Matrix metalloproteinases (MMPs), specifically MMP-9 plays a role in human placentation. The enzyme confers an invasive ability to cytotrophoblasts and degrades the endometrial matrix as the cells infiltrate the decidua to keep up with placental growth. Since tumor necrosis factor-a (TNF-a) can induce the synthesis of MMP-9, we investigated the patterns of changes in and correlation between placental villous MMP-9 and TNF-a expressions throughout normal human gestation. Placentas were obtained from 179 normal pregnant women who underwent elective abortion or term delivery. Chorionic villi isolated from placental samples were grouped as first, second, and third trimester (7 0/7 -13 0/7 , 13 1/7 -23 6/7 , and 37 0/7 -42 4/7 weeks, respectively). Chorionic villous TNF-a and MMP-9 proteins were assayed using enzyme immunoassay kits. There were significant differences in MMP-9 and TNF-a protein expressions among the trimester groups (P ¼ .001). The MMP-9 protein increased progressively with an increase in gestational age (GA), but TNF-a peaked in the second trimester. Within each trimester group, we searched for the effects of variation of GA in days on the 2 variables. A significant positive correlation between MMP-9 and GA was noted in the first trimester (r ¼ 0.364, P ¼ .005). No other comparisons were significant. When GA was controlled for, partial correlation revealed a significant positive correlation between TNF-a and MMP-9 only in the second trimester (r ¼ 0.300, P ¼ .018). We hypothesize that the TNF-a peak and the positive correlation between TNF-a and MMP-9 in the second trimester of normal human gestation could contribute toward a successful pregnancy outcome.

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