title: Repair of osteochondral defects with hyaluronan- and polyester-based scaffolds.
abstract: OBJECTIVE
  The natural repair of osteochondral defects can be enhanced with biocompatible, biodegradable materials that support the repair process. It is our hypothesis that hyaluronan-based scaffolds are superior to synthetic scaffolds because they provide biological cues. We tested this thesis by comparing two hyaluronan-based scaffolds [auto cross-linked polysaccharide polymer (ACP) and HYAFF-11] to polyester-based scaffolds [poly(DL-lactic-co-glycolic acid) (PLGA) and poly(L-lactic acid) (PLLA)] with similar pore size, porosity and degradation times.
  
  
  METHODS
  Fifty-four rabbits received bilateral osteochondral defects. One defect received a hyaluronan-based scaffold and the contralateral defect received the corresponding polyester-based scaffold. Rabbits were euthanized 4, 12 and 20 weeks after surgery and the condyles dissected and processed for histology.
  
  
  RESULTS
  Only ACP-treated defects presented bone at the base of the defect at 4 weeks. At 12 weeks, only defects treated with rapidly dissolving implants (ACP and PLGA) presented bone reconstitution consistently, while bone was present in only one third of those treated with slowly dissolving scaffolds (HYAFF-11 and PLLA). After 20 weeks, the articular surface of PLGA-treated defects presented fibrillation more frequently than in ACP-treated defects. The surface of defects treated with slowly dissolving scaffolds presented more cracks and fissures.
  
  
  CONCLUSIONS
  The degradation rate of the scaffolds is critical for the repair process. Slowly dissolving scaffolds sustain thicker cartilage at the surface but, it frequently presents cracks and discontinuities. These scaffolds also delay bone formation at the base of the defects. Hyaluronan-based scaffolds appear to allow faster cell infiltration leading to faster tissue formation. The degradation of ACP leads to rapid bone formation while the slow degradation of HYAFF-11 prolongs the presence of cartilage and delays endochondral bone formation.
authors.affiliation: Department of Orthopaedics, Case Western Reserve University School of Medicine and University Hospitals of Cleveland, Cleveland, OH, USA. las29@po.cwru.edu
authors.forename: Luis A
authors.initials: LA
authors.lastname: Solchaga
authors.forename: Johnna S
authors.initials: JS
authors.lastname: Temenoff
authors.forename: Jizong
authors.initials: J
authors.lastname: Gao
authors.forename: Antonios G
authors.initials: AG
authors.lastname: Mikos
authors.forename: Arnold I
authors.initials: AI
authors.lastname: Caplan
authors.forename: Victor M
authors.initials: VM
authors.lastname: Goldberg
mesh_terms: D000818:Animals; D001672:Biocompatible Materials; D018786:Bone Substitutes / Q000627:therapeutic use*; D002358:Cartilage, Articular / Q000293:injuries* / Q000473:pathology; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D020219:Chondrogenesis; D006820:Hyaluronic Acid / Q000627:therapeutic use* / Q000648:ultrastructure; D008422:Materials Testing / Q000379:methods; D008855:Microscopy, Electron, Scanning; D011091:Polyesters / Q000737:chemistry / Q000627:therapeutic use; D011817:Rabbits; D023822:Tissue Engineering / Q000379:methods*; D014945:Wound Healing / Q000502:physiology
chemical_list: D001672:Biocompatible Materials; D018786:Bone Substitutes; D011091:Polyesters; D006820:Hyaluronic Acid