title: Altered in vitro chondrogenic properties of chondrocytes harvested from unaffected cartilage in osteoarthritic joints.
abstract: OBJECTIVE
  In vitro models of chondrogenesis often depart from chondrocytes harvested from less-affected areas of osteoarthritic joints. However, there are indications that these chondrocytes are phenotypically different from chondrocytes from healthy joints and thus might differ in their capacity to generate hyaline cartilage. The goal of this study was to compare the chondrogenic capacity of chondrocytes from healthy and OA joints.
  
  
  METHODS
  Chondrocytes isolated from nine healthy and nine OA knee joints were expanded in monolayer for two passages. Chondrocytes from passages 1 and 2 were analyzed for expression of (de)differentiation and hypertrophy markers and were seeded at passage 2 on collagen-coated filters for redifferentiation culture to study cartilage matrix formation.
  
  
  RESULTS
  The collagen II/I mRNA ratio, reflecting differentiation, decreased from passage 1 to 2 in both chondrocytes from OA joints and chondrocytes from healthy joints (P<0.05), without a significant difference between the two donor types. At passage 1, levels of the cartilage transcription factors Sox-5, Sox-6 and Sox-9 appeared to be higher in chondrocytes from OA joints (n.s.), but this was not seen at passage 2. However, a clear difference was observed in collagen type X expression, which was high in chondrocytes from OA joints at both passages, while undetectable in chondrocytes from healthy joints (P<0.01). Tissue generated by chondrocytes from healthy joints redifferentiated for 28 days, showed a significantly better morphology, as assessed by histological scoring (P<0.01) and higher proteoglycan content (P<0.05), compared to chondrocytes from OA joints. Matrix turnover parameters, i.e., proteoglycan synthesis and degradation rate, were not significantly affected by donor tissue origin.
  
  
  CONCLUSIONS
  These results suggest that clear differences between chondrocytes from healthy and OA joints exist and that these are not completely abolished during the process of de- and redifferentiation. Therefore, in vitro cartilage regeneration models, which use chondrocytes from OA joints, should be interpreted with care.
authors.affiliation: Department of Orthopaedics, University Medical Center Utrecht, PO Box 85500, 3508 GA Utrecht, The Netherlands. g.auwyang@chir.azu.nl
authors.forename: K G A
authors.initials: KG
authors.lastname: Yang
authors.forename: D B F
authors.initials: DB
authors.lastname: Saris
authors.forename: R E
authors.initials: RE
authors.lastname: Geuze
authors.forename: M H P
authors.initials: MH
authors.lastname: van Rijen
authors.forename: Y J M
authors.initials: YJ
authors.lastname: van der Helm
authors.forename: A J
authors.initials: AJ
authors.lastname: Verbout
authors.forename: L B
authors.initials: LB
authors.lastname: Creemers
authors.forename: W J A
authors.initials: WJ
authors.lastname: Dhert
mesh_terms: D000368:Aged; D002358:Cartilage, Articular / Q000502:physiology* / Q000503:physiopathology; D002454:Cell Differentiation / Q000502:physiology; D019902:Chondrocytes / Q000502:physiology*; D020219:Chondrogenesis / Q000502:physiology*; D024042:Collagen Type I / Q000032:analysis; D024043:Collagen Type II / Q000032:analysis; D005260:Female; D006025:Glycosaminoglycans / Q000032:analysis; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods; D007719:Knee Joint / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000503:physiopathology; D011509:Proteoglycans / Q000032:analysis; D012333:RNA, Messenger / Q000032:analysis; D014157:Transcription Factors / Q000032:analysis
chemical_list: D024042:Collagen Type I; D024043:Collagen Type II; D006025:Glycosaminoglycans; D011509:Proteoglycans; D012333:RNA, Messenger; D014157:Transcription Factors