Figure 4. Exosomes derived from cigarette smoke (CS)-exposed epithelial cells contain high levels of miR-221-3p, which are transferred to macrophages. (A, B) qRT-PCR determination of miR-221-3p levels in exosomes from epithelial cells under cigarette conditions. (C, D) qRT-PCR determination of miR-221-3p levels in exosomes from epithelial cells grown under cigarette conditions following transfection with hnRNPA1 siRNAs. (E, F) qRT-PCR determination of miR-221-3p levels in macrophages grown in epithelial cells under cigarette conditions subjected to ultracentrifugation to deplete exosomes (exo-free supernatant). Data are shown as the mean ± SEM (n = 3–5 replicates). *P < 0.05; **P < 0.01; *** P < 0.001; ****P < 0.0001.