title: An ovine in vitro model for chondrocyte-based scaffold-assisted cartilage grafts.
abstract: BACKGROUND
  Scaffold-assisted autologous chondrocyte implantation is an effective clinical procedure for cartilage repair. From the regulatory point of view, the ovine model is one of the suggested large animal models for pre-clinical studies. The aim of our study was to evaluate the in vitro re-differentiation capacity of expanded ovine chondrocytes in biomechanically characterized polyglycolic acid (PGA)/fibrin biomaterials for scaffold-assisted cartilage repair.
  
  
  METHODS
  Ovine chondrocytes harvested from adult articular cartilage were expanded in monolayer and re-assembled three-dimensionally in PGA-fibrin scaffolds. De- and re-differentiation of ovine chondrocytes in PGA-fibrin scaffolds was assessed by histological and immuno-histochemical staining as well as by real-time gene expression analysis of typical cartilage marker molecules and the matrix-remodelling enzymes matrix metalloproteinases (MMP) -1, -2 and -13 as well as their inhibitors. PGA scaffolds characteristics including degradation and stiffness were analysed by electron microscopy and biomechanical testing.
  
  
  RESULTS
  Histological, immuno-histochemical and gene expression analysis showed that dedifferentiated chondrocytes re-differentiate in PGA-fibrin scaffolds and form a cartilaginous matrix. Re-differentiation was accompanied by the induction of type II collagen and aggrecan, while MMP expression decreased in prolonged tissue culture. Electron microscopy and biomechanical tests revealed that the non-woven PGA scaffold shows a textile structure with high tensile strength of 3.6 N/mm2 and a stiffness of up to 0.44 N/mm2, when combined with gel-like fibrin.
  
  
  CONCLUSIONS
  These data suggest that PGA-fibrin is suited as a mechanically stable support structure for scaffold-assisted chondrocyte grafts, initiating chondrogenic re-differentiation of expanded chondrocytes.
authors.affiliation: TransTissue Technologies GmbH, Berlin, Germany.
authors.forename: Michaela
authors.initials: M
authors.lastname: Endres
authors.forename: Katja
authors.initials: K
authors.lastname: Neumann
authors.forename: Bei
authors.initials: B
authors.lastname: Zhou
authors.forename: Undine
authors.initials: U
authors.lastname: Freymann
authors.forename: David
authors.initials: D
authors.lastname: Pretzel
authors.forename: Marcus
authors.initials: M
authors.lastname: Stoffel
authors.forename: Raimund W
authors.initials: RW
authors.lastname: Kinne
authors.forename: Christian
authors.initials: C
authors.lastname: Kaps
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena / Q000502:physiology; D002358:Cartilage, Articular / Q000166:cytology* / Q000502:physiology / Q000601:surgery*; D018929:Cell Culture Techniques / Q000379:methods; D002454:Cell Differentiation / Q000502:physiology; D002478:Cells, Cultured; D019902:Chondrocytes / Q000502:physiology; D023421:Models, Animal; D012756:Sheep; D054457:Tissue Scaffolds