Glutathione has cell protective and anti-catabolic effects in articular cartilage without impairing the chondroanabolic phenotype

Abstract

Joint injuries and consequent oxidative stress is a high-risk factor for developing post-traumatic osteoarthritis (OA). While antioxidative therapy using N-acetylcysteine (NAC) has cell- and chondroprotective effects following cartilage injury, it strongly impairs matrix synthesis. Consequently, direct application of Glutathione (GSH) was tested as an alternative therapeutic approach using an ex vivo cartilage trauma model and isolated chondrocytes, with comparison to NAC.Porcine cartilage explants were traumatized using a drop tower with an impact energy of 0.47 J and afterwards treated with 0.5–2 mM GSH or 2 mM NAC for 4 days according to a standardized protocol. The effects of antioxidative treatment on the chondrogenic phenotype were tested in a 3D pellet culture for 28 days. Our results demonstrated that both antioxidants had cell protective effects after cartilage trauma. GSH was most effective at a concentration of 0.5 mM, as confirmed in experiments with isolated human chondrocytes exposed to H2O2. At this concentration, GSH did not impair cell proliferation or hyaline cartilage matrix synthesis, while NAC suppressed the chondrogenic phenotype in pellet culture. Both, NAC and GSH elevated the intracellular GSH concentration, indicating an efficient uptake of the antioxidants. Furthermore, both therapeutics inhibited the activity of the matrix degrading enzyme MMP-2.Our results demonstrated cell- and chondroprotective effects by NAC and GSH therapy after cartilage trauma, with GSH demonstrating advantages in preserving the chondrogenic phenotype.