Cell cycle and functional differences between CD34+/CD38hi and CD34+/38lo human marrow cells after in vitro cytokine exposure.
The proliferation kinetics and clonogenic activity of CD34+/38hi (CD38hi) and CD34+/38lo (CD38lo) human marrow cells were measured before and after culturing the cells in vitro over a 6-day period in serum-deprived medium containing recombinant growth factors (interleukin-1 [IL-1], IL-3, IL-6, granulocyte colony-stimulating factor [G-CSF], granulocyte-macrophage [GM]-CSF, kit ligand, and erythropoietin). Before in vitro culture, 3% +/- 3% of the CD38lo and 13% +/- 2% of the CD38hi cells were in the S-phase of the cell cycle. The clonogenic activity of CD38hi cells was twofold greater than that of the CD38lo cells, as measured by colony-forming units (CFU) in short-term assays. However, CD38hi cells contained fewer pre-CFU than did the CD38lo cells, generating only 3 +/- 2 colonies per 1,000 cells after 4 weeks of culture on competent stromal layers, compared with 107 +/- 46 colonies per 1,000 cells from the CD38lo population. CD38hi and CD38lo cells exhibited distinctly different responses when cultured in serum-deprived medium supplemented with recombinant growth factors. After culturing cells for 24 hours, CD38lo cells essentially remained a noncycling population with only 5.1% +/- 3.0% of the cells cycling, whereas 44.2% +/- 6.9% of the CD38hi cells were in DNA synthesis. Gradually CD38lo cells were recruited into cycle, such that by 72 hours, approximately 28% of the CD38lo cells were in S-phase. However, during 6 days of culture, the percentage of cycling CD38lo cells never exceeded the proliferative response observed for CD38hi cells. Phenotype analysis conducted at day 6 indicated that 86% of the CD38hi population were no longer phenotypically CD34+/38hi, while 60% of CD38lo cells maintained a CD34+/38lo phenotype. Long-term cultures initiated with 6-day in vitro-expanded CD38lo cells showed approximately a twofold decrease in clonogenic activity attributable to a loss of erythroid precursors and a decrease in GM colonies. Thus, a proportion of CD38lo cells capable of generating CFU was maintained even after exposure to growth factors.
Reems
J A
JA
Clinical Research Division, Fred Hutchinson Cancer Research Center, Seattle, WA 98104.
Torok-Storb
B
B
D036541:ADP-ribosyl Cyclase; D051997:ADP-ribosyl Cyclase 1; D015703:Antigens, CD / Q000032:analysis*; D018952:Antigens, CD34; D000943:Antigens, Differentiation / Q000032:analysis*; D001854:Bone Marrow Cells; D002453:Cell Cycle; D002455:Cell Division / Q000187:drug effects; D002469:Cell Separation; D002478:Cells, Cultured; D016207:Cytokines / Q000494:pharmacology*; D006412:Hematopoietic Stem Cells / Q000187:drug effects* / Q000502:physiology; D006801:Humans; D008562:Membrane Glycoproteins
D015703:Antigens, CD; D018952:Antigens, CD34; D000943:Antigens, Differentiation; D016207:Cytokines; D008562:Membrane Glycoproteins; D036541:ADP-ribosyl Cyclase; C498154:CD38 protein, human; D051997:ADP-ribosyl Cyclase 1