Inner ear protein as a biomarker in circulation?

Serum biomarkers detect the earliest events in disease, monitor management, and provide insight into disease pathogenesis. At this time, there are no biomarkers available for otologic disorders. Otolin-1 is a scaffolding protein exclusively expressed in otoconia and cells of the vestibule and the cochlea; therefore, it may be a biomarker candidate for assessing the health of the inner ear. As a proof of concept, we used serum samples from controls without otologic history and subjects with a history of benign paroxysmal positional vertigo (BPPV), performed enzyme-linked immunosorbent assay for otolin-1, and measured the optical density of the substrate. Otolin-1 was detectable and quantifiable in all subjects, indicating that this inner ear protein crosses the blood-labyrinthine barrier. Furthermore, subjects with BPPV had significantly higher levels, with about one-third being above the control range. This promising preliminary result suggests that inner ear-specific proteins have the potential to serve as biomarkers for otologic disease processes.