title: Essential role for the p55 tumor necrosis factor receptor in regulating hematopoiesis at a stem cell level.
abstract: Hematopoietic stem cell (HSC) self-renewal is a complicated process, and its regulatory mechanisms are poorly understood. Previous studies have identified tumor necrosis factor (TNF)-alpha as a pleiotropic cytokine, which, among other actions, prevents various hematopoietic progenitor cells from proliferating and differentiating in vitro. However, its role in regulating long-term repopulating HSCs in vivo has not been investigated. In this study, mice deficient for the p55 or the p75 subunit of the TNF receptor were analyzed in a variety of hematopoietic progenitor and stem cell assays. In older p55(-/-) mice (>6 mo), we identified significant differences in their hematopoietic system compared with age-matched p75(-/-) or wild-type counterparts. Increased marrow cellularity and increased numbers of myeloid and erythroid colony-forming progenitor cells (CFCs), paralleled by elevated peripheral blood cell counts, were found in p55-deficient mice. In contrast to the increased myeloid compartment, pre-B CFCs were deficient in older p55(-/-) mice. In addition, a fourfold decrease in the number of HSCs could be demonstrated in a competitive repopulating assay. Secondary transplantations of marrow cells from primary recipients of p55(-/-) marrow revealed impaired self-renewal ability of p55-deficient HSCs. These data show that, in vivo, signaling through the p55 subunit of the TNF receptor is essential for regulating hematopoiesis at the stem cell level.
authors.affiliation: Department of Pediatric Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts 02115, USA. vivienne_rebel@dfci.harvard.edu
authors.forename: V I
authors.initials: VI
authors.lastname: Rebel
authors.forename: S
authors.initials: S
authors.lastname: Hartnett
authors.forename: G R
authors.initials: GR
authors.lastname: Hill
authors.forename: S B
authors.initials: SB
authors.lastname: Lazo-Kallanian
authors.forename: J L
authors.initials: JL
authors.lastname: Ferrara
authors.forename: C A
authors.initials: CA
authors.lastname: Sieff
mesh_terms: D000818:Animals; D015703:Antigens, CD / Q000502:physiology*; D002453:Cell Cycle; D002455:Cell Division; D006410:Hematopoiesis; D006412:Hematopoietic Stem Cells / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D018124:Receptors, Tumor Necrosis Factor / Q000502:physiology*; D047888:Receptors, Tumor Necrosis Factor, Type I; D047889:Receptors, Tumor Necrosis Factor, Type II
chemical_list: D015703:Antigens, CD; D018124:Receptors, Tumor Necrosis Factor; D047888:Receptors, Tumor Necrosis Factor, Type I; D047889:Receptors, Tumor Necrosis Factor, Type II