ABSTRACT
The lung mediates gas exchange between the organism and its environment, a process that is pivotal in homeostasis. Achieving a sufficient gas exchange needs an air-liquid interface (ALI) that is established and maintained by the respiratory epithelium. The surface of the respiratory epithelium is protected from desiccation by an airway surface liquid (ASL). The transition from liquid-liquid interface conditions to ALI occurs during birth and depends primarily on changes in epithelial transport function. Being directly exposed to the environment, mechanisms of defence are required to protect the lungs from airborne toxic particles, allergens and microbes. Infection of the respiratory tracts and chronic obstructive pulmonary diseases are among the most frequent cause of death worldwide. Cystic Fibrosis (CF) is an autosomal recessive genetic disease caused by variants in the CF transmembrane conductance regulator (CFTR) gene, which encodes an anion channel that coordinates epithelial ion transport. CF lung disease is characterized by excessive mucus production, ASL dehydration, chronic infection with Pseudomonas aeruginosa and inflammation leading to progressive bronchiectasis and respiratory failure. This chapter (1) briefly describes how a polarized airway epithelium is generated, (2) compiles evidence for defects in the epithelial biology of the CF airway epithelium and (3) summarizes knowledge regarding the signalling pathways that may contribute to the partial loss of barrier integrity of the CF airway epithelium.
