Pleiotrophin messenger ribonucleic acid levels increase in mouse endometrial stromal cells during decidualization

In mice (and other species) fibroblast-like endometrial stromal cells differentiate into large decidual cells during early pregnancy. These decidual cells, which play an important function during the process of embryo implantation, eventually die or form the maternal component of the placenta. In the current study, with the use of subtractive hybridization methods and Northern blot analysis, we found that steady-state pleiotrophin transcript levels are increased in uterine horns undergoing artificially induced decidualization compared to control hems. Steady-slate pleiotrophin transcript levels were significantly (P < 0.01) greater in uterine horns undergoing decidualization compared to the control horn at 48 h and 72 h, but not 24 h, after the application of the deciduogenic stimulus to appropriately sensitized uteri. This increase in pleiotrophin transcript levels was localized to the endometrial stromal cells undergoing decidualization, as determined by in situ hybridization. Finally, we also determined if pleiotrophin transcript levels were greater in implantation segments compared to inter-implantation segments of the uterus during early pregnancy. Steady-state pleiotrophin transcript levels were significantly (P < 0.01) greater in implantation compared to inter-implantation segments on day 6 to 8, but not 5 (day 1 = vaginal plug), of pregnancy. In conclusion, pleiotrophin transcript levels increase in the endometrial stromal cells during decidualization suggesting that it might play a role in the process.