Hematopoietic stem cells from the marrow of mice treated with Flt3 ligand are significantly expanded but exhibit reduced engraftment potential.
BACKGROUND
Hematopoietic stem cells (HSC) can be significantly expanded by hematopoietic growth factors. Flt3 ligand (FL) is a hematopoietic growth factor that induces proliferation and mobilization of HSC into the peripheral blood. We previously reported that FL-mobilized HSC exhibit superior engraftment potential. The engraftment potential of FL-expanded HSC in the bone marrow compartment has not been evaluated. In this study, we investigated the effect of in vivo administration of FL on the engraftment potential of HSC expanded in the marrow.


METHODS
B10.BR (H-2k) donor mice were treated for 10 days with 10 microg of FL per day. Partially conditioned allogeneic B10 (H-2b) recipients received whole bone marrow. Purified HSC (c-Kit+/Sca1+/lin-) from the marrow were also transplanted in ablated syngeneic B10.BR recipients.


RESULTS
FL treatment significantly expanded HSC in the marrow compartment. The absolute number of T cells and granulocytes were unchanged whereas dendritic cells, facilitating cells, and HSC were significantly increased in the bone marrow of donor mice treated with FL compared with untreated mice. Mice conditioned with 700 cGy and transplanted with FL-treated allogeneic bone marrow showed a significantly lower rate of engraftment (14%) compared with recipients of bone marrow from untreated mice (100%). Syngeneic recipients transplanted with 500, 1000, 2000, or 3000 purified HSC from FL-treated donors also showed reduced long-term survival compared with mice transplanted with HSC from untreated donors. Cell cycle analysis revealed that significantly more bone marrow HSC were in cycle after FL treatment compared with unmanipulated controls.


CONCLUSIONS
These data show that FL treatment for 10 days induces proliferation of HSC but reduces the engraftment potential of HSC harvested from the marrow. The reduced syngeneic engraftment of HSC indicates that FL treatment induces intrinsic changes in HSC, resulting in failure of long-term engraftment or self-renewal despite no change in characteristic phenotype of HSC.
Mueller
Yvonne M
YM
Institute for Cellular Therapeutics, University of Louisville, Louisville, Kentucky, 40202-1760, USA.
Cramer
Daniel E
DE
Huang
Yiming
Y
Exner
Beate G
BG
Ildstad
Suzanne T
ST
D000818:Animals; D001224:Aspartic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D001854:Bone Marrow Cells / Q000166:cytology / Q000187:drug effects*; D005260:Female; D006410:Hematopoiesis / Q000187:drug effects; D019650:Hematopoietic Stem Cell Mobilization / Q000379:methods; D018380:Hematopoietic Stem Cell Transplantation; D006412:Hematopoietic Stem Cells / Q000166:cytology* / Q000187:drug effects; D008297:Male; D008565:Membrane Proteins / Q000494:pharmacology*; D051379:Mice; D008810:Mice, Inbred C57BL; D008815:Mice, Inbred Strains; D011994:Recombinant Proteins / Q000494:pharmacology; D018183:Transplantation Chimera; D014184:Transplantation, Homologous; D014185:Transplantation, Isogeneic
D008565:Membrane Proteins; D011994:Recombinant Proteins; C093260:benzyloxycarbonyl-Asp-CH2OC(O)-2,6-dichlorobenzene; C084881:flt3 ligand protein; D001224:Aspartic Acid