E. Representative TEM images of RCS chondrocytes treated with 5% ABS (vehicle) and FGF18 (50 ng/mL) for 16 hours. BafA1 (100 nM; 4 hours) was used to inhibit lysosome activity. Arrows indicate lysosomes. Higher magnification insets showed presence of ER membranes decorated with ribosomes (arrowheads). Scale bar 500nm. Quantification shows average number of ER membranes and mitochondria number/ lysosome vesicle (Lys). Mean +/- standard error of the mean (sem) of N=3 biological replicates/treatment. ER fragment/vesicle n=60 (vehicle) and n=72 (FGF18) cells were analyzed; Mitochondria number/vesicle: n=40 (vehicle) and n=72 (FGF18) cells were analyzed. Student paired T-Test ***p<0.0005; NS not significant. 