An anatomical and day-night atlas links cochlear immunity to adjacent bone marrow

In mouse cochlea and adjacent temporal-bone marrow, neutrophil programs show daily, CXCR4-linked rhythms and a shared night heat-shock response that noise attenuates.

• Why it matters: The cochlea’s neighboring marrow may shape cochlear immune protection and daily physiology, but how this interface contributes to immune timing is unclear.
• What they did: The study profiled 160,643 cells from mouse cochlea and adjacent temporal-bone marrow at six times of day, mapped vascular connections by 3D confocal imaging, and localized neutrophils at the interface. Parabiosis and independent flow cytometry assessed local marrow contributions and daily immune composition changes, including CXCR4.
• The result: Neutrophils were found in healthy cochlear fluids, parabiosis supported local marrow contribution to cochlear immunity, and cochlear neutrophil programs aligned with circulating neutrophils while opposing marrow programs. A shared night-associated heat-shock programme was attenuated after noise in an independent cohort, enabling tests of local marrow supply and immune rhythm origins.

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