Culture dramatically increases in vivo repopulating stem-cell activity of BM SP cells. (A) Freshly isolated adult CD45.2 BM SP cells (2, 5, 25, or 100) or their progenies after 10 days of culture were transplanted (together with 1 × 105 CD45.1 competitor BM cells per mouse, n = 5-8) into CD45.1 congenic mice. Peripheral blood engraftments at 4 weeks and 4 months after transplantation are shown. Error bars indicate SEM. (B) Limiting dilution analysis of the repopulating ability of BM SP cells before culture. Irradiated CD45.1 congenic mice were injected with 105 CD45.1 BM competitor cells and 2 (n = 7 mice), 5 (n = 6), 25 (n = 8), or 100 (n = 5) freshly isolated CD45.2 BM SP cells. Similar to Figure 1E, plotted is the percentage of recipient mice containing less than 1% CD45.2 lymphoid and myeloid subpopulations in nucleated peripheral blood cells 4 months after transplantation versus the number of injected cells. Input SP cells (100) resulted in 0% of negative mice, and this data point is not plotted. (C) Limiting dilution analysis of the repopulating ability of BM SP cells after culture. The same assay as used in panel B was carried out except the progenies of the input 2 (n = 5), 5 (n = 6), 25 (n = 4), or 100 SP cells (n = 5) after 10 days of culture were injected. The cultured progeny of 25 or 100 input SP cells resulted in 0% of negative mice, and the data points are not plotted.
