title: Cell-free repair of small cartilage defects in the Goettinger minipig: the effects of BMP-7 continuously released by poly(lactic-co-glycolid acid) microspheres.
abstract: OBJECTIVE
  Cartilage repair of full-thickness chondral defects in the knees of Goettinger minipigs was assessed after treatment with cell-free collagen type-I gel with or without additional BMP-7 loaded poly(lactic-co-glycolid acid) microspheres.
  
  
  METHODS
  Two full-thickness chondral defects were created in the trochlear groove of one hind leg knee in six Goettinger minipigs. Six defects were treated with a cell-free collagen type-I gel plug of 10 mm, the corresponding six defects were treated with a cell-free collagen type-I plug with poly(lactic-co-glycolid acid) microspheres loaded with recombinant BMP-7 (100 ng/ml gel). After 1 year, the animals were sacrificed. Immediately after recovery, non-destructive biomechanical testing was performed. The repair tissue quality was evaluated by immunohistochemistry and the O'Driscoll score was calculated.
  
  
  RESULTS
  After 1 year, a robust cellular migration into the cell-free collagen gel plugs occurred and a hyaline-like repair tissue was found. Collagen type-II production and cellular organisation were higher in the BMP-7 microsphere group. The determination of the E-modulus, creep and relaxation revealed that mechanical properties of the BMP-7 microsphere group in summary were closer to control hyaline cartilage.
  
  
  CONCLUSIONS
  While all specimens revealed a homogeneous cellular distribution, ECM production, cellular organisation and mechanical properties were enhanced by continuous BMP-7 release.
authors.affiliation: 1Department of Orthopaedic and Trauma Surgery, Aachen University Hospital, Aachen, Germany.
authors.forename: Karsten
authors.initials: K
authors.lastname: Gavenis
authors.forename: Nicole
authors.initials: N
authors.lastname: Heussen
authors.forename: Martijn
authors.initials: M
authors.lastname: Hofman
authors.forename: Stefan
authors.initials: S
authors.lastname: Andereya
authors.forename: Ulrich
authors.initials: U
authors.lastname: Schneider
authors.forename: Bernhard
authors.initials: B
authors.lastname: Schmidt-Rohlfing
mesh_terms: D000818:Animals; D055419:Bone Morphogenetic Protein 7 / Q000008:administration & dosage*; D002358:Cartilage, Articular / Q000254:growth & development*; D002474:Cell-Free System; D019344:Lactic Acid / Q000008:administration & dosage* / Q000737:chemistry; D008297:Male; D008863:Microspheres; D011100:Polyglycolic Acid / Q000008:administration & dosage* / Q000737:chemistry; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011994:Recombinant Proteins / Q000008:administration & dosage; D013552:Swine; D013556:Swine, Miniature
chemical_list: D055419:Bone Morphogenetic Protein 7; D011994:Recombinant Proteins; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011100:Polyglycolic Acid; D019344:Lactic Acid
keywords: BMP-7 loaded PLGA microspheres; Collagen type-I gel; Goettinger minipig; cartilage tissue engineering; cell-free implant