Human airway ciliary dynamics

Abstract

Airway cilia depend on precise changes in shape to transport the mucus gel overlying mucosal surfaces. The ciliary motion can be recorded in several planes using video microscopy. However, cilia are densely packed, and automated computerized systems are not available to convert these ciliary shape changes into forms that are useful for testing theoretical models of ciliary function. We developed a system for converting planar ciliary motions recorded by video microscopy into an empirical quantitative model, which is easy to use in validating mathematical models, or in examining ciliary function, e.g., in primary ciliary dyskinesia (PCD). The system we developed allows the manipulation of a model cilium superimposed over a video of beating cilia. Data were analyzed to determine shear angles and velocity vectors of points along the cilium. Extracted waveforms were used to construct a composite waveform, which could be used as a standard. Variability was measured as the mean difference in position of points on individual waveforms and the standard. The shapes analyzed were the end-recovery, end-effective, and fastest moving effective and recovery with mean (Ϯ SE) differences of 0.31(0.04), 0.25(0.06), 0.50(0.12), 0.50(0.10), m, respectively. In contrast, the same measures for three different PCD waveforms had values far outside this range. model; empirical; video; ciliated epithelia; primary ciliary dyskinesia CILIA AND FLAGELLA ARE CELLULAR organelles, which undergo dynamic cyclic shape changes that propel fluid. Most epithelial cells of the conducting airways of the lung are ciliated, and it is the function of these cells to propel mucus so that the airway is cleared of inhaled microbes and particulates. Impaired ciliary or flagellar motion is a characteristic of a number of human diseases (18,22); primary ciliary dyskinesia (PCD) and cystic fibrosis typify failures of ciliary function as a result of defects intrinsic to cilia and the result of the ciliary environment, respectively.Because the geometry of dynein-tubulin interactions and the periodic nature of dynein activation are lost when the axoneme is dismantled, it is not possible to elucidate the mechanism generating the dynamics from experiments with isolated dynein motors processing on microtubules. It is necessary to study the dynamics directly. For flagella, clear video images allow the accurate recording organelle shapes by hand and the derivation of parameters such as curvature (17,23). Automated video analysis that can be used to digitize flagellar shapes and extract dynamics has been demonstrated by Baba and Mogami (1). Given the symmetry of the flagellar beat, Eshel and Brokaw (9) showed that recording shear angle from video frames enabled the fitting of the dynamics over many cycles to a trigonometric function, thus allowing the dynamics to be described with a smooth parameter set. Some theoretical dynamics have been coupled to the experimentally acquired dynamics. For example, the shear angle of the flagellar dynamics has been used to analyze dyn...

Primary Ciliary Dyskinesia. Recent Advances in Diagnostics, Genetics, and Characterization of Clinical Disease

“…ATP hydrolysis in dynein arms generate force to induce sliding of adjacent axonemal structures, and the complex ciliary waveform in human airways (12,13,22,23,30). Approximately 200 cilia per cell beat in a coordinated fashion across each cell and across multiple cells, and this coordinated vectorial synchrony results from both planar orientation and training by ciliadriven fluid flow (31,32).…”

“…Approximately 200 cilia per cell beat in a coordinated fashion across each cell and across multiple cells, and this coordinated vectorial synchrony results from both planar orientation and training by ciliadriven fluid flow (31,32). The cilia beat in-plane, and the forward (power) stroke is more rapid and extends a bit higher into the mucus layer than the recovery stroke (30). The wave-like movement across cells results from tightly packed cilia beating at approximately 6-12 Hz.…”

Primary Ciliary Dyskinesia

“…ATP hydrolysis in dynein arms induces sliding of adjacent axonemal structures, and generates the complex ciliary waveform in human airways (16-18, 23). Several hundred cilia per cell beat in a coordinated fashion, which generates coordinated vectorial flow from planar orientation (24).…”

“…Several hundred cilia per cell beat in a coordinated fashion, which generates coordinated vectorial flow from planar orientation (24). The cilia beat in-plane, and the forward (power) stroke is more rapid and extends a bit higher into the mucus layer than the recovery stroke (23). Ciliary beating is regulated by multiple signaling molecules, including cAMP, cGMP, and NO (16).…”

Mucociliary Function

“…Movement of a motile cilium involves an active effective stroke and a recovery stroke (Sleigh, 1968;Sleigh et al, 1988), which are initiated by bending of the base of the cilium's shaft to its tip, with the active vertical stroke extending the cilia into the overlying mucus layer (Brokow, 1966;Satir and Christensen, 2007). During the recovery stroke, the ciliary motion is directed horizontally beneath the mucus layer and within the periciliary layer (Wanner et al, 1996;Smith et al, 2008;Sears et al, 2013).…”