Introduction of interleukin-3 gene into stromal cells from the bone marrow alters hemopoietic differentiation but does not modify stem cell renewal.

Cloned endothelial-adipocytes from the stroma of mouse bone marrow (designated 14F1.1) induced growth of stem cells in vitro, accompanied by either pre-B lymphopoiesis or myelopoiesis. We examined the contribution of colony stimulating factors (CSF) to the process. mRNA for GM-CSF, interleukin 3 (IL3), G-CSF, and IL4 could not be detected in the stromal cells. Expression of IL3 gene, achieved by transfection of 14F1.1 cells with a plasmid carrying an IL3 cDNA, shifted the direction of differentiation but did not improve stem cell maintenance. It is proposed that novel stromal cell factors, distinct from known CSFs, regulate stem cell renewal.