Combined microscope-endoscopy resection of petrous bone cholesteatoma with temporary facial nerve transposition versus nontransposition.

PURPOSE: The narrow supralabyrinthine space affects surgical procedures. To study the effect of temporary transposition of geniculate ganglion of facial nerve versus nontransposition on lesion recurrence and facial nerve function in patients with petrous bone cholesteatoma. METHODS: A total of 18 patients with petrous bone cholesteatoma involving the facial nerve were treated in our hospital from November 2016 to March 2023. The main surgical method is the extended supralabyrinthine approach assisted by a microscope and an endoscope. We collected and retrospectively analyzed their medical records. RESULTS: Temporary facial nerve transposition was performed in five patients, and nontransposition was performed in 13 patients. Cholesteatoma recurred in three patients with facial nerve nontransposition, whereas none in patients with facial nerve transposition. In this study, except for one case with a second operation, postoperative facial paralysis in other cases was improved to varying degrees, and there was no significant difference between the two groups. CONCLUSION: Temporary transposition of geniculate ganglion of facial nerve will not affect the postoperative nerve function of patients and can reduce the possibility of cholesteatoma recurrence of the petrous bone.

Inhibition of ferroptosis protects House Ear Institute-Organ of Corti 1 cells and cochlear hair cells from cisplatin-induced ototoxicity.

Ferroptosis is a recently recognized form of non-apoptotic cell death caused by an iron-dependent accumulation of lipid hydroperoxides, which plays important roles in a wide spectrum of pathological conditions. The present study was aimed to investigate the impact of ferroptosis on cisplatin-induced sensory hair cell damage. Cell viability was determined by Cell Counting Kit-8 and lactase dehydrogenase assays. The reactive oxygen species (ROS) levels were evaluated by 2,7-Dichlorodi-hydrofluorescein diacetate (DCFH-DA) and MitoSox-Red staining. Mitochondrial membrane potential (MMP) was measured by tetramethylrhodamine methyl ester (TMRM) staining. Lipid peroxidation, intracellular and mitochondrial iron were detected by Liperfluo, C11-BODIPY581/591 , FerroOrange and Mito-FerroGreen, respectively. We found that cisplatin treatment not only markedly augmented ROS accumulation, decreased the MMP, but increased lipid peroxidation and iron accumulation in House Ear Institute-Organ of Corti 1 (HEI-OC1) cells. Of note, treatment with the specific ferroptosis inhibitor ferrostatin-1 could effectively abrogate the cisplatin-induced toxicity and subsequent cell death. Specifically, the improvement of mitochondrial functions is important mechanisms for protective action of ferroptosis inhibitor against cisplatin-induced damages in HEI-OC1 cells. Moreover, inhibition of ferroptosis significantly protected murine cochlear hair cells against cisplatin damage. In addition, treatment murine cochlear hair cells with ferroptosis inducer, RSL3, significantly exacerbated cisplatin-induced damage, which could be alleviated by ROS inhibitor N-acetyl-L-cysteine. Collectively, our study indicated that ferroptosis inhibition could alleviate the cisplatin-induced ototoxicity via inactivation of lipid peroxide radical and improvement of mitochondrial function in hair cells.

Identification of a novel compound heterozygous mutation in PTPRQ in a DFNB84 family with prelingual sensorineural hearing impairment.

With a prevalence of 0.1 %, hearing loss is among the most common sensory impairments and affects several million people around the world. Identification of deafness-related genes or loci may facilitate basic research and clinical translational research of the disorder. The PTPRQ gene encodes protein tyrosine phosphatase receptor Q, which is required for the formation of shaft connectors and the normal maturation and development of hair bundles in the mammalian cochlea. Here, we present the genetic and molecular characteristics of a Kazakh family with an autosomal recessive non-syndromic hearing impairment, DFNB84. Using whole-exome sequencing, we identified two mutations that together form a novel compound heterozygous mutation in PTPRQ. Sanger sequencing confirmed that the affected members inherited both the c.16_17insT (L8fsX18) and c.2714delA (E909fsX922) mutations. Both mutations lead to a frameshift and a truncated form of the protein. The novel compound heterozygous mutation co-segregated with hearing loss in this family, and neither of the two mutations was found in 200 healthy Kazakh controls or in any of the public databases. In the study, we identified novel mutations in PTPRQ responsible for DFNB84. This is the third report of PTPRQ mutations involved in deafness and the first report of familial deafness in China. The identification of novel mutations in PTPRQ presented here further confirms the essential role of PTPRQ in hearing development and auditory function. Our data provide additional molecular information for establishing a better genotype-phenotype understanding of DFNB84.

Feasibility Analysis and Surgical Details of Vestibular Schwannoma Resection via Retrolabyrinthine Approach With Preservation of Endolymphatic Sac.

Objectives: To study the feasibility of reserving the endolymphatic sac in the cerebellopontine angle (CPA) and the fundus of the internal auditory canal (IAC) by the retrolabyrinthine approach. Design: Single-center retrospective study. Methods: Through 3-dimensional preoperative computed tomography reconstruction, vestibular schwannoma (VS) resection was performed using a retrolabyrinthine approach with preservation of the endolymphatic sac in selected patients, and hearing and facial nerve functions were followed to assess the feasibility of this operation and the effectiveness of function preservation. Results: VS was completely removed in all cases and the postoperative detectable hearing retention rate (AAO-HNS hearing rating grade A, B, and C) was 80% (4/5). Postoperative facial nerve function was well preserved (HB grade I), no leakage of cerebrospinal fluid or other cranial complications was observed in all patients, and no recurrence was observed during follow-up. Conclusions: With less trauma and a promising route for hearing preservation and facial nerve functions, the retrolabyrinthine approach is a potential choice for the treatment of VS located in the IAC-CPA.

Surgical Techniques and Functional Reconstruction for Complex Tenosynovial Giant Cell Tumor of Temporal Bone and Middle Skull Base.

Objectives: Temporal tenosynovial giant cell tumors (TGCTs) are often large and have invaded the middle skull base. It is difficult to protect the important neurovascular structures around the tumor and perform functional reconstruction on the basis of complete tumor resection. This study aimed at analyzing the surgical techniques and functional reconstruction during the operation of complex TGCT of temporal bone and middle skull base. Methods: Five patients with pathologically confirmed TGCT of different complex types in the temporal bone and middle skull base were treated in our hospital from December 2020 to February 2023. We collected and retrospectively analyzed their medical records, including medical imaging, surgical procedures, and follow-up data. Results: The tumors invaded beyond the temporal bone and destroyed the middle skull base in all cases, involving the intracranial space and other important neurovascular structures. The internal carotid artery, infratemporal fossa, pterygopalatine fossa, and parapharyngeal space were also involved in 1 case. All the patients' tumors were completely removed, and the operations were performed mainly via modified infratemporal fossa approach, or combined with expanded middle cranial fossa approach. All cases with temporal and skull base destruction were repaired using the temporalis muscle flap with no occurrence of intracranial complications. The dura mater, condyle of temporomandibular joint, facial nerve, and internal carotid artery were fully preserved. Normal maxillofacial morphology was also preserved. The air conductive hearing of 2 patients was preserved. Conclusions: We found and summarized some surgical techniques that can help safeguard the important structures around massive TGCTs of temporal bone and middle skull base, and reconstruct the defects after tumor resection. The techniques are effective and feasible.

Glutamate-aspartate transporter dysfunction enhances aminoglycoside-induced cochlear hair cell death via NMDA receptor activation.

Glutamate is a crucial neurotransmitter for hearing transduction in the cochlea, but excess glutamate is detrimental to the survival of cochlear sensory cells. Glutamate-aspartate transporter (GLAST) is the major transporter for glutamate removal; however, its role in aminoglycoside-induced hair cell loss is not well studied. In the present study, we first investigated the localization and expression of GLAST over the course of development of the mouse cochlea, and we found that inhibition of GLAST increased hair cell death. However, when the glutamate receptor NMDAR was inhibited by D-AP5, hair cell death was no longer increased by the GLAST inhibitor. Our results indicate that GLAST inhibition aggravates damage to cochlear hair cells, which may occur via NMDAR, and this suggests new clinical strategies for ameliorating the ototoxicity associated with the dysfunction of glutamate metabolism.

Increased mitochondrial DNA copy number protects hair cells and HEI­OC1 cells against drug­induced apoptosis.

Several factors trigger apoptosis in cochlear hair cells. Previous studies have shown that mitochondria play key roles in apoptosis, but the role of mitochondrial deoxyribonucleic acid (mtDNA) copy number in the pathogenesis of hair cell apoptosis remains largely unknown. We used mouse cochlear hair cells and House Ear Institute­Organ of Corti 1 (HEI­OC1) cells to explore the relationship between mtDNA copy number and cell apoptosis. We found that the mtDNA copy number of hair cells was reduced relative to mitochondrial mass and hypothesized that increasing it might have a protective effect. We then increased the mtDNA copy number of the hair and HEI­OC1 cells by transfecting them with an adeno­associated virus (AAV) vector containing mitochondrial transcription factor A (TFAM). We found that the apoptosis rates decreased upon inducing apoptosis with neomycin or cisplatin (DDP). To elucidate the mechanisms, we analyzed the mitochondrial­membrane permeability and mitochondrial function of HEI­OC1 cells. Our results suggested that the increase in mtDNA copy number could protect hair cells and HEI­OC1 cells against drug­induced apoptosis by stabilizing the permeability of the mitochondrial membrane and mitochondrial function.

Novel biallelic OTOGL mutations in a Chinese family with moderate non-syndromic sensorineural hearing loss.

OBJECTIVE: Autosomal recessive non-syndromic hearing loss (DFNB) is a genetically heterogeneous disorder. So far, 55 pathogenic genes have been identified. In this study, we aim to characterize the clinical feature and the genetic cause of a Chinese DFNB family. METHODS: Whole exome sequencing was performed on the proband. Co-segregation between the hearing loss phenotype and the potential causative mutations was verified in all family members by Sanger sequencing. RESULTS: Audiologic profiles of the affected family members revealed a moderate hearing loss mainly affecting higher frequencies. Novel biallelic OTOGL mutations, c.6467C>A (p.Ser2156*) and c.6474dupA (p.Ser2159Metfs*2), were identified in this family segregating with the childhood onset DFNB. Both mutations were predicted to cause either nonsense mediated mRNA decay or premature terminations of protein synthesis. CONCLUSIONS: We identified novel biallelic OTOGL mutations in a Chinese DFNB family. To the best of our knowledge, this is the first report of OTOGL mutations causing hearing loss in the East Asian population. Our finding enriched the mutation spectrum of OTOGL associated hearing loss.

Role of histone deacetylase activity in the developing lateral line neuromast of zebrafish larvae.

Histone deacetylases are involved in many biological processes and have roles in regulating cell behaviors such as cell cycle entry, cell proliferation and apoptosis. However, the effect of histone deacetylases on the development of hair cells (HCs) has not been fully elucidated. In this study, we examined the influence of histone deacetylases on the early development of neuromasts in the lateral line of zebrafish. Hair cell development was evaluated by fluorescent immunostaining in the absence or presence of histone deacetylase inhibitors. Our results suggested that pharmacological inhibition of histone deacetylases with inhibitors, including trichostatin A, valproic acid and MS-275, reduced the numbers of both HCs and supporting cells in neuromasts. We also found that the treatment of zebrafish larvae with inhibitors caused accumulation of histone acetylation and suppressed proliferation of neuromast cells. Real-time PCR results showed that the expression of both p21 and p27 mRNA was increased following trichostatin A treatment and the increase in p53 mRNA was modest under the same conditions. However, the expression of p53 mRNA was significantly increased by treatment with a high concentration of trichostatin A. A high concentration of trichostatin A also led to increased cell death in neuromasts as detected in a TUNEL assay. Moreover, the nuclei of most of these pyknotic cells were immunohistochemically positive for cleaved caspase-3. These results suggest that histone deacetylase activity is involved in lateral line development in the zebrafish and might have a role in neuromast formation by altering cell proliferation through the expression of cell cycle regulatory proteins.