A modified adenovirus can transfect cochlear hair cells in vivo without compromising cochlear function

Cochlear hair cells express SK2, a small-conductance Ca2+-activated K+ channel thought to act in concert with Ca2+-permeable nicotinic acetylcholine receptors (nAChRs) α9 and α10 in mediating suppressive effects of the olivocochlear efferent innervation. To probe the in vivo role of SK2 channels in hearing, we examined gene expression, cochlear function, efferent suppression, and noise vulnerability in mice overexpressing SK2 channels. Cochlear thresholds, as measured by auditory brain stem responses and otoacoustic emissions, were normal in overexpressers as was overall cochlear morphology and the size, number, and distribution of efferent terminals on outer hair cells. Cochlear expression levels of SK2 channels were elevated eightfold without striking changes in other SK channels or in the α9/α10 nAChRs. Shock-evoked efferent suppression of cochlear responses was significantly enhanced in overexpresser mice as seen previously in α9 overexpresser mice; however, in contrast to α9 overexpressers, SK2 overexpressers were not protected from acoustic injury. Results suggest that efferent-mediated cochlear protection is mediated by other downstream effects of ACh-mediated Ca2+ entry different from those involving SK2-mediated hyperpolarization and the associated reduction in outer hair cell electromotility.

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Olivocochlear suppression of outer hair cells in vivo: evidence for combined action of BK and SK2 channels throughout the cochlea

Journal of Neurophysiology ◽

10.1152/jn.00924.2012 ◽

2013 ◽

Vol 109 (6) ◽

pp. 1525-1534 ◽

Cited By ~ 27

Author(s):

Stéphane F. Maison ◽

Sonja J. Pyott ◽

Andrea L. Meredith ◽

M. Charles Liberman

Keyword(s):

Hair Cells ◽

In Vitro Study ◽

Bk Channels ◽

Outer Hair Cells ◽

Cochlear Hair Cells ◽

Α Subunit ◽

Combined Action ◽

Cholinergic Effects

Cholinergic inhibition of cochlear hair cells via olivocochlear (OC)-efferent feedback is mediated by Ca2+ entry through α9-/α10-nicotinic receptors, but the nature of the K+ channels activated by this Ca2+ entry has been debated (Yoshida N, Hequembourg SJ, Atencio CA, Rosowski JJ, Liberman MC. J Neurophysiol 85: 84–88, 2001). A recent in vitro study (Wersinger E, McLean WJ, Fuchs PA, Pyott SJ. PLoS One 5: e13836, 2010) suggests that small-conductance (SK2) channels mediate cholinergic effects in the apical turn, whereas large-conductance (BK) channels mediate basal turn effects. Here, we measure, as a function of cochlear frequency, the magnitude of BK and SK2 expression in outer hair cells and the strength of in vivo OC suppression in BK+/+ mice vs. BK−/− lacking the obligatory α-subunit (Meredith AL, Thorneloe KS, Werner ME, Nelson MT, Aldrich RW. J Biol Chem 279: 36746–36752, 2004). Except at the extreme apical tip, we see immunostaining for both BK and SK2 in BK+/+. Correspondingly, at all testable frequencies (8–45 kHz), we see evidence for both SK2 and BK contributions to OC effects evoked by electrically stimulating the OC bundle: OC-mediated suppression was reduced, but not eliminated, at all frequencies in the BK−/− ears. The suppression remaining in BK nulls was blocked by strychnine, suggesting involvement of α9-/α10-cholinergic receptors, coupled to activation of the remaining SK2 channels.

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In vivo notch reactivation in differentiating cochlear hair cells induces sox2 and prox1 expression but does not disrupt hair cell maturation

Developmental Dynamics ◽

10.1002/dvdy.23863 ◽

2012 ◽

Vol 241 (10) ◽

Author(s):

Zhiyong Liu ◽

Thomas Owen ◽

Jie Fang ◽

R. Sathish Srinivasan ◽

Jian Zuo

Keyword(s):

Hair Cell ◽

Hair Cells ◽

Cell Maturation ◽

Cochlear Hair Cells ◽

Prox1 Expression

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Umbilical Cord Mesenchymal Stromal Cell-Derived Exosomes Rescue the Loss of Outer Hair Cells and Repair Cochlear Damage in Cisplatin-Injected Mice

International Journal of Molecular Sciences ◽

10.3390/ijms22136664 ◽

2021 ◽

Vol 22 (13) ◽

pp. 6664

Author(s):

Stella Chin-Shaw Tsai ◽

Kuender D. Yang ◽

Kuang-Hsi Chang ◽

Frank Cheau-Feng Lin ◽

Ruey-Hwang Chou ◽

...

Keyword(s):

Hearing Loss ◽

Umbilical Cord ◽

Hair Cells ◽

Round Window ◽

Outer Hair Cells ◽

Protective Effects ◽

Cochlear Hair Cells ◽

Potential Applications ◽

Round Window Niche

Umbilical cord-derived mesenchymal stromal cells (UCMSCs) have potential applications in regenerative medicine. UCMSCs have been demonstrated to repair tissue damage in many inflammatory and degenerative diseases. We have previously shown that UCMSC exosomes reduce nerve injury-induced pain in rats. In this study, we characterized UCMSC exosomes using RNA sequencing and proteomic analyses and investigated their protective effects on cisplatin-induced hearing loss in mice. Two independent experiments were designed to investigate the protective effects on cisplatin-induced hearing loss in mice: (i) chronic intraperitoneal cisplatin administration (4 mg/kg) once per day for 5 consecutive days and intraperitoneal UCMSC exosome (1.2 μg/μL) injection at the same time point; and (ii) UCMSC exosome (1.2 μg/μL) injection through a round window niche 3 days after chronic cisplatin administration. Our data suggest that UCMSC exosomes exert protective effects in vivo. The post-traumatic administration of UCMSC exosomes significantly improved hearing loss and rescued the loss of cochlear hair cells in mice receiving chronic cisplatin injection. Neuropathological gene panel analyses further revealed the UCMSC exosomes treatment led to beneficial changes in the expression levels of many genes in the cochlear tissues of cisplatin-injected mice. In conclusion, UCMSC exosomes exerted protective effects in treating ototoxicity-induced hearing loss by promoting tissue remodeling and repair.

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A015 In situ therapy can induce regeneration of cochlear hair cells in vivo

International Journal of Pediatric Otorhinolaryngology ◽

10.1016/s0165-5876(11)70016-7 ◽

2011 ◽

Vol 75 ◽

pp. 3

Author(s):

C. La Croix ◽

E. Mornet ◽

T. Montier ◽

G. Valette ◽

G. Potard ◽

...

Keyword(s):

Hair Cells ◽

Cochlear Hair Cells

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Calcium Balance and Mechanotransduction in Rat Cochlear Hair Cells

Journal of Neurophysiology ◽

10.1152/jn.00019.2010 ◽

2010 ◽

Vol 104 (1) ◽

pp. 18-34 ◽

Cited By ~ 62

Author(s):

Maryline Beurg ◽

Jong-Hoon Nam ◽

Qingguo Chen ◽

Robert Fettiplace

Keyword(s):

Time Constant ◽

Hair Cells ◽

Pump Current ◽

Outer Hair Cells ◽

Hair Bundle ◽

Calcium Balance ◽

Cochlear Hair Cells ◽

Fluorescent Indicators ◽

Intracellular Ca

Auditory transduction occurs by opening of Ca2+-permeable mechanotransducer (MT) channels in hair cell stereociliary bundles. Ca2+ clearance from bundles was followed in rat outer hair cells (OHCs) using fast imaging of fluorescent indicators. Bundle deflection caused a rapid rise in Ca2+ that decayed after the stimulus, with a time constant of about 50 ms. The time constant was increased by blocking Ca2+ uptake into the subcuticular plate mitochondria or by inhibiting the hair bundle plasma membrane Ca2+ ATPase (PMCA) pump. Such manipulations raised intracellular Ca2+ and desensitized the MT channels. Measurement of the electrogenic PMCA pump current, which saturated at 18 pA with increasing Ca2+ loads, indicated a maximum Ca2+ extrusion rate of 3.7 fmol·s−1. The amplitude of the Ca2+ transient decreased in proportion to the Ca2+ concentration bathing the bundle and in artificial endolymph (160 mM K+, 20 μM Ca2+), Ca2+ carried 0.2% of the MT current. Nevertheless, MT currents in endolymph displayed fast adaptation with a submillisecond time constant. In endolymph, roughly 40% of the MT current was activated at rest when using 1 mM intracellular BAPTA compared with 12% with 1 mM EGTA, which enabled estimation of the in vivo Ca2+ load as 3 pA at rest. The results were reproduced by a model of hair bundle Ca2+ diffusion, showing that the measured PMCA pump density could handle Ca2+ loads incurred from resting and maximal MT currents in endolymph. The model also indicated the endogenous mobile buffer was equivalent to 1 mM BAPTA.

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Ouabain-Induced Apoptosis in Cochlear Hair Cells and Spiral Ganglion NeuronsIn Vitro

BioMed Research International ◽

10.1155/2013/628064 ◽

2013 ◽

Vol 2013 ◽

pp. 1-16 ◽

Cited By ~ 14

Author(s):

Yong Fu ◽

Dalian Ding ◽

Lei Wei ◽

Haiyan Jiang ◽

Richard Salvi

Keyword(s):

Hair Cells ◽

Gene Array ◽

Spiral Ganglion ◽

Spiral Ganglion Neuron ◽

Round Window Membrane ◽

Spiral Ganglion Neurons ◽

Cochlear Hair Cells ◽

Ganglion Neurons

Ouabain is a common tool to explore the pathophysiological changes in adult mammalian cochleain vivo. In prior studies, locally administering ouabain via round window membrane demonstrated that the ototoxic effects of ouabainin vivovaried among mammalian species. Little is known about the ototoxic effectsin vitro. Thus, we prepared cochlear organotypic cultures from postnatal day-3 rats and treated these cultures with ouabain at 50, 500, and 1000 μM for different time to elucidate the ototoxic effects of ouabainin vitroand to provide insights that could explain the comparative ototoxic effects of ouabainin vivo. Degeneration of cochlear hair cells and spiral ganglion neurons was evaluated by hair-cell staining and neurofilament labeling, respectively. Annexin V staining was used to detect apoptotic cells. A quantitative RT-PCR apoptosis-focused gene array determined changes in apoptosis-related genes. The results showed that ouabain-induced damagein vitrowas dose and time dependent. 500 μM ouabain and 1000 μM ouabain were destructively traumatic to both spiral ganglion neurons and cochlear hair cells in an apoptotic signal-dependent pathway. The major apoptotic pathways in ouabain-induced spiral ganglion neuron apoptosis culminated in the stimulation of the p53 pathway and triggering of apoptosis by a network of proapoptotic signaling pathways.

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