title: Interleukin-6 deficiency affects bone marrow stromal precursors, resulting in defective hematopoietic support.
abstract: Interleukin-6 (IL-6) is a critical factor in the regulation of stromal function and hematopoiesis. In vivo bromodeoxyuridine incorporation analysis indicates that the percentage of Lin(-)Sca-1(+) hematopoietic progenitors undergoing DNA synthesis is diminished in IL-6-deficient (IL-6(-/-)) bone marrow (BM) compared with wild-type BM. Reduced proliferation of IL-6(-/-) BM progenitors is also observed in IL-6(-/-) long-term BM cultures, which show defective hematopoietic support as measured by production of total cells, granulocyte macrophage-colony-forming units (CFU-GMs), and erythroid burst-forming units (BFU-Es). Seeding experiments of wild-type and IL-6(-/-) BM cells on irradiated wild-type or IL-6-deficient stroma indicate that the hematopoietic defect can be attributed to the stromal and not to the hematopoietic component. In IL-6(-/-) BM, stromal mesenchymal precursors, fibroblast CFUs (CFU-Fs), and stroma-initiating cells (SICs) are reduced to almost 50% of the wild-type BM value. Moreover, IL-6(-/-) stromata show increased CD34 and CD49e expression and reduced expression of the membrane antigens vascular cell adhesion molecule-1 (VCAM-1), Sca-1, CD49f, and Thy1. These data strongly suggest that IL-6 is an in vivo growth factor for mesenchymal precursors, which are in part implicated in the reduced longevity of the long-term repopulating stem cell compartment of IL-6(-/-) mice.
authors.affiliation: Department of Immunology and Oncology, Centro Nacional de Biotecnología/CSIC, UAM Campus de Cantoblanco, E-28049 Madrid, Spain.
authors.forename: María del Carmen
authors.initials: Mdel C
authors.lastname: Rodríguez
authors.forename: Antonio
authors.initials: A
authors.lastname: Bernad
authors.forename: Miguel
authors.initials: M
authors.lastname: Aracil
mesh_terms: D000818:Animals; D001854:Bone Marrow Cells / Q000166:cytology; D002455:Cell Division; D002478:Cells, Cultured; D006410:Hematopoiesis; D006412:Hematopoietic Stem Cells / Q000166:cytology; D016130:Immunophenotyping; D015850:Interleukin-6 / Q000172:deficiency* / Q000502:physiology*; D059630:Mesenchymal Stem Cells / Q000166:cytology / Q000502:physiology*; D051379:Mice; D018345:Mice, Knockout; D017154:Stromal Cells / Q000166:cytology* / Q000502:physiology
chemical_list: D015850:Interleukin-6