title: Notochordal cell conditioned medium stimulates mesenchymal stem cell differentiation toward a young nucleus pulposus phenotype.
abstract: BACKGROUND
  Mesenchymal stem cells (MSCs) offer promise for intervertebral disc (IVD) repair and regeneration because they are easily isolated and expanded, and can differentiate into several mesenchymal tissues. Notochordal (NC) cells contribute to IVD development, incorporate into the nucleus pulposus (NP), and stimulate mature disc cells. However, there have been no studies investigating the effects of NC cells on adult stem cell differentiation. The premise of this study is that IVD regeneration is more similar to IVD development than to IVD maintenance, and we hypothesize that soluble factors from NC cells differentiate MSCs to a phenotype characteristic of nucleus pulposus (NP) cells during development. The eventual clinical goal would be to isolate or chemically/recombinantly produce the active agent to induce the therapeutic effects, and to use it as either an injectable therapy for early intervention on disc disease, or in developing appropriately pre-differentiated MSC cells in a tissue engineered NP construct.
  
  
  METHODS
  Human MSCs from bone marrow were expanded and pelleted to form high-density cultures. MSC pellets were exposed to either control medium (CM), chondrogenic medium (CM with dexamethasone and transforming growth factor, (TGF)-beta3) or notochordal cell conditioned medium (NCCM). NCCM was prepared from NC cells maintained in serum free medium for four days. After seven days culture, MSC pellets were analyzed for appearance, biochemical composition (glycosaminoglycans and DNA), and gene expression profile (sox-9, collagen types-II and III, laminin-beta1 and TIMP1(tissue inhibitor of metalloproteinases-1)).
  
  
  RESULTS
  Significantly higher glycosaminoglycan accumulation was seen in NCCM treated pellets than in CM or TGFbeta groups. With NCCM treatment, increased gene expression of collagen III, and a trend of increasing expression of laminin-beta1 and decreased expression of sox-9 and collagen II relative to the TGFbeta group was observed.
  
  
  CONCLUSIONS
  Together, results suggest NCCM stimulates mesenchymal stem cell differentiation toward a potentially NP-like phenotype with some characteristics of the developing IVD.
authors.affiliation: Cartilage Biology and Orthopaedics Branch, National Institute of Arthritis, Musculoskeletal and Skin Diseases, National Institutes of Health, Department of Health and Human Services, 50 South Drive, Bethesda, MD 20892, USA. ckorecki@gmail.com
authors.forename: Casey L
authors.initials: CL
authors.lastname: Korecki
authors.forename: Juan M
authors.initials: JM
authors.lastname: Taboas
authors.forename: Rocky S
authors.initials: RS
authors.lastname: Tuan
authors.forename: James C
authors.initials: JC
authors.lastname: Iatridis
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects*; D002478:Cells, Cultured; D019902:Chondrocytes / Q000378:metabolism; D024043:Collagen Type II / Q000378:metabolism; D024061:Collagen Type III / Q000378:metabolism; D017077:Culture Media, Conditioned / Q000494:pharmacology*; D003907:Dexamethasone / Q000494:pharmacology; D020869:Gene Expression Profiling; D006025:Glycosaminoglycans / Q000378:metabolism; D006801:Humans; D007403:Intervertebral Disc / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D055959:Intervertebral Disc Degeneration / Q000628:therapy; D007797:Laminin / Q000378:metabolism; D059630:Mesenchymal Stem Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D009672:Notochord / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D012038:Regeneration / Q000187:drug effects; D055758:SOX9 Transcription Factor / Q000378:metabolism; D013552:Swine; D019715:Tissue Inhibitor of Metalloproteinase-1 / Q000378:metabolism; D053782:Transforming Growth Factor beta3 / Q000494:pharmacology
chemical_list: D024043:Collagen Type II; D024061:Collagen Type III; D017077:Culture Media, Conditioned; D006025:Glycosaminoglycans; D007797:Laminin; D055758:SOX9 Transcription Factor; D019715:Tissue Inhibitor of Metalloproteinase-1; D053782:Transforming Growth Factor beta3; D003907:Dexamethasone