Evidence for a spatial and temporal regulation of prostaglandin- endoperoxide synthase 2 expression in human amnion in term and preterm parturition

Context: Prostaglandin-endoperoxide synthase 2 (PTGS2) is a key enzyme involved in parturition. PTGS2 mRNA was found to be differentially expressed between placental amnion (amnion overlying the placental disc) and reflected amnion (amnion of the extraplacental chorioamniotic membranes) in term placentas. Objective: The aim was to evaluate the spatial and temporal regulation of PTGS2 expression in the amnion and the chorion-decidua. Design: PTGS2 expression was analyzed in the amnion and chorion-decidua obtained from 32 women: term not in labor (n = 12), term in labor (n = 12), and preterm labor (n = 8), by immunoblotting and densitometry. Prostaglandin E₂ (PGE ₂) in the amnion and chorion-decidua was measured by a specific immunoassay. Results: Compared to preterm labor cases, PTGS2 expression increased at term before the onset of labor far more prominently in placental amnion (4.5-fold; P = 0.002) than in reflected amnion (1.4-fold; P = 0.007). There was a significant increase in PTGS2 expression in reflected amnion (2.9-fold; P < 0.01) but not in placental amnion with labor at term. PTGS2 expression was higher in reflected amnion than in chorion-decidua in labor at term (2.9-fold; P<0.01). PTGS2 was barely detected in amnion and chorion-decidua with preterm labor. Expression of PGE₂ showed a good correlation with PTGS2 expression (r = 0.722; P < 0.001). Conclusion: PTGS2 expression in the amnion shows a distinct spatial and temporal regulation. Spontaneous labor at term and pathological preterm labor clearly differ in amniotic PTGS2 and PGE₂ abundance. Our observations underscore the biological significance of the amnion and amniotic fluid in human parturition.