An In Vitro Model of Differentiated Human Airway Epithelia: Methods for Establishing Primary Cultures

The human airway epithelium forms a barrier between the external and internal environments, separating air from the interstitial space. However, it also serves many other functions. By active transepithelial transport of electrolytes, it controls the composition and quantity of the airway surface liquid covering the epithelium. It secretes numerous agents into the airway surface liquid, including IgA and antimicrobial factors; these form part of the defensive shield that protects the airways and lungs from infection. The activity of its cilia are key to mucociliary clearance. The epithelium participates in the inflammatory response when challenged with environmental factors or infectious agents. It responds to and produces a number of cytokines and other pro- and antiinflammatory agents. To study and understand the complex and varied functions of human airway epithelia, investigators have developed cell culture models of the epithelium. Compared to in vivo studies, such models have the important advantage of flexibility, control of experimental conditions, and greater opportunities for intervention. They also allow the study of epithelial function in the absence of other cells and tissues such as macrophages, submucosal glands, fibroblasts, and cells of the immune system. Conversely, for some studies, the presence of nonepithelial cells and tissues would be advantageous.