title: Human bone marrow-derived mesenchymal stem cells display enhanced clonogenicity but impaired differentiation with hypoxic preconditioning.
abstract: Stem cells are promising candidate cells for regenerative applications because they possess high proliferative capacity and the potential to differentiate into other cell types. Mesenchymal stem cells (MSCs) are easily sourced but do not retain their proliferative and multilineage differentiative capabilities after prolonged ex vivo propagation. We investigated the use of hypoxia as a preconditioning agent and in differentiating cultures to enhance MSC function. Culture in 5% ambient O(2) consistently enhanced clonogenic potential of primary MSCs from all donors tested. We determined that enhanced clonogenicity was attributable to increased proliferation, increased vascular endothelial growth factor secretion, and increased matrix turnover. Hypoxia did not impact the incidence of cell death. Application of hypoxia to osteogenic cultures resulted in enhanced total mineral deposition, although this effect was detected only in MSCs preconditioned in normoxic conditions. Osteogenesis-associated genes were upregulated in hypoxia, and alkaline phosphatase activity was enhanced. Adipogenic differentiation was inhibited by exposure to hypoxia during differentiation. Chondrogenesis in three-dimensional pellet cultures was inhibited by preconditioning with hypoxia. However, in cultures expanded under normoxia, hypoxia applied during subsequent pellet culture enhanced chondrogenesis. Whereas hypoxic preconditioning appears to be an excellent way to expand a highly clonogenic progenitor pool, our findings suggest that it may blunt the differentiation potential of MSCs, compromising their utility for regenerative tissue engineering. Exposure to hypoxia during differentiation (post-normoxic expansion), however, appears to result in a greater quantity of functional osteoblasts and chondrocytes and ultimately a larger quantity of high-quality differentiated tissue.
authors.affiliation: Cartilage Biology and Orthopaedics Branch, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Department of Health and Human Services, Bethesda, Maryland, USA; Center for Cellular and Molecular Engineering, Department of Orthopaedic Surgery, McGowan Institute for Regenerative Medicine, and Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.
authors.forename: Lisa B
authors.initials: LB
authors.lastname: Boyette
authors.forename: Olivia A
authors.initials: OA
authors.lastname: Creasey
authors.forename: Lynda
authors.initials: L
authors.lastname: Guzik
authors.forename: Thomas
authors.initials: T
authors.lastname: Lozito
authors.forename: Rocky S
authors.initials: RS
authors.lastname: Tuan
mesh_terms: D017667:Adipocytes / Q000166:cytology*; D016923:Cell Death / Q000502:physiology; D002454:Cell Differentiation / Q000502:physiology; D049109:Cell Proliferation; D002478:Cells, Cultured; D019902:Chondrocytes / Q000166:cytology*; D002999:Clone Cells / Q000166:cytology; D016207:Cytokines / Q000378:metabolism; D005347:Fibroblasts / Q000166:cytology; D006801:Humans; D000860:Hypoxia / Q000473:pathology* / Q000503:physiopathology; D016130:Immunophenotyping; D019194:Ischemic Preconditioning / Q000379:methods*; D020782:Matrix Metalloproteinases / Q000378:metabolism; D059630:Mesenchymal Stem Cells / Q000166:cytology* / Q000378:metabolism; D010011:Osteocytes / Q000166:cytology*; D010100:Oxygen / Q000494:pharmacology
chemical_list: D016207:Cytokines; D020782:Matrix Metalloproteinases; D010100:Oxygen
keywords: Adipogenesis; Chondrogenesis; Colony-forming units assay; Hypoxia; Mesenchymal stem cells; Osteogenesis