Preprint
Contribution of macrophages to intracochlear tissue remodeling responses following cochlear implantation and neural survival
Research square
06/26/2023
DOI: 10.21203/rs.3.rs-3065630/v1
PMCID: PMC10350110
PMID: 37461619
Abstract
INTRODUCTIONCochlear implants (CIs) restore hearing to deafened patients. The foreign body response (FBR) following cochlear implantation (post-CI) comprises an infiltration of macrophages, other immune and non-immune cells, and fibrosis into the scala tympani; a space that is normally devoid of cells. This FBR is associated with negative effects on CI outcomes including increased electrode impedances and loss of residual acoustic hearing. This study investigates the extent to which macrophage depletion by an orally administered CSF-1R specific kinase (c-FMS) inhibitor, PLX-5622, modulates the tissue response to CI and neural health. MATERIALS AND METHODS10-12-week-old CX3CR1+/GFP Thy1+/YFP mice on C57Bl6 background with normal hearing were fed chow containing 1200 mg/kg PLX5622 or control chow for the duration of the study. 7-days after starting the diet, 3-channel cochlear implants were implanted ear via the round window. Serial impedance and neural response telemetry (NRT) measurements were acquired throughout the study. Electric stimulation began 7 days post-CI until 28- days post-CI for 5 hrs/day, 5 days/week, with programming guided by NRT and behavioral responses. Cochleae harvested at 10-, 28- or 56-days post-CI were cryosectioned and labeled with antibody against α-smooth muscle actin (α-SMA) to identify myofibroblasts and quantify the fibrotic response. Using IMARIS image analysis software, the outlines of scala tympani, Rosenthal canal, modiolus and lateral wall for each turn were traced manually to measure region volume. Density of nuclei, CX3CR1+ macrophages, Thy1+ spiral ganglion neuron (SGN) numbers and ratio of volume of α-SMA+ space/volume of scala tympani were calculated. RESULTSCochlear implantation in control diet subjects caused infiltration of cells, including macrophages, into the cochlea: this response was initially diffuse throughout the cochlea and later localized to the scala tympani of the basal turn by 56-days post-CI. Fibrosis was evident in the scala tympani adjacent to the electrode array. Mice fed PLX5622 chow showed reduced macrophage infiltration throughout the implanted cochleae across all timepoints. However, scala tympani fibrosis was not reduced relative to control diet subjects. Further, mice treated with PLX5622 showed increased electrode impedances compared to controls. Finally, treatment with PLX5622 decreased SGN survival in implanted and contralateral cochleae. DISCUSSIONThe data suggest that macrophages play an important role in modulating the intracochlear tissue response following CI and neural survival.
Details
- Title: Subtitle
- Contribution of macrophages to intracochlear tissue remodeling responses following cochlear implantation and neural survival
- Creators
- Muhammad Taifur Rahman - University of IowaBrain J Mostaert - University of IowaBryce Hunger - University of IowaUtsow Saha - University of IowaAlexander D Claussen - University of IowaIbrahim Razu - University of IowaNasrin Farjana - University of IowaNashwaan Ali Khan - University of IowaSarah Coleman - University of IowaJackob Oleson - University of IowaJonathon Kirk - Cochlear (Australia)Hirose Keiko - Washington University in St. LouisMarlan R Hansen - University of Iowa
- Resource Type
- Preprint
- Publication Details
- Research square
- DOI
- 10.21203/rs.3.rs-3065630/v1
- PMID
- 37461619
- PMCID
- PMC10350110
- Language
- English
- Date posted
- 06/26/2023
- Academic Unit
- Molecular Physiology and Biophysics; Biostatistics; Neurosurgery; Otolaryngology
- Record Identifier
- 9984445624202771
Metrics
23 Record Views