The chemokine GROβ mobilizes early hematopoietic stem cells characterized by enhanced homing and engraftment

Abstract

Mobilized peripheral blood hematopoietic stem cells (PBSCs) demonstrate accelerated engraftment compared with bone marrow; however, mechanisms responsible for enhanced engraftment remain unknown. PBSCs mobilized by GROβ (GROβΔ4/CXCL2Δ4) or the combination of GROβΔ4 plus granulocyte colonystimulating factor (G-CSF) restore neutrophil and platelet recovery faster than G-CSF-mobilized PBSCs. To determine mechanisms responsible for faster hematopoietic recovery, we characterized immunophenotype and function of the GROβ-mobilized grafts. PBSCs mobilized by GROβΔ4 alone or with G-CSF contained significantly more Sca-1+-ckit +-lineage+ (SKL) cells and more primitive CD34 --SKL cells compared with cells mobilized by G-CSF and demonstrated superior competitive long-term repopulation activity, which continued to increase in secondary and tertiary recipients. GROβΔ4- mobilized SKL cells adhered better to VCAM-1+ endothelial cells compared with G-CSF-mobilized cells. GROβΔ4-mobilized PBSCs did not migrate well to the chemokine stromal derived factor (SDF)-1α in vitro that was associated with higher CD26 expression. However, GROβΔ4-mobilized SKL and c-Kit+ lineage- (KL) cells homed more efficiently to marrow in vivo, which was not affected by selective CXCR4 and CD26 antagonists. These data suggest that GROβΔ4-mobilized PBSCs are superior in reconstituting long-term hematopoiesis, which results from differential mobilization of early stem cells with enhanced homing and long-term repopulating capacity. In addition, homing and engraftment of GROβΔ4-mobilized cells is less dependent on the SDF-1α/CXCR4 axis. © 2007 by The American Society of Hematology.