title: Microstructural remodeling of articular cartilage following defect repair by osteochondral autograft transfer.
abstract: OBJECTIVE
  To assess collagen network alterations occurring with flow and other abnormalities of articular cartilage at medial femoral condyle (MFC) sites repaired with osteochondral autograft (OATS) after 6 and 12 months, using quantitative polarized light microscopy (qPLM) and other histopathological methods.
  
  
  METHODS
  The collagen network structure of articular cartilage of OATS-repaired defects and non-operated contralateral control sites were compared by qPLM analysis of parallelism index (PI), orientation angle (α) relative to the local tissue axes, and retardance (Γ) as a function of depth. qPLM parameter maps were also compared to ICRS and Modified O'Driscoll grades, and cell and matrix sub-scores, for sections stained with H&E and Safranin-O, and for Collagen-I and II.
  
  
  RESULTS
  Relative to non-operated normal cartilage, OATS-repaired regions exhibited structural deterioration, with low PI and more horizontal α, and unique structural alteration in adjacent host cartilage: more aligned superficial zone, and reoriented deep zone lateral to the graft, and matrix disorganization in cartilage overhanging the graft. Shifts in α and PI from normal site-specific values were correlated with histochemical abnormalities and co-localized with changes in cell organization/orientation, cloning, or loss, indicative of cartilage flow, remodeling, and deterioration, respectively.
  
  
  CONCLUSIONS
  qPLM reveals a number of unique localized alterations of the collagen network in both adjacent host and implanted cartilage in OATS-repaired defects, associated with abnormal chondrocyte organization. These alterations are consistent with mechanobiological processes and the direction and magnitude of cartilage strain.
authors.affiliation: Department of Bioengineering, University of California-San Diego, La Jolla, CA 92093-0412, USA.
authors.forename: C B
authors.initials: CB
authors.lastname: Raub
authors.forename: S C
authors.initials: SC
authors.lastname: Hsu
authors.forename: E F
authors.initials: EF
authors.lastname: Chan
authors.forename: R
authors.initials: R
authors.lastname: Shirazi
authors.forename: A C
authors.initials: AC
authors.lastname: Chen
authors.forename: E
authors.initials: E
authors.lastname: Chnari
authors.forename: E J
authors.initials: EJ
authors.lastname: Semler
authors.forename: R L
authors.initials: RL
authors.lastname: Sah
mesh_terms: D000818:Animals; D002356:Cartilage / Q000637:transplantation*; D002358:Cartilage, Articular / Q000648:ultrastructure*; D016022:Case-Control Studies; D019902:Chondrocytes / Q000637:transplantation*; D003094:Collagen / Q000648:ultrastructure*; D005269:Femur / Q000637:transplantation*; D006041:Goats; D008859:Microscopy, Polarization; D013264:Stifle / Q000601:surgery / Q000648:ultrastructure; D014182:Transplantation, Autologous; D014945:Wound Healing
chemical_list: D003094:Collagen