FGF-2 is required for HSPC expansion under stress-induced conditions, but not during steady-state conditions. FVB/N WT or FGF-2 KO mice were treated with either vehicle or PTH (n > 8). (A-B) Percentage of BM or spleen SKL cells as determined by flow cytometry. (C) FGF-2 protein levels as determined by ELISA in the BM supernatants of WT mice after PTH treatment. (D) FGF-2 protein levels as determined by ELISA in the BM supernatants of WT mice after irradiation or 5-FU treatments (n > 6). FVB/N WT or FGF-2 KO mice were treated with single dose of sublethal irradiation and killed at the indicated time points (n > 4). (E-F) Numbers of BM SKL and BM CD34⁻ SKL per femur of FVB/N WT or FGF-2 KO mice as determined by flow cytometry. (G-H) Numbers of peripheral WBC counts and peripheral RBC counts of FVB/N WT or FGF-2 KO mice. (I) Survival curve for FVB/N WT or FGF-2 KO mice treated once with a lethal dose of TBI followed by transplantation with minimal dose of 5 × 10⁴ BM cells from either WT or FGF-2 KO mice (n > 12). *P < .05; **P < .01. Data shown are means ± SEM.