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Novel insights into inner ear development and regeneration for targeted hearing loss therapies. Hear Res 2019; 397:107859. [PMID: 31810596 DOI: 10.1016/j.heares.2019.107859] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Revised: 11/06/2019] [Accepted: 11/25/2019] [Indexed: 02/06/2023]
Abstract
Sensorineural hearing loss is the most common sensory deficit in humans. Despite the global scale of the problem, only limited treatment options are available today. The mammalian inner ear is a highly specialized postmitotic organ, which lacks proliferative or regenerative capacity. Since the discovery of hair cell regeneration in non-mammalian species however, much attention has been placed on identifying possible strategies to reactivate similar responses in humans. The development of successful regenerative approaches for hearing loss strongly depends on a detailed understanding of the mechanisms that control human inner ear cellular specification, differentiation and function, as well as on the development of robust in vitro cellular assays, based on human inner ear cells, to study these processes and optimize therapeutic interventions. We summarize here some aspects of inner ear development and strategies to induce regeneration that have been investigated in rodents. Moreover, we discuss recent findings in human inner ear development and compare the results with findings from animal models. Finally, we provide an overview of strategies for in vitro generation of human sensory cells from pluripotent and somatic progenitors that may provide a platform for drug development and validation of therapeutic strategies in vitro.
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Silva SA, Maass JC. p27 Kip1 down-regulation as achieved by two clinically feasible means did not induce proliferation of supporting cells in the rat neonatal cochlea in vivo. Hear Res 2018; 373:10-22. [PMID: 30578960 DOI: 10.1016/j.heares.2018.12.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/13/2017] [Revised: 11/27/2018] [Accepted: 12/04/2018] [Indexed: 12/24/2022]
Abstract
In mammals, the cochlear sensory epithelium becomes quiescent early during development. After the first postnatal week, there is no cell replacement or proliferation, and severe damage leads to permanent deafness. Supporting cells' trans-differentiation has been suggested as a way to regenerate cochlear hair cells after damage. However, they are also needed for proper functionality. Cdkn1b (p27Kip1) participates in the cochlear terminal mitosis state achieved during development. Its expression is maintained in adult supporting cells and its postnatal deletion has induced cochlear proliferation in vitro and in vivo. Therefore, its manipulation has been proposed as a feasible way to induce proliferation of supporting cells after birth. Nevertheless, the literature is scarce regarding feasible methods to directly decrease p27Kip1 in the clinical domain. The effects of p27Kip1 knockdown using viral vectors are not completely elucidated and no pharmacological approaches to decrease p27Kip1 in the cochlea have been tested in vivo before. This study explores the ability of p27Kip1 messenger knockdown and pharmacological transcriptional inhibition to induce proliferation of supporting cells in the P0 neonatal rat cochlea in vivo. Respectively, lentiviral vectors transducing shRNA against p27Kip1 were administered into the scala media or Alsterpaullone 2-Cyanoethyl into the round window niche. Cell markers and gene expression were assessed through immunostaining and qRT-PCR. Despite both methods significantly decreasing p27Kip1 expression in vivo, signs of toxicity in the organ of Corti were not found; however, relevant proliferation was not found either. Finally, cochlear damage was added to increase the response in vitro, achieving only a mild to moderate proliferation induction. We conclude that our approaches were not able to stimulate the recall of supporting cell proliferation despite significantly decreased p27Kip1 levels in vivo. Considering the evaluation of the cochlea at a very responsive stage, we propose that the level of isolated modification of p27Kip1 expression in living mammals achievable through these approaches is insufficient to induce proliferation of supporting cells. Future proliferation induction experiments in the cochlea should study other methods and genes.
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Affiliation(s)
- Sebastián A Silva
- Department of Otolaryngology, Hospital Clínico Universidad de Chile and Interdisciplinary Program of Physiology and Biophysics, Institute of Biomedical Sciences (ICBM), Faculty of Medicine, Universidad de Chile, Av. Independencia 1027, 8380453, Independencia, Santiago, Chile
| | - Juan C Maass
- Department of Otolaryngology, Hospital Clínico Universidad de Chile and Interdisciplinary Program of Physiology and Biophysics, Institute of Biomedical Sciences (ICBM), Faculty of Medicine, Universidad de Chile, Av. Independencia 1027, 8380453, Independencia, Santiago, Chile; Department of Otolaryngology, Clínica Alemana de Santiago, Facultad de Medicina Clínica Alemana-Universidad del Desarrollo, Av. Vitacura 5951, 7650568, Vitacura, Santiago, Chile.
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Kanzaki S. Gene Delivery into the Inner Ear and Its Clinical Implications for Hearing and Balance. Molecules 2018; 23:molecules23102507. [PMID: 30274337 PMCID: PMC6222543 DOI: 10.3390/molecules23102507] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2018] [Revised: 09/04/2018] [Accepted: 09/14/2018] [Indexed: 11/16/2022] Open
Abstract
The inner ear contains many types of cell, including sensory hair cells and neurons. If these cells are damaged, they do not regenerate. Inner ear disorders have various etiologies. Some are related to aging or are idiopathic, as in sudden deafness. Others occur due to acoustic trauma, exposure to ototoxic drugs, viral infections, immune responses, or endolymphatic hydrops (Meniere's disease). For these disorders, inner ear regeneration therapy is expected to be a feasible alternative to cochlear implants for hearing recovery. Recently, the mechanisms underlying inner ear regeneration have been gradually clarified. Inner ear cell progenitors or stem cells have been identified. Factors necessary for regeneration have also been elucidated from the mechanism of hair cell generation. Inducing differentiation of endogenous stem cells or inner ear stem cell transplantation is expected. In this paper, we discuss recent approaches to hair cell proliferation and differentiation for inner ear regeneration. We discuss the future road map for clinical application. The therapies mentioned above require topical administration of transgenes or drug onto progenitors of sensory cells. Developing efficient and safe modes of administration is clinically important. In this regard, we also discuss our development of an inner ear endoscope to facilitate topical administration.
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Affiliation(s)
- Sho Kanzaki
- Department of Otolaryngology Head and Neck Surgery, School of Medicine, KEIO University, Tokyo 160-8582, Japan.
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Lee MY, Park YH. Potential of Gene and Cell Therapy for Inner Ear Hair Cells. BIOMED RESEARCH INTERNATIONAL 2018; 2018:8137614. [PMID: 30009175 PMCID: PMC6020521 DOI: 10.1155/2018/8137614] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/10/2018] [Revised: 04/11/2018] [Accepted: 05/15/2018] [Indexed: 02/06/2023]
Abstract
Sensorineural hearing loss is caused by the loss of sensory hair cells (HCs) or a damaged afferent nerve pathway to the auditory cortex. The most common option for the treatment of sensorineural hearing loss is hearing rehabilitation using hearing devices. Various kinds of hearing devices are available but, despite recent advancements, their perceived sound quality does not mimic that of the "naïve" cochlea. Damage to crucial cochlear structures is mostly irreversible and results in permanent hearing loss. Cochlear HC regeneration has long been an important goal in the field of hearing research. However, it remains challenging because, thus far, no medical treatment has successfully regenerated cochlear HCs. Recent advances in genetic modulation and developmental techniques have led to novel approaches to generating HCs or protecting against HC loss, to preserve hearing. In this review, we present and review the current status of two different approaches to restoring or protecting hearing, gene therapy, including the newly introduced CRISPR/Cas9 genome editing, and stem cell therapy, and suggest the future direction.
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Affiliation(s)
- Min Yong Lee
- Department of Otorhinolaryngology and Head & Neck Surgery, Dankook University Hospital, Cheonan, Chungnam, Republic of Korea
| | - Yong-Ho Park
- Department of Otolaryngology-Head and Neck Surgery, College of Medicine, Chungnam National University, Daejeon, Republic of Korea
- Brain Research Institute, College of Medicine, Chungnam National University, Daejeon, Republic of Korea
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5
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Regenerative medicine in hearing recovery. Cytotherapy 2017; 19:909-915. [DOI: 10.1016/j.jcyt.2017.04.008] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2017] [Revised: 03/24/2017] [Accepted: 04/21/2017] [Indexed: 12/20/2022]
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Cristóbal Maass J, Hanuch F, Ormazábal M. AVANCES EN REGENERACIÓN AUDITIVA. ESTADO ACTUAL Y PERSPECTIVAS FUTURAS. REVISTA MÉDICA CLÍNICA LAS CONDES 2016. [DOI: 10.1016/j.rmclc.2016.10.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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Riccardi S, Bergling S, Sigoillot F, Beibel M, Werner A, Leighton-Davies J, Knehr J, Bouwmeester T, Parker CN, Roma G, Kinzel B. MiR-210 promotes sensory hair cell formation in the organ of corti. BMC Genomics 2016; 17:309. [PMID: 27121005 PMCID: PMC4848794 DOI: 10.1186/s12864-016-2620-7] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2015] [Accepted: 04/14/2016] [Indexed: 12/20/2022] Open
Abstract
Background Hearing loss is the most common sensory defect afflicting several hundred million people worldwide. In most cases, regardless of the original cause, hearing loss is related to the degeneration and death of hair cells and their associated spiral ganglion neurons. Despite this knowledge, relatively few studies have reported regeneration of the auditory system. Significant gaps remain in our understanding of the molecular mechanisms underpinning auditory function, including the factors required for sensory cell regeneration. Recently, the identification of transcriptional activators and repressors of hair cell fate has been augmented by the discovery of microRNAs (miRNAs) associated with hearing loss. As miRNAs are central players of differentiation and cell fate, identification of miRNAs and their gene targets may reveal new pathways for hair cell regeneration, thereby providing new avenues for the treatment of hearing loss. Results In order to identify new genetic elements enabling regeneration of inner ear sensory hair cells, next-generation miRNA sequencing (miRSeq) was used to identify the most prominent miRNAs expressed in the mouse embryonic inner ear cell line UB/OC-1 during differentiation towards a hair cell like phenotype. Based on these miRSeq results eight most differentially expressed miRNAs were selected for further characterization. In UB/OC-1, miR-210 silencing in vitro resulted in hair cell marker expression, whereas ectopic expression of miR-210 resulted in new hair cell formation in cochlear explants. Using a lineage tracing mouse model, transdifferentiation of supporting epithelial cells was identified as the likely mechanism for this new hair cell formation. Potential miR-210 targets were predicted in silico and validated experimentally using a miR-trap approach. Conclusion MiRSeq followed by ex vivo validation revealed miR-210 as a novel factor driving transdifferentiation of supporting epithelial cells to sensory hair cells suggesting that miR-210 might be a potential new factor for hearing loss therapy. In addition, identification of inner ear pathways regulated by miR-210 identified potential new drug targets for the treatment of hearing loss. Electronic supplementary material The online version of this article (doi:10.1186/s12864-016-2620-7) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Sabrina Riccardi
- Developmental and Molecular Pathways, Novartis Institute for Biomedical Research, Basel, Switzerland
| | - Sebastian Bergling
- Developmental and Molecular Pathways, Novartis Institute for Biomedical Research, Basel, Switzerland
| | - Frederic Sigoillot
- Developmental and Molecular Pathways, Novartis Institute for Biomedical Research, Cambridge, USA
| | - Martin Beibel
- Developmental and Molecular Pathways, Novartis Institute for Biomedical Research, Basel, Switzerland
| | - Annick Werner
- Developmental and Molecular Pathways, Novartis Institute for Biomedical Research, Basel, Switzerland
| | - Juliet Leighton-Davies
- Developmental and Molecular Pathways, Novartis Institute for Biomedical Research, Basel, Switzerland
| | - Judith Knehr
- Developmental and Molecular Pathways, Novartis Institute for Biomedical Research, Basel, Switzerland
| | - Tewis Bouwmeester
- Developmental and Molecular Pathways, Novartis Institute for Biomedical Research, Basel, Switzerland
| | - Christian N Parker
- Developmental and Molecular Pathways, Novartis Institute for Biomedical Research, Basel, Switzerland
| | - Guglielmo Roma
- Developmental and Molecular Pathways, Novartis Institute for Biomedical Research, Basel, Switzerland
| | - Bernd Kinzel
- Developmental and Molecular Pathways, Novartis Institute for Biomedical Research, Basel, Switzerland.
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Basch ML, Brown RM, Jen H, Groves AK. Where hearing starts: the development of the mammalian cochlea. J Anat 2016; 228:233-54. [PMID: 26052920 PMCID: PMC4718162 DOI: 10.1111/joa.12314] [Citation(s) in RCA: 81] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/14/2015] [Indexed: 12/11/2022] Open
Abstract
The mammalian cochlea is a remarkable sensory organ, capable of perceiving sound over a range of 10(12) in pressure, and discriminating both infrasonic and ultrasonic frequencies in different species. The sensory hair cells of the mammalian cochlea are exquisitely sensitive, responding to atomic-level deflections at speeds on the order of tens of microseconds. The number and placement of hair cells are precisely determined during inner ear development, and a large number of developmental processes sculpt the shape, size and morphology of these cells along the length of the cochlear duct to make them optimally responsive to different sound frequencies. In this review, we briefly discuss the evolutionary origins of the mammalian cochlea, and then describe the successive developmental processes that lead to its induction, cell cycle exit, cellular patterning and the establishment of topologically distinct frequency responses along its length.
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Affiliation(s)
- Martin L. Basch
- Department of NeuroscienceBaylor College of MedicineHoustonTXUSA
| | - Rogers M. Brown
- Program in Developmental BiologyBaylor College of MedicineHoustonTXUSA
| | - Hsin‐I Jen
- Program in Developmental BiologyBaylor College of MedicineHoustonTXUSA
| | - Andrew K. Groves
- Department of NeuroscienceBaylor College of MedicineHoustonTXUSA
- Program in Developmental BiologyBaylor College of MedicineHoustonTXUSA
- Department of Molecular and Human GeneticsBaylor College of MedicineHoustonTXUSA
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9
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Monroe JD, Rajadinakaran G, Smith ME. Sensory hair cell death and regeneration in fishes. Front Cell Neurosci 2015; 9:131. [PMID: 25954154 PMCID: PMC4404912 DOI: 10.3389/fncel.2015.00131] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2015] [Accepted: 03/21/2015] [Indexed: 01/31/2023] Open
Abstract
Sensory hair cells are specialized mechanotransductive receptors required for hearing and vestibular function. Loss of hair cells in humans and other mammals is permanent and causes reduced hearing and balance. In the early 1980’s, it was shown that hair cells continue to be added to the inner ear sensory epithelia in cartilaginous and bony fishes. Soon thereafter, hair cell regeneration was documented in the chick cochlea following acoustic trauma. Since then, research using chick and other avian models has led to great insights into hair cell death and regeneration. However, with the rise of the zebrafish as a model organism for studying disease and developmental processes, there has been an increased interest in studying sensory hair cell death and regeneration in its lateral line and inner ears. Advances derived from studies in zebrafish and other fish species include understanding the effect of ototoxins on hair cells and finding otoprotectants to mitigate ototoxin damage, the role of cellular proliferation vs. direct transdifferentiation during hair cell regeneration, and elucidating cellular pathways involved in the regeneration process. This review will summarize research on hair cell death and regeneration using fish models, indicate the potential strengths and weaknesses of these models, and discuss several emerging areas of future studies.
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Affiliation(s)
- Jerry D Monroe
- Department of Biology, Western Kentucky University Bowling Green, KY, USA
| | - Gopinath Rajadinakaran
- Department of Genetics and Genome Sciences, University of Connecticut Health Center Farmington, CT, USA
| | - Michael E Smith
- Department of Biology, Western Kentucky University Bowling Green, KY, USA
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Auditory hair cell-specific deletion of p27Kip1 in postnatal mice promotes cell-autonomous generation of new hair cells and normal hearing. J Neurosci 2015; 34:15751-63. [PMID: 25411503 DOI: 10.1523/jneurosci.3200-14.2014] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Hearing in mammals relies upon the transduction of sound by hair cells (HCs) in the organ of Corti within the cochlea of the inner ear. Sensorineural hearing loss is a widespread and permanent disability due largely to a lack of HC regeneration in mammals. Recent studies suggest that targeting the retinoblastoma (Rb)/E2F pathway can elicit proliferation of auditory HCs. However, previous attempts to induce HC proliferation in this manner have resulted in abnormal cochlear morphology, HC death, and hearing loss. Here we show that cochlear HCs readily proliferate and survive following neonatal, HC-specific, conditional knock-out of p27(Kip1) (p27CKO), a tumor suppressor upstream of Rb. Indeed, HC-specific p27CKO results in proliferation of these cells without the upregulation of the supporting cell or progenitor cell proteins, Prox1 or Sox2, suggesting that they remain HCs. Furthermore, p27CKO leads to a significant addition of postnatally derived HCs that express characteristic synaptic and stereociliary markers and survive to adulthood, although a portion of the newly derived inner HCs exhibit cytocauds and lack VGlut3 expression. Despite this, p27CKO mice exhibit normal hearing as measured by evoked auditory brainstem responses, which suggests that the newly generated HCs may contribute to, or at least do not greatly detract from, function. These results show that p27(Kip1) actively maintains HC quiescence in postnatal mice, and suggest that inhibition of p27(Kip1) in residual HCs represents a potential strategy for cell-autonomous auditory HC regeneration.
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11
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Kohrman DC, Raphael Y. Gene therapy for deafness. Gene Ther 2013; 20:1119-23. [PMID: 23864018 PMCID: PMC4113964 DOI: 10.1038/gt.2013.39] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2013] [Revised: 06/06/2013] [Accepted: 06/10/2013] [Indexed: 12/18/2022]
Abstract
Hearing loss is the most common sensory deficit in humans and can result from genetic, environmental or combined etiologies that prevent normal function of the cochlea, the peripheral sensory organ. Recent advances in understanding the genetic pathways that are critical for the development and maintenance of cochlear function, as well as the molecular mechanisms that underlie cell trauma and death, have provided exciting opportunities for modulating these pathways to correct genetic mutations, to enhance the endogenous protective pathways for hearing preservation and to regenerate lost sensory cells with the possibility of ameliorating hearing loss. A number of recent animal studies have used gene-based therapies in innovative ways toward realizing these goals. With further refinement, some of the protective and regenerative approaches reviewed here may become clinically applicable.
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Affiliation(s)
- D C Kohrman
- Department of Otolaryngology-Head and Neck Surgery, Kresge Hearing Research Institute, The University of Michigan, Ann Arbor, MI, USA
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12
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Abstract
Sensory hair cells are exquisitely sensitive vertebrate mechanoreceptors that mediate the senses of hearing and balance. Understanding the factors that regulate the development of these cells is important, not only to increase our understanding of ear development and its functional physiology but also to shed light on how these cells may be replaced therapeutically. In this review, we describe the signals and molecular mechanisms that initiate hair cell development in vertebrates, with particular emphasis on the transcription factor Atoh1, which is both necessary and sufficient for hair cell development. We then discuss recent findings on how microRNAs may modulate the formation and maturation of hair cells. Last, we review recent work on how hair cells are regenerated in many vertebrate groups and the factors that conspire to prevent this regeneration in mammals.
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Affiliation(s)
- Andrew K Groves
- Department of Neuroscience, Baylor College of Medicine, Houston, TX 77030, USA.
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Coupling the cell cycle to development and regeneration of the inner ear. Semin Cell Dev Biol 2013; 24:507-13. [PMID: 23665151 DOI: 10.1016/j.semcdb.2013.04.004] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2013] [Accepted: 04/23/2013] [Indexed: 12/19/2022]
Abstract
Cell cycle exit and acquirement of a postmitotic state is essential for the proper development of organs. In the present review, we examine the role of the cell cycle control in the sensory epithelia of the mammalian inner ear. We describe the roles of the core cell cycle regulators in the proliferation of prosensory cells and in the initiation and maintenance of terminal mitosis of the sensory epithelia. We also discuss how other intracellular signalling may influence the cell cycle. Finally, we address the question of whether manipulations of the cell cycle may have the potential to create replacement cells for the damaged inner sensory epithelia.
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Maass JC, Berndt FA, Cánovas J, Kukuljan M. p27Kip1 knockdown induces proliferation in the organ of Corti in culture after efficient shRNA lentiviral transduction. J Assoc Res Otolaryngol 2013; 14:495-508. [PMID: 23612739 DOI: 10.1007/s10162-013-0383-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2012] [Accepted: 02/25/2013] [Indexed: 12/15/2022] Open
Abstract
The cells in the organ of Corti do not exhibit spontaneous cell regeneration; hair cells that die after damage are not replaced. Supporting cells can be induced to transdifferentiate into hair cells, but that would deplete their numbers, therefore impairing epithelium physiology. The loss of p27Kip1 function induces proliferation in the organ of Corti, which raises the possibility to integrate it to the strategies to achieve regeneration. Nevertheless, it is not known if the extent of this proliferative potential, as well as its maintenance in postnatal stages, is compatible with providing a basis for eventual therapeutic manipulation. This is due in part to the limited success of approaches to deliver tools to modify gene expression in the auditory epithelium. We tested the hypothesis that the organ of Corti can undergo significant proliferation when efficient manipulation of the expression of regulators of the cell cycle is achieved. Lentiviral vectors were used to transduce all cochlear cell types, with efficiencies around 4 % for hair cells, 43 % in the overall supporting cell population, and 74 % within lesser epithelial ridge (LER) cells. Expression of short hairpin RNA targeting p27Kip1 encoded by the lentiviral vectors led to measurable proliferation in the organ of Corti and increase in LER cells number but not hair cell regeneration. Our results revalidate the use of lentiviral vectors in the study and in the potential therapeutic approaches for inner ear diseases, as well as demonstrate that efficient manipulation of p27Kip1 is sufficient to induce significant proliferation in the postnatal cochlea.
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Affiliation(s)
- Juan C Maass
- Program in Physiology and Biophysics, Institute for Biomedical Sciences, Faculty of Medicine, Universidad de Chile, Av. Independencia 1027, Independencia, Santiago, Chile.
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MYC gene delivery to adult mouse utricles stimulates proliferation of postmitotic supporting cells in vitro. PLoS One 2012; 7:e48704. [PMID: 23119091 PMCID: PMC3484123 DOI: 10.1371/journal.pone.0048704] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2012] [Accepted: 10/01/2012] [Indexed: 01/01/2023] Open
Abstract
The inner ears of adult humans and other mammals possess a limited capacity for regenerating sensory hair cells, which can lead to permanent auditory and vestibular deficits. During development and regeneration, undifferentiated supporting cells within inner ear sensory epithelia can self-renew and give rise to new hair cells; however, these otic progenitors become depleted postnatally. Therefore, reprogramming differentiated supporting cells into otic progenitors is a potential strategy for restoring regenerative potential to the ear. Transient expression of the induced pluripotency transcription factors, Oct3/4, Klf4, Sox2, and c-Myc reprograms fibroblasts into neural progenitors under neural-promoting culture conditions, so as a first step, we explored whether ectopic expression of these factors can reverse supporting cell quiescence in whole organ cultures of adult mouse utricles. Co-infection of utricles with adenoviral vectors separately encoding Oct3/4, Klf4, Sox2, and the degradation-resistant T58A mutant of c-Myc (c-MycT58A) triggered significant levels of supporting cell S-phase entry as assessed by continuous BrdU labeling. Of the four factors, c-MycT58A alone was both necessary and sufficient for the proliferative response. The number of BrdU-labeled cells plateaued between 5–7 days after infection, and then decreased ∼60% by 3 weeks, as many cycling cells appeared to enter apoptosis. Switching to differentiation-promoting culture medium at 5 days after ectopic expression of c-MycT58A temporarily attenuated the loss of BrdU-labeled cells and accompanied a very modest but significant expansion of the sensory epithelium. A small number of the proliferating cells in these cultures labeled for the hair cell marker, myosin VIIA, suggesting they had begun differentiating towards a hair cell fate. The results indicate that ectopic expression of c-MycT58A in combination with methods for promoting cell survival and differentiation may restore regenerative potential to supporting cells within the adult mammalian inner ear.
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Okumura H, Miyasaka Y, Morita Y, Nomura T, Mishima Y, Takahashi S, Kominami R. Bcl11b heterozygosity leads to age-related hearing loss and degeneration of outer hair cells of the mouse cochlea. Exp Anim 2011; 60:355-61. [PMID: 21791875 DOI: 10.1538/expanim.60.355] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
BCL11B/CTIP2 zinc-finger transcription factor is expressed in various types of cells in many different tissues. This study showed that BCL11B is expressed in the nucleus of the outer hair cells of the mouse cochlea, degeneration of which is known to cause deafness and presbycusis or age-related hearing loss (AHL). We tested whether or not Bcl11b heterozygosity would affect AHL in mice. Analysis of auditory brainstem responses revealed AHL in Bcl11b (+/-) heterozygous, but not wild-type, mice, which was evident as early as 3 months after birth. Histological abnormalities were observed in the outer hair cells of the Bcl11b (+/-) mice at 6 months of age with hearing loss. These results suggest that the AHL observed in Bcl11b (+/-) mice is the result of impairment of the outer hair cells and that BCL11B activity is required for the maintenance of outer hair cells and normal hearing.
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Affiliation(s)
- Hitoshi Okumura
- Department of Molecular Genetics, Graduate School of Medical and Dental Sciences, Niigata University, 1–757 Asahimachi, Niigata 951-8510, Japan
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Abstract
PURPOSE p27kip1 is well-known as a cell cycle inhibitor and also plays an important role for cell differentiation. We hypothesized that if we caused retinal degeneration in a p27(-/-) mouse, then the appropriate method of restoration may be different from that of wild mice and therefore suggest a therapeutic methodology for retinal regeneration. METHODS Histological and electrophysiological (ERG) examination was performed on p27(-/-) mice retina. We injected N-methy-N-nitrosourea (MNU) to induce retinal degeneration. BrdU was used to identify the dividing cells in the retina. RESULTS Thicker retina were observed in the p27(-/-) mice when compared to those of the p27(-/+) mice or wild type mice. Almost all retinal layers were thick and optic nerves were also enlarged. A statistically significant decrease of a and b waves amplitudes of ERG was observed in p27(-/-) mice when compared to those of the other mice. BrdU and nestin positive cells were present at the outer nuclear layer with no difference between p27(-/-) and wild type mice after MNU injection. CONCLUSION p27(-/-) mice showed thicker retina and less retinal function than those of other mice. The MNU-induced retinal degeneration in p27(-/-) mice closely resembled the reaction of the other mice with no retinal regeneration observed in our experimental condition.
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Rocha-Sanchez SM, Scheetz LR, Contreras M, Weston MD, Korte M, McGee J, Walsh EJ. Mature mice lacking Rbl2/p130 gene have supernumerary inner ear hair cells and supporting cells. J Neurosci 2011; 31:8883-93. [PMID: 21677172 PMCID: PMC3132102 DOI: 10.1523/jneurosci.5821-10.2011] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2010] [Revised: 04/14/2011] [Accepted: 04/20/2011] [Indexed: 11/21/2022] Open
Abstract
Adult mammalian auditory hair cells (HCs) and their associated supporting cells (SCs) do not proliferate, and HC death leads to irreversible neurosensory hearing loss and balance impairment. In nonmammalian vertebrates, loss of HCs induces mitotic proliferation of adjacent nonsensory SCs and/or direct SC transdifferentiation to generate replacement cells. This results in the structural and functional recovery of the nonmammalian sensory systems. Potential replacement of mammalian auditory HCs, either by transplanting cells or by transforming existing cells through molecular therapy, has long been proposed. However, HC replacement strategies with clear therapeutic potential remain elusive. The retinoblastoma (pRB) family of cell cycle regulators, Rb1, Rbl1 (p107), and Rbl2 (p130), regulate the G(1)- to S-phase transition in proliferating cells. In the inner ear, the biochemical and molecular pathways involving pRBs, particularly p107 and p130, are relatively unexplored and their therapeutic suitability is yet to be determined. In this study, we analyzed the cochleae of adult p130 knock-out (p130(-/-)) mice and showed that lack of the p130 gene results in extra rows of HCs and SCs in the more apical regions of the cochlea. No evidence of transdifferentiation of these supernumerary SCs into HCs was observed in the p130(-/-) mouse. Nevertheless, unscheduled proliferation of SCs in the adult p130(-/-) cochlea coupled to downregulation of bona fide cell cycle inhibitors provides a mechanistic basis for the role of p130 as a regulator of SC and HC mitotic quiescence in the more apical regions of the cochlea. Interestingly, p130(-/-) mice exhibited nearly normal peripheral auditory sensitivity.
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MESH Headings
- Acoustic Stimulation
- Age Factors
- Animals
- Animals, Newborn
- Cell Proliferation
- Ear, Inner/cytology
- Ear, Inner/embryology
- Embryo, Mammalian
- Evoked Potentials, Auditory, Brain Stem/genetics
- Female
- Gene Expression Regulation, Developmental/genetics
- Hair Cells, Auditory, Inner/physiology
- Immunoprecipitation
- Labyrinth Supporting Cells/physiology
- Male
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Myosin VIIa
- Myosins/metabolism
- Otoacoustic Emissions, Spontaneous/genetics
- Receptors, Nerve Growth Factor/metabolism
- Retinoblastoma Protein/deficiency
- SOXB1 Transcription Factors/metabolism
- Tubulin/metabolism
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Affiliation(s)
- Sonia M Rocha-Sanchez
- Department of Oral Biology, Creighton University School of Dentistry, Omaha, Nebraska 68178, USA.
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19
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An RNA interference-based screen of transcription factor genes identifies pathways necessary for sensory regeneration in the avian inner ear. J Neurosci 2011; 31:4535-43. [PMID: 21430154 DOI: 10.1523/jneurosci.5456-10.2011] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Sensory hair cells of the inner ear are the mechanoelectric transducers of sound and head motion. In mammals, damage to sensory hair cells leads to hearing or balance deficits. Nonmammalian vertebrates such as birds can regenerate hair cells after injury. In a previous study, we characterized transcription factor gene expression during chicken hair cell regeneration. In those studies, a laser microbeam or ototoxic antibiotics were used to damage the sensory epithelia (SE). The current study focused on 27 genes that were upregulated in regenerating SEs compared to untreated SEs in the previous study. Those genes were knocked down by siRNA to determine their requirement for supporting cell proliferation and to measure resulting changes in the larger network of gene expression. We identified 11 genes necessary for proliferation and also identified novel interactive relationships between many of them. Defined components of the WNT, PAX, and AP1 pathways were shown to be required for supporting cell proliferation. These pathways intersect on WNT4, which is also necessary for proliferation. Among the required genes, the CCAAT enhancer binding protein, CEBPG, acts downstream of Jun Kinase and JUND in the AP1 pathway. The WNT coreceptor LRP5 acts downstream of CEBPG, as does the transcription factor BTAF1. Both of these genes are also necessary for supporting cell proliferation. This is the first large-scale screen of its type and suggests an important intersection between the AP1 pathway, the PAX pathway, and WNT signaling in the regulation of supporting cell proliferation during inner ear hair cell regeneration.
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20
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Oesterle EC, Chien WM, Campbell S, Nellimarla P, Fero ML. p27(Kip1) is required to maintain proliferative quiescence in the adult cochlea and pituitary. Cell Cycle 2011; 10:1237-48. [PMID: 21403466 DOI: 10.4161/cc.10.8.15301] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Cell cycle inhibitors, such as the cyclin-dependent kinase (Cdk) inhibitor proteins and retinoblastoma (Rb) family members, control exit from the cell cycle during the development of a variety of terminally differentiated tissues. It is unclear whether sustained expression of these proteins is required to prevent cell cycle re-entry in quiescent and terminally differentiated cells. The organ of Corti (cochlear sensory epithelium) and pars intermedia (intermediate lobe of the pituitary) are two tissues that share the characteristic of ongoing cell division in mice lacking either the p27(Kip1) Cdk inhibitor, Ink4 proteins, or Rb. Here, we use tamoxifen-inducible mouse models to delete p27(Kip1) in postnatal animals and show this is sufficient to induce proliferation in both the organ of Corti and pars intermedia. Thus, these tissues remain sensitive to the presence of p27(Kip1) even after their developmental exit from the cell cycle. The neonatal cochlea displayed heightened sensitivity to changes in p27(Kip1) expression, with a proliferative response higher than that of constitutive null mice. In adults, the proliferative response was reduced but was accompanied by increased cell survival. In contrast, re-establishment of normal p27(Kip1) expression in animals with established pituitary tumors, in an inducible "knock-on" model, led to cessation of pituitary tumor growth, indicating the cells had maintained their susceptibility to p27-mediated growth suppression. Although restoration of p27(Kip1) did not induce apoptosis, it did lead to resolution of pathological features and normalization of gene expression. Our data underscore the importance of p27(Kip1) expression in the maintenance of cellular quiescence and terminal differentiation.
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Affiliation(s)
- Elizabeth C Oesterle
- Virginia Merrill Bloedel Hearing Research Center, Department of Otolaryngology-Head and Neck Surgery, University of Washington, Seattle, WA, USA.
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21
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Liu Z, Owen T, Zhang L, Zuo J. Dynamic expression pattern of Sonic hedgehog in developing cochlear spiral ganglion neurons. Dev Dyn 2010; 239:1674-83. [PMID: 20503364 DOI: 10.1002/dvdy.22302] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Sonic hedgehog (Shh) signaling plays important roles in the formation of the auditory epithelium. However, little is known about the detailed expression pattern of Shh and the cell sources from which Shh is secreted. By analyzing Shh(CreEGFP/+) mice, we found that Shh was first expressed in all cochlear spiral ganglion neurons by embryonic day 13.5, after which its expression gradually decreased from base to apex. By postnatal day 0, it was not detected in any spiral ganglion neurons. Genetic cell fate mapping results also confirmed that Shh was exclusively expressed in all spiral ganglion neurons and not in surrounding glia cells. The basal-to-apical wave of Shh decline strongly resembles that of hair cell differentiation, supporting the idea that Shh signaling inhibits hair cell differentiation. Furthermore, this Shh(CreEGFP/+) mouse is a useful Cre line in which to delete floxed genes specifically in spiral ganglion neurons of the developing cochlea.
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Affiliation(s)
- Zhiyong Liu
- Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA
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22
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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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23
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In vivo proliferation of postmitotic cochlear supporting cells by acute ablation of the retinoblastoma protein in neonatal mice. J Neurosci 2010; 30:5927-36. [PMID: 20427652 DOI: 10.1523/jneurosci.5989-09.2010] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Cochlear hair cells (HCs) are mechanosensory receptors that transduce sound into electrical signals. HC damage in nonmammalian vertebrates induces surrounding supporting cells (SCs) to divide, transdifferentiate and replace lost HCs; however, such spontaneous HC regeneration does not occur in the mammalian cochlea. Here, we acutely ablate the retinoblastoma protein (Rb), a crucial cell cycle regulator, in two subtypes of postmitotic SCs (pillar and Deiters' cells) using an inducible Cre line, Prox1-CreER(T2). Inactivation of Rb in these SCs results in cell cycle reentry of both pillar and Deiters' cells, and completion of cell division with an increase in cell number of pillar cells. Interestingly, nuclei of Rb(-/-) mitotic pillar and Deiters' cells migrate toward the HC layer and divide near the epithelial surface in a manner similar to the SCs in the regenerating avian auditory epithelium. In contrast to postmitotic Rb(-/-) HCs which abort cell division, postmitotic Rb(-/-) pillar cells can proliferate, maintain their SC fate and survive for more than a week. However, no newly formed HCs are detected and SC death followed by HC loss occurs. Our studies accomplish a crucial step toward functional HC regeneration in the mammalian cochlea in vivo, demonstrating the critical role of Rb in maintaining quiescence of postmitotic pillar and Deiters' cells and highlighting the heterogeneity between these two cell types. Therefore, the combination of transient Rb inactivation and further manipulation of transcription factors (i.e., Atoh1 activation) in SCs may represent an effective therapeutic avenue for HC regeneration in the mammalian cochlea.
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24
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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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25
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Chen J, Wang F, Gao X, Zha D, Xue T, Cheng X, Zhong C, Han Y, Qiu J. Decreased level of cyclin A2 in rat cochlea development and cochlear stem cell differentiation. Neurosci Lett 2009; 453:166-9. [DOI: 10.1016/j.neulet.2009.02.019] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2008] [Revised: 02/09/2009] [Accepted: 02/09/2009] [Indexed: 11/27/2022]
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26
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Liu Z, Zuo J. Cell cycle regulation in hair cell development and regeneration in the mouse cochlea. Cell Cycle 2008; 7:2129-33. [PMID: 18635955 DOI: 10.4161/cc.7.14.6423] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Cell cycle inhibitors play important roles in the development of mammalian cochleae. Loss of function of those factors in mice at various developmental stages results in distinct phenotypes characterized by overproduction or loss of cochlear sensory cells. Our recent study showed that acute deletion of the retinoblastoma protein (Rb) induces rapid cell cycle reentry and subsequent loss of postnatal cochlear hair cells in mice. Clearly, these regulators play multiple roles in cell cycle exit and differentiation of hair cell and supporting cell progenitors. They are also crucial in maintenance of postmitotic states and survival of differentiated hair cells and supporting cells. In mammals, lost hair cells cannot be spontaneously replaced, leading to permanent deafness. However, lower vertebrates such as birds and fish can naturally regenerate damaged hair cells from the underlying supporting cells through proliferation and transdifferentiation. Thus, manipulating cell cycle inhibitors in mammalian cochleae could provide a new avenue to restore hearing in deaf people caused by a variety of genetic mutations and environmental insults.
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Affiliation(s)
- Zhiyong Liu
- Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA
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27
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Minoda R, Izumikawa M, Kawamoto K, Zhang H, Raphael Y. Manipulating cell cycle regulation in the mature cochlea. Hear Res 2007; 232:44-51. [PMID: 17658230 PMCID: PMC2048570 DOI: 10.1016/j.heares.2007.06.005] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/28/2006] [Revised: 06/06/2007] [Accepted: 06/08/2007] [Indexed: 11/19/2022]
Abstract
Sensorineural hearing loss, which is often caused by degeneration of hair cells in the auditory epithelium, is permanent because lost hair cells are not replaced. Several conceptual approaches can be used to place new hair cells in the auditory epithelium. One possibility is to enhance proliferation of non-sensory cells that remain in the deaf ear and induce transdifferentiation of some of these cells into the hair cell phenotype. Several genes, including p27(Kip1), have been shown to regulate proliferation and differentiation in the developing auditory epithelium. The role of p27(Kip1) in the mature ear is not well characterized. We now show that p27(Kip1) is present in the nuclei of non-sensory cells of the mature auditory epithelium. We determined that forced expression of Skp2 using a recombinant adenovirus vector, resulted in presence of BrdU-positive cells in the auditory epithelium. When SKP2 over-expression was combined with forced expression of Atoh1, ectopic hair cells were found in the auditory epithelium in greater numbers than were seen with Atoh1 alone. Skp2 over-expression alone did not result in ectopic hair cells. These findings suggest that the p27(Kip1) protein remains in the mature auditory epithelium and therefore p27(Kip1) can serve as a target for gene manipulation. The data also suggest that induced proliferation, by itself, does not generate new hair cells in the cochlea.
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Affiliation(s)
- Ryosei Minoda
- Kresge Hearing Research Institute, The University of Michigan, MSRB 3, Rm. 9303, 1150 W. Medical Center Dr., Ann Arbor, MI 48109-0648, USA
- Department of Otolaryngology- Head and Neck Surgery, Kumamoto University School of Medicine, 1-1-1 Honjo Kumamoto 860-8556, Japan
| | - Masahiko Izumikawa
- Kresge Hearing Research Institute, The University of Michigan, MSRB 3, Rm. 9303, 1150 W. Medical Center Dr., Ann Arbor, MI 48109-0648, USA
- Department of Otolaryngology- Head and Neck Surgery, Kansai Medical University, 10-15 Fumizono-cho, Moriguchi, Osaka 570-8506, Japan
| | - Kohei Kawamoto
- Kresge Hearing Research Institute, The University of Michigan, MSRB 3, Rm. 9303, 1150 W. Medical Center Dr., Ann Arbor, MI 48109-0648, USA
- Department of Otolaryngology- Head and Neck Surgery, Kansai Medical University, 10-15 Fumizono-cho, Moriguchi, Osaka 570-8506, Japan
| | - Hui Zhang
- Department of Genetics, Yale University School of Medicine, 333 Cedar Street, P.O. Box 208005, New Haven, CT 06520-8005, USA
| | - Yehoash Raphael
- Kresge Hearing Research Institute, The University of Michigan, MSRB 3, Rm. 9303, 1150 W. Medical Center Dr., Ann Arbor, MI 48109-0648, USA
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28
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Donadieu E, Hamdi W, Deveze A, Lucciano M, Lavieille JP, Magnan J, Riva C. Improved cryosections and specific immunohistochemical methods for detecting hypoxia in mouse and rat cochleae. Acta Histochem 2007; 109:177-84. [PMID: 17349680 DOI: 10.1016/j.acthis.2007.01.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2006] [Revised: 01/29/2007] [Accepted: 01/29/2007] [Indexed: 10/23/2022]
Abstract
The present study was undertaken to develop an improved cryoembedding method for analysis of mice and rat cochleae, which permits high-quality cryosections and preserves overall structure and cellular resolution as shown by hematoxylin/eosin staining. The preservation of morphology and antigenicity is mandatory to achieve optimal results. A total of 20 male cd/1 mice and 14 male Sprague-Dawley rats were used in experiments for optimization of preservation, fixative, decalcification, embedding and cryosectioning of cochleae from adult and aged rodents. In addition, a novel immunohistochemical procedure (using Hydroxyprobe-1 kit) was developed for detecting regions of hypoxia in mice and rat cochlea. This method employs a primary fluorescent-conjugated monoclonal antibody directed against pimonidazole protein adducts that are created in hypoxic tissues. Subsequent studies of hypoxia inducible factor-1alpha (HIF-1alpha) by immunofluorescence in the cochlea of these animals were performed in order to confirm that immunochemical detection of pimonidazole protein is representative of a hypoxic environment. We conclude that the present method results in high-quality cryosections of cochlear tissues presenting good anatomical and histological preservation. Furthermore, our optimized procedures provide novel tools for the investigation of neuro-sensory-epithelium in physio-pathological situations associated with hypoxia and/or ischemia, such as inner ear development, plasticity, regeneration and senescence.
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Affiliation(s)
- Emilie Donadieu
- Laboratoire d'Otologie Neuro-otologie et Micro-Endoscopie, IFR Jean Roche, Faculté de Médecine Nord, Université de la Méditerranée, Bd Pierre Dramard, 13916 Marseille cedex 20, France
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29
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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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