Establishment of a cochlear lymphatic vascular network and immune surveillance system following cochlear implantation
Hearing loss is a highly prevalent sensory abnormality often addressed with cochlear implants (CI) that provide auditory rehabilitation for deaf patients. However, a universal inflammatory foreign body response (FBR) to the implanted materials negatively impacts CI outcomes. The mechanistic basis for immune cell infiltration and propagation of the FBR directed against CIs is not defined. Using mouse CI models and quantitative, highly tractable reporters for lymphatics, blood vessels, and immune cells, we identify inner ear lymphatic vessels and changes to the immune surveillance system following cochlear implantation. Histopathological analysis of implanted temporal bones from human subjects shows that both blood vessels and lymphatics are evident within the scala tympani of the implanted cochlea. Our data reveal a rich lymphatic vascular network in the inner ear, closely associated with the perilymphatic and endolymphatic spaces. Lymphatics proliferate within the perilymphatic space of the implanted cochleae and appear to traffic immune cells. Together, our data provide direct evidence that concurrent proliferation of blood vessels and recruitment of blood-borne immune cells comprise an 'immune surveillance system' in the implanted cochleae that promotes the FBR. Our findings also highlight potential opportunities to limit adverse FBR outcomes following cochlear implantation.