Fig. 5. Retinoic acid increases lipid accumulation in lung fibroblasts. (A) Lung fibroblasts cultured for 1 week to deplete endogenous lipid droplets were exposed to fatty-acid complexes (0.1 µM) and retinoic acid (RA; 1 µM) for 1 week, stained with Nile Red and analyzed by flow cytometry. The shift in mean fluorescence intensity following fatty acid (FA) and RA treatment indicates increased Nile-Red staining and, hence, increased cellular lipids. (B) Graph of mean fluorescence intensities normalized to the average mean fluorescence intensity of untreated samples. The mean ± s.d. from triplicate samples are shown. Asterisks indicate statistically significant (P<0.01) pair wise comparisons between FA treated and untreated samples (^*) and between RA treated and untreated samples (^**).