title: Is cartilage sGAG content related to early changes in cartilage disease? Implications for interpretation of dGEMRIC.
abstract: OBJECTIVE
  This study investigates sulphated glycosaminoglycans (sGAG) content changes in early osteoarthritis (OA), and whether contrast-enhanced magnetic resonance imaging (MRI) of cartilage in vitro may identify early event of OA pathology.
  
  
  METHODS
  Osteochondral plugs from patients with hip OA or femoral neck fracture (reference group) were collected and analysed by 1.5 T MRI with ΔR1 as a measure of cartilage contrast concentration. Cartilage hydration, contents of sGAG, cartilage oligomeric matrix protein (COMP), hydroxyproline, denatured collagen, and aggrecan TEGE(392) neoepitope were determined and histological grading was performed.
  
  
  RESULTS
  sGAG content correlated to ΔR1, although no difference in either of these parameters was detectable between OA and reference cartilage at 4 h of contrast equilibration. In contrast, biochemical analysis of other cartilage matrix constituents showed distinct alterations typical for early cartilage degradation in OA cartilage and with clear evidence for increased aggrecan turnover.
  
  
  CONCLUSIONS
  In the present in vitro study, cartilage sGAG content could not distinguish between early OA cartilage and reference cartilage. Given, that delayed gadolinium enhanced MRI of cartilage (dGEMRIC) indicates early events in the pathogenesis of OA in vivo, our results from the in vitro studies imply other, additional factors than cartilage sGAG content, e.g., alterations in diffusion or increased supply of contrast agent in the diseased joint. Alternatively, an altered dGEMRIC reflects later stages of OA, when sGAG content decreases. Further investigations are warranted, to understand variations in sGAG content in pathology, an essential background for interpreting dGEMRIC measurements.
authors.affiliation: Joint and Soft Tissue Unit, Department of Clinical Sciences Malmö, Lund University, Department of Orthopaedics, Skåne University Hospital, Malmö, SE-20502 Malmö, Sweden. Electronic address: Johann.Stubendorff@med.lu.se.
authors.forename: J J
authors.initials: JJ
authors.lastname: Stubendorff
authors.affiliation: Joint and Soft Tissue Unit, Department of Clinical Sciences Malmö, Lund University, Department of Orthopaedics, Skåne University Hospital, Malmö, SE-20502 Malmö, Sweden; Department of Diagnostic Radiology, Oulu University Hospital, POB 50, FI-90029 OYS, Oulu, Finland.
authors.forename: E
authors.initials: E
authors.lastname: Lammentausta
authors.affiliation: Department of Orthopaedics, Clinical Sciences Lund, Lund University, Lund 221 84, Sweden.
authors.forename: A
authors.initials: A
authors.lastname: Struglics
authors.affiliation: Joint and Soft Tissue Unit, Department of Clinical Sciences Malmö, Lund University, Department of Orthopaedics, Skåne University Hospital, Malmö, SE-20502 Malmö, Sweden.
authors.forename: L
authors.initials: L
authors.lastname: Lindberg
authors.affiliation: Department of Clinical Sciences Lund, BMC C12 Lund University, SE-22184 Lund, Sweden.
authors.forename: D
authors.initials: D
authors.lastname: Heinegård
authors.affiliation: Joint and Soft Tissue Unit, Department of Clinical Sciences Malmö, Lund University, Department of Orthopaedics, Skåne University Hospital, Malmö, SE-20502 Malmö, Sweden.
authors.forename: L E
authors.initials: LE
authors.lastname: Dahlberg
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers / Q000378:metabolism; D002358:Cartilage, Articular / Q000378:metabolism* / Q000473:pathology; D003287:Contrast Media / Q000493:pharmacokinetics; D042241:Early Diagnosis; D005265:Femoral Neck Fractures / Q000378:metabolism; D005270:Femur Head / Q000378:metabolism; D019786:Gadolinium DTPA / Q000493:pharmacokinetics; D006025:Glycosaminoglycans / Q000378:metabolism*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008875:Middle Aged; D015207:Osteoarthritis, Hip / Q000175:diagnosis / Q000378:metabolism*; D058866:Osteoporotic Fractures / Q000378:metabolism
chemical_list: D015415:Biomarkers; D003287:Contrast Media; D006025:Glycosaminoglycans; C013786:A73025; D019786:Gadolinium DTPA