|Beitragstitel||Beneficial or deleterious roles of macrophages/microglia in endolymphatic sac pathologies associated with Meniere’s disease?|
Background: The inner ear harbors a vast population of macrophages/microglia (M/M). The roles of those M/M in normal organ homeostasis, as well as in different pathological conditions of the cochlea and the vestibular system remain unknown.
Here, we investigated whether M/M in the endolymphatic sac (ES) help to maintain a healthy ES epithelium, and whether disruption of M/M-dependent tissue homeostasis could lead to ES degeneration – a hallmark inner ear pathology in Meniere’s disease.
Material and Methods: (i) Tissue sections of the normal mouse and human ES were immunolabeled using M/M-specific antibodies against Iba1 and TMEM119 to investigate the M/M distribution in the ES region. (ii) In vitro cultured mouse ES specimens were manually damaged to investigate tissue repair functions of M/M, using immunohistochemistry. (iii) In tissue sections from MD patients with degenerative ES pathology, the M/M population was quantified using immunohistochemistry.
Results: (i) The normal mouse and human ES is surrounded by a dense M/M population interacting with the ES epithelium. (ii) ES epithelial damage activates local M/M, which then migrate and engage in repairing the damaged epithelium. (iii) In MD, ES degeneration is associated with a loss of the local M/M population.
Conclusion: M/M in the inner ear help to maintain a healthy ES epithelium. In MD, absence/loss of M/M may be causally linked to ES epithelial degeneration by (i) M/M gaining deleterious functions (e.g. inflammatory tissue damage), or by (ii) loss of beneficial, homeostatic functions (e.g. inactivity or death of M/M). Future studies will further elucidate the role of inner ear immune cell-pathologies in MD.