title: Inhibition of Notch1 promotes hedgehog signalling in a HES1-dependent manner in chondrocytes and exacerbates experimental osteoarthritis.
abstract: OBJECTIVE
  Notch ligands and receptors have recently been shown to be differentially expressed in osteoarthritis (OA). We aim to further elucidate the functional role of Notch signalling in OA using Notch1 antisense transgenic (Notch1 AS) mice.
  
  
  METHODS
  Notch and hedgehog signalling were analysed by real-time PCR and immunohistochemistry. Notch-1 AS mice were employed as a model of impaired Notch signalling in vivo. Experimental OA was induced by destabilisation of the medial meniscus (DMM). The extent of cartilage destruction and osteophyte formation was analysed by safranin-O staining with subsequent assessment of the Osteoarthritis Research Society International (OARSI) and Mankin scores and µCT scanning. Collagen X staining was used as a marker of chondrocyte hypertrophy. The role of hairy/enhancer of split 1 (Hes-1) was investigated with knockdown and overexpression experiments.
  
  
  RESULTS
  Notch signalling was activated in human and murine OA with increased expression of Jagged1, Notch-1, accumulation of the Notch intracellular domain 1 and increased transcription of Hes-1. Notch1 AS mice showed exacerbated OA with increases in OARSI scores, osteophyte formation, increased subchondral bone plate density, collagen X and osteocalcin expression and elevated levels of Epas1 and ADAM-TS5 mRNA. Inhibition of the Notch pathway induced activation of hedgehog signalling with induction of Gli-1 and Gli-2 and increased transcription of hedgehog target genes. The regulatory effects of Notch signalling on Gli-expression were mimicked by Hes-1.
  
  
  CONCLUSIONS
  Inhibition of Notch signalling activates hedgehog signalling, enhances chondrocyte hypertrophy and exacerbates experimental OA including osteophyte formation. These data suggest that the activation of the Notch pathway may limit aberrant hedgehog signalling in OA.
authors: Department of Internal Medicine III and Institute for Clinical Immunology, University of Erlangen-Nuremberg, Erlangen, Germany.
authors: Neng-Yu
authors: NY
authors: Lin
authors: Department of Internal Medicine III and Institute for Clinical Immunology, University of Erlangen-Nuremberg, Erlangen, Germany.
authors: Alfiya
authors: A
authors: Distler
authors: Department of Internal Medicine III and Institute for Clinical Immunology, University of Erlangen-Nuremberg, Erlangen, Germany.
authors: Christian
authors: C
authors: Beyer
authors: Department of Internal Medicine III and Institute for Clinical Immunology, University of Erlangen-Nuremberg, Erlangen, Germany.
authors: Ariella
authors: A
authors: Philipi-Schöbinger
authors: Department of Internal Medicine III and Institute for Clinical Immunology, University of Erlangen-Nuremberg, Erlangen, Germany Division of Rheumatology, University of Pavia, IRCCS Policlinico San Matteo Foundation, Pavia, Italy.
authors: Silvia
authors: S
authors: Breda
authors: Department of Internal Medicine III and Institute for Clinical Immunology, University of Erlangen-Nuremberg, Erlangen, Germany.
authors: Clara
authors: C
authors: Dees
authors: Department of Internal Medicine III and Institute for Clinical Immunology, University of Erlangen-Nuremberg, Erlangen, Germany.
authors: Michael
authors: M
authors: Stock
authors: Institute of Rheumatology and Department of Rheumatology, 1st Faculty of Medicine, Charles University, Prague, Czech Republic.
authors: Michal
authors: M
authors: Tomcik
authors: Department of Orthopedics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
authors: Andreas
authors: A
authors: Niemeier
authors: William Harvey Research Institute, Barts and The London, School of Medicine and Dentistry, Queen Mary, University of London, London, UK.
authors: Francesco
authors: F
authors: Dell'Accio
authors: Division of Trauma Surgery and Orthopedic Surgery, Department of Surgery, University of Erlangen-Nuremberg, Germany.
authors: Kolja
authors: K
authors: Gelse
authors: Laboratory of Neurosciences, National Institute on Aging Intramural Research Program, Baltimore, Maryland, USA.
authors: Mark P
authors: MP
authors: Mattson
authors: Department of Internal Medicine III and Institute for Clinical Immunology, University of Erlangen-Nuremberg, Erlangen, Germany.
authors: Georg
authors: G
authors: Schett
authors: Department of Internal Medicine III and Institute for Clinical Immunology, University of Erlangen-Nuremberg, Erlangen, Germany.
authors: Jörg Hw
authors: JH
authors: Distler
mesh_terms: D000818:Animals; D001169:Arthritis, Experimental / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism*; D002358:Cartilage, Articular / Q000378:metabolism; D019902:Chondrocytes / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000378:metabolism*; D051379:Mice; D008822:Mice, Transgenic; D010003:Osteoarthritis / Q000378:metabolism*; D054850:Osteophyte / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D051881:Receptor, Notch1 / Q000378:metabolism*; D012720:Severity of Illness Index; D015398:Signal Transduction; D000072056:Transcription Factor HES-1 / Q000378:metabolism*
chemical_list: D002352:Carrier Proteins; C489734:Hes1 protein, mouse; C498447:Hhip protein, mouse; D008562:Membrane Glycoproteins; C497762:Notch1 protein, mouse; D051881:Receptor, Notch1; D000072056:Transcription Factor HES-1
keywords: Chondrocytes; Knee Osteoarthritis; Osteoarthritis