Morphology of mouse embryo cultured in a newly established culture system using collagen gel layer

A new in vitro culture system of embryo using collagen gel as the substrate was developed, in which mouse blastocysts were cultured. Morphological analyses including electron microscopic observation disclosed that after hatchig, the mouse blastocysts were attached to the collagen gel layer and were satisfactorily developed and differentiated. In the embryo observed on the 3rd or 4th day after culture, cellular processes and villi had penetrated the collagen gel from the mural trophoblast. While there were many vacuoles in the cytoplasm and a large number of destroyed cells in the mural trophoblast mass, some steroid producing cells were also observed. The polar trophoblasts, though having a small number of vacuoles, partially exhibited characteristic activities of steroid production. Between the mural and the polar trophoblasts, a sort of desmosome or intermediate junction was observed. There were no morphological differences among the cells derived from the inner cell mass. From these results, it was concluded that this new embryo culture system using collagen gel layer as the substrate can be of value in studies on development and differentiation of the embryo; moreover, this system can be used to replicate several phenomena similar to those appearing in in utero implantation.