Tenascin-C (TN-C) is expressed in the cartilage of osteoarthritis (OA). We examined whether TN-C was involved in cartilage repair of the diseased joints. Human articular cartilage samples were obtained from patients with OA and those with normal joints.
Immunohistochemistry testing of TN-C, chondroitin sulfate (CS), and proliferating cell nuclear antigen (PCNA) was performed. Chondrocytes were isolated from human cartilage and cultured. After treatment with TN-C, chondrocyte proliferation s was analyzed by bromodeoxyuridine (BrdU) incorporation assay using an enzyme-linked immunosorbent assay kit. Glycosaminoglycan content was determined by dimethylmethylene blue (DMMB) assay. The mRNA expression of aggrecan was also analyzed, by quantitative real-time polymerase chain reaction (PCR).
In osteoarthritic cartilage, increased TN-C staining was observed with the degeneration of articular cartilage in comparison with normal cartilage. TN-C staining was shown in the cartilage surface overlying CS-positive areas. In addition, the expression of PCNA in the positive areas for TN-C was significantly higher than that in the negative areas. Treatment of human articular chondrocytes with 10 μg/ml TN-C accelerated chondrocyte proliferation, increased the proteoglycan amount in culture, and increased the expression of aggrecan mRNA.
Our findings indicate that the distribution of TN-C is related to CS production and chondrocyte proliferation in osteoarthritic cartilage and that TN-C has effects on DNA synthesis, proteoglycan content, and aggrecan mRNA expression in vitro. TN-C may be responsible for repair in human osteoarthritic cartilage.