title: Reduced bone perfusion in osteoporosis: likely causes in an ovariectomy rat model.
abstract: OBJECTIVE
  To investigate the cause of reduced vertebral perfusion in a rat ovariectomy model.
  
  
  METHODS
  Experimental protocol was approved by the local Animal Experiment Ethics Committee. Twenty-two Sprague-Dawley rats were studied. Computed tomographic bone densitometry and magnetic resonance perfusion imaging were performed at baseline and 2, 4, and 8 weeks after ovariectomy (n = 11) or sham surgery (n = 11). Perfusion parameters analyzed were maximum enhancement (E(max)) and enhancement slope (E(slope)). After the animals were sacrificed, the aorta and femoral artery were analyzed for vessel reactivity, and the lumbar vertebrae were analyzed for marrow content.
  
  
  RESULTS
  In control rats, bone mineral density (BMD), E(max), and E(slope) remained constant. In ovariectomy rats, a comparable reduction in BMD and the perfusion parameters at two weeks post-ovariectomy (BMD, 9.3%; E(max), 11.6%; E(slope), 9%) was seen 2 weeks after ovariectomy, and further reductions were seen 4 weeks (BMD, 17.5%; E(max), 15.6%; E(slope), 33%) and 8 weeks (BMD, 18.8%; E(max), 14.2%; E(slope), 33%) after ovariectomy. Endothelial dysfunction was observed in both the aorta and femoral artery of the ovariectomy group but not of the control group. Increased marrow fat area was seen in the ovariectomy group (52.9% vs 21.6%; P < .01) owing to an increase in fat cell number. Decreased erythropoetic marrow area (32.5% vs 48.6%; P < .05) was also observed in the ovariectomy group.
  
  
  CONCLUSIONS
  Reduced bone perfusion occurs in synchrony with reduced BMD. The most likely causes of reduced bone perfusion are a reduction in the amount of erythropoetic marrow and endothelial dysfunction after ovariectomy.
  
  
  BACKGROUND
  http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.09090608/-/DC1.
authors.affiliation: Departments of Diagnostic Radiology and Organ Imaging, Anatomy, Physiology, and Orthopedics and Traumatology, Prince of Wales Hospital, Chinese University of Hong Kong, Shatin, NT, Hong Kong. griffith@cuhk.edu.hk
authors.forename: James F
authors.initials: JF
authors.lastname: Griffith
authors.forename: Yi-Xiang J
authors.initials: YX
authors.lastname: Wang
authors.forename: Hua
authors.initials: H
authors.lastname: Zhou
authors.forename: Wing Hang
authors.initials: WH
authors.lastname: Kwong
authors.forename: Wing Tak
authors.initials: WT
authors.lastname: Wong
authors.forename: Yan-Lin
authors.initials: YL
authors.lastname: Sun
authors.forename: Yu
authors.initials: Y
authors.lastname: Huang
authors.forename: David K W
authors.initials: DK
authors.lastname: Yeung
authors.forename: Ling
authors.initials: L
authors.lastname: Qin
authors.forename: Anil T
authors.initials: AT
authors.lastname: Ahuja
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D015519:Bone Density; D003287:Contrast Media; D005260:Female; D007091:Image Processing, Computer-Assisted; D008159:Lumbar Vertebrae / Q000098:blood supply* / Q000000981:diagnostic imaging / Q000473:pathology*; D008279:Magnetic Resonance Imaging; D008536:Meglumine; D009942:Organometallic Compounds; D010024:Osteoporosis / Q000473:pathology*; D010052:Ovariectomy; D051381:Rats; D017207:Rats, Sprague-Dawley; D018709:Statistics, Nonparametric; D014057:Tomography, X-Ray Computed
chemical_list: D003287:Contrast Media; D009942:Organometallic Compounds; D008536:Meglumine; C072417:gadoterate meglumine