Cochlear resident tissue macrophages in normal cochlear development and the response to CMV infection - PROJECT SUMMARY / ABSTRACT Congenital cytomegalovirus (CMV) infection can lead to sensorineural hearing loss (SNHL) long after resolution of acute infection, implicating lasting alterations to tissue immunity, but the underlying pathogenic mechanisms remain poorly understood. The long-term goal of this project is to define the mechanisms by which congenital infection impinges on cochlear immune development to drive SNHL. The overall objectives in this application are (1) to determine the contribution of the fetal host immune cells, specifically resident tissue macrophages (RTMs) to normal cochlear development and (2) to determine how CMV shapes tissue immunity during perinatal development to drive cochlear dysfunction. The central hypothesis is that RTMs are crucial to normal cochlear development and that the response of fetal-derived RTMs to CMV infection is a critical mediator of cochlear damage that drives SNHL. Our preliminary data indicate that fetal macrophages of distinct ontogenetic origin seed the cochlea in a specific spatiotemporal pattern. Temporal blockade of CSF1R, a regulator of fetal macrophage development, causes cochlear impairment and SNHL. Together, these findings suggest that fetal- derived RTMs are critical regulators of normal cochlear development and tissue homeostasis, but the precise mechanisms have not been delineated. The central hypothesis will be tested by pursuing three specific aims: 1) Define the contribution of fetal RTMs to normal cochlear development; 2) Determine the effect of acute CMV infection on RTM development; and 3) Determine the immune drivers of progressive SNHL following acute CMV infection. In the first aim, we will employ fate-mapping and deletion of specific ontogenetic macrophage subsets to define the spatiotemporal seeding and function of distinct waves of RTMs in normal cochlear development. In Aim 2, we will investigate the effect of acute CMV infection in the perinatal period on seeding, transcriptional, and functional regulation of RTM development in the cochlea. In Aim 3, we will examine how replacement of fetal RTMs with adult BM-derived RTMs reshapes cochlear immunity and cochlear function, both under homeostasis and in response to acute infection. We will combine fate-mapping, transcriptomic analysis and genetic deletion models to define how replacement of fetal RTMs with BM-derived RTMs contributes to cochlear inflammation, immune cell infiltration, and hearing function. The research proposed in this application is innovative because it examines the origins of CMV-associated SNHL and cochlear dysfunction from the perspective of immune ontogeny and because it integrates state-of-the-art fate-mapping and deletion models with single-cell transcriptomics, advanced microscopy, and specialized hearing tests to perform highly detailed mechanistic studies over the course of CMV pathogenesis and associated SNHL. The proposed research is significant because it will contribute fundamental knowledge about the developing auditory system and provide strong scientific justification to examine RTMs as a potential novel therapeutic target for SNHL treatment.
