Ciliary activity in differentiating and reactivated human respiratory epithelial cells

Objective: Experimental studies of mucociliary clearance, especially those involving drug effects, suffer from the difficulty of determining whether drugs act directly on ciliary motility or whether their effects are indirect, acting via changes in cell metabolism, viscous load, or alternative mechanisms. The present study provides a solution to this problem by comparing the motile characteristics of ciliated cells that have differentiated in primary cell culture with those of demembranated cilia reactivated with MgATP. Methods: Human respiratory epithelial cells (REC) were dissociated from trachea, bronchus, nasal polyps, or turbinates and then placed in a dissociated cell culture system. Thirty-three percent of the dissociated cells contain beating cilia. Following 1 week in culture, the REC dedifferentiated, but then redifferentiated within 96 hours after they were brought to an air interface. Results: The cilia on such cells beat with planar waves consisting of power and recovery strokes. Beat frequencies at 20°C were 15 ± 2.3 Hz. Ciliary beating often was coordinated both within and between cells with a defined antilaeoplectic pattern of coordination. Either fresh or cultured cells could be demembranated with Triton X-100 and reactivated with MgATP. The activity of these reactivated models was equivalent to those observed in living cells. Conclusion: The authors have demonstrated that ciliary beat frequency of demembranated human respiratory epithelial cells can be modulated by MgATP and can be adjusted to the same level of activity as measured in living cells. This allows them to selectively test whether a drug's effects on mucociliary transport are the result of direct interactions with the ciliary apparatus or are produced through other indirect mechanisms.