Cell cycle analysis of fresh, ex vivo–cultured and BM- and spleen-homed MPB G₀CD34⁺ and G₁CD34⁺ cells.

Immunomagnetically selected MPB CD34⁺ cells were stained with Hst and PY, and CD34⁺ cells in G₀ or G₁ were isolated by cell sorting as described in “Materials and methods.” A sample from each sorted group was retained for cell cycle analysis at time zero (Fresh) and for initiating a short-term ex vivo culture (Ex vivo) that was maintained as described in the legend of Figure 2. Remaining cells from each group were transplanted into conditioned NOD/SCID mice, and 24, 48, and 72 hours AT, marrow (BM) and spleen (Spl) cells were recovered from individual mice, and human CFSE⁺ cells were isolated by flow cytometric cell sorting. Cell cycle status of all groups of cells was determined by PI staining. Number of measurements from 6 independent experiments for fresh samples is 4, for G₀CD34⁺ cells at 24 hours is 3, and for G₁CD34⁺ is 2; for G₀ and G₁CD34⁺ cells at 48 hours is 8 and for both groups at 72 hours is 1. Insufficient cell recovery (because of low cellularity after irradiation) precluded obtaining a measurement for spleen-homed G₁CD34⁺ cells 72 hours AT.