A quantitative interspecies comparison of the respiratory mucociliary clearance mechanism

• Published in: European biophysics journal Vol. 51; no. 1; pp. 51 - 65
• Main Authors: Burn, Andreas, Schneiter, Martin, Ryser, Manuel, Gehr, Peter, Rička, Jaroslav, Frenz, Martin
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 2022; Springer Nature B.V
• Subjects: Animals; Biochemistry; Biological and Medical Physics; Biomedical and Life Sciences; Biophysics; Birds; Cattle; Cell Biology; Cilia; Handedness; Image processing; Image Processing, Computer-Assisted; Life Sciences; Mammals; Membrane Biology; Mucociliary Clearance; Mucus; Nanotechnology; Neurobiology; Original; Original Article; Respiratory system; Sheep; Swine; Trachea; Velocity; Vertebrates; Wave propagation; Wavelengths; High-speed video microscopy; Metachronal wave; Mucociliary clearance; Avian respiratory system; Ciliary beating frequency; Cilia; Metachronism
• ISSN: 0175-7571; 1432-1017; 1432-1017
• DOI: 10.1007/s00249-021-01584-8

Collectively coordinated ciliary activity propels the airway mucus, which lines the luminal surface of the vertebrate respiratory system, in cranial direction. Our contemporary understanding on how the quantitative characteristics of the metachronal wave field determines the resulting mucociliary transport is still limited, partly due to the sparse availability of quantitative observational data. We employed high-speed video reflection microscopy to image and quantitatively characterize the metachronal wave field as well as the mucociliary transport in excised bovine, porcine, ovine, lapine, turkey and ostrich samples. Image processing techniques were used to determine the ciliary beating frequency (CBF), the velocity and wavelength of the metachronal wave and the mucociliary transport velocity. The transport direction was found to strongly correlate with the mean wave propagation direction in all six species. The CBF yielded similar values (10–15 Hz) for all six species. Birds were found to exhibit higher transport speeds (130–260  μ m/s) than mammals (20–80  μ m/s). While the average transport direction significantly deviates from the tracheal long axis in mammals, no significant deviation was found in birds. The metachronal waves were found to propagate at about 4–8 times the speed of mucociliary transport in mammals, whereas in birds they propagate at about the transport speed. The mucociliary transport in birds is fast and roughly follows the TLA, whereas the transport is slower and proceeds along a left-handed spiral in mammals. The longer wavelengths and the lower ratio between the metachronal wave speed and the mucociliary transport speed provide evidence that the mucociliary clearance mechanism operates differently in birds than in mammals.