Forces applied by cilia measured on explants from mucociliary tissue.

Area of Science:

• Biophysics
• Cell Biology
• Biomechanics

Background:

• Mucus-propelling cilia are vital for clearing airways and other biological surfaces.
• Understanding the forces generated by cilia is crucial for comprehending their function.

Purpose of the Study:

• To measure the forces exerted by individual, intact mucus-propelling cilia during their effective stroke.
• To investigate the contribution of dynein arms to ciliary force generation.

Main Methods:

• Utilized a novel combined system of atomic force microscopy (AFM) and an electrooptic system.
• AFM probe measured ciliary deflection, while the electrooptic system monitored frequency to prevent probe-induced perturbation.
• Experiments were conducted on cilia isolated from frog esophagus.

Main Results:

• Successfully measured forces generated by intact, beating cilia for the first time.
• Determined an average force of approximately 0.21 nN per cilium during the effective stroke.
• Observed no perturbation of ciliary frequency due to the AFM probe.

Conclusions:

• The measured force, combined with known ciliary structure, indicates that most dynein arms along the axoneme are active during the effective stroke.
• This study provides direct force measurements, advancing our understanding of ciliary propulsion mechanisms.