RESUMO
BACKGROUND: Rotor off (R/O) fraction obtained by counterflow centrifugal elutriation (CCE) contains small number of T cells and many hematopoietic stem cells. Since megakaryocytes and its progenitors are larger than other cells in bone marrow, it may be easier to be separated by CCE and newly applied to hematopoietic stem cell transplantation (HSCT) for early megakaryocytes reconstitution. METHODS: The marrow cells of BALB/c mice in each group (17, 25, 28mL/min, and R/O fraction) were cultured for quantifying CFU-MK and measured after 10 days. BALB/c mice were lethally irradiated and transplanted with R/O cells. The dosages of transplanted cells were 5x104 in Group A, 5x105 in Group B, and 5x106 in Group C. The platelet counts in peripheral blood were measured up to post-transplant day 14. RESULTS: After CCE, recovery rate of the loaded cells was 82.2% and the R/O fraction was 35.9%. Most CFU-MK were formed in R/O fraction, and Group C showed the fastest recovery. Group A couldn't reach the level of 100x109/L until post-transplant day 14, and Group B showed slower recovery compared to Group C. All 5 mice survived in Group C, but 2 out of 5 mice survived in Group A and B. CONCLUSIONS: R/O fraction contains higher number of megakaryocyte progenitors, and CCE could be an effective method for separating megakaryocyte progenitors essential for reconstituting platelet after HSCT. The cell dose of 5x106 was required for the effective recovery of platelet and the survival of BALB/c mice in syngeneic bone marrow transplantation with R/O cells.