[Transition from the latent to the active enzymatic form as a model of regulation of extracellular matrix degradation in the chorioamnion during human labor].

Matrix metallo proteinases (MMP) are the physiological mediators of collagen degradation and its participation in physiopathogenesis of premature rupture of membranes has been suggested by our group. With the idea of defining if some MMP become active active in a coordinated way with labor in fetal membranes, we analyzed enzymatic activity and immunoreactive protein present in extracts of amnion and chorion. It was possible to identify the presence of MMP-9 in extracts of membranes obtained during cesarean sections, without labor, although its activity/quantity was faintly detectable. Instead, extracts of fetal membranes obtained during active labor showed large activity/quantity of this MMP. With a monoclonal antibody, it was possible to show that the active form of MMP-9 could only be found in samples with labor. MMP-9 and its messenger RNA, were localized by immunohistochemistry and in situ hybridization in amniotic epithelium, in some fibroblasts of the compact layer and in trophoblast-like cells in chorion. It is concluded that: 1. Activity and quantity of MMP-9 increase selectively associated to labor; and 2. That this enzyme is expressed by different cellular populations of fetal membranes.