A differential pattern of follistatin expression in the placenta between spontaneous, induced and non-labouring patient groups

Abstract

Follistatin has been identified in human placenta, fetal membranes and fluids, with serum follistatin concentrations rising during pregnancy, particularly near term. Our laboratory has shown follistatin concentrations rise across labour in spontaneous but not induced women. As the placenta is a source of follistatin, this study examined placental tissues using immunohistochemistry to determine differences in follistatin localization between groups. Placental tissue was collected immediately following delivery from three groups of women at term, spontaneous onset (n = 4), induction (n = 4) and non-labouring caesarian (n = 4), and immediately formalin fixed. Antigen-retrieval immunohistochemistry using a specific chicken polyclonal antiserum (CK20) raised against a follistatin peptide (AA 121-133) or pre-immune chicken serum was performed. Positive staining of syncytiotrophoblast cells of the chorionic villi was seen in patients undergoing spontaneous labour but not in the induced and caesarian delivery group. The two labouring groups (spontaneous and induced) both showed positive staining for the vascular endothelial cells within the chorionic villi and the stratum basale, whilst the caesarian delivery group was negative for any staining within these vessels. Positive staining of Hofbauer cells was observed in both labouring groups; however, the caesarian group showed infrequent positive staining of these cell types. The differences in expression pattern in the two labouring groups (spontaneous v. induced) may be due to variations in labour lengths (6.5 v. 4.5 h, respectively); however, we would have expected a lower level of expression in the same cell types rather than the complete absence of staining. The positive follistatin staining in the syncytiotrophoblast of spontaneous patients suggests this may be the source of the rising plasma follistatin seen in this group. These differences in staining support our hypothesis that an earlier endocrine signal is absent in the induced and caesarian patient groups.