Opposite Regulation of Transforming Growth Factors-β2 and -β3 Expression in the Human Endometrium

TGF-βs have been reported to mediate the repression by progesterone of several matrix metalloproteinases in the human endometrium, thereby preventing menstrual breakdown. Because of conflicting reports on the expression profiles, source, and regulation of the TGF-β system in this tissue, we investigated by real-time RT-PCR and ELISA the expression of the three TGF-βs (total and mature forms) and their two receptors throughout the menstrual cycle, and their regulation by ovarian steroids in cultured explants including their microdissected epithelial and stromal compartments. Regulation by cAMP and MAPK was further investigated. This comprehensive study on a large collection of endometrial samples evidenced a differential regulation of TGF-β isoforms expression, both in vivo and in explant culture. In vivo, TGF-β2 increased by about 5-fold at the mid-late secretory phase then declined after menstruation; TGF-β3 increased at menstruation and remained high during the proliferative phase; TGF-β1 was maximal at menstruation. In explants cultured without ovarian steroids both TGF-β2 and -β3 were preferentially expressed in the stroma. Ovarian steroids strongly repressed both TGF-β2 and -β3 in stroma but only TGF-β2 in glands. cAMP prevented inhibition by ovarian steroids of TGF-β2 but not -β3. In presence of ovarian steroids, MAPK inhibitors (p38 and ERK pathways) stimulated TGF-β3 but inhibited TGF-β2 expression. In conclusion, TGF-β2 and -β3 are differentially expressed during the menstrual cycle and regulated by progesterone in epithelial vs stromal cells. The opposite regulation of TGF-β2 and -β3 by cAMP and MAPK could account for their distinct expression in vivo.