Analysis of motility and mucociliary function of tracheal epithelial cilia

The airway epithelium contains numerous multiciliated cells. The apical surface of multiciliated cells is covered with cilia that move at 15-25Hz. Ciliary movement is not a simple reciprocal movement and distinctly has forward and reverse movements called effective and recovery strokes, respectively. These "asymmetric" ciliary strokes push away the mucus covering the mucosa of the airway epithelium. Mucus flow created by ciliary stroke is important for capturing and expelling dust, pollen, PM2.5, pathogens, and other particles that enter the airways from outside the body. This mechanism for protecting the airways produced by ciliary movement is called mucociliary function. Defects in ciliary motility lead to impairment of mucociliary function, resulting in recurrent airway infections such as bronchitis and pneumonia, and consequently, bronchiectasis. While the analysis of ciliary beat frequency is relatively easy, the analyses of the amplitude, velocities of strokes, and the asymmetric level require specific techniques and tips. In this chapter, we present methods for the analysis of ciliary movements of a group of cilia on the luminal surface of the trachea ex vivo and individually isolated and ATP-reactivated cilia in vitro. In addition, a method for the analysis of mucociliary function is also presented.