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Closing the Gap between the Auditory Nerve and Cochlear Implant Electrodes: Which Neurotrophin Cocktail Performs Best for Axonal Outgrowth and Is Electrical Stimulation Beneficial? Int J Mol Sci 2023; 24:ijms24032013. [PMID: 36768339 PMCID: PMC9916558 DOI: 10.3390/ijms24032013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Revised: 01/12/2023] [Accepted: 01/14/2023] [Indexed: 01/22/2023] Open
Abstract
Neurotrophins promote neurite outgrowth of auditory neurons and may help closing the gap to cochlear implant (CI) electrodes to enhance electrical hearing. The best concentrations and mix of neurotrophins for this nerve regrowth are unknown. Whether electrical stimulation (ES) during outgrowth is beneficial or may direct axons is another open question. Auditory neuron explant cultures of distinct cochlear turns of 6-7 days old mice were cultured for four days. We tested different concentrations and combinations of BDNF and NT-3 and quantified the numbers and lengths of neurites with an advanced automated analysis. A custom-made 24-well electrical stimulator based on two bulk CIs served to test different ES strategies. Quantification of receptors trkB, trkC, p75NTR, and histological analysis helped to analyze effects. We found 25 ng/mL BDNF to perform best, especially in basal neurons, a negative influence of NT-3 in combined BDNF/NT-3 scenarios, and tonotopic changes in trk and p75NTR receptor stainings. ES largely impeded neurite outgrowth and glia ensheathment in an amplitude-dependent way. Apical neurons showed slight benefits in neurite numbers and length with ES at 10 and 500 µA. We recommend BDNF as a potent drug to enhance the man-machine interface, but CIs should be better activated after nerve regrowth.
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Vogl C, Neef J, Wichmann C. Methods for multiscale structural and functional analysis of the mammalian cochlea. Mol Cell Neurosci 2022; 120:103720. [DOI: 10.1016/j.mcn.2022.103720] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2021] [Revised: 02/13/2022] [Accepted: 03/08/2022] [Indexed: 01/11/2023] Open
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3
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Evolution of inner ear neuroanatomy of bats and implications for echolocation. Nature 2022; 602:449-454. [PMID: 35082447 DOI: 10.1038/s41586-021-04335-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2021] [Accepted: 12/10/2021] [Indexed: 12/25/2022]
Abstract
Phylogenomics of bats suggests that their echolocation either evolved separately in the bat suborders Yinpterochiroptera and Yangochiroptera, or had a single origin in bat ancestors and was later lost in some yinpterochiropterans1-6. Hearing for echolocation behaviour depends on the inner ear, of which the spiral ganglion is an essential structure. Here we report the observation of highly derived structures of the spiral ganglion in yangochiropteran bats: a trans-otic ganglion with a wall-less Rosenthal's canal. This neuroanatomical arrangement permits a larger ganglion with more neurons, higher innervation density of neurons and denser clustering of cochlear nerve fascicles7-13. This differs from the plesiomorphic neuroanatomy of Yinpterochiroptera and non-chiropteran mammals. The osteological correlates of these derived ganglion features can now be traced into bat phylogeny, providing direct evidence of how Yangochiroptera differentiated from Yinpterochiroptera in spiral ganglion neuroanatomy. These features are highly variable across major clades and between species of Yangochiroptera, and in morphospace, exhibit much greater disparity in Yangochiroptera than Yinpterochiroptera. These highly variable ganglion features may be a neuroanatomical evolutionary driver for their diverse echolocating strategies4,14-17 and are associated with the explosive diversification of yangochiropterans, which include most bat families, genera and species.
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Weiss KR, Voigt FF, Shepherd DP, Huisken J. Tutorial: practical considerations for tissue clearing and imaging. Nat Protoc 2021; 16:2732-2748. [PMID: 34021294 PMCID: PMC10542857 DOI: 10.1038/s41596-021-00502-8] [Citation(s) in RCA: 43] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Accepted: 01/18/2021] [Indexed: 02/06/2023]
Abstract
Tissue clearing has become a powerful technique for studying anatomy and morphology at scales ranging from entire organisms to subcellular features. With the recent proliferation of tissue-clearing methods and imaging options, it can be challenging to determine the best clearing protocol for a particular tissue and experimental question. The fact that so many clearing protocols exist suggests there is no one-size-fits-all approach to tissue clearing and imaging. Even in cases where a basic level of clearing has been achieved, there are many factors to consider, including signal retention, staining (labeling), uniformity of transparency, image acquisition and analysis. Despite reviews citing features of clearing protocols, it is often unknown a priori whether a protocol will work for a given experiment, and thus some optimization is required by the end user. In addition, the capabilities of available imaging setups often dictate how the sample needs to be prepared. After imaging, careful evaluation of volumetric image data is required for each combination of clearing protocol, tissue type, biological marker, imaging modality and biological question. Rather than providing a direct comparison of the many clearing methods and applications available, in this tutorial we address common pitfalls and provide guidelines for designing, optimizing and imaging in a successful tissue-clearing experiment with a focus on light-sheet fluorescence microscopy (LSFM).
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Affiliation(s)
- Kurt R Weiss
- Morgridge Institute for Research, Madison, WI, USA
| | - Fabian F Voigt
- Brain Research Institute, University of Zurich, Zurich, Switzerland
- Neuroscience Center Zurich, University of Zurich & ETH Zurich, Zurich, Switzerland
| | - Douglas P Shepherd
- Department of Physics, Arizona State University, Tempe, AZ, USA
- Center for Biological Physics, Arizona State University, Tempe, AZ, USA
| | - Jan Huisken
- Morgridge Institute for Research, Madison, WI, USA.
- Department of Integrative Biology, University of Wisconsin, Madison, WI, USA.
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5
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Steevens AR, Griesbach MW, You Y, Dutton JR, Low WC, Santi PA. Generation of inner ear sensory neurons using blastocyst complementation in a Neurog1 +/--deficient mouse. Stem Cell Res Ther 2021; 12:122. [PMID: 33579352 PMCID: PMC7881691 DOI: 10.1186/s13287-021-02184-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Accepted: 01/24/2021] [Indexed: 11/10/2022] Open
Abstract
This research is the first to produce induced pluripotent stem cell-derived inner ear sensory neurons in the Neurog1+/− heterozygote mouse using blastocyst complementation. Additionally, this approach corrected non-sensory deficits associated with Neurog1 heterozygosity, indicating that complementation is specific to endogenous Neurog1 function. This work validates the use of blastocyst complementation as a tool to create novel insight into the function of developmental genes and highlights blastocyst complementation as a potential platform for generating chimeric inner ear cell types that can be transplanted into damaged inner ears to improve hearing.
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Affiliation(s)
- Aleta R Steevens
- Department of Ophthalmology, University of Minnesota, Minneapolis, MN, USA. .,Department of Neurosurgery, University of Minnesota, Minneapolis, MN, USA. .,Stem Cell Institute, University of Minnesota, Minneapolis, MN, USA.
| | | | - Yun You
- Mouse Genetics Laboratory, University of Minnesota, Minneapolis, MN, USA
| | - James R Dutton
- Stem Cell Institute, University of Minnesota, Minneapolis, MN, USA
| | - Walter C Low
- Department of Neurosurgery, University of Minnesota, Minneapolis, MN, USA.,Stem Cell Institute, University of Minnesota, Minneapolis, MN, USA
| | - Peter A Santi
- Stem Cell Institute, University of Minnesota, Minneapolis, MN, USA.,Department of Otolaryngology, University of Minnesota, Minneapolis, MN, USA
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6
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Hutson KA, Pulver SH, Ariel P, Naso C, Fitzpatrick DC. Light sheet microscopy of the gerbil cochlea. J Comp Neurol 2020; 529:757-785. [PMID: 32632959 DOI: 10.1002/cne.24977] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2020] [Revised: 05/13/2020] [Accepted: 06/21/2020] [Indexed: 01/19/2023]
Abstract
Light sheet fluorescence microscopy (LSFM) provides a rapid and complete three-dimensional image of the cochlea. The method retains anatomical relationships-on a micrometer scale-between internal structures such as hair cells, basilar membrane (BM), and modiolus with external surface structures such as the round and oval windows. Immunolabeled hair cells were used to visualize the spiraling BM in the intact cochlea without time intensive dissections or additional histological processing; yet material prepared for LSFM could be rehydrated, the BM dissected out and reimaged at higher resolution with the confocal microscope. In immersion-fixed material, details of the cochlear vasculature were seen throughout the cochlea. Hair cell counts (both inner and outer) as well as frequency maps of the BM were comparable to those obtained by other methods, but with the added dimension of depth. The material provided measures of angular, linear, and vector distance between characteristic frequency regions along the BM. Thus, LSFM provides a unique ability to rapidly image the entire cochlea in a manner applicable to model and interpret physiological results. Furthermore, the three-dimensional organization of the cochlea can be studied at the organ and cellular level with LSFM, and this same material can be taken to the confocal microscope for detailed analysis at the subcellular level.
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Affiliation(s)
- Kendall A Hutson
- Department of Otolaryngology/Head and Neck Surgery, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Stephen H Pulver
- Department of Otolaryngology/Head and Neck Surgery, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Pablo Ariel
- Department of Pathology and Laboratory Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Caroline Naso
- Department of Otolaryngology/Head and Neck Surgery, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Douglas C Fitzpatrick
- Department of Otolaryngology/Head and Neck Surgery, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
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7
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Ekdale EG. Morphological variation among the inner ears of extinct and extant baleen whales (Cetacea: Mysticeti). J Morphol 2016; 277:1599-1615. [PMID: 27627739 DOI: 10.1002/jmor.20610] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2016] [Revised: 08/12/2016] [Accepted: 08/22/2016] [Indexed: 11/06/2022]
Abstract
Living mysticetes (baleen whales) and odontocetes (toothed whales) differ significantly in auditory function in that toothed whales are sensitive to high-frequency and ultrasonic sound vibrations and mysticetes to low-frequency and infrasonic noises. Our knowledge of the evolution and phylogeny of cetaceans, and mysticetes in particular, is at a point at which we can explore morphological and physiological changes within the baleen whale inner ear. Traditional comparative anatomy and landmark-based 3D-geometric morphometric analyses were performed to investigate the anatomical diversity of the inner ears of extinct and extant mysticetes in comparison with other cetaceans. Principal component analyses (PCAs) show that the cochlear morphospace of odontocetes is tangential to that of mysticetes, but odontocetes are completely separated from mysticetes when semicircular canal landmarks are combined with the cochlear data. The cochlea of the archaeocete Zygorhiza kochii and early diverging extinct mysticetes plot within the morphospace of crown mysticetes, suggesting that mysticetes possess ancestral cochlear morphology and physiology. The PCA results indicate variation among mysticete species, although no major patterns are recovered to suggest separate hearing or locomotor regimes. Phylogenetic signal was detected for several clades, including crown Cetacea and crown Mysticeti, with the most clades expressing phylogenetic signal in the semicircular canal dataset. Brownian motion could not be excluded as an explanation for the signal, except for analyses combining cochlea and semicircular canal datasets for Balaenopteridae. J. Morphol. 277:1599-1615, 2016. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Eric G Ekdale
- Department of Biology, San Diego State University, San Diego, California.,Department of Paleontology, San Diego Natural History Museum, San Diego, California
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8
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Coumans JVF, Palanisamy SKA, McFarlane J, Moens PDJ. Proteomic and Microscopic Strategies towards the Analysis of the Cytoskeletal Networks in Major Neuropsychiatric Disorders. Int J Mol Sci 2016; 17:E581. [PMID: 27104521 PMCID: PMC4849037 DOI: 10.3390/ijms17040581] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2016] [Revised: 04/06/2016] [Accepted: 04/08/2016] [Indexed: 11/17/2022] Open
Abstract
Mental health disorders have become worldwide health priorities. It is estimated that in the next 20 years they will account for a 16 trillion United State dollars (US$) loss. Up to now, the underlying pathophysiology of psychiatric disorders remains elusive. Altered cytoskeleton proteins expression that may influence the assembly, organization and maintenance of cytoskeletal integrity has been reported in major depressive disorders, schizophrenia and to some extent bipolar disorders. The use of quantitative proteomics, dynamic microscopy and super-resolution microscopy to investigate disease-specific protein signatures holds great promise to improve our understanding of these disorders. In this review, we present the currently available quantitative proteomic approaches use in neurology, gel-based, stable isotope-labelling and label-free methodologies and evaluate their strengths and limitations. We also reported on enrichment/subfractionation methods that target the cytoskeleton associated proteins and discuss the need of alternative methods for further characterization of the neurocytoskeletal proteome. Finally, we present live cell imaging approaches and emerging dynamic microscopy technology that will provide the tools necessary to investigate protein interactions and their dynamics in the whole cells. While these areas of research are still in their infancy, they offer huge potential towards the understanding of the neuronal network stability and its modification across neuropsychiatric disorders.
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Affiliation(s)
- Joëlle V F Coumans
- School of Rural Medicine, University of New England, Armidale, NSW 2351, Australia.
| | - Suresh K A Palanisamy
- Center for Bioactive Discovery in Health and Aging, School of Science and Technology, University of New England, Armidale, NSW 2351, Australia.
| | - Jim McFarlane
- Center for Bioactive Discovery in Health and Aging, School of Science and Technology, University of New England, Armidale, NSW 2351, Australia.
| | - Pierre D J Moens
- Center for Bioactive Discovery in Health and Aging, School of Science and Technology, University of New England, Armidale, NSW 2351, Australia.
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Abstract
The inner ear of mammals consists of the cochlea, which is involved with the sense of hearing, and the vestibule and three semicircular canals, which are involved with the sense of balance. Although different regions of the inner ear contribute to different functions, the bony chambers and membranous ducts are morphologically continuous. The gross anatomy of the cochlea that has been related to auditory physiologies includes overall size of the structure, including volume and total spiral length, development of internal cochlear structures, including the primary and secondary bony laminae, morphology of the spiral nerve ganglion, and the nature of cochlear coiling, including total number of turns completed by the cochlear canal and the relative diameters of the basal and apical turns. The overall sizes, shapes, and orientations of the semicircular canals are related to sensitivity to head rotations and possibly locomotor behaviors. Intraspecific variation, primarily in the shape and orientation of the semicircular canals, may provide additional clues to help us better understand form and function of the inner ear.
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Affiliation(s)
- Eric G. Ekdale
- Department of BiologySan Diego State UniversitySan DiegoCAUSA
- Department of PaleontologySan Diego Natural History MuseumSan DiegoCAUSA
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10
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Sensor JD, Suydam R, George JC, Liberman MC, Lovano D, Rhaganti MA, Usip S, Vinyard CJ, Thewissen JGM. The spiral ganglion and Rosenthal's canal in beluga whales. J Morphol 2016; 276:1455-66. [PMID: 26769322 DOI: 10.1002/jmor.20434] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2015] [Revised: 06/03/2015] [Accepted: 07/05/2015] [Indexed: 12/20/2022]
Abstract
With the increase of human activity and corresponding increase in anthropogenic sounds in marine waters of the Arctic, it is necessary to understand its effect on the hearing of marine wildlife. We have conducted a baseline study on the spiral ganglion and Rosenthal's canal of the cochlea in beluga whales (Delphinapterus leucas) as an initial assessment of auditory anatomy and health. We present morphometric data on the length of the cochlea, number of whorls, neuron densities along its length, Rosenthal's canal length, and cross-sectional area, and show some histological results. In belugas, Rosenthal's canal is not a cylinder of equal cross-sectional area, but its cross-section is greatest near the apex of the basal whorl. We found systematic variation in the numbers of neurons along the length of the spiral ganglion, indicating that neurons are not dispersed evenly in Rosenthal's canal. These results provide data on functionally important structural parameters of the beluga ear. We observed no signs of acoustic trauma in our sample of beluga whales.
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Affiliation(s)
- Jennifer D Sensor
- Department of Anatomy and Neurobiology, Northeast Ohio Medical University, Rootstown, Ohio, 44240
| | - Robert Suydam
- Department of Wildlife Management, North Slope Borough, Barrow, Alaska, 99723
| | - John C George
- Department of Wildlife Management, North Slope Borough, Barrow, Alaska, 99723
| | - M C Liberman
- Department of Otology and Laryngology, Harvard Medical School, Boston, Massachusetts, 02115.,Eaton-Peabody Laboratories Massachusetts Eye and Ear Infirmary, Boston, Massachusetts, 02114
| | - Denise Lovano
- Department of Anatomy and Neurobiology, Northeast Ohio Medical University, Rootstown, Ohio, 44240
| | - Mary Ann Rhaganti
- Department of Anthropology, Kent State University, Kent, Ohio, 44240
| | - Sharon Usip
- Department of Anatomy and Neurobiology, Northeast Ohio Medical University, Rootstown, Ohio, 44240
| | - Christopher J Vinyard
- Department of Anatomy and Neurobiology, Northeast Ohio Medical University, Rootstown, Ohio, 44240
| | - J G M Thewissen
- Department of Anatomy and Neurobiology, Northeast Ohio Medical University, Rootstown, Ohio, 44240
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11
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Goodrich LV. Early Development of the Spiral Ganglion. THE PRIMARY AUDITORY NEURONS OF THE MAMMALIAN COCHLEA 2016. [DOI: 10.1007/978-1-4939-3031-9_2] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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12
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Comparison of traditional histology and TSLIM optical sectioning of human temporal bones. Otol Neurotol 2015; 35:1145-9. [PMID: 24914787 DOI: 10.1097/mao.0000000000000416] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
HYPOTHESIS Thin-sheet laser imaging microscopy (TSLIM) optical sectioning can be used to assess temporal bone soft tissue morphology before celloidin sectioning. BACKGROUND Traditional human temporal bone (TB) celloidin embedding and sectioning is a lengthy and involved process. Although bone morphology can be assessed with microCT before traditional histology, soft tissue structures are difficult to resolve until after celloidin sectioning. A potential solution is TSLIM, a high-resolution, nondestructive optical sectioning technique first developed to image bone and soft tissue in animal cochleae. METHODS Two temporal bones from 1 individual were used to evaluate TSLIM's capacity to image human temporal bones (bone and soft tissue) before traditional histology. The right TB was trimmed to the cochlea, prepared for and imaged with TSLIM, then processed for celloidin sectioning. The left TB, serving as a control, was directly prepared for traditional celloidin sectioning. RESULTS TSLIM imaging of the right TB showed adequate resolution of all major tissue structures but barely resolved cells. Celloidin sections produced from the TSLIM-imaged right TB were equivalent in cytologic detail to those from the traditionally prepared left TB. TSLIM 3-dimensional (3D) reconstructions were superior to those obtained from celloidin sections because TSLIM produced many more sections that were without mechanical sectioning artifacts or alignment issues. CONCLUSION TSLIM processing disturbs neither gross nor detailed morphology and integrates well with celloidin histology, making it an ideal method to image soft tissue before celloidin sectioning.
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13
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Schmitz HM, Johnson SB, Santi PA. Kanamycin-furosemide ototoxicity in the mouse cochlea: a 3-dimensional analysis. Otolaryngol Head Neck Surg 2014; 150:666-72. [PMID: 24415490 DOI: 10.1177/0194599813519071] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
OBJECTIVE Administration of an aminoglycoside antibiotic and loop diuretic causes damage to hair cells in the organ of Corti, resulting in their death and the death of their corresponding spiral ganglion neurons. While this phenomenon has been studied previously, analysis of its effects in the whole cochlea has not been reported. The authors sought to evaluate the effects of a combination dose of kanamycin and furosemide in mice cochlea using an imaging system and computer analysis that allowed for nondestructive, whole-cochlea visualization. STUDY DESIGN Study using an animal model. SETTING Cochlear analysis laboratory. SUBJECTS AND METHODS Five mice received kanamycin and furosemide and 3 mice received saline. Cochleas were harvested and imaged with scanning thin-sheet laser imaging microscopy (sTSLIM) to analyze sensory cells and cochlea structures. RESULTS The drug-treated animals showed substantial loss of inner hair cells and complete outer hair cell loss. All treated mice showed spiral ganglion neuron loss with fewer neurons than control animals and decreased cell density in the middle turn of the cochlea. The spiral ligament and spiral limbus in the treated animals also showed a decrease in fibrocyte cell density in the middle to apical portion of the cochlea. The stria vascularis appeared normal in all animals. CONCLUSION Imaging methods that allow for whole-cochlea analysis provide insight into changes that occur in the cochlea after ototoxic insult. Trends that may not be apparent in cross-section samples of the cochlea can be observed. Computer analysis of these trends allows them to be assessed accurately.
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Affiliation(s)
- Heather M Schmitz
- Department of Otolaryngology, University of Minnesota, Minneapolis, Minnesota, USA
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14
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Wrzeszcz A, Reuter G, Nolte I, Lenarz T, Scheper V. Spiral ganglion neuron quantification in the guinea pig cochlea using Confocal Laser Scanning Microscopy compared to embedding methods. Hear Res 2013; 306:145-55. [PMID: 23968822 DOI: 10.1016/j.heares.2013.08.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/13/2013] [Revised: 07/10/2013] [Accepted: 08/06/2013] [Indexed: 12/16/2022]
Abstract
Neuron counting in the cochlea is a crucial but time-consuming operation for which various methods have been developed. To improve simplicity and efficiency, we tested an imaging method of the cochlea, and based on Confocal Laser Scanning Microscopy (CLSM), we visualised Rosenthal's Canal and quantified the spiral ganglion neurons (SGN) within. Cochleae of 8 normal hearing guinea pigs and one implanted with a silicone filament were fixed in paraformaldehyde (PFA), decalcified, dehydrated and cleared in Spalteholz solution. Using the tissue's autofluorescence, CLSM was performed at 100 fold magnification generating z-series stacks of about 20 slices of the modiolus. In 5 midmodiolar slices per cochlea the perimeters of the Rosenthal's Canal were surveyed, representative neuron diameters were measured and the neurons first counted manually and then software-assisted. For comparison, 8 normal hearing guinea pig cochleae were embedded in paraffin and examined similarly. The CLSM method has the advantage that the cochleae remain intact as an organ and keep their geometrical structure. Z-stack creation is nearly fully-automatic and frequently repeatable with various objectives and step sizes and without visible bleaching. The tissue shows minimal or no shrinking artefacts and damage typical of embedding and sectioning. As a result, the cells in the cleared cochleae reach an average diameter of 21 μm and a density of about 18 cells/10,000 μm(2) with no significant difference between the manual and the automatical counts. Subsequently we compared the CLSM data with those generated using the established method of paraffin slides, where the SGN reached a mean density of 9.5 cells/10,000 μm(2) and a mean soma diameter of 13.6 μm. We were able to prove that the semi-automatic CLSM method is a simple and effective technique for auditory neuron count. It provides a high grade of tissue preservation and the automatic stack-generation as well as the counter software reduces the effort considerably. In addition this visualisation technique offers the potential to detect the position and orientation of cochlear implants (CI) within the cochlea and tissue growing in the scala tympani around the CI and at the position of the cochleostomy due to the fact that the implant does not have to be removed to perform histology as in case of the paraffin method.
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Affiliation(s)
- Antonina Wrzeszcz
- Department of Otolaryngology, Hannover Medical School, Carl-Neuberg-Str. 1, 30625 Hannover, Germany.
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15
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Schettino AE, Lauer AM. The efficiency of design-based stereology in estimating spiral ganglion populations in mice. Hear Res 2013; 304:153-8. [PMID: 23876522 DOI: 10.1016/j.heares.2013.07.007] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/22/2013] [Revised: 06/18/2013] [Accepted: 07/10/2013] [Indexed: 10/26/2022]
Abstract
Accurate quantification of cell populations is essential in assessing and evaluating neural survival and degeneration in experimental groups. Estimates obtained through traditional two-dimensional counting methods are heavily biased by the counting parameters in relation to the size and shape of the neurons to be counted, resulting in a large range of inaccurate counts. In contrast, counting every cell in a population can be extremely labor-intensive. The present study hypothesizes that design-based stereology provides estimates of the total number of cochlear spiral ganglion neurons (SGNs) in mice that are comparable to those obtained by other accurate cell-counting methods, such as a serial reconstruction, while being a more efficient method. SGNs are indispensable for relaying auditory information from hair cells to the auditory brainstem, and investigating factors affecting their degeneration provides insight into the physiological basis for the progression of hearing dysfunction. Stereological quantification techniques offer the benefits of efficient sampling that is independent of the size and shape of the SGNs. Population estimates of SGNs in cochleae from young C57 mice with normal-hearing and C57 mice with age-related hearing loss were obtained using the optical fractionator probe and traditional two-dimensional counting methods. The average estimated population of SGNs in normal-hearing mice was 7009, whereas the average estimated population in mice with age-related hearing loss was 5096. The estimated population of SGNs in normal-hearing mice fell within the range of values previously reported in the literature. The reduction in the SGN population in animals with age-related hearing loss was statistically significant. Stereological measurements required less time per section compared to two-dimensional methods while optimizing the amount of cochlear tissue analyzed. These findings demonstrate that design-based stereology provides a practical alternative to other counting methods such as the Abercrombie correction method, which has been shown to notably underestimate cell populations, and labor-intensive protocols that account for every cell individually.
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Affiliation(s)
- Amy E Schettino
- Center for Hearing and Balance, Dept. of Otolaryngology-Head & Neck Surgery, Johns Hopkins University, Baltimore, MD, USA; Undergraduate Program in Neuroscience, Zanvyl Kreiger School of Arts and Sciences, Johns Hopkins University, Baltimore, MD, USA
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16
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Three-dimensional histological specimen preparation for accurate imaging and spatial reconstruction of the middle and inner ear. Int J Comput Assist Radiol Surg 2013; 8:481-509. [PMID: 23633112 PMCID: PMC3702969 DOI: 10.1007/s11548-013-0825-7] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2012] [Accepted: 02/27/2013] [Indexed: 11/02/2022]
Abstract
PURPOSE This paper presents a highly accurate cross-sectional preparation technique. The research aim was to develop an adequate imaging modality for both soft and bony tissue structures featuring high contrast and high resolution. Therefore, the advancement of an already existing micro-grinding procedure was pursued. The central objectives were to preserve spatial relations and to ensure the accurate three-dimensional reconstruction of histological sections. METHODS Twelve human temporal bone specimens including middle and inner ear structures were utilized. They were embedded in epoxy resin, then dissected by serial grinding and finally digitalized. The actual abrasion of each grinding slice was measured using a tactile length gauge with an accuracy of one micrometre. The cross-sectional images were aligned with the aid of artificial markers and by applying a feature-based, custom-made auto-registration algorithm. To determine the accuracy of the overall reconstruction procedure, a well-known reference object was used for comparison. To ensure the compatibility of the histological data with conventional clinical image data, the image stacks were finally converted into the DICOM standard. RESULTS The image fusion of data from temporal bone specimens' and from non-destructive flat-panel-based volume computed tomography confirmed the spatial accuracy achieved by the procedure, as did the evaluation using the reference object. CONCLUSION This systematic and easy-to-follow preparation technique enables the three-dimensional (3D) histological reconstruction of complex soft and bony tissue structures. It facilitates the creation of detailed and spatially correct 3D anatomical models. Such models are of great benefit for image-based segmentation and planning in the field of computer-assisted surgery as well as in finite element analysis. In the context of human inner ear surgery, three-dimensional histology will improve the experimental evaluation and determination of intra-cochlear trauma after the insertion of an electrode array of a cochlear implant system.
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Kopecky BJ, Duncan JS, Elliott KL, Fritzsch B. Three-dimensional reconstructions from optical sections of thick mouse inner ears using confocal microscopy. J Microsc 2013; 248:292-8. [PMID: 23140378 DOI: 10.1111/j.1365-2818.2012.03673.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Three-dimensional (3D) reconstructions of the vertebrate inner ear have provided novel insights into the development of this complex organ. 3D reconstructions enable superior analysis of phenotypic differences between wild type and mutant ears but can result in laborious work when reconstructed from physically sectioned material. Although nondestructive optical sectioning light sheet microscopy may ultimately prove the ideal solution, these technologies are not yet commercially available, or in many instances are not monetarily feasible. Here we introduce a simple technique to image a fluorescently labelled ear at different stages throughout development at high resolution enabling 3D reconstruction of any component of the inner ear using confocal microscopy. We provide a step-by-step manual from tissue preparation to imaging to 3D reconstruction and analysis including a rationale and troubleshooting guide at each step for researchers with different equipment, protocols, and access to resources to successfully incorporate the principles of this method and customize them to their laboratory settings.
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Affiliation(s)
- B J Kopecky
- Department of Biology, University of Iowa, Iowa City, Iowa, USA.
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Rau C, Hwang M, Lee WK, Richter CP. Quantitative X-ray tomography of the mouse cochlea. PLoS One 2012; 7:e33568. [PMID: 22485145 PMCID: PMC3317668 DOI: 10.1371/journal.pone.0033568] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2011] [Accepted: 02/13/2012] [Indexed: 11/29/2022] Open
Abstract
Imaging with hard X-rays allows visualizing cochlear structures while maintaining intrinsic qualities of the tissue, including structure and size. With coherent X-rays, soft tissues, including membranes, can be imaged as well as cells making use of the so-called in-line phase contrast. In the present experiments, partially coherent synchrotron radiation has been used for micro-tomography. Three-dimensional reconstructions of the mouse cochlea have been created using the EM3D software and the volume has been segmented in the Amira Software Suite. The structures that have been reconstructed include scala tympani, scala media, scala vestibuli, Reissner's membrane, basilar membrane, tectorial membrane, organ of Corti, spiral limbus, spiral ganglion and cochlear nerve. Cross-sectional areas of the scalae were measured. The results provide a realistic and quantitative reconstruction of the cochlea.
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Affiliation(s)
- Christoph Rau
- Diamond Light Source Ltd, Diamond House, Harwell Science and Innovation Campus, Didcot, United Kingdom.
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Kopecky B, Johnson S, Schmitz H, Santi P, Fritzsch B. Scanning thin-sheet laser imaging microscopy elucidates details on mouse ear development. Dev Dyn 2012; 241:465-80. [PMID: 22271591 DOI: 10.1002/dvdy.23736] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/02/2012] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND The mammalian inner ear is transformed from a flat placode into a three-dimensional (3D) structure with six sensory epithelia that allow for the perception of sound and both linear and angular acceleration. While hearing and balance problems are typically considered to be adult onset diseases, they may arise as a developmental perturbation to the developing ear. Future prevention of hearing or balance loss requires an understanding of how closely genetic mutations in model organisms reflect the human case, necessitating an objective multidimensional comparison of mouse ears with human ears that have comparable mutations in the same gene. RESULTS Here, we present improved 3D analyses of normal murine ears during embryonic development using optical sections obtained through Thin-Sheet Laser Imaging Microscopy. We chronicle the transformation of an undifferentiated otic vesicle between mouse embryonic day 11.5 to a fully differentiated inner ear at postnatal day 15. CONCLUSIONS Our analysis of ear development provides new insights into ear development, enables unique perspectives into the complex development of the ear, and allows for the first full quantification of volumetric and linear aspects of ear growth. Our data provide the framework for future analysis of mutant phenotypes that are currently under-appreciated using only two dimensional renderings.
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Affiliation(s)
- Benjamin Kopecky
- Department of Biology, University of Iowa, Iowa City, Iowa 52242, USA.
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