Challenges and opportunities in developing targeted molecular imaging to determine inner ear defects of sensorineural hearing loss

Visualization of the Spiral Ganglion Neuron in Vivo Using a Novel 177Lu Nuclear Molecule Label

For patients with severe and profound hearing loss, cochlear implant (CI), a common and effective modality for restoring hearing, directly stimulates spiral ganglion neurons (SGNs) to generate electrical activity and form auditory perception. However, the postoperative outcome of CI is significantly influenced by the number of surviving SGNs, ​​which is a key focus of preoperative evaluation​​. Existing audiologic function and radiographic tests cannot directly demonstrate the integrity of inner ear primary neurons. In this study, ​​we developed and validated​​ a radionuclide-labeled anti-vesicular glutamate transporter 1 (anti-VGLUT1) antibody-drug and achieved animal-level in vivo imaging of cochlear SGNs using nuclear imaging. By screening the public single-cell sequencing database, it is found that VGLUT1 can serve as a representative cell membrane marker for SGN in the cochlea. The potential of anti-VGLUT1 conjugated to the long half-life 177Lu as a molecular probe to detect the relative number of SGNs in SGN-injured mouse and pig models is explored. The study provides a novel method for assessing cochlear nerve integrity in vivo by visualizing target antigen expression levels through nuclear imaging. This approach is promising to help CI candidates with preoperative inner ear SGN integrity assessment, contributing to clinical decision-making.

Advances in 3D Inner Ear Reconstruction Software for Cochlear Implants: A Comprehensive Review

Auditory impairment stands as a pervasive global issue, exerting significant effects on individuals' daily functioning and interpersonal engagements. Cochlear implants (CIs) have risen as a cutting-edge solution for severe to profound hearing loss, directly stimulating the auditory nerve with electrical signals. The success of CI procedures hinges on precise pre-operative planning and post-operative evaluation, highlighting the significance of advanced three-dimensional (3D) inner ear reconstruction software. Accurate pre-operative imaging is vital for identifying anatomical landmarks and assessing cochlear deformities. Tools like 3D Slicer, Amira and OTOPLAN provide detailed depictions of cochlear anatomy, aiding surgeons in simulating implantation scenarios and refining surgical approaches. Post-operative scans play a crucial role in detecting complications and ensuring CI longevity. Despite technological advancements, challenges such as standardization and optimization persist. This review explores the role of 3D inner ear reconstruction software in patient selection, surgical planning, and post-operative assessment, tracing its evolution and emphasizing features like image segmentation and virtual simulation. It addresses software limitations and proposes solutions, advocating for their integration into clinical practice. Ultimately, this review underscores the impact of 3D inner ear reconstruction software on cochlear implantation, connecting innovation with precision medicine.

Modern In Vitro Techniques for Modeling Hearing Loss

Sensorineural hearing loss (SNHL) is a prevalent and growing global health concern, especially within operational medicine, with limited therapeutic options available. This review article explores the emerging field of in vitro otic organoids as a promising platform for modeling hearing loss and developing novel therapeutic strategies. SNHL primarily results from the irreversible loss or dysfunction of cochlear mechanosensory hair cells (HCs) and spiral ganglion neurons (SGNs), emphasizing the need for innovative solutions. Current interventions offer symptomatic relief but do not address the root causes. Otic organoids, three-dimensional multicellular constructs that mimic the inner ear's architecture, have shown immense potential in several critical areas. They enable the testing of gene therapies, drug discovery for sensory cell regeneration, and the study of inner ear development and pathology. Unlike traditional animal models, otic organoids closely replicate human inner ear pathophysiology, making them invaluable for translational research. This review discusses methodological advances in otic organoid generation, emphasizing the use of human pluripotent stem cells (hPSCs) to replicate inner ear development. Cellular and molecular characterization efforts have identified key markers and pathways essential for otic organoid development, shedding light on their potential in modeling inner ear disorders. Technological innovations, such as 3D bioprinting and microfluidics, have further enhanced the fidelity of these models. Despite challenges and limitations, including the need for standardized protocols and ethical considerations, otic organoids offer a transformative approach to understanding and treating auditory dysfunctions. As this field matures, it holds the potential to revolutionize the treatment landscape for hearing and balance disorders, moving us closer to personalized medicine for inner ear conditions.

Potential nanotechnology-based diagnostic and therapeutic approaches for Meniere's disease

Meniere's disease (MD) is a progressive inner ear disorder involving recurrent and prolonged episodes or attacks of vertigo with associated symptoms, resulting in a significantly reduced quality of life for sufferers. In most cases, MD starts in one ear; however, in one-third of patients, the disorder progresses to the other ear. Unfortunately, the etiology of the disease is unknown, making the development of effective treatments difficult. Nanomaterials, including nanoparticles (NPs) and nanocarriers, offer an array of novel diagnostic and therapeutic applications related to MD. NPs have specific features such as biocompatibility, biochemical stability, targetability, and enhanced visualization using imaging tools. This paper provides a comprehensive and critical review of recent advancements in nanotechnology-based diagnostic and therapeutic approaches for MD. Furthermore, the crucial challenges adversely affecting the use of nanoparticles to treat middle ear disorders are investigated. Finally, this paper provides recommendations and future directions for improving the performances of nanomaterials on theragnostic applications of MD.

Achievements and Challenges in Transplantation of Mesenchymal Stem Cells in Otorhinolaryngology

Otorhinolaryngology enrolls head and neck surgery in various tissues such as ear, nose, and throat (ENT) that govern different activities such as hearing, breathing, smelling, production of vocal sounds, the balance, deglutition, facial animation, air filtration and humidification, and articulation during speech, while absence of these functions can lead to high morbidity and even mortality. Conventional therapies for head and neck damaged tissues include grafts, transplants, and artificial materials, but grafts have limited availability and cause morbidity in the donor site. To improve these limitations, regenerative medicine, as a novel and rapidly growing field, has opened a new therapeutic window in otorhinolaryngology by using cell transplantation to target the healing and replacement of injured tissues. There is a high risk of rejection and tumor formation for transplantation of embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs); mesenchymal stem cells (MSCs) lack these drawbacks. They have easy expansion and antiapoptotic properties with a wide range of healing and aesthetic functions that make them a novel candidate in otorhinolaryngology for craniofacial defects and diseases and hold immense promise for bone tissue healing; even the tissue sources and types of MSCs, the method of cell introduction and their preparation quality can influence the final outcome in the injured tissue. In this review, we demonstrated the anti-inflammatory and immunomodulatory properties of MSCs, from different sources, to be safely used for cell-based therapies in otorhinolaryngology, while their achievements and challenges have been described too.

Advancements in Stem Cell Technology and Organoids for the Restoration of Sensorineural Hearing Loss

BACKGROUND

 Sensorineural hearing loss (SNHL) is a significant cause of morbidity worldwide and currently has no curative treatment. Technological advancements in stem cell therapy have led to numerous studies that examine the generation of otic sensory cells from progenitors to restore inner ear function. Recently, organoids have emerged as a promising technique to further advance the process of creating functional replacement cells after irreversible hearing loss. Organoids are the three-dimensional generation of stem cells in culture to model the tissue organization and cellular components of the inner ear. Organoids have emerged as a promising technique to create functioning cochlear structures in vitro and may provide crucial information for the utilization of stem cells to restore SNHL.

PURPOSE

 The purpose of this review is to discuss the recent advancements in stem cell-based regenerative therapy for SNHL.

RESULTS

 Recent studies have improved our understanding about the developmental pathways involved in the generation of hair cells and spiral ganglion neurons. However, significant challenges remain in elucidating the molecular interactions and interplay required for stem cells to differentiate and function as otic sensory cells. A few of the challenges encountered with traditional stem cell therapy may be addressed with organoids.

CONCLUSION

 Stem cell-based regenerative therapy holds a great potential for developing novel treatment modalities for SNHL. Further advancements are needed in addressing the challenges associated with stem cell-based regenerative therapy and promote their translation from bench to bedside.

[Development of novel drug carrier via round window membrane]

As isolated anatomical position, limited labyrinthine artery supply, and blood-labyrinth barrier hampers systemic drug delivery to the inner ear. The efficient concentration of drug treatment is unsatisfactory and there's possible side effects after systemic administration. Intratympanic injection of drug can bypass the blood-labyrinth and permeated to the hair cells or synaptic area via the round-or oval window of the cochlea. Efficacy and safety of pharmacotherapy has become increasingly relied on the inner ear delivery carrier system. The goal of this review focus on the anatomical barrier that need to be overcome in the intratympanic applications, the improvement of drug retention and specific targets, and the safety of novel drug carriers, these emerging strategies of local drug delivery promise novel and better guidance for the clinical application.

Progress in Modeling and Targeting Inner Ear Disorders with Pluripotent Stem Cells

Sensorineural hearing loss and vestibular dysfunction are caused by damage to neurons and mechanosensitive hair cells, which do not regenerate to any clinically relevant extent in humans. Several protocols have been devised to direct pluripotent stem cells (PSCs) into inner ear hair cells and neurons, which display many properties of their native counterparts. The efficiency, reproducibility, and scalability of these protocols are enhanced by incorporating knowledge of inner ear development. Modeling human diseases in vitro through genetic manipulation of PSCs is already feasible, thereby permitting the elucidation of mechanistic understandings of a wide array of disease etiologies. Early studies on transplantation of PSC-derived otic progenitors have been successful in certain animal models, yet restoration of function and long-term cell survival remain unrealized. Through further research, PSC-based approaches will continue to revolutionize our understanding of inner ear biology and contribute to the development of therapeutic treatments for inner ear disorders.