Comparative analysis of sodium coupled vitamin C transporter 2 in human osteoarthritis grade 1 and grade 3 tissues

Nutrient levels are known to influence the development of osteoarthritis (OA), presumably by modulating levels of matrix biosynthesis and degradation. These processes may be affected by ascorbic acid (AA), an antioxidant which acts as a cofactor for numerous biochemical reactions and is essential for post-translational modifications of collagen. In this study we examined the expression of SVCT2, the only known Sodium coupled vitamin C transporter isoform present in articular cartilage, in human articular cartilage explants derived from both normal and osteoarthritis articular cartilage.

OA1 and OA3 human articular cartilage was carefully dissected and macroscopically graded for degeneration via the Collins scale. The tissue samples were histologically examined by Hematoxylin and Eosin and Safranin O and Fast Green staining. SVCT2 expression analysis was performed at mRNA level by quantitative real time PCR and at a protein level by immunohistochemistry.

Our quantitative real time PCR showed marked variation in the expression of SVCT2 in human osteoarthritic articular cartilage. SVCT2 expression was significantly down-regulated (p = 0.0001) in the Collins grade 3 (OA3) compared to Collins grade 1 (OA1) tissue. Furthermore, slides stained with fluorescent antibodies to SVCT2 demonstrated greatly reduced fluorescence for the SVCT2 transporter on the chondrocyte plasma membrane in the osteoarthritic tissue samples.

These findings demonstrate that the expression of SVCT2 transporter is significantly altered in human osteoarthritic tissues (OA3). The modulation of this transporter could therefore potentially influence the prevention, management and treatment of osteoarthritis.