Increased survival of CBA pluripotent haemopoietic stem cells in vitro induced by a marrow stromal factor in Sl/Sld mice.

Media conditioned by marrow adherent cells from anaemic Sl/Sld and W/Wv mice increased the 24-h survival of CBA CFUs in vitro compared to fresh medium to about the same extent as marrow-conditioned medium from normal Sl+/Sl+, W+/W+, and CBA mice. Sl/Sld marrow-conditioned medium also increased the percentage of CFUs in DNA synthesis to the same extent as CBA marrow-conditioned medium. These results demonstrate that Sl/Sld mice produce a marrow stromal factor that increases both survival of CFUs and the percentage of CFUs in DNA synthesis in vitro. Therefore, the defective haemopoietic microenvironment of Sl/Sld mice is not due to a deficiency in the production of this factor.