Up-regulation of cyclooxygenase-2 gene expression by chorionic gonadotropin during the differentiation of human endometrial stromal cells into decidua

Human endometrial stromal cells contain human CG (hCG)/LH receptors and in vitro, hCG/LH can promote stromal cells differentiation into decidua. In the present study, we tested the hypothesis that the treatment of stromal cells with exogenous hCG/LH to promote their differentiation would result in up-regulation of cyclooxygenase-2 (COX-2) gene expression. The stromal cells from proliferative phase endometria were cultured for 10 days with 10 ng/ml estradiol and 100 ng/ml progesterone in the presence or absence of increasing concentrations of highly purified hCG. Northern blotting demonstrated that the cells contained a 4.4-kb COX-2 messenger RNA transcript whose levels significantly increased after treatment with hCG. Western blotting showed that the cells contained a 72-kDa COX-2 protein which also significantly increased after treatment with hCG. The effect of hCG on COX-2 messenger RNA and protein was seen at 10 ng/ml and higher concentrations sustained the increased levels. Although human LH mimicked hCG, human FSH, TSH, and isolated alpha- and beta-subunits of hCG had no effect on COX-2 protein levels suggesting that the hCG effect is hormone specific and requires the conformation of native hormone. The effect of hCG on COX-2 protein paralleled the increase in media prostaglandin E(2) levels indicating that the increased COX-2 is catalytically active. We measured the transcription rate of COX-2 gene and half-life of its transcripts to determine the molecular mechanism of hCG action. The results showed that hCG treatment had no significant effect on transcription rate of the COX-2 gene. On the other hand, treatment with hCG significantly increased the half-life of the COX-2 transcripts from 2.6 h in the control to 6.7 h after treatment. In summary, we conclude that treatment of human endometrial stromal cells with exogenous hCG to promote their differentiation into decidua results in an up-regulation of COX-2 gene expression by increasing the stability of the transcripts.