title: Determination of a critical size calvarial defect in senile osteoporotic mice model based on in vivo micro-computed tomography and histological evaluation.
abstract: OBJECTIVE
  To evaluate differences in the spontaneous healing capacity of senescence-prone inbred strains (SAMP6) and senescence-resistant inbred strains (SAMR1) and determine the critical defect size in a mouse model of senescence-accelerated osteoporosis.
  
  
  METHODS
  Unilateral full-thickness calvarial defects 2 or 4mm in diameter were made in 6-month-old male SAMP6 and SAMR1. Defects were evaluated in vivo by micro-CT at day 0 and 6 and 12 weeks postoperatively. Calvarial specimens were harvested at 12 weeks for hematoxylin and eosin staining, Masson's trichrome staining, and tartrate-resistant-acid-phosphatase (TRAP) staining.
  
  
  RESULTS
  Less new bone was observed in defects in SAMP6 compared to SAMR1 at 12 weeks postsurgery, with <5% healing in SAMP6 for both 2- and 4-mm defects compared to >5% healing in 2-mm defects in SAMRI (P<0.05). Histological analysis revealed dense connective tissue but little bone healing in 2- and 4-mm defects in SAMP6 and 4-mm defects in SAMR1. New bone was observed at the periphery of the 2-mm defects in SAMR1. Masson's trichrome staining also supported these findings. No obvious TRAP-positive cells were observed at the defect margins, but SAMP6 exhibited greater osteoclast numbers and surface areas in the diploë of contralateral bone compared to smaller osteoblast numbers and surface areas at the defect sites in SAMR1.
  
  
  CONCLUSIONS
  Defects of 2mm or larger in the cranium was critical-size or nonhealing defects in both SAMP6 and SAMR1. The differential findings on micro-CT and histomorphometry for the calvarial defect sites between SAMP6 and SAMR1 may imply different regenerative abilities of intramembranous ossification in these two strains.
authors: Department of Prosthodontics, Stomatological Hospital of Chongqing Medical University, No. 426 Songshibei Road, Yubei, Chongqing 401147, China; Chongqing key Laboratory of Oral Diseases and Biomedical Sciences, Chongqing 401147, China.
authors: Yufeng
authors: Y
authors: Zhang
authors: Department of Prosthodontics, Stomatological Hospital of Chongqing Medical University, No. 426 Songshibei Road, Yubei, Chongqing 401147, China; Chongqing key Laboratory of Oral Diseases and Biomedical Sciences, Chongqing 401147, China. Electronic address: wanglu@sina.com.
authors: Lu
authors: L
authors: Wang
authors: Chongqing key Laboratory of Oral Diseases and Biomedical Sciences, Chongqing 401147, China; Department of Orthodontics, Stomatological Hospital of Chongqing Medical University, No. 426 Songshibei Road, Yubei, Chongqing 401147, China.
authors: Feng
authors: F
authors: Deng
authors: Key Laboratory of Biochemistry and Molecular Pharmacology, Department of Pharmacology, School of Pharmacy, Chongqing Medical University, Yixueyuan Road, Yuzhong, Chongqing 400016, China.
authors: Hongmei
authors: H
authors: Qiu
authors: Department of Prosthodontics, Stomatological Hospital of Chongqing Medical University, No. 426 Songshibei Road, Yubei, Chongqing 401147, China; Chongqing key Laboratory of Oral Diseases and Biomedical Sciences, Chongqing 401147, China. Electronic address: hiwxh@hotmail.com.
authors: Xiaohong
authors: X
authors: Wu
mesh_terms: D000375:Aging; D000818:Animals; D001842:Bone and Bones / Q000000981:diagnostic imaging*; D004195:Disease Models, Animal; D008297:Male; D051379:Mice; D010024:Osteoporosis / Q000000981:diagnostic imaging* / Q000473:pathology*; D055114:X-Ray Microtomography / Q000379:methods*
keywords: Bone healing; Critical size defect; In vivo micro-CT; Osteoporosis; SAMP6