Induction of mmp-9 and normal presence of mmp-2, timp-1 and 2 in human fetal membranes

OBJECTIVE: To investigate the presence and regulation of an endogenous system of metalloproteinases and their inhibitors in human fetal membranes. STUDY DESIGN: Fetal membranes were collected from women undergoing elective repeat C-section with no signs of infection or pregnancy complications. Membranes were cultured in an organ explant system and stimulated with Gram negative and Gram positive bacterial toxins (LPS and Peptidoglycan polysaccharide [PGPS]). They were frozen at -70° C at various time points. Additionally membranes were collected from women with documented bacterial infection and also from women laboring at term with no signs of infection and frozen. RT-PCR was performed to determine the expression of inRNA for matrix metalloproteinase (MMP-2, MMP-9) and tissue inhibitors of metalloproteinases (TIMP-1 and TIMP-2). In situ hybridization and immunocytochemistry were performed to document the origin of mRNA and peptides in the fetal membranes. RESULTS: RT-PCR data indicated the presence of MMP-2. TIMP-1 and TIMP-2 mRNA and peptide in resting amniochorion. Membranes collected from non-laboring women did not show the presence of MMP-9 whereas infected membranes and membranes Rom laboring women showed induction of the MMP-9 gene. A reproducible increase in band intensities was seen in MMP-2 und MMP-9 mRNA from LPS and PGPS stimulated membranes. In situ hybridization documented MMP and TIMP mRNAs in both amnion and chorion. TIMP mRNA was also visible in the reticular layers of the connective tissue. Immunocytochemistry showed TIMP-1 peptide in amniochorion as well as in the reticular layer. Zymogram showed presence of MMP-2 and 9 from cultured tissues whet e as MMP-9 was absent in not mal non laboring tissues. CONCLUSION: Amniochorionic membranes are sources of matrix degrading enzynes and their counter regulatory inhibitory proteins suggesting the presence of a complete MMP regulators pathway in the fetal membranes. The presence of MMP-2 and TIMPs in normal tissue supports their role in the controlled collagenolytic process shown to exist in the fetal membrane during gestation. Induction of MMP-9 in infected as well as cultured and stimulated tissues suggests a possible role in PROM. These findings provide insights into a possible self destructive role of MMPs stimulated by infection. PROM may be an endogenous rather than exogenous process.