title: Ex vivo visualization of the mouse otoconial layer compared with micro-computed tomography.
abstract: OBJECTIVE
  Micro-computed tomography (micro-CT) is useful for assessing the 3-dimensional (3D) morphology and age-related changes of the otoconial layer.
  
  
  BACKGROUND
  Wriggle mouse Sagami (WMS) is a mutant of the plasma membrane Ca2+ ATPase type2 gene (Atp2b2) with deficits in the saccular otoconia. We examined the effectiveness of micro-CT in evaluating the otoconial layer of WMS and C57BL/6J mice.
  
  
  METHODS
  Otic capsules of C57BL/6J mice at different fixation time were examined using micro-CT to evaluate the effects of the fixation time on the otoconial layer. Otic capsules of Atp2b2(wri/wri), Atp2b2(wri/+), and Atp2b2(+/+) mice at P14, P21, and the age of 3 months were used to analyze age-related changes in the otoconial layer. A series of cross-section and 3D reconstructed images of the otoconial layer were obtained. The micro-CT findings were compared with the otic capsule findings cleared in methyl salicylate using stereomicroscopy.
  
  
  RESULTS
  Micro-CT produced high-resolution images of the otoconial layer, thereby providing information regarding the spatial configuration and 3D curvature. There were no changes between the different fixation times. In the Atp2b2(wri/+) and Atp2b2(+/+) mice, the saccular and utricular otoconial layers were normal among all age groups. In the Atp2b2(wri/wri) mice, the saccular otoconial layer decreased on P14 and was absent on P21, whereas the utricular otoconial layer disappeared at 3 months of age.
  
  
  CONCLUSIONS
  We obtained precise information regarding the mouse otoconial layer with minimum artifacts. This method is expected to improve our understanding of the physiologic function and age-related changes in otolith organs.
authors.affiliation: Department of Otorhinolaryngology, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan.
authors.forename: Keiji
authors.initials: K
authors.lastname: Honda
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Noguchi
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Kawashima
authors.forename: Masatoki
authors.initials: M
authors.lastname: Takahashi
authors.forename: Ayako
authors.initials: A
authors.lastname: Nishio
authors.forename: Ken
authors.initials: K
authors.lastname: Kitamura
mesh_terms: D000818:Animals; D034381:Hearing Loss / Q000000981:diagnostic imaging* / Q000235:genetics; D051379:Mice; D009154:Mutation; D010037:Otolithic Membrane / Q000000981:diagnostic imaging*; D053499:Plasma Membrane Calcium-Transporting ATPases / Q000235:genetics; D055114:X-Ray Microtomography
chemical_list: D053499:Plasma Membrane Calcium-Transporting ATPases; C506959:Atp2b2 protein, mouse