Shinji Takebayashi

Pharmacological inhibition of Notch signaling in the mature guinea pig cochlea

Recent studies using explant cultures have demonstrated that pharmacological inhibition of Notch signaling by &ggr;-secretase inhibitors generates supernumerary hair cells in embryonic or neonatal cochleae. The aim of this study was to examine the effects of such pharmacological inhibition on mature auditory epithelia in vivo. Normal adult guinea pig auditory epithelia exhibited weak or no immunoreactivity for Notch1 and Jagged1, whereas ototoxic treatment caused the upregulation of these molecules in damaged auditory epithelia. Local application of a &ggr;-secretase inhibitor in damaged cochleae generated ectopic hair cells in mature auditory epithelia. These findings indicate that pharmacological inhibition of Notch signaling is a possible strategy for hair cell regeneration in adult auditory epithelia.

Neural connections between embryonic stem cell-derived neurons and vestibular hair cells in vitro.

This study aimed to examine the potential of embryonic stem cell (ESC)-derived neural progenitors for restoration of the neural network in the peripheral vestibular system. Mouse ESC-derived neural progenitors were co-cultured with explants of vestibular sensory epithelia from neonatal mice. Histological analyses demonstrated that ESC-derived neurons substantially elongated their neurites towards vestibular hair cells, and attached to hair cells at the regions corresponding to the location of nerve endings in normal vestibular epithelia. Immunoreactivity for synaptophysin, a marker for synaptic vesicles, was present only in the cytoplasm of hair cells in sensory epithelia cultured alone, while the nerve endings of ESC-derived neurons attached to hair cells exhibited intense immunoreactivity for synaptophysin and some hair cells were moderately reactive in co-cultured specimens. The pattern of synaptophysin expression in co-cultured specimens was very similar to that observed in developing sensory epithelia, in which synaptic connections between hair cells and nerve endings are actively formed. These findings indicate that ESC-derived neurons have the potential to restore neural connections in the peripheral vestibular system.

Nestin expression in the developing Rat cochlea sensory epithelia

An intermediate filament (IF), nestin, is used as an immature cell marker because nestin occurs in neural progenitors during early development. Recent cell culture studies have indicated that proliferating otic progenitor cells express nestin in vitro. However, localization of nestin in the developing inner ear has not yet been clarified. In this study, the ontogenetical expression of nestin epitopes in the rat cochlea was examined immunohistochemically. Sensory epithelial cells in the rat Corti organ (e.g. hair cells and support cells) transiently demonstrated immunoreactivity for nestin during the late embryonic period. After birth, nestin expression in the sensory epithelia disappeared gradually. The findings of this study indicate that the expression of nestin epitopes in the developing cochlea is linked with the plasticities of sensory epithelial cells, such as proliferation or differentiation.

Nuclear translocation of β-catenin in developing auditory epithelia of mice

&bgr;-catenin, a protein component of adherens junctions, plays a role in the signalling pathway for cell proliferation. In this study, we examined the cellular distribution of &bgr;-catenin in developing auditory epithelia of mice. Immunohistochemistry for Ki67 and cyclin D indicated active cell proliferation in premature auditory epithelia. In this period, the nuclear localization of &bgr;-catenin in epithelial cells was observed together with expression of the lymphoid enhancer factor, a transcription factor in &bgr;-catenin signalling. Epithelial cells showing nuclear localization of &bgr;-catenin disappeared at the same time, as there was a decrease of cell proliferation. These findings indicate that nuclear translocation of &bgr;-catenin plays a role in cell proliferation in developing auditory epithelia.

Disruption and restoration of cell–cell junctions in mouse vestibular epithelia following aminoglycoside treatment

The intracellular junction complexes, which consist of tight junctions (TJ), adherens junctions (AJ), and desmosomes, mediate cell-cell adhesion in epithelial cells. E-cadherin, which is a major component of AJ, plays a role not only in the maintenance of cell-cell junctions, but also in repressing cell proliferation. In this study, we examined changes of E-cadherin expression in mouse vestibular epithelia following local application of neomycin using immunohistochemistry and western blotting, and morphology of cell-cell junctions by transmission electron microscopy (TEM). Immunohistochemistry and western blotting revealed down-expression of E-cadherin and its consecutive recovery. TEM demonstrated temporal disruption of cell-cell junctions. Morphology of cell-cell junctions was more rapidly restored than recovery of E-cadherin expression. Transient disruption of cell-cell junctions and down-expression of E-cadherin is a rational response for the deletion of dying hair cells, and may be associated with a limited capacity for cell proliferations in mammalian vestibular epithelia following their rapid restoration.

Outcome of regenerative therapy for age-related vocal fold atrophy with basic fibroblast growth factor

Age‐related vocal fold atrophy has become a significant voice disorder as the elderly population grows. However, several therapeutic challenges have limited attempts to improve voice quality. We reported that basic fibroblast growth factor (bFGF) stimulates fibroblasts to produce extracellular matrices such as hyaluronic acid in the lamina propria, leading to a regeneration of pliable vocal folds in animal models. The aim of this study was to determine the efficacy of bFGF for the treatment of age‐related vocal fold atrophy.

Serofendic acid promotes survival of auditory hair cells and neurons of mice.

Serofendic acid is a newly discovered neuroprotective substance derived from fetal calf serum. It has previously been shown to protect cortical neurons from the cytotoxicity of nitric oxide, glutamate and oxygen species. In the present study, we examined the protective effects of serofendic acid on auditory hair cells exposed to aminoglycoside toxicity using explant cultures of mouse auditory epithelia. We also determined the effect of serofendic acid on auditory neurons experiencing neurotrophin deprivation using primary cultures of mouse spiral ganglion neurons. Supplementation with serofendic acid significantly promoted the survival of auditory hair cells and neurons, and its protective effects were stronger than those of the caspase inhibitor z-VAD-fmk. These findings demonstrate the great potential of serofendic acid for protection of the auditory system.

Early-Onset Postirradiation Sarcoma of the Tongue after Pseudotumor Phase

Radiation-induced sarcoma usually develops after an interval of more than 10 years from the completion of radiation therapy to the diagnosis of secondary sarcoma. However, the theory of radiation-induced transformation does not rule out postirradiation sarcomas with a short latency period. We experienced the case of a patient with postirradiation leiomyosarcoma of the tongue, which occurred 19 months after he had received chemoradiotherapy. Besides the short latency period, a pseudotumor stage developed between the time of radiation exposure and the development of leiomyosarcoma. In this article, we also describe an immunohistochemical approach to diagnose leiomyosarcoma and the efficacy of a gemcitabine and docetaxel regimen.

Survival in patients with parotid gland carcinoma – Results of a multi-center study

BACKGROUND Parotid gland carcinoma is a rare malignancy, comprising only 1-4% of head and neck carcinomas; therefore, it is difficult for a single institution to perform meaningful analysis on its clinical characteristics. The aim of this study was to update the clinical knowledge of this rare disease by a multi-center approach. METHODS The study was conducted by the Kyoto University Hospital and Affiliated Facilities Head and Neck Clinical Oncology Group (Kyoto-HNOG). A total of 195 patients with parotid gland carcinoma who had been surgically treated with curative intent between 2006 and 2015 were retrospectively reviewed. Clinical results including overall survival (OS), disease-free survival (DFS), disease-specific survival (DSS), local control rate (LCR), regional control rate (RCR), and distant metastasis-free survival (DMFS) were estimated. Univariate and multivariate analyses were performed to identify prognostic factors. RESULTS The median patient age was 63years old (range 9-93years), and the median observation period was 39months. The OS, DFS, DSS, LCR, RCR, and DMFS at 3years were 85%, 74%, 89%, 92%, 88%, and 87%, respectively. Univariate analysis showed age over 74, T4, N+, preoperative facial palsy, high grade histology, perineural invasion, and vascular invasion were associated with poor OS. N+ and high grade histology were independent factors in multivariate analysis. In subgroup analysis, postoperative radiotherapy was associated with better OS in high risk patients. CONCLUSION Nodal metastases and high grade histology are important negative prognostic factors for OS. Postoperative radiotherapy is recommended in patients with advanced high grade carcinoma.

Adenoid cystic carcinoma of the head and neck: a retrospective multicenter study

Abstract Background: Adenoid cystic carcinoma of the head and neck (ACCHN) is rare and difficult to study effective treatment at one institute. Our aim is to identify prognostic factors for this disease by conducting a multicenter study at 11 institutions in Japan. Methods: A retrospective multicenter study of ACCHN was performed. One hundred and three patients were identified between 2006 and 2015. The overall survival (OS) rate for all patients was calculated, and OS, locoregional control (LRC) rate, or no distant metastasis (NDM) rate was calculated for patients in that the surgery was performed without distant metastasis (DM). Statistical analyses were performed. Results: A significant difference with multivariate analysis was observed in patients in sublingual glands, stage IV and the use of radiation therapy ≥60Gy (sufficient RT) in OS for all patients. A significant difference was observed in the use of sufficient postoperative RT in the OS and the LRC rate, and in pathological surgical margins in the NDM rate. Conclusion: Sublingual glands or stage IV was a poorer, and sufficient RT was a better prognostic factor for ACCHN. Sufficient RT was effective to prevent local recurrence after surgical resection. Positive surgical margins caused an increase in DM.