title: Hypoxia increases Sca-1/CD44 co-expression in murine mesenchymal stem cells and enhances their adipogenic differentiation potential.
abstract: Mesenchymal stem cells (MSCs) are usually cultured under normoxic conditions (21% oxygen). However, in vivo, the physiological "niches" for MSCs have a much lower oxygen tension. Because of their plasticity, stem cells are particularly sensitive to their environments, and oxygen tension is one developmentally important stimulus in stem cell biology and plays a role in the intricate balance between cellular proliferation and commitment towards differentiation. Therefore, we investigated here the effect of hypoxia (2% oxygen) on murine adipose tissue (AT) MSC proliferation and adipogenic differentiation. AT cells were obtained from the omental fat and AT-MSCs were selected for their ability to attach to the plastic dishes, and were grown under normoxic and hypoxic conditions. Prior exposure of MSCs to hypoxia led to a significant reduction of ex vivo expansion time, with significantly increased numbers of Sca-1(+) as well as Sca-1(+)/CD44(+)double-positive cells. Under low oxygen culture conditions, the AT-MSC number markedly increased and their adipogenic differentiation potential was reduced. Notably, the hypoxia-mediated inhibition of adipogenic differentiation was reversible: AT-MSCs pre-exposed to hypoxia when switched to normoxic conditions exhibited significantly higher adipogenic differentiation capacity compared to their pre-exposed normoxic-cultured counterparts. Accordingly, the expression of adipocyte-specific genes, peroxisome proliferator activated receptor gamma (Ppargamma), lipoprotein lipase (Lpl) and fatty acid binding protein 4 (Fabp4) were significantly enhanced in hypoxia pre-exposed AT-MSCs. In conclusion, pre-culturing MSCs under hypoxic culture conditions may represent a strategy to enhance MSC production, enrichment and adipogenic differentiation.
authors.affiliation: Centre for Diabetes, Blizard Institute of Cell and Molecular Science, Barts & the London School of Medicine & Dentistry, Queen Mary University of London, London, UK. m.g.valorani@qmul.ac.uk
authors.forename: M G
authors.initials: MG
authors.lastname: Valorani
authors.forename: A
authors.initials: A
authors.lastname: Germani
authors.forename: W R
authors.initials: WR
authors.lastname: Otto
authors.forename: L
authors.initials: L
authors.lastname: Harper
authors.forename: A
authors.initials: A
authors.lastname: Biddle
authors.forename: C P
authors.initials: CP
authors.lastname: Khoo
authors.forename: W R
authors.initials: WR
authors.lastname: Lin
authors.forename: M I
authors.initials: MI
authors.lastname: Hawa
authors.forename: P
authors.initials: P
authors.lastname: Tropel
authors.forename: M P
authors.initials: MP
authors.lastname: Patrizi
authors.forename: P
authors.initials: P
authors.lastname: Pozzilli
authors.forename: M R
authors.initials: MR
authors.lastname: Alison
mesh_terms: D050156:Adipogenesis; D000273:Adipose Tissue / Q000166:cytology; D000818:Animals; D000067696:Ataxin-1; D000067528:Ataxins; D015415:Biomarkers / Q000378:metabolism; D002453:Cell Cycle; D015687:Cell Hypoxia; D049109:Cell Proliferation; D002470:Cell Survival; D002478:Cells, Cultured; D018960:Hyaluronan Receptors / Q000378:metabolism*; D008297:Male; D059630:Mesenchymal Stem Cells / Q000166:cytology* / Q000378:metabolism*; D051379:Mice; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism*
chemical_list: D000067696:Ataxin-1; D000067528:Ataxins; C000593750:Atxn1 protein, mouse; D015415:Biomarkers; D018960:Hyaluronan Receptors; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins