title: Evidence of chondrocyte repopulation in adult ovine articular cartilage following cryoinjury and long-term transplantation.
abstract: OBJECTIVE
  To characterize the response of articular chondrocytes to a specific cryoinjury that leads to cluster formation following long-term transplantation.
  
  
  METHODS
  Osteochondral dowels from 20 adult sheep were cryopreserved to optimize the recovery of chondrocytes immediately after thawing. The dowels were transplanted as allografts and observed at 3 and 12 months. Chondrocyte distribution and viability was assessed using paravital dyes after transplantation. Chondrocyte phenotype was assessed by in situ hybridization and immunohistochemistry to detect type II collagen. An anticentrosome antibody was used to identify cells undergoing cell cycle progression towards mitosis.
  
  
  RESULTS
  All cryopreserved grafts showed the presence of spheroidal clusters of chondrocytes 1 year after transplantation while the host cartilage adjacent to the graft appeared morphologically normal. The average size of the clusters increased from four cells at 3 months to 12 cells at 1 year. The chondrocytes in the clusters displayed newly formed type II collagen protein and mRNA. Some cells within clusters were observed with two centrosomes, indicative of cells progressing through the S phase of the cell cycle.
  
  
  CONCLUSIONS
  Adult articular chondrocytes retain the ability to repopulate the matrix, an ability which is demonstrated with this specific cryoinjury. This may be an initial stage of cartilage regeneration.
authors.affiliation: University of Calgary, Alberta, Canada.
authors.forename: K
authors.initials: K
authors.lastname: Muldrew
authors.forename: M
authors.initials: M
authors.lastname: Chung
authors.forename: K
authors.initials: K
authors.lastname: Novak
authors.forename: N S
authors.initials: NS
authors.lastname: Schachar
authors.forename: R F
authors.initials: RF
authors.lastname: Zernicke
authors.forename: L E
authors.initials: LE
authors.lastname: McGann
authors.forename: J B
authors.initials: JB
authors.lastname: Rattner
authors.forename: J R
authors.initials: JR
authors.lastname: Matyas
mesh_terms: D000818:Animals; D002358:Cartilage, Articular / Q000637:transplantation*; D002455:Cell Division / Q000502:physiology; D002470:Cell Survival / Q000502:physiology; D019902:Chondrocytes / Q000166:cytology / Q000378:metabolism*; D003094:Collagen / Q000235:genetics / Q000378:metabolism; D015925:Cryopreservation; D005260:Female; D008938:Mitosis; D023421:Models, Animal; D010003:Osteoarthritis / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis; D012756:Sheep; D014184:Transplantation, Homologous
chemical_list: D012333:RNA, Messenger; D003094:Collagen