Influence of SDF-1α, GM-CSF, TPO, SLF, and FL, alone and in combination on the survival of CFU-GMs and CFU-GEMMs in FACS-sorted CD34⁺⁺⁺ cord blood cells subjected to delayed addition of a combination of maximally stimulating growth factors.

Human CD34⁺⁺⁺ cells were plated at time 0 in the absence and presence of various concentrations of SDF-1α, GM-CSF, TPO, SLF, FL, or SDF-1α plus either GM-CSF, TPO, SLF, or FL. The combination of rhu Epo (1 U/mL), rhu GM-CSF (10 ng/mL), rhu IL-3 (10 ng/mL), and rhu SLF (50 ng/mL), a maximally potent combination of cytokines to stimulate colony formation, was added to the plates at either time 0 or 24 hours and cultures were scored for CFU-GM and CFU-GEMM colonies 14 days after the addition of the maximally stimulating cytokines. Results are given as colonies ± SD (with the percent survival given in parentheses). (A) Significant increase in survival compared to control plates at the same time of delayed growth factor addition (P < .001). (B) Significant increase in survival compared to control plates at same time of delayed growth factor addition (P < .01). (C) Significant increase in survival compared to control plates at same time of delayed growth factor additions (P < .05). (D) Significantly greater survival than either cytokine alone and additive to slightly less than additive effects at the same time of delayed growth factor addition (P < .05). (E) Significantly greater survival than with either cytokine alone and greater than additive effect at the same time of delayed growth factor addition (P < .01). The addition of either SDF-1, GM-CSF, TPO, SLF, FL, or the combination of SDF-1 plus these cytokines along with the maximally stimulating combination of Epo, GM-CSF, IL-3, and SLF at time 0 had no significant effect (P > .05) compared to control medium added with the maximally stimulating combination of growth factors at time 0 (data not shown).