ACTA1 and chronic obstructive pulmonary disease: The lung epithelium of COPD patients and smokers has upregulated mesenchymal markers, such as α-SMA, vimentin, and collagen type 1, and downregulated epithelial markers (e.g., ZO-1, E-cadherin) compared to that of non-COPD non-smokers, likely due to cell turnover from repeated cycles of tissue injury and repair due to inflammation and oxidative stress (Figure 3C) [95,96].