Different adhesive characteristics and VLA-4 expression of CD34+ progenitors in G0/G1 versus S+G2/M phases of the cell cycle

We identified the cell cycle status of CD34(+) cells of steady-state hone marrow (BM) and peripheral blood (PB) obtained from healthy volunteers, and those of apherasis PB samples collected from healthy donors who had been administered granulocyte colony-stimulating factor (G-CSF). More than 10% of CD34(+) cells in BM were in S+G(2)/M phase. In contrast, regardless of whether G-CSF treatment was performed, less than 2% of CD34(+) cells in PB were cycling. BM CD34(+) cells showed greater VLA-4 expression and adherence to stromal cells than PB CD34(+) cells. In addition, when cycling and dormant BM CD34(+) cells were analyzed separately, the cells in S+G(2)/M phase expressed more VLA-4 and adhered to the stromal cell monolayer more efficiently than the cells in G(0)/G(1) phase. Furthermore, this adhesion of CD34(+) cells to the stromal cell layer was almost completely inhibited by anti-VLA-4 antibody, Taken together, these results suggest that CD34(+) progenitors in G(0)/G(1) phase of the cell cycle differ from those in S+G(2)/M phase in adhesiveness mediated by VLA-4 in the hematopoietic microenvironment. (C) 1998 by The American Society of Hematology.