title: Co-culture induces mesenchymal stem cell differentiation and modulation of the degenerate human nucleus pulposus cell phenotype.
abstract: OBJECTIVE
  While mesenchymal stem cell (MSC)-based therapies for repair of the degenerate intervertebral disc (IVD) have been proposed, the interaction of MSCs with cells of the degenerate IVD has not been fully investigated. Therefore, it is unclear whether implanted MSCs would differentiate into nucleus pulposus (NP) cells and/or stimulate endogenous NP cells. Here, we investigate the differences in interaction between human MSCs and NP cells from both nondegenerate and degenerate discs during in vitro co-culture with direct cell-cell contact.
  
  
  METHODS
  Human bone marrow-derived MSCs (labeled with CFDA) were co-cultured with direct cell-cell contact in monolayer with NP cells obtained from nondegenerate or degenerate human NP tissue from lumbar IVDs at 50:50 ratios for 7 days. Differentiation of MSCs and changes of matrix-associated genes in NP cells were assessed by quantitative real-time PCR.
  
  
  RESULTS
  MSCs differentiated to an NP-like phenotype following direct co-culture with both nondegenerate and degenerate NP, as shown by a significant upregulation of SOX9, type VI collagen, aggrecan and versican gene expression together with a simultaneous upregulation of CDMP-1, TGF-β1, IGF-1 and CTGF. Direct co-culture of normal NP cells with MSCs had no effect on the phenotype of normal NP cells, while co-culture with degenerate NP cells resulted in enhanced matrix gene expression in degenerate NP cells, accompanied by increases in both TGF-β and CDMP-1 gene expression.
  
  
  CONCLUSIONS
  Importantly for MSC-based therapies for repair of the degenerate IVD, these data suggest that cellular interactions between MSCs and degenerate NP cells may both stimulate MSC differentiation to an NP-like phenotype and also stimulate the endogenous NP cell population to regain a nondegenerate phenotype and consequently enhance matrix synthesis for self-repair.
authors.affiliation: Regenerative Medicine, School of Biomedicine, Faculty of Medical & Human Sciences, The University of Manchester, Manchester, M13 9PT, UK.
authors.forename: Sandra
authors.initials: S
authors.lastname: Strassburg
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Richardson
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Freemont
authors.forename: Judith A
authors.initials: JA
authors.lastname: Hoyland
mesh_terms: D002450:Cell Communication; D002454:Cell Differentiation; D018920:Coculture Techniques; D016326:Extracellular Matrix Proteins / Q000235:genetics; D005786:Gene Expression Regulation; D006801:Humans; D007403:Intervertebral Disc / Q000166:cytology*; D059630:Mesenchymal Stem Cells / Q000166:cytology*; D010641:Phenotype; D044968:Regenerative Medicine / Q000379:methods
chemical_list: D016326:Extracellular Matrix Proteins