Collagenase Treatment's Effect On Hair Cell Bundle Stiffness And Oscillations

Hair cells are the mechano-electrical transducers of the inner ear. Each cell contains a bundle comprised of 10-100 actin‐filled stereocilia protruding from the apical surface of the hair cell body. Each stereocilium is linked to the next tallest one by a tip‐link, which is attached to the mechanically gated transduction channel. The tip‐links exert tension that induces channel opening in response to an external force. When a mechanical stimulus is applied, the stereocilia are deflected about their pivots. The stereociliary pivots, tip‐links, and the transduction channels each have an associated stiffness, which add to make up the overall stiffness of the hair bundle. In vivo, in most vestibular organs, hair bundles are coupled to an overlying gelatinous membrane. In vitro studies of hair cells from the inner ear of the American Bullfrog (Rana catesbeiana) require removal of the otolithic membrane following a collagenase or protease digestion. An enzymatic alteration to the stiffness of hair bundles can affect their spontaneous oscillations. Our preliminary data indicate that a change in frequency and amplitude of oscillations occurs in hair cell bundles after 16 minutes of a collagenase treatment. To confirm whether a collagenase (Type IA-S from Clostridium histolyticum) treatment in vitro is influencing the oscillations of hair bundles via alterations in stiffness, measurements of hair bundle stiffness from an epithelium are studied pre and post repeated collagenase treatments.