The α-chemokine stromal-derived factor 1 (SDF-1), which binds to the CXCR4 receptor, directs migration and homing of CXCR4+ hematopoietic stem/progenitor cells (HSPCs) to bone marrow (BM) stem cell niches. Nevertheless, it is also known that CXCR4-/- fetal liver-derived hematopoietic stem cells engraft into BM and that blockade of CXCR4 by its antagonist AMD3100 does not prevent engraftment of HSPCs. Because of this finding of SDF-1-CXCR4-independent BM homing, the unique role of SDF-1 in HSPC homing has recently been challenged. While SDF-1 is the only chemokine that chemoattracts HSPCs, other chemoattractants for these cells have recently been described, including the bioactive phosphosphingolipid sphingosine-1-phosphate (S1P). To address the potential role of S1P in homing of HSPCs to BM, we performed hematopoietic transplants into mice deficient in BM-expressed sphingosine kinase 1 (Sphk1-/-) using hematopoietic cells from normal control mice as well as cells from mice in which floxed CXCR4 (CXCR4fl/fl) was conditionally deleted. We observed the presence of a homing and engraftment defect in HSPCs of Sphk1-/- mice that was particularly profound after transplantation of CXCR4-/- BM cells. Thus, our results indicate that BM-microenvironment-expressed S1P plays a role in homing of HSPCs. They also support the concept that, in addition to the SDF-1-CXCR4 axis, other chemotactic axes are also involved in homing and engraftment of HSPCs.
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This work was supported by NIH grants 2R01 DK074720 and R01HL112788 and the Stella and Henry Hoenig Endowment to MZR and University of www.impactjournals.com/oncotarget 18827 Oncotarget Kentucky Clinical and Translational Science Pilot Award (UL1TR000117), the UK COBRE Early Career Program (P20 GM103527), and NIH Grant R56 HL124266.
Adamiak, Mateusz; Borkowska, Sylwia; Wysoczynski, Marcin; Suszynska, Malwina; Kucia, Magda; Rokosh, Gregg; Abdel-Latif, Ahmed; Ratajczak, Janina; and Ratajczak, Mariusz Z., "Evidence for the Involvement of Sphingosine-1-Phosphate in the Homing and Engraftment of Hematopoietic Stem Cells to Bone Marrow" (2015). Internal Medicine Faculty Publications. 83.