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Kopecky B, Fritzsch B. Regeneration of Hair Cells: Making Sense of All the Noise. Pharmaceuticals (Basel) 2011; 4:848-879. [PMID: 21966254 PMCID: PMC3180915 DOI: 10.3390/ph4060848] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2011] [Revised: 06/04/2011] [Accepted: 06/08/2011] [Indexed: 12/17/2022] Open
Abstract
Hearing loss affects hundreds of millions of people worldwide by dampening or cutting off their auditory connection to the world. Current treatments for sensorineural hearing loss (SNHL) with cochlear implants are not perfect, leaving regenerative medicine as the logical avenue to a perfect cure. Multiple routes to regeneration of damaged hair cells have been proposed and are actively pursued. Each route not only requires a keen understanding of the molecular basis of ear development but also faces the practical limitations of stem cell regulation in the delicate inner ear where topology of cell distribution is essential. Improvements in our molecular understanding of the minimal essential genes necessary for hair cell formation and recent advances in stem cell manipulation, such as seen with inducible pluripotent stem cells (iPSCs) and epidermal neural crest stem cells (EPI-NCSCs), have opened new possibilities to advance research in translational stem cell therapies for individuals with hearing loss. Despite this, more detailed network maps of gene expression are needed, including an appreciation for the roles of microRNAs (miRs), key regulators of transcriptional gene networks. To harness the true potential of stem cells for hair cell regeneration, basic science and clinical medicine must work together to expedite the transition from bench to bedside by elucidating the full mechanisms of inner ear hair cell development, including a focus on the role of miRs, and adapting this knowledge safely and efficiently to stem cell technologies.
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Affiliation(s)
- Benjamin Kopecky
- Department of Biology, University of Iowa, Iowa City, IA, 52242, USA
- Medical Scientist Training Program, Carver College of Medicine, University of Iowa, Iowa City, IA, 52242, USA
| | - Bernd Fritzsch
- Department of Biology, University of Iowa, Iowa City, IA, 52242, USA
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Leake PA, Hradek GT, Hetherington AM, Stakhovskaya O. Brain-derived neurotrophic factor promotes cochlear spiral ganglion cell survival and function in deafened, developing cats. J Comp Neurol 2011; 519:1526-45. [PMID: 21452221 PMCID: PMC3079794 DOI: 10.1002/cne.22582] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Postnatal development and survival of spiral ganglion (SG) neurons depend on both neural activity and neurotrophic support. Our previous studies showed that electrical stimulation from a cochlear implant only partially prevents SG degeneration after early deafness. Thus, neurotrophic agents that might be combined with an implant to improve neural survival are of interest. Recent studies reporting that brain-derived neurotrophic factor (BDNF) promotes SG survival after deafness have been conducted in rodents and limited to relatively short durations. Our study examined longer duration BDNF treatment in deafened cats that may better model the slow progression of SG degeneration in human cochleae, and this is the first study of BDNF in the developing auditory system. Kittens were deafened neonatally, implanted at 4-5 weeks with intracochlear electrodes containing a drug-delivery cannula, and BDNF or artificial perilymph was infused for 10 weeks from a miniosmotic pump. In BDNF-treated cochleae, SG cells grew to normal size and were significantly larger than cells on the contralateral side. However, their morphology was not completely normal, and many neurons lacked or had thinned perikaryl myelin. Unbiased stereology was employed to estimate SG cell density, independent of cell size. BDNF was effective in promoting significantly improved survival of SG neurons in these developing animals. BDNF treatment also resulted in higher density and larger size of myelinated radial nerve fibers, sprouting of fibers into the scala tympani, and improvement of electrically evoked auditory brainstem response thresholds. BDNF may have potential therapeutic value in the developing auditory system, but many serious obstacles currently preclude clinical application.
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Affiliation(s)
- Patricia A Leake
- Departmant of Otolaryngology-Head and Neck Surgery, University of California San Francisco, San Francisco, California 94143-0526, USA.
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Provenzano MJ, Minner SA, Zander K, Clark JJ, Kane CJ, Green SH, Hansen MR. p75(NTR) expression and nuclear localization of p75(NTR) intracellular domain in spiral ganglion Schwann cells following deafness correlate with cell proliferation. Mol Cell Neurosci 2011; 47:306-15. [PMID: 21658451 DOI: 10.1016/j.mcn.2011.05.010] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2011] [Revised: 05/21/2011] [Accepted: 05/23/2011] [Indexed: 12/25/2022] Open
Abstract
Spiral ganglion Schwann cells (SGSCs) myelinate spiral ganglion neurons (SGNs) and represent a potential source of neurotrophic support for SGNs. Deafening due to loss of hair cells results in gradual degeneration and death of SGNs. Successful efforts to maintain or regenerate a functional auditory nerve may depend on a healthy population of SGSCs, yet the responses of SGSCs to neural injury remain largely unknown. Here we investigate the role of p75(NTR) in SGSC responses to gradual denervation. Following deafening, SGSCs in the osseous spiral lamina (OSL) and, subsequently, in Rosenthal's canal (RC) expressed elevated p75(NTR) compared to hearing controls. p75(NTR)-positive cells co-labeled with S100 and RIP antibodies (Schwann cell markers), but not with anti-neurofilament. The pattern of p75(NTR) expression mirrored the pattern of neural degeneration, beginning in the OSL of the cochlea base and later extending into the apex. SGSCs expressed sortilin, a p75(NTR) co-receptor for pro-neurotrophins. Both pro-nerve growth factor (pro-NGF) and pro-brain derived neurotrophic factor (proBDNF) induced apoptosis in cultured SGSCs. Deafened animals exhibited significantly higher levels of SGSC proliferation (as measured by BrdU uptake) compared to hearing animals while total Schwann cell density remained stable, suggesting a tight regulation of SGSC proliferation and cell death. SGSCs undergoing cell division lose p75(NTR) expression from the cell surface and demonstrate nuclear localization of the intracellular domain (ICD), raising the possibility that p75(NTR) cleavage and ICD nuclear localization regulate SGSC proliferation. These results suggest that p75(NTR) contributes to SGSC responses to deafening and neural degeneration.
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Affiliation(s)
- Matthew J Provenzano
- Department of Otolaryngology-Head and Neck Surgery, University of Iowa, Iowa City, IA 52242-1078, USA
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Clarke JC, Tuft BW, Clinger JD, Levine R, Figueroa LS, Guymon CA, Hansen MR. Micropatterned methacrylate polymers direct spiral ganglion neurite and Schwann cell growth. Hear Res 2011; 278:96-105. [PMID: 21616131 DOI: 10.1016/j.heares.2011.05.004] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/10/2010] [Revised: 04/27/2011] [Accepted: 05/03/2011] [Indexed: 01/17/2023]
Abstract
Significant advances in the functional outcomes achieved with cochlear implantation will likely require tissue-engineering approaches to improve the neural prosthesis interface. One strategy is to direct spiral ganglion neuron (SGN) axon growth in a highly organized fashion to approximate or contact stimulating electrodes. Here we assessed the ability of micropatterns induced by photopolymerization in methacrylate (MA) polymer systems to direct cultured neonatal rat SGN neurite growth and alignment of SG Schwann cells (SGSCs). SGN survival and neurite length were comparable among various polymer compositions. Remarkably, there was no significant difference in SGN survival or neurite length between laminin and non-laminin coated MA polymer substrates, suggesting high biocompatibility with SG tissue. Micropatterning with photopolymerization generated microchannels with a ridge periodicity of 50 μm and channel depths of 0.6-1.0 μm. SGN neurites grew within the grooves of the microchannels. These topographies strongly induced alignment of dissociated SGN neurites and SGSCs to parallel the pattern. By contrast, fibroblasts failed to align with the micropattern suggesting cell specific responses to topographical cues. SGN neurites extending from explants turned to parallel the pattern as they encountered the microchannels. The extent of turning was significantly correlated with angle at which the neurite initially encountered the pattern. These results indicate that SGN neurites respond to microtopographical features and that these features can be used to direct neurite growth in a highly organized fashion.
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Affiliation(s)
- Joseph C Clarke
- Department of Otolaryngology-Head and Neck Surgery, University of Iowa Hospitals and Clinics, 2PFP, 200 Hawkins Dr., Iowa City, IA 52242, USA
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Atkinson PJ, Cho CH, Hansen MR, Green SH. Activity of all JNK isoforms contributes to neurite growth in spiral ganglion neurons. Hear Res 2011; 278:77-85. [PMID: 21554942 DOI: 10.1016/j.heares.2011.04.011] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/03/2010] [Revised: 04/06/2011] [Accepted: 04/22/2011] [Indexed: 01/30/2023]
Abstract
Jun N-terminal kinase (JNK) is a multifunctional protein kinase crucial for neuronal apoptosis as well as neurite growth. We have previously shown that JNK activity is correlated with spiral ganglion neuron (SGN) apoptosis following hair cell loss in rats (Alam et al., 2007) implying that JNK inhibition may have therapeutic potential to protect SGNs in deaf individuals. Here we investigated the role of JNK in neurite outgrowth from cultured neonatal rat and mouse SGNs. We show that JNK is required for initial growth of neurites and for continued extension of already established neurites. The effect of JNK inhibition on neurite growth is rapid and is also rapidly reversible after washout of the inhibitor. Using phosphoJNK immunoreactivity as an indicator, we show that JNK is activated in growth cones within 30 min after transfer to medium lacking neurotrophic stimuli (5 K medium) but activation in the nucleus and soma requires hours. By transfecting epitope-tagged JNK1, JNK2, or JNK3 isoforms into SGNs, we found that all are present in the nucleus and cytoplasm and that there is no preferential redistribution to the nucleus after transfer to 5 K medium. Cotransfection of dominant-negative (dn) JNK1 and JNK2 into SGNs reduced neurite growth, although transfection of dnJNK1 or dnJNK2 alone had no significant effect. SGNs cultured from JNK3(-/-) mice showed reduced neurite growth that was further reduced by transfection of dnJNK1 and dnJNK2. This indicates that all three JNK isoforms promote SGN neurite growth although there may be functional redundancy between JNK1 and JNK2.
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Affiliation(s)
- Patrick J Atkinson
- Department of Biology, University of Iowa, 143 Biology Building, Iowa City, IA 52242, USA
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Jeon EJ, Xu N, Xu L, Hansen MR. Influence of central glia on spiral ganglion neuron neurite growth. Neuroscience 2011; 177:321-34. [PMID: 21241783 PMCID: PMC3057386 DOI: 10.1016/j.neuroscience.2011.01.014] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2010] [Revised: 01/05/2011] [Accepted: 01/06/2011] [Indexed: 10/18/2022]
Abstract
Spiral ganglion neurons (SGNs) extend processes that interact with Schwann cells (SCs) and with oligodendrocytes (OLs) and astrocytes (ACs). We investigated the ability of these glial cells to support SGN neurite growth. In the presence of cultured ACs, OLs and SCs, SGN neurites tended to follow SCs and OLs and cross-over ACs. Most neurites initially followed the type of glial cell on which the neuronal cell body was found. To determine the influence of homogeneous populations of glia on neurite growth, SG explants were plated on cultured SCs, ACs or OLs. The number of neurites/explant extending onto SCs (463.89±16.25) was significantly greater than the number extending onto ACs (111.38±38.73) or OLs (6.75±2.21), indicating that populations of central glia inhibit SGN neurite growth. Treatment with cell-permeant cpt-cAMP or forskolin (FSK) each significantly increased the number of neurites on OLs (133.54±25.59 and 292.25±83.57, respectively). cpt-cAMP and FSK each also increased the number of neurites on ACs (213.19±36.06 and 208.64±59.25, respectively), however the difference was not significant compared with control. The neurites on ACs and OLs failed to grow radially in a well-fasciculated pattern as on SCs. In explants plated on the borders of cultured OL-SC or AC-SC groups, more neurites extended onto SCs compared with OLs and ACs. Conditioned media (CM) from OL or AC cultures did not reduce neurite length, implying that the inhibition of neurite growth by central glia is not due to soluble factors. Taken together, these results demonstrate that homogeneous populations of central glia inhibit SGN neurite growth.
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Affiliation(s)
- Eun-Ju Jeon
- Department of Otolaryngology-Head and Neck Surgery, University of Iowa
- Department of Otolaryngology, Incheon St. Mary’s Hospital, The Catholic University of Korea, Seoul, Korea
| | - Ningyong Xu
- Department of Otolaryngology-Head and Neck Surgery, University of Iowa
| | - Lingjing Xu
- Department of Otolaryngology-Head and Neck Surgery, University of Iowa
| | - Marlan R. Hansen
- Department of Otolaryngology-Head and Neck Surgery, University of Iowa
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Stöver T, Lenarz T. Biomaterials in cochlear implants. GMS CURRENT TOPICS IN OTORHINOLARYNGOLOGY, HEAD AND NECK SURGERY 2011; 8:Doc10. [PMID: 22073103 PMCID: PMC3199815 DOI: 10.3205/cto000062] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The cochlear implant (CI) represents, for almost 25 years now, the gold standard in the treatment of children born deaf and for postlingually deafened adults. These devices thus constitute the greatest success story in the field of ‘neurobionic’ prostheses. Their (now routine) fitting in adults, and especially in young children and even babies, places exacting demands on these implants, particularly with regard to the biocompatibility of a CI’s surface components. Furthermore, certain parts of the implant face considerable mechanical challenges, such as the need for the electrode array to be flexible and resistant to breakage, and for the implant casing to be able to withstand external forces. As these implants are in the immediate vicinity of the middle-ear mucosa and of the junction to the perilymph of the cochlea, the risk exists – at least in principle – that bacteria may spread along the electrode array into the cochlea. The wide-ranging requirements made of the CI in terms of biocompatibility and the electrode mechanism mean that there is still further scope – despite the fact that CIs are already technically highly sophisticated – for ongoing improvements to the properties of these implants and their constituent materials, thus enhancing the effectiveness of these devices. This paper will therefore discuss fundamental material aspects of CIs as well as the potential for their future development.
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Affiliation(s)
- Timo Stöver
- Department of Otolaryngology, Goethe University Frankfurt, Frankfurt a.M., Germany
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58
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Haase GM, Prasad KN, Cole WC, Baggett-Strehlau JM, Wyatt SE. Antioxidant micronutrient impact on hearing disorders: concept, rationale, and evidence. Am J Otolaryngol 2011; 32:55-61. [PMID: 20015808 DOI: 10.1016/j.amjoto.2009.09.002] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2009] [Revised: 09/03/2009] [Accepted: 09/06/2009] [Indexed: 10/20/2022]
Abstract
PURPOSE Although auditory disorders are complex conditions, device-related modalities dominate current treatment. However, dysfunction from the central cortex to the inner ear apparatus is increasingly thought to be related to biochemical pathway abnormalities and to free radical-induced oxidative damage and chronic inflammation. Therefore, considering appropriate biologic therapy as an adjunct to standard care against these damaging factors may provide rational expansion of treatment options for otolaryngologists and audiologists. METHODS This review outlines the biologic concepts related to some auditory and vestibular conditions and details the current rationale for utilizing antioxidants for a spectrum of hearing disorders. The strategy is based on the authors' collective experience in antioxidant science and supported with published research, pilot animal data and preliminary clinical observations. RESULTS A comprehensive micronutrient approach was developed to exploit these pathways, and demonstrated safety and efficacy against oxidative damage and inflammation and clinically relevant neuroprotection. Cooperative research with Department of Defense institutions used prospective, randomized designs to show (1) reduction in oxidative damage measured in plasma and urine over six months, (2) protection against oxidative damage during 12 weeks of intense military training, (3) protection against inflammation after total body blast exposure (rodents), (4) strong neuroprotection against chemically-induced Parkinson's disease (rodents), (5) nerve VIII function improvement after concussive head injury in military personnel, and (6) tinnitus improvement in majority of patients after 90-day evaluation. CONCLUSION This systematic review of biologic strategies against hearing disorders combined with new animal and human observations may provide a rational basis for expanding current practice paradigms.
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Whitlon DS, Tieu D, Grover M. Purification and transfection of cochlear Schwann cells. Neuroscience 2010; 171:23-30. [PMID: 20837108 DOI: 10.1016/j.neuroscience.2010.08.069] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2010] [Revised: 08/24/2010] [Accepted: 08/31/2010] [Indexed: 10/19/2022]
Abstract
Schwann cells line nerve fibers in the peripheral nervous system (PNS) and synthesize myelin. In addition, they support neuronal survival, neurite growth and regeneration. In dissociated cultures of postnatal mouse spiral ganglia, regenerating neurites spontaneously associate with Schwann cells. However, the mechanisms and consequences of interactions between cochlear Schwann cells and spiral ganglion neurites have not been examined. Further, the similarities and differences between cochlear Schwann cells and other PNS Schwann cells have not been studied. Experiments to examine these questions will rely on the ability to purify and characterize cochlear Schwann cells. Here we present methods for purifying Schwann cells from postnatal mouse cochleas and for transfecting them with expression plasmids. Dissociated spiral ganglia were plated on poly-D-lysine/laminin in medium containing neurotrophins, leukemia inhibitory factor (LIF), N2 supplement and serum and maintained for 5 days. Cells were harvested with trypsin/EDTA and subjected to an immuno-magnetic purification procedure. After 24 h in vitro, cultures were >85% Schwann cells. Nucleofection of purified Schwann cells with pMax-green fluorescent protein (pMax-GFP) plasmid, or with pEGFP-C-vimentin plasmid returned >45% transfection efficiency. These methods will allow the in-depth characterization of cochlear Schwann cells and an evaluation of their biochemical, functional, and genetic mechanisms that may promote neurite growth from the spiral ganglion.
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Affiliation(s)
- D S Whitlon
- Department of Otolaryngology-Head and Neck Surgery, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA.
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60
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Renton JP, Xu N, Clark JJ, Hansen MR. Interaction of neurotrophin signaling with Bcl-2 localized to the mitochondria and endoplasmic reticulum on spiral ganglion neuron survival and neurite growth. J Neurosci Res 2010; 88:2239-51. [PMID: 20209634 DOI: 10.1002/jnr.22381] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Enhanced spiral ganglion neuron (SGN) survival and regeneration of peripheral axons following deafness will likely enhance the efficacy of cochlear implants. Overexpression of Bcl-2 prevents SGN death but inhibits neurite growth. Here we assessed the consequences of Bcl-2 targeted to either the mitochondria (GFP-Bcl-2-Maob) or the endoplasmic reticulum (ER, GFP-Bcl-2-Cb5) on cultured SGN survival and neurite growth. Transfection of wild-type GFP-Bcl-2, GFP-Bcl-2-Cb5, or GFP-Bcl-2-Maob increased SGN survival, with GFP-Bcl-2-Cb5 providing the most robust response. Paradoxically, expression of GFP-Bcl-2-Maob results in SGN death in the presence of neurotrophin-3 (NT-3) and brain-derived neurotrophic factor (BDNF), neurotrophins that independently promote SGN survival via Trk receptors. This loss of SGNs is associated with cleavage of caspase 3 and appears to be specific for neurotrophin signaling, insofar as coexpression of constitutively active mitogen-activated kinase kinase (MEKDeltaEE) or phosphatidyl inositol-3 kinase (P110), but not other prosurvival stimuli (e.g., membrane depolarization), also results in the loss of SGNs expressing GFP-Bcl-2-Maob. MEKDeltaEE and P110 promote SGN survival, whereas P110 promotes neurite growth to a greater extent than NT-3 or MEKDeltaEE. However, wild-type GFP-Bcl-2, GFP-Bcl-2-Cb5, and GFP-Bcl-2-Maob inhibit neurite growth even in the presence of neurotrophins, MEKDeltaEE, or P110. Historically, Bcl-2 has been thought to act primarily at the mitochondria to prevent neuronal apoptosis. Nevertheless, our data show that Bcl-2 targeted to the ER is more effective at rescuing SGNs in the absence of trophic factors. Additionally, Bcl-2 targeted to the mitochondria results in SGN death in the presence of neurotrophins. (c) 2010 Wiley-Liss, Inc.
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Affiliation(s)
- John P Renton
- Department of Otolaryngology-Head and Neck Surgery, University of Iowa, Iowa City, Iowa
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Jiao Y, Novozhilova E, Karlén A, Muhr J, Olivius P. Olfactory ensheathing cells promote neurite outgrowth from co-cultured brain stem slice. Exp Neurol 2010; 229:65-71. [PMID: 20974131 DOI: 10.1016/j.expneurol.2010.10.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2010] [Revised: 09/19/2010] [Accepted: 10/15/2010] [Indexed: 01/01/2023]
Abstract
Cell therapy aiming at the replacement of degenerated neurons is a very attractive approach. By using an established in vitro organotypic brain stem (BS) slice culture we screen for candidate donor cells, some of them being further functionally assessed in in vivo models of sensorineural hearing loss. Both in vitro and in vivo systems show that implanted cells face challenges of survival, targeted migration, differentiation and functional integration with the host tissue. Low success rates are possibly due to the lack of necessary neurotrophic factors, adhesion molecules and guiding cues. Olfactory ensheathing cells (OECs) have been shown to express a number of neurotrophic factors and to promote axonal growth through cell to cell interactions. In the present study we co-cultured OECs with organotypic BS slice in order to see if OECs can serve as a facilitator when screening candidate donor cells in an organotypic culture setup. Here we show that OECs when co-cultured with the auditory BS slice not only promote neurite outgrowth from the cochlear nucleus (CN) region of the BS slice but also support cells by having BS slice axons growing along their processes. These findings further suggest that OECs may enhance survival and targeted migration of candidate donor cells suitable for cell therapy in vitro and in vivo. This article is part of a Special Issue entitled: Understanding olfactory ensheathing glia and their prospect for nervous system repair.
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Affiliation(s)
- Yu Jiao
- Center for Hearing and Communication Research, Karolinska University Hospital, Stockholm, Sweden.
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Chronic electrical stimulation does not prevent spiral ganglion cell degeneration in deafened guinea pigs. Hear Res 2010; 269:169-79. [DOI: 10.1016/j.heares.2010.06.015] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/18/2010] [Revised: 06/16/2010] [Accepted: 06/17/2010] [Indexed: 02/08/2023]
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Staecker H, Garnham C. Neurotrophin therapy and cochlear implantation: translating animal models to human therapy. Exp Neurol 2010; 226:1-5. [PMID: 20654616 DOI: 10.1016/j.expneurol.2010.07.012] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2010] [Revised: 07/14/2010] [Accepted: 07/15/2010] [Indexed: 12/31/2022]
Abstract
Cochlear implantation is a highly successful intervention for the treatment of deafness that depends on electrical stimulation of the inner ear's surviving spiral ganglion neurons. It is thought that some of the variability in hearing outcomes that is seen in patients receiving implants may be a reflection of the number or health of surviving neurons. A variety of studies have demonstrated a relationship between hair cell loss and degeneration of the spiral ganglion. This has been attributed to the loss of neurotrophin production with destruction of the spiral ganglion's target, the hair cell. Delivery of neurotrophins either through a device or through gene therapy has been shown to improve spiral ganglion survival after hair cell loss and additionally improves the function of cochlear implants in animal models. Translation of these observations to human therapy will require a clear understanding of the relationship between human spiral ganglion health and cochlear implant outcomes as well as the development of novel pre- and post-implantation outcomes measures.
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Affiliation(s)
- Hinrich Staecker
- Department of Otolaryngology Head and Neck Surgery, University of Kansas, Kansas City, KS 66160, USA.
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Shibata SB, Raphael Y. Future approaches for inner ear protection and repair. JOURNAL OF COMMUNICATION DISORDERS 2010; 43:295-310. [PMID: 20430401 PMCID: PMC2905731 DOI: 10.1016/j.jcomdis.2010.04.001] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2009] [Revised: 01/28/2010] [Accepted: 02/01/2010] [Indexed: 05/29/2023]
Abstract
UNLABELLED Health care professionals tending to patients with inner ear disease face inquiries about therapy options, including treatments that are being developed for future use but not yet available. The devastating outcome of sensorineural hearing loss, combined with the permanent nature of the symptoms, make these inquiries demanding and frequent. The vast information accessible online and the publicity for breakthroughs in research add to patient requests for access to advanced and innovative therapies, even before these are available for clinical use. This can sometimes be taxing on the health care provider who is in contact with the patients. Here we aim to equip the provider with information about some of the progress made for protective and reparative approaches for treating inner ears. LEARNING OUTCOMES (1) Readers will be able to explain why hearing loss is irreversible and common, (2) readers will be able to explain the importance of protective measures and the progress made in discovery and design of novel biological protective molecules, (3) readers will be able to describe reparative approaches currently under investigation (such as tissue engineering), the main difficulties in the design of such therapies and the major hurdles that remain for making novel technologies clinically viable, and (4) readers will be able to explain to their patients some of the progress in developing new treatments without making the promise of imminent clinical use. With this information, readers will be able to guide patients to make better choices for their treatment and to guide students toward research in this exciting field.
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Affiliation(s)
- Seiji B. Shibata
- Kresge Hearing Research Institute, Department of Otolaryngology, The University of Michigan, Ann Arbor, MI, 48109-5648, USA
| | - Yehoash Raphael
- Kresge Hearing Research Institute, Department of Otolaryngology, The University of Michigan, Ann Arbor, MI, 48109-5648, USA
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Bao J, Ohlemiller KK. Age-related loss of spiral ganglion neurons. Hear Res 2010; 264:93-7. [PMID: 19854255 PMCID: PMC2868093 DOI: 10.1016/j.heares.2009.10.009] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/09/2009] [Revised: 10/14/2009] [Accepted: 10/16/2009] [Indexed: 01/12/2023]
Abstract
Spiral ganglion neurons (SGNs) are the relay station for auditory information between hair cells and central nervous system. Age-related decline of auditory function due to SGN loss can not be ameliorated by hearing aids or cochlear implants. Recent findings clearly indicate that survival of SGNs during aging depends on genetic and environmental interactions, which can be demonstrated at the systemic, tissue, cellular, and molecular levels. At the systemic level, both insulin/insulin-like growth factor-1 and lipophilic/steroid hormone pathways influence SGN survival during aging. At the level of organ of the Corti, it is difficult to determine whether age-related SGN loss is primary or secondary degeneration. However, a late stage of SGN degeneration may be independent of age-related loss of hair cells. At the cellular and molecular level, several pathways, particularly free radical and calcium signaling pathways, can influence age-related SGN loss, and further studies should determine how these pathways contribute to SGN loss, such as whether they directly or indirectly act on SGNs. With the advancement of recent genetic and pharmacologic tools, we should not only understand how SGNs die during aging, but also find ways to delay this loss.
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Affiliation(s)
- Jianxin Bao
- Fay and Carl Simmons Center for the Biology of Hearing and Deafness, Department of Otolaryngology, Washington University Medical School, 660 S. Euclid, St. Louis, MO 63110, USA.
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Accelerated neurite growth from spiral ganglion neurons exposed to the Rho kinase inhibitor H-1152. Neuroscience 2010; 169:855-62. [PMID: 20478368 DOI: 10.1016/j.neuroscience.2010.05.020] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2010] [Revised: 05/07/2010] [Accepted: 05/11/2010] [Indexed: 12/18/2022]
Abstract
Upon the death of their hair cell synaptic partners, bipolar cochlear spiral ganglion neurons either die or retract their peripheral nerve fibers. Efforts to induce the regrowth of the peripheral neurites have had to rely on limited knowledge of the mechanisms underlying spiral ganglion neurite regeneration and have been restricted by the impracticality of undertaking large numbers of manual analyses of neurite growth responses. Here we have used dissociated cultures of postnatal mouse spiral ganglia to assess the effects of the Rho kinase inhibitor H-1152 on neurite growth and to determine the utility of automated high content analysis for evaluating neurite length from spiral ganglion neurons in vitro. In cultures of postnatal mouse spiral ganglion, greater than 95% of the neurons develop bipolar, monopolar or neurite-free morphologies in ratios dependent on whether the initial medium composition contains leukemia inhibitory factor or bone morphogenetic protein 4. Cultures under both conditions were maintained for 24 h, then exposed for 18 h to H-1152. None of the cultures exposed to H-1152 showed decreased neuronal survival or alterations in the ratios of different neuronal morphologies. However, as measured manually, the population of neurite lengths was increased in the presence of H-1152 in both types of cultures. High content analysis using the Arrayscan VTi imager and Cellomics software confirmed the rank order differences in neurite lengths among culture conditions. These data suggest the presence of an inhibitory regulatory mechanism(s) in the signaling pathway of Rho kinase that slows the growth of spiral ganglion neurites. The automated analysis demonstrates the feasibility of using primary cultures of dissociated mouse spiral ganglion for large scale screens of chemicals, genes or other factors that regulate neurite growth.
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67
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Abstract
Sensory hair cells of the inner ear are responsible for translating auditory or vestibular stimuli into electrical energy that can be perceived by the nervous system. Although hair cells are exquisitely mechanically sensitive, they can be easily damaged by excessive stimulation by ototoxic drugs and by the effects of aging. In mammals, auditory hair cells are never replaced, such that cumulative damage to the ear causes progressive and permanent deafness. In contrast, non-mammalian vertebrates are capable of replacing lost hair cells, which has led to efforts to understand the molecular and cellular basis of regenerative responses in different vertebrate species. In this review, we describe recent progress in understanding the limits to hair cell regeneration in mammals and discuss the obstacles that currently exist for therapeutic approaches to hair cell replacement.
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Affiliation(s)
- Andrew K Groves
- Department of Neuroscience, Baylor College of Medicine, BCM 295, 1 Baylor Plaza, Houston, TX 77030, USA.
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68
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Shibata SB, Cortez SR, Beyer LA, Wiler JA, Di Polo A, Pfingst BE, Raphael Y. Transgenic BDNF induces nerve fiber regrowth into the auditory epithelium in deaf cochleae. Exp Neurol 2010; 223:464-72. [PMID: 20109446 DOI: 10.1016/j.expneurol.2010.01.011] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2009] [Revised: 01/20/2010] [Accepted: 01/21/2010] [Indexed: 12/26/2022]
Abstract
Sensory organs typically use receptor cells and afferent neurons to transduce environmental signals and transmit them to the CNS. When sensory cells are lost, nerves often regress from the sensory area. Therapeutic and regenerative approaches would benefit from the presence of nerve fibers in the tissue. In the hearing system, retraction of afferent innervation may accompany the degeneration of auditory hair cells that is associated with permanent hearing loss. The only therapy currently available for cases with severe or complete loss of hair cells is the cochlear implant auditory prosthesis. To enhance the therapeutic benefits of a cochlear implant, it is necessary to attract nerve fibers back into the cochlear epithelium. Here we show that forced expression of the neurotrophin gene BDNF in epithelial or mesothelial cells that remain in the deaf ear induces robust regrowth of nerve fibers towards the cells that secrete the neurotrophin, and results in re-innervation of the sensory area. The process of neurotrophin-induced neuronal regeneration is accompanied by significant preservation of the spiral ganglion cells. The ability to regrow nerve fibers into the basilar membrane area and protect the auditory nerve will enhance performance of cochlear implants and augment future cell replacement therapies such as stem cell implantation or induced transdifferentiation. This model also provides a general experimental stage for drawing nerve fibers into a tissue devoid of neurons, and studying the interaction between the nerve fibers and the tissue.
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Affiliation(s)
- Seiji B Shibata
- Kresge Hearing Research Institute, Department of Otolaryngology, The University of Michigan, 1150 W. Med. Cntr. Dr., Ann Arbor, MI 48109-5648, USA
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69
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Abstract
The technique of cochlear implantation was the first method which allowed replacement of a sense organ by a (partially) implantable electronic prosthesis. By this method the cells of the spiral ganglion of the cochlea are directly stimulated by the electrodes introduced into the cochlea, bypassing the functions of the outer and middle ear as well as the cochlea. Treatment with a cochlear implant (CI) has been established over the last 20-30 years as a reliable method for restoring hearing in adults and children with severe hearing disorders and is now a routine method in many centers. For optimal results in understanding speech and for children in the speech development phase, rehabilitation must be an integral part of the total treatment and follow soon after implantation. To achieve this early diagnosis of hearing difficulties or deafness is necessary, which is simplified by a consistent hearing screening of newborns, now a statutory procedure in Germany.
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Affiliation(s)
- J Maurer
- Direktor der Klinik für HNO-Krankheiten, Kopf-Hals- und Schädelbasischirurgie Sowie Plastische Operationen und des Zentrums für Hören und Kommunikation, Katholisches Klinikum Koblenz, Koblenz, Germany.
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70
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[Growth behavior of spiral ganglion explants on cochlear implant electrodes and their materials]. HNO 2009; 57:358-63. [PMID: 19247626 DOI: 10.1007/s00106-008-1843-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
BACKGROUND With the increasing use of cochlear implants (CIs), the insertion of alloplastic material into the inner ear is nowadays an established treatment for severe to profound hearing loss in children and adults. Beyond its widespread use, the biocompatibility of the CI electrode and its interaction with the neural structures of the cochlea is not yet established. METHODS To investigate the survival and growth behavior of spiral ganglion neurons on different CI materials, spiral ganglion explants from newborn rats were cultured on silicone and platinum, on a surface combination of silicone and platinum, and, finally, on a CI electrode. RESULTS The results of this study indicate that the growth of spiral ganglion neurons in vitro is strongly influenced by the different materials and their arrangement, with platinum exhibiting the highest degree of biocompatibility with respect to neurite extension. Level differences in the surface structure between silicone and platinum lead to inhibition of neurite outgrowth. Furthermore, the culturing of spiral ganglion explants on a CI electrode leads to neurite sprouting toward the electrodes made of platinum. CONCLUSION The biocompatibility of CI materials with spiral ganglion neurons was shown in this study, but it differs with different CI materials. Besides the material itself, the arrangement of the materials can affect the neurite extension.
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71
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Chikar JA, Batts SA, Pfingst BE, Raphael Y. Visualization of spiral ganglion neurites within the scala tympani with a cochlear implant in situ. J Neurosci Methods 2009; 179:201-7. [PMID: 19428528 DOI: 10.1016/j.jneumeth.2009.01.034] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2008] [Revised: 01/15/2009] [Accepted: 01/29/2009] [Indexed: 11/29/2022]
Abstract
Current cochlear histology methods do not allow in situ processing of cochlear implants. The metal components of the implant preclude standard embedding and mid-modiolar sectioning, and whole mounts do not have the spatial resolution needed to view the implant within the scala tympani. One focus of recent auditory research is the regeneration of structures within the cochlea, particularly the ganglion cells and their processes, and there are multiple potential benefits to cochlear implant users from this work. To facilitate experimental investigations of auditory nerve regeneration performed in conjunction with cochlear implantation, it is critical to visualize the cochlear tissue and the implant together to determine if the nerve has made contact with the implant. This paper presents a novel histological technique that enables simultaneous visualization of the in situ cochlear implant and neurofilament-labeled nerve processes within the scala tympani, and the spatial relationship between them.
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Affiliation(s)
- Jennifer A Chikar
- Kresge Hearing Research Institute, Department of Otolaryngology, University of Michigan, 1150 W. Medical Center Drive, Room 4605 Med Sci II, Ann Arbor, MI 48109-5616, USA
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72
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Spontaneous association of glial cells with regrowing neurites in mixed cultures of dissociated spiral ganglia. Neuroscience 2009; 161:227-35. [PMID: 19324078 DOI: 10.1016/j.neuroscience.2009.03.044] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2009] [Revised: 03/10/2009] [Accepted: 03/11/2009] [Indexed: 11/23/2022]
Abstract
Evidence from developmental and regeneration studies of the cochlea and other tissues gives reason to hypothesize a role for nonneural cells in the growth and regeneration of cochlear spiral ganglion nerve fibers. We examined the spontaneous associations of regrowing neurites and nonneural cells in mixed cultures of dissociated newborn mouse spiral ganglia. After 7 days in vitro, nonneural cells formed a confluent layer in the culture well. Regrowing neurites grew atop this layer, forming non-uniform patterns that were similar to those formed by endogenously expressed laminin-1, entactin and integrin beta4, but not fibronectin or tenascin. In cultures grown for 42 h and maintained in three different growth media, all regrowing neurites were preferentially associated with spindle-shaped nonneural cells. The spindle-shaped cells incorporated bromodeoxyuridine in culture and were immunoreactive for the proteins S100, laminin-1, laminin-2, SRY-related high-mobility-group box 10 transcription factor (Sox10), neurotrophin receptor (P75) and connexin29 but negative for fibronectin and glial fibrillary acidic protein. These cells existed in the culture within a much larger, general population of fibronectin positive cells. Immunolabeling of fixed cochleas from neonatal mice localized Sox10, P75 and connexin29, to peripheral nerve bundles. The observed expressions of protein markers and the bipolar, spindle shape of the neurite-associated cells indicate that they are derived in vitro from the original Schwann or satellite cells in the ganglion or spiral lamina. The spontaneous and preferential association of neurites in culture with mitotic Schwann cells highlights the potential contribution neurite-Schwann cell interactions may have in promoting the growth and regrowth of damaged spiral ganglion neurons in the cochlea.
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73
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Volkenstein S, Brors D, Hansen S, Minovi A, Laub M, Jennissen HP, Dazert S, Neumann A. Influence of bone morphogenetic protein-2 on spiral ganglion neurite growth in vitro. Eur Arch Otorhinolaryngol 2009; 266:1381-9. [DOI: 10.1007/s00405-009-0930-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2008] [Accepted: 02/17/2009] [Indexed: 11/28/2022]
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74
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Stimulation for the Return of Hearing. Neuromodulation 2009. [DOI: 10.1016/b978-0-12-374248-3.00059-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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75
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Tanamati LF, Bevilacqua MC, Costa OA. Longitudinal study of the ecap measured in children with cochlear implants. Braz J Otorhinolaryngol 2009; 75:90-6. [PMID: 19488566 PMCID: PMC9442250 DOI: 10.1016/s1808-8694(15)30837-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2007] [Accepted: 11/04/2007] [Indexed: 11/29/2022] Open
Abstract
In children with cochlear implant (CI), the recording of the electrically evoked compound action potential (ECAP) of the auditory nerve represents an option to assess changes in auditory nerve responses and the interaction between the electrode bundle and the neural tissue over time. Aim: To study ECAP in children during the first year of CI use. Materials and methods: The ECAP characteristics have been analyzed in 13 children implanted younger than three years of age. Series study. Results: During the first year of CI use there was a significant statistical raise in the N1 peak amplitude, in basal electrodes, between the second and third return visits. There were not any significant differences obtained for N1 peak, latency, slope, p-NRT or recovery time, in the return visits. Conclusion: During the first year of CI use, the electrical stimulation provided by the intracochlear electrodes did not cause significant changes to ECAP characteristics, except for an increase in N1 peak amplitude.
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76
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Wei D, Levic S, Nie L, Gao WQ, Petit C, Jones EG, Yamoah EN. Cells of adult brain germinal zone have properties akin to hair cells and can be used to replace inner ear sensory cells after damage. Proc Natl Acad Sci U S A 2008; 105:21000-5. [PMID: 19064919 PMCID: PMC2634930 DOI: 10.1073/pnas.0808044105] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2008] [Indexed: 01/27/2023] Open
Abstract
Auditory hair cell defect is a major cause of hearing impairment, often leading to spiral ganglia neuron (SGN) degeneration. The cell loss that follows is irreversible in mammals, because inner ear hair cells (HCs) have a limited capacity to regenerate. Here, we report that in the adult brain of both rodents and humans, the ependymal layer of the lateral ventricle contains cells with proliferative potential, which share morphological and functional characteristics with HCs. In addition, putative neural stem cells (NSCs) from the subventricular zone of the lateral ventricle can differentiate into functional SGNs. Also important, the NSCs can incorporate into the sensory epithelia, demonstrating their therapeutic potential. We assert that NSCs and edendymal cells can undergo an epigenetic functional switch to assume functional characteristics of HCs and SGNs. This study suggests that the functional plasticity of renewable cells and conditions that promote functional reprogramming can be used for cell therapy in the auditory setting.
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Affiliation(s)
- Dongguang Wei
- Department of Anesthesiology and Pain Medicine, Center for Neuroscience, Program in Communication and Sensory Science, University of California, 1544 Newton Court, Davis, CA 95618
| | - Snezana Levic
- Department of Anesthesiology and Pain Medicine, Center for Neuroscience, Program in Communication and Sensory Science, University of California, 1544 Newton Court, Davis, CA 95618
| | - Liping Nie
- Department of Anesthesiology and Pain Medicine, Center for Neuroscience, Program in Communication and Sensory Science, University of California, 1544 Newton Court, Davis, CA 95618
| | - Wei-qiang Gao
- Department of Molecular Biology, Genentech, Inc., South San Francisco, CA 94080; and
| | - Christine Petit
- Unité de Génétique et Physiologie de l'Audition, Unité Mixte de Recherche S587, Institut National de la Santé et de la Recherche Médicale-Université Paris VI, Collège de France, Institut Pasteur, 25 Rue du Dr Roux, 75724 Paris, Cedex 15, France
| | - Edward G. Jones
- Department of Anesthesiology and Pain Medicine, Center for Neuroscience, Program in Communication and Sensory Science, University of California, 1544 Newton Court, Davis, CA 95618
| | - Ebenezer N. Yamoah
- Department of Anesthesiology and Pain Medicine, Center for Neuroscience, Program in Communication and Sensory Science, University of California, 1544 Newton Court, Davis, CA 95618
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77
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Ruel J, Emery S, Nouvian R, Bersot T, Amilhon B, Van Rybroek JM, Rebillard G, Lenoir M, Eybalin M, Delprat B, Sivakumaran TA, Giros B, El Mestikawy S, Moser T, Smith RJ, Lesperance MM, Puel JL. Impairment of SLC17A8 encoding vesicular glutamate transporter-3, VGLUT3, underlies nonsyndromic deafness DFNA25 and inner hair cell dysfunction in null mice. Am J Hum Genet 2008; 83:278-92. [PMID: 18674745 PMCID: PMC2495073 DOI: 10.1016/j.ajhg.2008.07.008] [Citation(s) in RCA: 177] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2008] [Revised: 06/20/2008] [Accepted: 07/11/2008] [Indexed: 11/27/2022] Open
Abstract
Autosomal-dominant sensorineural hearing loss is genetically heterogeneous, with a phenotype closely resembling presbycusis, the most common sensory defect associated with aging in humans. We have identified SLC17A8, which encodes the vesicular glutamate transporter-3 (VGLUT3), as the gene responsible for DFNA25, an autosomal-dominant form of progressive, high-frequency nonsyndromic deafness. In two unrelated families, a heterozygous missense mutation, c.632C-->T (p.A211V), was found to segregate with DFNA25 deafness and was not present in 267 controls. Linkage-disequilibrium analysis suggested that the families have a distant common ancestor. The A211 residue is conserved in VGLUT3 across species and in all human VGLUT subtypes (VGLUT1-3), suggesting an important functional role. In the cochlea, VGLUT3 accumulates glutamate in the synaptic vesicles of the sensory inner hair cells (IHCs) before releasing it onto receptors of auditory-nerve terminals. Null mice with a targeted deletion of Slc17a8 exon 2 lacked auditory-nerve responses to acoustic stimuli, although auditory brainstem responses could be elicited by electrical stimuli, and robust otoacoustic emissions were recorded. Ca(2+)-triggered synaptic-vesicle turnover was normal in IHCs of Slc17a8 null mice when probed by membrane capacitance measurements at 2 weeks of age. Later, the number of afferent synapses, spiral ganglion neurons, and lateral efferent endings below sensory IHCs declined. Ribbon synapses remaining by 3 months of age had a normal ultrastructural appearance. We conclude that deafness in Slc17a8-deficient mice is due to a specific defect of vesicular glutamate uptake and release and that VGLUT3 is essential for auditory coding at the IHC synapse.
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Affiliation(s)
- Jérôme Ruel
- Inserm U 583, Institut des Neurosciences, Hôpital Saint Eloi, 34091 Montpellier, France
- Université Montpellier 1, 34091 Montpellier, France
| | - Sarah Emery
- Division of Pediatric Otolaryngology, Department of Otolaryngology-Head and Neck Surgery, University of Michigan Health System, Ann Arbor, MI 48109-5241, USA
| | - Régis Nouvian
- InnerEarLab, Department of Otolaryngology and Center for Molecular Physiology of the Brain, University of Goettingen Medical School, Goettingen 37075, Germany
| | - Tiphaine Bersot
- Inserm U 583, Institut des Neurosciences, Hôpital Saint Eloi, 34091 Montpellier, France
- Université Montpellier 1, 34091 Montpellier, France
| | | | - Jana M. Van Rybroek
- Department of Otolaryngology and Head and Neck Surgery, University of Iowa, Iowa City, IA 52242, USA
| | - Guy Rebillard
- Inserm U 583, Institut des Neurosciences, Hôpital Saint Eloi, 34091 Montpellier, France
- Université Montpellier 1, 34091 Montpellier, France
| | - Marc Lenoir
- Inserm U 583, Institut des Neurosciences, Hôpital Saint Eloi, 34091 Montpellier, France
- Université Montpellier 1, 34091 Montpellier, France
| | - Michel Eybalin
- Inserm U 583, Institut des Neurosciences, Hôpital Saint Eloi, 34091 Montpellier, France
- Université Montpellier 1, 34091 Montpellier, France
| | - Benjamin Delprat
- Inserm U 583, Institut des Neurosciences, Hôpital Saint Eloi, 34091 Montpellier, France
- Université Montpellier 1, 34091 Montpellier, France
| | - Theru A. Sivakumaran
- Division of Pediatric Otolaryngology, Department of Otolaryngology-Head and Neck Surgery, University of Michigan Health System, Ann Arbor, MI 48109-5241, USA
| | - Bruno Giros
- Inserm U 513, 9 Quai Saint Bernard, 75252 Paris, France
| | | | - Tobias Moser
- InnerEarLab, Department of Otolaryngology and Center for Molecular Physiology of the Brain, University of Goettingen Medical School, Goettingen 37075, Germany
- Bernstein Center for Computational Neuroscience, University of Goettingen, Goettingen 37075, Germany
| | - Richard J.H. Smith
- Department of Otolaryngology and Head and Neck Surgery, University of Iowa, Iowa City, IA 52242, USA
| | - Marci M. Lesperance
- Division of Pediatric Otolaryngology, Department of Otolaryngology-Head and Neck Surgery, University of Michigan Health System, Ann Arbor, MI 48109-5241, USA
| | - Jean-Luc Puel
- Inserm U 583, Institut des Neurosciences, Hôpital Saint Eloi, 34091 Montpellier, France
- Université Montpellier 1, 34091 Montpellier, France
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78
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Shepherd RK, Coco A, Epp SB. Neurotrophins and electrical stimulation for protection and repair of spiral ganglion neurons following sensorineural hearing loss. Hear Res 2008; 242:100-9. [PMID: 18243608 PMCID: PMC2630855 DOI: 10.1016/j.heares.2007.12.005] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/12/2007] [Revised: 12/05/2007] [Accepted: 12/12/2007] [Indexed: 01/14/2023]
Abstract
Exogenous neurotrophins (NTs) have been shown to rescue spiral ganglion neurons (SGNs) from degeneration following a sensorineural hearing loss (SNHL). Furthermore, chronic electrical stimulation (ES) has been shown to retard SGN degeneration in some studies but not others. Since there is evidence of even greater SGN rescue when NT administration is combined with ES, we examined whether chronic ES can maintain SGN survival long after cessation of NT delivery. Young adult guinea pigs were profoundly deafened using ototoxic drugs; five days later they were unilaterally implanted with an electrode array and drug delivery system. Brain derived neurotrophic factor (BDNF) was continuously delivered to the scala tympani over a four week period while the animal simultaneously received ES via bipolar electrodes in the basal turn (i.e., turn 1) scala tympani. One cohort (n=5) received ES for six weeks (i.e., including a two week period after the cessation of BDNF delivery; ES(6)); a second cohort (n=5) received ES for 10 weeks (i.e., a six week period following cessation of BDNF delivery; ES(10)). The cochleae were harvested for histology and SGN density determined for each cochlear turn for comparison with normal hearing controls (n=4). The withdrawal of BDNF resulted in a rapid loss of SGNs in turns 2-4 of the deafened/BDNF-treated cochleae; this was significant as early as two weeks following removal of the NT when compared with normal controls (p<0.05). Importantly, there was not a significant reduction in SGNs in turn 1 (i.e., adjacent to the electrode array) two and six weeks after NT removal, as compared with normal controls. This result suggests that chronic ES can prevent the rapid loss of SGNs that occurs after the withdrawal of exogenous NTs. Implications for the clinical delivery of NTs are discussed.
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Affiliation(s)
- Robert K Shepherd
- The Bionic Ear Institute, 384-388 Albert Street, East Melbourne, Victoria 3002, Australia.
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79
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Abstract
This review is based on Pubmed, Medline and Internet literature searches, supplemented by knowledge from textbooks, conference presentations, and personal communications with experts in the field of hearing restoration and patients. We have not specifically selected a time limit for our literature searches; however, the majority are articles from the past 5 years.
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Affiliation(s)
- Kunal Kulkarni
- The Department of Physiology, Anatomy & Genetics, University of Oxford Sherrington Building, Parks Road, Oxford, UK.
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80
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Regenerating cochlear hair cells: quo vadis stem cell. Cell Tissue Res 2008; 333:373-9. [PMID: 18575894 DOI: 10.1007/s00441-008-0639-z] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2008] [Revised: 05/07/2008] [Accepted: 05/08/2008] [Indexed: 12/30/2022]
Abstract
Many elderly people worldwide lose the neurosensory part of their ear and turn deaf. Cochlear implants to restore some hearing after neurosensory hearing loss are, at present, the only therapy for these people. In contrast to this therapy, replacement of hair cells via stem cell therapies holds the promise for a cure. We review here current insights into embryonic, adult, and inducible stem cells that might provide cells for seeding the cochlea with the hope of new hair cell formation. We propose a two-step approach using a first set of transcription factors to enhance the generation of inducible pluripotent stem (iPS) cells and a second set of factors to initiate the differentiation of hair cells. Recent evidence regarding ear development and stem cell research strongly suggest that microRNAs will be an important new regulatory factor in both iPS cell formation and differentiation to reprogram cells into hair cells. In addition, we highlight currently insurmountable obstacles to the successful transformation of stem cells into hair cell precursors and their injection into the cochlear canal to replace lost hair cells.
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81
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Wilson BS, Dorman MF. Cochlear implants: a remarkable past and a brilliant future. Hear Res 2008; 242:3-21. [PMID: 18616994 DOI: 10.1016/j.heares.2008.06.005] [Citation(s) in RCA: 398] [Impact Index Per Article: 24.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/28/2007] [Revised: 06/08/2008] [Accepted: 06/11/2008] [Indexed: 11/18/2022]
Abstract
The aims of this paper are to (i) provide a brief history of cochlear implants; (ii) present a status report on the current state of implant engineering and the levels of speech understanding enabled by that engineering; (iii) describe limitations of current signal processing strategies; and (iv) suggest new directions for research. With current technology the "average" implant patient, when listening to predictable conversations in quiet, is able to communicate with relative ease. However, in an environment typical of a workplace the average patient has a great deal of difficulty. Patients who are "above average" in terms of speech understanding, can achieve 100% correct scores on the most difficult tests of speech understanding in quiet but also have significant difficulty when signals are presented in noise. The major factors in these outcomes appear to be (i) a loss of low-frequency, fine structure information possibly due to the envelope extraction algorithms common to cochlear implant signal processing; (ii) a limitation in the number of effective channels of stimulation due to overlap in electric fields from electrodes; and (iii) central processing deficits, especially for patients with poor speech understanding. Two recent developments, bilateral implants and combined electric and acoustic stimulation, have promise to remediate some of the difficulties experienced by patients in noise and to reinstate low-frequency fine structure information. If other possibilities are realized, e.g., electrodes that emit drugs to inhibit cell death following trauma and to induce the growth of neurites toward electrodes, then the future is very bright indeed.
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Affiliation(s)
- Blake S Wilson
- Division of Otolaryngology, Head and Neck Surgery, Department of Surgery, Duke University Medical Center, Durham, NC 27710, USA.
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82
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Glueckert R, Bitsche M, Miller JM, Zhu Y, Prieskorn DM, Altschuler RA, Schrott-Fischer A. Deafferentiation-associated changes in afferent and efferent processes in the guinea pig cochlea and afferent regeneration with chronic intrascalar brain-derived neurotrophic factor and acidic fibroblast growth factor. J Comp Neurol 2008; 507:1602-21. [DOI: 10.1002/cne.21619] [Citation(s) in RCA: 117] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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83
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Roehm PC, Xu N, Woodson EA, Green SH, Hansen MR. Membrane depolarization inhibits spiral ganglion neurite growth via activation of multiple types of voltage sensitive calcium channels and calpain. Mol Cell Neurosci 2007; 37:376-87. [PMID: 18055215 DOI: 10.1016/j.mcn.2007.10.014] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2007] [Revised: 10/17/2007] [Accepted: 10/25/2007] [Indexed: 12/23/2022] Open
Abstract
The effect of membrane electrical activity on spiral ganglion neuron (SGN) neurite growth remains unknown despite its relevance to cochlear implant technology. We demonstrate that membrane depolarization delays the initial formation and inhibits the subsequent extension of cultured SGN neurites. This inhibition depends directly on the level of depolarization with higher levels of depolarization causing retraction of existing neurites. Cultured SGNs express subunits for L-type, N-type, and P/Q type voltage-gated calcium channels (VGCCs) and removal of extracellular Ca(2+) or treatment with a combination of L-type, N-type, and P/Q-type VGCC antagonists rescues SGN neurite growth under depolarizing conditions. By measuring the fluorescence intensity of SGNs loaded with the fluorogenic calpain substrate t-butoxy carbonyl-Leu-Met-chloromethylaminocoumarin (20 microM), we demonstrate that depolarization activates calpains. Calpeptin (15 microM), a calpain inhibitor, prevents calpain activation by depolarization and rescues neurite growth in depolarized SGNs suggesting that calpain activation contributes to the inhibition of neurite growth by depolarization.
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Affiliation(s)
- Pamela C Roehm
- Department of Otolaryngology-Head and Neck Surgery, University of Iowa, Iowa City, IA 52242, USA
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84
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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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85
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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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86
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Fritzsch B, Beisel KW, Hansen LA. The molecular basis of neurosensory cell formation in ear development: a blueprint for hair cell and sensory neuron regeneration? Bioessays 2007; 28:1181-93. [PMID: 17120192 PMCID: PMC3901523 DOI: 10.1002/bies.20502] [Citation(s) in RCA: 97] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The inner ear of mammals uses neurosensory cells derived from the embryonic ear for mechanoelectric transduction of vestibular and auditory stimuli (the hair cells) and conducts this information to the brain via sensory neurons. As with most other neurons of mammals, lost hair cells and sensory neurons are not spontaneously replaced and result instead in age-dependent progressive hearing loss. We review the molecular basis of neurosensory development in the mouse ear to provide a blueprint for possible enhancement of therapeutically useful transformation of stem cells into lost neurosensory cells. We identify several readily available adult sources of stem cells that express, like the ectoderm-derived ear, genes known to be essential for ear development. Use of these stem cells combined with molecular insights into neurosensory cell specification and proliferation regulation of the ear, might allow for neurosensory regeneration of mammalian ears in the near future.
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Affiliation(s)
- Bernd Fritzsch
- Creighton University, Department of Biomedical Sciences, Omaha, NE 68178, USA.
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87
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Whitlon DS, Grover M, Tristano J, Williams T, Coulson MT. Culture conditions determine the prevalence of bipolar and monopolar neurons in cultures of dissociated spiral ganglion. Neuroscience 2007; 146:833-40. [PMID: 17331652 PMCID: PMC2532701 DOI: 10.1016/j.neuroscience.2007.01.036] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2006] [Revised: 01/19/2007] [Accepted: 01/22/2007] [Indexed: 01/05/2023]
Abstract
To gain insight into the mechanisms that control the generation or maintenance of the characteristic bipolar morphology of cochlear spiral ganglion neurons, we have taken advantage of our recently developed procedure for culture of dissociated newborn mouse spiral ganglion. In these cultures, inclusion of the cytokine leukemia inhibitory factor (LIF) in the medium increases neuronal survival and the number of bipolar neurons. Here we tested effects of two other LIF-type cytokines (ciliary neurotrophic factor, CNTF; and human recombinant oncostatin M, hOSM) and of bone morphogenetic protein 4 (BMP4) on survival, morphology and neurite lengths of neurons in cultures of dissociated spiral ganglion. Like LIF, CNTF and hOSM increased neuronal survival and the number of surviving bipolar neurons. BMP4 also increased neuronal survival, but unlike LIF, CNTF and hOSM, increased the number of monopolar neurons and neurons with no neurites. In addition, population histograms demonstrate that the population lengths of the longer and shorter neurites of bipolar neurons were shorter in BMP4 containing cultures than in control or LIF cultures. When LIF and BMP4 were simultaneously added to the cultures, the BMP4 effects predominated. These experiments demonstrate that exposure to different environmental conditions can result in different morphologies in the surviving population of spiral ganglion neurons in culture.
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Affiliation(s)
- D S Whitlon
- Department of Otolaryngology Head and Neck Surgery, Searle, Room 12-561, Feinberg School of Medicine, Northwestern University, 303 East Chicago Avenue, Chicago, IL 60611, USA.
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88
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Yoshida T, Hakuba N, Morizane I, Fujita K, Cao F, Zhu P, Uchida N, Kameda K, Sakanaka M, Gyo K, Hata R. Hematopoietic stem cells prevent hair cell death after transient cochlear ischemia through paracrine effects. Neuroscience 2007; 145:923-30. [PMID: 17320298 DOI: 10.1016/j.neuroscience.2006.12.067] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2006] [Revised: 12/21/2006] [Accepted: 12/23/2006] [Indexed: 01/01/2023]
Abstract
Transplantation of hematopoietic stem cells (HSCs) is regarded to be a potential approach for promoting repair of damaged organs. Here, we investigated the influence of hematopoietic stem cells on progressive hair cell degeneration after transient cochlear ischemia in gerbils. Transient cochlear ischemia was produced by extracranial occlusion of the bilateral vertebral arteries just before their entry into the transverse foramen of the cervical vertebra. Intrascalar injection of HSCs prevented ischemia-induced hair cell degeneration and ameliorated hearing impairment. We also showed that the protein level of glial cell line-derived neurotrophic factor (GDNF) in the organ of Corti was upregulated after cochlear ischemia and that treatment with HSCs augmented this ischemia-induced upregulation of GDNF. A tracking study revealed that HSCs injected into the cochlea were retained in the perilymphatic space of the cochlea, although they neither transdifferentiated into cochlear cell types nor fused with the injured hair cells after ischemia, suggesting that HSCs had therapeutic potential possibly through paracrine effects. Thus, we propose HSCs as a potential new therapeutic strategy for hearing loss.
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Affiliation(s)
- T Yoshida
- Department of Otolaryngology, Ehime University Graduate School of Medicine, Shitsukawa, Toon, Ehime 791-0295, Japan
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89
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Nemzou N RM, Bulankina AV, Khimich D, Giese A, Moser T. Synaptic organization in cochlear inner hair cells deficient for the CaV1.3 (alpha1D) subunit of L-type Ca2+ channels. Neuroscience 2006; 141:1849-60. [PMID: 16828974 DOI: 10.1016/j.neuroscience.2006.05.057] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2006] [Revised: 04/25/2006] [Accepted: 05/23/2006] [Indexed: 11/25/2022]
Abstract
Cochlear inner hair cells (IHCs) release neurotransmitter onto afferent auditory nerve fibers in response to sound stimulation. Normal development and function of inner hair cells require the expression of alpha subunit 1.3 forming L-type voltage-gated Ca(2+) channel (Ca(V)1.3). Here, we used immunohistochemistry and reverse transcription-polymerase chain reaction to study the synaptic organization and expression of large conductance Ca(2+)-activated potassium channels in IHCs of mice lacking the Ca(V)1.3 Ca(2+) channel (Ca(V)1.3(-/-)). Despite the near complete block of evoked afferent synaptic transmission, hair cell ribbon synapses were formed and remained preserved for at least 4 weeks after birth. Moreover, these "silent" afferent synapses held major components of the synaptic machinery such as Bassoon, Piccolo, and CSP. Hence, the block of exocytosis might be solely attributed to the lack of Ca(2+) influx through Ca(V)1.3 channels. Later on, Ca(V)1.3 deficient IHCs subsequently lost their afferent synapses. This was probably due to a secondary degeneration of the postsynaptic spiral ganglion neurons. In line with a prolonged efferent synaptic transmission onto Ca(V)1.3 deficient IHCs, which normally ceases around onset of hearing, we found juxtaposed immunoreactive spots of efferent presynaptic synaptophysin and postsynaptic (IHCs) small conductance Ca(2+)-activated potassium channels (SK channels) up to six weeks after birth. Finally, we show a substantial reduction of mRNA for the alpha subunit of the large conductance Ca(2+)-activated potassium channel (BK) in the apical cochlea, suggesting a reduced transcription of its gene in Ca(V)1.3 deficient IHCs. Ca(V)1.3 deficient IHCs lacked the apical spot-like immunoreactivity of clustered BK channels, which normally contribute to the temporal precision of hair cell afferent synaptic transmission. In summary, these data indicate that the Ca(V)1.3 channels are crucially involved in regulation of the expression of BK and SK channels. Ca(V)1.3 channels seem not to be essential for ribbon synapse formation, but are required for the maintenance of ribbon synapses and spiral ganglion neurons.
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MESH Headings
- Age Factors
- Animals
- Animals, Newborn
- Blotting, Northern/methods
- Calcium Channels, L-Type/deficiency
- Calcium Channels, L-Type/genetics
- Cochlea/cytology
- Gene Expression Regulation, Developmental/genetics
- Hair Cells, Auditory, Inner/cytology
- Hair Cells, Auditory, Inner/physiology
- Immunohistochemistry/methods
- In Vitro Techniques
- Large-Conductance Calcium-Activated Potassium Channel alpha Subunits/genetics
- Large-Conductance Calcium-Activated Potassium Channel alpha Subunits/metabolism
- Membrane Glycoproteins/genetics
- Membrane Glycoproteins/metabolism
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Protein Subunits/genetics
- Protein Subunits/metabolism
- RNA, Messenger/metabolism
- Receptors, Glutamate/metabolism
- Reverse Transcriptase Polymerase Chain Reaction/methods
- Synapses/physiology
- Synaptophysin/metabolism
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Affiliation(s)
- R M Nemzou N
- Department of Otolaryngology and Center for Molecular Physiology of the Brain, University of Göttingen Medical School, D-37099 Göttingen, Germany
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90
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Whitlon DS, Ketels KV, Coulson MT, Williams T, Grover M, Edpao W, Richter CP. Survival and morphology of auditory neurons in dissociated cultures of newborn mouse spiral ganglion. Neuroscience 2006; 138:653-62. [PMID: 16413120 DOI: 10.1016/j.neuroscience.2005.11.030] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2005] [Revised: 11/08/2005] [Accepted: 11/20/2005] [Indexed: 10/25/2022]
Abstract
We have systematically characterized neuronal survival and growth in cultures derived from newborn/postnatal day 1 mouse cochlea. Dissociated cultures of the cochlear spiral ganglion provide an experimental environment in which to examine molecular mechanisms of survival, development and physiology of auditory neurons. To relate survival to the total number of neurons present in the source tissue, three cochleas from different newborn CD-1 mice were embedded in Araldite resin and serially sectioned at 5 mum thickness. All neurons were counted. To avoid overcounting, each section served as a lookup section for the next, giving 8240+/-423 (S.D.) neurons per ganglion. Cultures maintained in the presence of adjacent non-neural tissue, brain-derived neurotrophic factor, neurotrophin 3, leukemia inhibitory factor (LIF) and 10% fetal bovine serum returned the best overall survival (30%) at 42 h post-plating. Best overall survival required the continuous presence of a serum component(s) larger than 100,000 MW. Plating efficiency (number of neurons that attach to the well after 4 h) was similar in the presence or absence of LIF. Inclusion of LIF maintained 100% survival of plated neurons over 42 h of culture; without LIF, a large fraction of the neurons did not survive. LIF appeared to maintain survival by preferentially preserving a population of bipolar neurons, while having little effect on the number of monopolar neurons. This work provides quantitative measures of survival and morphology of auditory neurons in vitro. The results support the idea that survival of spiral ganglion neurons in vivo may depend on interactions with adjacent, non-neural tissue and raise the possibility that maintenance of bipolar morphology after hair cell damage may require biochemical mechanisms in addition to those induced by neurotrophins.
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Affiliation(s)
- D S Whitlon
- Department of Otolaryngology-Head and Neck Surgery, Feinberg School of Medicine, Northwestern University, 303 East Chicago Avenue, Chicago, IL 60611, USA.
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