Ribbon Synapse Reformation: A Key Role for the Hearing Restoration; A Review

 Auditory sensory epithelium of mammals has two types of mechanosensory cells including the inner hair cells (IHC) and outer hair cells (OHC). IHC in the mammalian inner ear is an important component for the sound perception. Information about the frequency, intensity, and timing of acoustic signals is transmitted rapidly and precisely via ribbon synapses of the IHCs to the type 1 spiral ganglion neurons (SGNs). Even in the absence of stimulation, these synapses drive spontaneous spiking into the afferent neuron. Evidence has shown that cochlear neuropathy leading to hearing loss may be a result of the damage to ribbon synapses

Here, we review how these synapses promote the rapid neurotransmitter release and sustained signal transmission. We also discuss the mechanisms involved in ribbon synapse reformation for hearing restoration.

Although cochlear ribbon synapses fail to regenerate spontaneously when injured, recent studies have provided evidence for cochlear synaptogenesis that will be relevant to regenerative methods for cochlear neural loss. A better understanding of mechanisms underlying synaptic reformation would be helpful in achieving reversal of sensorineural hearing loss.