Increased survival of haemopoietic pluripotent stem cells in vitro induced by a marrow fibroblast factor.

When mouse bone marrow was incubated in medium conditioned by marrow fibroblasts, the survival of pluripotent stem cells (CFUs) was considerably greater than when marrow was incubated in fresh medium. This increase in CFUs survival depended on the age of the marrow fibroblast culture, the initial number of cells in the culture, and the concentration of the conditioned medium. Medium conditioned by fibroblasts from other adult tissues--spleen, bone, and subcutaneous tissue--did not increase CFUs survival, but medium conditioned by embryo bone did. The increase in CFUs survival by marrow-fibroblast-conditioned medium was not accompanied by any change in the total number of nucleated cells of the incubated marrow nor by any comparable increase in the survival of granulopoietic stem cells (CFUc) or erythropoietic stem cells (BFUE). These results indicate that marrow fibroblasts produce a factor that increases the survival of CFUs, which may be involved in the role of marrow stroma in the control of haemopoiesis.