Autoregulation of Beat Frequency in Respiratory Ciliated Cells: Demonstration by Viscous Loading

Abstract

As opposed to the virtually constant load exerted by water on the cilia of ciliated protozoa, the hydrodynamic load on respiratory cilia can undergo broad variations because of changes in the rheologic properties of mucus. When water-rowing ciliated cells are exposed to increased viscosity (1 to 50 cP), their beat frequency decreases exponentially. According to Newton's fluid dynamic theory, this outcome is expected for an engine that generates constant force. However, the findings reported here indicate that when mucus-propelling respiratory ciliated cells are exposed to high viscous loads, ranging from 12 to 150 cP, the frequency of ciliary beat decreases only slightly, whereas the beat amplitude remains virtually constant. These observations suggest that ciliated cells of the respiratory tract have a functional reserve that allows them to autoregulate their mechanical output in response to the changes in viscosity to which they are normally exposed in the airway.

Sensory reception is an attribute of both primary cilia and motile cilia

“…As mucus viscosity around the cilia (i.e. the load on the system) increases, ciliary mechanics are adjusted so as to maintain a ciliary beat frequency, albeit somewhat reduced, that is sufficient to maintain transport of mucus (containing trapped pathogens and particulates) to the larynx, where it is swallowed or expectorated (Johnson et al, 1991). Cytosolic Ca 2+ levels play an important role in this process of autoregulation, and increases in cytosolic Ca 2+ are associated with changes in ciliary beat frequency (Salathe, 2006).…”

Comparison of Efficacy of Hypertonic Saline Versus Normal Saline in the Treatment of Chronic Rhinosinusitis With the Help of Ct: PNS

“…14 It appears that respiratory ciliated cells have a functional reserve that permits them to auto regulate their mechanical output in response to changing respiratory mucus viscosity. 15 The dynamic viscoelastic properties of nasal mucosa determined by oscillary rheometry has revealed significant improvement in elasticity after repeated antral lavages in chronic sinusitis. 16 It is hypothesized that it improves mucociliary function, decreases mucosal oedema and inflammatory mediators and mechanically clears inspissated mucus.…”

The effect of viscous loading on brain ependymal cilia

“…Although water-propelling cilia do appear to be able to adapt to increasing viscosity they do not appear to be as well adapted as mucous propelling respiratory cilia [9]. Johnson and colleagues [9] found that mucous propelling cilia of the respiratory tract from confluent clusters of cells or single cells showed autoregulatory properties when exposed to an increased viscous load.…”

“…Johnson and colleagues [9] found that mucous propelling cilia of the respiratory tract from confluent clusters of cells or single cells showed autoregulatory properties when exposed to an increased viscous load. Despite the use of viscous loads, that were considerably higher (1-150cP) than those used in our experiments, the beat amplitude and frequency exhibited only slight variations over viscosities ranging from 12-150cP.…”

“…Johnson and colleagues found that when they increased the viscous load beyond 180cP, ciliary activity became unpredictable [9]. Cilia on some cells stopped beating whilst others were observed to develop a fibrillatory beat pattern of high frequency and short amplitude.…”