Phenotypic characterization of CD34⁺CD38⁻ cells expanded under serum-free and serum-containing conditions. CD34⁺CD38⁻BM cells were cultured in 1.5 mL SF-medium or FCS-containing medium supplemented with KFM. After 12 days of incubation, cell numbers were counted and cells were analyzed for CD34 and CD38 expression by flow cytometry. Results are presented as the means (±SEM) of 3 separate experiments. Paired Student's t-test was performed comparing the 2 different growth conditions. *P < .05.