Current mechanistic scenarios in hematopoietic stem/progenitor cell mobilization.

Uncovering the molecular mechanisms governing the exit of stem/progenitor cells from bone marrow to peripheral blood at steady state or after their enforced migration has been an ongoing challenge. Recently, however, several new avenues or paradigms in mobilization have emerged from ever-expanding work in humans subjected to granulocyte colony-stimulating factor (G-CSF) mobilization, as well as from studies in normal and gene-deficient mouse models. Although these developments represent notable advances that met with considerable excitement, they have been quenched by surprising vacillations in subsequent research. This perspective highlights recent developments in mobilization along with their controversies. A full understanding of the directional cues that control the migratory behavior and the fate of stem/progenitor cells once they migrate out of bone marrow will await further experimentation, aiming to bridge our current gaps in knowledge.