COMPARATIVE-STUDIES ON THE IN-VITRO DECIDUALIZATION PROCESS IN THE BABOON (PAPIO-ANUBIS) AND HUMAN

The process of decidualization involves the morphological and function al transformation of stromal fibroblasts to decidual cells. The object ive of this study was to define appropriate in vitro culture condition s required for decidualization of baboon stromal cells. Parallel studi es were also done with human endometrial stromal cells for comparative analysis. Human stromal cells produced prolactin and insulin-like gro wth factor-binding protein (IGFBP)-1 in response to hormones (estradio l-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 di butyryl cAMP (dbcAMP). By contrast, baboon cells did not produce any d etectable Bevels of proplastin, even in the presence of hormones and d bcAMP, IGFBP-1 expression in baboon stromal cells was detectable by Da y 6 of hormone and dbcAMP treatment and increased exponentially therea fter. In both human and baboon stromas cells, alpha smooth muscle acti n (alpha SMA) expression, an early marker for decidualization in the b aboon in vivo, was induced spontaneously under normal culture conditio ns. Furthermore, a decrease in alpha SMA expression was observed in ce lls 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 expr essed the protein kinase A regulatory subunits RI alpha, RI beta, RII alpha, and RII beta whereas baboon stromal cells expressed RI alpha, R II alpha, and RII beta. No difference in the mRNA expression of these isoforms was observed in decidualized or nondecidualized cells of eith er human or baboon endometrium. Our observations indicate that baboon stromal cells can be induced to decidualize in vitro and that this req uires dbcAMP in addition to hormones. This is the first report demonst rating in vitro decidualization in a nonhuman primate.