title: Chromatin-modifying agents permit human hematopoietic stem cells to undergo multiple cell divisions while retaining their repopulating potential.
abstract: Human hematopoietic stem cells (HSCs) exposed to cytokines in vitro rapidly divide and lose their characteristic functional properties presumably due to the alteration of a genetic program that determines the properties of an HSC. We have attempted to reverse the silencing of this HSC genetic program by the sequential treatment of human cord blood CD34(+) cells with the chromatin-modifying agents, 5-aza-2'-deoxycytidine (5azaD) and trichostatin A (TSA). We determined that all CD34(+)CD90(+) cells treated with 5azaD/TSA and cytokines after 9 days of incubation divide, but to a lesser degree than cells exposed to only cytokines. When CD34(+)CD90(+) cells that have undergone extensive number of cell divisions (5-10) in the presence of cytokines alone were transplanted into immunodeficient mice, donor cell chimerism was not detectable. By contrast, 5azaD/TSA-treated cells that have undergone similar numbers of cell divisions retained their marrow repopulating potential. The expression of several genes and their products previously implicated in HSC self-renewal were up-regulated in the cells treated with 5azaD/TSA as compared to cells exposed to cytokines alone. These data indicate that HSC treated with chromatin-modifying agents are capable of undergoing repeated cell divisions in vitro while retaining their marrow-repopulating potential.
authors.affiliation: Section of Hematology/Oncology, Department of Medicine, University of Illinois at Chicago, 909 S. Wolcott Avenue, Chicago, IL 60612, USA.
authors.forename: Hiroto
authors.initials: H
authors.lastname: Araki
authors.forename: Kazumi
authors.initials: K
authors.lastname: Yoshinaga
authors.forename: Piernicola
authors.initials: P
authors.lastname: Boccuni
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhao
authors.forename: Ronald
authors.initials: R
authors.lastname: Hoffman
authors.forename: Nadim
authors.initials: N
authors.lastname: Mahmud
mesh_terms: D000818:Animals; D018952:Antigens, CD34; D001374:Azacitidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D002455:Cell Division / Q000187:drug effects* / Q000235:genetics; D002478:Cells, Cultured; D002843:Chromatin / Q000235:genetics / Q000378:metabolism; D016207:Cytokines / Q000494:pharmacology; D000077209:Decitabine; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D018380:Hematopoietic Stem Cell Transplantation; D006412:Hematopoietic Stem Cells / Q000166:cytology* / Q000378:metabolism; D006801:Humans; D006877:Hydroxamic Acids / Q000494:pharmacology*; D051379:Mice; D016688:Mice, Inbred NOD; D016513:Mice, SCID; D018800:Thy-1 Antigens; D013997:Time Factors; D014183:Transplantation, Heterologous; D015854:Up-Regulation / Q000187:drug effects
chemical_list: D018952:Antigens, CD34; D002843:Chromatin; D016207:Cytokines; D004791:Enzyme Inhibitors; D006877:Hydroxamic Acids; D018800:Thy-1 Antigens; C012589:trichostatin A; D000077209:Decitabine; D001374:Azacitidine