title: The peroxisome proliferator-activated receptor gamma agonist pioglitazone reduces the development of cartilage lesions in an experimental dog model of osteoarthritis: in vivo protective effects mediated through the inhibition of key signaling and catabolic pathways.
abstract: OBJECTIVE
  Emerging evidence indicates that peroxisome proliferator-activated receptor gamma (PPARgamma) may have protective effects in osteoarthritis (OA). The aim of this study was to evaluate the in vivo effect of a PPARgamma agonist, pioglitazone, on the development of lesions in a canine model of OA, and to explore the influence of pioglitazone on the major signaling and metabolic pathways involved in OA pathophysiologic changes.
  
  
  METHODS
  OA was surgically induced in dogs by sectioning of the anterior cruciate ligament. The dogs were then randomly divided into 3 treatment groups in which they were administered either placebo, 15 mg/day pioglitazone, or 30 mg/day pioglitazone orally for 8 weeks. Following treatment, the severity of cartilage lesions was scored. Cartilage specimens were processed for histologic and immunohistochemical evaluations; specific antibodies were used to study the levels of matrix metalloproteinase 1 (MMP-1), ADAMTS-5, and inducible nitric oxide synthase (iNOS), as well as phosphorylated MAPKs ERK-1/2, p38, JNK, and NF-kappaB p65.
  
  
  RESULTS
  Pioglitazone reduced the development of cartilage lesions in a dose-dependent manner, with the highest dosage producing a statistically significant change (P < 0.05). This decrease in lesions correlated with lower cartilage histologic scores. In addition, pioglitazone significantly reduced the synthesis of the key OA mediators MMP-1, ADAMTS-5, and iNOS and, at the same time, inhibited the activation of the signaling pathways for MAPKs ERK-1/2, p38, and NF-kappaB.
  
  
  CONCLUSIONS
  These results indicate the efficacy of pioglitazone in reducing cartilage lesions in vivo. The results also provide new and interesting insights into a therapeutic intervention for OA in which PPARgamma activation can inhibit major signaling pathways of inflammation and reduce the synthesis of cartilage catabolic factors responsible for articular cartilage degradation.
authors.affiliation: University of Montreal Hospital Centre, Notre-Dame Hospital, Montreal, Quebec, Canada.
authors.forename: Christelle
authors.initials: C
authors.lastname: Boileau
authors.forename: Johanne
authors.initials: J
authors.lastname: Martel-Pelletier
authors.forename: Hassan
authors.initials: H
authors.lastname: Fahmi
authors.forename: François
authors.initials: F
authors.lastname: Mineau
authors.forename: Martin
authors.initials: M
authors.lastname: Boily
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Pelletier
mesh_terms: D000818:Animals; D002356:Cartilage / Q000187:drug effects / Q000473:pathology*; D004195:Disease Models, Animal; D004285:Dogs; D005269:Femur; D007004:Hypoglycemic Agents / Q000627:therapeutic use; D010003:Osteoarthritis / Q000188:drug therapy / Q000473:pathology*; D047495:PPAR gamma / Q000819:agonists*; D000077205:Pioglitazone; D045162:Thiazolidinediones / Q000627:therapeutic use*; D013977:Tibia
chemical_list: D007004:Hypoglycemic Agents; D047495:PPAR gamma; D045162:Thiazolidinediones; D000077205:Pioglitazone