Comparative studies on the in vitro decidualization process in the baboon (Papio anubis) and human

The process of decidualization involves the morphological and functional transformation of stromal fibroblasts to decidual cells. The objective of this study was to define appropriate in vitro culture conditions required for decidualization of baboon stromal cells. Parallel studies were also done with human endometrial stromal cells for comparative analysis. Human stromal cells produced prolactin and insulin-like growth factor-binding protein (IGFBP)-1 in response to hormones (estradiol-17 beta [36 nM], medroxyprogesterone acetate [1 mu M], and relaxin [100 ng/ ml]), and production was enhanced in the presence of 0.1 mM dibutyryl cAMP (dbcAMP). By contrast, baboon cells did not produce any detectable Bevels of proplastin, even in the presence of hormones and dbcAMP, IGFBP-1 expression in baboon stromal cells was detectable by Day 6 of hormone and dbcAMP treatment and increased exponentially thereafter. In both human and baboon stromas cells, alpha smooth muscle actin (alpha SMA) expression, an early marker for decidualization in the baboon in vivo, was induced spontaneously under normal culture conditions. Furthermore, a decrease in alpha SMA expression was observed in cells producing high levees of IGFBP-1. Human cells produced significant levels of IGFBP-1 (p less than or equal to 0.01) in response to short-term dbcAMP treatment (48 h) after 2 and 12 days of hormone treatment. However, baboon stromal cells required 17 days of hormonal treatment before cells became responsive to short-term dbcAMP treatment (p less than or equal to 0.01). Finally, human endometrial stromal cells expressed the protein kinase A regulatory subunits RI alpha, RI beta, RII alpha, and RII beta whereas baboon stromal cells expressed RI alpha, RII alpha, and RII beta. No difference in the mRNA expression of these isoforms was observed in decidualized or nondecidualized cells of either human or baboon endometrium. Our observations indicate that baboon stromal cells can be induced to decidualize in vitro and that this requires dbcAMP in addition to hormones. This is the first report demonstrating in vitro decidualization in a nonhuman primate.