Expression of Akt and ERK1/2 in human osteoarthritic chondrocytes

AIM: To investigate the expression of protein kinase B (Akt) and extracellular signal-regulated kinase 1/2 (ERK1/2) in normal and osteoarthritic chondrocytes. METHODS: The samples of knee cartilage were obtained from the normal donors (n=5) and the patients (n=18) undergoing total knee arthroplasty with the diagnosis of osteoarthritis (OA). The expression of p-Akt and p- ERK1/2 in the normal and osteoarthritic cartilage tissues was detected by the method of immunohistochemistry. The chondrocytes were isolated and identified by toluidine blue staining and immunohistochemical method. The expression levels of Akt, p-Akt, ERK1/2,p-ERK1/2,phosphorylated 70-kD ribosomal protein S6 kinase(p-p70S6K) and proliferating cell nuclear antigen(PCNA) were tested in normal and osteoarthritic chondrocytes by Western blotting. Real-time fluorescence quantitative PCR was used to measured the expression levels of aggrecan and type II collagen gene in normal and osteoarthritic chondrocytes. RESULTS: The expression of p-Akt in normal cartilage was higher than that in OA cartilage. The expression of p- ERK1/2 in OA cartilage was higher than that in normal cartilage. Compared with the normal chondrocytes, the expression of p-Akt and p-p70S6K, and the mRNA levels of aggrecan and type II collagen were increased (P<0.05), and the expression of p-ERK1/2 and PCNA was decreased in OA chondrocytes (P<0.05). CONCLUSION: Akt might regulate aggrecan and type II collagen synthesis via p-p70S6K, and ERK1/2 might regulate OA chondrocyte proliferation through PCNA. Both Akt and ERK1/2 play important roles in the pathogenesis of OA.