[Clonogenic fibroblasts from the hematopoietic organs of the human embryo and fetus at different gestational ages].

Fibroblast precursors of hemopoietic organs of 72 embryos and fetuses 5-27 weeks of age have been studied. The study has shown that the increase in the number of clonogenic fibroblasts took place in the bone marrow and spleen 2-3 weeks before the beginning of hemopoiesis, that is during the period of the highest hemopoietic stem cell concentration. These data suggest possible participation of stromal fibroblasts of hemopoietic organs in the formation of microenvironment for hemopoietic stem cell functioning.