Intracellular, but not extracellular, PAI-1 regulates the motility of HSPCs. (A) Schema for long-term reciprocal transplantation experiments. (B) Representative flow cytometric profiles and MFI (n = 12) for MT1-MMP expression in LSK CD34⁻ cells of primary recipients. (C-D) Percentages of circulating LSK cells (C) and the number of circulating CFCs (D) in PB samples obtained from the primary recipients of reciprocal transplantation experiments (n = 12). (E-F) Percentages of PKH26⁺ cells (E) and the number of CFCs (F) homed to the BM of secondary recipients (n = 12). (B-F) Means ± SD of 3 independent experiments are shown.