LOCALIZATION OF TRANSFORMING GROWTH-FACTOR-ALPHA IN THE HUMAN PLACENTA AND DECIDUA - ROLE IN TROPHOBLAST GROWTH

Transforming growth factor alpha (TGFalpha) is an important growth regulatory molecule, the location and function of which at the human fetomaternal interface remain to be determined. The present study examined the presence of TGFalpha in the human placenta, decidua, and fetal membranes throughout gestation (from a total of 29 subjects) as well as its functional role in the proliferation of first trimester trophoblasts. The peptide was localized immunocytochemically with a monoclonal anti-TGFalpha antibody (Ab) (MF9) on paraffin-embedded tissues via the avidin-biotin complex-peroxidase technique with diaminobenzidine (DAB) as the chromogen. Omission or TGFalpha absorption of the primary Ab served as negative controls. Specific (cytoplasmic) staining was noted in typical stromal-type decidual cells, including cells of the decidua basalis and parietalis and chorionic decidua, throughout gestation. Villous trophoblast celts (syncytiotrophoblast and to a minor extent cytotrophoblast) at all gestational ages as well as extravillous cytotrophoblast cells (intermediate and cytotrophoblastic shell) also showed specific cytoplasmic staining. Chorionic trophoblasts showed variable staining, and little or no immunoreactivity was seen in die amniocytes. Second-passage first trimester human trophoblast cells (characterized by their expression of cytokeratin as well as other markers) were cultured in die presence of TGFalpha or neutralizing anti-TGFalpha Ab (TAb-1) or no additive for 18 h prior to exposure to H-3-TdR for 6 h to measure H-3-TdR uptake. TGFalpha (0-100 ng/ml) caused a dose-dependent stimulation of proliferation, reaching a near plateau at 6-100 ng/ml to slightly more than double the basal level. The presence of anti-TGFalpha Ab alone (25 mug/ml) did not significantly influence the proliferation of die cells, indicating the absence of significant endogenous TGFalpha in these cultures; however, the Ab was able to abolish the stimulatory function of exogenous TGFalpha. Exogenous TGFalpha also increased the number of trophoblast nuclei immunoreactive for proliferating cell nuclear antigen and reduced the incidence of multinucleate cells in culture. These results indicate that TGFalpha is present in the cells of the fetomaternal interface throughout human gestation and may function as a stimulator of trophoblastic growth in situ.