[Establishment of mouse embryo culture system on collagen gel layer]

In order to study the morphological features of mouse embryos in the early developmental stage, we first established an in vitro culture system applying a collagen gel layer, and then observed the morphology of the embryos cultured in this system. Embryos after hatching were attached to the collagen gel layer and grew to the egg cylinder stage. By means of morphological analysis of embryos cultured for 3 or 4 days, some interesting characteristics, such as processes and villi of the mural trophoblast, lacunae formation in the mural trophoblast, steroid synthesis of the mural and polar trophoblasts and desmosome or intermediate junctions between the mural and the polar trophoblasts, were revealed. Moreover, no morphological difference was observed between cells derived from the inner cell mass. From those findings, it has been concluded that the established culture system is useful in observing the morphology of early embryonal development and also in maintaining the viability of the embryo.