Impact of Systemic versus Intratympanic Dexamethasone Administration on the Perilymph Proteome

Glucocorticoids are the first-line
treatment for sensorineural
hearing loss, but little is known about the mechanism of their protective
effect or the impact of route of administration. The recent development
of hollow microneedles enables safe and reliable sampling of perilymph
for proteomic analysis. Using these microneedles, we investigate the
effect of intratympanic (IT) versus intraperitoneal (IP) dexamethasone
administration on guinea pig perilymph proteome. Guinea pigs were
treated with IT dexamethasone (n = 6), IP dexamethasone
(n = 8), or untreated for control (n = 8) 6 h prior to aspiration. The round window membrane (RWM) was
accessed via a postauricular approach, and hollow microneedles were
used to perforate the RWM and aspirate 1 μL of perilymph. Perilymph
samples were analyzed by liquid chromatography–mass spectrometry-based
label-free quantitative proteomics. Mass spectrometry raw data files
have been deposited in an international public repository (MassIVE
proteomics repository at https://massive.ucsd.edu/) under data set # MSV000086887. In the 22 samples of perilymph analyzed,
632 proteins were detected, including the inner ear protein cochlin,
a perilymph marker. Of these, 14 proteins were modulated by IP, and
three proteins were modulated by IT dexamethasone. In both IP and
IT dexamethasone groups, VGF nerve growth factor inducible was significantly
upregulated compared to control. The remaining adjusted proteins modulate
neurons, inflammation, or protein synthesis. Proteome analysis facilitated
by the use of hollow microneedles shows that route of dexamethasone
administration impacts changes seen in perilymph proteome. Compared
to IT administration, the IP route was associated with greater changes
in protein expression, including proteins involved in neuroprotection,
inflammatory pathway, and protein synthesis. Our findings show that
microneedles can mediate safe and effective intracochlear sampling
and hold promise for inner ear diagnostics.