Biologic activity of rhHAPO in murine system. (A) Bone marrow was obtained from BALB/c mice. The cells were seeded in 24-wells plates at a cell density of 2 × 10⁶/mL in long-term culture system with or without rhHAPO (100 ng/mL). After culture for 4 weeks, the cells were detached and subjected to FACS analysis. FACS analysis showed that rhHAPO significantly increased the number of the CD34⁺, Sca-1⁺, and flk-1⁺ cells as compared with control cells.^*P < .05. (B) Colony formation from bone marrow long-term culture-initiating cells (LTC-ICs) in the absence (i) or presence (ii) of rhHAPO. Original magnification × 100.