Abstract
BackgroundNutrient 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.MethodsOA1 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.ResultsOur 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.ConclusionsThese 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.
Highlights
Nutrient levels are known to influence the development of osteoarthritis (OA), presumably by modulating levels of matrix biosynthesis and degradation
We hypothesize that the Sodium-dependent vitamin C transporters (SVCT2) transporter plays a key role in the normal function of articular chondrocytes, and that alteration in SVCT2 expression may contribute to cartilage degeneration
The present study examined the expression of SVCT2 in human articular chondrocytes derived from osteoarthritis grade 1 (OA1) and osteoarthritis grade 3 (OA3) at mRNA level by quantitative real time PCR and at protein level by immunohistochemistry
Summary
Patient samples Osteoarthritis grade 1 (OA1) and Osteoarthritis grade 3 (OA3) human cartilage was obtained from distal, anterior, and posterior femoral cuts from the knee joints of 29 tissue donors (13 males and 16 females) undergoing total knee arthroplasty procedures. The cartilage tissue was obtained from the operating room at the time of surgery, transported to the laboratory, washed with PBS, and immediately macroscopically graded for degeneration via the Collins scale. Following macroscopic grading, this tissue was assigned into one of two groups, OA1 (Collins grade 1) or OA3 (Collins grade 3–4) [8]. The groups (OA1 and OA3) were derived from a single knee of a single patient This graded cartilage tissue was dissected from the remnant joint tissue using a scalpel, with care taken to avoid underlying bone or tissue from osteophytes. A one-sample t-test was used to determine whether the mean ΔΔCt for SVCT2 was significantly different than zero
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