Evaluation of the Efficacy of Dexamethasone-Eluting Electrode Array on the Post-Implant Cochlear Fibrotic Reaction by Three-Dimensional Immunofluorescence Analysis in Mongolian Gerbil Cochlea

Abstract

Cochlear implant is the method of choice for the rehabilitation of severe to profound sensorineural hearing loss. The study of the tissue response to cochlear implantation and the prevention of post-cochlear-implant damages are areas of interest in hearing protection research. The objective was to assess the efficacy of dexamethasone-eluting electrode array on endo canal fibrosis formation by three-dimensional immunofluorescence analysis in implanted Mongolian gerbil cochlea. Two trials were conducted after surgery using Mongolian gerbil implanted with dexamethasone-eluting or non-eluting intracochlear electrode arrays. The animals were then euthanised 10 weeks after implantation. The cochleae were prepared (electrode array in place) according to a 29-day protocol with immunofluorescent labelling and tissue clearing. The acquisition was carried out using light-sheet microscopy. Imaris software was then used for three-dimensional analysis of the cochleae and quantification of the fibrotic volume. The analysis of 12 cochleae showed a significantly different mean volume of fibrosis (2.16 × 108 μm3 ± 0.15 in the dexamethasone eluting group versus 3.17 × 108 μm3 ± 0.54 in the non-eluting group) (p = 0.004). The cochlear implant used as a corticosteroid delivery system appears to be an encouraging device for the protection of the inner ear against fibrosis induced by implantation. Three-dimensional analysis of the cochlea by light-sheet microscopy was suitable for studying post-implantation tissue damage.

Outcomes following cochlear implantation with eluting electrodes: A systematic review

“…Seventeen studies 3,5,10,22,27–39 used animal models. These studies were published between 2008 and 2021.…”

Model-based prediction of optogenetic sound encoding in the human cochlea by future optical cochlear implants

“…For all these aspects, advancements in cochlear implant design and surgical techniques will greatly improve the efficiency of optical stimulation. For example, studies involving release of corticosteroids in the cochlea have shown promising results towards decreasing formation of scar tissue [57] , [58] , [59] . Perimodiolar (or “modiolus-hugging”) implants, which are designed to lie in closer proximity to the SGNs, provide more reliable stimulation with less spectral spread [60] , [61] .…”

Cochlear implant material effects on inflammatory cell function and foreign body response

“…Another strategy to mitigate the cochlear tissue response to implanted electrode arrays is to delivery pharmaceuticals that modulate cellular responses. For example, electrode arrays that elute dexamethasone are currently under development in an effort to limit intracochlear tissue fibrosis (Farhadi et al, 2013;Toulemonde et al, 2021). Further studies are needed to explore strategies to limit the FBR to implanted biomaterials and improve hearing outcomes for CI recipients.…”