In vitro identification of the trophoblastic stem cell of the human villous placenta

An in vitro search for th e epithelial stem cell of the placenta has been made. The cytotrophoblast has been selected for tissue culture from germinal beds of cell column cytotrophoblast of the first and early second trimester placenta. These beds have been shown by Wislocki and Padykula 9 to represent the generative source of new and expanding placental villi in vivo. Th e morphologic charact eristics of these cell columns confirm their cytotrophoblast composition in hematoxylin and eosin sections. Under the dissecting microscope comparable areas were stlected and ex planted in tissue cultures. Primary growth of cytotrophoblast with characteristic micro villi migrated from these cell columns and have been followed by daily microscopic observation. HCG was detected in the medium in which these cells were grown for a limited period of time, roughly comparable to the period during which mitosis occurred in cytotrophoblast. It is concluded that these cells represent the functioning cytotrophoblast of the normal placenta.