胸腺上皮肿瘤组织中基质金属蛋白酶-2活性与Ⅰ型膜型基质金属蛋白酶 mRNA表达的相关性

目的探讨胸腺瘤和胸腺癌中基质金属蛋白酶（MMP）-2、Ⅰ型膜型（MT1）-MMP、金属蛋白酶组织抑制剂（TIMP）-2mRNA的表达和MMP-2蛋白活性的关系。方法分别用real-time逆转录．聚合酶链反应（RT-PCR,Taqman法）、明胶酶谱法和Filmin situ gelatin-Zymography（FIZ）对正常的胸腺组织（2例）、胸腺瘤（12例）和胸腺癌（2例）患者的新鲜肿瘤组织中MMP-2、MT1-MMP、TIMP-2mRNA的表达,pro-MMP-2的活性率及活性蛋白的定位进行测定。结果MMP-2、MT1-MMP及TIMP-2mRNA在Ⅰ期与Ⅱ期和Ⅲ期与Ⅳ期中的表达差异均无统计学意义（P〉0．05）,在Ⅰ～Ⅱ期与Ⅲ～Ⅳ期和胸腺癌3组中差异均有统计学意义（P〈0．01）。在AB、B1型（混合型和淋巴细胞为主型）与B2、B3型（皮质型和多角细胞为主型）以及胸腺癌3组中差异均有统计学意义（P〈0．05）。MMP-2的蛋白活性率（MMP-2／pro—MMP-2＋MMP-2）在Ⅰ～Ⅱ期、Ⅲ～Ⅳ期和胸腺癌各组中差异有统计学意义（P〈0．05）,在AB、B1型与B2、B3型以及胸腺癌各组中的差异均具有统计学意义（P〈0．05）。胸腺瘤各期及各型中MT1-MMP、TIMP-2mRNA与MMP-2蛋白活性表达均呈正相关,且相关程度相似（r=0．7235、r=0．7647、P〈0．005）。MMP-9的蛋白表达在各组间差异均无统计学意义。结论MMP-2、MT1-MMP及TIMP-2的mRNA表达与胸腺瘤临床分期、病理分型相关,MMP-2的活性与MT1-MMP和TIMP-2的表达升高正相关。推测MT1-MMP通过TIMP-2对MMP-2的激活起促进作用。     

Regulation of matrix metalloproteinase-2(gelatinase A, MMP-2), membrane-type matrixmetalloproteinase-1 (MT1-MMP) and tissue inhibitorof metalloproteinases-2 (TIMP-2) expression byelastin-derived peptides in human HT-1080 fibrosarcoma cell line

Soluble kappa-elastin peptides were shown to stimulate the expression of MMP-2 (but not MMP-9) byhuman fibrosarcoma HT-1080 cells, both at the protein and mRNA levels; maximal effect being observedat a concentration of 25 mg/ml of kappa-elastin. The stimulatory effect could be reproduced using Val-Gly-Val-Ala-Pro-Gly (VGVAPG) peptide, an elastin-derived hydrophobic hexapeptide which represented theelastin receptor binding sequence of tropoelastin. Furthermore, treatment of cells with lactose (30 mM),which dissociated 67-kDa elastin binding protein (EBP) from cell surfaces, completely abolished this effect,suggesting that the elastin receptor could mediate such a response. Using a specific monoclonal antibody,67-kDa EBP was detected in HT-1080 membrane preparations by Western immunoblotting. Following treat-mentwith 25 mg/ml kappa-elastin or 200 mg/ml VGVAPG, increased levels of the active 62-kDa form ofMMP-2 were found in HT-1080 cell extracts. Stimulation of MT1-MMP mRNA expression by treatmentwith elastin-derived peptides (EDPs) was shown by competitive polymerase chain reaction (PCR). A reversezymography analysis revealed that EDPs also stimulated TIMP-2 (but not TIMP-1) production by HT-1080cells. Competitive PCR confirmed increased TIMP-2 mRNA expression by such treatment. These resultssuggest that occupancy of the 67-kDa elastin receptor by elastin-derived peptides enhanced both expressionand activation of proMMP-2 and consequently, could promote the invasive/metastatic ability of tumor cellsexpressing this receptor. ©Kluwer Academic Publishers     

Cell membrane-associated MT1-MMP dependent activation of MMP-2 in SiHa (human cervical cancer) cells.

Among the soluble MMPs, MMP-2 (gelatinase A) is particularly important in the invasive property of tumor cells. Cell membrane-associated MMP-2 activation is one of the challenging areas in tumor biology. In the present communication, we studied the membrane dependent activation of MMP-2 in SiHa cells. METHODS: Activation of pro-MMP-2 by membrane fraction, membrane extract, and live SiHa cells was studied by gelatin zymography. The role of MT1-MMP in MMP-2 activation was studied by incubating SiHa cells and cell membrane fractions with anti-MT1-MMP antibody. RESULTS: Activation of purified pro-MMP-2 by membrane fraction isolated from SiHa cells, by SiHa cell membrane extract and by SiHa cells, pro-MMP-2 from Con A treated HT-1080 conditioned medium by SiHa cells, and pro-MMP-2 from serum free culture medium of SiHa cells and cervical tissue homogenate by SiHa cell membrane fraction was shown by gelatin zymography. SiHa membrane fraction activated only pro-MMP-2 from purified MMP-9/MMP-2 mixture, indicating that the activation is specific for MMP-2. Inhibition of MMP-2 activation in the presence of anti-MT1-MMP antibody strongly indicated that the cell membrane mediated MMP-2 activation is MT1-MMP dependent. Immunocytochemistry of SiHa cells demonstrated expression of MT1-MMP at focal points. Invasion assay showed that invasiveness of anti-MT1-MMP antibody treated SiHa cells through Matrigel was drastically reduced compared to control SiHa cells. CONCLUSIONS: Our findings furnish an example of the cell membrane-associated MT1-MMP mediated MMP-2 activation in SiHa cells and suggest that this MT1-MMP mediated MMP-2 activation is of importance in tumor invasion and metastasis. This MT1-MMP mediated MMP-2 activation on tumor cell surface could be a realistic target for managing metastatic diseases.     

Expression of MMP-2 and MMP-9, their inhibitors, and the activator MT1-MMP in primary breast carcinomas.

Enhanced expression of the type IV collagenases MMP-2 and MMP-9, or lack of their inhibitors TIMP-1 and TIMP-2, has been associated with tumour invasion and metastatic potential in several experimental models. Regulation of enzyme activity is clearly a key step in tumour invasion, and recently a potent activator of MMP-2, the membrane-associated MT1-MMP, has been described and characterized. Using an immunohistochemical approach, this study has examined the expression and distribution of the type IV collagenases, their inhibitors, and the activator MT1-MMP, in a series of 79 infiltrating ductal carcinomas (IDCs), 8 tubular carcinomas, and 27 infiltrating lobular carcinomas (ILCs). MMP-2 and MT1-MMP were expressed in more than 90 per cent of all carcinomas, with predominantly stromal and tumour cell cytoplasmic staining. However, reactivity localized on tumour cell membranes was recorded for MMP-2 in 34 per cent of cases with a monoclonal antibody and 55 per cent of cases with a polyclonal antibody, and for MT1-MMP in 68 per cent of tumours. In each case, this pattern of staining was significantly associated with the presence of lymph node metastasis (p=0.001, p=0. 008, and p=0.1, respectively). Both tumour cell and stromal staining was observed for TIMP-2, but there was no correlation with metastatic status. The 92 kD gelatinase MMP-9 was expressed by 68 per cent of carcinomas, either in the stromal compartment or by tumour cells. There was a highly significant correlation between the expression pattern of MMP-9 and tumour type, with ILCs displaying greater frequency and more homogeneous cytoplasmic staining than IDCs (p=0.0004). Staining for TIMP-1 was seen in the stroma and also in relation to small blood vessels, with more than 90 per cent of tumours showing this staining pattern using a polyclonal antibody. This study indicates distinct patterns of expression for different MMPs and demonstrates the potential importance of the MMP-2/MT1-MMP system in breast tumour progression. The association of MMP-9 with the infiltrating lobular phenotype may reveal novel mechanisms of control for this metalloproteinase.     

MMP-2、MT1-MMP、TIMP-2在胎膜早破中的作用

目的通过检测不同情况产妇胎膜组织中基质金属蛋白酶2(matrix metalloproteinase-2,MMP-2)及其激动剂(membrane type 1-matrix metalloprotease MT1-MMP)和其特异性组织抑制剂(tissue inhibitor of matrix metalloproteinases-2,TIMP-2)的表达,以探讨MMP-2在胎膜早破中的作用.方法 RT-PCR和S-P法对20例自发性胎膜早破患者、20例正常分娩产妇的胎膜组织中MMP-2、TIMP-2 mRNA和MT1-MMP蛋白的表达及定位进行检测.结果 (1)MMP-2 mRNA在胎膜早破组表达明显高于正常分娩组,两者比较,差异有显著性(P＜0.05).(2)TIMP-2 mRNA在正常分娩组表达高于胎膜早破组,两者比较差异有显著性(P＜0.05).(3)MT1-MMP蛋白在胎膜早破组表达明显高于正常分娩组,两者比较,差异有显著性(P＜0.05).MT1-MMP在羊膜细胞和绒毛膜的滋养细胞内表达.主要在细胞浆内表达.结论胎膜早破中,MMP-2及其人调节剂的表达失调将可能导致胎膜基质的降解增加并最终导致胎膜的破裂.     

Co-ordinated expression of MMP-2 and its putative activator, MT1-MMP, in human placentation

The spatial expression of mRNA for matrix metalloproteinase 2 (MMP-2), its putative activator, the membrane-type 1 matrix metalloproteinase (MT1-MMP), and the MMP-2 substrate type IV collagen was investigated in human placentas of both normal and tubal ectopic pregnancies and in cyclic endometrium using in-situ hybridization. Cytokeratin staining applied to adjacent sections was used to identify epithelial and trophoblast cells. In both normal and tubal pregnancies MT1-MMP, MMP-2 and type IV collagen mRNA were highly expressed and co-localized in the extravillous cytotrophoblasts of anchoring villi, in cytotrophoblasts that had penatrated into the placental bed and in cytotrophoblastic cell islands. In addition, the decidual cells of normal pregnancies in some areas co-expressed MT1-MMP and MMP-2 mRNA, with moderate signals for both components. Fibroblast-like stromal cells in tubal pregnancies were positive for MMP-2 mRNA but generally negative for MT1-MMP mRNA. The consistent co-localization of MT1-MMP with MMP-2 and type IV collagen in the same subset of cytotrophoblasts strongly suggests that all three components co-operate in the tightly regulated fetal invasion process. The co-expression of MT1-MMP and MMP-2 mRNA in some of the decidual cells indicates that these cells are also actively involved in the placentation process.      

MT1-MMP correlates with MMP-2 activation potential seen after epithelial to mesenchymal transition in human breast carcinoma cells

We have previously reported that human breast carcinoma (HBC) cell lines expressing the mesenchymal intermediate filament protein vimentin (VIM+) are highly invasive in vitro, and highly metastatic in nude mice when compared to their VIM– counterparts. Since only VIM+ cell lines can be induced to activate matrix metalloproteinase-2 (MMP-2) upon stimulation with Concanavalin A (Con A), we have examined here membrane type 1 MMP (MT1-MMP), a cell surface activator of MMP-2. Northern analysis reveals baseline expression of MT1-MMP in five of the six VIM+ cell lines studied (MDA-MB-231, MDA-MB-435, BT-549, Hs578T, MCF-7ADR), each of which showed variable activation of exogenous MMP-2 after treatment with Con A. In contrast, the four VIM–, poorly invasive HBC cell lines studied (MCF-7, T47D, MDA-MB 468, ZR-75-1) lacked baseline MT1-MMP mRNA expression, and showed no induction of either MT1-MMP expression or MMP-2-activation with Con A. Such differential MT1-MMP expression was confirmed in vivo using in situ hybridization analysis of nude mouse tumor xenografts of representative cell lines. Western analysis of the MDA-MB-231 cells revealed baseline membrane expression of a 60 kDa species, which was strongly induced by Con A treatment along with a weaker band co-migrating with that from MT1-MMP-transfected COS-1 cells (63 kDa), presumably representing latent MT1-MMP. MT1-MMP immunofluorescence strongly decorated Con A-stimulated MDA-MB-231 cells in a manner consistent with membranous staining, but did not decorate the unstimulated MDA-MB-231 cells or MCF-7 cells under either condition. Collectively, the results suggest the constitutive production of active MT1-MMP which is unavailable for either MMP-2 activation or immuno-decoration until Con A treatment. Since VIM expression arises by virtue of the so-called epithelial to mesenchymal transition (EMT) in invasive embryonic epithelia, we propose that this represents a major metastasis mechanism in breast carcinomas. MT1-MMP on the surface of such ÔfibroblastoidÕ carcinoma cells may mediate a paracrine loop for the utilization of stromally produced MMP-2, and contribute to the poorer survival associated with VIM+ breast carcinomas.     

High levels of MMP-2, MMP-9, MT1-MMP and TIMP-2 mRNA correlate with poor survival in ovarian carcinoma

The object of this study was to analyze the potential association between the expression of MMP-2, MMP-9, MT1-MMP and TIMP-2, and disease outcome in advanced-stage ovarian carcinomas. Sections from 70 paraffin-embedded blocks (36 primary ovarian carcinomas and 34 metastatic lesions) from 45 patients diagnosed with advanced stage ovarian carcinomas (FIGO stages III–IV) were studied using mRNA in situ hybridization (ISH) technique. Patients were divided retrospectively in two groups based on disease outcome. Long-term survivors (21 patients) and short-term survivors (24 patients) were defined using a double cut-off of 36 months for disease-free survival (DFS) and 60 months for overall survival (OS). Mean follow-up period for patients that were diagnosed with advanced-stage carcinoma was 70 months. The mean values for DFS and OS were 109 and 125 months for long-term survivors, as compared to 3 and 21 months for short-term survivors, respectively. Intense mRNA signals were detected more frequently in tumor cells of short-term survivors with use of all four probes. Comparable findings were observed in peritumoral stromal cells with ISH for MMP-2, MMP-9 and TIMP-2 mRNA. Notably, primary tumors with intense mRNA signal for TIMP-2 (No = 14) were uniformly associated with a fatal outcome. In univariate analysis of primary tumors, mRNA levels of TIMP-2 in stromal cells (P = 0.0002), as well as for MMP-9 (P = 0.012) and TIMP-2 (P = 0.02) in tumor cells, correlated with poor outcome. In univariate analysis of metastatic lesions, mRNA levels of TIMP-2 in stromal cells (P = 0.031), as well as for MMP-2 (P = 0.027) and MT1-MMP (P = 0.008) in tumor cells, correlated with poor outcome. Interestingly, the presence of MT1-MMP in stromal cells correlated with longer survival (P = 0.025). In a multivariate analysis of ISH results for primary tumors, TIMP-2 levels in stromal cells (P = 0.006) and MMP-9 levels in tumor cells (P = 0.011) retained their predictive value. We conclude that MMP-2, MMP-9, MT1-MMP and TIMP-2 are valid markers of poor survival in advanced-stage ovarian carcinoma. This revised version was published online in July 2006 with corrections to the Cover Date.     

Survivin, MMP-2, MT1-MMP, and TIMP-2: their impact on survival, implantation, and proliferation of endometriotic tissues

In order to study survivin, matrix metalloproteinases (MMP-2), membranous type 1 matrix metalloproteinase (MT1-MMP), and tissue inhibitor metalloproteinase-2 (TIMP-2) expression immunohistochemically in endometriotic tissues and normal endometrium, our retrospective study considered 194 patients affected by endometriosis and 71 patients with normal endometrium. Tissue microarrays were created from paraffin-embedded blocks; immunohistochemistry was used to assess protein expression. In endometriotic tissues, survivin was expressed at a higher level than in normal endometrium; its glandular expression level was higher in non-ovarian than in ovarian endometriotic tissues and lower in stromal components. Endometrial tissues from women without endometriosis and endometriotic tissues had different matrix metalloproteinase expression profiles. MMP-2 and MT1-MMP correlated with TIMP-2 in endometriotic tissues. Furthermore, in endometriotic tissues, expression of survivin, aurora B kinase, and Ki-67 showed a significant positive correlation, which indicates a role in cellular proliferation that could be closely linked to its anti-apoptotic activity in endometriosis development. Our results imply a role for matrix metalloproteinases in endometriosis invasiveness; correlation of their expression with that of TIMP-2 underscores its possible key regulatory role.     

E6/E7 oncoproteins of high risk HPV-16 upregulate MT1-MMP,MMP-2 and MMP-9 and promote the migration of cervical cancer cells

Background: E6 and E7 of high risk human papillomavirus 16 (HPV16) were reported to correlate with the cervical cancer (CC). And the presence of matrix metalloproteinases (MMPs) has also been indicated to be associated with CC. Methods: The present study investigated the expression of MMPs (MT1-MMP, MMP-2 and MMP-9) in CC cells with HPV16-E6/E7 oncoprotein(s) negative or positive, and then determined the regulation of HPV16-E6/E7 oncoproteins on the expression of MMPs (MT1-MMP, MMP-2 and MMP-9) and the migration of cervical cancer Caski and SiHa cells with RNAi technology. Results: It was demonstrated that the overexpression or the knockdown of HPV16-E6/E7 promoted or reduced MT1-MMP, MMP-2 and MMP-9 in CC cells. And the HPV16-E6, -E7 or -E6E7 influenced the migration of CC cells. The overexpression or the knockdown of them promoted or inhibited the migration of C33A or Caski/SiHa cells. Moreover, the chemical inhibition of MMP-2 or MMP-9 significantly reduced the migration of CC Caski or SiHa cells. Conclusions: Our results demonstrated that the E6-HPV16 or E7-HPV16 promoted the activity of MMP-2/9, and contributed to the migration of cervical cells.     

Soluble membrane-type 1 matrix metalloproteinase (MT1-MMP) and gelatinase A (MMP-2) in induced sputum and bronchoalveolar lavage fluid of human bronchial asthma and bronchiectasis

The aim of this study was to investigate the involvement of the MT1-MMP/MMP-2 cascade in induced sputum (IS) and bronchoalveolar lavage fluid (BALF) from bronchial asthma (BA) and bronchiectasis (BE) patients and healthy controls. The molecular forms and cellular origins of MT1-MMP and MMP-2 were determined by Western immunoblotting, immunohistochemistry and in situ hybridization. Elevated levels of soluble activated and autocatalyzed MT1-MMP species as well as activated forms of MMP-2 in IS and BALF samples from BA and BE patients were evidenced. The activation degrees of soluble MT1-MMP and MMP-2 were significantly correlated in BA and BE IS and BALF. Only low levels of both these MMPs were observed in healthy control IS and BALF. The co-expression of MMP-2 with MT1-MMP was evidenced by double immunostaining in bronchial epithelial cells, submucosal glandular cells, smooth muscle cells and monocyte/macrophages. The MT1-MMP/MMP-2 cascade is present and active in human inflammatory lung disease fluid and tissue samples. This cascade seemingly reflects the active destructive phases of these chronic lung diseases.     

胰腺癌MT1-MMP和MMP-2表达与神经浸润、转移及预后关系

目的 探讨膜型基质金属蛋白酶-1(MTI-MMP)和基质金属蛋白酶-2(MMP-2)在胰腺癌中的表达及其与神经浸润、转移及预后的关系.方法 采用免疫组化双标技术检测47例胰腺癌组织中MT1-MMP和MMP-2的表达,并以S-100标记神经纤维,观察MT1-MMP和MMP-2的阳性表达率与胰腺癌神经浸润、转移及预后的关系.结果 MT1-MMP和MMP-2在有神经浸润的胰腺癌组织中阳性表达率均明显高于无神经浸润者(χ2=4.24,11.57;P<0.05);MT1-MMP和MMP-2的表达与胰腺癌转移、临床分期和预后有关(χ2=7.42,7.26;11.85,12.69;6.69,7.86;P<0.01),而与性别、年龄、肿瘤大小及组织学分级无关(χ2=0.05～4.29;P>0.05);胰腺癌组织中MT1-MMP和MMP-2的表达呈正相关(r＝0.585,P<0.01).结论MT1-MMP和MMP-2在胰腺癌的神经浸润、转移过程中可能发挥协同作用;MT1-MMP和MMP-2的表达水平与胰腺癌临床分期和预后密切相关,可作为反应胰腺癌生物学行为的重要指标.     

Expression of matrix metalloprotease-2 (MMP-2) and the activator membrane type 1 (MT1-MMP) in canine mammary carcinomas

An immunohistochemical approach was used to examine the expression of MMP-2 and the activator MT1-MMP in a series of 50 canine mammary carcinomas of different histotype and stage. MMP-2 and MT1-MMP were mainly expressed in the cytoplasm of carcinoma cells and in fibroblasts. Immunolabelling for both MMP-2 and MT1-MMP was also seen on the tumour cell membranes. This labelling pattern showed no significant association with either the histological sub-type or stage of the carcinomas. Therefore, although distinct patterns of expression of MMP-2 and MT-MMP1 were shown by these carcinomas, functional studies by means of zymography would be required to provide useful information on tumour behaviour.     

In vivo activation of gelatinase B/MMP-9 by trypsin in acute pancreatitis is a permissive factor in streptozotocin-induced diabetes

Matrix metalloproteinases, in particular gelatinase B/MMP-9, are key mediators in autoimmune diseases like multiple sclerosis and rheumatoid arthritis, but their pathogenic roles in diabetes are not well established. Gelatinase B has previously been shown to be upregulated in pancreas tissue from patients with acute and chronic pancreatitis and was suggested to exacerbate diabetes by cleaving insulin. In this study, the role of gelatinase B in diabetes was investigated using two streptozotocin-induced animal models of type I diabetes. In both a hyperacute and a subacute model, gelatinase B upregulation was found to be associated with disease activity. However, gelatinase B deficiency did not significantly protect against diabetes development, and wild-type and gelatinase B-deficient animals behaved similarly in terms of beta-cell apoptosis or necrosis. The fact that gelatinase B was found almost exclusively as the inactive pro-enzyme in most of the streptozotocin-induced diabetic animals may explain the lack of a gelatinase B effect. On the contrary, gelatinase B was completely activated in a minority (15%) of wild-type animals. This coincided with exocrine pancreatic inflammation, as revealed by the presence of active trypsin. The discovery of in vivo activation of progelatinase B by trypsin in acute pancreatitis is extended in a model of caerulein-induced pancreatitis. In the latter model, trypsinogen activation is systematically achieved and gelatinase B is found in its active form. In conclusion, gelatinase B itself is not a causative factor but, when activated by endogenous trypsin, is a permissive factor for insulin degradation and diabetes.     

(-)Epigallocatechin-3-gallate directly inhibits MT1-MMP activity,leading to accumulation of nonactivated MMP-2 at the cell surface

Consumption of green tea has been associated with prevention of cancer development, metastasis, and angiogenesis. Given the crucial role of the matrix metallo-proteinase-2 (MMP-2) on the degradation of the extracellular matrix instrumental to invasion, we examined the effect of the main flavanol present, (-)epigallocatechin-3-gallate (EGCG), on membrane-type 1 MMP (MT1-MMP), the receptor/activator of MMP-2. In-solution fluorimetric assay with activated MT1-MMP and gelatin-zymography with MT1-MMP catalytic domain alone and pro-MMP-2 activation by the same domain revealed dose-dependent inhibition of MT1-MMP at EGCG concentrations slightly lower than that reported to inhibit MMP-2 and MMP-9. Cytofluorimetry and immunolocalization revealed that EGCG does not impair MT1-MMP/TIMP-2/MMP-2 presence on the cell membrane. In the membrane extract of HT-1080 human fibrosarcoma cells, 10 micro M EGCG caused a strong increase in MT1-MMP level and accumulation of pro-MMP-2 while leaving activated MMP-2 unchanged. EGCG thus exerts inhibition of MT1-MMP, which restrains activation of MMP-2; this may confer the antiangiogenic and antimetastatic activity associated with green tea.     

Expression of MMP2, MMP9, MT1-MMP, TIMP1, and TIMP2 mRNA in valvular lesions of the heart

Matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) play an important role in several diseases. This study was undertaken to investigate the mRNA synthesis of MMP2, MMP9, membrane-type 1 (MT1)-MMP, and matrix metalloproteinase inhibitors TIMP1 and TIMP2 by in situ hybridization in a set of heart mitral and aortic valves operatively removed due to degenerative or inflammatory valvular diseases. The material consisted of 21 valves, eight with endocarditis and 13 with a degenerative valvular disease. The samples were studied by in situ hybridization with specific probes for MMP2, MMP9, MT1-MMP, TIMP1, and TIMP2. Synthesis of MMP2 mRNA was found in seven valves, five with endocarditis and two with degenerative valvular disease. Signals for MMP9 mRNA were found in two cases with endocarditis and five cases with degenerative valvular disease. No signal for MT1-MMP mRNA was found in the lesions. TIMP1 mRNA, on the other hand, was found in 17 cases, both endocarditis and degenerative valvular disease. TIMP2 mRNA was found in three cases of endocarditis. The signals for MMP2, MMP9, TIMP1, and TIMP2 mRNA were localized in endothelial cells and in fibroblast-like cells expressing alpha-smooth muscle actin, thus showing myofibroblast-type differentiation. The results show that matrix metalloproteinases MMP2 and MMP9, and matrix metalloproteinase inhibitors TIMP1 and TIMP2 mRNAs are synthesized in diseased valves and suggest that they may contribute to matrix remodelling in valvular disease.