The distribution of matrix metalloproteinases and tissue inhibitors of metalloproteinases in the lungs of congenital diaphragmatic hernia patients and age-matched controls

AIMS: In congenital diaphragmatic hernia (CDH), the pathogenesis of abnormal pulmonary morphology is still incompletely understood. Matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) are known to play an important role in the turnover of the extracellular matrix (ECM) during development and in remodelling of tissue. The aim of this study was to investigate differences in the expression of MMPs and TIMPs between CDH lungs and controls, against the background of the abnormal pulmonary vasculature in CDH. METHODS: We studied 12 lungs of term CDH patients who died < 24 h after birth and 11 normal age-matched control lungs, by immunohistochemistry with antibodies against human MMP-1, -2, -9, TIMP-1 and -2. RESULTS: There was a clear increase in the number of MMP-1-reactive capillaries and fibroblasts in CDH lungs compared with controls. In contrast, TIMP-2 reactivity in these structures was decreased in CDH lungs. The arterial endothelium and medial smooth muscle expressed MMP-2, -9 and TIMP-2 in both CDH and control lungs. In small arteries (< 100 microm in diameter), the positive surface area of MMP-2, -9 and TIMP-2 was significantly larger in CDH lungs than in controls. There was no difference in the distribution and expression of TIMP-1 between CDH lungs and normal controls. CONCLUSION: The differences in staining pattern of MMPs and TIMPs between normal and CDH lungs suggest that these enzymes might play a role in the abnormal remodelling of the interstitium and the pulmonary arteries in CDH lungs. This could contribute to our understanding of the abnormal lung morphology and the occurrence of pulmonary hypertension, which forms one of the major obstacles to the successful treatment of these patients.     

Gelatinases and their tissue inhibitors during human ovulation: increased expression of tissue inhibitor of matrix metalloproteinase-1

Remodelling of the extracellular matrix (ECM) of the follicular wall by matrix metalloproteinases (MMPs) and tissue inhibitors of matrix metalloproteinases (TIMPs) has been suggested to be crucial in ovulation. To investigate the expression of the gelatinases, MMP-2 and MMP-9, together with their inhibitors, TIMP-2 and TIMP-1, in the perifollicular ovarian stroma from women just before and during ovulation, we obtained biopsies of the stroma adjacent to the leading follicle. Laparoscopic surgery was performed either before the LH peak or at any of three intervals after ovulation triggering by hCG. Immunoblotting, immunohistochemistry and quantitative RT-PCR were performed. All four proteins were expressed by immunoblots, with no detectable changes in the expression of MMP-2, MMP-9 and TIMP-2. Scattered immunostaining for MMP-9 and TIMP-2 was seen, and MMP-2 was demonstrated in a concentric layer. A significant increase in TIMP-1 protein and mRNA was seen during the three ovulatory phases, and a strong and patchy immunostaining for TIMP-1 was shown. This is the first study that has demonstrated an ovulation-associated expression of these ECM-remodelling enzymes around the human follicle at ovulation. The increased expression of TIMP-1 may reflect a specific temporal inhibition of collagenolysis and thereby a time-dependent regulation of ECM breakdown in areas surrounding the apex of the follicle.     

Expression of matrix metalloproteinases and tissue inhibitors of metalloproteinases in human chondrosarcomas

The aim of the present study was to characterise the ability of malignant chondrosarcomas to invade normal bone by analysing their production of matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs). For this purpose 12 chondrosarcomas were investigated for the expression of mRNAs for several MMPs and all 4 TIMPs by Northern hybridisation, and for immunohistochemical localisation of the proteins. A characteristic finding of these analyses was increased expression of MMP-13, MMP-14 and TIMP-2 mRNAs in chondrosarcomas when compared with nonmalignant control samples. Individual chondrosarcomas also exhibited elevated levels of MMP-1, MMP-7 and MMP-9 mRNAs. The results of Northern hybridisations were supported by immunohistochemical stainings of the corresponding tumour areas for MMP-2, MMP-14 and TIMP-2, further suggesting that these may have prognostic value for determining whether individual chondrosarcomas are locally aggressive or have a probability of recurrence. Another finding of the present study was a marked heterogeneity in histologic appearance and gene expression of the chondrosarcomas, emphasising the importance of analysing several areas of these tumours to get representative results. These findings suggest that analysis of MMPs could be a useful diagnostic indicator in patients with cartilaginous tumours and could help in differentiating between a low-grade malignant chondrosarcoma and a benign growing enchondroma.     

Immunolocalization of matrix metalloproteinases and their inhibitors in clinical specimens of bone metastasis from breast carcinoma

Matrix metalloproteinases (MMPs) are essential in several stages of the metastatic process, and in normal bone development and remodeling. We explored whether the interaction between tumor cells and bone leads to changes in MMP and tissue inhibitor of MMP (TIMP) expression thus affecting osteolysis in metastatic bone disease. Using immunohistochemistry we have investigated the MMP/TIMP expression in tumor cells, fibroblasts, osteoblasts and osteoclasts. Thirty one specimens of bone metastasis from breast carcinoma were stained for MMP-1, -2, -9, MT1-MMP and TIMP- 1, and -2 and compared with staining in normal breast tissue, primary breast carcinoma and normal bone. Specimens came from patients in three clinical scenarios: from open biopsies without or with pathological fracture, or bone marrow biopsies containing tumor from patients with pancytopenia but without clinical evidence of osteolysis. By bone histomorphometry the latter group showed a heavy tumor load not different from the open biopsy groups but displayed little active bone resorption and low numbers of osteoclasts. Cell type-specific MMP/TIMP expression was observed and the staining patterns were comparable between the three groups of patients. Though no major differences in the MMP/TIMP staining of tumor cells and fibroblasts were observed between bone metastasis and primary tumor, we showed that tumor cells do express MMPs capable of degrading bone matrix collagen. The number and activity of osteoclasts and osteoblasts was increased dramatically in bone metastases, their MMP/TIMP profiles, however, were not different from normal bone, suggesting that the mechanism of bone degradation by osteoclasts is not different from normal bone remodelling. This revised version was published online in July 2006 with corrections to the Cover Date.     

MMP9及TIMP1 mRNA在先兆子痫患者胎盘中的表达及其意义

目的检测基质金属蛋白酶9及其抑制物1的mRNA(MMP9mRNA、TIMP1mRNA)在先兆子痫患者胎盘中的表达,以探求MMP9在先兆子痫发病机制中的意义.方法用半定量逆转录聚合酶链反应(RT-PCR)技术检测正常妊娠(10例),先兆子痫(22例)剖宫产后胎盘中MMP9、TIMP1基因在转录水平的表达.结果重度先兆子痫胎盘中MMP9mRNA表达量降低(0.05±0.04),TIMP1mRNA表达量增加,MMP9/TIMP1比值下降(0.04±0.03),与轻度先兆子痫及正常对照组比较有明显意义.结论 MMP9表达在基因转录水平就已经下调,同时因TIMP1表达增强其活性进一步被抑制,因而在先兆子痫的发生和发展中有重要意义.     

Expression of matrix metalloproteinases 2 and 9 in human trophoblasts of normal and preeclamptic placentas: Preliminary findings

Objective: Here we test the hypothesis that “the expression of matrix metalloproteinase 2 and 9 proteins is altered in preeclamptic placentas compared to placentas of normal pregnancy.”Patients and methods: This case–control study includes preeclamptic placentas (40 women with preeclampsia) from a singleton pregnancy and placentas of normal pregnancies (control group, 40 women with uncomplicated pregnancy). The expression patterns of metalloproteinases 2 and 9 were examined using immunohistochemical staining methods.Results: Compared to uncomplicated pregnancy, the incidence of intrauterine growth restriction was high and the mean birth weight was markedly low in patients with preeclampsia. Both metalloproteinase 2 and 9 proteins were frequently and strongly expressed in the majority of placentas of uncomplicated pregnancies (control group). Metalloproteinase 9 expression was absent in the majority of the preeclamptic placentas. In the remaining cases of preeclamptic placentas, the expression of metalloproteinase 9 was weak. In contrast, a strong metalloproteinase 2 protein expression was seen in the majority of the preeclamptic placentas.Conclusions: These preliminary data demonstrate the expression of metalloproteinase 2 and 9 proteins in the placentas of uncomplicated pregnancies. The absence/reduced expression of metalloproteinase 9 in the preeclamptic placentas may be related to insufficient invasion of trophoblast, leading to superficial and unsuccessful placentation.     

Diverse roles of matrix metalloproteinases and tissue inhibitors of metalloproteinases in neuroinflammation and cerebral ischemia

Regulation of the extracellular matrix by proteases and protease inhibitors is a fundamental biological process for normal growth, development and repair in the CNS. Matrix metalloproteinases (MMPs) and the tissue inhibitors of metalloproteinases (TIMPs) are the major extracellular-degrading enzymes. Two other enzyme families, a disintegrin and metalloproteinase (ADAM), and the serine proteases, plasminogen/plasminogen activator (P/PA) system, are also involved in extracellular matrix degradation. Normally, the highly integrated action of these enzyme families remodels all of the components of the matrix and performs essential functions at the cell surface involved in signaling, cell survival, and cell death. During the inflammatory response induced in infection, autoimmune reactions and hypoxia/ischemia, abnormal expression and activation of these proteases lead to breakdown of the extracellular matrix, resulting in the opening of the blood-brain barrier (BBB), preventing normal cell signaling, and eventually leading to cell death. There are several key MMPs and ADAMs that have been implicated in neuroinflammation: gelatinases A and B (MMP-2 and -9), stromelysin-1 (MMP-3), membrane-type MMP (MT1-MMP or MMP-14), and tumor necrosis factor-alpha converting enzyme (TACE). In addition, TIMP-3, which is bound to the cell surface, promotes cell death and impedes angiogenesis. Inhibitors of metalloproteinases are available, but balancing the beneficial and detrimental effects of these agents remains a challenge.     

Cellular composition of pancreas-associated lymphoid tissue during human fetal pancreatic development

AIM: To study human fetal pancreatic tissue between 15 weeks of gestation and term, analysing the development of pancreatic lymphoid tissue and focusing on the presence and maturational status of dendritic cells (DCs). During normal human fetal pancreatic development lymphoid tissue arises in and around the pancreas. DCs are antigen-presenting cells which are capable of initiating immunity, but are also essential in inducing and maintaining T-cell tolerance. METHODS AND RESULTS: First, the presence and general composition of intra- and peripancreatic lymphoid tissue was investigated by histology and immunohistochemistry with antibodies to CD3, CD4, CD8, CD14, CD20, CD68, and CD79. Intrapancreatic lymphoid tissue (IPLT) appeared to be present only from 29 weeks of gestation onwards, and had a similar composition to peripancreatic lymphoid tissue (PPLT), which was found in all 23 specimens examined. Both forms of lymphoid tissue had an architecture similar to lymph nodes, with separate B- and T-lymphocyte areas and scattered macrophages. DCs were investigated in detail by immunohistochemistry for CD1a, CD83, CD86, CD123, Langerin, and DC-LAMP. Both Langerin, a marker for immature DCs, as well as DC-LAMP, a marker for mature DCs, were expressed by cells in both the IPLT and PPLT at all ages examined. CONCLUSION: The presence of DCs at all developmental stages, expressing various maturation-related markers, in addition to the general composition of the human fetal PPLT and IPLT suggests that this is fully functional and has a function comparable to peripheral lymph nodes.     

Expression of matrix metalloproteinases and tissue inhibitors of metalloproteinases define the migratory characteristics of human monocyte-derived dendritic cells

Dendritic cells (DCs) have an essential role in the initiation of immune responses as they deliver antigen/epitope and the appropriate signals to activate naïve T cells and thus start an immune response. In order to fulfil their function, DCs have to patrol different part of the body, thus migrating through the extracellular matrix to sample the local ‘antigenic’ environment. In the present study, we have investigated which enzymes might be involved in this process using the Matrigel trans‐well migration assay, an in vitro model of extracellular matrix migration. In this assay we analysed the migratory ability of interleukin‐4 (IL‐4)/granulocyte macrophage–colony‐stimulating factor (GM‐CSF)‐derived immature DCs as well as mature DCs, induced by tumour necrosis factor‐α (TNF‐α) and modified vaccinia virus Ankara (MVA). The ‘mature’ DCs showed an increased migration through Matrigel, which was significantly inhibited by inhibitors of matrix metalloproteinases (MMP). We also observed that the dominant MMP involved in this process was MMP‐9, and a concomitant decrease of the endogenous tissue inhibitors of metalloproteinases (TIMP)‐1 and TIMP‐2 was also observed. Collectively these data suggest that the balance between MMP/TIMP determines the net migratory capacity of human DCs. Surprisingly, TIMP‐3 was significantly increased in mature DC. Our data thus indicate that MMP and TIMP play a role in the migratory ability of human DCs. Our results also suggest that TIMP‐3 expression might represent a new marker of maturation of human DCs.     

Distribution patterns of matrix metalloproteinase (MMP)-2 and -9 and their inhibitors (TIMP-1 and TIMP-2) in the human decidua during early pregnancy

Early human trophoblast shows dramatic invasive properties during early pregnancy. A tightly-regulated activation of matrix metalloproteinases (MMPs) is considered to be of critical importance for the control of trophoblast invasion. The aim of the present study was to determine MMP-2, MMP-9, TIMP-1 and TIMP-2 protein expression in decidual endometrium during the first trimester of pregnancy (22-42 days post coitus) with special attention to their expression patterns in endometrial compartments. Cytokeratin staining applied to adjacent sections was used to identify epithelial and trophoblast cells. We observed that MMP-2, particularly in the fourth week, appeared to be expressed more strongly in extravillous trophoblasts (EVTs) and vascular endothelial cells in the first trimester of pregnancy. Therefore, MMP-2 is likely to be the primary mediator in invasion of the trophoblast into the decidual endometrium, as well as in vascular remodeling and angiogenesis in the first trimester of pregnancy. The high expression of TIMP-1 and TIMP-2 in EVTs and glandular epithelium suggests that a restricted and balanced expression of these molecules is important for matrix remodeling and controlled trophoblast invasion during placentation. We conclude that (1) MMP-2 and MMP-9 and their inhibitors TIMP-1, and TIMP-2 determine the invasive behavior of trophoblast into the endometrium, and in particular, (2) MMP-2 may be the key regulator of trophoblast invasion in early human pregnancy.     

Comparison of matrix metalloproteinase expression in normal and cirrhotic human liver

 To study the extend of ongoing tissue remodelling in end-stage cirrhosis, the expression of different matrix metalloproteinases [interstitial collagenase (MMP-1), M_r 72000 gelatinase (MMP-2), stromelysin-1 (MMP-3) and stromelysin-3 (MMP-11)] and of TIMP-1 was studied in 13 cirrhotic livers explanted at transplantation. The results were compared with those obtained in normal liver. Western blot, northern blot, ELISA, RT-PCR and zymogram analysis were used. Proenzymes of stromelysin-1 and -3, interstitial collagenase and M_r 72000 gelatinase were positive in normal liver, while activated enzymes were not detectable in western blot analysis. In cirrhosis proenzyme levels of the studied MMPs were reduced to a mean of 60–70%, but mRNA expression and gelatin-degrading activity increased. TIMP-1 expression was detectable on mRNA level and by ELISA in normal liver and also increased in cirrhosis. Our results show that mRNA expression of certain matrix metalloproteinases is increased in end-stage liver cirrhosis, while the amount of proenzyme is decreased, indicating enhanced MMP proenzyme turnover. These data suggest that besides increased TIMP-1 activity, altered MMP expression may also play a part in fibroproliferation in liver disease. Received: 6 June 1997 / Accepted: 1 September 1997     

Expression of matrix metalloproteinases and their inhibitors in human brain tumors

Sixty human brain tumors, classified according to the New World Health Organization (WHO) classification including, grade I schwannomas, meningiomas and pilocytic astrocytomas, grade II astrocytomas, grade III anaplastic astrocytomas, grade IV glioblastomas, grade III anaplastic oligodendrogliomas and grade IV glioblastomas and lung and melanoma metastases were analyzed for the expression of three matrix metalloproteinases (MMPs), two tissue inhibitors of MMPs (TIMPs) and for MMP activity. Some correlation was found between MMP expression and the degree of malignancy. Western blotting analysis revealed a more uniform pattern of distribution of MMP-2 (gelatinase A) than of MMP-9 (gelatinase B) and MMP-12 (metalloelastase) among tumors. MMP-9 levels were found to be significantly higher in grade III anaplastic astrocytomas and anaplastic oligodendrogliomas than those in grade I schwannomas and meningiomas. Anaplastic astrocytomas and Grade IV glioblastomas expressed significantly higher levels MMP-12 than grade I meningiomas. All sixty tumors showed a similar pattern of activity in zymography, proMMP-9 being the major species detected. Interestingly, TIMP-1 and TIMP-2 expression levels were especially low in tumors of grade II and grade III but significantly higher in tumors of grade I, particularly in schwannomas. Taken together, these data suggest that: 1) a balance between MMPs and TIMPs has an important role to play in human brain tumors; 2) TIMP expression may be valuable markers for tumor malignancy. This revised version was published online in July 2006 with corrections to the Cover Date.     

Polymorphisms in the matrix metalloproteinase-2 and tissue inhibitor of metalloproteinase-2 and the risk of human adenomyosis

The matrix metalloproteinases (MMPs) and tissue inhibitor of metalloproteinases (TIMPs) may contribute to the development of adenomyosis. The aim of the present study was to investigate whether three single nucleotide polymorphisms (SNPs) in the promoter regions of MMP-2 (-1306C/T and -735C/T) and TIMP-2 (-418G/C) genes were related to the risk of adenomyosis development. Genotypes were determined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay in 180 adenomyosis patients and 324 frequency-matched control women in a Chinese population. There were significant differences in allele frequencies and genotype distributions of the MMP-2 -1306C/T polymorphism between patients and control women (P = 0.01 and 0.04, respectively). The frequency of C allele in patients (92.2%) was significantly higher than in the controls (87.0%) (P = 0.01). Compared with the C/T+T/T genotypes, the C/C genotype could significantly increase the risk of adenomyosis development, with an odds ratio of 1.83 (95% CI = 1.13-2.96). However, no statistically significant difference was found in allele frequencies and genotype distributions of MMP-2 -735C/T and TIMP-2 -418G/C SNPs between the two groups (all P values > 0.05). Two polymorphisms of MMP-2 displayed linkage disequilibrium (D' = 0.74). The haplotype analysis suggested no significant association of four haplotypes with the risk of adenomyosis development. Our results indicated an association of MMP-2 -1306C/T polymorphism with the risk of adenomyosis, suggesting a potential role in adenomyosis development in North Chinese women.     

Expression of Fhit, cell adhesion molecules and matrix metalloproteinases in atypical adenomatous hyperplasia and pulmonary adenocarcinoma

Invasive parenchymal-type lung adenocarcinoma develops from atypical adenomatous hyperplasia (AAH), through an intermediate in situ stage of bronchioloalveolar carcinoma (BAC). We examined the expression of the putative tumour suppressor gene product Fhit, cell adhesion molecules CD44v6, E-cadherin and beta-catenin, and matrix metalloproteinase 2 and its inhibitor, TIMP-2, in a range of AAH lesions, BACs and invasive adenocarcinomas, to determine the changes in molecular expression associated with this form of neoplastic progression. Sections of formalin-fixed wax-embedded archival tissue were stained by standard Immunohistochemical techniques and scored semi-quantitatively, resulting in a grading of negative/low- or high-level staining. Fhit protein was retained at high levels in over 90% of AAH and 83% of BAC, but was found in only 6% of stromally invasive tumours (p < 0.0001). CD44v6 staining was high-level in 64% of AAH but fell to 26% in stromally invasive tumour (p = 0.007). E-cadherin and beta-catenin showed the opposite, with more high-level staining as adenocarcinoma developed (p < 0.001). High-level MMP-2 and TIMP-2 expression was relatively infrequent in AAH (32% and 40% respectively), rose in BAC (89% each) but fell in stromally invasive tumour (31% and 17% respectively) (p < 0.01). Unlike in central bronchial carcinogenesis, loss of Fhit expression is a relatively late event in this putative progression of lung adenocarcinogenesis, and has potential as a surrogate marker of invasion, which could be of value in screening patients for lung cancer. Loss of CD44v6 expression follows the convention of falling adhesion molecule expression as malignancy develops. Increased expression of E-cadherin and beta-catenin may reflect increased cell-cell contact as tissue architecture changes in the transition from AAH to adenocarcinoma. Loss of MMP-2 and TIMP-2 in stromally invasive tumour may reflect a particular role for MMP-2 at the BAC stage, with later down-regulation of this particular enzyme.     

基质金属蛋白酶及其组织抑制因子在左心室机械辅助减负荷模型中的表达

目的 研究基质金属蛋白酶(MMP)及其组织抑制因子(TIMP)在左心室机械辅助减负荷模型中的表达,探讨左心室减负荷后心肌逆向重构的分子机制.方法 结扎Lewis大鼠冠状动脉左前降支诱导心力衰竭,4周后将14只心力衰竭大鼠随机分为心力衰竭组(n=7)与移植组(n=7).将供体移植组心力衰竭大鼠的心脏及右肺移植到受体正常Lewis大鼠的腹部,通过供体的升主动脉与受体的降主动脉吻合.7只正常Lewis大鼠作为正常组.结扎左前降支4周后心脏超声测量3组大鼠心室直径和心肌梗死范围.移植2周后,称取各组大鼠心脏、左心室质量;显微镜观测左心室心肌细胞直径与心肌纤维化程度;采用实时荧光定量PCR检测MMP-1、MMP-9、TIMP-1的mRNA表达及计算MMP-1mRNA/TIMP-1 mRNA的比值.结果 结扎左前降支4周后,心力衰竭组及移植组舒张末直径(LVEDD)较正常组升高、左心室短轴缩短率(LVFS)较正常组下降,而此两组间LVEDD、LVFS及心肌梗死范围比较差异无统计学意义,两组的心力衰竭严重程度差异也无统计学意义.心力衰竭组心脏、左心室质量和左心室心肌细胞直径大于移植组与正常组;移植组心脏、左心室质量、左心室心肌细胞直径接近正常组.心肌纤维化的程度移植组＞心力衰竭组＞正常组[(7.90±2.32)％比(4.20±1.84)％比(1.54±0.31)％,均P＜0.05].心力衰竭组和移植组MMP-1、MMP-9mRNA表达均高于正常组(1.89±0.23、1.32±0.16比0.41±0.01,2.03±0.15、1.50±0.13比0.46+0.01,均P＜0.05),但心力衰竭组与移植组比较差异无统计学意义.心力衰竭组TIMP-1mRNA表达低于正常组与移植组(0.72±0.18比1.21±0.02、1.68±0.21,均P＜0.05);正常组与移植组比较差异无统计学意义.心力衰竭组MMP-1 mRNA/TIMP-1mRNA比值较正常组及移植组明显增高(2.03±0.15比0.30±0.01、0.81±0.11,均P＜0.05);正常组与移植组差异则无统计学意义.结论 左心室减负荷后,心肌逆向重塑的过程伴随着心肌细胞MMP及TIMP水平的改变.     

Temporospatial distribution of matrix metalloproteinase and tissue inhibitors of matrix metalloproteinases during murine secondary palate morphogenesis

Extracellular matrix (ECM) molecules are known to play a pivotal role in the morphogenesis of the secondary palate. The maintenance and degradation of the ECM is mediated in part by the matrix metalloproteinases (MMPs) and their endogenous inhibitors TIMPs. MMPs and TIMPs have previously been shown to be developmentally regulated within the palatal shelf during secondary palate morphogenesis. This study was conducted to examine the temporospatial distribution of these enzymes and their inhibitors within the palatal shelves using immunofluorescent localization to determine if specific changes occur in their distribution concomitant with events in palatal shelf formation and reorientation. Frontal sections through the posterior palatal shelves at gestational day (gd) 12, 13 and 14 were immunofluorescently stained for MMPs 2, 3, 9, and 13 and TIMPs 1, 2, and 3 using standard protocols and commercially available antibodies. The results demonstrated that MMPs and TIMPs were already present within the palatal shelf mesenchyme 30 h prior to reorientation and closure and that their expression within the shelf mesenchyme increased as the shelves remodeled, then decreased with closure and fusion. Increased distribution of MMPs and TIMPs within specific regions of the palatal mesenchyme and palatal epithelial basement membrane preceded decreases previously observed within these areas for their substrates, fibronectin, collagen III and collagen I. In addition, MMP-3 and TIMP-3 were immunolocalized to regions of the palatal epithelium that undergo reorganization concomitant with reorientation. The results of this study indicate that MMPs and TIMPs are developmentally regulated during palatal shelf morphogenesis and that their distribution correlates with the distribution of the ECM components of the palatal shelf they regulate. These results provide support for the idea that temporospatially controlled interactions between MMPs and their substrates may be pivotal in modulating events in palatal morphogenesis. Accepted: 3 March 2000