No description available.

No description available.

No description available.

Arthritis includes many conditions of the joints characterized by inflammation, pain, and loss of joint function that affect 66 million people in the U.S. alone. During arthritic degeneration, chondrocytes exhibit downregulated synthesis of extracellular matrix molecules and upregulation of proteolytic enzymes. Fibrochondrocytes, found in meniscal fibrocartilage, appear to behave in a similar way. Metalloproteinases, including matrix metalloproteinases (MMP) and a disintegrin and metollproteinase with thrombospondin motif (ADAMTS) class enzymes have demonstrated efficient, distinct aggrecan degradation in models of arthritis. ADAMTS-4 and ADAMTS-5 are thought to be primary mediators of pathologic aggrecan catabolism, while MMP-17 may be involved in ADAMTS activation. There is also growing evidence of metalloproteinase-independent mechanisms in aggrecan catabolism. The cysteine endopeptidase m-calpain has been detected in cartilage from arthritic joints, and chondrocytes can secrete this protease. The overall objective of this work was to investigate metalloproteinases and m-calpain as comediators of aggrecan turnover in articular cartilage and meniscal fibrocartilage. The central hypothesis was that metalloproteinases cooperate with m-calpain to mediate cytokine-induced aggrecan turnover and associated changes in tissue mechanics. Experiments involved using inhibitors to perturb protease systems, antibodies targeting aggrecan neoepitopes to characterize enzyme activity, and established methods of evaluating tissue compressive and shear properties. Models of degradation and de novo tissue assembly were used to investigate tissue-specific differences in aggrecan turnover. The results of this work demonstrate tissue-specific differences in the abundance and structure of aggrecan, and indicate that the mechanisms and extent of aggrecan processing in the meniscus is dependent on location within the tissue. The relationships between aggrecan structure and tissue material properties are discussed, along with implications for development, disease, and repair.

Introduction: Le principal objectif de cette étude est de mesurer l’effet du GDF-5 sur l’homéostasie du cartilage. Le GDF-5 est un gène de susceptibilité de l’OA faisant partie de la famille des BMPs et qui favorise la synthèse du cartilage. Le but de notre étude a été de déterminer l’effet du GDF-5 sur le métabolisme catabolique ainsi que sur l’équilibre global des chondrocytes, principalement au niveau de l’Aggrécan. Méthode : Des chondrocytes arthrosiques canins et humains OA ont été exposés au GDF-5. L’expression des ARNm et des protéines a été analysée afin d’évaluer la production de l’Aggrécan et le ratio Col-II/Col-I au niveau des facteurs anaboliques et du phénotype. Pour le catabolisme, l’expression et l’activité des aggrécanases ADAMTS-4 et ADAMTS-5 ont été mesurées. Les épitopes NITEGE et CTX-II ont aussi été quantifiés dans le liquide synovial canin après des injections intraarticulaires de GDF-5. Résultats : Le GDF-5 provoque une augmentation de l’activité cellulaire des chondrocytes canins et humains. Pour les ARNm et l’expression protéique, le GDF-5 augmente l’expression de l’Aggrécan alors que les facteurs cataboliques le diminuent. Le phénotype reste inchangé en présence du produit, sauf à haute dose où on augmente le ColI. L’activité des aggrécanases diminue puisque l’épitope NITEGE diminue alors que le CTX-II augmente dans l’articulation. Conclusion : En somme, les facteurs anaboliques du cartilage sont favorisés, alors que les facteurs cataboliques sont diminués par le GDF-5. Cette action double permet d’illustrer l’effet du GDF-5, le classant comme un potentiel médicament modifiant la maladie de l’OA qui mérite d’être étudiée. / Purpose: The objective of this study is to assess the effect of GDF-5 on cartilage homeostasis. GDF-5 is a susceptibility gene for OA and member of the BMP super family. Studies have shown that it can increase expression of anabolic factors in chondrocytes. Therefore, our study indentifies how GDF-5 influences this metabolism and the global homeostasis of chondrocytes, aiming mainly towards Aggrecan. Methods : Osteoarthritic (OA) chondrocytes from canine and human models were exposed to GDF-5. Protein expressions, along with mRNA expression were assessed in order to investigate Aggrecan production and the ratio of Col-II/Col-I, for the anabolic phenotype markers. The aggrecanases ADAMTS-4 and ADAMTS-5 and their global activity were assed for the catabolic factors. The NITEGE and CTX-II epitope were also measured in synovial fluid of Pond-Nuki dogs that received intraarticular GDF-5 injections. Results : GDF-5 increases chondrocyte cellular activity, in our canine and human models. Both mRNA and protein expression of the chondrocytes Aggrecan were increased and the aggrecanases expression and activity were decreased. Collagen ratio did not show a phenotype, except et high dosage where the Col-I production is induced. Aggrecanase activity was lowered while CTX-II was increased. Conclusion : In conclusion, the anabolic cellular activity of OA chondrocytes increases while the catabolic factors decrease in presence of GDF-5. This double action illustrates the global effect of GDF-5, identifying it as a potential disease modifying factor of OA that should be further investigated.

Introduction: Le principal objectif de cette étude est de mesurer l’effet du GDF-5 sur l’homéostasie du cartilage. Le GDF-5 est un gène de susceptibilité de l’OA faisant partie de la famille des BMPs et qui favorise la synthèse du cartilage. Le but de notre étude a été de déterminer l’effet du GDF-5 sur le métabolisme catabolique ainsi que sur l’équilibre global des chondrocytes, principalement au niveau de l’Aggrécan. Méthode : Des chondrocytes arthrosiques canins et humains OA ont été exposés au GDF-5. L’expression des ARNm et des protéines a été analysée afin d’évaluer la production de l’Aggrécan et le ratio Col-II/Col-I au niveau des facteurs anaboliques et du phénotype. Pour le catabolisme, l’expression et l’activité des aggrécanases ADAMTS-4 et ADAMTS-5 ont été mesurées. Les épitopes NITEGE et CTX-II ont aussi été quantifiés dans le liquide synovial canin après des injections intraarticulaires de GDF-5. Résultats : Le GDF-5 provoque une augmentation de l’activité cellulaire des chondrocytes canins et humains. Pour les ARNm et l’expression protéique, le GDF-5 augmente l’expression de l’Aggrécan alors que les facteurs cataboliques le diminuent. Le phénotype reste inchangé en présence du produit, sauf à haute dose où on augmente le ColI. L’activité des aggrécanases diminue puisque l’épitope NITEGE diminue alors que le CTX-II augmente dans l’articulation. Conclusion : En somme, les facteurs anaboliques du cartilage sont favorisés, alors que les facteurs cataboliques sont diminués par le GDF-5. Cette action double permet d’illustrer l’effet du GDF-5, le classant comme un potentiel médicament modifiant la maladie de l’OA qui mérite d’être étudiée. / Purpose: The objective of this study is to assess the effect of GDF-5 on cartilage homeostasis. GDF-5 is a susceptibility gene for OA and member of the BMP super family. Studies have shown that it can increase expression of anabolic factors in chondrocytes. Therefore, our study indentifies how GDF-5 influences this metabolism and the global homeostasis of chondrocytes, aiming mainly towards Aggrecan. Methods : Osteoarthritic (OA) chondrocytes from canine and human models were exposed to GDF-5. Protein expressions, along with mRNA expression were assessed in order to investigate Aggrecan production and the ratio of Col-II/Col-I, for the anabolic phenotype markers. The aggrecanases ADAMTS-4 and ADAMTS-5 and their global activity were assed for the catabolic factors. The NITEGE and CTX-II epitope were also measured in synovial fluid of Pond-Nuki dogs that received intraarticular GDF-5 injections. Results : GDF-5 increases chondrocyte cellular activity, in our canine and human models. Both mRNA and protein expression of the chondrocytes Aggrecan were increased and the aggrecanases expression and activity were decreased. Collagen ratio did not show a phenotype, except et high dosage where the Col-I production is induced. Aggrecanase activity was lowered while CTX-II was increased. Conclusion : In conclusion, the anabolic cellular activity of OA chondrocytes increases while the catabolic factors decrease in presence of GDF-5. This double action illustrates the global effect of GDF-5, identifying it as a potential disease modifying factor of OA that should be further investigated.