title: Cochlear gene transfer mediated by adeno-associated virus: Comparison of two surgical approaches.
abstract: OBJECTIVE
  Gene therapy offers the possibility of delivering corrective genetic materials to the cochlea, potentially improving hearing. In animals, the most commonly used surgical methods for viral gene therapy delivery to the cochlea are the round window and the cochleostomy approaches. However, the patterns of viral infection and the effects on hearing have not been directly compared between these two approaches. In this study, we compare the patterns of cochlear infection and effects on hearing between these two surgical approaches using adeno-associated virus serotype 2/8 (AAV8) as the gene delivery vehicle.
  
  
  METHODS
  Animal study and basic science research.
  
  
  METHODS
  One- to two-month-old CBA/J mice were used in this study. AAV8-green fluorescent protein (GFP) was delivered to the cochlea by either the round window or the cochleostomy approach (described below). Auditory brainstem response was used to examine hearing thresholds before and after surgery. Animals were examined at 1, 2, 3, and 4 weeks after surgery for the patterns of cochlear infection and hearing loss.
  
  
  RESULTS
  Cochlear gene transfer was successful through both surgical approaches. In both approaches, AAV8-GFP mostly infected the inner hair cells. There was occasional low-level infection of the outer hair cells and supporting cells. The two surgical approaches resulted in comparable viral infection efficiencies. The round window approach resulted in less surgical trauma, as indicated by hearing loss, than the cochleostomy approach.
  
  
  CONCLUSIONS
  Adeno-associated virus-mediated gene transfer to the cochlea can be accomplished using either the round window or the cochleostomy surgical approach. The round window approach resulted in less hearing loss compared to the cochleostomy approach.
  
  
  METHODS
  NA.
authors.affiliation: National Institute on Deafness and Other Communication Disorders (w.w.c., d.s.m., s.r., t.s.f., l.l.c), National Institutes of Health, Bethesda, Maryland, U.S.A.|Department of Otolaryngology-Head and Neck Surgery, Johns Hopkins School of Medicine, Baltimore, Maryland, U.S.A.
authors.forename: Wade W
authors.initials: WW
authors.lastname: Chien
authors.affiliation: National Institute on Deafness and Other Communication Disorders (w.w.c., d.s.m., s.r., t.s.f., l.l.c), National Institutes of Health, Bethesda, Maryland, U.S.A.
authors.forename: Devin S
authors.initials: DS
authors.lastname: McDougald
authors.affiliation: National Institute on Deafness and Other Communication Disorders (w.w.c., d.s.m., s.r., t.s.f., l.l.c), National Institutes of Health, Bethesda, Maryland, U.S.A.
authors.forename: Soumen
authors.initials: S
authors.lastname: Roy
authors.affiliation: National Institute on Deafness and Other Communication Disorders (w.w.c., d.s.m., s.r., t.s.f., l.l.c), National Institutes of Health, Bethesda, Maryland, U.S.A.
authors.forename: Tracy S
authors.initials: TS
authors.lastname: Fitzgerald
authors.affiliation: National Institute on Deafness and Other Communication Disorders (w.w.c., d.s.m., s.r., t.s.f., l.l.c), National Institutes of Health, Bethesda, Maryland, U.S.A.
authors.forename: Lisa L
authors.initials: LL
authors.lastname: Cunningham
mesh_terms: D000818:Animals; D003051:Cochlea / Q000601:surgery; D000229:Dependovirus / Q000235:genetics*; D005260:Female; D018014:Gene Transfer Techniques; D015316:Genetic Therapy / Q000379:methods*; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006199:Hair Cells, Auditory, Inner / Q000821:virology; D034381:Hearing Loss / Q000821:virology; D049408:Luminescent Agents; D008297:Male; D008808:Mice, Inbred CBA; D013506:Otologic Surgical Procedures / Q000379:methods*; D010322:Parvoviridae Infections / Q000378:metabolism; D012405:Round Window, Ear / Q000601:surgery
chemical_list: D049408:Luminescent Agents; D049452:Green Fluorescent Proteins
keywords: Gene therapy; adeno-associated virus; cochleostomy; hearing loss; round window