The ribbon synapses of inner hair cells (IHCs) play an important role in sound encoding and neurotransmitter release. However, it remains unclear whether IHC ribbon synapse plasticity can be interrupted by ototoxic aminoglycoside stimuli. Here, we report that quantitative changes in the number of IHC ribbon synapses and hearing loss occur in response to gentamicin treatment in mice. Using 3D reconstruction, we were able to calculate the number of IHC ribbon synapses after ototoxic gentamicin exposure. Mice were injected intraperitoneally with a low dose of gentamicin (100 mg/kg) once a day for 14 days. Double immunostaining was used to identify IHC ribbon synapses; histopathology and scanning electron microscopy were used to observe the morphology of cochlear hair cells and spiral ganglion neurons (SGNs), the hearing threshold shifts were recorded by auditory brainstem response examinations. Our study shows that the maximal number of IHC ribbon synapses appeared at the 7th day after treatment, followed by a significant reduction after the 7th day regardless of ongoing treatment. Correspondingly, the maximal elevation of hearing threshold was observed at the 7th day after treatment. Meanwhile, additional cochlear components included OHCs, IHCs, and SGNs were unaffected, suggesting that IHC ribbon synapses are more susceptible to ototoxic aminoglycoside stimulation. Our study indicated that quantitative changes in the number of IHC ribbon synapses is critical response to lower dose of ototoxic stimulation, and may contribute to moderate hearing loss. Additionally, our data indcated that ribbon synaptic plasticity may require the quantitative changes to play self-protective role adapted to ototoxic aminoglycoside stimuli.

Lower dose treatment: There were no significant differences among the control (day 0), and 4, 7, and 14 days after the ototoxicity exposure (p > 0.05). Dose-dependent gentamicin treatment: There were no significant differences among the control, 100, 200, and 300 mg/kg groups after the ototoxicity exposure (p > 0.05). In contrast, we found an altered expression of otoferlin in IHCs among the control (day 0), and 4, 7, and 14 days of exposure, when the mice were exposed to gentamicin ototoxicity (p > 0.05).

Laryngeal carcinoma is one of the most common malignant tumors of the head, neck, and respiratory tract. The aim of the present study is to explore the biological function of SRY-related HMG-box 18 (SOX18) in laryngeal carcinoma cells and study the molecular mechanism involved. Initial findings indicate that the expression of SOX18 was increased in laryngeal carcinoma cell lines and tissues. The effect of SOX18 on laryngeal carcinoma cell proliferation, cell cycle, apoptosis, invasion, and migration was also identified. The results indicated that down-regulation of SOX18 significantly inhibited cell proliferation, migration, and invasion, and induced cell-cycle arrest in G0/G1 phase and apoptosis of laryngeal carcinoma cells. However, overexpression of SOX18 promoted cell proliferation, invasion, and migration, and inhibited cell apoptosis. The expression of cyclin D1, active-caspase-3, N-cadherin, MTA1, MMP-2, and MMP-7 was also regulated by the overexpression of siSOX18 or SOX18. In addition, it was found that SOX18 could also accelerate the phosphorylation of JAK2/STAT3 signaling in laryngeal carcinoma cells. Furthermore, our study indicated that SOX18 could stimulate cell proliferation, migration, and invasion of laryngeal carcinoma cells via regulation of JAK2/STAT3 signaling, which could provide a new strategy for laryngeal carcinoma diagnosis and molecular therapies.

In rodents, massive initial synapses are formed in the auditory peripheral nervous system at the early postnatal stage, and one of the major phenomena is that the number of afferent synapses in the cochlea is significantly reduced in the duration of development. This raises the hypothesis that the number of cochlear ribbon synapses are dramatically changed with hearing development and maturation. In this study, several tracers identifying activities of autophagy were applied to estimate the level of autophagy activity in the process of ribbon synapse development in mice; further, changes in the synaptic number and spiral ganglion nerve (SGN) fibers were quantitatively measured. We found robust expression of LC3B and lysosomal-associated membrane protein 1 as well as LysoTracker in or near inner hair cells and cochlear ribbon synapses in the early stage of postnatal development. Moreover, we found a significant loss in the intensity of SGN fibers at ribbon synaptic development and hearing onset. Thus, this study demonstrates that ribbon synaptic refinement and SGN fibers pruning are closely associated with the morphological and functional maturation of ribbon synapses and that synaptic refinement and SGN fiber pruning are regulated by the robust activities of autophagy in the earlier stages of auditory development.