The role of strial macrophages in the maintenance of the blood–labyrinth barrier

Macrophages in the cochlear stria vascularis (SV) are crucial for maintaining the integrity of the blood–labyrinth barrier (BLB) and supporting auditory function. Using a macrophage depletion mouse model during auditory development, we conducted a comprehensive series of auditory assessments to elucidate the role of strial macrophages in maintaining the BLB. These assessments included auditory brainstem response tests, flow cytometry, immunofluorescence staining, immunoblotting, and permeability assays on postnatal day 35. We found that macrophage depletion in the SV led to increased BLB permeability and high-frequency hearing loss, which were accompanied by decreased vessel density, a reduced vessel branching index, and loss of tight junctions. These findings highlight the essential role of strial macrophages in the formation of a fully functional BLB, providing new insights into sensorineural hearing loss, particularly in the high-frequency compartment.