Vestibular Damage and Repair in Chronic Ototoxicity: Cellular Stages, Physiological Deficits and Molecular Mechanisms Erin A. Greguske ADVERTIMENT. La consulta d’aquesta tesi queda condicionada a l’acceptació de les següents condicions d'ús: La difusió d’aquesta tesi per mitjà del servei TDX (www.tdx.cat) i a través del Dipòsit Digital de la UB (diposit.ub.edu) ha estat autoritzada pels titulars dels drets de propietat intelꞏlectual únicament per a usos privats emmarcats en activitats d’investigació i docència. No s’autoritza la seva reproducció amb finalitats de lucre ni la seva difusió i posada a disposició des d’un lloc aliè al servei TDX ni al Dipòsit Digital de la UB. No s’autoritza la presentació del seu contingut en una finestra o marc aliè a TDX o al Dipòsit Digital de la UB (framing). Aquesta reserva de drets afecta tant al resum de presentació de la tesi com als seus continguts. En la utilització o cita de parts de la tesi és obligat indicar el nom de la persona autora. 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Vestibular Damage and Repair in Chronic Ototoxicity: Cellular Stages, Physiological Deficits and Molecular Mechanisms Thesis by Erin A Greguske Vestibular Damage and Repair in Chronic Ototoxicity: Cellular Stages, Physiological Deficits and Molecular Mechanisms Doctoral Thesis presented by Erin A Greguske L’Hospitalet de Llobregat, 2019 Doctoral Program in Biomedicine Vestibular Damage and Repair in Chronic Ototoxicity: Cellular Stages, Physiological Deficits and Molecular Mechanisms Department of Physiological Sciences Faculty of Medicine and Health Sciences, Campus Bellvitge Universitat de Barcelona Doctoral Candidate Thesis Director Erin A Greguske Dr. Jordi Llorens Baucells The work of this Thesis was financed by: - Grant FI-DGR 2015 (9015-355847/2014) “Damage and Repair in the Vestibular Sensory Epithelia during Chronic Ototoxicity and Recovery”, from the Agency for Management of University and Research Grants (AGAUR), Generalitat de Catalunya - Grant FPU14-05426 “Vestibular Damage and Repair in Chronic Ototoxicity: Cellular Stages, Physiological Deficits and Molecular Mechanisms”, from the Ministry of Education, Culture and Sport of Spain - Project BFU2012-31164 “Vestibular Damage and Repair in Chronic Ototoxicity: Cellular Stages, Physiological Deficits and Molecular Mechanisms”, from the Ministry of Economy and Competitiveness of Spain - Project BFU2015-66109-R “Damage and Repair of the Vestibular Synapses during Chronic Ototoxicity”, from the Ministry of Economy and Competitiveness of Spain - Minor Grant “Synaptic Damage in the Vestibular Epithelium in a Chronic Ototoxicity Model”, from the Ménière’s Society in the United Kingdom Acknowledgements Keeping it sweet and simple: Thank you to all my family and loved ones for believing in me every step of the way on this long academic journey. Your support and love were everything in helping me cultivate the passion I have for science and to always finish strong. Thank you to my friends, old and new, for the endless words of encouragement and hype, which kept me happy and sane. Thank you to my colleagues for your teachings that helped me persevere throughout my pursuit of knowledge and a special thanks to Benja and Josep of the CCiTUB and Klaas of the UMIC for all of your help. And thank you Jordi for your endless patience and guidance throughout the years; for believing in my academic strength and helping me achieve this goal. Index 1. Abbreviations………………………………………………………………..1 2. Abstract……………………………………………………………………...7 3. Introduction…………………………………………………………............11 3.1. The Inner Ear…………………………………………………………....13 3.2. The Vertebrate Ear……………………………………………………....14 3.3. The Vestibular System…………………………………………………...14 3.4. The Vestibular Sensory Hair Cells……………………………………….16 3.5. The Vestibular Sensory Afferents………………………………………..17 3.6. Vestibular Sensory Hair Cell Signal Transmission………………………..19 3.7. Vestibular Signaling Pathway to the CNS………………………................21 3.8. The Auditory System……………………………………………………22 3.9. The Organ of Corti, the Sensory Epithelium of the Cochlea…………….23 3.10. The Cochlear Sensory Hair Cells……………………………………...23 3.11. The Cochlear Sensory Afferents……………………………………....25 3.12. The Auditory Efferent Pathway…………………………………….....25 3.13. Cochlear Sensory Hair Cell Signal Transmission………………….…...25 3.14. Auditory Signaling Pathway to the CNS………………………….........26 3.15. Ototoxicity and Aminoglycoside Antibiotics………………………......27 3.16. Animal Studies of Ototoxicity……………………………………........28 3.17. The Introduction of Nitriles for Progressive Ototoxic Studies………..29 4. Objectives…………………………………………………………………..33 5. Methodology……………………………………………………………….37 5.1. Animals………………………………………………………………….39 5.2. Ototoxic IDPN Exposure……………………………………………….39 5.3. Vestibular Dysfunction Ratings (VDRs)…………………………………41 5.4. Auditory Brainstem Response (ABR) Measurements…………………….41 5.5. Tissue Dissection and Epithelia/Ganglia Extraction…………………….42 5.6. Immunofluorescent Studies……………………………………………...42 5.6.1. First Protocol/Study………………………………………………43 5.6.2. Second Protocol/Study……………………………………………43 5.6.3. Third Protocol/Study……………………………………………...44 5.6.4. Fourth Protocol/Study………………………………………….....44 5.6.5. Fifth Protocol/Study……………………………………………....44 5.7. Cochlear Place-Frequency Maps…………………………………………47 5.8. Confocal Microscopy and Image Analysis………………………...............47 5.9. Scanning Electron Microscopy (SEM) Ultrastructural Studies………........49 5.10. Transmission Electron Microscopy (TEM) Ultrastructural Studies…....50 5.11. qRT-PCR Studies……………………………………………................50 5.12. RNA-sequencing (RNAseq)…………………………………................52 5.13. Data Analysis-SPSS………………………………………….................52 6. Results……………………………………………………………….............55 6.1. Preliminary Total RNA Isolation Study………………………………......57 6.1.1. Testing various protocols………………………………………........57 6.1.2. Qiagen proves to be the most consistent, efficient, and effective protocol……………………………………………………...............58 6.2. Characterizing Vestibular Damage…………………………………..........59 6.2.1. Effects of sub-chronic IDPN on 129S1 body weight…………..........59 6.2.2. Effects of sub-chronic IDPN on 129S1 vestibular function………...60 6.2.3. SEM analysis of stereociliary damage and HC loss following sub- chronic IDPN exposure………………………………………..........61 6.2.4. Light Microscopy and TEM analysis of calyceal junction loss, stereociliary fusion, and HC extrusion following sub-chronic IDPN exposure………………………………………………………….....64 6.2.5. Molecular analysis of calyceal junction dismantlement following sub- chronic IDPN exposure…………………………………………….66 6.2.6. mRNA expression of tenascin-c in the vestibular sensory epithelia is altered following sub-chronic IDPN exposure……………………...68 6.2.7. Molecular analysis of synaptic uncoupling and post-synaptic density protein alterations following sub-chronic IDPN exposure………….69 6.2.8. mRNA expression of various synaptic, scaffolding, and signaling proteins in the vestibular sensory epithelia and ganglia are altered following sub-chronic IDPN exposure……………………………..75 6.2.9. Preliminary RNAseq data of the vestibular ganglia and vestibular sensory epithelia demonstrate a depression in signal transmission in the afferent and cell-cell adhesion in the epithelia following sub- chronic IDPN exposure…………………………………………….76 6.2.10. Corroborating RNAseq results with qRT-PCR analyses of selected neurotrophic factors, synaptic, receptor, and kinase proteins and proteins associated with molecule transport…........................................81 6.3. Characterizing Auditory Damage…………………………………............82 6.3.1. Effects of sub-chronic IDPN on 129S2 body weight………….......82 6.3.2. Effects of sub-chronic IDPN on 129S2 vestibular function………83 6.3.3. IDPN exposure strongly affects the hearing of treated mice…........83 6.3.4. IDPN exposure causes a robust loss of OHCs, but IHCs remain