title: Nondestructive assessment of sGAG content and distribution in normal and degraded rat articular cartilage via EPIC-microCT.
abstract: OBJECTIVE
  The objective of this study was to evaluate the feasibility of quantifying the Equilibrium Partitioning of an Ionic Contrast agent via Microcomputed Tomography (EPIC-microCT) to nondestructively assess sulfated glycosaminoglycan (sGAG) content and distribution in rat articular cartilage ex vivo, and in doing so to establish a paradigm for extension of this technique to other small animal models.
  
  
  METHODS
  After determination of an appropriate incubation time for the anionic contrast agent, EPIC-microCT was used to examine age-related differences in cartilage sGAG content between 4-, 8-, and 16-week old (n=5 each) male Wistar rats and to evaluate sGAG depletion in the right femora of each age group after 60 min of digestion with chondroitinase ABC. The EPIC-microCT measurements were validated by histological safranin-O staining, and reproducibility was evaluated by triplicate scans of six femora.
  
  
  RESULTS
  Cartilage attenuation gradually increased with cumulative digestion time and reached a plateau at approximately 60 min with a 16.0% temporal increase (P<0.01). Average femoral articular cartilage attenuation increased by 14.2% from 4- to 8-weeks of age (P<0.01) and further increased by 2.5% from 8 to 16 weeks (P<0.05). After 60 min of digestion, femoral articular cartilage attenuations increased by 15-17% in each age group (P<0.01). Correspondingly, sGAG optical density decreased with age and digestion, and showed a linear correlation (r=-0.88, slope=-1.26, P<0.01, n=30) with EPIC-microCT cartilage attenuation. High reproducibility was indicated by a low coefficient of variation (1.5%) in cartilage attenuation.
  
  
  CONCLUSIONS
  EPIC-microCT imaging provides high spatial resolution and sensitivity to assess sGAG content and three-dimensional distribution in rat femoral articular cartilage.
authors.affiliation: George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0405, USA.
authors.forename: L
authors.initials: L
authors.lastname: Xie
authors.forename: A S P
authors.initials: AS
authors.lastname: Lin
authors.forename: R E
authors.initials: RE
authors.lastname: Guldberg
authors.forename: M E
authors.initials: ME
authors.lastname: Levenston
mesh_terms: D000818:Animals; D002358:Cartilage, Articular / Q000000981:diagnostic imaging* / Q000378:metabolism* / Q000473:pathology; D003287:Contrast Media; D004195:Disease Models, Animal; D005269:Femur / Q000000981:diagnostic imaging; D006025:Glycosaminoglycans / Q000032:analysis*; D021621:Imaging, Three-Dimensional / Q000379:methods; D008297:Male; D008852:Microradiography; D051381:Rats; D017208:Rats, Wistar; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D003287:Contrast Media; D006025:Glycosaminoglycans; C013786:A73025