Kinetics of engraftment of CD34(-) and CD34(+) cells from mobilized blood differs from that of CD34(-) and CD34(+) cells from bone marrow

Objective. Mobilized peripheral blood (PB) progenitors are increasingly use d in autologous and allogeneic transplantation. However, the short- and lon g-term engraftment potential of mobilized PB or bone marrow (BM) has not be en directly compared. Although several studies showed that BM-derived Lin(- )CD34(-) cells contain hemopoietic progenitors, no studies have addressed w hether Lin(-)CD34(-) cells from mobilized PB contain hemopoietic progenitor s. Here, we compared the short- and long-term engraftment potential of CD34 (+) cells and Lin(-)CD34(-) cells in BM and PB of normal donors who receive d 5 days of granulocyte colony-stimulating factor (G-CSF), Materials and Methods, 35 x 10(3) CD34(+) or Lin(-)CD34(-) cells from G-CSF mobilized BM and PB of normal donors were transplanted in 60-day-old fetal sheep. Animals were evaluated 2 and 6 months after transplantation for hum an hemopoietic cells. In addition, cells recovered after 2 months from feta l sheep were serially passaged to secondary and tertiary recipients to asse ss long-term engrafting cells. Results, Mobilized PB CD34(+) cells supported earlier development of human hemopoiesis than BM CD34(+) cells. When serially transferred to secondary a nd tertiary recipients, earlier exhaustion of human hematopoiesis was seen for PB than BM CD34(+) cells. A similar degree of chimerism was seen for Li n(-)CD34(-) cells from PB or BM in primary recipients, We again observed ea rlier exhaustion of human hemopoiesis with serial transplantation of PB tha n BM Lin(-)CD34(-) cells, Conclusions, Differences exist in the short- and long-term repopulating abi lity of cells in PB and BM from G-CSF mobilized normal donors, and this is independent of the phenotype, Studies are ongoing to examine if this reflec ts intrinsic differences in the repopulating potential between progenitors from PB and BM, or a lower frequency of long-term repopulating cells in PB than BM CD34(+) and Lin(-)CD34(-) cells, that may not be apparent if larger numbers of cells are transplanted. (C) 2000 International Society for Expe rimental Hematology, Published by Elsevier Science Inc.