title: Fms-related tyrosine kinase 3 expression discriminates hematopoietic stem cells subpopulations with differing engraftment-potential: identifying the most potent combination.
abstract: BACKGROUND
  Fms-related tyrosine kinase 3 (Flt3)-ligand (FL) promotes the proliferation, differentiation, development, and mobilization of hematopoietic cells. We previously found that FL-mobilized hematopoietic stem cells (HSC) engraft efficiently, whereas FL-expanded bone marrow HSC do not. The function of FL-mobilized c-Kit(+) Sca-1(+)Lin(-)(KSL) subpopulations has not been systematically evaluated. A precise definition of the repopulating ability is needed to define which HSC subpopulations are critical for long-term chimerism and tolerance induction. FL significantly mobilized c-Kit(hi) and c-Kit(lo) Sca-1(+)Lin(-) cells into peripheral blood (PB). Here, we evaluated the influence of Flt3 expression on long-term repopulating ability of HSC subpopulations.
  
  
  METHODS
  c-Kit(hi) or c-Kit(lo) KSL cells were sorted from PB of FL-treated green fluorescent protein-positive donors. The function of these cells was evaluated using competitive reconstitution assays, colony-forming units spleen, and colony forming cell assays. The function of c-Kit(hi) CD34(-)Flt3(-) KSL, c-Kit CD34(+)Flt3(-) KSL, c-Kit(hi) CD34(+)Flt3(+) KSL were investigated in an in vivo transplantation model.
  
  
  RESULTS
  Only FL-mobilized PB c-Kit(hi) KSL cells exhibited high spleen colony-forming unit activity, generated high numbers of both lymphoid and myeloid colonies in vitro, and rescued ablated recipients. FL-mobilization expanded both c-Kit(hi) CD34(+)Flt3(-) cells (short-term HSC) and c-Kit(hi) CD34(-)Flt3(-) KSL cells (long-term HSC). There was a significant decrease in c-Kit CD34Flt3 KSL late multipotent progenitors in PB. A combination of c-Kit(hi) CD34Flt3 and c-Kit CD34(+)Flt3(-) KSL cells offered the most effective rescue of ablated recipients.
  
  
  CONCLUSIONS
  These data suggest that engraftment of purified HSC is influenced by both short- and long-term repopulating populations and that Flt3 expression may be useful for selecting the most critical HSC subpopulations for transplantation.
authors.affiliation: Institute for Cellular Therapeutics, University of Louisville, Louisville, KY 40202-1760, USA.
authors.forename: Yiming
authors.initials: Y
authors.lastname: Huang
authors.forename: Mariusz Z
authors.initials: MZ
authors.lastname: Ratajczak
authors.forename: Ryan
authors.initials: R
authors.lastname: Reca
authors.forename: Hong
authors.initials: H
authors.lastname: Xu
authors.forename: Michael
authors.initials: M
authors.lastname: Tanner
authors.forename: Francine
authors.initials: F
authors.lastname: Rezzoug
authors.forename: Lala-Rukh
authors.initials: LR
authors.lastname: Hussain
authors.forename: Isabelle
authors.initials: I
authors.lastname: Fugier-Vivier
authors.forename: Roberto
authors.initials: R
authors.lastname: Bolli
authors.forename: Suzanne T
authors.initials: ST
authors.lastname: Ildstad
mesh_terms: D000818:Animals; D018952:Antigens, CD34 / Q000032:analysis; D002454:Cell Differentiation; D019650:Hematopoietic Stem Cell Mobilization; D018380:Hematopoietic Stem Cell Transplantation; D006412:Hematopoietic Stem Cells / Q000166:cytology*; D008297:Male; D008565:Membrane Proteins / Q000494:pharmacology; D051379:Mice; D008810:Mice, Inbred C57BL; D051941:fms-Like Tyrosine Kinase 3 / Q000502:physiology*
chemical_list: D018952:Antigens, CD34; D008565:Membrane Proteins; C084881:flt3 ligand protein; C497971:Flt3 protein, mouse; D051941:fms-Like Tyrosine Kinase 3