Presence and synthesis of inhibin subunits in human decidua

A growing number of studies provided the evidence that human decidua is a pregnancy-related tissue capable of hormone production and metabolism. The aim of the present study was to evaluate the possible presence of inhibin subunits in human decidua. Tissue samples were collected in pregnant women during the first (8 weeks) and second trimester (18 weeks) of gestation and at term (40 weeks). Immunohistochemical data were obtained using affinity purified polyclonal antisera raised in rabbit against porcine alpha, beta A, or beta B subunits. Levels of the respective inhibin subunits were evaluated by Northern blot analysis using cDNA probes encoding sequences corresponding to each subunit. The present results indicated that human decidua contains and synthesizes inhibin alpha, beta A, and beta B subunits. The immunohistochemical data showed that decidual cells were stained with both inhibin alpha and beta B antisera, showing a similar localization. On the other hand, cells stained with inhibin beta A antisera were sparse and followed a distribution pattern different from that of cells stained with alpha or beta B antisera. The first inhibin alpha and beta B subunit mRNAs were both expressed in first trimester of pregnancy, and those mRNA levels showed a gestational related increase. The beta A subunit mRNA was expressed at very low levels at term and could not be detected earlier during pregnancy. The present data showed that human decidua actively produces inhibin subunits with a gestational-related profile. The results suggest that decidua may be a further source of inhibin-related proteins during pregnancy and emphasize the endocrine competence of human decidua.