Inner ear supporting cells are organized tissue-resident macrophages arranged like cobblestones.

Sensorineural hearing loss (SHL) is a relatively common disease, and studies have suggested viral infection as a major cause. In the inner ear, the blood-labyrinthine barrier prevents access of the peripheral immune system; therefore, the immune system remains poorly understood. Here we found that cochlear accessory supporting cells (SCs), which are anchored by tight junctions, are organized tissue-resident macrophages. Virus-infected supporting cells change into activated macrophages and protect audiosensory receptor hair cells (HCs) against virus infection by producing interferon (IFN)-/. Moreover, we also observed bacterial phagocytosis by SCs. However, tumour necrosis factor-related apoptosis-inducing ligand (Trail), produced by virus-infected SCs, induced sensory hair loss and HC death by necroptosis. Notably, corticosteroid, the only effective drug for SHL, inhibited the virus-induced macrophage change of SCs. These results revealed an inner ear immune system, and suggest a possible mechanism for virus-induced SHL.

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