Growth of murine multipotent stem cells in a simple "serum-free" culture system: role of interleukin-3, erythropoietin, and hemin.

The growth requirements of normal murine marrow-derived multipotent stem cells (CFU-GEMM) in a simple clonal cell culture system substantially devoid of exogenous serum proteins was assessed. The ability of murine interleukin-3 (Il-3), recombinant human erythropoietin (rEPO), and a crystalline preparation of the protoporphyrin hemin to support colony growth in "serum-free" cultures was examined by titration. The results suggest that both Il-3 and hemin are limiting for multipotential colony growth in "serum-free" cultures, but that EPO is not. In addition, the "sensitivity" of CFU-GEMM to each growth factor appeared to increase in the "serum-free" environment as evidenced by a "shift-to-the-left" in all the titration curves. Nearly half of the GEMM colonies grew to full maturity in the absence of exogenous EPO. Given the optimal concentration of each growth factor, high colony growth was consistently observed in the "serum-free" cultures, with a range from 65% to 119% of the serum control level. It is therefore concluded that supplementation of murine marrow cultures with Il-3 and hemin alone may provide the necessary setting for studying the factors that modulate the growth of multipotent stem cells in a serum-free environment.