Immunohistochemical study of inhibin A and B expression in placentas from normal and pathological gestations.

Objective: The aim of the study was to examine, by an immunohistochemical method, the distribution of Inhibin-A and -B, in placentas from normal and pathological gestations.

Materials And Methods: Sixty-two specimens of placental tissue were examined: i) ten cases from early gestations, ii) 28 cases from mature placentas, iii) six cases associated with intrauterine growth restriction, iv) four cases associated with diabetes mellitus and v) 14 placentas from gestations with fetal chromosome abnormalities. The expression of Inhibin A and B was studied by automatic Ventana method.

Results: i) Early gestation specimens: Inhibin A (+) immunoreaction was observed in the syncytiotrophoblast (8/10 cases) and in the intermediate trophoblast (6/10 cases). Inhibin B (+) immunoreaction was observed in the syncytiotrophoblast (10/10 cases) and in the intermediate trophoblast (4/10 cases), ii) Normal mature placentas: Inhibin A (+) immunostain was observed in 2/28 cases in the syncytiotrophoblast and in 7/28 cases in the intermediate trophoblast. Inhibin B (+) immunostain was observed in 28/28 cases in the syncytiotrophoblast and in 18/28 cases in the intermediate trophoblast. iii) Placentas associated with intrauterine growth restriction: Inhibin A (+) immunostain was observed in the intermediate trophoblast in 2/6 cases. Inhibin B (+) immunostain was observed in 5/6 cases in the syncytiotrophoblast and in 4/6 cases in the intermediate trophoblast. iv) Placentas associated with gestational diabetes mellitus: Inhibin A (+) immunostain was observed in 2/4 cases in the intermediate trophoblast. Inhibin B (+) immunostain was observed in 2/4 cases in the syncytiotrophoblast. v) Placentas from gestations with fetal chromosome abnormalities: no Inhibin A immunoreaction was observed. Inhibin B (+) immunostain was observed in 13/14 cases in the syncytiotrophoblast and in 9/14 cases in the intermediate trophoblast. The cytotrophoblast, the umbilical cord, and the membranes do not participate in the production of Inhibins.

Discussion: Inhibin A and B are located in the syncytiotrophoblast and the intermediate trophoblast of the placenta, during early pregnancy (Inhibin A) and present throughout pregnancy (Inhibin B). No remarkable findings in placentas of pathological gestations support the evidence that Inhibins do not participate in processes that affect the development of the placenta or the fetus, but may participate in,the mechanism of labor.