title: FK506 protects against articular cartilage collagenous extra-cellular matrix degradation.
abstract: OBJECTIVE
  Osteoarthritis (OA) is a non-rheumatologic joint disease characterized by progressive degeneration of the cartilage extra-cellular matrix (ECM), enhanced subchondral bone remodeling, activation of synovial macrophages and osteophyte growth. Inhibition of calcineurin (Cn) activity through tacrolimus (FK506) in in vitro monolayer chondrocytes exerts positive effects on ECM marker expression. This study therefore investigated the effects of FK506 on anabolic and catabolic markers of osteoarthritic chondrocytes in 2D and 3D in vitro cultures, and its therapeutic effects in an in vivo rat model of OA.
  
  
  METHODS
  Effects of high and low doses of FK506 on anabolic (QPCR/histochemistry) and catabolic (QPCR) markers were evaluated in vitro on isolated (2D) and ECM-embedded chondrocytes (explants, 3D pellets). Severe cartilage damage was induced unilaterally in rat knees using papain injections in combination with a moderate running protocol. Twenty rats were treated with FK506 orally and compared to twenty untreated controls. Subchondral cortical and trabecular bone changes (longitudinal microCT) and macrophage activation (SPECT/CT) were measured. Articular cartilage was analyzed ex vivo using contrast enhanced microCT and histology.
  
  
  RESULTS
  FK506 treatment of osteoarthritic chondrocytes in vitro induced anabolic (mainly collagens) and reduced catabolic ECM marker expression. In line with this, FK506 treatment clearly protected ECM integrity in vivo by markedly decreasing subchondral sclerosis, less development of subchondral pores, depletion of synovial macrophage activation and lower osteophyte growth.
  
  
  CONCLUSIONS
  FK506 protected cartilage matrix integrity in vitro and in vivo. Additionally, FK506 treatment in vivo reduced OA-like responses in different articular joint tissues and thereby makes Cn an interesting target for therapeutic intervention of OA.
authors.affiliation: Department of Orthopedics, Erasmus University Medical Center, Rotterdam, The Netherlands. Electronic address: m.siebelt@erasmusmc.nl.
authors.forename: M
authors.initials: M
authors.lastname: Siebelt
authors.affiliation: Department of Orthopedics, Erasmus University Medical Center, Rotterdam, The Netherlands.
authors.forename: A E
authors.initials: AE
authors.lastname: van der Windt
authors.affiliation: Department of Nuclear Medicine, Erasmus University Medical Center, Rotterdam, The Netherlands.
authors.forename: H C
authors.initials: HC
authors.lastname: Groen
authors.affiliation: Department of Orthopedics, Erasmus University Medical Center, Rotterdam, The Netherlands.
authors.forename: M
authors.initials: M
authors.lastname: Sandker
authors.affiliation: Department of Orthopedics, Erasmus University Medical Center, Rotterdam, The Netherlands.
authors.forename: J H
authors.initials: JH
authors.lastname: Waarsing
authors.affiliation: Center for Radiopharmaceutical Sciences PSI-ETH-USZ, Paul Scherrer Institute, Villigen-PSI, Switzerland.
authors.forename: C
authors.initials: C
authors.lastname: Müller
authors.affiliation: Department of Nuclear Medicine, Erasmus University Medical Center, Rotterdam, The Netherlands.
authors.forename: M
authors.initials: M
authors.lastname: de Jong
authors.affiliation: Department of Orthopedics, Erasmus University Medical Center, Rotterdam, The Netherlands; Department of Orthopedic Surgery, University Hospital RWTH, Aachen, Germany.
authors.forename: H
authors.initials: H
authors.lastname: Jahr
authors.affiliation: Department of Biomechanical Engineering, TU Delft, The Netherlands; Department of Orthopaedics, UMC Utrecht, The Netherlands; Department of Rheumatology, UMC Utrecht, The Netherlands.
authors.forename: H
authors.initials: H
authors.lastname: Weinans
mesh_terms: D000818:Animals; D065095:Calcineurin Inhibitors / Q000494:pharmacology*; D002358:Cartilage, Articular / Q000000981:diagnostic imaging / Q000187:drug effects*; D016022:Case-Control Studies; D019902:Chondrocytes / Q000000981:diagnostic imaging / Q000187:drug effects*; D003287:Contrast Media; D004195:Disease Models, Animal; D006801:Humans; D008264:Macrophages / Q000000981:diagnostic imaging / Q000187:drug effects; D008297:Male; D020370:Osteoarthritis, Knee / Q000188:drug therapy* / Q000473:pathology; D051381:Rats; D017208:Rats, Wistar; D013264:Stifle / Q000000981:diagnostic imaging; D016559:Tacrolimus / Q000494:pharmacology*; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods; D016896:Treatment Outcome; D055114:X-Ray Microtomography / Q000379:methods
chemical_list: D065095:Calcineurin Inhibitors; D003287:Contrast Media; D016559:Tacrolimus
keywords: Activation of synovial macrophages; Cartilage matrix degradation; FK506; Osteoarthritis; Osteoclastic subchondral bone resorption