Genetic background in late-onset sensorineural hearing loss patients.

Genetic testing for congenital or early-onset hearing loss patients has become a common diagnostic option in many countries. On the other hand, there are few late-onset hearing loss patients receiving genetic testing, as late-onset hearing loss is believed to be a complex disorder and the diagnostic rate for genetic testing in late-onset patients is lower than that for the congenital cases. To date, the etiology of late-onset hearing loss is largely unknown. In the present study, we recruited 48 unrelated Japanese patients with late-onset bilateral sensorineural hearing loss, and performed genetic analysis of 63 known deafness gene using massively parallel DNA sequencing. As a result, we identified 25 possibly causative variants in 29 patients (60.4%). The present results clearly indicated that various genes are involved in late-onset hearing loss and a significant portion of cases of late-onset hearing loss is due to genetic causes. In addition, we identified two interesting cases for whom we could expand the phenotypic description. One case with a novel MYO7A variant showed a milder phenotype with progressive hearing loss and late-onset retinitis pigmentosa. The other case presented with Stickler syndrome with a mild phenotype caused by a homozygous frameshift COL9A3 variant. In conclusion, comprehensive genetic testing for late-onset hearing loss patients is necessary to obtain accurate diagnosis and to provide more appropriate treatment for these patients.

Cellular recognition and patterning in sensory systems.

Cells dissociated from various tissues of vertebrate embryos preferentially reaggregate with cells from the same tissue when they are mixed together. This tissue-specific recognition process in vertebrates is mainly mediated by a family of cell adhesion molecules because of their specific binding properties. Recent studies have revealed that two families of adhesion molecules, nectins and cadherins, are associated with each other, and these associations provide cells with the differential adhesive affinities required for cellular recognition and complex cellular pattern formations during development. This review provides an overview of recent findings regarding the cooperative functions of nectins and cadherins, as well as a discussion of the molecular basis underlying these functions.

Influences of Orogastric and Nasogastric Tubes on Sucking Pressure during Bottle Feeding in Immature Infants.

Orogastric (OG) and nasogastric (NG) tubes have been reported to delay breastfeeding initiation and affect respiratory function. However, the effects of feeding tubes on sucking pressure have not been well studied. Fourteen preterm infants were enrolled in this study, and their sucking pressures during bottle feeding with an OG tube, NG tube, and without any tube were measured. Sucking pressure significantly increased after changing the OG tube to an NG tube (p = 0.044). However, sucking pressure showed no significant differences after changing the feeding method from an NG tube to oral intake. Thus, NG tubes are superior to OG tubes in terms of sucking pressure.

Corrigendum: Influences of Orogastric and Nasogastric Tubes on Sucking Pressure during Bottle Feeding in Immature Infants.

This corrects the article in Kobe J Med Sci. 2023 May 31; 69(1): E25-E32.

Hearing loss in mice with disruption of auditory epithelial patterning in the cochlea.

In the cochlear auditory epithelia, sensory hair and supporting cells are arranged in a checkerboard-like mosaic pattern, which is conserved across a wide range of species. The cell adhesion molecules nectin-1 and nectin-3 are required for this pattern formation. The checkerboard-like pattern is thought to be necessary for auditory function, but has never been examined. Here, we showed the significance of checkerboard-like cellular pattern in the survival and function of sensory hair cells in the cochlear auditory epithelia of nectin-3 knockout (KO) mice. Nectin-3 KO mice showed progressive hearing loss associated with degeneration of aberrantly attached hair cells via apoptosis. Apoptotic hair cell death was due to the disorganization of tight junctions between the hair cells. Our study revealed that the checkerboard-like cellular pattern in the auditory epithelium provides a structural basis for ensuring the survival of cochlear hair cells and hearing function.

Phenotype-genotype correlation in patients with typical and atypical branchio-oto-renal syndrome.

Some patients have an atypical form of branchio-oto-renal (BOR) syndrome, which does not satisfy the diagnostic criteria, despite carrying a pathogenic variant (P variant) or a likely pathogenic variant (LP variant) of a causative gene. P/LP variants phenotypic indices have yet to be determined in patients with typical and atypical BOR syndrome. We hypothesized that determining phenotypic and genetic differences between patients with typical and atypical BOR syndrome could inform such indices. Subjects were selected from among patients who underwent genetic testing to identify the cause of hearing loss. Patients were considered atypical when they had two major BOR diagnostic criteria, or two major criteria and one minor criterion; 22 typical and 16 atypical patients from 35 families were included. Genetic analysis of EYA1, SIX1, and SIX5 was conducted by direct sequencing and multiplex ligation-dependent probe amplification. EYA1 P/LP variants were detected in 25% and 86% of atypical and typical patients, respectively. Four EYA1 P/LP variants were novel. Branchial anomaly, inner ear anomaly, and mixed hearing loss were correlated with P/LP variants. Development of refined diagnostic criteria and phenotypic indices for atypical BOR syndrome will assist in effective detection of patients with P/LP variants among those with suspected BOR syndrome.

A High Risk of Missing Congenital Cytomegalovirus-Associated Hearing Loss through Newborn Hearing Screening in Japan.

It remains unclear to what extent newborn hearing screening (NHS) detects congenital cytomegalovirus (cCMV)-associated sensorineural hearing loss (SNHL) in Japan. This study aimed to clarify the NHS results and audiological characteristics of patients with cCMV-associated SNHL. A total of 541 individuals with unilateral or bilateral hearing loss of unknown etiology were examined for cCMV infection. cCMV infection was defined by the presence of CMV DNA in the dried umbilical cord detected using real-time quantitative PCR. NHS results and audiological data were retrospectively obtained from medical records. Forty-four cases (8.1%) were positive for cCMV infection. Of them, 33 cases underwent NHS and 13 cases (39.4%) passed NHS bilaterally. The pure-tone audiograms of 21 patients were obtained. There were seven cases of unilateral SNHL, five cases of asymmetric bilateral SNHL, and nine cases of symmetric bilateral SNHL. cCMV-related hearing loss is highly heterogeneous, and there is a high risk of missing this condition through NHS.

Investigation of the hearing levels of siblings affected by a single GJB2 variant: Possibility of genetic modifiers.

OBJECTIVE: Variants in GJB2 can cause autosomal recessive deafness (DFNB1). There is evidence for genotype-phenotype correlations of GJB2 variants; however, several genotypes can cause varying levels of hearing loss likely attributable to differences in genetic or environmental background. As siblings share approximately 50% of their genetic background and usually have a common environmental background, analysis of phenotypes of siblings with a specific GJB2 variant may reveal factors relevant to phenotypic variation. There have been no previous analyses of differences in hearing among siblings carrying a single GJB2 genotype. Here, we investigated hearing differences between siblings with a single GJB2 variant, which can cause various levels of hearing loss. METHODS: We examined hearing levels in 16 pairs of siblings homozygous for the c.235delC variant of GJB2. Differences in hearing acuity between sibling pairs were detected by auditory evaluation. RESULTS: Average differences in acoustic threshold >30 dB were observed between five pairs of siblings, whereas the remaining 11 pairs had average threshold values within approximately 10 dB of one another. Hearing loss varied from moderate to profound. CONCLUSION: Our results indicate that auditory acuity associated with homozygosity for GJB2 c.235delC can vary in degree; however, in approximately 70% of younger siblings, it was approximately the same as that in the first child, despite a diverse spectrum of hearing loss among different families. These results suggest that differences in genetic background may modify the phenotype associated with homozygous GJB2 c.235delC.

Bone marrow stem cell transplantation to olfactory epithelium.

OBJECTIVES: We sought to develop a new therapeutic strategy for degeneration of olfactory receptor neurons (ORNs). METHODS: We transplanted into Balb/C mice, locally by transnasal injection and systemically via the tail vain, BrdU-labeled bone marrow stem cells, also known as NRGs, which have the ability to differentiate into neural cells. Bone marrow stem cells engrafted into the olfactory epithelium were examined immunohistochemically. RESULTS: Compared with previous studies, in which bone marrow was transplanted rather than bone marrow stem cells, migration of transplanted bone marrow stem cells into the olfactory epithelium was observed earlier, and engraftment rates were significantly higher. However, migrated bone marrow stem cells were positive for GAP43 but not for olfactory marker protein. CONCLUSIONS: These results suggest that engrafted cells had differentiated into premature, but not mature, ORNs. Further experiments using autologous bone marrow stem cells in combination with various growth factors and/or neurotrophic factors should aid the development of new therapeutic methods for degenerated ORNs.

Three-year prospective study on olfaction of patients with Parkinson's disease.

OBJECTIVE: We conducted a 3-year prospective study on olfaction of patients with Parkinson's disease (PD) in order to examine the severity and frequency of smell disorder in PD using odor identification test, Open Essence (OE) and to verify the validity of olfactory tests as a predictor of cognitive symptom onset of PD. PATIENTS AND METHODS: We conducted a prospective study by performing an annual examination over a 3-year period. For 56 cases diagnosed with PD by the Department of Neurology at our hospital, OE and Jet Stream Olfactometry (JSO) were performed to assess the olfactory function, and Mini-Mental-State Examination (MMSE) was conducted to measure cognitive impairment. RESULTS: At the beginning, 56 cases were examined, of which 42 remained to be followed up for 3 years. Based on the results of baseline, we found a correlation between OE and the average cognitive thresholds of JSO, but did not find any correlation between OE and MMSE. OE (median 4.0→4.0) and the average cognitive thresholds of JSO (median 2.2→1.6)　decreased after 3 years, and MMSE (median 29→29) also declined, but not significantly. At the 3rd year, 6 cases with MMSE score of 23 or less were identified as suspected dementia and 36 cases with more than 24 points were defined as an invariant group. In order to distinguish these two groups, OE scores of baselines were evaluated with a combination of 12 odors. Sensitivity 1.0 and specificity 0.722 were obtained and the sensitivity+specificity value (1.722) was the highest when the number of correct answers was 4 or less using an odor combination of lumber, menthol, Japanese orange, gas for household use, Hinoki cypress and condensed milk. CONCLUSION: When the number of correct answers of 6 odors (lumber, menthol, Japanese orange, gas for household use, Hinoki cypress and condensed milk) is 4 or less in patients with PD, there is a possibility that MMSE declines in 3 years.

Effect of intranasal administration of neurotrophic factors on regeneration of chemically degenerated olfactory epithelium in aging mice.

In the mammalian olfactory epithelium (OE), neurogenesis continues throughout the lifetime, by replacing olfactory receptor neurons (ORNs) lost by normal turnover in the postnatal period. However, this ability decreases with age and/or because of various toxic factors. To date, no effective treatment for olfactory dysfunction' especially because of aging, is available in clinical practice. Here, we examined the effects of intranasal administration of fibroblast growth factor-2 and insulin-like growth factor-1 in gelatin hydrogel on the degenerated OE of aging mice induced by methimazole administration. These topical treatments led to increases in the number of olfactory marker protein-positive cells, which identified mature ORNs, resulting in the increased thickness of OE. These results indicate that both fibroblast growth factor-2 and insulin-like growth factor-1 promote the proliferation of basal cells and differentiation of immature ORNs into mature ORNs in the degenerated OE of aging mice. These agents might be promising candidates for the treatment of degenerated OE of aging humans.

Synergistic action of nectins and cadherins generates the mosaic cellular pattern of the olfactory epithelium.

In the olfactory epithelium (OE), olfactory cells (OCs) and supporting cells (SCs), which express different cadherins, are arranged in a characteristic mosaic pattern in which OCs are enclosed by SCs. However, the mechanism underlying this cellular patterning is unclear. Here, we show that the cellular pattern of the OE is established by cellular rearrangements during development. In the OE, OCs express nectin-2 and N-cadherin, and SCs express nectin-2, nectin-3, E-cadherin, and N-cadherin. Heterophilic trans-interaction between nectin-2 on OCs and nectin-3 on SCs preferentially recruits cadherin via α-catenin to heterotypic junctions, and the differential distributions of cadherins between junctions promote cellular intercalations, resulting in the formation of the mosaic pattern. These observations are confirmed by model cell systems, and various cellular patterns are generated by the combinatorial expression of nectins and cadherins. Collectively, the synergistic action of nectins and cadherins generates mosaic pattern, which cannot be achieved by a single mechanism.

BDNF expression in olfactory bulb and epithelium during regeneration of olfactory epithelium.

To further understand the roles of growth factors in the olfactory neurogenesis, we studied the mRNA levels of diverse genes in olfactory bulb (OB) and olfactory epithelium (OE) during the regeneration process of OE. mRNA expression levels of various genes in the OB and OE during the regeneration processes of OE from damage induced by methimazole administration were studied by DNA microarray analysis. The results were confirmed by quantitative real-time RT-PCR and immunohistochemistry. Expression levels of various genes dramatically changed during the observation period. Among them, mRNA expression of BDNF dramatically increased in OE during the first 7 days and then decreased. In contrast, mRNA expression of BDNF in OB significantly decreased during the first 7 days after administration and then gradually increased. The changes in the mRNA levels of OMP in OB precisely followed those of OMP in OE and OB. The present results suggest that BDNF in OE contributes to the early stage of regeneration, and BDNF in OB has its role in the late stage of regeneration of olfactory receptor neurons (ORNs).

Increased inner ear susceptibility to noise injury in mice with streptozotocin-induced diabetes.

We aimed to investigate the pathophysiology of diabetes-associated hearing impairment in type 1 diabetes using mice with streptozotocin-induced diabetes (C57BL/6J; male). Hearing function was evaluated 1, 3, and 5 months after induction of diabetes (five diabetic and five control animals per time point) using auditory-evoked brain stem responses (ABRs). Mice (four diabetic and four control) were exposed to loud noise (105 dB) 5 months after induction of diabetes. ABRs were measured before and after noise exposure. Cochlear blood flows were measured by laser-Doppler flowmeter. Spiral ganglion cells (SGCs) were counted. Vessel endothelial cells were observed by CD31 immunostaining. Chronologic changes in the ABR threshold shift were not significantly different between the diabetic and control groups. However, vessel walls in the modiolus of the cochleae were significantly thicker in the diabetic group than the control group. Additionally, recovery from noise-induced injury was significantly impaired in diabetic mice. Reduced cochlea blood flows and SGC loss were observed in diabetic mice cochleae after noise exposure. Our data suggest that diabetic cochleae are more susceptible than controls to loud noise exposure, and decreased cochlear blood flow due to sclerosis of the vessels and consequent loss of SGCs are possible mechanisms of hearing impairment in diabetic patients.

Vestibular dysfunction and compensation after removal of acoustic neuroma.

OBJECTIVE: To evaluate vestibular function after unilateral acoustic neuroma surgery via a retrosigmoid approach. METHODS: Thirty-eight patients were tested using caloric irrigation, static posturography, and the Dizziness Handicap Inventory (DHI) before, and one week to nine months after surgery. RESULTS: Twenty-six patients were categorized as a response group and 12 as a no-response group on the basis of preoperative caloric irrigation findings. The posturographic parameters and DHI scores at one week after surgery showed significant deterioration in the response group, but not in the no-response group. However, they recovered to the preoperative baseline at 3 months after surgery. The posturographic parameters and DHI scores for older patients tended to be worse than those for younger patients at 6 and 9 months after surgery. CONCLUSION: Patients in whom caloric responses are retained preoperatively show a temporary disturbance of balance after removal of acoustic neuroma. Disequilibrium after surgery ameliorates to the preoperative baseline within three months due to vestibular compensation, regardless of preoperative vestibular function. It is possible that poorer vestibular compensation may facilitate incomplete recovery in older patients after surgery.

Effect of intranasal administration of basic fibroblast growth factor on olfactory epithelium.

To further study the effects of basic fibroblast growth factor (bFGF) on the olfactory epithelium, bFGF was intranasally administered twice a day for 6 weeks to 2.5-month-old and 7-month-old mice. The effects were immunohistochemically examined by using antibodies against proliferating cell nuclear antigen, olfactory marker protein, and GAP43. The number of cells positive for proliferating cell nuclear antigen in the supporting cell layer increased dramatically, and that of GAP43-positive cells, or globose basal cells, increased significantly, especially in aging mice. However, no significant changes were observed in the number of olfactory marker protein-positive cells or mature olfactory receptor neurons. These results suggest that topical application of bFGF promotes proliferation of globose basal cells and supporting cells.