Impact of Systemic versus Intratympanic Dexamethasone Administration on the Perilymph Proteome

Abstract

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 ) 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.

Pyrolyzed Ultrasharp Glassy Carbon Microneedles

“…Just as for the 2PP-fabricated polymeric microneedles, [16] the pyrolyzed microneedles are able to penetrate the RWM successfully without ripping or tearing the RWM. Earlier our group [13,21,22] investigated the anatomical and functional consequences of microperforations introduced by 100 μm diameter polymeric microneedles through the guinea pig RWM in vivo. The studies conclude that the microperforations can heal within 72 h without causing significant anatomic or physiologic dysfunction.…”

“…[ 7–9 ] However, introduction of microperforations across the RWM significantly enhances both the rate and precision of delivery of therapeutic agents into the cochlea; [ 10,11 ] and 3) direct intracochlear therapeutic delivery across the RWM, which minimizes potential systemic side effects and ensures that a precise volume of medication passes the RWM barrier. [ 6,12,13 ]…”

“…[7][8][9] However, introduction of microperforations across the RWM significantly enhances both the rate and precision of delivery of therapeutic agents into the cochlea; [10,11] and 3) direct intracochlear therapeutic delivery across the RWM, which minimizes potential systemic side effects and ensures that a precise volume of medication passes the RWM barrier. [6,12,13] Therapeutic delivery across the round window membrane with either of the latter two methods requires perforation of the RWM, with potential severe consequences to hearing and balance, often due to ripping of the RWM (e.g., [14] ). In addition, as the cochlea is a closed constant-volume chamber, intracochlear injection of relatively large volumes into the inner ear may lead to hearing loss.…”

“…Significantly, similar 2PP-printed microneedles can perforate cadaveric human RWM tissue by the same "separation not scission" mechanism. [17] Further, we designed and fabricated hollow 100 μm diameter microneedles and aspirated 1 μL of perilymph across the GP RMW that was analyzed using proteomics, [13,22] again with no functional or structural consequence. Finally, after introducing microscale perforations across a GP RWM as well as across a proxy artificial membrane, the resulting perforations significantly enhance the therapeutic diffusion rate across the RWM.…”

Dual viscosity mixture vehicle for intratympanic steroid treatment modifies the ROS and inflammation related proteomes

“…The cochlea is covered with thick bone, and the inner ear compartment is isolated from other parts of the body by the blood labyrinthine barrier (LBL). Only a handful of studies have been able to access inner ear fluid for in-depth proteomic analysis ( Szeto et al, 2021 ; Durisin et al, 2022 ; van Dieken et al, 2022 ).…”