Auditory and vestibular hair cell stereocilia: relationship between functionality and inner ear disease

A Preliminary Data Visualization Approach to Vestibulocochlear Diseases Based on Multiple Scalar Dimensions

For vestibulocochlear diseases, traditional clinical history-taking, and the terminology of widely taught nosologic taxonomy, have misleading implications that can lead to errors in diagnosis and therefore in treatment. In the interest of facilitating differential diagnosis while simultaneously recognizing that many of these diseases may not be as discrete as textbooks suggest, we propose a data visualization approach focusing on several continuous scalar dimensions in the domains of anatomy, physiology, and chronology. We illustrate the application of this approach to several categories of clinical presentation.

Distribution of ciliary adaptor proteins tubby and TULP3 in the organ of Corti

Tubby-like proteins are membrane-associated adaptors that mediate directional trafficking into primary cilia. In inner ear sensory epithelia, cilia-including the hair cell's kinocilium-play important roles as organizers of polarity, tissue architecture and cellular function. However, auditory dysfunction in tubby mutant mice was recently found to be related to a non-ciliary function of tubby, the organization of a protein complex in sensory hair bundles of auditory outer hair cells (OHCs). Targeting of signaling components into cilia in the cochlea might therefore rather rely on closely related tubby-like proteins (TULPs). In this study, we compared cellular and subcellular localization of tubby and TULP3 in the mouse inner ear sensory organs. Immunofluorescence microscopy confirmed the previously reported highly selective localization of tubby in the stereocilia tips of OHCs and revealed a previously unnoticed transient localization to kinocilia during early postnatal development. TULP3 was detected in the organ of Corti and vestibular sensory epithelium, where it displayed a complex spatiotemporal pattern. TULP3 localized to kinocilia of cochlear and vestibular hair cells in early postnatal development but disappeared subsequently before the onset of hearing. This pattern suggested a role in targeting ciliary components into kinocilia, possibly related to the developmental processes that shape the sensory epithelia. Concurrent with loss from kinocilia, pronounced TULP3 immunolabeling progressively appeared at microtubule bundles in non-sensory Pillar (PCs) and Deiters cells (DC). This subcellular localization may indicate a novel function of TULP proteins associated with the formation or regulation of microtubule-based cellular structures.

The Rho GTPase Cell Division Cycle 42 Regulates Stereocilia Development in Cochlear Hair Cells

Stereocilia are actin-based cell protrusions on the apical surface of inner ear hair cells, playing a pivotal role in hearing and balancing sensation. The development and maintenance of stereocilia is tightly regulated and deficits in this process usually lead to hearing or balancing disorders. The Rho GTPase cell division cycle 42 (CDC42) is a key regulator of the actin cytoskeleton. It has been reported to localize in the hair cell stereocilia and play important roles in stereocilia maintenance. In the present work, we utilized hair cell-specific Cdc42 knockout mice and CDC42 inhibitor ML141 to explore the role of CDC42 in stereocilia development. Our data show that stereocilia height and width as well as stereocilia resorption are affected in Cdc42-deficient cochlear hair cells when examined at postnatal day 8 (P8). Moreover, ML141 treatment leads to planar cell polarity (PCP) deficits in neonatal hair cells. We also show that overexpression of a constitutively active mutant CDC42 in cochlear hair cells leads to enhanced stereocilia developmental deficits. In conclusion, the present data suggest that CDC42 plays a pivotal role in regulating hair cell stereocilia development.

Therapeutic perspectives for structural and functional abnormalities of cilia

Ciliopathies are a group of hereditary disorders that result from structural or functional abnormalities of cilia. Recent intense research efforts have uncovered the genetic bases of ciliopathies, and our understanding of the assembly and functions of cilia has been improved significantly. Although mechanism-specific therapies for ciliopathies have not yet received regulatory approval, the use of innovative therapeutic modalities such as oligonucleotide therapy, gene replacement therapy, and gene editing in addition to symptomatic treatments are expected to provide valid treatment options in the near future. Moreover, candidate chemical compounds for developing small molecule drugs to treat ciliopathies have been identified. This review introduces the key features of cilia and ciliopathies, and summarizes the advances as well as the challenges that remain with the development of therapies for treating ciliopathies.

The involvement of liquid crystals in multichannel implanted neurostimulators, hearing and ENT infections, and cancer

Liquid crystals (LCs) consist of assemblies of molecules, between one and tens of nanometers, grouped in identifiable cohorts according to orientation and structure, which is often lamellar with varying chirality. The term liquid phase (Lo phase) designates certain such mesophases. This variety in geometry corresponds to a variety of functions. Some molecules, both organic and inorganic, used in applied engineering, and association with LCs confer new properties. Applying these aspects of LCs in manufacturing implantable material is a growing technology, especially in the interfaces of differentiated multichannel electro-neurostimulation. We highlight the involvement of LCs in the head and neck region, and the role mesophases play in outer hair cell electromotility (mechanotransduction). We summarize implications of LCs this for multichannel electroneurostimulation implant engineering, and highlight their role importance of LCs in early oncogenic process, HPV, and latency in (Epstein-Barr) and other pathogens. Our approach should help give rise to new therapeutic perspectives. Focusing on upstream nanometric phenomena needs to take on board classic determinism, quantum probability, and statistical complexity.

Cochlear Proteins Associated with Noise-induced Hearing Loss: An Update

Noise-induced hearing loss (NIHL) is one of the major occupational disease that has influence on the quality of life of mining workers. Several reports suggest NIHL is attributed to noise exposure at workplace and approximately 16% of hearing loss is due to it. NIHL occurs as a result of exposure to high-level noise (>85 dB) in the workplace. Noise disrupts proteins present in the micromachinery of the ear that is required for mechano-electric transduction of sound waves. High-level noise exposure can lead to hearing impairment owing to mechanical and metabolic exhaustion in cochlea, the major organ responsible for resilience of sound. Several key proteins of cochlea include tectorial membrane, inner hair cells, outer hair cells, and stereocilia are damaged due to high-level noise exposure. Numerous studies conducted in animals have shown cochlear proteins involvement in NIHL, but the pertinent literature remains limited in humans. Detection of proteins and pathways perturbed within the micromachinery of the ear after excessive sound induction leads toward the early identification of hearing loss. The situation insisted to present this review as an update on cochlear proteins associated with NIHL after an extensive literature search using several electronic databases which help to understand the pathophysiology of NIHL.

Usher's Syndrome Type II: A Comparative Study of Genetic Mutations and Vestibular System Evaluation

Objective Usher's syndrome type II (USH2) is characterized by moderate to profound congenital hearing loss, later onset of retinitis pigmentosa, and normal vestibular function. Recently, a study investigating the vestibular function of USH2 patients demonstrated a pathologic response to vestibular tests. In this cross-sectional study we performed vestibular tests of a group patients with genetic diagnosis of USH2 syndrome to demonstrate if vestibular damage is present in USH2 patients. Study Design Cross-sectional study. Setting Tertiary referral center. Subjects and Methods Mutated genes of 7 patients with a clinical diagnosis of USH2 were evaluated. Vestibular function was investigated by audiometry, Fitzgerald-Hallpike caloric vestibular testing, cervical vestibular evoked myogenic potentials (C-VEMPs), ocular vestibular evoked myogenic potentials (O-VEMPs), and video head impulse test (v-HIT). Results Genetic tests confirmed the USH2 diagnosis in 5 of 7 patients examined, with 1 patient reporting a unique mutation on genetic tests. Four (80%) of the 5 patients with a genetic diagnosis of USH2 showed pathological O-VEMPs. Two patients (40%) reported bilateral absent or abnormal values of C-VEMPs. The superior semicircular canal presented a significant deficit in 2 (40%) patients. The same 2 cases showed a pathologic response of the v-HIT of the horizontal semicircular canal. Finally, the posterior semicircular canal presented a significant deficit in 4 (40.0%) patients. Conclusion A vestibular evaluation with vestibular evoked myogenic potentials and v-HIT seems to identify latent damage to the vestibular receptors of USH2 patients.

Usher's Syndrome: Evaluation of the Vestibular System with Cervical and Ocular Vestibular Evoked Myogenic Potentials and the Video Head Impulse Test

OBJECTIVE

The Usher's syndrome (USH) is composed of a group of inherited disorders characterized by a dual sensory impairment of the audiovestibular and visual systems. Despite the established hearing loss, few authors have investigated vestibular dysfunction in these patients.The aim of this article is to investigate otolith or ampullary dysfunction in a group of patients affected by USH by means of a diagnostic protocol using caloric vestibular tests, cervical vestibular evoked myogenic potentials (C-VEMPs), ocular vestibular evoked myogenic potentials (O-VEMPs), and video head impulse test (v-HIT) to show any selective damage of the vestibular nerve and also to identify if it is present in patients with a previous diagnosis of USH Type II.

STUDY DESIGN

Prospective study with C-VEMPs, O-VEMPs, and v-HIT.

SETTING

Tertiary referral center.

PATIENTS

Fifteen patients with USH.

INTERVENTION

Evaluation of otolith dysfunction with caloric test, C-VEMPs, and O-VEMPs and the measurement of the vestibular-ocular reflex using the v-HIT.

RESULTS

Only three cases showed normal values of all the vestibular tests performed. O-VEMPs and C-VEMPs appeared pathologic in nine and seven cases, respectively. V-HITs showed ampullary dysfunction in 10 patients. In our study, eight of the 11 patients belonging to the group of USH Type II showed a pathologic response to at least one of the vestibular tests performed.

CONCLUSION

Today, in patients affected by USH, any vestibular diagnostic protocol must include VEMPs and v-HIT to confirm the vestibular damage, identify selective deficit of the vestibular nerve, and provide useful information for a correct classification of USH.

Immunobiology of congenital cytomegalovirus infection of the central nervous system—the murine cytomegalovirus model

Congenital human cytomegalovirus infection is a leading infectious cause of long-term neurodevelopmental sequelae, including mental retardation and hearing defects. Strict species specificity of cytomegaloviruses has restricted the scope of studies of cytomegalovirus infection in animal models. To investigate the pathogenesis of congenital human cytomegalovirus infection, we developed a mouse cytomegalovirus model that recapitulates the major characteristics of central nervous system infection in human infants, including the route of neuroinvasion and neuropathological findings. Following intraperitoneal inoculation of newborn animals with mouse cytomegalovirus, the virus disseminates to the central nervous system during high-level viremia and replicates in the brain parenchyma, resulting in a focal but widespread, non-necrotizing encephalitis. Central nervous system infection is coupled with the recruitment of resident and peripheral immune cells as well as the expression of a large number of pro-inflammatory cytokines. Although infiltration of cellular constituents of the innate immune response characterizes the early immune response in the central nervous system, resolution of productive infection requires virus-specific CD8(+) T cells. Perinatal mouse cytomegalovirus infection results in profoundly altered postnatal development of the mouse central nervous system and long-term motor and sensory disabilities. Based on an enhanced understanding of the pathogenesis of this infection, prospects for novel intervention strategies aimed to improve the outcome of congenital human cytomegalovirus infection are proposed.

Inner ear symptoms and disease: pathophysiological understanding and therapeutic options

In recent years, huge advances have taken place in understanding of inner ear pathophysiology causing sensorineural hearing loss, tinnitus, and vertigo. Advances in understanding comprise biochemical and physiological research of stimulus perception and conduction, inner ear homeostasis, and hereditary diseases with underlying genetics. This review describes and tabulates the various causes of inner ear disease and defines inner ear and non-inner ear causes of hearing loss, tinnitus, and vertigo. The aim of this review was to comprehensively breakdown this field of otorhinolaryngology for specialists and non-specialists and to discuss current therapeutic options in distinct diseases and promising research for future therapies, especially pharmaceutic, genetic, or stem cell therapy.

Structural-flow trajectories for unravelling 3D tubular bundles

We cast segmentation of 3D tubular structures in a bundle as partitioning of structural-flow trajectories. Traditional 3D segmentation algorithms aggregate local pixel correlations incrementally along a 3D stack. In contrast, structural-flow trajectories establish long range pixel correspondences and their affinities propagate grouping cues across the entire volume simultaneously, from informative to non-informative places. Segmentation by trajectory clustring recovers from persistent ambiguities caused by faint boundaries or low contrast, common in medical images. Trajectories are computed by linking successive registration fields, each one registering pairs of consecutive slices of the 3D stack. We show our method effectively unravels densely packed tubular structures, without any supervision or 3D shape priors, outperforming previous 2D and 3D segmentation algorithms.