201
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Huang M, Sage C, Li H, Xiang M, Heller S, Chen ZY. Diverse expression patterns of LIM-homeodomain transcription factors (LIM-HDs) in mammalian inner ear development. Dev Dyn 2009; 237:3305-12. [PMID: 18942141 DOI: 10.1002/dvdy.21735] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
LIM-homeodomain transcription factors (LIM-HDs) are essential in tissue patterning and differentiation. But their expression patterns in the inner ear are largely unknown. Here we report on a study of twelve LIM-HDs, by their tempo-spatial patterns that imply distinct yet overlapping roles, in the developing mouse inner ear. Expression of Lmx1a and Isl1 begins in the otocyst stage, with Lmx1a exclusively in the non-sensory and Isl1 in the prosensory epithelia. The second wave of expression at E12.5 includes Lhx3, 5, 9, Isl2, and Lmx1b in the differentiating sensory epithelia with cellular specificities. With the exception of Lmx1a and Lhx3, all LIM-HDs are expressed in ganglion neurons. Expression of multiple LIM-HDs within a cell type suggests their redundant function.
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Affiliation(s)
- Mingqian Huang
- Eaton-Peabody Laboratory, Massachusetts Eye and Ear Infirmary and Department of Otology and Laryngology, Harvard Medical School, Boston, Massachusetts 02114, USA
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202
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Richardson RT, Wise AK, Andrew JK, O'Leary SJ. Novel drug delivery systems for inner ear protection and regeneration after hearing loss. Expert Opin Drug Deliv 2009; 5:1059-76. [PMID: 18817513 DOI: 10.1517/17425247.5.10.1059] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
BACKGROUND A cochlear implant, the only current treatment for restoring auditory perception after severe or profound sensorineural hearing loss (SNHL), works by electrically stimulating spiral ganglion neurons (SGNs). However, gradual degeneration of SGNs associated with SNHL can compromise the efficacy of the device. OBJECTIVE To review novel drug delivery systems for preserving and/or regenerating sensory cells in the cochlea after SNHL. METHODS The effectiveness of traditional cochlear drug delivery systems is compared to newer techniques such as cell, polymer and gene transfer technologies. Special requirements for local drug delivery to the cochlea are discussed, such as protecting residual hearing and site-specific drug delivery for cell preservation and regeneration. RESULTS/CONCLUSIONS Drug delivery systems with the potential for immediate clinical translation, as well as those that will contribute to the future of hearing preservation or cochlear cellular regeneration, are identified.
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Affiliation(s)
- Rachael T Richardson
- Bionic Ear Institute, 384 Albert Street, East Melbourne, Victoria 3002, Australia.
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203
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Abstract
PURPOSE OF REVIEW Treatment of auditory and vestibular dysfunction has become increasingly dependent on inner ear drug delivery. Recent advances in molecular therapy and nanotechnology have pushed development of alternate delivery methodologies involving both transtympanic and direct intracochlear infusions. This review examines recent developments in the field relevant to both clinical and animal research environments. RECENT FINDINGS Transtympanic delivery of gentamicin and corticosteroids for the treatment of Meniere's disease and sudden sensorineural hearing loss continues to be clinically relevant, with understanding of pharmacokinetics becoming more closely studied. Stabilizing matrices placed on the round window membrane for sustained passive delivery of compounds offer more controlled dosing profiles than transtympanic injections. Nanoparticles are capable of traversing the round window membrane and cochlear membranous partitions, and may become useful gene delivery platforms. Cochlear and vestibular hair cell regeneration has been demonstrated by vector delivery to the inner ear, offering promise for future advanced therapies. SUMMARY Optimal methods of inner ear drug delivery will depend on toxicity, therapeutic dose range, and characteristics of the agent to be delivered. Advanced therapy development will likely require direct intracochlear delivery with detailed understanding of associated pharmacokinetics.
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204
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Lin J, Feng L, Hamajima Y, Komori M, Burns TC, Fukudome S, Anderson J, Wang D, Verfaillie CM, Low WC. Directed differentiation of mouse cochlear neural progenitors in vitro. Am J Physiol Cell Physiol 2008; 296:C441-52. [PMID: 19261910 DOI: 10.1152/ajpcell.00324.2008] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Multipotent cochlear neural progenitors (CNPs) in the organ of Corti hold the promise for cell replacement in degenerative hearing disorders. However, not much is known about the CNPs and the specific conditions for their differentiation. Here we isolate the CNPs from the postnatal day 1 organ of Corti in mice and demonstrate their capability to self-renew and to differentiate into hair cell-like and neuronal cell-like phenotypes under the guidance of sonic hedgehog (SHH), epidermal growth factor (EGF), retinoic acid (RA), and brain-derived neurotrophic factor (BDNF), herein termed SERB (abbreviation of SHH, EGF, RA, and BDNF) in an asymmetric or symmetric manner from clonal isolates. Differentiation of CNPs into hair cells by SERB was dependent on the ERK signaling pathway, whereas the differentiation of CNPs into neurons by SERB was not. This work develops a new in vitro methodology for the maintenance and self-regeneration of CNPs for future design of regenerative strategies for hearing disorders.
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Affiliation(s)
- Jizhen Lin
- Department of Otolaryngology, 216 Lions Research Bldg., Univ. of Minnesota, 2001 Sixth St. S.E., Minneapolis, MN 55455, USA.
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205
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Swan EEL, Mescher MJ, Sewell WF, Tao SL, Borenstein JT. Inner ear drug delivery for auditory applications. Adv Drug Deliv Rev 2008; 60:1583-99. [PMID: 18848590 PMCID: PMC2657604 DOI: 10.1016/j.addr.2008.08.001] [Citation(s) in RCA: 144] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2008] [Accepted: 08/21/2008] [Indexed: 02/07/2023]
Abstract
Many inner ear disorders cannot be adequately treated by systemic drug delivery. A blood-cochlear barrier exists, similar physiologically to the blood-brain barrier, which limits the concentration and size of molecules able to leave the circulation and gain access to the cells of the inner ear. However, research in novel therapeutics and delivery systems has led to significant progress in the development of local methods of drug delivery to the inner ear. Intratympanic approaches, which deliver therapeutics to the middle ear, rely on permeation through tissue for access to the structures of the inner ear, whereas intracochlear methods are able to directly insert drugs into the inner ear. Innovative drug delivery systems to treat various inner ear ailments such as ototoxicity, sudden sensorineural hearing loss, autoimmune inner ear disease, and for preserving neurons and regenerating sensory cells are being explored.
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Affiliation(s)
- Erin E Leary Swan
- Charles Stark Draper Laboratory, 555 Technology Square, Cambridge, MA 02139, USA.
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206
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Yuan Z, Suo–qiang Z, Wei S, Wei G, Gui–liang Z, Yin–yan H. Retrovirus–Mediated Gene Transfer in Immortalization of Progenitor Hair Cell Lines in Newborn Rat. J Otol 2008. [DOI: 10.1016/s1672-2930(08)50021-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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207
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Matsumoto M, Nakagawa T, Kojima K, Sakamoto T, Fujiyama F, Ito J. Potential of embryonic stem cell-derived neurons for synapse formation with auditory hair cells. J Neurosci Res 2008; 86:3075-85. [DOI: 10.1002/jnr.21754] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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208
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Konishi M, Kawamoto K, Izumikawa M, Kuriyama H, Yamashita T. Gene transfer into guinea pig cochlea using adeno-associated virus vectors. J Gene Med 2008; 10:610-8. [PMID: 18338819 DOI: 10.1002/jgm.1189] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
BACKGROUND Several genes are candidates for treating inner ear diseases. For clinical applications, minimally invasive approaches to the inner ear are desirable along with minimal side-effects. METHODS Adeno-associated virus (AAV) was used as a vector into the guinea pig inner ear. Six AAV-cytomegalovirus hybrids (AAV-2/1, -2/2, -2/5, -2/7, -2/8 and -2/9) were infused into perilymph of the cochlea basal turn, an approach that could be used in cochlear implant surgery. At 7 days after injection, distribution of gene expression, hearing and morphology were evaluated. Adenoviral vector was also used to compare distributions of gene expression. Moreover, distribution of cell surface receptors of AAV in the cochlea was examined using immunohistochemistry. RESULTS Using the perilymphatic approach, adenovirus could be transferred to mesothelial cells lining the perilymph, but not sensory cells. Conversely, all AAV serotypes displayed tissue tropism to inner hair cells, with AAV-2/2 showing particularly efficient transfer to sensory cells. This tissue tropism of AAV could not be explained by the distribution of AAV receptors. Hearing and morphology were largely unaffected. CONCLUSIONS Our results indicate that AAV vector can be safely applied to the inner ear and AAV-2/2 offers a good tool for transferring transgenes into sensory cells of the inner ear efficiently without toxicity.
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Affiliation(s)
- Masaya Konishi
- Departments of Otolaryngology and Head-Neck Surgery, Kansai Medical University, Moriguchi, Osaka, Japan.
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209
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210
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Kawamoto K, Izumikawa M, Beyer LA, Atkin GM, Raphael Y. Spontaneous hair cell regeneration in the mouse utricle following gentamicin ototoxicity. Hear Res 2008; 247:17-26. [PMID: 18809482 DOI: 10.1016/j.heares.2008.08.010] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/22/2008] [Accepted: 08/22/2008] [Indexed: 10/21/2022]
Abstract
Whereas most epithelial tissues turn-over and regenerate after a traumatic lesion, this restorative ability is diminished in the sensory epithelia of the inner ear; it is absent in the cochlea and exists only in a limited capacity in the vestibular epithelium. The extent of regeneration in vestibular hair cells has been characterized for several mammalian species including guinea pig, rat, and chinchilla, but not yet in mouse. As the fundamental model species for investigating hereditary disease, the mouse can be studied using a wide variety of genetic and molecular tools. To design a mouse model for vestibular hair cell regeneration research, an aminoglycoside-induced method of complete hair cell elimination was developed in our lab and applied to the murine utricle. Loss of utricular hair cells was observed using scanning electron microscopy, and corroborated by a loss of fluorescent signal in utricles from transgenic mice with GFP-positive hair cells. Regenerative capability was characterized at several time points up to six months following insult. Using scanning electron microscopy, we observed that as early as two weeks after insult, a few immature hair cells, demonstrating the characteristic immature morphology indicative of regeneration, could be seen in the utricle. As time progressed, larger numbers of immature hair cells could be seen along with some mature cells resembling surface morphology of type II hair cells. By six months post-lesion, numerous regenerated hair cells were present in the utricle, however, neither their number nor their appearance was normal. A BrdU assay suggested that at least some of the regeneration of mouse vestibular hair cells involved mitosis. Our results demonstrate that the vestibular sensory epithelium in mice can spontaneously regenerate, elucidate the time course of this process, and identify involvement of mitosis in some cases. These data establish a road map of the murine vestibular regenerative process, which can be used for elucidating the molecular events that govern this process.
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Affiliation(s)
- Kohei Kawamoto
- Department of Otolaryngology, Kansai Medical University, 10-15 Fumizono-cho, Moriguchi, Osaka 570-8506, Japan
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211
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212
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Cotanche DA. Genetic and pharmacological intervention for treatment/prevention of hearing loss. JOURNAL OF COMMUNICATION DISORDERS 2008; 41:421-443. [PMID: 18455177 PMCID: PMC2574670 DOI: 10.1016/j.jcomdis.2008.03.004] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2008] [Accepted: 03/12/2008] [Indexed: 05/26/2023]
Abstract
UNLABELLED Twenty years ago it was first demonstrated that birds could regenerate their cochlear hair cells following noise damage or aminoglycoside treatment. An understanding of how this structural and functional regeneration occurred might lead to the development of therapies for treatment of sensorineural hearing loss in humans. Recent experiments have demonstrated that noise exposure and aminoglycoside treatment lead to apoptosis of the hair cells. In birds, this programmed cell death induces the adjacent supporting cells to undergo regeneration to replace the lost hair cells. Although hair cells in the mammalian cochlea undergo apoptosis in response to noise damage and ototoxic drug treatment, the supporting cells do not possess the ability to undergo regeneration. However, current experiments on genetic manipulation, gene therapy, and stem cell transplantation suggest that regeneration in the mammalian cochlea may eventually be possible and may 1 day provide a therapeutic tool for hearing loss in humans. LEARNING OUTCOMES The reader should be able to: (1) Describe the anatomy of the avian and mammalian cochlea, identify the individual cell types in the organ of Corti, and distinguish major features that participate in hearing function, (2) Demonstrate a knowledge of how sound damage and aminoglycoside poisoning induce apoptosis of hair cells in the cochlea, (3) Define how hair cell loss in the avian cochlea leads to regeneration of new hair cells and distinguish this from the mammalian cochlea where there is no regeneration following damage, and (4) Interpret the potential for new approaches, such as genetic manipulation, gene therapy and stem cell transplantation, could provide a therapeutic approach to hair cell loss in the mammalian cochlea.
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MESH Headings
- Aminoglycosides/toxicity
- Animals
- Apoptosis/drug effects
- Apoptosis/genetics
- Apoptosis/physiology
- Birds
- Cell Proliferation/drug effects
- Genetic Therapy
- Guinea Pigs
- Hair Cells, Auditory/drug effects
- Hair Cells, Auditory/pathology
- Hair Cells, Auditory/physiology
- Hearing Loss, Noise-Induced/pathology
- Hearing Loss, Noise-Induced/physiopathology
- Hearing Loss, Noise-Induced/therapy
- Hearing Loss, Sensorineural/pathology
- Hearing Loss, Sensorineural/physiopathology
- Hearing Loss, Sensorineural/therapy
- Humans
- Mice
- Mice, Knockout
- Microscopy, Confocal
- Nerve Regeneration/drug effects
- Nerve Regeneration/genetics
- Nerve Regeneration/physiology
- Organ of Corti/drug effects
- Organ of Corti/pathology
- Organ of Corti/physiopathology
- Stem Cell Transplantation
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Affiliation(s)
- Douglas A Cotanche
- Laboratory of Cellular and Molecular Hearing Research, Department of Otolaryngology, Children's Hospital Boston, Boston, MA, USA.
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213
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Gubbels SP, Woessner DW, Mitchell JC, Ricci AJ, Brigande JV. Functional auditory hair cells produced in the mammalian cochlea by in utero gene transfer. Nature 2008; 455:537-41. [PMID: 18754012 DOI: 10.1038/nature07265] [Citation(s) in RCA: 199] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2008] [Accepted: 07/17/2008] [Indexed: 02/07/2023]
Abstract
Sensory hair cells in the mammalian cochlea convert mechanical stimuli into electrical impulses that subserve audition. Loss of hair cells and their innervating neurons is the most frequent cause of hearing impairment. Atonal homologue 1 (encoded by Atoh1, also known as Math1) is a basic helix-loop-helix transcription factor required for hair-cell development, and its misexpression in vitro and in vivo generates hair-cell-like cells. Atoh1-based gene therapy to ameliorate auditory and vestibular dysfunction has been proposed. However, the biophysical properties of putative hair cells induced by Atoh1 misexpression have not been characterized. Here we show that in utero gene transfer of Atoh1 produces functional supernumerary hair cells in the mouse cochlea. The induced hair cells display stereociliary bundles, attract neuronal processes and express the ribbon synapse marker carboxy-terminal binding protein 2 (refs 12,13). Moreover, the hair cells are capable of mechanoelectrical transduction and show basolateral conductances with age-appropriate specializations. Our results demonstrate that manipulation of cell fate by transcription factor misexpression produces functional sensory cells in the postnatal mammalian cochlea. We expect that our in utero gene transfer paradigm will enable the design and validation of gene therapies to ameliorate hearing loss in mouse models of human deafness.
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Affiliation(s)
- Samuel P Gubbels
- Department of Otolaryngology, Oregon Hearing Research Center, Portland, Oregon 97239, USA
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214
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Zou D, Erickson C, Kim EH, Jin D, Fritzsch B, Xu PX. Eya1 gene dosage critically affects the development of sensory epithelia in the mammalian inner ear. Hum Mol Genet 2008; 17:3340-56. [PMID: 18678597 DOI: 10.1093/hmg/ddn229] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Haploinsufficiency of the transcription co-activator EYA1 causes branchio-oto-renal syndrome, congenital birth defects that account for as many as 2% of profoundly deaf children; however, the underlying cause for its dosage requirement and its specific role in sensory cell development of the inner ear are unknown. Here, an allelic series of Eya1 were generated to study the basis of Eya1 dosage requirements for sensory organ development. Our results show different threshold requirements for the level of Eya1 in different regions of the inner ear. Short and disorganized hair cell sterocilia was observed in wild-type/null heterozygous or hypomorphic/hypomorphic homozygous cochleae. Patterning and gene-marker analyses indicate that in Eya1 hypomorphic/null heterozygous mice, a reduction of Eya1 expression to 21% of normal level causes an absence of cochlear and vestibular sensory formation. Eya1 is initially expressed in the progenitors throughout the epithelium of all six sensory regions, and later on during sensory cell differentiation, its expression becomes restricted to the differentiating hair cells. We provide genetic evidence that Eya1 activity, in a concentration-dependent manner, plays a key role in the regulation of genes known to be important for sensory development. Furthermore, we show that Eya1 co-localizes with Sox2 in the sensory progenitors and both proteins physically interact. Together, our results indicate that Eya1 appears to be upstream of very early events during the sensory organ development, hair cell differentiation and inner-ear patterning. These results also provide a molecular mechanism for understanding how hypomorphic levels of EYA1 cause inner-ear defects in humans.
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Affiliation(s)
- Dan Zou
- McLaughlin Research Institute for Biomedical Sciences, Great Falls, MT 59405, USA
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215
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Ectopic expression of tmie transgene induces various recovery levels of behavior and hearing ability in the circling mouse. Biochem Biophys Res Commun 2008; 374:17-21. [PMID: 18586001 DOI: 10.1016/j.bbrc.2008.06.064] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2008] [Accepted: 06/18/2008] [Indexed: 11/21/2022]
Abstract
The circling (cir/cir) mouse is one of the murine models for human non-syndromic deafness DFNB6. The mice have abnormal circling behavior, suggesting a balanced disorder and profound deafness. The causative gene was transmembrane inner ear (tmie) gene of which the mutation is a 40-kb genomic deletion including tmie gene itself. In this study, tmie-overexpression trasngenic mice were established. Individuals with germline transmission have been mated with circling homozygous mutant mice (cir/cir) in order to produce the transgenic mutant mice (cir/cir-tg) as a gene therapy. After the genotyping, phenotypic analyses were performed so that the insertion of the new gene might compensate for the diseases such as hearing loss, circling behavior, or swimming inability. Some individuals exhibited complete recovery in their behavior and hearing but the others did not show any amelioration in behavior or hearing. Individual mice had very different levels of tmie transgene expression in the cochlea. These results clearly indicate that tmie protein plays an important role when the appropriate expression level of tmie was expressed in the inner ear. The protein levels were variable in each individual and these are thought to induce the differences in disease amelioration levels.
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216
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Abstract
Transfer of exogenous genetic material into the mammalian inner ear using viral vectors has been characterized over the last decade. A number of different viral vectors have been shown to transfect the varying cell types of the nonprimate mammalian inner ear. Several routes of delivery have been identified for introduction of vectors into the inner ear while minimizing injury to existing structures and at the same time ensuring widespread distribution of the agent throughout the cochlea and the rest of the inner ear. These studies raise the possibility that gene transfer may be developed as a potential strategy for treating inner ear dysfunction in humans. Furthermore, a recent report showing successful transfection of excised human vestibular epithelia offers proof of principle that viral gene transfer is a viable strategy for introduction and expression of exogenous genetic material to restore function to the inner ear. Human vestibular epithelia were harvested from patients undergoing labyrinthectomy, either for intractable Ménière's disease or vestibular schwannoma resection, and cultured for as long as 5 days. In those experiments, recombinant, multiply-deleted, replication-deficient adenoviral vectors were used to transfect and express a reporter gene as well as the functionally relevant gene, wild-type KCNQ4, a potassium channel gene that when mutated causes the autosomal dominant HL DFNA2.Here, we review the current state of viral-mediated gene transfer in the inner ear and discuss different viral vectors, routes of delivery, and potential applications of gene therapy. Emphasis is placed on experiments demonstrating viral transfection of human inner ear tissue and implications of these findings and for the future of gene therapy in the human inner ear.
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217
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Wei C, Yin–yan H, Shi–ming Y, Wei G, Jian–he S, Dong–yi H, Suo–qiang Z, Wei–yan Y, Z.Z.He D. Adenoviral–mediated Hath1–EGFP gene transfer into guinea pig cochlea through intact round window membrane. J Otol 2008. [DOI: 10.1016/s1672-2930(08)50003-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022] Open
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218
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Li–dong Z, Jun L, Yin–yan H, Jian–he S, Shi–ming Y. Supporting Cells–a New Area in Cochlear Physiology Study. J Otol 2008. [DOI: 10.1016/s1672-2930(08)50002-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022] Open
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219
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Seelman KD, Palmer CV, Ortmann A, Mormer E, Guthrie O, Miele J, Brabyn J. Quality-of-life technology for vision and hearing loss. IEEE ENGINEERING IN MEDICINE AND BIOLOGY MAGAZINE : THE QUARTERLY MAGAZINE OF THE ENGINEERING IN MEDICINE & BIOLOGY SOCIETY 2008; 27:40-55. [PMID: 18463020 DOI: 10.1109/emb.2007.907393] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Katherine D Seelman
- Department of Communication Science and Disorders, School of Health and Rehabilitation Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA.
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220
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Izumikawa M, Batts SA, Miyazawa T, Swiderski DL, Raphael Y. Response of the flat cochlear epithelium to forced expression of Atoh1. Hear Res 2008; 240:52-6. [PMID: 18430530 DOI: 10.1016/j.heares.2008.02.007] [Citation(s) in RCA: 98] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/22/2007] [Revised: 02/05/2008] [Accepted: 02/17/2008] [Indexed: 12/18/2022]
Abstract
Following hair cell elimination in severely traumatized cochleae, differentiated supporting cells are often replaced by a simple epithelium with cuboidal or flat appearance. Atoh1 (previously Math1) is a basic helix-loop-helix transcription factor critical to hair cell differentiation during mammalian embryogenesis. Forced expression of Atoh1 in the differentiated supporting cell population can induce transdifferentiation leading to hair cell regeneration. Here, we examined the outcome of adenovirus mediated over-expression of Atoh1 in the non-sensory cells of the flat epithelium. We determined that seven days after unilateral elimination of hair cells with neomycin, differentiated supporting cells are absent, replaced by a flat epithelium. Nerve processes were also missing from the auditory epithelium, with the exception of infrequent looping nerve processes above the habenula perforata. We then inoculated an adenovirus vector with Atoh1 insert into the scala media of the deafened cochlea. The inoculation resulted in upregulation of Atoh1 in the flat epithelium. However, two months after the inoculation, Atoh1-treated ears did not exhibit clear signs of hair cell regeneration. Combined with previous data on induction of supporting cell to hair cell transdifferentiation by forced expression of Atoh1, these results suggest that the presence of differentiated supporting cells in the organ of Corti is necessary for transdifferentiation to occur.
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Affiliation(s)
- Masahiko Izumikawa
- Kresge Hearing Research Institute, The University of Michigan Medical School, Ann Arbor, MI 48109-5648, USA
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221
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Pfannenstiel S, Praetorius M. [Protection and regeneration of sensory epithelia of the inner ear]. HNO 2008; 56:13-20. [PMID: 18210008 DOI: 10.1007/s00106-007-1631-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Dysfunctions of the inner ear such as hearing impairment due to noise exposure or presbycusis and vertigo are often caused by loss of hair cells in the sensory epithelium. There is still no specific therapy, just technical aids. Options for protecting and regenerating hair cells are explained here. The inhibition of apoptosis via caspases is presently the main target of research. They are involved in damage caused by aminoglycosides, cisplatin, or noise exposure. Bcl-2, growth factors, and oxidative stress are discussed. In regeneration the transdifferentiation of supporting cells to hair cells is explained. This can be achieved with local gene therapy using math1. Approach and media for the application are discussed, while viral vectors such as the adenovector seem the most promising in research.
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Affiliation(s)
- S Pfannenstiel
- Sektion Otologie und Neuro-Otologie, Hals-Nasen-Ohrenklinik,Universitätsklinikum, Im Neuenheimer Feld 400 , 69120, Heidelberg, Deutschland
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222
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Löwenheim H, Waldhaus J, Hirt B, Sandke S, Müller M. [Regenerative medicine in the treatment of sensorineural hearing loss]. HNO 2008; 56:288-300. [PMID: 18288464 DOI: 10.1007/s00106-008-1689-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Regenerative medicine offers the prospect of causal treatment of sensorineural hearing loss. In humans, the loss of sensory hair cells is irreversible and results in chronic hearing loss. Other vertebrates, particularly birds, have the capability to spontaneously regenerate lost sensory hair cells and restore hearing. In the bird model, regeneration of hair cells is based on the proliferation of supporting cells. In mammals, supporting cells have lost their proliferative capacity and are terminally differentiated. To gain an understanding about regeneration of hair cells in mammals, cell division of supporting cells has to be controlled. Gene disruption of the cell cycle inhibitor p27(Kip1) allows supporting cell proliferation in the organ of Corti in vivo. Furthermore, in vitro studies indicate that newly generated cells may differentiate into hair cells after p27(Kip1) disruption. Other current methods to induce hair cell regeneration include the gene transfer of Math1 and transplantation of stem cells to the inner ear.
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Affiliation(s)
- H Löwenheim
- Klinik für Hals-Nasen-Ohren-Heilkunde, Universitätsklinikum Tübingen, Elfriede-Aulhorn-Strasse 5, 72076 Tübingen, Deutschland.
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223
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Advances in Molecular and Cellular Therapies for Hearing Loss. Mol Ther 2008; 16:224-236. [DOI: 10.1038/sj.mt.6300351] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2007] [Accepted: 10/10/2007] [Indexed: 02/07/2023] Open
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Bogaerts S, Douglas S, Corlette T, Pau H, Saunders D, McKay S, Oleskevich S. Microsurgical access for cell injection into the mammalian cochlea. J Neurosci Methods 2008; 168:156-63. [DOI: 10.1016/j.jneumeth.2007.09.016] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2007] [Revised: 09/13/2007] [Accepted: 09/17/2007] [Indexed: 11/28/2022]
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225
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Abstract
Recent studies using explant cultures have demonstrated that pharmacological inhibition of Notch signaling by gamma-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 gamma-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.
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226
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Abstract
BACKGROUND Gene therapy may provide a way to restore cochlear function to deaf patients. The most successful techniques for cochlear gene therapy have been injection of early-generation adenoviral vectors into scala media in guinea pigs. However, it is important to be able to perform gene therapy research in mice because there is wide availability of transgenic strains with hereditary hearing loss. PURPOSE We demonstrate our technique for delivery of a third-generation adenoviral vector, helper-dependent adenovirus (HDAd), to the adult mouse cochlea. METHODS Mice were injected with an HDAd that contained a reporter gene for either beta-galactosidase or green fluorescent protein into scala media. After 4 days, the cochleae were harvested for analyses. Auditory brainstem response monitoring of cochlear function was performed before making a cochleostomy, after making a cochleostomy, and before killing the animal. RESULTS Beta-galactosidase was identified in the spiral ligament, the organ of Corti, and spiral ganglion cells by light microscopy. Green fluorescent protein epifluorescence was assessed in whole-mount organ of Corti preparations using confocal microscopy. This demonstrated transduction of inner hair cells, outer hair cells, and supporting cells. Paraffin-embedded cross sections similarly revealed gene transduction within the organ of Corti. Threshold shifts of 39.8 +/- 5.4 and 37.7 +/- 5.5 dB were observed in mice injected with HDAd or control buffer, respectively. CONCLUSION The technique of scala media HDAd injection reliably infects the adult mouse cochlea, including cells within the organ of Corti, although the procedure itself adversely affects hearing.
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227
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Ozeki H, Oshima K, Senn P, Kurihara H, Kaga K. Development and regeneration of hair cells. Acta Otolaryngol 2007:38-44. [PMID: 18340569 DOI: 10.1080/03655230701597200] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The vertebrate inner ear is derived from the otic placode and undergoes a complicated series of morphogenetic processes to differentiate into an elaborate structure harboring mechanosensory epithelia featuring hair cells, the mechanoreceptors of hearing and balance. Recently, the principal mechanisms producing hair cells and the key molecules involved in their fate determination and differentiation have been gradually unveiled. The in-depth understanding of hair cell development is consequently providing clues to strategies for mammalian hair cell regeneration. Among them, the identification and characterization of progenitor cells for the hair cell lineage, which is just emerging, is of particular interest. Herein, we review the molecular mechanisms of inner ear development with particular focus on perspectives for hair cell regeneration.
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228
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Qian D, Radde-Gallwitz K, Kelly M, Tyrberg B, Kim J, Gao WQ, Chen P. Basic helix-loop-helix gene Hes6 delineates the sensory hair cell lineage in the inner ear. Dev Dyn 2007; 235:1689-700. [PMID: 16534784 PMCID: PMC2810659 DOI: 10.1002/dvdy.20736] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
The basic helix-loop-helix (bHLH) gene Hes6 is known to promote neural differentiation in vitro. Here, we report the expression and functional studies of Hes6 in the inner ear. The expression of Hes6 appears to be parallel to that of Math1 (also known as Atoh1), a bHLH gene necessary and sufficient for hair cell differentiation. Hes6 is expressed initially in the presumptive hair cell precursors in the cochlea. Subsequently, the expression of Hes6 is restricted to morphologically differentiated hair cells. Similarly, the expression of Hes6 in the vestibule is in the hair cell lineage. Hes6 is dispensable for hair cell differentiation, and its expression in inner ear hair cells is abolished in the Math1-null animals. Furthermore, the introduction of Hes6 into the cochlea in vitro is not sufficient to promote sensory or neuronal differentiation. Therefore, Hes6 is downstream of Math1 and its expression in the inner ear delineates the sensory lineage. However, the role of Hes6 in the inner ear remains elusive.
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Affiliation(s)
- Dong Qian
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA 30322
| | | | - Michael Kelly
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA 30322
| | | | - Jaesang Kim
- Division of Molecular Life Sciences, Ewha Womans University, Seoul, Korea
| | - Wei-Qiang Gao
- Department of Molecular Biology Genentech South San Francisco, CA 94080
| | - Ping Chen
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA 30322
- Author for correspondence: , 404 727-1808 (Tel), 404 727-6256 (Fax)
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229
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Kharlamova A, Aarts NL. A Review of Past and Present Hair Cell Regeneration Techniques. ACTA ACUST UNITED AC 2007. [DOI: 10.1044/cicsd_34_f_134] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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230
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Ladrech S, Wang J, Simonneau L, Puel JL, Lenoir M. Macrophage contribution to the response of the rat organ of Corti to amikacin. J Neurosci Res 2007; 85:1970-9. [PMID: 17497672 DOI: 10.1002/jnr.21335] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Transdifferentiation of nonsensory supporting cells into sensory hair cells occurs naturally in the damaged avian inner ear. Such transdifferentiation was achieved experimentally in the cochlea of deaf guinea pigs through Atoh 1 gene transfection. Supporting cells may therefore serve as targets for transdifferentiation therapy. Supporting cells rapidly degenerate after hair cell disappearance, however, limiting the therapeutic window for gene transfer. We studied the time course of ultrastructural and phenotypical changes occurring in Deiters cells (hair cell supporting cells) after ototoxic treatment in the rat. The presence of macrophages in the cochlea was also investigated, to study any deleterious effects they may have on pathologic tissues. One week after treatment most hair cells had disappeared. Deiters cells no longer expressed the glial marker vimentin but instead displayed typical hair cell markers, the calcium binding proteins calbindin and parvalbumin. This suggests that a process of transdifferentiation of Deiters cells into hair cells was activated. By 3 weeks post-treatment, however, the Deiters cells began to degenerate and by 10 weeks post-treatment the organ of Corti was degraded fully. Interestingly, a marked increase in macrophage density was seen after the end of amikacin treatment to 10 weeks post-treatment. This suggests chronic inflammation is involved in epithelium degeneration. Consequently, early treatments with anti-inflammatory factors might promote supporting cell survival, thus improving the efficacy of more specific strategies aimed to regenerate hair cells from nonsensory cells.
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Affiliation(s)
- Sabine Ladrech
- INSERM, U.583, Laboratoire de Physiopathologie et Thérapie des Déficits Sensoriels et Moteurs, Montpellier, France
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231
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Breuskin I, Bodson M, Thelen N, Thiry M, Nguyen L, Belachew S, Lefebvre PP, Malgrange B. Strategies to regenerate hair cells: identification of progenitors and critical genes. Hear Res 2007; 236:1-10. [PMID: 17920797 DOI: 10.1016/j.heares.2007.08.007] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/05/2007] [Revised: 08/03/2007] [Accepted: 08/12/2007] [Indexed: 01/13/2023]
Abstract
Deafness commonly results from a lesion of the sensory cells and/or of the neurons of the auditory part of the inner ear. There are currently no treatments designed to halt or reverse the progression of hearing loss. A key goal in developing therapy for sensorineural deafness is the identification of strategies to replace lost hair cells. In amphibians and birds, a spontaneous post-injury regeneration of all inner ear sensory hair cells occurs. In contrast, in the mammalian cochlea, hair cells are only produced during embryogenesis. Many studies have been carried out in order to demonstrate the persistence of endogenous progenitors. The present review is first focused on the occurrence of spontaneous supernumerary hair cells and on nestin positive precursors found in the organ of Corti. A second approach to regenerating hair cells would be to find genes essential for their differentiation. This review will also focus on critical genes for embryonic hair cell formation such as the cell cycle related proteins, the Atoh1 gene and the Notch signaling pathway. Understanding mechanisms that underlie hair cell production is an essential prerequisite to defining therapeutic strategies to regenerate hair cells in the mature inner ear.
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Affiliation(s)
- Ingrid Breuskin
- Center for Cellular and Molecular Neurosciences, Developmental Neurobiology Unit, University of Liege, 4000 Liege, Belgium
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232
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Hume CR, Bratt DL, Oesterle EC. Expression of LHX3 and SOX2 during mouse inner ear development. Gene Expr Patterns 2007; 7:798-807. [PMID: 17604700 PMCID: PMC2043117 DOI: 10.1016/j.modgep.2007.05.002] [Citation(s) in RCA: 121] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2007] [Revised: 05/03/2007] [Accepted: 05/21/2007] [Indexed: 12/12/2022]
Abstract
A cascade of transcription factors is believed to regulate the coordinate differentiation of primordial inner ear cells into the subtypes of hair cells and supporting cells. While candidate genes involved in this process have been identified, the temporal and spatial patterns of expression of many of these have not been carefully described during the extended period of inner ear development and functional maturation. We systematically examined the expression of two such transcription factors, LHX3 and SOX2, from the time of hair cell terminal mitoses into adulthood. We show that LHX3 is expressed specifically in auditory and vestibular hair cells soon after terminal mitoses and persists into the adult in vestibular hair cells. While SOX2 expression is widespread in the inner ear sensory epithelia prior to hair cell differentiation, it has a unique pattern of expression in the mature auditory and vestibular organs.
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Affiliation(s)
- Clifford R Hume
- Department of Otolaryngology - Head and Neck Surgery, Virginia Merrill Bloedel Hearing Research Center, University of Washington, VMBHRC, CHDD, CD176, Box 357923, 1959 NE Pacific, Seattle, WA 98195, USA.
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233
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Abstract
Hearing loss is an etiologically diverse condition with many disease-related complications and major clinical, social, and quality of life implications. As the rate of acquired hearing loss secondary to environmental causes decreases and improvements in the diagnosis of abnormalities occur, the significance of genetic factors that lead to deafness increases. Advancements in molecular biology have led to improved detection and earlier intervention in patients with hearing loss. Subsequently, earlier implementation of educational services and cochlear implant technology in patients with profound hearing loss now results in superior communication skills and enhanced language development. The aim of this review is to provide a comprehensive framework underlying the causes of hearing impairment and to detail the clinical management for patients with hereditary hearing loss.
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Affiliation(s)
- Amit Kochhar
- Molecular Otolaryngology Research Laboratories, University of Iowa, Iowa City, Iowa 52242, USA
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234
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Liu JJ, Shin JH, Hyrc KL, Liu S, Lei D, Holley MC, Bao J. Stem cell therapy for hearing loss: Math1 overexpression in VOT-E36 cells. Otol Neurotol 2007; 27:414-21. [PMID: 16639283 DOI: 10.1097/00129492-200604000-00020] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
HYPOTHESIS VOT-E36 cells acquire mechanosensitivity after mammalian atonal homolog 1 (Math1) overexpression. BACKGROUND VOT-E36 cells are derived from a population of epithelial cells in the ventral region of the otocyst at embryonic Day 10.5, before hair cell differentiation. These cells express a number of specific molecular markers for hair cells under both proliferation and differentiation states. Overexpression of Math1 can convert nonsensory epithelial cells into hair cells in the cochlea. Based on this information, we tested whether VOT-E36 cells can be converted into hair cells by Math1 overexpression. METHODS Using reverse transcriptase-polymerase chain reaction-based analysis, we first compared the expression patterns of various molecular markers for hair cell development in VOT-E36 cells between proliferation and differentiation states, and also before and after overexpression of Math1. Subsequently, with a standard calcium imaging method, we examined whether VOT-E36 cells overexpressing Math1 could detect mechanical vibrations and activate spiral ganglion neurons in a coculture model. In addition, using confocal and scanning electron microscopes, we examined morphologic changes of VOT-E36 cells after Math1 overexpression. RESULTS Consistent with previous reports, this study has shown that VOT-E36 cells express a number of specific molecular markers for hair cells in both proliferation and differentiation states. Under appropriate culture conditions, Math1 is transiently expressed in this cell line during conditional differentiation. In VOT-E36 cells overexpressing Math1, the normal expression pattern of certain molecular markers for mature hair cells is partially restored. Interestingly, after coculture with spiral ganglion neurons, VOT-E36 cells overexpressing Math1 are able to respond to mechanical vibrations and activate spiral ganglion neurons. Possible molecular mechanisms underlying this novel finding have been explored. CONCLUSION Math1 overexpression can partially restore presumably downstream signaling cascades for normal hair cell differentiation in VOT-E36 cells, which are able to detect mechanical vibrations after being cocultured with spiral ganglion neurons.
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Affiliation(s)
- Jan-Jan Liu
- Department of Otolaryngology, Center for Aging, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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235
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Parker MA, Corliss DA, Gray B, Anderson JK, Bobbin RP, Snyder EY, Cotanche DA. Neural stem cells injected into the sound-damaged cochlea migrate throughout the cochlea and express markers of hair cells, supporting cells, and spiral ganglion cells. Hear Res 2007; 232:29-43. [PMID: 17659854 PMCID: PMC2032013 DOI: 10.1016/j.heares.2007.06.007] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/18/2007] [Revised: 06/06/2007] [Accepted: 06/08/2007] [Indexed: 11/27/2022]
Abstract
Most cases of hearing loss are caused by the death or dysfunction of one of the many cochlear cell types. We examined whether cells from a neural stem cell line could replace cochlear cell types lost after exposure to intense noise. For this purpose, we transplanted a clonal stem cell line into the scala tympani of sound damaged mice and guinea pigs. Utilizing morphological, protein expression and genetic criteria, stem cells were found with characteristics of both neural tissues (satellite, spiral ganglion, and Schwann cells) and cells of the organ of Corti (hair cells, supporting cells). Additionally, noise-exposed, stem cell-injected animals exhibited a small but significant increase in the number of satellite cells and Type I spiral ganglion neurons compared to non-injected noise-exposed animals. These results indicate that cells of this neural stem cell line migrate from the scala tympani to Rosenthal's canal and the organ of Corti. Moreover, they suggest that cells of this neural stem cell line may derive some information needed from the microenvironment of the cochlea to differentiate into replacement cells in the cochlea.
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Affiliation(s)
- Mark A Parker
- Department of Communication Sciences and Disorders, Emerson College, Boston, MA 02114, USA.
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236
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Minoda R, Izumikawa M, Kawamoto K, Zhang H, Raphael Y. Manipulating cell cycle regulation in the mature cochlea. Hear Res 2007; 232:44-51. [PMID: 17658230 PMCID: PMC2048570 DOI: 10.1016/j.heares.2007.06.005] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/28/2006] [Revised: 06/06/2007] [Accepted: 06/08/2007] [Indexed: 11/19/2022]
Abstract
Sensorineural hearing loss, which is often caused by degeneration of hair cells in the auditory epithelium, is permanent because lost hair cells are not replaced. Several conceptual approaches can be used to place new hair cells in the auditory epithelium. One possibility is to enhance proliferation of non-sensory cells that remain in the deaf ear and induce transdifferentiation of some of these cells into the hair cell phenotype. Several genes, including p27(Kip1), have been shown to regulate proliferation and differentiation in the developing auditory epithelium. The role of p27(Kip1) in the mature ear is not well characterized. We now show that p27(Kip1) is present in the nuclei of non-sensory cells of the mature auditory epithelium. We determined that forced expression of Skp2 using a recombinant adenovirus vector, resulted in presence of BrdU-positive cells in the auditory epithelium. When SKP2 over-expression was combined with forced expression of Atoh1, ectopic hair cells were found in the auditory epithelium in greater numbers than were seen with Atoh1 alone. Skp2 over-expression alone did not result in ectopic hair cells. These findings suggest that the p27(Kip1) protein remains in the mature auditory epithelium and therefore p27(Kip1) can serve as a target for gene manipulation. The data also suggest that induced proliferation, by itself, does not generate new hair cells in the cochlea.
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Affiliation(s)
- Ryosei Minoda
- Kresge Hearing Research Institute, The University of Michigan, MSRB 3, Rm. 9303, 1150 W. Medical Center Dr., Ann Arbor, MI 48109-0648, USA
- Department of Otolaryngology- Head and Neck Surgery, Kumamoto University School of Medicine, 1-1-1 Honjo Kumamoto 860-8556, Japan
| | - Masahiko Izumikawa
- Kresge Hearing Research Institute, The University of Michigan, MSRB 3, Rm. 9303, 1150 W. Medical Center Dr., Ann Arbor, MI 48109-0648, USA
- Department of Otolaryngology- Head and Neck Surgery, Kansai Medical University, 10-15 Fumizono-cho, Moriguchi, Osaka 570-8506, Japan
| | - Kohei Kawamoto
- Kresge Hearing Research Institute, The University of Michigan, MSRB 3, Rm. 9303, 1150 W. Medical Center Dr., Ann Arbor, MI 48109-0648, USA
- Department of Otolaryngology- Head and Neck Surgery, Kansai Medical University, 10-15 Fumizono-cho, Moriguchi, Osaka 570-8506, Japan
| | - Hui Zhang
- Department of Genetics, Yale University School of Medicine, 333 Cedar Street, P.O. Box 208005, New Haven, CT 06520-8005, USA
| | - Yehoash Raphael
- Kresge Hearing Research Institute, The University of Michigan, MSRB 3, Rm. 9303, 1150 W. Medical Center Dr., Ann Arbor, MI 48109-0648, USA
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237
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Kesser BW, Hashisaki GT, Fletcher K, Eppard H, Holt JR. An in vitro model system to study gene therapy in the human inner ear. Gene Ther 2007; 14:1121-31. [PMID: 17568767 PMCID: PMC2742230 DOI: 10.1038/sj.gt.3302980] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The confined fluid-filled labyrinth of the human inner ear presents an opportunity for introduction of gene therapy reagents designed to treat hearing and balance dysfunction. Here we present a novel model system derived from the sensory epithelia of human vestibular organs and show that the tissue can survive up to 5 days in vitro. We generated organotypic cultures from 26 human sensory epithelia excised at the time of labyrinthectomy for intractable Meniere's disease or vestibular schwannoma. We applied multiply deleted adenoviral vectors at titers between 10(5) and 10(8) viral particles/ml directly to the cultures for 4-24 h and examined the tissue 12-96 h post-transfection. We noted robust expression of the exogenous transgene, green fluorescent protein (GFP), in hair cells and supporting cells suggesting both were targets of adenoviral transfection. We also transfected cultures with a vector that carried the genes for GFP and KCNQ4, a potassium channel subunit that causes dominant-progressive hearing loss when mutated. We noted a positive correlation between GFP fluorescence and KCNQ4 immunolocalization. We conclude that our in vitro model system presents a novel and effective experimental paradigm for evaluation of gene therapy reagents designed to restore cellular function in patients who suffer from inner ear disorders.
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Affiliation(s)
- BW Kesser
- Department of Otolaryngology – Head and Neck Surgery, University of Virginia School of Medicine, Charlottesville, VA, USA
| | - GT Hashisaki
- Department of Otolaryngology – Head and Neck Surgery, University of Virginia School of Medicine, Charlottesville, VA, USA
| | - K Fletcher
- Department of Otolaryngology – Head and Neck Surgery, University of Virginia School of Medicine, Charlottesville, VA, USA
| | - H Eppard
- Department of Neuroscience, University of Virginia School of Medicine, Charlottesville, VA, USA
| | - JR Holt
- Department of Otolaryngology – Head and Neck Surgery, University of Virginia School of Medicine, Charlottesville, VA, USA
- Department of Neuroscience, University of Virginia School of Medicine, Charlottesville, VA, USA
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238
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Hawkins RD, Bashiardes S, Powder KE, Sajan SA, Bhonagiri V, Alvarado DM, Speck J, Warchol ME, Lovett M. Large scale gene expression profiles of regenerating inner ear sensory epithelia. PLoS One 2007; 2:e525. [PMID: 17565378 PMCID: PMC1888727 DOI: 10.1371/journal.pone.0000525] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2006] [Accepted: 05/23/2007] [Indexed: 12/29/2022] Open
Abstract
Loss of inner ear sensory hair cells (HC) is a leading cause of human hearing loss and balance disorders. Unlike mammals, many lower vertebrates can regenerate these cells. We used cross-species microarrays to examine this process in the avian inner ear. Specifically, changes in expression of over 1700 transcription factor (TF) genes were investigated in hair cells of auditory and vestibular organs following treatment with two different damaging agents and regeneration in vitro. Multiple components of seven distinct known signaling pathways were clearly identifiable: TGFbeta, PAX, NOTCH, WNT, NFKappaB, INSULIN/IGF1 and AP1. Numerous components of apoptotic and cell cycle control pathways were differentially expressed, including p27(KIP) and TFs that regulate its expression. A comparison of expression trends across tissues and treatments revealed identical patterns of expression that occurred at identical times during regenerative proliferation. Network analysis of the patterns of gene expression in this large dataset also revealed the additional presence of many components (and possible network interactions) of estrogen receptor signaling, circadian rhythm genes and parts of the polycomb complex (among others). Equal numbers of differentially expressed genes were identified that have not yet been placed into any known pathway. Specific time points and tissues also exhibited interesting differences: For example, 45 zinc finger genes were specifically up-regulated at later stages of cochlear regeneration. These results are the first of their kind and should provide the starting point for more detailed investigations of the role of these many pathways in HC recovery, and for a description of their possible interactions.
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Affiliation(s)
- R. David Hawkins
- Division of Human Genetics, Department of Genetics, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Stavros Bashiardes
- Division of Human Genetics, Department of Genetics, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Kara E. Powder
- Division of Human Genetics, Department of Genetics, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Samin A. Sajan
- Division of Human Genetics, Department of Genetics, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Veena Bhonagiri
- Division of Human Genetics, Department of Genetics, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - David M. Alvarado
- Division of Human Genetics, Department of Genetics, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Judith Speck
- Department of Otolaryngology, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Mark E. Warchol
- Department of Otolaryngology, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Michael Lovett
- Division of Human Genetics, Department of Genetics, Washington University School of Medicine, St. Louis, Missouri, United States of America
- * To whom correspondence should be addressed. E-mail:
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239
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Hansen MR, Roehm PC, Xu N, Green SH. Overexpression of Bcl-2 or Bcl-xL prevents spiral ganglion neuron death and inhibits neurite growth. Dev Neurobiol 2007; 67:316-25. [PMID: 17443790 DOI: 10.1002/dneu.20346] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Spiral ganglion neurons (SGNs) provide afferent innervation to the cochlea and rely on contact with hair cells (HCs) for their survival. Following deafferentation due to hair cell loss, SGNs gradually die. In a rat culture model, we explored the ability of prosurvival members of the Bcl-2 family of proteins to support the survival and neurite outgrowth of SGNs. We found that overexpression of either Bcl-2 or Bcl-xL significantly increases SGN survival in the absence of neurotrophic factors, establishing that the Bcl-2 pathway is sufficient for SGN cell survival and that SGN deprived of trophic support die by an apoptotic mechanism. However, in contrast to observations in central neurons and PC12 cells where Bcl-2 appears to promote neurite growth, both Bcl-2 and Bcl-xL overexpression dramatically inhibit neurite outgrowth in SGNs. This inhibition of neurite growth by Bcl-2 occurs in nearly all SGNs even in the presence of multiple neurotrophic factors implying that Bcl-2 directly inhibits neurite growth rather than simply rescuing a subpopulation of neurons incapable of extending neurites without additional stimuli. Thus, although overexpression of prosurvival members of the Bcl-2 family prevents SGN loss following trophic factor deprivation, the inhibition of neurite growth by these molecules may limit their efficacy for support of auditory nerve maintenance or regeneration following hair cell loss.
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Affiliation(s)
- Marlan R Hansen
- Department of Otolaryngology, Head, and Neck Surgery, University of Iowa, Iowa City, Iowa 52242, USA.
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240
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Zhang Y, Zhai SQ, Shou J, Song W, Sun JH, Guo W, Zheng GL, Hu YY, Gao WQ. Isolation, growth and differentiation of hair cell progenitors from the newborn rat cochlear greater epithelial ridge. J Neurosci Methods 2007; 164:271-9. [PMID: 17583357 DOI: 10.1016/j.jneumeth.2007.05.009] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2007] [Revised: 05/09/2007] [Accepted: 05/10/2007] [Indexed: 11/15/2022]
Abstract
Mammalian cochlear hair cell loss is irreversible and leads to permanent hearing loss. To restore hearing physiologically, it is necessary to generate new functional hair cells either from endogenous cells or from exogenously transplanted hair cells/progenitors. Previous studies suggest that cochlear greater epithelial ridge (GER) and lesser epithelial ridge (LER) cells are capable of differentiating into hair cells. While it was recently possible to obtain and culture pure LER progenitors, isolation of pure GER progenitors has not been reported. Here we describe a method that allows isolation of pure GER cells from neonatal rat cochleae. The cochlear epithelial sheet (CES) containing GER progenitor cells was mechanically separated from the underlying mesenchymal tissue after digestion with thermolysin. The GER area could then be dissected following mechanical removal of organ of Corti as well as all the lateral area. The isolated GER cells showed significant proliferation and expressed markers for GER cells but not markers for hair cells or LER. When the GER cells were cultured in serum-free medium containing epidermal growth factor, spheres were formed where they continued to proliferate. Furthermore, when GER cells were induced to express Hath1 or co-cultured with mesenchymal cells prepared from neonate rat cochleae, they showed the potential to differentiate into hair cell-like cells. Successful isolation, culture and differentiation of GER hair cell progenitors will shed additional light on the mechanism of hair cell differentiation and potential hair cell replacement.
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Affiliation(s)
- Yuan Zhang
- Institute of Otolaryngology and Department of Otolaryngology, Head and Neck Surgery, Chinese PLA General Hospital, 28 Fuxing Road, Beijing 100853, China
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Cafaro J, Lee GS, Stone JS. Atoh1 expression defines activated progenitors and differentiating hair cells during avian hair cell regeneration. Dev Dyn 2007; 236:156-70. [PMID: 17096404 DOI: 10.1002/dvdy.21023] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
In the avian inner ear, nonsensory supporting cells give rise to new sensory hair cells through two distinct processes: mitosis and direct transdifferentiation. Regulation of supporting cell behavior and cell fate specification during avian hair cell regeneration is poorly characterized. Expression of Atoh1, a proneural transcription factor necessary and sufficient for developmental hair cell specification, was examined using immunofluorescence in quiescent and regenerating hair cell epithelia of mature chickens. In untreated birds, Atoh1 protein was not detected in the auditory epithelium, which is quiescent. In contrast, numerous Atoh1-positive nuclei were seen in the utricular macula, which undergoes continual hair cell turnover. Atoh1-positive nuclei emerged in the auditory epithelium by 15 hr post-ototoxin administration, before overt hair cell damage and supporting cell re-entry into the cell cycle. Subsequently, Atoh1 labeling was seen in 15% of dividing supporting cells. During cell division, Atoh1 was distributed symmetrically to daughter cells, but Atoh1 levels were dramatically regulated shortly thereafter. After cellular differentiation, Atoh1 labeling was confined to hair cells regenerated through either mitosis or direct transdifferentiation. However, Atoh1 expression in dividing progenitors did not necessarily predict hair cell fate specification in daughter cells. Finally, predominant modes of hair cell regeneration varied significantly across the radial axis of the auditory epithelium, with mitosis most frequent neurally and direct transdifferentiation most frequent abneurally. These observations suggest a role for Atoh1 in re-specifying supporting cells and in biasing postmitotic cells toward the hair cell fate during hair cell regeneration in the mature chicken ear.
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Affiliation(s)
- Jon Cafaro
- Virginia Merrill Bloedel Hearing Research Center, Department of Otolaryngology and Head and Neck Surgery, University of Washington, Seattle, Washington 98195-7923, USA
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242
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Praetorius M, Brunner C, Lehnert B, Klingmann C, Schmidt H, Staecker H, Schick B. Transsynaptic delivery of nanoparticles to the central auditory nervous system. Acta Otolaryngol 2007; 127:486-90. [PMID: 17453474 DOI: 10.1080/00016480600895102] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
CONCLUSION Silica nanoparticles may serve as a nonviral delivery system to the sensory hair cells, spiral ganglion cells within the cochlea, and the vestibular organ, as well as the cochlear nucleus. OBJECTIVES At present there are no targeted therapeutics for inner ear disease. A variety of viral vector systems have been tested in the inner ear with variable efficacy but they are still not regarded as safe systems for inner ear delivery. Nanoparticles are a nonviral method of delivering a variety of macromolecules that potentially can be used for delivery within the auditory system. In this study, we evaluated the distribution and safety of nanoparticles in the inner ear. MATERIALS AND METHODS Cy3-labeled silica nanoparticles were placed on the round window membrane of adult mice. Hearing thresholds were determined after nanoparticle delivery by auditory brainstem responses (ABRs). Distribution of particles was determined by histological evaluation of the cochlea, vestibular organs, and brain stem. RESULTS Fluorescent microscopy demonstrated Cy3-labeled nanoparticles signals in the sensory hair cells and the spiral ganglion neurons of both the treated and contralateral inner ears. Additionally, the distal part of the central auditory pathway (dorsal cochlear nucleus, superior olivary complex) was found to be labeled with the Cy3-linked silica nanoparticles, indicating a retrograde axonal transport. No hearing loss or inflammation was noted in the treated cochlea.
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Affiliation(s)
- Mark Praetorius
- Department of Otolaryngology, Head and Neck Surgery, University of Heidelberg Medical Center, Im Neuenheimer Feld 400, 69120 Heidelberg, Germany.
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243
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Staecker H, Praetorius M, Baker K, Brough DE. Vestibular hair cell regeneration and restoration of balance function induced by math1 gene transfer. Otol Neurotol 2007; 28:223-31. [PMID: 17255891 DOI: 10.1097/mao.0b013e31802b3225] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
HYPOTHESIS Delivery of math1 using an adenovector (Admath1.11D) results in vestibular hair cell regeneration and recovery of balance function in ototoxin-treated adult mice. BACKGROUND Loss of peripheral vestibular function is associated with disease processes such as vestibular neuronitis, aminoglycoside ototoxicity, and aging. Loss of vestibular hair cells is one of the mechanisms underlying balance dysfunction in all of these disorders. Currently, recovery from these diseases relies on central vestibular compensation rather than on local tissue recovery. Overexpression of the mammalian atonal homologue math1 has been demonstrated to induce generation of hair cells in neonatal organ of Corti cultures and in the guinea pig cochlea in vivo and could thus provide an approach to local tissue recovery. METHODS Admath1.11D was applied to cultures of aminoglycoside-treated macular organs or in vivo in a mouse aminoglycoside ototoxicity model. Outcome measures included histologic examination, immunohistochemistry, swim testing, and evaluation of the horizontal vestibulo-ocular reflex. RESULTS Delivery of math1 resulted in the generation of vestibular hair cells in vitro after aminoglycoside-mediated loss of hair cells. Math1-treated mice showed recovery of the vestibular neuroepithelium within 8 weeks after Admath1.11D treatment. Assessment of animals after vector infusion demonstrated a recovery of vestibular function compared with aminoglycoside-only-treated mice. CONCLUSION Molecular replacement of math1 may provide a therapeutic means of restoring vestibular function related to vestibular hair cell loss.
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Affiliation(s)
- Hinrich Staecker
- Otolaryngology Head and Neck Surgery, University of Kansas School of Medicine, Kansas City, Kansas 66160, USA.
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244
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Sekiya T, Kojima K, Matsumoto M, Holley MC, Ito J. Rebuilding lost hearing using cell transplantation. Neurosurgery 2007; 60:417-33; discussion 433. [PMID: 17327786 DOI: 10.1227/01.neu.0000249189.46033.42] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
OBJECTIVE The peripheral auditory nervous system (cochlea and auditory nerve) has a complex anatomy, and it has traditionally been thought that once the sensorineural structures are damaged, restoration of hearing is impossible. In the past decade, however, the potential to restore lost hearing has been intensively investigated using molecular and cell biological techniques, and we can now part with such a pessimistic view. In this review, we examine an important field in hearing restoration research: cell transplantation. METHODS Most efforts in this field have been directed to the replacement of hair cells by transplantation to the cochlea. Here, we focus on transplantation to the auditory nerve, from the side of the cerebellopontine angle rather than the cochlea. RESULTS Delivery of cells to the cochlea is potentially damaging, and nerve cells transplanted distally to the Schwann-glial transitional zone (cochlear side) may become inhibited when they reach the transitional zone. The auditory nerve is probably the most suitable route for cell transplantation. CONCLUSION The auditory nerve occupies an important position not only in neurosurgery but also in various diseases in other disciplines, and several lines of recent evidence indicate that it is a key target for hearing restoration. It is familiar to most neurosurgeons, and the recent advances in the molecular and cell biology of inner-ear development are of direct importance to neurorestorative medicine. In this article, we review the anatomy, development, and molecular biology of the auditory nerve and cochlea, with emphasis on the advances in cell transplantation.
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Affiliation(s)
- Tetsuji Sekiya
- Department of Otolaryngology, Kyoto University Graduate School of Medicine, Kyoto, Japan.
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245
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Du X, Jensen P, Goldowitz D, Hamre KM. Wild-type cells rescue genotypically Math1-null hair cells in the inner ears of chimeric mice. Dev Biol 2007; 305:430-8. [PMID: 17397818 DOI: 10.1016/j.ydbio.2007.02.028] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2006] [Revised: 02/05/2007] [Accepted: 02/21/2007] [Indexed: 11/15/2022]
Abstract
The transcription factor Math1 has been shown to be critical in the formation of hair cells (HCs) in the inner ear. However, the influence of environmental factors in HC specification suggests that cell extrinsic factors are also crucial to their development. To test whether extrinsic factors impact development of Math1-null (Math1(beta-Gal/beta-Gal)) HCs, we examined neonatal (postnatal ages P0-P4.5) Math1-null chimeric mice in which genotypically mutant and wild-type cells intermingle to form the inner ear. We provide the first direct evidence that Math1-null HCs are able to be generated and survive in the conducive chimeric environment. beta-Galactosidase expression was used to identify genetically mutant cells while cells were phenotypically defined as HCs by morphological characteristics notably the expression of HC-specific markers. Genotypically mutant HCs were found in all sensory epithelia of the inner ear at all ages examined. Comparable results were obtained irrespective of the wild-type component of the chimeric mice. Thus, genotypically mutant cells retain the competence to differentiate into HCs. The implication is that the lack of the Math1 gene in HC precursors can be overcome by environmental influences, such as cell-cell interactions with wild-type cells, to ultimately result in the formation of HCs.
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Affiliation(s)
- Xiaoping Du
- Department of Anatomy and Neurobiology, University of Tennessee Health Science Center, 855 Monroe Avenue, Room 515, Memphis, TN 38163, USA
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246
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Savary E, Hugnot JP, Chassigneux Y, Travo C, Duperray C, Van De Water T, Zine A. Distinct Population of Hair Cell Progenitors Can Be Isolated from the Postnatal Mouse Cochlea Using Side Population Analysis. Stem Cells 2007; 25:332-9. [PMID: 17038670 DOI: 10.1634/stemcells.2006-0303] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
In mammals, the permanence of hearing loss is due mostly to the incapacity of the cochlea to replace lost mechano-receptor cells (i.e., hair cells [HCs]). The generation of new HCs from a renewable source of progenitors is a principal requirement for developing a cell therapy within this sensory organ. A subset of stem cells, termed side population (SP), has been identified in several tissues of mammals. The ATP-binding cassette transporter Abcg2/Bcrp1 contributes to the specification of the SP phenotype and is proposed as a universal marker for stem/progenitor cells. A defining character of these SP cells is a high efflux capacity for Hoechst dye. Here, we demonstrate that Abcg2 transporter is expressed with two other stem/progenitor cell markers (i.e., Nestin and Musashi1) in distinct and overlapping domains of the supporting cells within the postnatal cochlea. We have developed and describe a fluorescence-activated cell sorting (FACS) technique that enables the purification of a discrete subpopulation of SP-supporting cells from the early postnatal mouse cochlea based on their ability to exclude Hoechst dye. These FACS-isolated cells can divide and express markers of stem/progenitor cells such as Abcg2, a determinant of the SP phenotype, and Musashi1, a neural stem/progenitor cell marker. These markers can differentiate cells expressing markers of HCs and supporting cells in vitro. Our observation that these SP cells are capable of differentiating into HC-like cells implies a possible use for such cells (i.e., the replacement of lost auditory HCs within damaged cochlea).
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Affiliation(s)
- Etienne Savary
- Institute of Neuroscience, INSERM U.583, Montpellier, France
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247
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Higashi T, Nakagawa T, Kita T, Kim TS, Sakamoto T, Ito J. Effects of bone morphogenetic protein 4 on differentiation of embryonic stem cells into myosin VIIa-positive cells. Acta Otolaryngol 2007:36-40. [PMID: 17453441 DOI: 10.1080/03655230601065373] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
CONCLUSION Our results indicate that myosin VIIa-positive cells are generated from embryonic stem cells (ESCs) co-cultured with PA6 cells; however, bone morphogenetic protein 4 (BMP4) may not be a key molecule for induction of myosin VIIa-positive cells from the ESCs. BACKGROUND ESCs have been considered as a basis for cell therapy in a range of organs, because of their potential for self-renewal and pluripotency. Co-culture with PA6 stromal cells can induce differentiation of ESCs into various types of ectodermal cells including sensory progenitors. BMP4 plays an essential role in the development of sensory hair cells in the inner ear. MATERIALS AND METHODS We examined effects of BMP4 on differentiation of ESCs into the hair cell immunophenotype. BMP4 was supplemented at different time points to ESCs co-cultured on PA6 stromal cells. The ESCs were then collected and examined for the expression of myosin VIIa, a hair cell marker, and betaIII-tubulin, a neural marker. The expression of myosin VIIa and betaIII-tubulin was identified. RESULTS Quantitative assessments revealed that exogenous BMP4 has significant effects on the expression of betaIII-tubulin, but not of myosin VIIa.
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Affiliation(s)
- Toru Higashi
- Department of Otolaryngology-Head and Neck Surgery, Kyoto University Graduate School of Medicine, Kyoto, Japan
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248
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Abstract
Sensorineural hearing loss is one of the most common disabilities in our society. Experimentally, many candidates for therapeutic molecules have been discovered. However, the lack of safe and effective methods for drug delivery to the cochlea has been a considerable obstacle to clinical application. Local application of therapeutic molecules into the cochlea has been used in clinic and in animal experiments. Advances in pharmacological technology provide various drug delivery systems via biomaterials, which can be utilized for local drug delivery to the cochlea. Recent studies in the field of otology have demonstrated the potential of synthetic and natural biomaterials for local drug delivery to the cochlea. Although problems still remain to be resolved for clinical application, introduction into clinical practice of these controlled-release systems may be reasonable because of their certain advantages over previous methods.
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Affiliation(s)
- Takayuki Nakagawa
- Department of Otolaryngology-Head and Neck Surgery, Kyoto University Graduate School of Medicine, Kyoto, Japan.
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249
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Abstract
The sensory epithelia of the inner ear contain mechanosensory hair cells and non-sensory supporting cells. Both classes of cell are heterogeneous, with phenotypes varying both between and within epithelia. The specification of individual cells as distinct types of hair cell or supporting cell is regulated through intra- and extracellular signalling pathways that have been poorly understood. However, new methodologies have resulted in significant steps forward in our understanding of the molecular pathways that direct cells towards these cell fates.
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Affiliation(s)
- Matthew W Kelley
- Section on Developmental Neuroscience, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, 35 Convent Dr., Bethesda, Maryland 20892, USA.
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250
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Tang LS, Montemayor C, Pereira FA. Sensorineural hearing loss: potential therapies and gene targets for drug development. IUBMB Life 2007; 58:525-30. [PMID: 17002980 DOI: 10.1080/15216540600913258] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Recent advances in the developmental biology, genetics and cell biology of the inner ear are guiding research to novel therapeutic modalities - a market currently estimated to be at least US Dollars 10 billion. This article highlights prospects to manipulate the mammalian hearing organ with gene and stem cell delivery to the inner ear to protect, repair or regenerate the hair cells, supporting cells and associated nerves.
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Affiliation(s)
- Louisa S Tang
- Huffington Center on Aging, Bobby R. Alford Department of Otolaryngology - Head and Neck Surgery, Baylor College of Medicine, Houston, Texas 77030, USA
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