Makoto Hosoya

Notch Inhibition Induces Cochlear Hair Cell Regeneration and Recovery of Hearing after Acoustic Trauma

Hearing loss due to damage to auditory hair cells is normally irreversible because mammalian hair cells do not regenerate. Here, we show that new hair cells can be induced and can cause partial recovery of hearing in ears damaged by noise trauma, when Notch signaling is inhibited by a γ-secretase inhibitor selected for potency in stimulating hair cell differentiation from inner ear stem cells in vitro. Hair cell generation resulted from an increase in the level of bHLH transcription factor Atoh1 in response to inhibition of Notch signaling. In vivo prospective labeling of Sox2-expressing cells with a Cre-lox system unambiguously demonstrated that hair cell generation resulted from transdifferentiation of supporting cells. Manipulating cell fate of cochlear sensory cells in vivo by pharmacological inhibition of Notch signaling is thus a potential therapeutic approach to the treatment of deafness.

Distinct Expression Patterns of Causative Genes Responsible for Hereditary Progressive Hearing Loss in Non-Human Primate Cochlea

Hearing impairment is the most frequent sensory deficit in humans. Deafness genes, which harbor pathogenic mutations that have been identified in families with hereditary hearing loss, are commonly expressed in the auditory end organ or the cochlea and may contribute to normal hearing function, yet some of the mouse models carrying these mutations fail to recapitulate the hearing loss phenotype. In this study, we find that distinct expression patterns of those deafness genes in the cochlea of a non-human primate, the common marmoset (Callithrix jacchus). We examined 20 genes whose expression in the cochlea has already been reported. The deafness genes GJB3, CRYM, GRHL2, DFNA5, and ATP6B1 were expressed in marmoset cochleae in patterns different from those in mouse cochleae. Of note, all those genes are causative for progressive hearing loss in humans, but not in mice. The other tested genes, including the deafness gene COCH, in which mutation recapitulates deafness in mice, were expressed in a similar manner in both species. The result suggests that the discrepancy in the expression between rodents and primates may account for the phenotypic difference. This limitation of the rodent models can be bypassed by using non-human primate models such as the marmoset.

Expression and Function of Sox21 During Mouse Cochlea Development

The development of the inner ear is an orchestrated process of morphogenesis with spatiotemporally controlled generations of individual cell types. Recent studies have revealed that the Sox gene family, a family of evolutionarily conserved HMG-type transcriptional factors, is differentially expressed in each cell type of the mammalian inner ear and plays critical roles in cell-fate determination during development. In this study, we examined the expression pattern of Sox21 in the developing and adult murine cochlea. Sox21 was expressed throughout the sensory epithelium in the early otocyst stage but became restricted to supporting cells during adulthood. Interestingly, the expression in adults was restricted to the inner phalangeal, inner border, and Deiters’ cells: all of these cells are in direct contact with hair cells. Evaluations of the auditory brainstem-response revealed that Sox21−/− mice suffered mild hearing impairments, with an increase in hair cells that miss their appropriate planar cell polarity. Taken together with the previously reported critical roles of SoxB1 families in the morphogenesis of inner ear sensory and neuronal cells, our results suggest that Sox21, a counteracting partner of the SoxB1 family, controls fine-tuned cell fate decisions. Also, the characteristic expression pattern may be useful for labelling a particular subset of supporting cells.

Expression pattern of wolframin, the WFS1 (Wolfram syndrome-1 gene) product, in common marmoset (Callithrix jacchus) cochlea.

Wolfram syndrome is an autosomal recessive disorder of the neuroendocrine system, known as DIDMOAD (Diabetes Insipidus, Diabetes Mellitus, Optic Atrophy and Deafness) syndrome, and considered an endoplasmic reticulum disease. Patients show mutations in WFS1, which encodes the 890 amino acid protein wolframin. Although Wfs1 knockout mice develop diabetes, their hearing level is completely normal. In this study, we examined the expression of wolframin in the cochlea of a nonhuman primate common marmoset (Callithrix jacchus) to elucidate the discrepancy in the phenotype between species and the pathophysiology of Wolfram syndrome-associated deafness. The marmoset cochlea showed wolframin immunoreactivity not only in the spiral ligament type I fibrocytes, spiral ganglion neurons, outer hair cells, and supporting cells, but in the stria vascularis basal cells, where wolframin expression was not observed in the previous mouse study. Considering the absence of the deafness phenotype in Wfs1 knockout mice, the expression of wolframin in the basal cells of primates may play an essential role in the maintenance of hearing. Elucidating the function of wolframin protein in the basal cells of primates would be essential for understanding the pathogenesis of hearing loss in patients with Wolfram syndrome, which may lead to the discovery of new therapeutics.

Distinct Expression Pattern of a Deafness Gene, KIAA1199, in a Primate Cochlea

Deafness is one of the most common types of congenital impairments, and at least half of the cases are caused by hereditary mutations. Mutations of the gene KIAA1199 are associated with progressive hearing loss. Its expression is abundant in human cochlea, but interestingly the spatial expression patterns are different between mouse and rat cochleae; the pattern in humans has not been fully investigated. We performed immunohistochemical analysis of a nonhuman primate, common marmoset (Callithrix jacchus), cochlea with a KIAA1199-specific antibody. In the common marmoset cochlea, KIAA1199 protein expression was more widespread than in rodents, with all epithelial cells, including hair cells, expressing KIAA1199. Our results suggest that the primate pattern of KIAA1199 expression is wider in comparison with rodents and may play an essential role in the maintenance of cochlear epithelial cells.

Engraftment of Human Pluripotent Stem Cell-derived Progenitors in the Inner Ear of Prenatal Mice

There is, at present, no curative treatment for genetic hearing loss. We have previously reported that transuterine gene transfer of wild type CONNEXIN30 (CX30) genes into otocysts in CX30-deleted mice could restore hearing. Cell transplantation therapy might be another therapeutic option, although it is still unknown whether stem cell-derived progenitor cells could migrate into mouse otocysts. Here, we show successful cell transplantation of progenitors of outer sulcus cell-like cells derived from human-derived induced pluripotent stem cells into mouse otocysts on embryonic day 11.5. The delivered cells engrafted more frequently in the non-sensory region in the inner ear of CX30-deleted mice than in wild type mice and survived for up to 1 week after transplantation. Some of the engrafted cells expressed CX30 proteins in the non-sensory region. This is the first report that demonstrates successful engraftment of exogenous cells in prenatal developing otocysts in mice. Future studies using this mouse otocystic injection model in vivo will provide further clues for developing treatment modalities for congenital hearing loss in humans.

Expression pattern of EYA4 in the common marmoset (Callithrix jacchus) cochlea

The eyes absent (EYA)-like genes are essential for the formation of sensory organs among fly (Drosophila melanogaster) and mammals. EYA4, one of the vertebrate genes of Eya family, is reported to be causative for late-onset mid-frequency sensorineural hearing loss in humans, while Eya4-deficient mice exhibited congenital profound deafness and otitis media with effusion due to the eustachian tube dysmorphology. Because of the species difference in the phenotype, the pathophysiology of EYA4 in the human cochlea has yet to be elucidated. Here, we examine the expression pattern of EYA4 in the cochlea of common marmoset (Callithrix jacchus), a non-human primate. The results indicated a distinct expression pattern of EYA4 in the adult marmoset cochleae, especially strong in all supporting cells, while in mouse their expressions were diminished. Interestingly, EYA4 expression in the hair cells, supporting cells and neurons was co-localized with sine oculis homeobox-SIX1, a transcription factor essential for the transcriptional activity of EYA4. The results revealed inter-species differences in the expression pattern of EYA4 gene in supporting cells between primates and rodents. The results also indicated a fundamental role of EYA4 in the primate auditory cells. Experiments with primate models such as marmosets or with human cochlear cells may provide cues about the unknown pathogenesis of EYA4-related hearing loss.

Elongated EABR Wave Latencies Observed in Patients With Auditory Neuropathy Caused by OTOF Mutation: Longer EABR latencies with OTOF mutations

We sought to determine how the pathology altered electrically evoked auditory brainstem responses (EABRs) in patients with hearing loss by evaluating EABRs in auditory neuropathy patients with OTOF mutations comparing with various types of congenital deafness.

Vocal Hygiene Education Program Reduces Surgical Interventions for Benign Vocal Fold Lesions: A Randomized Controlled Trial: Effect of Reinforced Vocal Hygiene Education

Vocal fold polyps and nodules are common benign laryngeal lesions. Currently, the Japanese health insurance system covers surgical interventions. However, the establishment of more cost‐effective conservative methods is required, because healthcare costs are viewed as a major concern, and the government and taxpayers are demanding more economical, effective treatments. In this situation, more suitable vocal hygiene education may be important for the success of cost‐effective conservative treatment. In this study, we developed a novel reinforced vocal hygiene education program and compared the results of this program with those of previous methods of teaching vocal hygiene.

A rare case of bilateral vagus nerve schwanomatosis

Schwanomatosis is the third most common form of neurofibromatosis. Schwanomatosis affecting the vagus nerve is particularly rare. In this report, we describe an extremely rare case bilateral vagus nerve schwanomatosis in a 45-year-old male patient. The patient initially presented with bilateral neck tumors and hoarseness arising after thoracic surgery. We performed left neck surgery in order to diagnose and resect the remaining tumors followed by laryngeal framework surgery to improve vocal cord closure and symptoms of hoarseness. Voice recovery was successfully achieved after surgery. An appropriate diagnosis and surgical tumor resection followed by phonosurgery improved patient quality of life in this rare case.