Similar in vivo repopulating activity of neonatal and adult CD49f⁺cells when cotransplanted with CD34⁺CB “helper” cells. (A) Design of a cotransplantation strategy to compare the regenerative potential of CD49f⁺ cells isolated from donors of different ages. (B) Flow-cytometric analysis of the cells in a representative BM aspirate obtained from a mouse that had undergone cotransplantation 12 weeks earlier with CB CD49f⁺ cells and GFP-labeled CD34⁺ CB cells. (C-D) Percentage of human CD49f⁺ cell (GFP⁻) (C), and NM, B-lymphoid, erythroid, and CD34⁺ progeny (D) from input CB, young adult BM, or aged adult BM measured in the total number of viable cells present in the BM aspirate obtained at each time point assessed. Values indicate the geometric mean of pooled values from all mice in each group assessed in 2 independent experiments (2-3 mice per donor per experiment). Bars indicate the geometric means ± 1 standard error of the mean (SEM). (E) Linear regression analyses of CD49f⁺-progeny (GFP⁻) and GFP⁺ chimerism levels for CB (left), young adult BM (center), and aged adult BM (right). Points indicate paired results within each individual mouse at each different time point assessed after transplant. Symbols indicate mice that had undergone transplantation with different donors of the CD49f⁺ cells tested.