Abstract: Abstract Objectives The expression of proteins and genes of Wnt/β-catenin signaling in the articular cartilage of human OA samples from patients undergoing total knee arthroplasty.Methods Knee joint samples were dissected and embeded in paraffin. The tissue sections were stained with HE , Safranin O / Fast Green (SO/FG) and Alcian blue / orange G(AB/OG),and graded using a modified version of the Mankin scale. Immunohistochemistry staining of β-catenin and MMP-13 were performed in all samples. Total RNA extracted from articular cartilage tissue was prepared using Trizol according to the manufacture’s protocol. Real time RT-PCR was performed to test BMP-2, COL-10 and MMP-13 expression. Results 1.All samples were studied and the distribution of averaged grades allowed for stratification of human samples into three groups :control ,mild OA and moderate OA. 2.Immunohistochemistry of all samples showed a significant up-regulation of β-catenin and MMP-13 in both the mild and moderate groups compared with the normal control.3.Expression of chondrocyte marker genes such as BMP-2, COL-10 and MMP-13 were significantly increased in moderate OA group. Conclusions 1.The protein level of β-catenin and MMP-13 was increased in OA patients.2.Expression of chondrocyte maturation marker genes, such as BMP-2, COL-10, and MMP-13 were significantly increased in articular cartilage of OA patients. 3.Overexpression of β-catenin in articular chondrocytes leads to premature chondrocytes differentiation and the development of OA. These results establish a strong association between human OA and β-catenin expression.

Key words: osteoarthritis, articular chondrocytes, β-catenin, bone morphogenetic protein -2, type X collagen, matrix metalloproteinase-13