Hemopoiesis of the cultured whole mouse embryo.

In vitro cultured murine embryos provide a valuable methodology for studying the ontogeny of hemopoiesis in mammalian embryos. Under improved conditions, 49% of mouse embryos cultured from the blastocyst stage reached the early somite stage. The development of the embryo was arrested at different stages by omitting human cord serum from the culture medium at specific times. These observations suggest the appearance and differentiation of the first hemopoietic cells in the mouse yolk sac to be independent of a normal embryo. In the yolk sac of all cultured mouse embryos, hemopoietic cell differentiated into a major cell type, erythroblasts, and minor cell types such as monocytes, macrophages, and granulocytic cells. A small number of hemopoietic cells remained undifferentiated.