Preterm premature rupture of membranes without labor is not associated with increased levels of matrix metalloproteinase-9 protein

Objectives Preterm premature rupture of membranes (PROM) accounts for 30-40 % of all preterm births. The objectives of this study were to determine whe ther matrix metalloproteinase-9 (MMP-9) is increased in preterm PROM fetal membranes, whether labor or gestational age affects expression, and whether the increase is localized to the rupture site or is membrane-wide. Methods Fetal membranes were collected from 15 pregnancies complicated by p reterm PROM and 26 control cases, which delivered at term or preterm withou t PROM. The preterm PROM cases represented both patients who labored and th ose who did not. Membrane samples at the rupture site and a remote site (ap proximately >5 cm) were analyzed for MMP-9 protein and enzymatic activity b y Western blot and gelatin zymography, respectively. Results MMP-9 levels in fetal membranes were similar at both the rupture an d the remote sites. The highest levels of total MMP-9 protein were found in preterm PROM patients with labor (p<0.05) and were increased four-fold ove r protein levels in non-laboring preterm PROM patients delivered by Cesarea n section (p<0.001). In preterm PROM patients without labor, levels of MMP- 9 protein were similar to those of non-laboring patients at term and preter m. Zymography correlated with protein results in all membranes. Conclusions Preterm PROM without labor is not associated with increased mem brane levels of MMP-9 protein, suggesting that its local elevation does not play a role in early membrane rupture.