DIFFERENT ADHESIVE CHARACTERISTICS AND VLA-4 EXPRESSION OF CD34(+) PROGENITORS IN G(0) G(1) VERSUS S+G(2)/M PHASES OF THE CELL-CYCLE/

We identified the cell cycle status of CD34(+) cells of steady-state h one marrow (BM) and peripheral blood (PB) obtained from healthy volunt eers, 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 con trast, regardless of whether G-CSF treatment was performed, less than 2% of CD34(+) cells in PB were cycling. BM CD34(+) cells showed greate r VLA-4 expression and adherence to stromal cells than PB CD34(+) cell s. In addition, when cycling and dormant BM CD34(+) cells were analyze d separately, the cells in S+G(2)/M phase expressed more VLA-4 and adh ered to the stromal cell monolayer more efficiently than the cells in G(0)/G(1) phase. Furthermore, this adhesion of CD34(+) cells to the st romal cell layer was almost completely inhibited by anti-VLA-4 antibod y, 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 i n adhesiveness mediated by VLA-4 in the hematopoietic microenvironment . (C) 1998 by The American Society of Hematology.