Asiatic acid protects articular cartilage through promoting chondrogenesis and inhibiting inflammation and hypertrophy in osteoarthritis

Abstract

Natural small molecules have become attractive in osteoarthritis (OA) treatment. This study aims to investigate the effect of asiatic acid (AA) on OA development in vitro and in vivo. Chondrocytes were pretreated with AA at optimized concentrations and subsequently treated with interleukin-1 beta (IL-1β). Inflammatory mediator nitric oxide (NO) was measured by Griess method. The mRNA expression level of inflammatory markers nitric oxide synthase (iNOS) and cyclooxygenase 2 (Cox2), as well as chondrogenic or hypertrophic markers including SRY-box transcription factor 9 (Sox9), Aggrecan, Collagen 2a1 (Col II), and Matrix metalloproteinase-13 (Mmp13) were measured by using real-time PCR analysis. The nuclear factor-kappa B (NF-κB) signaling activity was determined by dual luciferase assay and Western blot analysis. Surgery-induced OA animal model was constructed, and AA was administrated to study its effect on OA pathogenesis. AA induced a dose-dependent inhibitory effect up to -67.4% on NO production. AA could repress iNOS and Cox2 protein expression levels (-77.2% and -73.4%, respectively) in IL-1β induced chondrocytes. AA increased the formation of cartilage extracellular matrix components including glycosaminoglycans (GAGs) and collagen type II. AA also mRNA expression of chondrogenesis marker including Aggrecan, Sox9, Col II and Fibronectin (402.87%, 151.04%, 314.15% and 187.76%, respectively) as well as hypertrophic marker Mmp13 (-67.8%). AA repressed the chondrocyte inflammation by directly inhibiting NF-κB signaling activity, which was revealed by the inhibition effect of AA on IκBα phosphorylation (-105.4%) and NF-κB/p65 translocation (-60.9%) induced by IL-1β. Furthermore, In vivo OA study indicated the protective effect of AA on OA progression by preventing articular cartilage from degeneration and destruction. AA treatment could significantly reduce OA score (16.125 vs 5.25) and repress mRNA expression level of Mmp13 and Col X (23.5, vs 2.375 and 18.125 vs 94.5). Taken together, our findings suggest that AA could effectively rescue IL-1β induced chondrocytes and protected cartilage in OA progression, which shed light on a potential novel therapeutic strategy of OA treatment.

Keywords: Asiatic acid; Chondrocytes; Inflammation; NF-κB signaling pathway; Osteoarthritis.