Establishment of a human in vitro model for airway epithelial repair and regeneration

The airway epithelium is constantly exposed to noxious substances and respiratory disease is among the major leading causes of death worldwide. Upon airway injury, restoration of the normal lung architecture would be desirable, but the mechanisms involved in human adult lung regeneration are poorly understood. Notably, most mechanistic studies have been performed in mouse models where exposition to chemicals, most frequently naphthalene (NP) or polidocanol (PL), causes depletion of bronchial epithelial cells followed by subsequent epithelial regeneration. Given the major differences in cellular composition in the upper respiratory epithelium between humans and mice, we have set out to develop a human in vitro model for the analysis of lung injury and regeneration using primary human bronchial epithelial cells (phBECs) cultured at the air-liquid interface. In contrast to the mouse model, NP treatment in human bronchial epithelium in vitro did not induce cell death, let alone specifically deplete club cells. PL treatment, however, led to a dose-dependent loss of epithelial cells with an IC50 of 0.047% PL. Furthermore, loss of differentiated cell types such as goblet, ciliated and club cells were observed post PL treatment followed by subsequent regeneration of the human bronchial epithelium with the appearance of differentiated cell types at the expense of basal cells within two weeks. During regeneration phase, an increase in cell count was observed based on DAPI count from immunofluorescence analysis indicates proliferation. For proof-of-concept, we will next use this human in-vitro model to assess modulation of bronchial epithelial regeneration by Notch signaling.