CD26 inhibition enhanced engraftment of Flk2⁻CD34⁻ HSCs. (A) Flk2⁻CD34⁻ LT-HSCs and Flk2⁻CD34⁺ ST-HSCs were isolated from the BM of donor mice (CD45.2), either treated with 5mM Dip A, a CD26 inhibitor, or left untreated and IV-injected into lethally irradiated recipient mice (CD45.1). Ten, 18, and 30 days after cell transplantation, BM aspirates from recipient mice were analyzed by flow cytometry to measure the percentage of donor cells (expressing CD45.2) found in recipient tissues. (B) Results of the engraftment of donor cells treated with Dip A [red] and control [blue] in the BM of recipient mice were determined at each time point for both the ST-HSCs (left panels) and the LT-HSCs (right panels). Data presented are the mean ± SD of >5 mice from each group at the different time points (*P = .02). (C) A representative analysis of donor cell engraftment for both ST-HSCs (left panel) and LT-HSCs (right panel) that were either treated with Dip A (red) or left untreated (blue).