Work

Tissue-resident and recruited mononuclear phagocyte organization in the cochlea under homeostasis and implant-induced inflammation

Year: 2026

Type: article

Abstract: Background: The cochlea contains a diverse population of immune cells that contribute to tissue homeostasis and to responses to injury. Among these, mononuclear phagocytes including tissue-resident macrophages, dendritic cells, and microglia-like cells play central roles in immune surveillance and inflammation. Cochlear implantation induces a robust foreign body response, and here we sought to map the spatial distribution of mononuclear phagocytes across distinct cochlear compartments in healthy cochleae and following implantation. Materials and methods: We used two reporter mice in this study: C57BL/6-Tmem119em2Gfng/J (TMEM119+/GFP as reporter for microglia), B6. FVB-1700016L21RikTg (Itgax-DTR/EGFP)57Lan/J (CD11c+/GFP as reporter for dendritic cells). To define the spatial organization of different types of mononuclear phagocytes in normal cochleae and after implantation, 30-μm mid-modiolar cochlear sections from these reporter mice were imaged using a confocal microscope. Immunolabeling with cell-specific and activation markers was used to further characterize the cellular distributions and responses. Results: We identify heterogeneous distribution of mononuclear phagocytes throughout the cochlea. CD11c-positive dendritic cells display a more restricted baseline distribution, residing primarily in Rosenthal's canal and the spiral ligament; they selectively accumulate at the implant-tissue interface in the scala tympani after implantation and upregulate major histocompatibility complex class II expression, consistent with antigen-presenting phenotypes. In addition, expression of microglia-associated markers, including TMEM119 and P2Y12, identifies a microglia-like population within specific cochlear sub-regions that persists following implantation. Conclusion: Together, these findings reveal an immune landscape in the cochlea under both healthy and implant-associated inflammatory conditions. CD11c-positive dendritic cells appear to play a central role in the inflammatory response to cochlear implants, becoming activated and localizing to the interface with the biomaterial surface.

Source: Frontiers in Cellular Neuroscience

DOI: 10.3389/fncel.2026.1895870