F. Representative co-immunofluorescence staining of ER (ER tracker BODIPY green) and lysosomes (Lamp1, red) in RCS chondrocytes treated with vehicle (5% ABS) and FGF18 (50 ng/mL) for 16 hours. Insets show higher magnification of boxed area. Scale bar 15 μm and 2 μm (higher magnification boxes). N=3 biological replicates/treatment. 