CFU-F efficiency. Efficiency of self renewal assessed by rate of colony formation in CFU-F assays. Columns illustrate mean CFU-F efficiency ± standard deviation. Six independent CFU-F assays were performed for each cell populations. Statistical data analysis: multiple variance analysis with repeated measurements; Tukey post-hoc-test for multiple mean value comparisons. P values < 0.05 were considered statistically significant. Significant differences among cell sources were denoted by a, b and c (all p-values < 0.019).