Safranine O staining
Chondrocytes were incubated with different concentrations (0, 1, and 5 μM) of empagliflozin with or without IL-1β (10 ng/ml) for 24 h. Then the cells were fixed with 4% paraformaldehyde (PFA) solution for 20 min. After washing with PBS, 0.1% Safranine O dye solution were added to stain the cells for 5 min. After washing with PBS twice, cells were imaged by gross camera.