The chemokine stromal cell-derived factor-1 (SDF-1), and its receptor, CXCR-4, have been implicated in the homing and mobilization of human CD34+ cells. We show here that SDF-1 may also be involved in hematopoiesis, promoting the proliferation of human CD34+ cells purified from normal adult peripheral blood (PB). CXCR-4 was expressed on PB CD34+ cells. The amount of CXCR-4 on PB CD34+ cells was 10 times higher when CD34+ cells were purified following overnight incubation. CXCR-4 overexpression was correlated with a primitive PB CD34+ cell subset defined by a CD34high CD38lowCD71lowc-KitlowThy-1+antigenic profile. The functional significance of CXCR-4 expression was ascertained by assessing the promoting effect of SDF-1 on cell cycle, proliferation, and colony formation. SDF-1 alone increased the percentage of CD34+ cells in the S+G2/M phases and sustained their survival. In synergy with cytokines, SDF-1 increased PB CD34+ and CD34highCD38low cell expansion and colony formation. SDF-1 also stimulated the growth of colonies derived from primitive progenitors released from quiescence by anti–TGF-β treatment. Thus, our results shed new light on the potential role of this chemokine in the stem cell engraftment process, which involves migration, adhesion, and proliferation. Furthermore, both adhesion-induced CXCR-4 overexpression and SDF-1 stimulating activity may be of clinical relevance for improving cell therapy settings in stem cell transplantation.
Haematopoietic stem cells—role of calcium-sensing receptor in bone marrow homing**Comment on Adams GB, Chabner KT, Alley IR et al. Stem cell engraftment at the endosteal niche is specified by the calcium-sensing receptor. Nature 2006; 439: 599–603
