Expression of smad2 and smad4 in rhesus monkey endometrium during the menstrual cycle and early pregnancy

Expression of Smad2, and Smad4 mRNAs in the endometrium of rhesus monkey on Days 8, 20 and 28 of the normal menstrual cycle and on Days 12, 18 and 26 of early pregnancy was detected using in situ hybridization. The results showed that Smad2 and Smad4 mRNAs were mainly localized in luminal epithelium and glandular epithelium. The expression of Smad2 mRNA in glandular epithelium was sustained at moderate level on Days 8, 20 and 28 of the menstrual cycle, while the expression of Smad4 gradually increased with the menstrual cycle. Both Smad2 and Smad4 mRNAs in functionalis glandular epithelium were expressed at the highest levels on Day 12 of early pregnancy, while in basalis glandular epithelium the most abundant expression of both Smads occurred on Days 12 and 18 of pregnancy. On Day 26, both Smads mRNAs were expressed at the lowest levels either in functionalis or in basalis. The data suggest that the epithelium is the major compartment where TGF-betas/activins exert their biological effects via Smads, and that Smad4 may play a role in the maintenance of endometrial gland function during secreting period of the menstrual cycle. During lacunar stage of early pregnancy, Smad2 and Smad4 are implicated in the tissue remodeling of endometrial functionalis and basalis, and during early villous stage both Smads are functional primarily in basalis.