title: Oligo[poly(ethylene glycol)fumarate] hydrogel enhances osteochondral repair in porcine femoral condyle defects.
abstract: BACKGROUND
  Management of osteochondritis dissecans remains a challenge. Use of oligo[poly(ethylene glycol)fumarate] (OPF) hydrogel scaffold alone has been reported in osteochondral defect repair in small animal models. However, preclinical evaluation of usage of this scaffold alone as a treatment strategy is limited.
  
  
  OBJECTIVE
  We therefore (1) determined in vitro pore size and mechanical stiffness of freeze-dried and rehydrated freeze-dried OPF hydrogels, respectively; (2) assessed in vivo gross defect filling percentage and histologic findings in defects implanted with rehydrated freeze-dried hydrogels for 2 and 4 months in a porcine model; (3) analyzed highly magnified histologic sections for different types of cartilage repair tissues, subchondral bone, and scaffold; and (4) assessed neotissue filling percentage, cartilage phenotype, and Wakitani scores.
  
  
  METHODS
  We measured pore size of freeze-dried OPF hydrogel scaffolds and mechanical stiffness of fresh and rehydrated forms. Twenty-four osteochondral defects from 12 eight-month-old micropigs were equally divided into scaffold and control (no scaffold) groups. Gross and histologic examination, one-way ANOVA, and one-way Mann-Whitney U test were performed at 2 and 4 months postoperatively.
  
  
  RESULTS
  Pore sizes ranged from 20 to 433 μm in diameter. Rehydrated freeze-dried scaffolds had mechanical stiffness of 1 MPa. The scaffold itself increased percentage of neotissue filling at both 2 and 4 months to 58% and 54%, respectively, with hyaline cartilage making up 39% of neotissue at 4 months.
  
  
  CONCLUSIONS
  Rehydrated freeze-dried OPF hydrogel can enhance formation of hyaline-fibrocartilaginous mixed repair tissue of osteochondral defects in a porcine model.
  
  
  CONCLUSIONS
  Rehydrated freeze-dried OPF hydrogel alone implanted into cartilage defects is insufficient to generate a homogeneously hyaline cartilage repair tissue, but its spacer effect can be enhanced by other tissue-regenerating mediators.
authors: Cartilage Repair Program, Therapeutic Tissue Engineering Laboratory, Department of Orthopaedic Surgery, National University Health System, National University Hospital, Yong Loo Lin School of Medicine, National University of Singapore, 1E, Kent Ridge Road, Singapore, 119288, Singapore. james_hui@nuhs.edu.sg
authors: James H
authors: JH
authors: Hui
authors: Xiafei
authors: X
authors: Ren
authors: Mohd Hassan
authors: MH
authors: Afizah
authors: Kerm Sin
authors: KS
authors: Chian
authors: Antonios G
authors: AG
authors: Mikos
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D002358:Cartilage, Articular / Q000473:pathology / Q000601:surgery*; D004195:Disease Models, Animal; D005269:Femur / Q000473:pathology / Q000601:surgery*; D005650:Fumarates / Q000494:pharmacology*; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D010008:Osteochondritis Dissecans / Q000473:pathology / Q000601:surgery*; D011092:Polyethylene Glycols / Q000494:pharmacology*; D018709:Statistics, Nonparametric; D013552:Swine; D013556:Swine, Miniature; D054457:Tissue Scaffolds; D014945:Wound Healing / Q000187:drug effects*
chemical_list: D005650:Fumarates; C508734:poly(ethylene glycol fumarate); D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D011092:Polyethylene Glycols