Superoxide dismutase downregulation in osteoarthritis progression and end-stage disease.
BACKGROUND
Oxidative stress is proposed as an important factor in osteoarthritis (OA).


OBJECTIVE
To investigate the expression of the three superoxide dismutase (SOD) antioxidant enzymes in OA.


METHODS
SOD expression was determined by real-time PCR and immunohistochemistry using human femoral head cartilage. SOD2 expression in Dunkin-Hartley guinea pig knee articular cartilage was determined by immunohistochemistry. The DNA methylation status of the SOD2 promoter was determined using bisulphite sequencing. RNA interference was used to determine the consequence of SOD2 depletion on the levels of reactive oxygen species (ROS) using MitoSOX and collagenases, matrix metalloproteinase 1 (MMP-1) and MMP-13, gene expression.


RESULTS
All three SOD were abundantly expressed in human cartilage but were markedly downregulated in end-stage OA cartilage, especially SOD2. In the Dunkin-Hartley guinea pig spontaneous OA model, SOD2 expression was decreased in the medial tibial condyle cartilage before, and after, the development of OA-like lesions. The SOD2 promoter had significant DNA methylation alterations in OA cartilage. Depletion of SOD2 in chondrocytes increased ROS but decreased collagenase expression.


CONCLUSIONS
This is the first comprehensive expression profile of all SOD genes in cartilage and, importantly, using an animal model, it has been shown that a reduction in SOD2 is associated with the earliest stages of OA. A decrease in SOD2 was found to be associated with an increase in ROS but a reduction of collagenase gene expression, demonstrating the complexities of ROS function.
Scott
Jenny L
JL
Musculoskeletal Research Group, Institute of Cellular Medicine, Newcastle University, Newcastle-upon-Tyne, UK.
Gabrielides
Christos
C
Davidson
Rose K
RK
Swingler
Tracey E
TE
Clark
Ian M
IM
Wallis
Gillian A
GA
Boot-Handford
Raymond P
RP
Kirkwood
Tom B L
TB
Taylor
Robert W
RW
Talyor
Robert W
RW
Young
David A
DA
D000818:Animals; D001169:Arthritis, Experimental / Q000201:enzymology*; D001483:Base Sequence; D002358:Cartilage, Articular / Q000201:enzymology; D002478:Cells, Cultured; D019902:Chondrocytes / Q000201:enzymology; D019175:DNA Methylation; D018450:Disease Progression; D015536:Down-Regulation; D005272:Femur Neck / Q000201:enzymology; D015971:Gene Expression Regulation, Enzymologic; D006168:Guinea Pigs; D006801:Humans; D008297:Male; D020781:Matrix Metalloproteinase 1 / Q000096:biosynthesis; D053509:Matrix Metalloproteinase 13 / Q000096:biosynthesis; D008969:Molecular Sequence Data; D015207:Osteoarthritis, Hip / Q000201:enzymology*; D011401:Promoter Regions, Genetic; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D013482:Superoxide Dismutase / Q000096:biosynthesis* / Q000172:deficiency / Q000235:genetics; D000099156:Superoxide Dismutase 2
D020781:Matrix Metalloproteinase 1; D053509:Matrix Metalloproteinase 13; D013482:Superoxide Dismutase; D000099156:Superoxide Dismutase 2