RESUMO
OBJECTIVE: To determine which compartments of placenta in the term pregnancy express the embryonic stem cell markers. METHODS: We have used immunohistochemical methods with antibodies to embryonic stem cell surface antigens, TRA 1-60 (Tumor rejection antigen 1-60), TRA 1-81 (Tumor rejection antigen 1-81), SSEA-3 (stage-specific embryonic antigen-3) and SSEA-4 (stage-specific embryonic antigen-4), to identify and localize stem cells in the term placenta. RESULTS: Stem cell marker-positive cells were found in all layer of placenta. Amnionic epithelial cells was immunoreactive with TRA 1-60, TRA 1-81. Amnionic mesenchymal stromal cells was immunoreactive with TRA 1-81. Chorionic mesenchymal stromal cells was immunoreactive with TRA 1-60 and TRA 1-81. SSEA-3 and SSEA-4 were not stained at any compartment of the term placenta. Compartment that was stained most strongly by TRA 1-60 was the amnionic epithelial cells layer. Compartment that was stained most strongly by TRA 1-81 was the chorionic mesenchymal stromal cells layer. CONCLUSION: The mesenchymal stroma cells of the amnion and chorion as well as amnionic epithelial cells may be useful source of pluripotent stem cells in the term placenta.