New Frontiers in the Amelioration of Hearing Loss: Part 2-Hair Cell Development, Regeneration, Protection, and Rescue

The focus of the Central Institute for the Deaf conference (New Frontiers in the Amelioration of Hearing Loss, St. Louis, MO, March 22-25, 2001) was on the amelioration of hearing loss. In recent years, there has been an explosion of information on the fundamental biology of the auditory system. This explosion has paralleled significant advances in sensory aids as well as our understanding of auditory processing and rehabilitation. The overall objective of this conference was to bring together basic scientists who study cellular and molecular mechanisms of sensory cells with clinical scientists and engineers who work on the characteristics and development of sensory aids and treatments. We have published the proceedings of this conference in two issues. Part 1 (Seminars in Hearing, volume 23, number 1, 2002) was on issues related to new ideas in aural rehabilitation and sensory aids. Part 2 (this issue) focuses on hair cell development, regeneration, protection, and rescue.

As we increase our knowledge of the biology of sensory cells, it calls to question what, if any, potential applications to the treatment of hearing loss are possible. A multifaceted approach that includes biochemical, cellular, physiological, and behavioral investigations is necessary to understand the complex processes that underlie restoration of auditory function. At the biological level, most of the work related to the amelioration of hearing loss centers around sensory cell regeneration and development and around sensory cell protection and rescue. The realization of clinical gains from this research will require years of sustained investigation, but the potential benefits are great. Sensorineural hearing loss has long been considered irreversible because the production of hair cells and nerve cells in the inner ear normally ceases before birth. However, animal research has shown that under certain conditions, hair cell production can be reactivated in mature damaged ears. It also is known that these regenerated cells contribute to a recovery of hearing. Understanding the mechanisms of development is important in several ways: in regenerated sensory systems in which function is predicated on connecting neurons with regenerated sensory cells and in cochlear implants that depend on surviving neurons for their prosthetic efficacy. The mechanisms underlying these processes could be applied to enhance the efficacy of the restoration of auditory function. Research on the molecular control and cellular mechanisms of this self-repair process has been possible with modern biological methods. Although major inroads have been made in understanding the conditions under which exposure to noise or ototoxic agents cause hearing loss, the elucidation of the molecular mechanisms leading to the impairment of auditory function remains unresolved. Knowledge of these mechanisms will enable the design of rational approaches to prevention, amelioration, and treatment, which are the major concerns in research on these auditory disorders. Elucidation of these basic processes should lead to future therapeutic advances.

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