To validate RNA-Seq results, we conducted RT-PCR using ferret tissues for selected DEGs (Fig. 5) that were uniquely modeled in ferrets, in addition to CYP1B1 as an exposure control, MMP12 as an important gene associated with COPD progression, and HAS1 as a disease of interest related to mucosal defense. This evidence concerns the gene MMP12 and chronic obstructive pulmonary disease.