Analyzes on ECM metabolism in transgenic and knockout mice

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Among the matrix metalloproteinase (MMP) gene family members, MMP-2 (gelatinase A) is believed to be involved in cancer invasion and metastasis and joint destruction, and thus its function in vivo is important. Membrane-type MMPs (MT-MMPs) were recently cloned as acribators of proMMP-2 and the degradation mechanism of extracellular matrix by the MT-MMPs/MMP-2 system is one of the key projects in the field of MMP research. In the present studies, we have demonstrated that proMMP-2 activation is mediated by MT1-MMP in the human invasive breast carcinomas and human thyroid carcinomas. In the human osteoarthritic and rheumatoid arhtritic cartilages, MT1-MMP also playd a major role in the activation of proMMP-2, showing a positive correlation with cartilage destruction. We also revealed that MT1-MMP is an extracellular matrix-degrading proteinase capable of digesting interstitial collagens and aggrecan as well as an activator of proMMP-2. MT3-MMP had a similar acitivity against these substrates except for type I collagen. Transgenic mice expressing MT1-MMP specifically in the cartilages are being made and analyzes of their phenotypes are now under way. These mice will be back crossed with MMP-2 knockout mice which had been made by a Japanese group and their phenotypes will be examined.