Objective: To investigate a possible site-specific augmentation of prostaglandin (PG) synthesis in the fetal membranes during labor.
Methods: We used reverse transcriptase-polymerase chain reaction or Western blot analysis to evaluate the expression of cytosolic phospholipase A2 (cPLA2) and cyclooxygenase-1, -2 (COX-1, -2), in both the upper and lower parts of the amnion, chorion laeve, and decidua vera tissues from term pregnant women before (n = 8) and after labor (n = 24). Prostaglandin E2 (PGE2) secretion from amnion-derived WISH cells was assessed using enzyme-linked immunosorbent assay after stimulation by cyclic mechanical stretching and interleukin-1 (IL-1).
Results: The expression of cPLA2 and COX-1 and COX-2 mRNAs was detected in all samples examined. Western blot analysis revealed that COX-2 expression in the upper part of the amnion, chorion laeve, and decidua vera tissues after labor was 4.7-, 4.9-, and 3.7-fold higher than that before labor, respectively (P < .05 for all). The cPLA2 protein expression in the upper part of the amnion and chorion laeve tissues after labor was 14.0- and 8.8-fold higher than that before labor, respectively (P < .05 for both). Moreover, in specimens obtained after labor, the amnion COX-2 expression and the decidua vera cPLA2 expression in the lower part of the fetal membrane was 1.9- and 2.6-fold higher than the respective levels in the upper part (P < .05 for both). In an in vitro study, cyclic mechanical stretching significantly enhanced IL-1-augmented PGE2 secretion from WISH cells.
Conclusion: In the lower part of the amnion and decidua vera tissues, adjacent to the dilating cervical canal, PG synthesis was upregulated site specifically after labor. Such enhancement of amnion PG synthesis might be regulated at least partly by IL-1 and cyclic distension.