title: High-resolution tracking of cell division suggests similar cell cycle kinetics of hematopoietic stem cells stimulated in vitro and in vivo.
abstract: The kinetics of proliferation of primitive murine bone marrow (BM) cells stimulated either in vitro with growth factors (fetal liver tyrosine kinase ligand 3 [FL], Steel factor [SF], and interleukin-11 [IL-11], or hyper-IL-6) or in vivo by factors active in myeloablated recipients were examined. Cells were first labeled with 5- and 6-carboxyfluorescein diacetate succinimidyl ester (CFSE) and then incubated overnight prior to isolating CFSE(+) cells. After 2 more days in culture, more than 90% of the in vivo lymphomyeloid repopulating activity was associated with the most fluorescent CFSE(+) cells (ie, cells that had not yet divided), although this accounted for only 25% of the repopulating stem cells measured in the CFSE(+) "start" population. After a total of 4 days in culture (1 day later), 15-fold more stem cells were detected (ie, 4-fold more than the day 1 input number), and these had become (and thereafter remained) exclusively associated with cells that had divided at least once in vitro. Flow cytometric analysis of CFSE(+) cells recovered from the BM of transplanted mice indicated that these cells proliferated slightly faster (up to 5 divisions completed within 2 days and up to 8 divisions completed within 3 days in vivo versus 5 and 7 divisions, respectively, in vitro). FL, SF, and ligands which activate gp130 are thus efficient stimulators of transplantable stem cell self-renewal divisions in vitro. The accompanying failure of these cells to accumulate rapidly indicates important changes in their engraftment potential independent of accompanying changes in their differentiation status.
authors.affiliation: Terry Fox Laboratory, British Columbia Cancer Agency, Vancouver, BC, Canada.
authors.forename: R A
authors.initials: RA
authors.lastname: Oostendorp
authors.forename: J
authors.initials: J
authors.lastname: Audet
authors.forename: C J
authors.initials: CJ
authors.lastname: Eaves
mesh_terms: D000818:Animals; D002453:Cell Cycle / Q000502:physiology*; D002455:Cell Division / Q000502:physiology*; D002478:Cells, Cultured; D003114:Colony-Forming Units Assay; D016895:Culture Media, Serum-Free; D005434:Flow Cytometry; D018380:Hematopoietic Stem Cell Transplantation; D006412:Hematopoietic Stem Cells / Q000166:cytology*; D051379:Mice; D020297:Mice, Congenic; D008810:Mice, Inbred C57BL
chemical_list: D016895:Culture Media, Serum-Free