Effects of mouse utricle stromal tissues on hair cell induction from induced pluripotent stem cells

BACKGROUND: Hair cells are important for maintaining our sense of hearing and balance. However, they are difficult to regenerate in mammals once they are lost. Clarification of the molecular mechanisms underlying inner ear disorders is also impeded by the anatomical limitation of experimental access to the human inner ear. Therefore, the generation of hair cells, possibly from induced pluripotent stem (iPS) cells, is important for regenerative therapy and studies of inner ear diseases. RESULTS: We generated hair cells from mouse iPS cells using an established stepwise induction protocol. First, iPS cells were differentiated into the ectodermal lineage by floating culture. Next, they were treated with basic fibroblast growth factor to induce otic progenitor cells. Finally, the cells were co-cultured with three kinds of mouse utricle tissues: stromal tissue, stromal tissue + sensory epithelium, and the extracellular matrix of stromal tissue. Hair cell-like cells were successfully generated from iPS cells using mouse utricle stromal tissues. However, no hair cell-like cells with hair bundle-like structures were formed using other tissues. CONCLUSIONS: Hair cell-like cells were induced from mouse iPS cells using mouse utricle stromal tissues. Certain soluble factors from mouse utricle stromal cells might be important for induction of hair cells from iPS cells

Digoxin induces inner ear damage

Auditory neuropathy is a hearing disorder in which the inner ear can detect sounds, but has a problem with sending sounds to the brain. The main pathology might be　the disorder between inner hair cell synapse and cochlear nerve. Although it is an indication for cochlear implants, there is no radical treatment yet. Therefore, a neuropathy model using animals is needed for the development of new treatment. So, we investigated digoxin-induced inner ear disorders using guinea pigs. As the results , when the digoxin was administrated into the cochlea, the number of cochlear spiral ganglion cells decreased. However, no obvious damage was observed to the cochlear hair cells. As the result of ABR (Auditory Brainstem Response), physiological dysfunction was also confirmed. As for the effect on the vestibule, the vestibular ganglion cells were damaged, but the hair cells in the otoliths and in the ampulla were not damaged. These results suggest that digoxin might be useful drug for the generation of the animal model to auditory neuropathy

ラット ゼンテイ キカン バイヨウ ニ オケル ゲンタマイシン ショウガイゴ ノ ユウモウ サイボウ ノ キノウ カイフク ニ カンスル ケンキュウ

京都大学0048新制・課程博士博士(医学)甲第12707号医博第3031号新制||医||937(附属図書館)UT51-2007-C243京都大学大学院医学研究科外科系専攻(主査)教授 金子 武嗣, 教授 鈴木 茂彦, 教授 福山 秀直学位規則第4条第1項該当Doctor of Medical ScienceKyoto UniversityDA

Olfactory marker protein directly buffers cAMP to avoid depolarization-induced silencing of olfactory receptor neurons

Olfactory receptor neurons (ORNs) use odour-induced intracellular cAMP surge to gate cyclic nucleotide-gated nonselective cation (CNG) channels in cilia. Prolonged exposure to cAMP causes calmodulin-dependent feedback-adaptation of CNG channels and attenuates neural responses. On the other hand, the odour-source searching behaviour requires ORNs to be sensitive to odours when approaching targets. How ORNs accommodate these conflicting aspects of cAMP responses remains unknown. Here, we discover that olfactory marker protein (OMP) is a major cAMP buffer that maintains the sensitivity of ORNs. Upon the application of sensory stimuli, OMP directly captured and swiftly reduced freely available cAMP, which transiently uncoupled downstream CNG channel activity and prevented persistent depolarization. Under repetitive stimulation, OMP-/- ORNs were immediately silenced after burst firing due to sustained depolarization and inactivated firing machinery. Consequently, OMP-/- mice showed serious impairment in odour-source searching tasks. Therefore, cAMP buffering by OMP maintains the resilient firing of ORNs

「平衡障害に対する新規治療法の開発」- iPS細胞による前庭再生医療 -

70515345藍野大学（34441）研究種目：基盤研究（C）（一般）研究期間：2017～202217K1134

Virus-induced expression of retinoic acid inducible gene-I and melanoma differentiation-associated gene 5 in the cochlear sensory epithelium.

The inner ear has been regarded as an immunoprivileged site because of isolation by the blood-labyrinthine barrier. Several reports have indicated the existence of immune cells in the inner ear, but there are no reports showing immunocompetence of the cochlear tissue. In this report, we examined the potential involvement of retinoic acid inducible gene-I (RIG-I) and melanoma differentiation-associated gene 5 (MDA5), which are critical for initiating antiviral innate immune responses. We found that RIG-I and MDA5 are expressed in the mouse cochlear sensory epithelium, including Hensen's and Claudius' cells. Ex vivo viral infection using Theiler's murine encephalomyelitis virus revealed that the virus replicates in these cells and that protein levels of RIG-I and MDA5 are up-regulated. Furthermore, the critical antiviral transcription factor, interferon (IFN) regulatory factor-3, is activated in the infected cells as judged by its nuclear translocation and the accumulation of type I IFN transcripts. These results strongly suggest that RIG-I and MDA5 participate in innate antiviral responses in cochlear tissue