Antioxidant activity of decorin purified from the serum of osteoarthritis patients

Background: Osteoarthritis (OA) is a chronic degenerative joint disease characterized by cartilage loss, pain, inflammation and limited mobility. Leucine-rich small proteoglycans, specifically decorin (DCN), play a vital role in maintaining the integrity of cartilage and the extracellular matrix. Recent research reveals new dimensions to DCN’s role beyond structural regulation, highlighting its antioxidant and free radical scavenging properties. The relationship between DCN level and activity, and oxidative status within a degene­rative joint needs further elucidation. Objective: This study aimed to purify DCN from the serum of OA patients and healthy individuals and to determine the antioxidant activity of the purified samples. Methods: Decorin isolation and fractionation included: 65% ammonium sulfate precipitation, dialysis, size-exclusion chromatography using Sephadex G-75 and confirmation of DCN purity by RP-HPLC. The antioxidant efficacy of the purified protein was evaluated with the DPPH radical-scavenging method. Results: Molecular weight analyses using gel electrophoresis and HPLC confirmed high purity and a molecular weight of 45 kDa for both purified samples. DCN extracted from the serum of OA patients exhibited higher antioxidant activity (IC50 = 0.380 ng/ml) than DCN extracted from healthy controls (IC50 = 0.790 ng/ml) or than standard vitamin C (IC50 = 0.765 ng/ml). Conclusions: The results obtained indicate that purified DCN possesses antioxidant capability, which is stimulated in the inflammatory microenvironment of the affected joint in osteoarthritis.