Culture of normal human airway epithelial cells and measurement of mucin synthesis and secretion.

The plasticity of conducting airway epithelia is well recognized (1-3). Under normal conditions, the epithelia express mucociliary function, which is the first pulmonary defense mechanism against inhaled air pollutants. Aberrance in this function is either the cause or one of the major contributors to the pathogenesis of various pulmonary diseases, such as asthma and bronchitis. To exert this vital defense function, mucus-secreting cell types of surface epithelium and sub- mucosal gland synthesize and secrete a high-mol-wt mucous glycoprotein, mucin, which is responsible for the viscoelastic property of the surface mucus layer. Secreted mucus, which is able to trap air pollutants and microorganisms, is steadily removed from the airway surface by ciliary escalation. Overall, the coordinated mucociliary function helps to maintain homeostasis in airway lumen.