Verteporfin, an inhibitor of nuclear YAP, improved multi-ciliated cell differentiation in the airway epithelium.

BACKGROUND

Impaired multi-ciliated cell (MCC) differentiation, observed in various airway diseases, causes prolonged inflammation and further airway complications due to malfunction of the airway defense mechanism. YAP/TAZ-TEAD signaling mediates multiple mechanisms associated with MCC differentiation. However, YAP reportedly has both negative and positive roles in MCC differentiation, putatively due to its dual functions in the cytoplasm and nucleus. We hypothesize inhibition of nuclear YAP, while preserving cytoplasmic YAP functions, restores MCCs in various airway disorders. Here, we investigated the relationship between YAP nuclear localization and the presence of MCCs across patients. In addition, we identified compounds that promote MCC differentiation based on the inhibitory function of YAP nuclear localization.

METHOD: Tracheal specimens were collected from patients with different conditions (smoking, irradiation, tracheotomy, dysphagia), and YAP nuclear localization in MCCs was assessed by immunohistochemistry at areas with varying MCC compositions. To identify compounds that efficiently inhibit nuclear localization of YAP, airway epithelial cells were treated with multiple YAP inhibitors and YAP nuclear localization was assessed by immunofluorescence-based image analysis. The effects of the compounds on MCC differentiation were evaluated using air-liquid interface (ALI) culture and rat airway squamous metaplasia models.

RESULTS

In the human trachea, YAP nuclear localization in MCCs was negatively correlated with the proportion of MCCs in the epithelium, regardless of patient condition. Among known YAP inhibitors, verteporfin and atorvastatin efficiently inhibited YAP nuclear localization in cultured airway epithelial cells. Additionally, verteporfin promoted MCC differentiation in ALI culture and in vivo squamous metaplasia models.

CONCLUSION

Our findings suggest YAP nuclear localization in human airway MCCs is broadly associated with decreased MCCs regardless of patient condition, and verteporfin improves airway MCC differentiation.