The chemokine SDF-1 is a chemoattractant for human CD34+ hematopoietic progenitor cells and provides a new mechanism to explain the mobilization of CD34+ progenitors to peripheral blood

Hematopoietic progenitor cells migrate in vitro and in vivo towards a gradient of the chemotactic factor stromal cell-derived factor-1 (SDF-1) produced by stromal cells. This is the first chemoattractant reported for human CD34⁺ progenitor cells. Concentrations of SDF-1 that elicit chemotaxis also induce a transient elevation of cytoplasmic calcium in CD34⁺ cells. SDF-1-induced chemotaxis is inhibited by pertussis toxin, suggesting that its signaling CD34⁺ cells is mediated by seven transmembrane receptors coupled to G₁ proteins. CD34⁺ cells migrating of SDF-1 include cells with a more primitive (CD34⁺/CD38^- or CD34⁺/DR^-) phenotype as well as CD34⁺ cells phenotypically committed to the erythroid, lymphoid and myeloid lineages, including functional BFU-E, CFU-GM, and CFU- MIX progenitors. Chemotaxis of CD34⁺ cells in response to SDF-1 is increased by IL-3 in vitro and is lower in CD34⁺ progenitors from peripheral blood than in CD34⁺ progenitors from bone marrow, suggesting that an altered response to SDF-1 may be associated with CD34 progenitor mobilization.