ELISA
The levels of MMP9, MMP13, PGE2 and IL-6 were measured using ELISA kits (AdipoGen LIFE SCIENCES, Germany). Chondrocytes were incubated with IL-1β (10 ng/ml) for 24 h before pretreatment for 2 h with empagliflozin at various concentrations (0, 1, and 5 μM). The levels of MMP9, MMP13, PGE2 and IL-6 were detected by collecting the cell culture supernatants from each sample with ELISA kits according to the manufacturer. The relative levels were normalized to cell count.