Protocol for in vivo elimination of avian auditory hair cells, multiplexed mRNA detection, immunohistochemistry, and S-phase labeling.

The avian inner ear can naturally regenerate sensory hair cells and is therefore an ideal candidate for investigating mechanisms leading to hair cell regeneration and functional recovery. Here, we present a surgical protocol for eliminating auditory hair cells via sisomicin injection into the lateral semicircular canal. We describe steps for multiplex mRNA detection in chicken basilar papilla and utricle sections. We then detail procedures for integrating immunohistochemistry for concurrent mRNA and protein visualization, complemented by S-phase labeling with EdU. For complete details on the use and execution of this protocol, please refer to Benkafadar et al., Benkafadar et al., Sato et al., Janesick et al., Scheibinger et al.1,2,3,4,5.

Hair cell regeneration, reinnervation, and restoration of hearing thresholds in the avian hearing organ.

Hearing starts, at the cellular level, with mechanoelectrical transduction by sensory hair cells. Sound information is then transmitted via afferent synaptic connections with auditory neurons. Frequency information is encoded by the location of hair cells along the cochlear duct. Loss of hair cells, synapses, or auditory neurons leads to permanent hearing loss in mammals. Birds, in contrast, regenerate auditory hair cells and functionally recover from hearing loss. Here, we characterized regeneration and reinnervation in sisomicin-deafened chickens and found that afferent neurons contact regenerated hair cells at the tips of basal projections. In contrast to development, synaptic specializations are established at these locations distant from the hair cells' bodies. The protrusions then contracted as regenerated hair cells matured and became functional 2 weeks post-deafening. We found that auditory thresholds recovered after 4-5 weeks. We interpret the regeneration-specific synaptic reestablishment as a location-preserving process that might be needed to maintain tonotopic fidelity.

An essential signaling cascade for avian auditory hair cell regeneration.

Hearing loss is a chronic disease affecting millions of people worldwide, yet no restorative treatment options are available. Although non-mammalian species can regenerate their auditory sensory hair cells, mammals cannot. Birds retain facultative stem cells known as supporting cells that engage in proliferative regeneration when surrounding hair cells die. Here, we investigated gene expression changes in chicken supporting cells during auditory hair cell death. This identified a pathway involving the receptor F2RL1, HBEGF, EGFR, and ERK signaling. We propose a cascade starting with the proteolytic activation of F2RL1, followed by matrix-metalloprotease-mediated HBEGF shedding, and culminating in EGFR-mediated ERK signaling. Each component of this cascade is essential for supporting cell S-phase entry in vivo and is integral for hair cell regeneration. Furthermore, STAT3-phosphorylation converges with this signaling toward upregulation of transcription factors ATF3, FOSL2, and CREM. Our findings could provide a basis for designing treatments for hearing and balance disorders.

Prognostic significance of the harmonized maximum standardized uptake value of 18F-FDG-PET/CT in patients with resectable oral tongue squamous cell carcinoma: a multicenter study.

OBJECTIVES: To investigate the usefulness of harmonized 18F-FDG-PET/CT parameters for predicting the postoperative recurrence and prognosis of oral tongue squamous cell carcinoma (OTSCC). METHODS: We retrospectively analyzed the cases of 107 OTSCC patients who underwent surgical resection at four institutions in Japan in 2010-2016 and evaluated the harmonized PET parameters of the maximum standardized uptake value (SUVmax), metabolic tumor volume (MTV), and total lesion glycolysis (TLG) for the primary tumor as the pSUVmax, pMTV, and pTLG. For lymph node metastasis, we used harmonized PET parameters of nodal-SUVmax, nodal-total MTV (tMTV), and nodal-total TLG (tTLG). The associations between the harmonized PET parameters and the patients' relapse-free survival (RFS) and overall survival (OS) were evaluated by the Kaplan-Meier method and Cox proportional hazard regression analysis for model 1 (preoperative stage) and model 2 (preoperative + postoperative stages). RESULTS: The harmonized SUVmax values were significantly lower than those before harmonization (p=0.012). The pSUVmax was revealed as a significant preoperative risk factor for RFS and OS. Nodal-SUVmax, nodal-tMTV, and nodal-tTLG were significant preoperative risk factors for OS. The combination of pSUVmax + nodal-SUVmax significantly stratified the patients into a low-risk group (pSUVmax <3.97 + nodal-SUVmax <2.85 or ≥2.85) and a high-risk group (pSUVmax ≥3.97 + nodal-SUVmax <2.85 or pSUVmax ≥3.97 + nodal-SUVmax ≥2.85) for recurrence and prognosis (RFS: p=0.001; OS: p<0.001). CONCLUSIONS: The harmonized pSUVmax is a significant prognostic factor for the survival of OTSCC patients. The combination of pSUVmax and nodal-SUVmax identified OTSCC patients at high risk for recurrence and poor prognosis at the preoperative stage.

COVID-19 presenting as acute epiglottitis: A case report and literature review.

Coronavirus disease 2019 (COVID-19) occasionally causes acute laryngitis, requiring emergency treatment. Understanding the characteristic laryngeal findings can help diagnose COVID-19 earlier, prevent worsening infection, and properly manage airway obstruction. Herein, we report the case of a 44-year-old male with acute epiglottitis likely caused by COVID-19. On presentation, chest computed tomography (CT) showed no signs of pneumonia. However, the larynx had extensive necrotic-like erosive lesions resembling those of tuberculous laryngitis. COVID-19 was diagnosed by reverse-transcription polymerase chain reaction, and secondary bacterial superinfections were suspected after blood testing. The symptoms improved after administration of antibiotics (sulbactam sodium/ampicillin sodium), steroids (dexamethasone), and favipiravir. The patient developed a high fever on the sixth day of hospitalization, and pneumonia was identified on CT. Various culture tests, including tuberculosis, were negative. Thus, remdesivir was administered for COVID-19-induced pneumonia. The patient gradually recovered, was transferred to another hospital, and was discharged on the 35th day of hospitalization. Six previous case reports of COVID-19-induced acute epiglottitis suggested that acute epiglottitis preceded the onset of pneumonia. The laryngeal findings from this report may be useful for diagnosing COVID-19 that does not cause pneumonia and for bringing attention to pneumonia after a COVID-19 diagnosis.

Three Cases of Hematoma in the Retropharyngeal Space.

OBJECTIVES: Hematoma in the retropharyngeal space (RPS) is a life-threatening condition that leads to rapid airway obstruction. However, the indication for airway management remains unclear. Additionally, the requirement for surgical hematoma evacuation remains undetermined. Therefore, we attempt to suggest some criteria for the management of hematoma in such cases. METHODS: We report three cases of hematoma in the RPS wherein one patient was treated without surgery and the other two underwent tracheotomy followed by hematoma evacuation. RESULTS: We found that airway management should be based on whether the glottis could be visible on laryngoscopy and dyspnea severity. The degree of hematoma, swelling, subcutaneous bleeding in the anterior neck, and emotional stability should also be considered. Proper management during the acute phase may allow for conservative treatments. Hematomas extending below the tracheal bifurcation may help ease upper airway obstruction due to pressure distribution, allowing for conservative treatment. When hematomas are surgically evacuated, tracheotomy should be performed simultaneously. Our report suggests that mediastinal hematoma evacuation could be avoided. CONCLUSION: We should determine a therapeutic strategy for hematoma in RPS based on glottis visualization, patient's condition, and extent of hematoma growth under careful observation.

Predictive factors for malignant neoplasms veiled in deep neck infections.

Background: Malignant neoplasms (MNs) in the head and neck are occasionally hidden in deep neck infections (DNIs) that require emergency treatment, which potentially leads to delayed diagnosis of MNs.Objectives: This study aimed to identify predictive factors that can prevent delays in diagnosing MNs in patients with DNIs.Methods: We retrospectively analysed data from 83 patients admitted to our hospital who were diagnosed with DNIs.Results: Four patients (4.8%) had DNIs veiling MNs in the head and neck. Statistical analyses revealed a significant association (p = .0481) of platelet to albumin ratio (PAR; ≥ 98.9 × 103) with hidden MNs in DNIs. Furthermore, concomitant cervical lymphadenopathy, especially multiple lymphadenopathies and excluding abscesses, was higher in patients with DNIs veiling MNs (p = .0142 and p = .0023, respectively).Conclusions and Significance: The PAR, which can be easily measured and readily detected, was a potential predictive factor. Moreover, performing fine-needle aspiration for lymphadenopathies could help diagnose hidden MNs in DNIs.

A novel parotid carcinoma with a prominent ghost cell population: a masquerading tumor or "salivary ghost cell carcinoma"?

Ghost cell is one of several unique cellular morphologies associated with aberrant keratinization. We encountered a novel parotid tumor containing numerous ghost cells and herein describe its histological features and discuss diagnostic problems. The patient was a 90-year-old Japanese male, who complained of swelling of the left parotid area for four months. Positron emission tomography indicated no cervical lymph node metastasis or distant metastasis. The tumor was successfully resected with no signs of recurrence or metastasis for six months after surgery. Histologically, the tumor was mainly composed of squamous cells forming irregularly shaped nests with a mixture of pleomorphic giant or multinucleated cells and bland basaloid cell. Keratinized areas were occupied by a prominent ghost cell population. Immunohistochemically, CK5/6 and CK19 were widely positive as well as AE1/AE3, p40 and p63. Nuclear expression of ß-catenin was also observed. The present case can be regarded as a particular form of squamous cell carcinoma and is believed to contain a large number of ghost cells resulting from an unclear mechanism. However, it seems difficult to consider such tumors as a clinicopathologically independent entity at present. Applying a term such as "salivary ghost cell carcinoma" would be premature.

Examination of risk factors for postoperative vestibular symptoms in patients with cholesteatoma.

BACKGROUND: In cholesteatoma, the prognosis of tympanoplasty has been well discussed in terms of hearing outcomes and residual or recurrent lesions. Postoperative dizziness and vertigo are major complications of tympanoplasty; however, few reports are available. AIMS/OBJECTIVES: We investigated each condition of cholesteatoma postoperative vestibular risk using the STAM system and staging published by EAONO/JOS, as well as findings on bony destruction. MATERIAL AND METHODS: From April 2010 to March 2021, 156 patients (166 ears) with cholesteatoma who underwent primary microscopic tympanoplasty at our hospital were registered. Subjective vestibular symptoms were recorded the day after surgery. RESULTS: Postoperative vestibular symptoms were observed in 13.9% of subjects. All of them were stage II and had both attic and mastoid lesions. Attic (p < .05) and mastoid (p < .01) lesions were risk factors. Multivariate analysis showed that significant differences were found in past histories of vestibular symptoms (p < .05) and exposure of the dura mater (p < .01). CONCLUSIONS AND SIGNIFICANCE: In the exposed dura group, the length of the prominence of the lateral semicircular canal to the middle cranial fossa dura was significantly shorter than that of the non-exposed group (p < .01). Narrow working space and downward operation may increase vestibular risk.

Up-front neck dissection followed by chemoradiotherapy for T1-T3 hypopharyngeal cancer with advanced nodal involvement.

BACKGROUND: The advantage of up-front neck dissection (UFND) followed by chemoradiotherapy (CRT) for hypopharyngeal cancer (HPC) with advanced neck involvement remains controversial. We aimed to determine the indications. METHODS: The data of 41 and 14 patients with stage IVA/B (T1-T3 and ≥N2a) HPC who underwent UFND followed by CRT and received CRT, respectively, were retrospectively analyzed and compared. RESULTS: The 5-year overall survival (OS) and disease-specific survival rates for the UFND and CRT groups were 61% and 52% (p = 0.1019), and 89% and 74% (p = 0.2333), respectively. Moreover, patients aged ≥70 years or those with a pulmonary disease history had a significantly poorer prognosis due to aspiration pneumonia in the UFND group. The 5-year regional control (RC) for the UFND and CRT groups were 92% and 57%, respectively (p = 0.0001). CONCLUSIONS: UFND followed by CRT was feasible with satisfactory RC. To further improve OS, aspiration pneumonia prevention is essential.

Electrochemical properties of the non-excitable tissue stria vascularis of the mammalian cochlea are sensitive to sounds.

Excitable cochlear hair cells convert the mechanical energy of sounds into the electrical signals necessary for neurotransmission. The key process is cellular depolarization via K+ entry from K+ -enriched endolymph through hair cells' mechanosensitive channels. Positive 80 mV potential in endolymph accelerates the K+ entry, thereby sensitizing hearing. This potential represents positive extracellular potential within the epithelial-like stria vascularis; the latter potential stems from K+ equilibrium potential (EK ) across the strial membrane. Extra- and intracellular [K+ ] determining EK are likely maintained by continuous unidirectional circulation of K+ through a putative K+ transport pathway containing hair cells and stria. Whether and how the non-excitable tissue stria vascularis responds to acoustic stimuli remains unclear. Therefore, we analysed a cochlear portion for the best frequency, 1 kHz, by theoretical and experimental approaches. We have previously developed a computational model that integrates ion channels and transporters in the stria and hair cells into a circuit and described a circulation current composed of K+ . Here, in this model, mimicking of hair cells' K+ flow induced by a 1 kHz sound modulated the circulation current and affected the strial ion transport mechanisms; the latter effect resulted in monotonically decreasing potential and increasing [K+ ] in the extracellular strial compartment. Similar results were obtained when the stria in acoustically stimulated animals was examined using microelectrodes detecting the potential and [K+ ]. Measured potential dynamics mirrored the EK change. Collectively, because stria vascularis is electrically coupled to hair cells by the circulation current in vivo too, the strial electrochemical properties respond to sounds. KEY POINTS: A highly positive potential of +80 mV in K+ -enriched endolymph in the mammalian cochlea accelerates sound-induced K+ entry into excitable sensory hair cells, a process that triggers hearing. This unique endolymphatic potential represents an EK -based battery for a non-excitable epithelial-like tissue, the stria vascularis. To examine whether and how the stria vascularis responds to sounds, we used our computational model, in which strial channels and transporters are serially connected to those hair cells in a closed-loop circuit, and found that mimicking hair cell excitation by acoustic stimuli resulted in increased extracellular [K+ ] and decreased the battery's potential within the stria. This observation was overall verified by electrophysiological experiments using live guinea pigs. The sensitivity of electrochemical properties of the stria to sounds indicates that this tissue is electrically coupled to hair cells by a radial ionic flow called a circulation current.

Characterisation of the static offset in the travelling wave in the cochlear basal turn.

In mammals, audition is triggered by travelling waves that are evoked by acoustic stimuli in the cochlear partition, a structure containing sensory hair cells and a basilar membrane. When the cochlea is stimulated by a pure tone of low frequency, a static offset occurs in the vibration in the apical turn. In the high-frequency region at the cochlear base, multi-tone stimuli induce a quadratic distortion product in the vibrations that suggests the presence of an offset. However, vibrations below 100 Hz, including a static offset, have not been directly measured there. We therefore constructed an interferometer for detecting motion at low frequencies including 0 Hz. We applied the interferometer to record vibrations from the cochlear base of guinea pigs in response to pure tones. When the animals were exposed to sound at an intensity of 70 dB or higher, we recorded a static offset of the sinusoidally vibrating cochlear partition by more than 1 nm towards the scala vestibuli. The offset's magnitude grew monotonically as the stimuli intensified. When stimulus frequency was varied, the response peaked around the best frequency, the frequency that maximised the vibration amplitude at threshold sound pressure. These characteristics are consistent with those found in the low-frequency region and are therefore likely common across the cochlea. The offset diminished markedly when the somatic motility of mechanosensitive outer hair cells, the force-generating machinery that amplifies the sinusoidal vibrations, was pharmacologically blocked. Therefore, the partition offset appears to be linked to the electromotile contraction of outer hair cells.

Primary Liposarcoma with Cholesteatoma in Mastoid.

Liposarcoma is a soft tissue neoplasm that commonly develops in the lower extremities and rarely in the head and neck region. Herein, we report the case of a patient with primary liposarcoma that was detected in the mastoid antrum during staged tympanoplasty for cholesteatoma. The tumor adjacent to the attic cholesteatoma was resected completely, and the pathological diagnosis was that of myxoid-type liposarcoma. Because positron emission tomography after the surgery showed no signs of tumor remnants or systemic metastasis, a second-stage surgery was performed 8 months after the first surgery. After confirming that there was no recurrence, tympanoplasty type III with interposition between the stapes and malleus and canal reconstruction was performed. No recurrence was observed for 5 years, and to date, good hearing has been maintained. This is the first report on long-term follow-up of a patient with liposarcoma in the mastoid antrum.

Time-controllable Nkcc1 knockdown replicates reversible hearing loss in postnatal mice.

Identification of the causal effects of specific proteins on recurrent and partially reversible hearing loss has been difficult because of the lack of an animal model that provides reversible gene knockdown. We have developed the transgenic mouse line Actin-tTS::Nkcc1 tetO/tetO for manipulatable expression of the cochlear K+ circulation protein, NKCC1. Nkcc1 transcription was blocked by the binding of a tetracycline-dependent transcriptional silencer to the tetracycline operator sequences inserted upstream of the Nkcc1 translation initiation site. Administration of the tetracycline derivative doxycycline reversibly regulated Nkcc1 knockdown. Progeny from pregnant/lactating mothers fed doxycycline-free chow from embryonic day 0 showed strong suppression of Nkcc1 expression (~90% downregulation) and Nkcc1 null phenotypes at postnatal day 35 (P35). P35 transgenic mice from mothers fed doxycycline-free chow starting at P0 (delivery) showed weaker suppression of Nkcc1 expression (~70% downregulation) and less hearing loss with mild cochlear structural changes. Treatment of these mice at P35 with doxycycline for 2 weeks reactivated Nkcc1 transcription to control levels and improved hearing level at high frequency; i.e., these doxycycline-treated mice exhibited partially reversible hearing loss. Thus, development of the Actin-tTS::Nkcc1 tetO/tetO transgenic mouse line provides a mouse model for the study of variable hearing loss through reversible knockdown of Nkcc1.

Hearing Loss Controlled by Optogenetic Stimulation of Nonexcitable Nonglial Cells in the Cochlea of the Inner Ear.

Light-gated ion channels and transporters have been applied to a broad array of excitable cells including neurons, cardiac myocytes, skeletal muscle cells and pancreatic ß-cells in an organism to clarify their physiological and pathological roles. Nonetheless, among nonexcitable cells, only glial cells have been studied in vivo by this approach. Here, by optogenetic stimulation of a different nonexcitable cell type in the cochlea of the inner ear, we induce and control hearing loss. To our knowledge, deafness animal models using optogenetics have not yet been established. Analysis of transgenic mice expressing channelrhodopsin-2 (ChR2) induced by an oligodendrocyte-specific promoter identified this channel in nonglial cells-melanocytes-of an epithelial-like tissue in the cochlea. The membrane potential of these cells underlies a highly positive potential in a K+-rich extracellular solution, endolymph; this electrical property is essential for hearing. Illumination of the cochlea to activate ChR2 and depolarize the melanocytes significantly impaired hearing within a few minutes, accompanied by a reduction in the endolymphatic potential. After cessation of the illumination, the hearing thresholds and potential returned to baseline during several minutes. These responses were replicable multiple times. ChR2 was also expressed in cochlear glial cells surrounding the neuronal components, but slight neural activation caused by the optical stimulation was unlikely to be involved in the hearing impairment. The acute-onset, reversible and repeatable phenotype, which is inaccessible to conventional gene-targeting and pharmacological approaches, seems to at least partially resemble the symptom in a population of patients with sensorineural hearing loss. Taken together, this mouse line may not only broaden applications of optogenetics but also contribute to the progress of translational research on deafness.