The effect of short G-CSF administration on the numbers and clonogenic efficiency of hematopoietic progenitor cells in bone marrow and peripheral blood of normal donors.

We have analysed the cellularity, the number of clonogenic cells and their clonogenic efficiency (the number of clonogenic cells/2 x 10(5) MNC) in peripheral blood (PB) and bone marrow (BM) during and after filgrastim (rhG-CSF) mobilization of CD34+ cells in 12 healthy donors for allogeneic stem cell donation. G-CSF was administrated subcutaneously for 5 consecutive days at a dose of 10 micrograms/kg/day. WBC, MNC, CD34+ cell counts, CFU-GM and BFU-E assays in PB were performed at baseline and then daily 12 hours after each G-CSF dose. BM was assayed before start (day 1) and after the last dose (day 6) of G-CSF. Results are given as medians, with ranges in parentheses. In PB the total WBC and MNC increased 7.4-fold (6.0-12.3) and 3.3-fold (1.5-9.4), respectively, reaching a peak of 49.4 x 10(9)/l (32.5-66.6) on day 6 for WBC and 6.28 x 10(9)/l (4.7-13.3) for MNC on day 5. CD34+ cell number reached a peak value of 48.0 x 10(6)/l (45.6-285) on day 6 whereas CFU-GM and BFU-E reached their peaks on day 5, 0.95 x 10(4)/ml (0.05-6.08) and 1.04 x 10(4)/ml, respectively. CFU-MIX, not detectable at baseline, reached a peak of 0.95 x 10(4)/ml (0.006-0.51) on day 5 as well. This was accompanied by an increase in CFU-GM, BFU-E and CFU-MIX clonogenic efficiency: 23-fold (3-150), 9.75-fold (2.2-27.8) and 20-fold (2.5-210), respectively. In BM the total WBC number increased 2.5-fold (1.3-4.9) from the baseline value of 52.6 x 10(9)/l (7.9-137.0) whereas the MNC count increased 2.0-fold (0.81-3.7) from a baseline of 13.6 x 10(9)/l (3.5-54.8). This was, however, not significant. The number of CD34+ cells increased significantly 2.9-fold (0.8-8.3). In 8 donors CFU-MIX were detectable before but not after G-CSF treatment. A similar decrease in CFU-GM and BFU-E clonogenic efficiency occurred but was not significant. CFU-GM and BFU-E numbers did not change. We conclude that the total body numbers of lineage committed progenitors increased during G-CSF administration, which indicate their proliferation in addition to mobilization. The effect of G-CSF on the number of more primitive progenitors in BM is less clear and needs further investigation.