Expression of Smad Ubiquitin Regulatory Factor 2 (Smurf2) in Rhesus Monkey Endometrium and Placenta During Early Pregnancy

Smad ubiquitin regulatory factor 2 (Smurf2) is an E3 ubiquitin ligase that is involved in the Smad-mediated TGF-β signaling. TGF-β has been shown to play an important role during normal embryo implantation, but whether Smurf2 is involved in this process has not been reported. This study was first conducted to investigate the expression of Smurf2 transcript and protein in different compartments of the rhesus monkey uteri and placenta during early pregnancy. The results showed that both the cloned partial sequence of Smurf2 gene and the corresponding amino acid residues shared 99% identity with those of human homologs. On day 12 (D12) of pregnancy, strong signals of Smurf2 mRNA were found in basalis glandular epithelium and luminal epithelium, and moderate expressions were detected in functionalis glandular epithelium. During early villi stage and villi placental stage, Smurf2 mRNAs were mainly localized in the placenta villi, trophoblastic column, trophoblastic shell, and basalis glandular epithelium. There appeared strong staining signals in the arterioles on D26 of pregnancy, but faint staining signals on D18 of pregnancy. No specific staining of Smurf2 mRNA was observed in stromal cells and myometrium. The expression pattern of Smurf2 protein was generally similar to that of its mRNA. These results provide the first evidence that Smurf2 may play specific roles in glandular secretion, trophoblastic cell invasion, and placentation through mediating the expression of the related proteins of TGF-β signaling pathway during early pregnancy.