Objective: Our purpose was to determine the distribution of membrane-bound cell surface peptidases, namely aminopeptidase N, neutral endopeptidase, and dipeptidyl peptidase IV in the human placenta and fetal membranes.
Study design: Frozen tissue sections of the first-trimester chorionic villi, term placentas, and term fetal membranes were stained by indirect immunofluorescence with specific monoclonal antibodies.
Results: In the first trimester chorionic villi cytotrophoblasts expressed both neutral endopeptidase and dipeptidyl peptidase IV, but syncytiotrophoblasts expressed only neutral endopeptidase. Stromal cells in the chorionic villi expressed the three peptidases at various intensities. In the term placentas villous syncytiotrophoblasts expressed neutral endopeptidase weakly, and the villous stromal cells expressed large amounts of both aminopeptidase N and dipeptidyl peptidase IV but neutral endopeptidase weakly or faintly. In the term fetal membranes amniotic epithelial cells and chorion laeve expressed both neutral endopeptidase and dipeptidyl peptidase IV. Decidual cells in the decidua parietalis moderately or highly expressed aminopeptidase N.
Conclusion: Three peptidases, aminopeptidase N, neutral endopeptidase, and dipeptidyl peptidase IV, are expressed by different cell populations in the human placenta and fetal membranes, suggesting their respective and important roles at the maternofetal interface.