title: The murine long-term multi-lineage renewal marrow stem cell is a cycling cell.
abstract: Prevailing wisdom holds that hematopoietic stem cells (HSCs) are predominantly quiescent. Although HSC cycle status has long been the subject of scrutiny, virtually all marrow stem cell research has been based on studies of highly purified HSCs. Here we explored the cell cycle status of marrow stem cells in un-separated whole bone marrow (WBM). We show that a large number of long-term multi-lineage engraftable stem cells within WBM are in S/G2/M phase. Using bromodeoxyuridine, we show rapid transit through the cell cycle of a previously defined relatively dormant purified stem cell, the long-term HSC (LT-HSC; Lineage(-)/c-kit(+)/Sca-1(+)/Flk-2(-)). Actively cycling marrow stem cells have continually changing phenotype with cell cycle transit, likely rendering them difficult to purify to homogeneity. Indeed, as WBM contains actively cycling stem cells, and highly purified stem cells engraft predominantly while quiescent, it follows that the population of cycling marrow stem cells within WBM are lost during purification. Our studies indicate that both the discarded lineage-positive and lineage-negative marrow cells in a stem cell separation contain cycling stem cells. We propose that future work should encompass this larger population of cycling stem cells that is poorly represented in current studies solely focused on purified stem cell populations.
authors.affiliation: Department of Medicine, Rhode Island Hospital, Providence, RI, USA.
authors.forename: L R
authors.initials: LR
authors.lastname: Goldberg
authors.affiliation: Department of Medicine, Rhode Island Hospital, Providence, RI, USA.
authors.forename: M S
authors.initials: MS
authors.lastname: Dooner
authors.affiliation: Department of Medicine, Rhode Island Hospital, Providence, RI, USA.
authors.forename: K W
authors.initials: KW
authors.lastname: Johnson
authors.affiliation: Department of Medicine, Rhode Island Hospital, Providence, RI, USA.
authors.forename: E F
authors.initials: EF
authors.lastname: Papa
authors.affiliation: Department of Medicine, Rhode Island Hospital, Providence, RI, USA.
authors.forename: M G
authors.initials: MG
authors.lastname: Pereira
authors.affiliation: Department of Medicine, Rhode Island Hospital, Providence, RI, USA.
authors.forename: M
authors.initials: M
authors.lastname: Del Tatto
authors.affiliation: Department of Medicine, Rhode Island Hospital, Providence, RI, USA.
authors.forename: D M
authors.initials: DM
authors.lastname: Adler
authors.affiliation: Department of Medicine, Rhode Island Hospital, Providence, RI, USA.
authors.forename: J M
authors.initials: JM
authors.lastname: Aliotta
authors.affiliation: Department of Medicine, Rhode Island Hospital, Providence, RI, USA.
authors.forename: P J
authors.initials: PJ
authors.lastname: Quesenberry
mesh_terms: D000818:Animals; D001854:Bone Marrow Cells / Q000166:cytology*; D002453:Cell Cycle; D019070:Cell Lineage; D005434:Flow Cytometry; D006412:Hematopoietic Stem Cells / Q000166:cytology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL