To develop a method for the study of mucociliary clearance in small- caliber airways, we investigated ciliary function in an in vitro lung tissue culture technique in mice. Lungs were excised from 45 anesthetized mice [weight 30.9 ± 6.2 (SD) g] and inflated with 2% liquid agarose at 37°C via the trachea. After cooling to 4°C, the lungs were cut into 0.5- to 1.0-mm thick slices and cultured overnight. Ciliary beat frequency (CBF) was measured in airways cut in cross section using a computerized image processing system. In some experiments, charcoal particle transport (PT) in tangentially cut airways was also measured. Airway diameter ranged from 0.3 to 0.8 mm. In this preparation CBF was stable over a 3-h period and unaffected by minor pH changes. Both CBF and PT exhibited a linear dependency on temperature. CBF and PT were significantly correlated with each other. CBF at 37°C (18.7 ± 2.93 Hz) was almost twofold higher than values at 22°C (9.74 ± 3.11 Hz). Isoproterenol increased CBF in a dose-dependent fashion (50% effective concentration of 10-6.75 M); the effect of isoproterenol could be blocked by propranolol. Administration of forskolin (10 μM) also increased both CBF and PT significantly. These findings demonstrate the feasibility of measuring the major aspects of mucociliary clearance in this system. This approach holds promise as a technique suitable to the investigation of both the small airways of humans and other large animals as well as of airways in murine genetic models of respiratory disease.
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