title: Detecting cathepsin activity in human osteoarthritis via activity-based probes.
abstract: BACKGROUND
  Lysosomal cathepsins have been reported to contribute to Osteoarthritis (OA) pathophysiology due to their increase in pro-inflammatory conditions. Given the causal role of cathepsins in OA, monitoring their specific activity could provide means for assessing OA severity. To this end, we herein sought to assess a cathepsin activity-based probe (ABP), GB123, in vitro and in vivo.
  
  
  METHODS
  Protein levels and activity of cathepsins B and S were monitored by immunoblot analysis and GB123 labeling in cultured primary chondrocytes and conditioned media, following stimuli with tumor necrosis factor alpha (TNFα) and/or Interleukin 1 beta (IL-1β). Similarly, cathepsin activity was examined in sections of intact cartilage (IC) and degraded cartilage (DC) regions of OA. Finally, synovial fluid (SF) and serum from donors with no signs of diseases, early OA, late OA and rheumatoid arthritis (RA) patients were analyzed with GB123 to detect distinct activity levels of cathepsin B and S.
  
  
  RESULTS
  Cathepsin activity in cell lysates, conditioned media explants and DC sections showed enhanced enzymatic activity of cathepsins B and S. Further histological analysis revealed that cathepsin activity was found higher in superficial zones of DC than in IC. Examining serum and SF revealed that cathepsin B is significantly elevated with OA severity in serum and SF, yet levels of cathepsin S are more correlated with synovitis and RA.
  
  
  CONCLUSIONS
  Based on our data, cathepsin activity monitored by ABPs correlated well with OA severity and joint inflammation, directing towards a novel etiological target for OA, which possesses significant translational potential in developing means for non-invasive detection of early signs of OA.
authors.affiliation: Laboratory of Cartilage Biology, Institute of Dental Sciences, Hebrew University of Jerusalem, PO BOX 12272, Ein Kerem Campus, Jerusalem, 9112001, Israel. louisa.ben-aderet@mail.huji.ac.il.
authors.forename: Louisa
authors.initials: L
authors.lastname: Ben-Aderet
authors.affiliation: School of Pharmacy- Institute for Drug Research, Hebrew University of Jerusalem, PO BOX 12065, Ein Kerem Campus, Jerusalem, 9112001, Israel. emmanuellem@savion.huji.ac.il.
authors.forename: Emmanuelle
authors.initials: E
authors.lastname: Merquiol
authors.affiliation: School of Pharmacy- Institute for Drug Research, Hebrew University of Jerusalem, PO BOX 12065, Ein Kerem Campus, Jerusalem, 9112001, Israel. duhafahham@gmail.com.
authors.forename: Duha
authors.initials: D
authors.lastname: Fahham
authors.affiliation: Laboratory of Cartilage Biology, Institute of Dental Sciences, Hebrew University of Jerusalem, PO BOX 12272, Ein Kerem Campus, Jerusalem, 9112001, Israel. ashokbiot@gmail.com.
authors.forename: Ashok
authors.initials: A
authors.lastname: Kumar
authors.affiliation: Laboratory of Cartilage Biology, Institute of Dental Sciences, Hebrew University of Jerusalem, PO BOX 12272, Ein Kerem Campus, Jerusalem, 9112001, Israel. reich.eli@gmail.com.
authors.forename: Eli
authors.initials: E
authors.lastname: Reich
authors.affiliation: School of Pharmacy- Institute for Drug Research, Hebrew University of Jerusalem, PO BOX 12065, Ein Kerem Campus, Jerusalem, 9112001, Israel. yaelben@ekmd.huji.ac.il.
authors.forename: Yael
authors.initials: Y
authors.lastname: Ben-Nun
authors.affiliation: Joint Replacement and Reconstructive Surgery Unit, Orthopaedic Surgery Complex, Hadassah Mount Scopus Hospital, Jerusalem, Israel. kandel@hadassah.org.il.
authors.forename: Leonid
authors.initials: L
authors.lastname: Kandel
authors.affiliation: Joint Replacement and Reconstructive Surgery Unit, Orthopaedic Surgery Complex, Hadassah Mount Scopus Hospital, Jerusalem, Israel. dhaz332@hadassah.org.il.
authors.forename: Amir
authors.initials: A
authors.lastname: Haze
authors.affiliation: Joint Replacement and Reconstructive Surgery Unit, Orthopaedic Surgery Complex, Hadassah Mount Scopus Hospital, Jerusalem, Israel. liebergall@hadassah.org.il.
authors.forename: Meir
authors.initials: M
authors.lastname: Liebergall
authors.affiliation: Department of Orthopaedics, Laboratory for Experimental Orthopaedics, Justus-Liebig-University of Giessen, Giessen, Germany. m.kosinska@gmail.com.
authors.forename: Marta K
authors.initials: MK
authors.lastname: Kosińska
authors.affiliation: Department of Orthopaedics, Laboratory for Experimental Orthopaedics, Justus-Liebig-University of Giessen, Giessen, Germany. Juergen.Steinmeyer@ortho.med.uni-giessen.de.
authors.forename: Juergen
authors.initials: J
authors.lastname: Steinmeyer
authors.affiliation: Department of Biochemistry and Molecular and Structural Biology, Jozef Stefan Institute, Ljubljana, Slovenia. boris.turk@ijs.si.
authors.forename: Boris
authors.initials: B
authors.lastname: Turk
authors.affiliation: School of Pharmacy- Institute for Drug Research, Hebrew University of Jerusalem, PO BOX 12065, Ein Kerem Campus, Jerusalem, 9112001, Israel. galiabl@ekmd.huji.ac.il.
authors.forename: Galia
authors.initials: G
authors.lastname: Blum
authors.affiliation: Laboratory of Cartilage Biology, Institute of Dental Sciences, Hebrew University of Jerusalem, PO BOX 12272, Ein Kerem Campus, Jerusalem, 9112001, Israel. monad@ekmd.huji.ac.il.
authors.forename: Mona
authors.initials: M
authors.lastname: Dvir-Ginzberg
mesh_terms: D000368:Aged; D002401:Cathepsin B / Q000032:analysis / Q000378:metabolism*; D002478:Cells, Cultured; D019902:Chondrocytes / Q000737:chemistry / Q000378:metabolism; D004789:Enzyme Activation / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D010003:Osteoarthritis / Q000201:enzymology* / Q000473:pathology*; D012720:Severity of Illness Index; D013194:Staining and Labeling / Q000379:methods*; D055815:Young Adult
chemical_list: C533912:CTSB protein, human; D002401:Cathepsin B