HSPC frequency is increased in BM with defect hypoxia-regulated Vegfa expression. (A) BM cellularity was determined by counting mononuclear cells from femur, tibia, and iliac crest from Vegfa^δ/δ or WT mice. Data are presented as ratio of WT BM cellularity and results shown are combined data from 8 independent experiments. Bars represent mean ± SD, **P = .0065, t test. (B) Total CFU frequency was measured by plating 2 × 10⁴ BM cells/mL in methylcellulose, with or without mVEGFA, followed by incubation in normoxia or hypoxia for 7 days. Results shown are data combined from 4 independent experiments. (C) The frequency of LSK cells in the BM was measured by FACS analysis. Representative FACS plots of lineage⁻ gated cells. (D) Percentage LSK cells in BM. (E) Total number of LSK cells per 2 × femur and tibia. Results shown in D-E are data combined from 5 independent experiments. Bars represent mean ± SD, n = 15-17 mice per genotype. P values are from t test. (F) The frequency of LSK CD34⁻ cells in BM was measured by FACS analysis. Representative FACS plots of LSK gated cells. (G) Percentage LSK CD34⁻ cells in BM. (H) Total number of LSK CD34⁻ cells per 2 × femur and tibia. Results shown in G-H are data combined from 4 independent experiments. Bars represent mean ± SD, n = 13 mice per genotype. P values are from t test.