Distribution of ECM Components in Early Embryos

Abstract

Extracellular matrix (ECM) components have been localized in preimplantation and early postimplantation mouse embryos at the ultrastructural level using a fixative supplemented with tannic acid. In the early blastocyst, tannic acid postive structures occurred in the blastocyst cavity. Moreover, positive reaction products were seen between polar trophoblast cells and cells of the inner cell mass. After implantation of the embryos (late day 4, early day 5) stained ECM components were located between the ectodermal and the endodermal cell layers. These structures occurred in the part of the embryo where polar trophoblast cells were in contact with endodermal cells. On late day 5 or early day 6 of development the tannic acid positive Reichert’s membrane had formed. In the extraembryonic part of the developing egg cylinder, a fully developed basement membrane of the ectoderm could be seen, whereas in the embryo there were only patches of stained material which occurred between the ectodermal and endodermal cell layer.