Abstract
Background: Osteoarthritis (OA) is epidemic in the elderly people as a common chronic joint disease. By now, drug and surgical treatments are two main therapies for OA worldwidely. Baicalin (BA) is a flavonoid monomer extracted from Scutellaria baicalensis Georgi and is reported that BA has anti-inflammatory, anti-deformation and anti-bacterial effects. Methods: Micromass culture, alcian blue and Safran O (SO)/fast green staining were used to investigate chondrocyte viability and ECM synthesis in chondrocytes of all groups. The expression of SOX9 and Smad3 in chondrocytes of all groups were detected by western blot and RT-qPCR, the expression of aggrecan (AGG), type II collagen (Col2α), MMP9/13 and ADAMTS5 were detected by RT-qPCR. In current study, we demonstrated that BA neutralized the down-regulation of chondrocyte viability and extracellular matrix (ECM) secretion, including AGG and Col2α, induced by IL-1β. As the key regulators of ECM, the down-regulation of SOX9, and the up-regulation of MMP9/13 and ADAMTS5 induced by IL-1β were abolished by BA. Moreover, BA increased the nuclear translocation and phosphorylation of Smad3, one key mediator of TGF-β/Smads pathway. Interestingly, the addition of Smad3 inhibitor SIS3 reversed the promotions of BA on chondrocyte viability, ECM secretion, SOX9 expression, Smad3 nuclear translocation and Smad3 phosphorylation, and the down-regulation of BA on the expressions of MMP9/13 and ADAMTS5. Conclusions: These results imply that BA can protect chondrocytes against IL-1β-induced inflammatory injury through the acceleration of Smad3 phosphorylation and nuclear translocation in chondrocytes. This study demonstrates that BA may be a potential drug for OA clinical treatment.