title: Autocrine transforming growth factor beta 1 blocks colony formation and progenitor cell generation by hemopoietic stem cells stimulated with steel factor.
abstract: The ability of Steel Factor (SF) to stimulate colony formation and progenitor cell generation by hemopoietic stem cells (HSCs) in vitro in the absence of interleukin 3 (IL-3) was investigated. IL-3 was required for HSC proliferation, and no or restricted proliferation occurred in the presence of SF, IL-6, IL-11, or IL-12 as single factors or in combination. Neutralizing concentrations of anti-transforming growth factor (TGF)-beta 1 antibodies enhanced progenitor cell generation 2-3-fold in the presence of IL-3, but 75 to over 300-fold when cultures contained at least SF in the absence of IL-3. Exogenous TGF-beta 1 fully abrogated the antibody effects. In the presence of antibodies to TGF-beta 1, SF alone stimulated the delayed formation of small blast cell colonies and SF synergized with IL-6, IL-11, or IL-12 to greatly hasten colony formation, enhance colony number and size, and increase colony forming unit-culture (CFU-C) output from suspension cultures of enriched HSC populations. Secondary CFU-C colonies were significantly larger when IL-3 was absent during the suspension culture phase. Single cell and limiting dilution analysis using a homogenous colony forming unit-spleen (CFU-S) day-12 population and an 800-fold enriched long-term repopulating HSC fraction, respectively, indicated that TGF-beta 1 was an autocrine product of these HSC subsets. Addition of nucleosides, insulin, extra glucose, or serum could not replace the effects of the anti-TGF-beta 1 antibody. While these data offer one possible explanation for reports on the inability of SF to stimulate HSC proliferation, they present the basis for a novel model of the regulation of HSC activation wherein: 1) close-range interactions of HSCs with mesenchymal stromal cells do not exclusively determine maintenance of HSC quiescence; 2) competence acquisition by dormant HSCs may involve the down-regulation or inactivation of autocrine TGF-beta 1; and 3) SF may act as a primary growth factor rather than exclusively as a synergistic cytokine.
authors.affiliation: Institute of Hematology, Erasmus University, Rotterdam, The Netherlands.
authors.forename: R E
authors.initials: RE
authors.lastname: Ploemacher
authors.forename: P L
authors.initials: PL
authors.lastname: van Soest
authors.forename: A
authors.initials: A
authors.lastname: Boudewijn
mesh_terms: D000818:Animals; D016466:CHO Cells / Q000378:metabolism; D002455:Cell Division / Q000187:drug effects; D003114:Colony-Forming Units Assay; D006224:Cricetinae; D016895:Culture Media, Serum-Free / Q000494:pharmacology; D004921:Erythropoietin / Q000494:pharmacology; D016298:Hematopoietic Cell Growth Factors / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D006412:Hematopoietic Stem Cells / Q000187:drug effects*; D006801:Humans; D007136:Immunoglobulins / Q000276:immunology; D007378:Interleukins / Q000494:pharmacology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008808:Mice, Inbred CBA; D011994:Recombinant Proteins / Q000378:metabolism / Q000494:pharmacology; D019089:Stem Cell Factor; D016212:Transforming Growth Factor beta / Q000276:immunology / Q000378:metabolism / Q000494:pharmacology*
chemical_list: D016895:Culture Media, Serum-Free; D016298:Hematopoietic Cell Growth Factors; C016512:IgY; D007136:Immunoglobulins; D007378:Interleukins; D011994:Recombinant Proteins; D019089:Stem Cell Factor; D016212:Transforming Growth Factor beta; D004921:Erythropoietin