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 reg ulatory molecule, the location and function of which at the human feto maternal interface remain to be determined. The present study examined the presence of TGFalpha in the human placenta, decidua, and fetal me mbranes throughout gestation (from a total of 29 subjects) as well as its functional role in the proliferation of first trimester trophoblas ts. The peptide was localized immunocytochemically with a monoclonal a nti-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 s erved 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. V illous trophoblast celts (syncytiotrophoblast and to a minor extent cy totrophoblast) at all gestational ages as well as extravillous cytotro phoblast 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 (characterize d by their expression of cytokeratin as well as other markers) were cu ltured in die presence of TGFalpha or neutralizing anti-TGFalpha Ab (T Ab-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-TGF alpha Ab alone (25 mug/ml) did not significantly influence the prolife ration of die cells, indicating the absence of significant endogenous TGFalpha in these cultures; however, the Ab was able to abolish the st imulatory function of exogenous TGFalpha. Exogenous TGFalpha also incr eased the number of trophoblast nuclei immunoreactive for proliferatin g cell nuclear antigen and reduced the incidence of multinucleate cell s in culture. These results indicate that TGFalpha is present in the c ells of the fetomaternal interface throughout human gestation and may function as a stimulator of trophoblastic growth in situ.