Purified human fetal BM CD34⁺ thy-1⁺ cells from each sample (average 450,000 to 500,000 cells) were divided into 2 fractions. One fraction (approximately 400,000 cells) was used to inject 40 SCID-hu mice (20 thy/liv mice and 20 bone mice, and 10,000 cells per graft). The other fraction (about 10,000 cells) was used to initiate ex vivo expansion culture (20 cells per well and a total of 5 96-well plates) with the combination of IL-3, IL-6, GM-CSF, SCF, and LIF for 5 weeks. Ex vivo–expanded CD34⁺ thy-1⁺cells were than sorted from the cultures (approximately 450,000 cells) and injected into 40 SCID-hu mice (again, 20 thy/liv mice and 20 bone mice, and 10,000 cells per graft). As a negative control, ex vivo–expanded cells from CD34⁺ thy-1⁺/negative wells (without detectable CD34⁺ thy-1⁺ cells) were injected into 20 SCID-hu mice (10 thy/liv mice and 10 bone mice, and 10,000 cells per graft). Frequency of donor-reconstituted animals and percentage of donor-derived hematopoietic cells in the reconstituted animals were determined at 3 to 4 months after stem cell injection. These data are compiled from 3 independent experiments using different donor BM samples. The frequency of reconstituted animals is presented as the total number of reconstituted animals divided by the total number of animals used in the experiments. The percentage of donor-derived cells represents the mean ± SD of all reconstituted animals from the same experiments.

Abbreviation: NA, not applicable.