title: The biomaterial-mediated healing of critical size bone defects in the ovariectomized rat.
abstract: This study demonstrated an impaired biomaterial-mediated bone regeneration in a critical sized calvarial defect established within an ovariectomized rat model. Histological and microtomographic evidences were supported by an impaired osteoblastic gene expression and altered expression of estrogen receptors and adipogenic markers.
  
  
  BACKGROUND
  This work aims to address the bone regeneration process in the ovariectomized rat model, by assessing a calvarial critical size defect implanted with a biocompatible bovine bone mineral graft.
  
  
  METHODS
  Animals were randomly divided into two groups: Ovx (bilateral ovariectomy) and Sham (control surgery). Following 8 weeks, all animals were submitted to a surgical bicortical craniotomy (5-mm circular critical size defect), which was filled with a biocompatible mineral graft. Animals were euthanized at 1, 3, and 6 months following graft implantation (n = 10), and results on the orthotopic bone regeneration process were blindly evaluated by radiographic, microtomographic, histological, histomorphometric, and gene expression techniques.
  
  
  RESULTS
  In the attained model, in both Sham and Ovx groups, the bone regenerative process was found to occur in a slow-paced manner. Likewise, a qualitative evaluation of the microtomographic and histological analysis, as well as quantitative data from histomorphometric indexes, revealed reduced bone regeneration in Ovx animals, at the assayed time points. Significant differences were attained at the 3 and 6 months. Gene expression analysis revealed a reduced expression of osteoblastic-related genes and an altered expression of estrogen receptors and adipogenic markers, within the regenerating bone of Ovx animals.
  
  
  CONCLUSIONS
  Due to the similarities between the osteoporotic animal model and the human condition of postmenopausal osteoporosis, it might be relevant to consider the potential clinical implication of the osteoporotic condition in the biomaterial-mediated bone tissue healing/regeneration process.
authors.affiliation: Surgery Department, Faculty of Dental Medicine, University of Porto, Rua Dr. Manuel Pereira da Silva, 4200-393, Porto, Portugal.
authors.forename: S F
authors.initials: SF
authors.lastname: Durão
authors.forename: P S
authors.initials: PS
authors.lastname: Gomes
authors.forename: B J
authors.initials: BJ
authors.lastname: Colaço
authors.forename: J C
authors.initials: JC
authors.lastname: Silva
authors.forename: H M
authors.initials: HM
authors.lastname: Fonseca
authors.forename: J R
authors.initials: JR
authors.lastname: Duarte
authors.forename: A C
authors.initials: AC
authors.lastname: Felino
authors.forename: M H
authors.initials: MH
authors.lastname: Fernandes
mesh_terms: D000818:Animals; D001672:Biocompatible Materials / Q000627:therapeutic use; D001861:Bone Regeneration / Q000502:physiology*; D016025:Bone Transplantation / Q000379:methods*; D004195:Disease Models, Animal; D005260:Female; D005786:Gene Expression Regulation / Q000502:physiology; D006801:Humans; D010006:Osteoblasts / Q000378:metabolism; D015663:Osteoporosis, Postmenopausal / Q000503:physiopathology*; D010052:Ovariectomy; D017208:Rats, Wistar; D012886:Skull / Q000000981:diagnostic imaging / Q000293:injuries / Q000502:physiology; D014945:Wound Healing / Q000502:physiology; D055114:X-Ray Microtomography
chemical_list: D001672:Biocompatible Materials