title: Retinoic acid enhances the effect of collagen on bone union, following induced non-union defect in guinea pig ulna.
abstract: OBJECTIVE
  The aim of the present study is to evaluate the involvement of retinoic acid and collagen in wound healing, by combining them in a therapeutic modality for treating a non-union bone defect in a guinea-pig ulnar-bone model.
  
  
  METHODS
  a 4-mm disc was excised from the guinea-pig's ulnar-bone, and the space formed between the two ulnar fragments was filled with either collagen solution, retinoic acid solution or a combination of both. The guinea-pigs were sacrificed 2 or 6 weeks later, and the defected ulnar bones were studied by X-ray, by histology and by computerized histomorphometry.
  
  
  RESULTS
  After 6 weeks, the long bone area fraction within the histological sections of the bone, was increased after treatment with this mixture by 180%, as compared to the untreated controls. The cartilage area in those sections was decreased by 44% after the combined treatment, as compared to increases of 133% and 182% following treatments with collagen alone.
  
  
  CONCLUSIONS
  These findings demonstrate that addition of 500 IU of retinoic acid to collagen at a site of a bone defect, is superior to either agent in enhancing regeneration of new bone, achieving union across the defect and leading to its complete repair.
authors.affiliation: Division of Oral Pathology and Laboratory of Biomineralization, The Hebrew University-Hodassah Faculty of Dental Medicine, Jerusalem, Israel.
authors.forename: J
authors.initials: J
authors.lastname: Sela
authors.forename: D
authors.initials: D
authors.lastname: Kaufman
authors.forename: S
authors.initials: S
authors.lastname: Shoshan
authors.forename: J
authors.initials: J
authors.lastname: Shani
mesh_terms: D000818:Animals; D001846:Bone Development / Q000187:drug effects*; D020219:Chondrogenesis / Q000187:drug effects; D003094:Collagen / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D006168:Guinea Pigs; D007091:Image Processing, Computer-Assisted; D008297:Male; D014212:Tretinoin / Q000494:pharmacology*; D014457:Ulna / Q000187:drug effects / Q000254:growth & development*; D014945:Wound Healing / Q000187:drug effects
chemical_list: D014212:Tretinoin; D003094:Collagen