Histological and immunohistochemical findings of the intermediate trophoblasts in normal full term and pre-eclamptic placentas

Background: Recent studies have suggested that implantation site intermediate trophoblasts (ISITs) and chorionic type intermediate trophoblasts (CTITs) show different immunohistochemical findings, and that each type has specific location in placentas. However, we observed that both subtypes are intimately admixed in many areas of the placentas and both types are proliferated around the infarcts. Methods: In order to examine the site specificity in their distribution and the changes of intermediate trophoblasts (ITs), if any, in the pre-eclamptic placentas, quantitative analyses of ISITs and CTITs using p63, CD146, placental alkaline phosphatase, human placental lactogen, and α-inhibin were performed in normal and pre-eclamptic placentas containing infarcts. Results: In the fetal membranes of both normal and pre-eclamptic placentas, CTITs and ISITs were equally identified, forming distinct layers. ISITs were predominant in the intervillous septum and basal plate, while CTITs were predominant in the subchorionic area. At the margin of infarcts in pre-eclamptic placentas, both subtypes were increased in number, forming distinct layers. Conclusions: The subtypes of ITs do not have site specificity in placentas. Increased number of ITs and zonal distribution around infarcts suggest that CTITs and ISITs have differentiation associated relationship, and the differentiation might be related to the microenvironment of placenta, such as intraplacental oxygen concentration.