Ontogenic localization and distribution of S-100beta protein in human placental tissues

OBJECTIVE: To investigate whether S-100beta, a brain-specific protein found in amniotic fluid and fetal circulation, is present in fetoplacental tissues throughout gestation. METHODS: S-100beta protein localization and concentration were assessed in placentae, fetal membranes, and cord vessels. Tissues were obtained from 40 pregnant women at different gestational ages: first trimester (n = 10), second trimester (n = 10), early third trimester (n = 10), and late third trimester (n = 10). RESULTS: In the placenta, S-100beta was localized in villous and intermediate trophoblast cells. The intensity of immunostaining and protein concentration increased with advancing gestation. S-100beta protein was also present in amnion, trophoblast, and decidual cells of fetal membranes, and in endothelial cells of umbilical vessels at all gestational ages. CONCLUSION: This study demonstrated that fetoplacental tissues contain S-100beta protein, suggesting that these tissues may, at least in part, be responsible for the high level found in the fetal circulation. Although the significance of placental S-100beta is unknown, this origin should be taken into account when this protein is used as a marker of brain injury in the fetus or infant at birth.