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

• Published in: Journal of biomaterials applications 2014-03, Vol.28 (7), p.1008-1015
• Main Authors: Gavenis, Karsten, Heussen, Nicole, Hofman, Martijn, Andereya, Stefan, Schneider, Ulrich, Schmidt-Rohlfing, Bernhard
• Format: Article
• Language: English
• Subjects: Animals; Bone Morphogenetic Protein 7 - administration & dosage; Cartilage, Articular - growth & development; Cell-Free System; Indexing in process; Lactic Acid - administration & dosage; Lactic Acid - chemistry; Male; Microspheres; Polyglycolic Acid - administration & dosage; Polyglycolic Acid - chemistry; Recombinant Proteins - administration & dosage; Swine; Swine, Miniature
• ISSN: 0885-3282; 1530-8022
• DOI: 10.1177/0885328213491440

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.