Expression of mRNA encoding decidualization-associated protein, a variant of acute-phase alpha 2 macroglobulin, by...

The patterns of expression of mRNA encoding decidualization-associated protein (DAP) in the rat uterus from early, mid-, and late stages of pregnancy were examined by in situ hybridization to provide an insight into the function of DAP during pregnancy. Parallel studies were performed on rat uteri during the oestrous cycle and oil-induced deciduomata. DAP transcripts were absent in virgin uteri and during the day of implantation (day 5), low in early gestation tissues (days 8, 9) and high during midgestation (days 10-14). Expression of mRNA encoding DAP was first detected on day 8 of pregnancy in decidual cells of the lateral decidual glycogen wing areas. On day 9, mRNA encoding DAP was found in the same area as on day 8 as well as in the outer layer of cells in the antimesometrial decidua adjacent to the myometrium termed the fibrinoid capsula. On days 11 and 12, expression appeared in the decidual cells of the mesometrial decidua, and was particularly strong around the ectoplacental cone and blood vessels that were invaded by the trophoblast. By day 13 and throughout the remainder of pregnancy, expression occurred in the mesometrial decidua and metrial gland. No signal was observed in granulated metrial gland cells. mRNA encoding DAP was also found in the smooth circular muscle coat adjacent to the mesometrial decidua. A similar pattern and cellular localization of expression of mRNA encoding DAP expression was detected during the development of the deciduomata, artificially induced in the absence of a conceptus. The spatial and temporal patterns of expression correlated with a possible role for DAP in mediating fetal-maternal interactions and the establishment of the placental structure.