title: Expansion of human SCID-repopulating cells under hypoxic conditions.
abstract: It has been proposed that bone marrow (BM) hematopoietic stem and progenitor cells are distributed along an oxygen (O2) gradient, where stem cells reside in the most hypoxic areas and proliferating progenitors are found in O2-rich areas. However, the effects of hypoxia on human hematopoietic stem cells (HSCs) have not been characterized. Our objective was to evaluate the functional and molecular responses of human BM progenitors and stem cells to hypoxic conditions. BM lineage-negative (Lin-) CD34+CD38- cells were cultured in serum-free medium under 1.5% O2 (hypoxia) or 20% O2 (normoxia) for 4 days. Using limiting dilution analysis, we demonstrate that the absolute number of SCID-repopulating cells (SRCs) increased by 5.8-fold in hypoxic cultures compared with normoxia, and by 4.2-fold compared with freshly isolated Lin-CD34+CD38- cells. The observed increase in BM-repopulating activity was associated with a preferential expansion of Lin-CD34+CD38- cells. We also demonstrate that, in response to hypoxia, hypoxia-inducible factor-1alpha protein was stabilized, surface expression of angiogenic receptors was upregulated, and VEGF secretion increased in BM Lin-CD34+ cultures. The use of low O2 levels to enhance the survival and/or self-renewal of human BM HSCs in vitro represents an important advance and could have valuable clinical implications.
authors.affiliation: Division of Hematology-Oncology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104-6160, USA. gdanet@mail.med.upenn.edu
authors.forename: Guénahel H
authors.initials: GH
authors.lastname: Danet
authors.forename: Yi
authors.initials: Y
authors.lastname: Pan
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Luongo
authors.forename: Dominique A
authors.initials: DA
authors.lastname: Bonnet
authors.forename: M Celeste
authors.initials: MC
authors.lastname: Simon
mesh_terms: D036541:ADP-ribosyl Cyclase / Q000032:analysis; D051997:ADP-ribosyl Cyclase 1; D000818:Animals; D015703:Antigens, CD / Q000032:analysis; D018952:Antigens, CD34 / Q000032:analysis; D001854:Bone Marrow Cells / Q000502:physiology*; D002453:Cell Cycle; D002455:Cell Division; D015687:Cell Hypoxia; D002478:Cells, Cultured; D006412:Hematopoietic Stem Cells / Q000502:physiology*; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D008562:Membrane Glycoproteins; D051379:Mice; D016688:Mice, Inbred NOD; D016511:Severe Combined Immunodeficiency / Q000276:immunology / Q000473:pathology*; D014157:Transcription Factors / Q000378:metabolism
chemical_list: D015703:Antigens, CD; D018952:Antigens, CD34; C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D008562:Membrane Glycoproteins; D014157:Transcription Factors; D036541:ADP-ribosyl Cyclase; C498154:CD38 protein, human; C498155:Cd38 protein, mouse; D051997:ADP-ribosyl Cyclase 1