title: Hypoxia promotes nucleus pulposus phenotype in 3D scaffolds in vitro and in vivo: laboratory investigation.
abstract: OBJECTIVE
  The role of oxygen in disc metabolism remains a matter of debate. Whether the effect of hypoxic priming on the nucleus pulposus phenotype can be maintained in vivo is not clear. The goal of the present study was to test the hypothesis that priming in a low oxygen tension in vitro could promote a nucleus pulposus phenotype in vivo.
  
  
  METHODS
  Bovine nucleus pulposus cells were seeded in 3D scaffolds and subjected to varying oxygen tensions (2% and 20%) for 3 weeks. The constructs were then implanted subcutaneously for 8 weeks. Changes in the extracellular matrix were evaluated using quantitative real-time reverse transcriptase polymerase chain reaction, glycosaminoglycan (GAG) assay, DNA assay, collagen quantification, and histological and immunohistological analyses.
  
  
  RESULTS
  Hypoxia resulted in greater production of sulfated glycosaminoglycan and higher levels of gene expression for collagen Type II, aggrecan, and SOX-9. Furthermore, after hypoxic priming, the subcutaneously implanted constructs maintained the nucleus pulposus phenotype, which was indicated by a significantly higher amount of glycosaminoglycan and collagen Type II.
  
  
  CONCLUSIONS
  Hypoxia enhanced the nucleus pulposus phenotype under experimental conditions both in vitro and in vivo. When used in combination with appropriate scaffold material, nucleus pulposus cells could be regenerated for tissue-engineering applications.
authors.affiliation: Departments of 1 Orthopedics.
authors.forename: Ganjun
authors.initials: G
authors.lastname: Feng
authors.forename: Li
authors.initials: L
authors.lastname: Li
authors.forename: Ying
authors.initials: Y
authors.lastname: Hong
authors.forename: Hao
authors.initials: H
authors.lastname: Liu
authors.forename: Yueming
authors.initials: Y
authors.lastname: Song
authors.forename: Fuxing
authors.initials: F
authors.lastname: Pei
authors.forename: Peter X
authors.initials: PX
authors.lastname: Ma
authors.forename: Quan
authors.initials: Q
authors.lastname: Gong
authors.forename: Melanie J
authors.initials: MJ
authors.lastname: Gupte
mesh_terms: D053674:Aggrecans / Q000378:metabolism; D000818:Animals; D002417:Cattle; D015687:Cell Hypoxia; D002478:Cells, Cultured; D024043:Collagen Type II / Q000378:metabolism; D005109:Extracellular Matrix / Q000378:metabolism; D006025:Glycosaminoglycans / Q000378:metabolism; D007150:Immunohistochemistry; D007403:Intervertebral Disc / Q000166:cytology* / Q000378:metabolism*; D010641:Phenotype; D012313:RNA / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D023822:Tissue Engineering / Q000379:methods; D054457:Tissue Scaffolds
chemical_list: D053674:Aggrecans; D024043:Collagen Type II; D006025:Glycosaminoglycans; D012313:RNA
keywords: ECM = extracellular matrix; GAG = glycosaminoglycan; PBS = phosphate-buffered saline; hypoxia; intervertebral disc; nucleus pulposus; scaffold; subcutaneous implantation; tissue engineering