LAMININ PROMOTES IN-VITRO OUTGROWTH OF MOUSE TROPHOBLAST FROM BLASTOCYSTS CULTURED IN HANGING DROP

Differentiation of the nonadherent trophectoderm cells of the mammalia n embryo into attachment-competent trophoblast cells appears to be a n ecessary event for invasion of the uterine stroma. We have used a hang ing drop culture system to investigate the involvement of contact with a solid surface and extracellular matrix proteins on mouse trophoblas t differentiation. We report that laminin, but not fibronectin, promot es in vitro outgrowth of mouse trophoblast without attachment of the e mbryo to a solid surface, in a serum free culture medium. This result indicates that, in the presence of a trophoblast differentiation facto r, the contact of the embryo with a solid surface is not necessary to obtain in vitro trophoblast differentiation.