Kiyomi Hamaguchi

Topical insulin-like growth factor 1 treatment using gelatin hydrogels for glucocorticoid- resistant sudden sensorineural hearing loss: a prospective clinical trial

BackgroundSudden sensorineural hearing loss (SSHL) is a common condition in which patients lose the hearing in one ear within 3 days. Systemic glucocorticoid treatments have been used as standard therapy for SSHL; however, about 20% of patients do not respond. We tested the safety and efficacy of topical insulin-like growth factor 1 (IGF1) application using gelatin hydrogels as a treatment for SSHL.MethodsPatients with SSHL that showed no recovery to systemic glucocorticoid administration were recruited. We applied gelatin hydrogels, impregnated with recombinant human IGF1, into the middle ear. The primary outcome measure was the proportion of patients showing hearing improvement 12 weeks after the test treatment. The secondary outcome measures were the proportion of patients showing improvement at 24 weeks and the incidence of adverse events. The null hypothesis was that 33% of patients would show hearing improvement, as was reported for a historical control after hyperbaric oxygen therapy.ResultsIn total, 25 patients received the test treatment at a median of 23 days (range 15-32) after the onset of SSHL, between 2007 and 2009. At 12 weeks after the test treatment, 48% (95% CI 28% to 69%; P = 0.086) of patients showed hearing improvement, and the proportion increased to 56% (95% CI 35% to 76%; P = 0.015) at 24 weeks. No serious adverse events were observed.ConclusionsTopical IGF1 application using gelatin hydrogels is well tolerated and may be efficacious for hearing recovery in patients with SSHL that is resistant to systemic glucocorticoids.

Hedgehog signaling regulates prosensory cell properties during the basal-to-apical wave of hair cell differentiation in the mammalian cochlea

Mechanosensory hair cells and supporting cells develop from common precursors located in the prosensory domain of the developing cochlear epithelium. Prosensory cell differentiation into hair cells or supporting cells proceeds from the basal to the apical region of the cochleae, but the mechanism and significance of this basal-to-apical wave of differentiation remain to be elucidated. Here, we investigated the role of Hedgehog (Hh) signaling in cochlear development by examining the effects of up- and downregulation of Hh signaling in vivo. The Hh effector smoothened (Smo) was genetically activated or inactivated specifically in the developing cochlear epithelium after prosensory domain formation. Cochleae expressing a constitutively active allele of Smo showed only one row of inner hair cells with no outer hair cells (OHCs); abnormal undifferentiated prosensory-like cells were present in the lateral compartment instead of OHCs and their adjacent supporting cells. This suggests that Hh signaling inhibits prosensory cell differentiation into hair cells or supporting cells and maintains their properties as prosensory cells. Conversely, in cochlea with the Smo conditional knockout (Smo CKO), hair cell differentiation was preferentially accelerated in the apical region. Smo CKO mice survived after birth, and exhibited hair cell disarrangement in the apical region, a decrease in hair cell number, and hearing impairment. These results indicate that Hh signaling delays hair cell and supporting cell differentiation in the apical region, which forms the basal-to-apical wave of development, and is required for the proper differentiation, arrangement and survival of hair cells and for hearing ability.

Prostaglandin E receptor subtype EP4 agonist protects cochleae against noise-induced trauma

Prostaglandin E(1) is frequently used for the clinical treatment of acute sensorineural hearing loss. However, the mechanisms underlying the effects of prostaglandin E(1) on the inner ear have not yet been elucidated. The physiological effects of prostaglandin E(1) are mediated by the prostanoid receptors prostaglandin I receptor and the prostaglandin E receptor subtypes EP1, EP2, EP3, and EP4, the respective agonists for which have been purified. In the current study, we examined the efficacy of a local EP4 agonist application for the treatment of sensorineural hearing loss. We examined EP4 expression in the mouse cochlea using the reverse transcription-polymerase chain reaction and immunohistochemistry. The protective effects of local EP4 agonist treatment before or after noise exposure were tested in guinea pigs using measurements of auditory brain-stem responses and histological analysis. The results demonstrated EP4 expression in the cochlea, and showed that pre- and post-treatment with an EP4 agonist significantly attenuated threshold shifts of auditory brain stem responses, and significant attenuation in the loss of outer hair cells was found in local EP4 agonist treatment before noise exposure. These findings indicate that EP4 is involved in mechanisms for prostaglandin E(1) actions on the cochlea, and local EP4 agonist treatment could attenuate acute sensorineural hearing loss.

Cells transplanted onto the surface of the glial scar reveal hidden potential for functional neural regeneration

Significance Cell transplantation can restore function in neurodegenerative disorders, but the low rate of functional integration of donor cells into host is a major limiting factor for clinical application. This problem is closely related to the long-standing view that donor cells must be transplanted intraneurally. We show that glial scar, which is common in neurodegenerative conditions, inhibits the survival of intraneurally transplanted cells in our rat glial scar model in the auditory system. However, cells placed on the surface of scar tissue autonomously enter the nerve and become functionally integrated into the host. The glial scar, normally considered to be a barrier to cell transplantation, includes important structural and chemical cues that are disrupted by intraneural delivery but preserved by surface transplantation. Cell transplantation therapy has long been investigated as a therapeutic intervention for neurodegenerative disorders, including spinal cord injury, Parkinson’s disease, and amyotrophic lateral sclerosis. Indeed, patients have high hopes for a cell-based therapy. However, there are numerous practical challenges for clinical translation. One major problem is that only very low numbers of donor cells survive and achieve functional integration into the host. Glial scar tissue in chronic neurodegenerative disorders strongly inhibits regeneration, and this inhibition must be overcome to accomplish successful cell transplantation. Intraneural cell transplantation is considered to be the best way to deliver cells to the host. We questioned this view with experiments in vivo on a rat glial scar model of the auditory system. Our results show that intraneural transplantation to the auditory nerve, preceded by chondroitinase ABC (ChABC)-treatment, is ineffective. There is no functional recovery, and almost all transplanted cells die within a few weeks. However, when donor cells are placed on the surface of a ChABC-treated gliotic auditory nerve, they autonomously migrate into it and recapitulate glia- and neuron-guided cell migration modes to repair the auditory pathway and recover auditory function. Surface transplantation may thus pave the way for improved functional integration of donor cells into host tissue, providing a less invasive approach to rescue clinically important neural tracts.

Role of prostaglandin E receptor subtypes EP2 and EP4 in autocrine and paracrine functions of vascular endothelial growth factor in the inner ear

BackgroundThe physiological effects of prostaglandin E1 (PGE1) and prostaglandin E2 (PGE2) are mediated by the prostaglandin E receptor subtypes EP1, EP2, EP3, and EP4, and the respective agonists have been purified. PGE1 and PGE2 can increase the production of vascular endothelial growth factor (VEGF), particularly through EP2 and EP4. The biological effects of VEGF are mediated by the phosphotyrosine kinase receptors fms-related tyrosine kinase-1 (Flt-1) and fetal liver kinase-1 (Flk-1). Here we examined the effects of EP2 and EP4 agonists on the production of VEGF proteins and VEGF messenger RNAs (mRNAs) in the inner ear, using an enzyme-linked immunosorbent assay and the real-time quantitative reverse transcription-polymerase chain reaction, respectively. We also examined the localization of EP2, VEGF, Flt-1, and Flk-1 in the cochlea by immunohistochemistry.ResultsThe expression of EP2 occurred in the cochlea, and the local application of an EP2 or EP4 agonist increased VEGF protein and VEGF mRNA levels in the inner ear. Furthermore, the intensity of the VEGF immunoreactivity in the spiral ganglion appeared to be increased by the local EP2 or EP4 agonist treatment. Immunoreactivity for Flt-1, and Flk-1 was found in the cochlear sensory epithelium, spiral ganglion, spiral ligament, and stria vascularis.ConclusionsThese findings demonstrate that EP2 and EP4 agonists stimulate VEGF production in the inner ear, particularly in the spiral ganglions. Moreover, the Flt-1 and Flk-1 expression observed in the present study suggests that VEGF has autocrine and paracrine actions in the cochlea. Thus, EP2 and EP4 might be involved in the mechanisms underlying the therapeutic effects of PGE1 on acute sensorineural hearing loss via VEGF production.

In vivo imaging of mouse cochlea by optical coherence tomography.

Hypothesis Cochlear pathology can be evaluated in living animals using optical coherence tomography (OCT). Background The current imaging methods available for the detailed analysis of cochlear pathology in a clinical setting provide only limited information. Thus, a cochlear imaging modality with high definition is needed for improving the diagnosis of cochlear pathology. OCT has been used in other fields for obtaining high-resolution subsurface images, and its use could potentially be extended to the analysis of cochlear pathogenesis. Methods Slc26a4(–/–) mice, which generate endolymphatic hydrops, and their littermates were used in this study. Auditory function was monitored by the auditory brainstem responses (ABR). After the mice were placed under general anesthesia, OCT images of the cochlea were captured. The cochlea was subsequently dissected out and histologically evaluated. Three or 7 days later, the wild-type mice cochleae were visualized again. Results In ABR assessments, Slc26a4(–/–) mice showed severe hearing loss, while no significant hearing loss was found in Slc26a4(+/–) or Slc26a4(+/+) mice. OCT demonstrated normal morphology in the cochlea of both Slc26a4(+/–) and Slc26a4(+/+) mice, including the location of Reissner’s membrane. Meanwhile, in Slc26a4(–/–) mice, obvious dislocation of Reissner’s membrane was observed, indicating severe endolymphatic hydrops. These findings in the OCT images were consistent with the histologic results for the cochlear morphology, as observed with hematoxylin and eosin staining. Three or 7 days later, wild-type cochleae were successfully visualized using OCT, and no otitis media or labyrinthitis was observed. Conclusion OCT can be applied in the detection of endolymphatic hydrops in living mice, indicating the potential of OCT for cochlear imaging analyses for clinical use in the near future.

Role of PGE-type receptor 4 in auditory function and noise-induced hearing loss in mice.

This study explored the physiological roles of PGE-type receptor 4 (EP4) in auditory function. EP4-deficient mice exhibited slight hearing loss and a reduction of distortion-product otoacoustic emissions (DPOAEs) with loss of outer hair cells (OHCs) in cochleae. After exposure to intense noise, these mice showed significantly larger threshold shifts of auditory brain-stem responses (ABRs) and greater reductions of DPOAEs than wild-type mice. A significant increase of OHC loss was confirmed morphologically in the cochleae of EP4-deficient mice. Pharmacological inhibition of EP4 had a similar effect to genetic deletion, causing loss of both hearing and OHCs in C57BL/6 mice, indicating a critical role for EP4 signaling in the maintenance of auditory function. Pharmacological activation of EP4 significantly protected OHCs against noise trauma, and attenuated noise-induced hearing loss in C57BL/6 mice. These findings suggest that EP4 signaling is necessary for the maintenance of cochlear physiological function and for cochlear protection against noise-induced damage, in particular OHCs. EP4 might therefore be an effective target for cochlear disease therapeutics.

Prostaglandin E receptor subtype EP4 agonist serves better to protect cochlea than prostaglandin E1

OBJECTIVE The present study aimed to examine whether an E-prostanoid receptor 4 (EP4) agonist has superior protective effects to those of prostaglandin E1 (PGE1) in a guinea pig model of noise trauma. METHODS Drugs were locally applied on the round window membrane of guinea pig cochleae, followed by exposure of the test animals to intense noise. Protective effects mediated by an EP4 agonist were compared with those mediated by PGE1. Auditory function was monitored by measurements of the auditory brainstem response (ABR), and histological damage was assessed by immunohistochemical analysis of cochlear specimens. RESULTS Animals treated with an EP4 agonist exhibited significantly better hearing recovery than those pretreated with PGE1. Histologically, the numbers of remaining outer hair cells in cochleae treated with the EP4 agonist were significantly higher than in those treated with PGE1. CONCLUSION The selective activation of EP4 has a stronger protective effect on cochleae against noise trauma than does the broad activation of EPs by PGE1.

Hedgehog signaling is needed for development and maintenance of the cochlear sensory epithelium

foot-shock (Unconditioned Stimulus, US) was investigated by using of optical imaging. Optical signals in the auditory cortex in response to CS (a 12 kHz pure tone) and non-CS (4, 8, 16 kHz pure tones) were recorded before and after normal and sham conditioning. Results showed that the area activated by CS enlarged only after normal conditioning. Furthermore, we report that, after conditioning, auditory information could be retrieved on the basis of an electric foot-shock alone. Before conditioning, the auditory cortex showed no response to a foot-shock presented in the absence of sound. In contrast, after conditioning, the presentation of a foot-shock in the absence of sound elicited activity in the auditory cortex. Additionally, the magnitude of the optical response in the auditory cortex correlated with variation in the electrocardiogram. The area activated in the auditory cortex, in response to the foot-shock, also showed a considerable correspondence to that elicited by the CS sound. Research fund: Grant-in-Aid for Young Scientists (B) 21700435, Grant-in-Aid for Scientific Research on Innovative Areas 21120006.

Meningocele of the Temporal Bone

We report a case of meningocele of the temporal bone. A 22-year-old female consulted our hospital complaining of high grade fever and vomitting. Meningitis was detected and treated with antibiotics. About one month after the initial hospitalization, meningitis recurred. CT examination demonstrated bone defect at the skull base of mastoid cavity. We diagnosed this patient as having cholesteatoma or meningocele.Surgery was performed by the trans-mastoid approach. After mastoidectomy, a round mass was found and the mass decreased after leakage of liquor. Meningocele of the temporal bone was confirmed. Reduction of meningocele was performed using bone fragment and temporal muscle. Postoperatively, there has not been any recurrence of meningitis to date.