title: Hypoxia improves expansion potential of human cord blood-derived hematopoietic stem cells and marrow repopulation efficiency.
abstract: OBJECTIVE
  In bone marrow, hematopoietic stem cells (HSCs) reside in the most hypoxic endosteum niche, whereas the proliferating progenitors are located near the relatively oxygen-rich vascular region. High oxygen tension is potentially detrimental to HSCs. The objective of this investigation was to compare cellular, functional, and molecular responses of human umbilical cord blood (UCB)-derived hematopoietic stem and progenitor cells in culture under hypoxic and normoxic conditions.
  
  
  METHODS
  CD133-enriched UCB cells were cultured in growth factor containing serum-free and serum-supplemented medium under 5% O(2) (hypoxia) or 21% O(2) (normoxia) for 10 d. The phenotypes of expanded cells were analyzed by flow cytometry and the engraftability by SCID-repopulation assay. The expression of hypoxia-inducible factor (HIF)-1α and some of its target genes was analyzed by real-time RT-PCR.
  
  
  RESULTS
  In hypoxic culture, CD34(+) CD38(-) cells were expanded about 27-fold, which was significantly (P < 0.01) higher than that obtained in normoxic culture. Serum-free culture did not support the growth of cells in the presence of 21% O(2) . Myeloid colony-forming potential of cells was significantly (P < 0.05) increased in 5% O(2) compared with 21% O(2) culture. SCID-repopulation efficiency seems to be better preserved in the cells cultured under hypoxic conditions. Hypoxia significantly (P < 0.05) induced the expression of HIF-1α, vascular endothelial growth factor (VEGF), and ABCG2 genes and also upregulated CXCR4 receptor expression.
  
  
  CONCLUSIONS
  Low oxygen tension enhanced the proliferation of UCB-derived HSC/progenitor cells and maintenance of SCID-repopulating cells than normoxia. These expanded cells are expected to be beneficial in the patients who lack human leukocyte antigen (HLA)-matched donors.
authors.affiliation: Stem Cell Biology Laboratory, National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi, India.
authors.forename: Sushmita
authors.initials: S
authors.lastname: Roy
authors.forename: Manjul
authors.initials: M
authors.lastname: Tripathy
authors.forename: Nitin
authors.initials: N
authors.lastname: Mathur
authors.forename: Asish
authors.initials: A
authors.lastname: Jain
authors.forename: Asok
authors.initials: A
authors.lastname: Mukhopadhyay
mesh_terms: D000071916:AC133 Antigen; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters / Q000378:metabolism; D000818:Animals; D015703:Antigens, CD / Q000276:immunology; D017209:Apoptosis; D002455:Cell Division; D015687:Cell Hypoxia; D019070:Cell Lineage; D049109:Cell Proliferation; D003470:Culture Media; D005312:Fetal Blood / Q000166:cytology*; D005434:Flow Cytometry; D006023:Glycoproteins / Q000276:immunology; D006412:Hematopoietic Stem Cells / Q000166:cytology* / Q000276:immunology; D006801:Humans; D051379:Mice; D016513:Mice, SCID; D009363:Neoplasm Proteins / Q000378:metabolism; D010455:Peptides / Q000276:immunology; D060888:Real-Time Polymerase Chain Reaction; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism
chemical_list: C116614:ABCG2 protein, human; D000071916:AC133 Antigen; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters; D015703:Antigens, CD; D003470:Culture Media; D006023:Glycoproteins; D009363:Neoplasm Proteins; C000606023:PROM1 protein, human; D010455:Peptides; C000606024:Prom1 protein, mouse; D042461:Vascular Endothelial Growth Factor A