title: Reduction in disease progression by inhibition of transforming growth factor α-CCL2 signaling in experimental posttraumatic osteoarthritis.
abstract: OBJECTIVE
  Transforming growth factor α (TGFα) is increased in osteoarthritic (OA) cartilage in rats and humans and modifies chondrocyte phenotype. CCL2 is increased in OA cartilage and stimulates proteoglycan loss. This study was undertaken to test whether TGFα and CCL2 cooperate to promote cartilage degradation and whether inhibiting either reduces disease progression in a rat model of posttraumatic OA.
  
  
  METHODS
  Microarray analysis was used to profile expression of messenger RNA (mRNA) for Tgfa, Ccl2, and related genes in a rat model of posttraumatic OA. Rat primary chondrocytes and articular cartilage explants were treated with TGFα in the presence or absence of MEK-1/2, p38, phosphatidylinositol 3-kinase, Rho-associated protein kinase, or CCR2 inhibitors and immunostained for markers of cartilage degradation. The rat model was used to administer pharmacologic inhibitors of TGFα (AG1478) and CCL2 (RS504393) signaling for up to 10 weeks and assess histopathology and serum biomarkers of cartilage synthesis (C-propeptide of type II collagen [CPII]) and breakdown (C2C).
  
  
  RESULTS
  Tgfa and Ccl2 mRNA were simultaneously up-regulated in articular cartilage in the rat model of posttraumatic OA. TGFα induced expression of CCL2, Mmp3, and Tnf in primary chondrocytes. Cleavage of type II collagen and aggrecan (by matrix metalloproteinases and ADAMTS-4/5, respectively) induced by TGFα was blocked by pharmacologic inhibition of CCL2 in cartilage explants. In vivo pharmacologic inhibition of TGFα or CCL2 signaling reduced Osteoarthritis Research Society International cartilage histopathology scores and increased serum CPII levels, but only TGFα inhibition reduced C2C levels intreated versus untreated rat OA cartilage.
  
  
  CONCLUSIONS
  TGFα signaling stimulates cartilage degradation via a CCL2-dependent mechanism, but pharmacologic inhibition of the TGFα-CCL2 axis reduces experimental posttraumatic OA progression in vivo.
authors.affiliation: Western University Schulich School of Medicine and Dentistry, London, Ontario, Canada.
authors.forename: C Thomas G
authors.initials: CT
authors.lastname: Appleton
authors.affiliation: Western University Schulich School of Medicine and Dentistry, London, Ontario, Canada.
authors.forename: Shirine E
authors.initials: SE
authors.lastname: Usmani
authors.affiliation: Western University Schulich School of Medicine and Dentistry, London, Ontario, Canada.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Pest
authors.affiliation: Western University Schulich School of Medicine and Dentistry, London, Ontario, Canada.
authors.forename: Vasek
authors.initials: V
authors.lastname: Pitelka
authors.affiliation: Shriners Hospitals for Children-Canada and McGill University, Montreal, Quebec, Canada.
authors.forename: John S
authors.initials: JS
authors.lastname: Mort
authors.affiliation: Western University Schulich School of Medicine and Dentistry and Children's Health Research Institute, London, Ontario, Canada.
authors.forename: Frank
authors.initials: F
authors.lastname: Beier
mesh_terms: D000818:Animals; D048588:Benzoxazines / Q000494:pharmacology; D002358:Cartilage, Articular / Q000473:pathology / Q000503:physiopathology; D018932:Chemokine CCL2 / Q000037:antagonists & inhibitors* / Q000187:drug effects / Q000502:physiology; D004195:Disease Models, Animal; D018450:Disease Progression; D008297:Male; D010003:Osteoarthritis / Q000209:etiology / Q000503:physiopathology* / Q000517:prevention & control*; D011799:Quinazolines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D013141:Spiro Compounds / Q000494:pharmacology; D016211:Transforming Growth Factor alpha / Q000037:antagonists & inhibitors / Q000187:drug effects / Q000502:physiology; D020032:Tyrphostins / Q000494:pharmacology; D015854:Up-Regulation / Q000502:physiology; D014947:Wounds and Injuries / Q000150:complications*
chemical_list: D048588:Benzoxazines; C491766:Ccl2 protein, rat; D018932:Chemokine CCL2; D011799:Quinazolines; C579117:RS 504393; D013141:Spiro Compounds; D016211:Transforming Growth Factor alpha; D020032:Tyrphostins; C101044:RTKI cpd