LOCAL PRODUCTION AND ACTION OF FOLLISTATIN IN HUMAN PLACENTA

The aim of the present study was to investigate the possible production, localization, and action of follistatin in human placenta, fetal membranes (amnion, chorion), and maternal decidua. Four different experimental approaches were used: 1) Southern blot analysis following reverse polymerase chain reaction to identify follistatin messenger RNA (mRNA) in tissue homogenates; 2) immunohistochemistry to localize immunoreactive (ir-) follistatin in the various intrauterine tissues; 3) measurement by RIA of ir-follistatin levels in culture medium of placental cells; and 4) possible action of follistatin on human CG (hCG) and progesterone release from cultured placental cells. Placental and decidual cells collected during first trimester or at term gestation express follistatin mRNA; fetal membranes (amnion, chorion) at term also express follistatin mRNA. Immunoreactive follistatin is localized in syncytial cells of placental villi at term as well as in large decidual cells, in amnion epithelium, and in chorionic cells. The placental secretion of follistatin has been confirmed by the evidence of measurable levels of ir-follistatin in the medium of cultured placental cells at term; the release is time dependent and is not modified by the addition of forskolin or progesterone. The addition of increasing doses of recombinant human follistatin does not significantly influence the release of hCG or progesterone from cultured placental cells, whereas the activin A-induced hCG and progesterone release are completely reversed. The present data showed that 1) human placenta, fetal membranes, and decidua express follistatin mRNA; 2) ir-follistatin is localized and released from placental cells at term; and 3) follistatin has a functional role in the local control system regulating placental hormone production.