Gene expression of transforming growth factor-β receptors types I and II in rat endometrium during the estrous cycle and early pregnancy

Roles of transforming growth factor-beta (TGF-beta) receptor types I (T beta RI) and II (T beta RII) during the estrous cycle and implantation of rodents are currently unclear. In the present study, the spatial and temporal expressions of T beta RI and T beta RII in rat endometrium during the estrous cycle, pre-, and peri-implantation were examined using in situ hybridization and semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR). With in situ hybridization, T beta RI and T beta RII were expressed at weak levels in rat endometrium during the estrous cycle. During pre-implantation, both receptors were expressed in the luminal epithelium and glandular epithelium on Days 0.5 and 1.5 of pregnancy, but were down-regulated on Days 2.5 and 3.5. During peri-implantation, both TGF-beta receptors were localized in the luminal epithelium and subepithelial stroma to facilitate attachment reaction and trophoblast invasion. They were highly expressed on Day 4.5, whereas were down-regulated on Days 5.5 and 6.5. Semi-quantitative RT-PCR analysis confirmed the data obtained by in situ hybridization. These results suggest that during pre-implantation, both TGF-beta receptors are functional in the proliferation of endometrial epithelial cells. During peri-implantation, both TGF-beta receptors play important roles during the onset of the uterine receptivity and the attachment reaction. TGF-beta signaling is down-regulated when trophoblast invasion begins. (c) 2005 Elsevier Inc. All rights reserved.