Histone acetylation in refractory sudden sensorineural hearing loss patients after intratympanic methylprednisolone perfusion

Elucidation of the Hdac2/Sp1/miR-204-5p/Bcl-2 axis as a modulator of cochlear apoptosis via in vivo/in vitro models of acute hearing loss

We previously reported that dysregulation of histone deacetylase 2 (Hdac2) was associated with the prognosis of sudden sensorineural hearing loss. However, the underlying molecular mechanisms are poorly understood. In the present study, we developed an acute hearing loss animal model in guinea pigs by infusing lipopolysaccharides (LPS) into the cochlea and measured the expression of Hdac2 in the sensory epithelium. We observed that the level of Hdac2 was significantly decreased in the LPS-infused cochleae. The levels of apoptosis-inhibition genes Bcl-2 and Bcl-xl were also decreased in the cochlea and correlated positively with the levels of Hdac2. Caspase3 or TUNEL-positive spiral ganglion neurons, hair cells, and supporting cells were observed in the LPS-infused cochleae. These in vivo observations were recapitulated in cell culture experiments. Based on bioinformatics analysis, we found miR-204-5p was engaged in the regulation of Hdac2 on Bcl-2. Molecular mechanism experiments displayed that miR-204-5p could be regulated by Hdac2 through interacting with transcription factor Sp1. Taken together, these results indicated that the Hdac2/Sp1/miR-204-5p/Bcl-2 regulatory axis mediated apoptosis in the cochlea, providing potential insights into the progression of acute hearing loss. To our knowledge, the study describes a miRNA-related mechanism for Hdac2-mediated regulation in the cochlea for the first time.

Effectiveness of Steroid Treatment for Sudden Sensorineural Hearing Loss: A Meta-analysis of Randomized Controlled Trials

Background:

The best way to administer steroids for sudden sensorineural hearing loss (SSHL) is still unclear. The present study was aimed at estimating the efficacy of steroids by intratympanic, systemic, and combined therapy (CT) routes.

Methods:

A systematic literature search was performed from 1950 to October 2019 for randomized controlled trials comparing the use of intratympanic, systemic, and combined steroid therapy for SSHL. The outcomes of recovery rate and pure tone average (PTA) improvement were assessed by random-effects and fixed-effects meta-analysis.

Results:

A total of 20 articles identified from 7 countries were eligible for analysis. Although no significant difference in recovery rate was observed between intratympanic steroid therapy (IST) and systemic steroid therapy (SST), IST did demonstrate better hearing improvement, as evidenced by a higher PTA than SST. Compared with SST, CT comprising IST and SST had significant recovery rate improvement. Patients treated with CT had a significantly higher PTA than those treated with SST. Through subgroup analysis based on the equivalent dose of prednisone, it was shown that CT led to a significantly higher PTA than SST only in the high-dose CT versus high-dose SST groups and moderate-dose CT versus high-dose SST groups.

Conclusion:

Moderate and high dose of CT could accelerate hearing improvement in SSHL.