Effects of matrix proteins and heparin-binding components in fetal bovine serum upon the proliferation of ectoplacental cone cells in mouse blastocysts cultured in vitro.

Abstract

Trophoblastic invasion of the endometrium is among the events that are crucial for successful implantation and hemochorial placentation. To understand the mechanism underlying the trophoblastic invasion, we investigated effects of fibronectin substratum and heparin-binding components in fetal bovine serum (FBS) upon trophoblast and ectoplacental cone (EPC) cells derived from mouse blastocysts produced by IVF and cultured in vitro. The results demonstrated that 1) in these blastocysts, contact of EPC cells with fibronectin-coated glass substratum in the presence of FBS triggered an outburst of cell proliferation with the eventual differentiation of the EPC cells into secondary giant trophoblast cells and 2) frequencies of blastocysts that exhibited EPC cell proliferation significantly increased if FO medium (modified Eagle's minimum essential medium) was supplemented with FBS depleted of heparin-binding substances (H-FBS). One possible interpretation of the effect of H-FBS is that free fibronectins or related substances in the serum might interfere with EPC cell proliferation, for which the presence of substratum-bound fibronectin is essential. Alternatively, the serum might contain heparin-binding competitive inhibitors of yet unidentified growth factor(s) necessary for EPC cell proliferation.