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The simplest interpretation of our in vitro studies is that increased expression of the MMP-9 proenzyme leads to the formation of active enzyme, which, in turn, degrades type IV collagen, leading to amnion cell apoptosis. Alternative interpretations include the possibility that the increased proMMP-9 sequestered endogenous tissue inhibitors of me-talloproteinases, leading to increased activities of endogenous MMPs. This alternative explanation still invokes a role for MMPs in the induction of apoptosis and could be part of the physiological process of fetal membrane breakdown in that proMMP-9 levels increase markedly before active labor in the rat amnion. buy birth control online
Apoptosis is now recognized to play an important role in fetal and maternal tissues near the end of pregnancy. However, the factors that provoke programmed cell death in preparation for labor and after delivery remain to be clarified. Our observations suggest that increased expression of MMPs initiates apoptosis by catalyzing degradation of the basement membranes or pericellular matrix, leading to cell detachment or change in cell shape and subsequently cell demise. It should be noted that MMP activation is not the only mechanism by which apoptosis can be induced in involuting tissues. In addition to catabolic processes, altered production of matrix proteins by amnion cells and changes in levels of cytokines or growth factors may also promote cell death.
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