Regulation of Progesterone Formation by Human Placental Cells in Culture*

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Abstract
In the present study, a culture system of human placental cells was established to examine the role of estrogen and androgen in progesterone (P4) formation. Normal human placentae were obtained at term, and cells were dispersed in Hank''s Balanced Salt Solution (5 ml/g tissue) containing 0.1% collagenase, 0.1% hyaluronidase, 0.01% deoxyribonuclease, and 1% fetal bovine serum for 2 h at 37 C. Dispersed placental cells (106 cells/ml) were placed in medium 199 with modified Earle''s salts (pH 7.4) containing 10% fetal vovine serum, 12.5 mM HEPES buffer, 26 mM NaHCO3, and 40 .mu.g/ml Gentamycin-SO4 and incubated for 72 h at 37 C and 5% CO2 in air to allow cell attachment. Medium was then changed (time zero), and P4 formation was studied thereafter. Culture of placental cells for 96 h resulted in linear increases in P4 and estradiol (E2) formation, indicating the maintenance of cell viability and steroidogenic function. Mean .+-. SE P4 formation at 48 h was 246 .+-. 16 pg/.mu.g DNA. To assess the role of estrogen on P4 formation, placental cells were incubated for a period of 48 h with various amounts (10-7-10-4 M) of the antiestrogen ethamoxytriphetol (MER-25), the aromatase inhibitor hydroxyandrostenedione (4-OHA), and/or E2. Both MER-25 ,and 4-OHA resulted in a dose-dependent deline (P < 0.01) in P4 formation (> 80% decline at 10-4 M MER-25 or 4-OHA). The marked reduction in P4 formation caused by 4-OHA alone was reversed by concomitant addition of E2; however, E2 alone had no effect. To assess the role of androgens on P4 formation, cells were incubated for 48 h with increasing amounts (10-7-10-4 M) of androstenedione, dehydroepiandrosterone (DHA), or dihydrotestosterone. Although the formation fo E2 was enhanced by DHA, formation of of P4 was not affected by the aromatizable androgens DHA or androsterenedione or the nonaromatizable dihydrotestosterone. The decline in P4 formation by human placental cells in culture elicited by MER-25 or 4-HOA supports the hypothesis of a regulatory role for estrogen in placental P4 formation during human pregnancy. The lack of effect of exogenous estrogen suggests that the action of estrogen on P4 formatoin may be permissive.