Location of proliferating cell nuclear antigen and p53 protein in human first trimester and term placenta

To examine immunohistochemically the distribution of cell-cycle regulators p53 and proliferating cell nuclear antigen (PCNA), which are in close cooperation with each other in first trimester and term human placentas.

Human first trimester placental tissue was obtained by curettage from legal abortions obtained for social reasons, and human term placental tissue was obtained. Neither the interrupted pregnancy nor the obstetrical history showed any abnormalities. A total of 12 tissue samples were analyzed: n = 6 (6-12 weeks), n = 6 (38-40 weeks). Tissues were evaluated by immunohistochemical study.

In the first trimester p53 expression was at a normal level, and p53 immunolabeling was present in syncytiotrophoblast and extravillous trophoblast cells found in the cell column. Very few villous stroma cells were p53 positive. PCNA was present intensely in the cytotrophoblast and in extravillous trophoblast found in the cell column. In term placentas p53 immunolabeling was very low and was expressed in only a limited number of syncytiotrophoblast cells. PCNA was at a normal level in villous and extravillous tissue. PCNA was decreased when compared with the first trimester and was present in syncytiotrophoblast and cytotrophoblast cells. A small number of endothelial cells and villous stromal cells were positive.

We think that the immunohistochemical distribution of PCNA and p53 are strongly coordinated with each other in villous and extravillous cells in human placenta. This finding may be useful in the explanation of placental pathologies.