Steroid production by early pregnancy human placental villi in culture

Organ cultures prepared from human placentae obtained at 7–12 weeks of gestation were maintained for 3–13 days in Dulbecco's modified Eagle medium (DMEM). The addition of pregnenolone to the medium resulted in a dose-related increase in progesterone production and the addition of androstenedione resulted in a dose related increase in oestrogen production. More oestrone than oestradiol was measured in medium collected at the end of the first day of culture, but, on all subsequent days, oestradiol was the predominant oestrogen produced when androstenedione was added to the culture medium. When villi were incubated with [³H]androstenedione immediately after dissection most of the radiolabelled oestrogen recovered from the tissue and medium was oestrone; however, more [³H]oestradiol was recovered when villi were tested after 3 days of culture in DMEM. The addition of oestrone to the culture medium resulted in a dose related increase in oestradiol production with oestradiol accouting for a larger proportion of the total oestrogen in the day 2 and 3 medium samples than in the day 1 samples. These data demonstrate that the enzymes required for biosynthesis of progesterone and oestrogen from exogenous substrate are maintained for at least 13 days when early pregnancy placental villi are cultured in serum-free DMEM. However, a temporal change in the pattern of oestrogen synthesis does occur in culture, such that oestradiol rather than oestrone becomes the major product of androstenedione metabolism.