Selectin-mediated rolling of hematopoietic stem and progenitor cells

We studied the interaction of human hematopoietic stem and progenitor cells (HSPC) from adult bone marrow (ABM) and fetal liver (FL) with E-, P-, and L-selectin immobilized in a flow chamber. CD34/sup +/ HSPC from both ABM and FL rolled on all the selectins, indicating the presence of selectin ligands on HSPC. Rolling was specific, and could be blocked by selectin monoclonal antibodies (mAbs), calcium chelation with EDTA, and fucoidan on P- and Lselectin. Rolling properties (velocity, rolling flux, etc.) differed according to expression of CD34 and CD38 cell surface markers. CD34/sup +/ ABM and FL cells roll more efficiently (to a greater extent and more slowly) than more differentiated CD34/sup -/ cells, especially on P- and L-selectin. Similarly, increased rolling efficiency was also seen with CD34/sup +/CD38/sup -/ ABM cells compared to CD34/sup +/CD38/sup +/ cells. Rolling of CD34/sup +/ ABM cells on P- selectin could be partially inhibited by mAb against PSGL-1, and was not inhibited by mAb against CD34. Our results provide direct evidence of selectin ligands on HSPC and show a correlation between the maturity of HSPC during development and rolling efficiency on selectins, suggesting a mechanism by which subsets of HSPC may home to the bone marrow.