SDF-1 enhances the expansion and maintenance of highly purified human hematopoietic progenitors

The stromal-derived factor-1 (SDF-1) chemokine and its putative receptor, CXCR4, have been implicated in hematopoiesis. Here we aim to characterize the effects of cytokine-induced CXCR4 expression and SDF-1 treatment on primitive human umbilical cord blood (CB) cells in vitro. Highly purified CD34+CD38-Lin-CXCR4- blood cells were capable of forming CD34+CXCR4+ cells during short-term liquid culture, but maintained distinct erythroid and myeloid progenitor composition, similar to the parent population prior to culture. In vitro, SDF-1 enhanced the expansion and differentiation of primitive CB cells in a manner that was dependent upon both the concentration of SDF-1 and the presence of specific cytokines. In the absence of cytokine addition, cultures seeded with CD34+CD38-Lin- cells demonstrated substantial cell death; however, the addition of SDF-1 alone preferentially increased progenitor cell frequency. Our study demonstrates that induction of CXCR4 expression does not alter the differentiative potential of human blood progenitors and suggests a role for SDF-1 as a growth factor required for human hematopoiesis.