Similar preservation of CD34⁺CD38⁻ cells when UCB progenitors are cultured at 2% to 3% O₂ on FN with OB factors or in contact with the osteoblast cell line MG-63. CD34⁺ progenitors were cultured in (A) SCF, FLT3L, and TPO or in (B) SCF, IL-6, and CXCL12. (C) CD34⁺ progenitors were cultured for 7 days at 2% to 3% O₂ either on FN-coated plates and SCF, IL-6, and CXCL2 or on the MG-63 osteoblast feeder. FACS analysis was done on CD45⁺ gated fractions in the coculture. Shown here is a FACS plot representative of 1 of 3 independent experiments.