IGFBP2 supports the repopulation of HSCs in the BM environment. (A) A schematic representation of BM transplantation. (B) CD45.1 total BM cells (5 × 10⁵) were transplanted into lethally irradiated CD45.2 WT or IGFBP2-null recipients for 4 months. Subsequently, 1 × 10⁶ CD45.1 total BM cells from primary WT or IGFBP2-null recipients were cotransplanted with 1 × 10⁵ CD45.2 total BM cells into secondary CD45.2 recipients (n = 9). Shown are donor repopulations at indicated time after transplantation. Data shown are representative of 2 independent experiments that gave similar results. (C) Different donor lineages from long-term repopulation were determined. (D) One hundred twenty CD45.2 donor Lin⁻Sca-1⁺Kit⁺Flk2⁻CD34⁻ cells were cocultured with 360 WT or IGFBP2-null CD45⁻ cells in STF medium containing 10% FBS for 5 days. The total mixture of cultured cells were then cotransplanted with 1 × 10⁵ CD45.1 total BM cells into CD45.1 recipients (n = 5). Shown are donor repopulations at indicated time after transplantation. (E) One hundred and twenty CD45.2 donor Lin⁻Sca-1⁺Kit⁺Flk2⁻CD34⁻ cells were cultured alone or cocultured with 360 IGFBP2-null CD45⁻ cells in serum-supplemented STF medium, with or without IGFBP2, for 5 days (n = 5). Shown is donor repopulation at indicated time, representative of 2 independent experiments that gave similar results.