title: Biphasic scaffolds for repair of deep osteochondral defects in a sheep model.
abstract: BACKGROUND
  To oppose the disadvantages of autologous osteochondral transplantation in the treatment of deep osteochondral defects such as donor site morbidity, size limitation, and insufficient chondral integration, we developed two biphasic scaffolds of either hydroxylapatite/collagen (scaffold A) or allogenous sterilized bone/collagen (scaffold B) and tested their integration in a sheep model.
  
  
  METHODS
  We collected chondral biopsies from 12 sheep for the isolation of chondroblasts and cultured them for 4 wk. We created defects at the femoral condyle and implanted either scaffold A or B with chondrocytes or cell free. After 6 wk, animals were euthanized, we explanted the condyles, and evaluated them using histological, immunohistochemical, molecular biological, and histomorphometrical methods.
  
  
  RESULTS
  Specimens with scaffold A showed severe lowering of the surface, and the defect size was larger than for scaffold B. We found more immune-competent cells around scaffold A. Chondrocytes were scarcely detected on the surface of both scaffolds. Histomorphometry of the interface between scaffold and recipient showed no significant difference regarding tissue of chondral, osseous, fibrous or implant origin or tartrate-resistant acid phosphatase-positive cells. Real-time reverse transcriptase-polymerase chain reaction analysis revealed significant up-regulation for collagen II and SOX-9 messenger ribonucleic acid expression on the surface of scaffold B compared with scaffold A.
  
  
  CONCLUSIONS
  Scaffold B proved to be stable and sufficiently integrated in the short term compared with scaffold A. More extensive evaluations with scaffold B appear to be expedient.
authors.affiliation: Department of Trauma Surgery Giessen, University Hospital of Giessen-Marburg, Justus-Liebig-University Giessen, Giessen, Germany. iris.schleicher@ortho.med.uni-giessen.de
authors.forename: Iris
authors.initials: I
authors.lastname: Schleicher
authors.forename: Katrin S
authors.initials: KS
authors.lastname: Lips
authors.forename: Ursula
authors.initials: U
authors.lastname: Sommer
authors.forename: Ines
authors.initials: I
authors.lastname: Schappat
authors.forename: Alexander P
authors.initials: AP
authors.lastname: Martin
authors.forename: Gabor
authors.initials: G
authors.lastname: Szalay
authors.forename: Sonja
authors.initials: S
authors.lastname: Hartmann
authors.forename: Reinhard
authors.initials: R
authors.lastname: Schnettler
mesh_terms: D000818:Animals; D054544:Arthroplasty, Subchondral; D019902:Chondrocytes / Q000637:transplantation*; D005260:Female; D007150:Immunohistochemistry; D012756:Sheep; D054457:Tissue Scaffolds; D014182:Transplantation, Autologous