellate cells.

METHODS

A human hepatic stellate cell line, LI90, was treated with hepatocyte growth factor. Expression of collagenase, 72 kDa gelatinase, procollagen alpha 1(I), tissue inhibitor of matrix metalloproteinase-1, transforming growth factor-beta 1, or Ets-1, and carboxyterminal telopeptide of type I collagen was examined. Ets-1 binding activity was determined by gel mobility shift assay, collagenase promoter activity was evaluated by reporter gene assay. LI90 cells were also transfected with Ets-1 antisense oligonucleotides with or without hepatocyte growth factor.

RESULTS

Hepatocyte growth factor increased expression of collagenase mRNA and protein, and an increase in Ets-1 mRNA preceded the increase in collagenase mRNA. Collagenase activity and protein, and a degradation product of type I collagen were increased in the medium. Nuclear extracts from treated LI90 cells also showed increased Ets-1 binding activity. Hepatocyte growth factor and cotransfection of Ets-1 enhanced promoter activity of collagenase gene. Furthermore, treatment of LI90 cells with Ets-1 antisense oligonucleotides downregulated basal and hepatocyte growth factor-induced Ets-1 and collagenase mRNA expression.

CONCLUSIONS

Collectively, the results suggest that hepatocyte growth factor increases collagenase expression in hepatic stellate cells via the Ets-1 transcription factor-dependent manner.

The role of proteases in fibronectin matrix remodeling in thyroid epithelial cell monolayer cultures

Fischer rat thyroid (FRT) cells organize a matrix of extracellular fibronectin (FN) fibrils, which undergoes extensive remodeling according to cell culture confluence. In non-confluent cells FN forms a fibrillar array associated with the ventral cell surface. However, basal FN is progressively removed in confluent cultures and substituted by non-fibrillar FN deposits at lateral cell domains in regions of cell-cell contacts. FRT cells secrete and expose on the plasma membrane the tissue-type plasminogen activator and, in serum-free cultures, plasminogen induces a rapid loss of FN fibrils. Incubation with plasmin inhibitors greatly reduces this effect. FRT cells also express annexin II, a plasminogen receptor, suggesting that plasmin activity is associated with the pericellular enviroment. This is in agreement with the observation that a great reduction in FN degradation is observed if the cells are pre-incubated with carboxypeptidase B, which prevents plasminogen binding to the cells. A gelatinolytic activity with a molecular weigth equivalent to MMP-2 has been demonstrated by zymography of culture media, and the presence of MMP-2 and MT1-MMP on the cell plasma membrane has been detected by immunofluorescence. These results indicate that in the FN remodeling process, occurring during FRT epithelium maturation, both plasmin-dependent (tPA activated) and plasmin-independent proteolytic activities are involved.

A fibronectin fragment induces type II collagen degradation by collagenase through an interleukin-1-mediated pathway

OBJECTIVE

To examine the effects of a fibronectin (FN) fragment containing the COOH-terminal heparin-binding domain (HBFN-f) on chondrocyte-mediated type II collagen (CII) cleavage by collagenase and proteoglycan (PG) degradation in articular cartilage in explant culture.

METHODS

Intact FN or HBFN-f was added to explant cultures of mature bovine articular cartilage. We investigated collagenase-mediated cleavage of CII caused by HBFN-f in explant cultures using a new immunoassay for detection and measurement of the primary collagenase cleavage site of CII. CII denaturation in cartilage was also measured using a specific enzyme-linked immunosorbent assay. Degradation of PG (principally aggrecan) was analyzed by a dye-binding assay. APMA and/or a matrix metalloproteinase 13 (MMP-13) preferential inhibitor or interleukin-1 receptor antagonist (IL-1Ra) were added to some cultures to examine the presence of latent procollagenase or the involvement of MMP-13 or IL-1, respectively, in cartilage breakdown induced by HBFN-f. Secretion of MMP-3 and MMP-13 into media was detected by immunoblotting.

RESULTS

In contrast to intact FN, HBFN-f was shown to stimulate CII cleavage by collagenase in a dose-dependent manner following PG degradation, similar to cartilage breakdown induced by IL-1. Treatment with HBFN-f also resulted in elevated denaturation of CII. Immunoblotting demonstrated that HBFN-f enhanced pro-matrix metalloproteinase 13 (proMMP-13) production as well as that of proMMP-3. APMA, which activates latent proMMPs, enhanced the HBFN-f-mediated cleavage of CII by collagenase. An MMP-13 preferential inhibitor or IL-1Ra suppressed HBFN-f-induced collagen cleavage to control levels.

CONCLUSION

Our data demonstrate that HBFN-f can induce early PG degradation and subsequent CII cleavage. The latter is probably mediated by early proMMP-13 induction involving an IL-1-dependent pathway. Activation of latent collagenase is delayed. This new information, together with existing data on other FN fragments, reveals that increased levels of these fragments, found in diseased joints such as in osteoarthritis and rheumatoid arthritis, may stimulate cartilage breakdown by mechanisms of the kind demonstrated in the present study.

Cartilage viability after repetitive loading: a preliminary report

OBJECTIVE

To assess matrix changes and chondrocyte viability during static and continuous repetitive mechanical loading in mature bovine articular cartilage explants.

METHODS

Cartilage explants were continuously loaded either statically or cyclically (0.5 Hz) for 1-72 h (max. stress 1 megapascal). Cell death was assessed using fluorescent probes and detection of DNA strand breakage characteristic of apoptosis. Cell morphology and matrix integrity were evaluated using histology and transmission electron microscopy.

RESULTS

Repetitive loading of articular cartilage at physiological levels of stress (1 megapascal) was found to be harmful to only the chondrocytes in the superficial tangential zone (STZ) and depended on the characteristics (static vs cyclic) and duration (1-72 h) of the applied load. The chondrocytes in the middle and deep zone remained viable at all times. Static loads caused cell death at an early time (3 h) as compared with cyclic loads (sinusoidal, 0.5 cycles per s for 6 h). The amount and extent of cell death peaked at 6 h of cyclic loading, and did not change in subsequent experiments run for longer periods of time (up to 72 h). There was no indication of fragmented nuclear DNA but there was evidence of injurious cell death (necrosis) by electron microscopy. Morphological analysis of cartilage repetitively loaded for 24 h showed matrix damage only in the uppermost superficial layer at the articular surface, reminiscent of the early stages of osteoarthritis.

CONCLUSIONS

Cell death in mature cartilage explants occurred after 6 hours of continuous repetitive load or 3 h of static load. Cell death was directly related to the mechanical load, as control (free-swelling) explants remained viable at all times. The excessive, repetitive loading conditions imposed are not physiological, and demonstrate the deleterious effects of mechanical overload resulting in morphological and cellular damage similar to that seen in degenerative joint disease.

Evaluation of extracellular matrix proteins and tissue inhibitor of matrix metalloproteinases-2 on bovine inner cell mass outgrowth in vitro

Effects of extracellular matrix proteins and tissue inhibitor of matrix metalloproteinases-2 (TIMP-2) on bovine inner cell mass (ICM) outgrowth and proteinase production in vitro were determined. Inner cell masses were isolated immunosurgically from day 7 embryos (day 0 = onset of estrus) and cultured for 96 h. In experiment 1, cellular outgrowth and gelatinase production were evaluated for ICM cultured on collagen IV, fibronectin, or laminin. More (P < 0.05) ICM generated cellular outgrowth on fibronectin (71%). compared with collagen IV (0%) or laminin (15%). Inner cell mass and outgrowth areas were greatest (P < 0.05) on fibronectin after 96 h of culture, compared with laminin. Although the incidence of cellular outgrowth on laminin was limited, numbers of cells in outgrowths supported by laminin were similar (P > 0.10) to fibronectin except at 72 h of culture, where more (P < 0.05) cells were in laminin than in fibronectin outgrowths. Gelatinase activity was not detected in conditioned medium. In experiment 2, cellular outgrowth and plasminogen activator production by ICM cultured on fibronectin in medium containing 0 or 10 microg/ml TIMP-2 were evaluated. Inner cell mass and outgrowth areas, and numbers of cells in outgrowths were greater (P < 0.05) in 10 compared with 0 microg/ml TIMP-2 at 96 h of culture. Mean plasminogen activator activity in conditioned medium from ICM cultured in 10 microg/ml TIMP-2 was greater (P < 0.05) compared with 0 microg/ml TIMP-2 (16.2 +/- 4.8 versus 6.7 +/- 1.4 x 10(-3) IU/ml, respectively). These results demonstrate that cellular outgrowth from bovine ICM is supported by fibronectin and is stimulated by TIMP-2.

The angiogenic factor Cyr61 activates a genetic program for wound healing in human skin fibroblasts

Cyr61 is a heparin-binding, extracellular matrix-associated protein of the CCN family, which also includes connective tissue growth factor, Nov, WISP-1, WISP-2, and WISP-3. Cyr61 is capable of multiple functions, including induction of angiogenesis in vivo. Purified Cyr61 mediates cell adhesion and induces adhesive signaling, stimulates cell migration, enhances cell proliferation, and promotes cell survival in both fibroblasts and endothelial cells. In this study, we have used cDNA array hybridization to identify genes regulated by Cyr61 in primary human skin fibroblasts. The Cyr61-regulated genes fall into several groups known to participate in processes important for cutaneous wound healing, including: 1) angiogenesis and lymphogenesis (VEGF-A and VEGF-C); 2) inflammation (interleukin-1beta); 3) extracellular matrix remodeling (MMP1, MMP3, TIMP1, uPA, and PAI-1); and 4) cell-matrix interactions (Col1alpha1, Col1alpha2, and integrins alpha(3) and alpha(5)). Cyr61-mediated gene expression requires heparin binding activity of Cyr61, cellular de novo transcription, and protein synthesis and is largely dependent on the activation of p42/p44 MAPKs. Cyr61 regulates gene expression not only in serum-free medium but also in fibroblasts cultured on various matrix proteins or in the presence of 10% serum. These effects of Cyr61 can be sustained for at least 5 days, consistent with the time course of wound healing in vivo. Interestingly, Cyr61 can interact with transforming growth factor-beta1 to regulate expression of specific genes in an antagonistic, additive, or synergistic manner. Furthermore, we show that the Cyr61 gene is highly induced in dermal fibroblasts of granulation tissue during cutaneous wound repair. Together, these results show that Cyr61 is inducibly expressed in granulation tissues after wounding and that Cyr61 activates a genetic program for wound repair in skin fibroblasts. We propose a model in which Cyr61 integrates its activities on endothelial cells, fibroblasts, and macrophages to regulate the processes of angiogenesis, inflammation, and matrix remodeling in the context of cutaneous wound healing.

Expression of a novel matrix metalloproteinase gene during Cynops early embryogenesis

Matrix metalloproteinases (MMPs) are thought to play important roles in the gastrulation of Cynops pyrrhogaster embryos. MMP cDNAs were cloned from Cynops pyrrhogaster and we report here a novel MMP called CyMMP, which has strong similarity to MMP-21 (XMMP) in Xenopus. Reverse transcription-polymerase chain reaction (RT-PCR) analysis demonstrated that CyMMP mRNA was already present in cleavage stage embryos. The amount of the mRNA then gradually decreased, but increased again starting in late gastrula. There were regional differences in the level of CyMMP mRNA expression at late gastrula: the involved archenteron roof was the predominant site of expression of the gene, while there was weak expression in the neuroectoderm and epidermal ectoderm. We also found that the gene was activated in artificially mesodermalized ectoderm. The present findings indicate that CyMMP mRNA expression is activated in differentiating mesoderm during gastrulation, suggesting that CyMMP plays a role in gastrulation-related cell movement.

Cartilage damage by matrix degradation products: fibronectin fragments

Catabolic cytokines play a major role in cartilage degradation not only in rheumatoid arthritis but also in osteoarthritis. Although the major source in rheumatoid arthritis may be mononuclear cells and synovial tissue and the cause of release may be multifactorial, the source of cytokines in osteoarthritis would be mostly from chondrocytes. However, there are few explanations of how upregulation of the cytokines might occur in osteoarthritis. One possibility is that degradation products of the extracellular matrix arising from elevated protease levels, substrate, or both, might regulate cytokine activities. Fragments of the extracellular matrix protein, fibronectin, upregulate cytokine expression and induce the events of suppressed matrix synthesis and upregulation of matrix metalloproteinases, characteristic of osteoarthritis. The catabolic aspects of this system are short term, subsequently serve to enhance anabolic processes above untreated levels, and condition the tissue against additional insult. It will be necessary to determine whether in vivo these degradation products precede cytokine expression and act early and are targets for intervention or instead are a consequence of cytokine damage. Whether they regulate anabolism and catabolism, blocking of their activities may not be ideal.

Adhesion strength of individual human bone marrow cells to fibronectin. Integrin beta1-mediated adhesion

The purpose of this work was to study the adhesion strength of individual bone marrow cells, using a micropipette aspiration technique. The adhesion strength of the primary human bone marrow cells to fibronectin-coated substrate, by blocking the beta1 integrin with and without antibodies, was also determined. Human bone marrow stromal cells of the second passage were seeded at a density of 500 cells/cm2 on two different substrates: plastic culture dish (PCD) and PCD coated with fibronectin. In short adhesion times (15-180 min) the cells attached without spreading and remained almost spherical. A negative pressure of about 3500 Pa was applied, through the micropipette, on individual bone marrow cells and the detach process was recorded. The tip of the micropipette was bent at an 130 degrees angle to the corpus of the pipette and it was manipulated to be on the upper side of the cell and vertically to the bottom of the plate. It was observed from the experiments that the cells exhibited smaller adhesion strength at early adhesion times (30-85 min). After 85 min the adhesion strength increased abruptly and remained relatively constant for the adhesion period from 85 to 180 min for all substrates. Monoclonal antibodies against integrin subunit beta1 were used for integrin blocking experiments. The data suggested that the attachment of osteoblasts to a plastic culture dish without fibronectin coating occurred earlier than to the one coated with fibronectin PCD. In longer adhesion time the coating with fibronectin increased the adhesion strength at 107%. Blocking of integrin beta1 with monoclonal antibody resulted in decrease of the adhesion strength at 49%.

Age-associated changes in cardiac matrix and integrins

The progressive shift from young age to senescence is characterized by structural and functional changes in the cardiac extracellular matrix (ECM), which supports and aligns myocytes and blood vessels, and maintains myocardial mass, structure and function. As cardiac function declines with advancing age, ECM collagen and fibronectin influence diastolic stiffness. ECM binding to membrane-bound receptors, or integrins, directly links ECM to cardiac muscle and fibroblast cells, affording it the permissive role to modulate heart function. To better understand the ECM structure-function relationship in the old heart, we studied the relative protein content of these ECM proteins and integrins across three age groups. Old Balb-c mice (20 months) exhibit biventricular, cardiac hypertrophy, and greater left ventricular (LV) collagen, fibronectin, alpha 1 and alpha 5 integrin protein than middle-aged (12 months) or young (2 months) LV (P<0.05). beta1 integrin protein content is lower in old LV (P<0.05). These data show that advancing age is associated with greater collagen, fibronectin, alpha 1 and alpha 5 integrin content, suggesting that these matrix proteins undergo coordinated regulation in the aging heart. The differential integrin and ECM protein content suggests that there is regulatory signaling to the fibroblasts, which maintain the cardiac ECM.

Accelerated apoptosis in the Timp-3-deficient mammary gland

The proapoptotic proteinase inhibitor TIMP-3 is the only molecule of this family thought to influence cell death. We examined epithelial apoptosis in TIMP-3-deficient mice during mammary gland involution. Lactation was not affected by the absence of TIMP-3, but glandular function, as measured by gland-to-body weight ratio and production of beta-casein, was suppressed earlier during post-lactational involution than in controls. Histological examination revealed accelerated lumen collapse, alveolar-epithelial loss, and adipose reconstitution in Timp-3(-/-) females. Epithelial apoptosis peaked on the first day of involution in Timp-3-null glands but at day 3 in wild-type littermates. Unscheduled activation of gelatinase-A was evident by zymography and correlated with earlier fragmentation of fibronectin in Timp-3(-/-) mammary. To obtain independent evidence of the proapoptotic effects of TIMP-3 deficiency, we introduced recombinant TIMP-3-releasing pellets into regressing Timp-3(-/-) mammary tissue and showed that this treatment rescued lumen collapse and epithelial apoptosis. Ex vivo, involuting Timp-3(-/-) mammary tissue demonstrated accelerated epithelial apoptosis that could be reduced by metalloproteinase inhibition. The physiological relevance of TIMP-3 became apparent as Timp-3(-/-) dams failed to reestablish lactation after brief cessation of suckling. Thus, TIMP-3 is a critical epithelial survival factor during mammary gland involution.

Phenotypic alterations in Caki-1 cells as a consequence of TIMP-1 overexpression

Maintenance of the extracellular matrix (ECM) is important for tissue integrity and cellular physiology. Normal ECM turnover is regulated by a balance between matrix metalloproteinases and their inhibitors, the tissue inhibitors of metalloproteinases (TIMPs). In metastasis, this balance favours increased ECM degradation. The objective of this study was to determine the effects of TIMP-1 overexpression on the metastatic process. To this end, we stably transfected a renal carcinoma cell line, Caki-1, with TIMP-1, using a pRc/CMV expression plasmid and LIPOFECTAMINE transfection reagent. The resultant clones displayed increased adhesion on the ECM substratum, including collagen type IV and laminin, and altered invasive capacity through fibronectin and Matrigel, dependent upon the level of TIMP-1 expression. These changes were not due to altered integrin expression, as assessed by flow cytometry. As well as protease inhibitory activity, TIMPs can influence cell proliferation and cell survival. The TIMP-1 clones displayed no changes in proliferation under normal growth conditions, compared with Caki-1 cells. However, under reduced serum conditions, the TIMP-1 clones had a greater percentage of cells in both S (P<0.05) and G(2)/M (P<0.005) phases and less cells in G(0)/G(1) (P<0.001) of the cell cycle than Caki-1 cells. The results confirm a dual role for TIMP-1 in invasion and metastasis, and provide further clues behind the molecular mechanisms in these processes.

Inhibition of proprotein convertases is associated with loss of growth and tumorigenicity of HT-29 human colon carcinoma cells: importance of insulin-like growth factor-1 (IGF-1) receptor processing in IGF-1-mediated functions

Proprotein convertases (PCs) of the subtilisin/kexin family are responsible for the activation of prohormones, protrophic factors, and their receptors. We sought to determine whether loss of PC-mediated activities might affect the malignant phenotypes of cancer cells. Stable transfectants of alpha(1)-antitrypsin Portland (alpha(1)-PDX) cDNA, coding for a potent PC inhibitor, were analyzed in model HT-29 cells (HT-29/PDX) and in other cell lines. Expression of alpha(1)-PDX resulted in a proinsulin-like growth factor-1 receptor (pro-IGF-1R) processing blockade, hence inhibiting the ability of exogenous IGF-1 to induce tyrosine phosphorylation of its beta-subunit and insulin-related substrate-1. Coexpression of IGF-1R with four different PCs or the novel convertase SKI-1 in the furin-defective LoVo-C5 cells demonstrated that pro-IGF-1R ( approximately 200 kDa) cleavage into IGF-1R (beta-subunit, approximately 105 kDa) can be achieved by furin and PC5A, but not by PACE4, PC7, or SKI-1. Expression of alpha(1)-PDX resulted in reduction of DNA synthesis and in anchorage-independent growth. Following serum deprivation, the alpha(1)-PDX transfectants exhibited an enhanced apoptotic phenotype and were insensitive to IGF-1-mediated [(3)H]thymidine incorporation and protection against apoptosis. These cells showed reduced invasiveness that paralleled decreased mRNA levels of urokinase-type plasminogen activator and its receptor, tissue-type plasminogen activator, and plasminogen activator inhibitor-1. Comparative subcutaneous inoculation of cells in nude mice revealed that animals injected with HT-29/PDX cells exhibited delayed and lower incidence of tumor development as well as reduced tumor size. Immunohistochemical analysis of CD31 antigen expression, a marker of endothelial cells, revealed reduced HT-29/PDX tumor vascularization. These findings indicate that PCs actively contribute to the growth and malignant phenotypes of HT-29 tumors, suggesting that PC inhibition strategies may be a useful adduct to the arsenal of colorectal anticancer gene therapies.

Effects of matrix proteins on the expression of matrix metalloproteinase-2, -9, and -14 and tissue inhibitors of metalloproteinases in human cytotrophoblast cells during the first trimester

The activity of matrix metalloproteinases (MMPs) specifies the ability of the trophoblast cell to degrade extracellular matrix (ECM) substrates. Usually the process of normal human placentation involves a coordinated interaction between the fetal-derived trophoblast cells and their microenvironment in the uterus. In this study, the effects of ECM proteins on the expression of MMP-2, -9, and -14 (membrane-type MMP-1); and the production of tissue inhibitors of metalloproteinase (TIMP) types -1, -2, and -3 have been investigated. Cytotrophoblast cells at 9 or 10 wk of gestation were cultured on various ECM coated dishes under serum-free conditions. Gelatin zymography analysis showed that cells grown on fibronectin (FN), laminin (LN), and vitronectin (VN) secreted more MMP-9 (about 1.5- to 3-fold more) than cells cultured on collagen I (Col I), whereas the secretion of MMP-9 by cells cultured on collagen IV (Col IV) was only half that by the cells on Col I. Northern Blot analysis gave the same results as zymography, indicating that expression of the MMP-9 gene in cytotrophoblast cells can be affected by matrix proteins. There was no significant difference in the expression of MMP-2 either at protein or mRNA levels among the cells cultured on the different matrix substrates. The expression of MMP-14 was regulated in a manner similar to that of MMP-2. Using ELISA, we detected higher levels of TIMP-1 in the culture medium of cells grown on VN, LN, and FN compared with that grown on Col I. But the expression of TIMP-3 mRNA was remarkably inhibited by VN, and ECM proteins had no effect on TIMP-1 and TIMP-2 mRNA expression. It was also observed that cultured cytotrophoblast cells expressed the corresponding receptors for the tested matrix proteins, such as integrins alpha(1), alpha(5), alpha(6), beta(1), and beta(4). Furthermore, the adhesiveness of cytotrophoblast cells on Col I, Col IV, FN, and LN was increased by 62%, 45%, 21%, and 22%, respectively, when compared with adhesiveness on VN. Isolated cytotrophoblast cells remained stationary when cultured on dishes coated with Col I and Col IV, but they assumed a more motile morphology and aggregated into a network when cultured on LN and VN. These data indicate that human trophoblast cells interact with their microenvironment to control their behavior and function.

Role of stem cell factor and c-kit signaling in regulation of fetal intestinal epithelial cell adhesion to fibronectin

The interaction of stem cell factor (SCF) and c-kit is considered to be an important signaling event for the homeostasis of the epithelial barrier function in the intestinal tract. This study was designed to investigate the role of the SCF and c-kit signaling pathway in adhesion of intestinal epithelial cells (IECs) to fibronectin (FN) using primary cells. Fetal murine IECs were prepared from the small intestine of mouse fetus. The mRNAs coding for SCF in mesenchymes and c-kit in IECs were detected by reverse transcription-PCR. The expression of FN receptor VLA-5 on IECs was examined by flow cytometry. A cell adhesion assay showed that the stimulation of IECs with SCF increased the number of cells adhering to FN. Experiments using specific antibody against SCF indicated that this increase in cell adhesion was SCF-dependent. On the other hand, SCF did not influence the expression of VLA-5 on IECs. The IEC adhesion to FN was inhibited by specific antibody against the FN receptor (VLA-5), as well as competitive Arg-Gly-Asp (RGD) peptide. When alteration of intracellular signal transduction induced by SCF was examined, it was found that SCF stimulated a tyrosine-specific c-kit autophosphorylation cascade of IECs. Further, preincubation of IECs with an optimal concentration of genistein resulted in the inhibition of SCF-induced c-kit phosphorylation and adhesion of IECs to FN. These results suggested that adhesion of immature IECs to FN is regulated by activation of RGD-dependent VLA-5 through the SCF and c-kit signal transduction pathway. SCF, which may be produced by mesenchymes locally, is an important regulatory factor for the adhesion of immature IECs to basement membrane matrix via VLA-5 and FN interaction. This cytokine-regulated interaction between VLA-5 and FN may play an important role in the development and wound repair of the intestinal tract.

Synergistic effect of titanium alloy and collagen type I on cell adhesion, proliferation and differentiation of osteoblast-like cells

A number of studies have demonstrated the pivotal role of collagen in modulating cell growth and differentiation. In bone, where the extracellular matrix is composed of approximately 85% type I collagen, cellular interaction with matrix components has been shown to be important in the regulation of the osteoblast phenotype. Preservation or enhancement of normal osteoblast function and appositional bone formation after implant placement represents a strategy that can be useful for the purpose of improving osseointegration. In order to further improve biocompatibility, we combined two known favorable compounds, namely the titanium alloy, Ti6A14V, with type I collagen. We assessed the in vitro behavior of primary osteoblasts grown on both fibrillar collagen-coated and tropocollagen-coated Ti6A14V in comparison with uncoated titanium alloy, using an improved adsorption procedure. As parameters of biocompatibility, a variety of processes, including cell attachment, spreading, cytoskeletal organization, focal contact formation, proliferation and expression of a differentiated phenotype, were investigated. Our results demonstrated for the first time that in comparison to uncoated titanium alloy, collagen-coated alloy enhanced spreading and resulted in a more rapid formation of focal adhesions and their associated stress fibers. Growing on collagen-coated Ti6A14V, osteoblasts had a higher proliferative capacity and the intracellular expression of osteopontin was upregulated compared to uncoated titanium alloy. Type I collagen-coated titanium alloy exhibits favorable effects on the initial adhesion and growth activities of osteoblasts, which is encouraging for its potential use as bone graft material. Moreover, collagen type I may serve as an excellent biocompatible carrier for osteotropic factors such as cell adhesion molecules (e.g. fibronectin) or bone-specific growth factors.

AlphaVbeta6 integrin promotes invasion of squamous carcinoma cells through up-regulation of matrix metalloproteinase-9

The integrin alphaVbeta6 is a fibronectin receptor, which is not detectable on normal epithelium but is neo-expressed in oral epithelial dysplasia and oral squamous-cell carcinoma (SCC), suggesting a role in promoting malignant behaviour and tumour progression. We used transfection and retroviral infection to create a panel of SCC cell lines expressing various levels of alphaVbeta6 to examine this possibility. We found that increased expression of alphaVbeta6 in malignant keratinocytes up-regulates MMP-9 and MMP-2 expression and promotes invasion in an MMP-9-dependent manner. Our results suggest a possible mechanism for the involvement of alphaVbeta6 in squamous carcinoma in vivo.

Regulation of MCP-3 and BRCA2 mRNA expression levels by beta(1) integrins

The integrin cytoplasmic domain has been shown to modulate several cellular functions, including cell proliferation, adhesion, migration, and intracellular signaling. The beta(1) integrin subunits beta(1C) and beta(1A), which contain variant cytoplasmic domains, differentially affect cancer and normal cell functions. To identify target genes selectively regulated by these beta(1) cytoplasmic variants, stable cell transfectants expressing either beta(1A) or beta(1C) under the control of a doxycycline-inducible promoter were obtained using murine beta(1)-deficient GD25 cells. Screening of 1176 murine cDNAs using first-strand cDNA of mRNA isolated from either beta(1C)- or beta(1A)-expressing cells showed a striking differential expression of few genes. The differential expression of two genes, MCP-3 and BRCA2 (monocyte chemoattractant protein-3 and breast cancer susceptibility gene 2, respectively), whose products are involved, respectively, in chemotaxis and embryonic proliferation, was confirmed by Northern blot analysis. Increased MCP-3 and decreased BRCA2 mRNA levels in cells expressing beta(1C) compared to those in cells expressing beta(1A) were observed. Since beta(1C) and beta(1A) stable cell transfectants showed comparable adhesion to fibronectin, upregulation of MCP-3 and downregulation of BRCA2 mRNA levels did not appear to be due to a differential ability of the beta(1C) cells to adhere to the beta(1) ligand fibronectin. Overall, our data show that beta(1) integrin cytoplasmic domain variants control expression of downstream target genes in a differential manner without affecting cell adhesion.

Pathogenesis of rheumatoid arthritis: the role of synoviocytes

Considering the characteristics of RA synovial tissues such as marked proliferation and invasion to adjacent tissues, comparisons with transformed or neoplastic tissue are natural. RA synovial tissues or cells are not truly malignant, but they have many features of transformation, denoted as "partial transformation" in this article. These features include anchorage-independent growth, loss of contact inhibition, oncogene activation, monoclonal or oligoclonal expansion, detectable telomerase activity, and somatic gene mutations. Although it is not possible to conclude whether most of these cells are permanently changed in association with some genetic alterations or are passively changed by virtue of environmental factors (i.e., cytokine-mediated imprinting), the presence of p53 mutations in RA synovial tissues is especially persuasive. A number of transcription factors play a critical role in the activation, differentiation, and proliferation of RA synovial cells. In particular, the roles of AP-1, MAPKs, and NF-kappa B have been investigated carefully because of their ability to regulate numerous inflammation-related genes. These transcription factors also control expression and activation of matrix-degrading enzymes, including MMPs, aggrecanase, and cysteine proteases, which are the primary enzymes responsible for joint destruction. Elucidation of gene mutations and detailed signal transduction pathways that are specific to RA as well as mechanisms of action of matrix-degrading enzymes may lead to development of a novel therapy for RA. Careful mapping of cytokine networks a decade ago led to groundbreaking advances in therapy. Similarly, methodical evaluation and prioritization of intracellular targets might provide the basis for therapeutic interventions.

The fibronectin-derived antiadhesive peptides suppress the myofibroblastic conversion of rat hepatic stellate cells

We previously found that fibronectin (FN) had a functional site (YTIYVIAL sequence in the 14th type III module) suppressing the integrin-mediated cell adhesion to extracellular matrix. FN-derived peptides containing this antiadhesive site were also shown to regulate cellular processes such as proliferation, differentiation, and apoptosis. The present study shows that the FN-derived antiadhesive peptides suppress the myofibroblastic conversion of rat hepatic stellate cells (HSC). Freshly isolated HSC underwent myofibroblastic conversion during culture in the presence of FBS, as evaluated by indices representing the phenotypic activation of HSC, including increased proliferation, consumption of vitamin A-enriched lipid droplets, and expression of alpha-smooth muscle actin. However, appearance of these myofibroblastic characters was suppressed by coculturing HSC with the FN-derived antiadhesive peptides. On the other hand, the activated HSC, which had already acquired the myofibroblastic phenotype through repeated subculture, secreted FN and then stimulated matrix assembly of ED-A (+) cellular FN as well as plasma FN, while the FN-derived antiadhesive peptides inhibited them. Furthermore, the FN-derived antiadhesive peptides suppressed the integrin-mediated adhesion of the primary HSC to plasma FN and ED-A (+) cellular FN substrates. These results suggested that the FN-derived antiadhesive peptides down-regulated the myofibroblastic conversion of HSC in an indirect manner by inhibiting the integrin-mediated adhesive interaction of HSC with ED-A (+) cellular FN.

p38 mitogen-activated kinase is a bidirectional regulator of human fibroblast collagenase-1 induction by three-dimensional collagen lattices

When fibroblasts are cultured in contracting collagen matrices, matrix metalloproteinase-1 (MMP-1, collagenase-1) is induced. In the present study we demonstrate that p38alpha mitogen-activated protein kinase (p38alpha MAPK) plays a bi-directional role in the MMP-1 response to contracting floating collagen lattices (fl-coll). fl-coll, but not attached collagen lattices (att-coll), co-ordinately increased expression of MMP-1 and activities of p38alpha and MKK3/6 (MAPK kinase 3/6). However, treatment of primary fibroblasts cultured in fl-coll with increasing doses of SB203580, an inhibitor of p38alpha and p38beta, caused a bipolar pattern of MMP-1 expression. Partial inhibition of p38 MAPK activity resulted in the lowest level of MMP-1 expression, whereas total inhibition of p38 activity led to MMP-1 levels as high as in the absence of inhibitor. The activation/inhibition of p38alpha was apparently responsible for the observed phenomena, as supported by three lines of evidence. (1) p38alpha was the predominant isoform sensitive to SB203580 in primary fibroblasts. (2) Fibroblasts transfected with increasing dose of a dominant negative p38alpha (p38DN) similarly demonstrated the bipolar pattern of MMP-1 expression induced by fl-coll. (3) The bipolar MMP-1 expression occurred during the gradual, linear inhibition of p38alpha kinase activity by both inhibitors, SB203580 and p38DN. Nuclear factor-kappaB (NF-kappaB), a previously identified positive regulator of MMP-1 expression induced by fl-coll [Xu, Zutter, Santoro and Clark (1998) J. Cell Biol. 140, 709-719] was mediated by fl-coll-activated p38alpha. However, the fl-coll-induced expression of MMP-1 facilitated by p38alpha suppression was maintained independent of NF-kappaB activity, suggesting the existence of a p38alpha-dependent antagonistic pathway. We conclude that fl-coll-induced MMP-1 expression is the net outcome of opposing effects mediated by p38alpha. Therefore, the level of p38alpha kinase activity may provide a fine-tuned control of MMP-1 gene expression in response to biomechanical signals.

Epithelium-fibroblast interactions in response to airway inflammation

Dramatic changes to the architecture of the airway walls have been commonly described in the airways of patients with asthma, cystic fibrosis (CF) and chronic obstructive pulmonary disease (COPD). Much research has focused on how airway inflammation drives these structural changes, particularly in terms of the mechanisms/mediators that are involved, and a number of parallels are observed between the disease phenotypes. For example, the increased deposition of extracellular matrix (ECM) at focal sites in the airway wall is seen in asthma and all interstitial lung diseases that involve fibrosis. In addition, increased expression of a number of well characterized cytokines and growth factors, such as TGF-beta and epidermal growth factor (EGF) have been demonstrated in these diseases. However, the role of the lesser-known cytokines, including the leukaemia inhibitory factor (LIF) and other members of the IL-6 family of cytokines in the pathogenesis of airway remodelling and fibrosis is largely unknown. However, the use of genetic manipulation in vivo and more specific inhibitors/antibodies in vitro has now provided increasing evidence to support the hypothesis that a complex interaction exists between these cytokines, ECM and integrins in regulating the function of both epithelial cells and fibroblasts.

Urokinase receptor and fibronectin regulate the ERK(MAPK) to p38(MAPK) activity ratios that determine carcinoma cell proliferation or dormancy in vivo

We discovered that a shift between the state of tumorigenicity and dormancy in human carcinoma (HEp3) is attained through regulation of the balance between two classical mitogen-activated protein kinase (MAPK)-signaling pathways, the mitogenic extracellular regulated kinase (ERK) and the apoptotic/growth suppressive stress-activated protein kinase 2 (p38(MAPK)), and that urokinase plasminogen activator receptor (uPAR) is an important regulator of these events. This is a novel function for uPAR whereby, when expressed at high level, it enters into frequent, activating interactions with the alpha5beta1-integrin, which facilitates the formation of insoluble fibronectin (FN) fibrils. Activation of alpha5beta1-integrin by uPAR generates persistently high level of active ERK necessary for tumor growth in vivo. Our results show that ERK activation is generated through a convergence of two pathways: a positive signal through uPAR-activated alpha5beta1, which activates ERK, and a signal generated by the presence of FN fibrils that suppresses p38 activity. When fibrils are removed or their assembly is blocked, p38 activity increases. Low uPAR derivatives of HEp3 cells, which are growth arrested (dormant) in vivo, have a high p38/ERK activity ratio, but in spite of a similar level of alpha5beta1-integrin, they do not assemble FN fibrils. However, when p38 activity is inhibited by pharmacological (SB203580) or genetic (dominant negative-p38) approaches, their ERK becomes activated, uPAR is overexpressed, alpha5beta1-integrins are activated, and dormancy is interrupted. Restoration of these properties in dormant cells can be mimicked by a direct re-expression of uPAR through transfection with a uPAR-coding plasmid. We conclude that overexpression of uPAR and its interaction with the integrin are responsible for generating two feedback loops; one increases the ERK activity that feeds back by increasing the expression of uPAR. The second loop, through the presence of FN fibrils, suppresses p38 activity, further increasing ERK activity. Together these results indicate that uPAR and its interaction with the integrin should be considered important targets for induction of tumor dormancy.

The angiogenic factors Cyr61 and connective tissue growth factor induce adhesive signaling in primary human skin fibroblasts

The angiogenic inducers cysteine-rich angiogenic protein 61 (Cyr61) and connective tissue growth factor (CTGF) are structurally related, extracellular matrix-associated heparin-binding proteins. Both can stimulate chemotaxis and promote proliferation in endothelial cells and fibroblasts in culture and induce neovascularization in vivo. Encoded by inducible immediate early genes, Cyr61 and CTGF are synthesized upon growth factor stimulation in cultured fibroblasts and during cutaneous wound healing in dermal fibroblasts. Recently, we have shown that adhesion of primary human fibroblasts to immobilized Cyr61 is mediated through integrin alpha(6)beta(1) and cell surface heparan sulfate proteoglycans (HSPGs) (Chen, N., Chen, C.-C., and Lau, L.F. (2000) J. Biol. Chem. 275, 24953-24961), providing the first demonstration of an absolute requirement for HSPGs in integrin-mediated cell attachment. We show in this study that CTGF also mediates fibroblast adhesion through the same mechanism and demonstrate that fibroblasts adhesion to immobilized Cyr61 or CTGF induces distinct adhesive signaling responses consistent with their biological activities. Compared with fibroblast adhesion to fibronectin, laminin, or type I collagen, cell adhesion to Cyr61 or CTGF induces 1) more extensive and prolonged formation of filopodia and lamellipodia, concomitant with formation of integrin alpha(6)beta(1)-containing focal complexes localized at leading edges of pseudopods; 2) activation of intracellular signaling molecules including focal adhesion kinase, paxillin, and Rac with similar rapid kinetics; 3) sustained activation of p42/p44 MAPKs lasting for at least 9 h; and 4) prolonged gene expression changes including up-regulation of MMP-1 (collagenase-1) and MMP-3 (stromelysin-1) mRNAs and proteins sustained for at least 24 h. Together, these results establish Cyr61 and CTGF as bona fide adhesive substrates with specific signaling capabilities, provide a molecular basis for their activities in fibroblasts through integrin alpha(6)beta(1) and HSPG-mediated signaling during attachment and indicate that these proteins may function in matrix remodeling through the activation of metalloproteinases during angiogenesis and wound healing.

Structure-function and pathogenesis studies of Streptococcus pyogenes extracellular cysteine protease

Replacement of the single cysteine residue (C192) with serine in the Streptococcus pyogenes extracellular cysteine protease (SCP) prevented auto-catalytic processing of the 40-kDa zymogen to the 28-kDa mature form and eliminated proteolytic activity. SCP incubated with human endothelial cells induced a time- and concentration-dependent increase in a 66-kDa gelatinase/type IV collagenase in culture supernatants. Activation of this gelatinase/collagenase may contribute to endothelial cell damage, tissue destruction, and hemodynamic derangement observed in some patients with severe, invasive S. pyogenes infection.

An in vitro Model for Studying Mechanisms Underlying Synoviocyte-Mediated Cartilage Invasion in Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a chronic inflammatory disease of joints involving the pathological development of an invasive and destructive pannus tissue which contributes to the loss of cartilage and bone. To further analyze the process of cartilage degradation and invasion, we have developed an in vitro model composed of cartilage matrix and synoviocytes (isolated from RA pannus tissue, as well as normal synovial membrane). The matrix is derived from pig articular cartilage and contains collagen type II and proteoglycans and is similar in composition to human cartilage. Data generated from this model reveal that synoviocytes isolated from RA pannus tissue invaded cartilage matrix in a manner which directly correlated with the severity of the disease. Analysis of mechanisms associated with the invasive process demonstrate that highly invasive RA synoviocytes maintain a round morphology during attachment and spreading on cartilage matrix, compared with their normal counterparts. Furthermore, the level of secretion of matrix metalloproteinase (MMP) activity was shown to correlate with the RA phenotype, which could be modulated with a novel MMP inhibitor. Normal synoviocytes could be "converted" to an RA phenotype by specific inflammatory cytokines, such that invasion of cartilage matrix was augmented by culturing these cells in the presence of 5 U/ml IL-1b or 18 U/ml TGFb. Invasion was inhibited by 150 U/ml TNFa, and unaffected by 100 ng/ml PDGF. In addition, synovial fluid from RA patients induced invasion of normal synoviocytes, in a concentration dependent manner, from 150% to 460%; however, synovial fluid from another inflammatory arthritidy (Crohn's) did not augment invasion to the same degree. Moreover, this "conversion effect" appears to be specific for synoviocytes, since similar effects could not be achieved with human skin fibroblasts. This in vitro model of synoviocyte-mediated cartilage invasion allows for further molecular characterization of the invasive properties of the synoviocyte which contribute to RA.

Altered processing of fibronectin in mice lacking heparin. a role for heparin-dependent mast cell chymase in fibronectin degradation

We have previously generated a mouse strain with a defect in its heparin biosynthesis by targeting the gene for N-deacetylase/N-sulfotransferase-2 (NDST-2). The NDST-2(-/-) mice show reduced levels of various mast cell mediators such as histamine and various heparin-binding mast cell proteases, including chymases, tryptases, and carboxypeptidase A. In this work we have addressed the possible functional consequences of the lack of sulfated heparin. Peritoneal cells were harvested from normal and NDST-2(-/-) mice. After culturing the cells, conditioned media were collected and were subjected to SDS-polyacrylamide gel electrophoresis under reducing conditions. Several differences in the protein patterns were observed, including the presence of large amounts of a approximately 250-kDa protein in medium from NDST-2(-/-) mice that was absent in normal controls. Peptide microsequencing revealed identity of this protein with fibronectin. Western blot analysis showed the presence of fibronectin degradation products in cell cultures from normal mice, which were absent in cultures from NDST-2(-/-) animals. Further experiments showed that the degradation of fibronectin observed in cell cultures from NDST-2(+/+) mice was catalyzed by mast cell chymase in a strongly heparin-dependent manner. This report thus indicates a biological function for chymase/heparin proteoglycan complexes in fibronectin turnover.

Matrix metalloproteinases and their inhibitors in oral lichen planus

BACKGROUND

Oral lichen planus (OLP) is characterized by a sub-epithelial lymphocytic infiltrate, basement membrane (BM) disruption, intra-epithelial T-cell migration and apoptosis of basal keratinocytes. BM damage and T-cell migration in OLP may be mediated by matrix metalloproteinases (MMPs).

METHODS

We examined the distribution, activation and cellular sources of MMPs and their inhibitors (TIMPs) in OLP using immunohistochemistry, ELISA, RT-PCR and zymography.

RESULTS

MMP-2 and -3 were present in the epithelium while MMP-9 was associated with the inflammatory infiltrate. MMP-9 and TIMP-1 secretion by OLP lesional T cells was greater than OLP patient (p < 0.01) and healthy control subject (p < 0.001) peripheral blood T cells. MMP-9 and TIMP-1 mRNA levels were greater in OLP lesional T cells compared with healthy control subject peripheral blood T cells p < 0.01). Tumor necrosis factor (TNF)-alpha upregulated OLP lesional T-cell MMP-9 (not TIMP-1) mRNA and secretion (p < 0.05). The in vitro activation rate of MMP-9 from OLP lesional T cells was greater than that from OLP peripheral blood T cells (p < 0.05).

CONCLUSION

T-cell-derived MMP-9 may be involved in the pathogenesis of OLP. Relative over-expression of MMP-9 (compared with TIMP-1) may cause BM disruption and facilitate intra-epithelial T-cell migration in OLP.