Cholinergic markers in transformed trophoblast cells: BeWo and JAr cells

During the first trimester of pregnancy, the human placental trophoblast contains very low levels of choline acetyltransferase (ChA), a specific enzyme for synthesis of acetylcholine (ACh) and a reliable cholinergic marker. There is a relationship between ChA levels and development and maturation of syncytiotrophoblast during the first six months of pregnancy, when ChA levels reach maximum. These observations suggest that ChA and its product, ACh, have significant roles during differentiation of cytotrophoblast into syncytium. Therefore, we have measured ChA levels in malignant trophoblast cultures before and after differentiation. Two pure trophoblast cell lines (BeWo and JAr) are used in these studies. ChA in these cells was determined by a standard radiometric method in which 14C-acetyl groups were transferred from 14C-acetylcoenzyme A to choline. Methotrexate (1 microM) was used to differentiate the cells. The following results were obtained: 1) Undifferentiated BeWo cells contained ChA level of 311.0 +/- 8.3 pmoles ACh formed (M +/- S.E., N = 6)/mg protein/10 min. Differentiation decreased ChA level to 213.0 +/- 9.3 pmoles ACh/mg protein/10 min.; b) Undifferentiated JAr cells contained ChA levels of 279.0 +/- 15.0 ACh pmoles formed/mg protein/10 min. This decreased to 166.8 +/- 10.0 upon differentiation; c) Upon differentiation, ChA levels decreased by 31.5-40.2% in BeWo and JAr cell lines. In term human placenta, the ChA levels falls by about 46.0-73% after syncytiotrophoblast is fully developed; d) Chorionic gonadotropin (hCG), which is produced in cytotrophoblast, is a standard tumor marker for chorionic cancer. As the syncytiotrophoblast is formed, production of hCG decreases. Similarly, production of hCG by BeWo and JAr cells decreases upon their differentiation, and e) In hydatidiform mole, which can undergo malignant transformation into choriocarcinoma, there were no significant levels of ChA. These observations suggest that ChA and ACh are necessary for development and maturation of syncytiotrophoblast.