Roles of the Synapse in Hair-Cell Pathology

项目总结

Project Summary Noise exposure damages synaptic connections between cochlear inner hair cells and innervating auditory nerves. Data from mammalian models and humans indicate that loss of some inner hair cell synapses can be permanent, leading to the slow degeneration of detached auditory nerves. Yet recent research also supports that the mammalian cochlea possesses the intrinsic capacity for hair cell synaptic repair following noise damage. Defining the cellular mechanisms of synapse repair following traumatic noise is a critical step toward identifying therapeutic targets to promote repair of hair cell synaptic contacts and prevent loss of auditory nerves. The overall goal of this proposal is to understand the molecular basis of morphological and functional hair cell organ repair and recovery following noise-induced damage. Current gaps in our understanding of how hair cell synapses repair following traumatic noise are in large part due to our inability to define the cellular processes that promote synaptic repair in mammalian model systems. This project will circumvent these issues by investigating mechecaniclly induced hair-cell synapse loss and subsequent repair in the zebrafish lateral line— a mechanosensory organ which is made up of clusters of innervated hair cells. Zebrafish lateral-line hair cells are comparable to mammalian hair cells at the molecular and cellular level, including a shared mechanism of hair cell synapse loss and de-innervation following traumatic overstimulation. Yet lateral line hair cells rapidly and unambiguously repair lost synaptic connections within hours following stimulus-induced damage. Aim 1 of our proposal will test the hypothesis that hair cell activity governs synaptic repair, while Aim 2 will define the contribution of inflammation to synaptic recovery and reinnervation. The results of each of our Aims will provide information on how hair cell synaptic connections are restored following traumatic overstimulation and will help identify strategies to promote endogenous repair in noise exposed cochlea, thereby preventing subsequent auditory nerve degeneration and hearing loss.