In vitro production of pregnancy-associated plasma protein-A (PAPP-A) by trophoblastic cells.

Pregnancy-associated plasma protein-A (PAPP-A) a high molecular weight glycoprotein, is found in high concentration in the maternal circulation during pregnancy. Immunohistochemically, PAPP-A can be localized in the trophoblast and in the decidua. Short term cultures of trophoblastic and decidual explants produce PAPP-A in vitro. It was thus of interest to see if long term cultures of primary monolayers of human trophoblast cells were capable of producing PAPP-A. Under our in vitro conditions, trophoblastic monolayers were producing both PAPP-A and beta hCG. During the first 3 days of culture PAPP-A levels increased in the medium whereas beta hCG levels decreased. The production of both proteins could be inhibited by cycloheximide. These results strongly suggest that the trophoblast is a source of PAPP-A in vivo.