title: Engineering of hyaline cartilage with a calcified zone using bone marrow stromal cells.
abstract: OBJECTIVE
  In healthy joints, a zone of calcified cartilage (ZCC) provides the mechanical integration between articular cartilage and subchondral bone. Recapitulation of this architectural feature should serve to resist the constant shear force from the movement of the joint and prevent the delamination of tissue-engineered cartilage. Previous approaches to create the ZCC at the cartilage-substrate interface have relied on strategic use of exogenous scaffolds and adhesives, which are susceptible to failure by degradation and wear. In contrast, we report a successful scaffold-free engineering of ZCC to integrate tissue-engineered cartilage and a porous biodegradable bone substitute, using sheep bone marrow stromal cells (BMSCs) as the cell source for both cartilaginous zones.
  
  
  METHODS
  BMSCs were predifferentiated to chondrocytes, harvested and then grown on a porous calcium polyphosphate substrate in the presence of triiodothyronine (T3). T3 was withdrawn, and additional predifferentiated chondrocytes were placed on top of the construct and grown for 21 days.
  
  
  RESULTS
  This protocol yielded two distinct zones: hyaline cartilage that accumulated proteoglycans and collagen type II, and calcified cartilage adjacent to the substrate that additionally accumulated mineral and collagen type X. Constructs with the calcified interface had comparable compressive strength to native sheep osteochondral tissue and higher interfacial shear strength compared to control without a calcified zone.
  
  
  CONCLUSIONS
  This protocol improves on the existing scaffold-free approaches to cartilage tissue engineering by incorporating a calcified zone. Since this protocol employs no xenogeneic material, it will be appropriate for use in preclinical large-animal studies.
authors.affiliation: Institute of Biomaterials and Biomedical Engineering, University of Toronto, 164 College St., Toronto, Ontario M5S 3G9, Canada.
authors.forename: W D
authors.initials: WD
authors.lastname: Lee
authors.affiliation: Ontario Veterinary College, University of Guelph, 50 McGilvray Street, Guelph, Ontario N1G 2W1, Canada.
authors.forename: M B
authors.initials: MB
authors.lastname: Hurtig
authors.affiliation: Institute of Biomaterials and Biomedical Engineering, University of Toronto, 164 College St., Toronto, Ontario M5S 3G9, Canada; Faculty of Dentistry, University of Toronto, 124 Edward St., Toronto, Ontario M5G 1G6, Canada.
authors.forename: R M
authors.initials: RM
authors.lastname: Pilliar
authors.affiliation: Institute of Biomaterials and Biomedical Engineering, University of Toronto, 164 College St., Toronto, Ontario M5S 3G9, Canada; Sprott Centre for Stem Cell Research, Ottawa Hospital Research Institute, University of Ottawa, 501 Smyth Road, Ottawa, ON K1H 8L6, Canada; Department of Cellular & Molecular Medicine, University of Ottawa, 501 Smyth Road, Box 511, Ottawa, Ontario K1H 8L6, Canada; Department of Biochemistry, Microbiology and Immunology, University of Ottawa, 501 Smyth Road, Box 511, Ottawa, Ontario K1H 8L6, Canada. Electronic address: wstanford@ohri.ca.
authors.forename: W L
authors.initials: WL
authors.lastname: Stanford
authors.affiliation: Institute of Biomaterials and Biomedical Engineering, University of Toronto, 164 College St., Toronto, Ontario M5S 3G9, Canada; Department of Pathology and Laboratory Medicine, Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, University of Toronto, 600 University Ave., Toronto, Ontario M5G 1X5, Canada. Electronic address: rkandel@mtsinai.on.ca.
authors.forename: R A
authors.initials: RA
authors.lastname: Kandel
mesh_terms: D000818:Animals; D001854:Bone Marrow Cells / Q000166:cytology*; D002113:Calcification, Physiologic / Q000502:physiology*; D018929:Cell Culture Techniques / Q000379:methods; D002454:Cell Differentiation; D024043:Collagen Type II / Q000502:physiology; D024121:Collagen Type X / Q000502:physiology; D051457:Hyaline Cartilage / Q000502:physiology*; D011509:Proteoglycans / Q000502:physiology; D012756:Sheep; D017154:Stromal Cells / Q000166:cytology*; D023822:Tissue Engineering / Q000379:methods*; D014284:Triiodothyronine / Q000494:pharmacology
chemical_list: D024043:Collagen Type II; D024121:Collagen Type X; D011509:Proteoglycans; D014284:Triiodothyronine
keywords: Cartilage–bone interface; Mesenchymal stromal cells; Osteochondral constructs; Tissue engineering