Stromal stem cells (CFU-f) in yolk sac, liver, spleen and bone marrow of pre- and postnatal mice.

Our results demonstrate that in yolk sac, liver, spleen and femoral bone marrow of mice at ages ranging between 11 d of gestation and adult life, important changes in the stromal stem cell population (CFU-f assay) occur which are correlated with haemopoiesis. In the liver, spleen and bone marrow, high numbers of CFU-f precede high haemopoietic stem cell values. As haemopoiesis starts in the spleen, CFU-f numbers in fetal liver are low. Similarly, CFU-f numbers decrease in the spleen as bone marrow haemopoiesis starts. This suggests the existence of a migration stream of stromal stem cells. In spleen and bone marrow, CFU-f numbers decrease towards adult life as these organs maintain a stable haemopoietic activity.