Chemotaxis of primitive hematopoietic cells in response to stromal cell-derived factor-1

Stromal cell-derived factor-1 (SDF-1) provides a potent chemotactic stimulu s for CD34(+) hematopoietic cells. We cultured mobilized peripheral blood ( PB) and umbilical cord blood (CD) for up to 5 weeks and examined the migrat ory activity of cobblestone area-forming cells (CAFCs) and long-term cultur e-initiating cells (LTC-ICs) in a transwell assay. In this system, SDF-1 or MS-5 marrow stromal cells placed in the lower chamber induced transmembran e and transendothelial migration by 2- and 5-week-old CAFCs and LTC-ICs in 3 hours. Transmigration was blocked by preincubation of input CD34(+) cells with antibody to CXCR4. Transendothelial migration of CB CAFCs and LTC-ICs was higher than that of PB. We expanded CD34(+) cells from CB in serum-fre e medium with thrombopoietin, flk-2 ligand, and c-kit ligand, with or witho ut IL-3 and found that CAFCs cultured in the absence of IL-3 had a chemotac tic response equivalent to noncultured cells, even after 5 weeks. However, addition of IL-3 to the culture reduced this response by 20-50%. These data indicate that SDF-1 induces chemotaxis of primitive hematopoietic cells si gnaling through CXCR4 and that the chemoattraction could be downmodulated b y culture ex vivo.