title: Ex vivo targeting of p21Cip1/Waf1 permits relative expansion of human hematopoietic stem cells.
abstract: Relative quiescence is a defining characteristic of hematopoietic stem cells. Reasoning that inhibitory tone dominates control of stem cell cycling, we previously showed that mice engineered to be deficient in the cyclin-dependent kinase inhibitor, p21Cip1/Waf1 (p21), have an increased stem cell pool under homeostatic conditions. Since p21 was necessary to maintain stem cell quiescence and its absence sufficient to permit increased murine stem cell cycling, we tested whether reduction of p21 alone in human adult-derived stem cells could affect stem cell proliferation. We demonstrate here that interrupting p21 expression ex vivo resulted in expanded stem cell number and in vivo stem cell function compared with control, manipulated cells. Further, we demonstrate full multilineage reconstitution capability in cells where p21 expression was knocked down. Therefore, lifting the brake on cell proliferation by altering cell cycle checkpoints provides an alternative paradigm for increasing hematopoietic stem cell numbers. This approach may be useful for relative ex vivo human stem cell expansion.
authors.affiliation: Center for Regenerative Medicine and Technology, AIDS Research Center and Cancer Center, Massachusetts General Hospital, Harvard Medical School, Boston, USA.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Stier
authors.forename: Tao
authors.initials: T
authors.lastname: Cheng
authors.forename: Randolf
authors.initials: R
authors.lastname: Forkert
authors.forename: Christoph
authors.initials: C
authors.lastname: Lutz
authors.forename: David M
authors.initials: DM
authors.lastname: Dombkowski
authors.forename: Jie Lin
authors.initials: JL
authors.lastname: Zhang
authors.forename: David T
authors.initials: DT
authors.lastname: Scadden
mesh_terms: D036541:ADP-ribosyl Cyclase / Q000378:metabolism; D051997:ADP-ribosyl Cyclase 1; D000818:Animals; D015703:Antigens, CD / Q000378:metabolism; D018952:Antigens, CD34 / Q000378:metabolism; D002478:Cells, Cultured; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000037:antagonists & inhibitors* / Q000235:genetics; D016373:DNA, Antisense / Q000235:genetics / Q000494:pharmacology; D005312:Fetal Blood / Q000166:cytology; D005434:Flow Cytometry; D005822:Genetic Vectors / Q000235:genetics; D006412:Hematopoietic Stem Cells / Q000166:cytology* / Q000187:drug effects / Q000502:physiology; D006801:Humans; D016086:Lentivirus / Q000235:genetics; D008562:Membrane Glycoproteins; D051379:Mice; D016688:Mice, Inbred NOD; D016513:Mice, SCID; D016376:Oligonucleotides, Antisense / Q000235:genetics / Q000494:pharmacology; D014161:Transduction, Genetic
chemical_list: D015703:Antigens, CD; D018952:Antigens, CD34; C493956:CDKN1A protein, human; C493957:Cdkn1a protein, mouse; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D016373:DNA, Antisense; D008562:Membrane Glycoproteins; D016376:Oligonucleotides, Antisense; D036541:ADP-ribosyl Cyclase; C498154:CD38 protein, human; C498155:Cd38 protein, mouse; D051997:ADP-ribosyl Cyclase 1