Previous studies have shown that occludin, ZO-1, and E-cadherin expression in bronchial epithelial cells and lung tissue sections from patients with COPD is lower than that in healthy individuals (Heijink et al., 2014; Nishida et al., 2017; Aghapour et al., 2018). The gene discussed is OCLN; the disease is chronic obstructive pulmonary disease.