Airway epithelial dysfunction and mesenchymal transition in chronic obstructive pulmonary disease: Role of Oct-4

The airway epithelium is a dynamic tissue that undergoes slow but constant renewal. Dysregulation of airwayepithelial function related to cigarette smoke exposure plays an important role in the pathophysiology of COPD.Oct4 is a transcription factor responsible for maintaining cellular self-renewal and regeneration, and CD146 andCD105/Endoglin are adhesion molecules involved in cell proliferation, differentiation, epithelial-mesenchymaltransitionand tissue remodeling. Bronchial biopsy specimens (BBs) were obtained from 7 healthy controls (HC)and 10 COPD and subjected to paraffin embedding; BBs from HC were also used for epithelial cell expansion andpHBEC/ALI (air-liquid interface) culture. pHBEC/ALI were exposed to cigarette smoke extract (CSE) for 7, 14and 21 days. In BBs, Oct4, CD146 and CD105 were evaluated by immunohistochemistry. In pHBEC/ALI, theexpression of Oct4, CD146, CD105 and acetyl-αtubulin was evaluated by Western Blot, MUC5AC and IL-8measurements by ELISA.The Oct4 epithelial immunoreactivity was lower in COPD than in HC, whilst CD146 and CD105 expression washigher in COPD than in HC. In pHBEC/ALI, Transepithelial Electrical Resistance values, measured over 7 to 21days of differentiation, decreased by 18% (2.5% CSE) and 29% (5% CSE) compared to untreated samples. Oct4and acetyl-αtubulin were induced after one-week differentiation and downregulated by CSE in reconstitutedepithelium; CD146, CD105, MUC5AC and IL-8 were increased by CSE.Oct4 de-regulation and CD146 and CD105 overexpression, induced by cigarette smoke exposure, might play arole in airway epithelial dysfunction by causing changes in self-renewal and mesenchymal transition mechanisms,leading to alteration of epithelium homeostasis and abnormal tissue remodeling involved in progression ofCOPD.