Differential cyclooxygenase-1 and -2 gene expression in human myometria from preterm and term deliveries

The expression of cyclooxygenase-1 (COX-1) and COX-2 genes in myometria from preterm and term pregnancies was investigated by in situ hybridization, immunoblotting, and immunocytochemistry. In situ hybridization revealed that myometrial smooth muscle contained both COX-1 and COX-2 messenger ribonucleic acid transcripts. Immunoblotting revealed that myometria contained 55- and 67-kilodalton COX-1 proteins as well as 72- and 56-kilodalton COX-2 proteins. Immunocytochemistry showed that COX-1 and COX-2 proteins are present in the myometrial smooth muscle. The expression of COX-1 and COX-2 genes differed in myometria. For example, although COX-1 expression was lower, COX-2 expression was higher at term compared to preterm pregnancy not in labor. In addition, although COX-1 expression was not dependent on labor, COX-2 expression was lower with labor compared to not in labor for both preterm and term pregnancy. The myometrial smooth muscle also immunostained for prostaglandin E2 (PGE2) and PGF2 alpha, suggesting that the cyclooxygenases are catalytically active. The changes in PGE2 and PGF2 alpha paralleled the changes in COX-1 enzyme in terms of being lower at term compared to preterm pregnancy and the changes in COX-2 enzyme in terms of being lower during labor at preterm and term pregnancy. In summary, our results demonstrate that pregnant human myometria express both COX-1 and COX-2 genes. The expression of these genes differed in preterm or term pregnancy myometria from in labor and not in labor.