Advancements of ROS-based biomaterials for sensorineural hearing loss therapy

Sensorineural hearing loss (SNHL) represents a substantial global health challenge, primarily driven by oxidative stress-induced damage within the auditory system. Excessive reactive oxygen species (ROS) play a pivotal role in this pathological process, leading to cellular damage and apoptosis of cochlear hair cells, culminating in irreversible hearing impairment. Recent advancements have introduced ROS-scavenging biomaterials as innovative, multifunctional platforms capable of mitigating oxidative stress. This comprehensive review systematically explores the mechanisms of ROS-mediated oxidative stress in SNHL, emphasizing etiological factors such as aging, acoustic trauma, and ototoxic medication exposure. Furthermore, it examines the therapeutic potential of ROS-scavenging biomaterials, positioning them as promising nanomedicines for targeted antioxidant intervention. By critically assessing recent advances in biomaterial design and functionality, this review thoroughly evaluates their translational potential for clinical applications. It also addresses the challenges and limitations of ROS-neutralizing strategies, while highlighting the transformative potential of these biomaterials in developing novel SNHL treatment modalities. This review advocates for continued research and development to integrate ROS-scavenging biomaterials into future clinical practice, aiming to address the unmet needs in SNHL management and potentially revolutionize the treatment landscape for this pervasive health issue.

Disruption of Hars2 in Cochlear Hair Cells Causes Progressive Mitochondrial Dysfunction and Hearing Loss in Mice

Mutations in a number of genes encoding mitochondrial aminoacyl-tRNA synthetases lead to non-syndromic and/or syndromic sensorineural hearing loss in humans, while their cellular and physiological pathology in cochlea has rarely been investigated in vivo. In this study, we showed that histidyl-tRNA synthetase HARS2, whose deficiency is associated with Perrault syndrome 2 (PRLTS2), is robustly expressed in postnatal mouse cochlea including the outer and inner hair cells. Targeted knockout of Hars2 in mouse hair cells resulted in delayed onset (P30), rapidly progressive hearing loss similar to the PRLTS2 hearing phenotype. Significant hair cell loss was observed starting from P45 following elevated reactive oxygen species (ROS) level and activated mitochondrial apoptotic pathway. Despite of normal ribbon synapse formation, whole-cell patch clamp of the inner hair cells revealed reduced calcium influx and compromised sustained synaptic exocytosis prior to the hair cell loss at P30, consistent with the decreased supra-threshold wave I amplitudes of the auditory brainstem response. Starting from P14, increasing proportion of morphologically abnormal mitochondria was observed by transmission electron microscope, exhibiting swelling, deformation, loss of cristae and emergence of large intrinsic vacuoles that are associated with mitochondrial dysfunction. Though the mitochondrial abnormalities are more prominent in inner hair cells, it is the outer hair cells suffering more severe cell loss. Taken together, our results suggest that conditional knockout of Hars2 in mouse cochlear hair cells leads to accumulating mitochondrial dysfunction and ROS stress, triggers progressive hearing loss highlighted by hair cell synaptopathy and apoptosis, and is differentially perceived by inner and outer hair cells.