Polyharmonic Vibrations of Human Middle Ear Implanted by Means of Nonlinear Coupler

This paper presents a possibility of quasi-periodic and chaotic vibrations in the human middle ear stimulated by an implant, which is fixed to the incus by means of a nonlinear coupler. The coupler represents a classical element made of titanium and shape memory alloy. A five-degrees-of-freedom model of lumped masses is used to represent the implanted middle ear for both normal and pathological ears. The model is engaged to numerically find the influence of the nonlinear coupler on stapes and implant dynamics. As a result, regions of parameters regarding the quasi-periodic, polyharmonic and irregular motion are identified as new contributions in ear bio-mechanics. The nonlinear coupler causes irregular motion, which is undesired for the middle ear. However, the use of the stiff coupler also ensures regular vibrations of the stapes for higher frequencies. As a consequence, the utility of the nonlinear coupler is proven.

Immunohistochemical and qPCR Detection of SARS-CoV-2 in the Human Middle Ear Versus the Nasal Cavity: Case Series

Viral infections have already been implicated with otitis media and sudden sensorineural hearing loss. However, the pathophysiology of COVID-19 as it relates to otologic disorders is not well-defined. With the spread of SARS-CoV-2, it is important to evaluate its colonization of middle ear mucosa. Middle ear and nasal tissue samples for quantitative RT-PCR and histologic evaluations were obtained from post-mortem COVID-19 patients and non-diseased control patients. Here we present evidence that SARS-CoV-2 colonizes the middle ear epithelium and co-localizes with the primary viral receptor, angiotensin-converting enzyme 2 (ACE2). Both middle ear and nasal epithelial cells show relatively high expression of ACE2, required for SARS-CoV-2 entry. The epithelial cell adhesion molecule (EpCAM) was use as a biomarker of epithelia. Furthermore, we found that the viral load in the middle ear is lower than that present in the nasal cavity.

The Effect of Ossicular Chain Disorders on Sound Transmission and Tinnitus Perception using Electrical Model

Human middle ear ensures sound transfer due its ossicular chain, any disorder or abnormalities in this structure leads to a conductive hearing loss (CHL). Tinnitus is a health problem, associated with hearing loss, it remains a devastating symptom. In this work, we present an electrical model of the human middle ear including middle ear cavities (ZMEC), tympanic membrane with ossicular chain (ZTOC), and stapes complex with cochlea load (ZSC). This model is modified to represent more closely the related pathologies affecting the middle ear. We will focus our analysis on ossicular chain disorder by studying the effect of increasing ossicular chain (OC) stiffness and mass in both normal middle ear structures and disconnected stapes superstructure. The change in middle ear structures and impedance allows us to simulate ossicular chain disorder effects and analyze their impact on sound transmission. This analysis allowed us to know if this disorder can eventually cause tinnitus. The results showed that the effect of ossicular chain anomalies can be studied based on frequency response of middle ear transfer function by applying only the principle of mass and stiffness, and demonstrate compared to clinical results the efficiency and simplicity of using the electrical model.

Alteration of payload in extracellular vesicles by crosstalk with mesenchymal stem cells from different origin

Background The application of extracellular vesicles (EVs) derived from mesenchymal stem cells (MSCs) requires customized materials to target disease or cell damage. We hypothesized that EVs exert different inflammatory effects on one recipient cell, although stem cells of different origins in humans have similar payloads. Results Here, the payload of EVs released by crosstalk between MSCs and human middle ear epithelial cells (HMEECs) extracted from adipose tissue, bone marrow and tonsils significantly increased the level of anti-inflammatory factors. EVs derived from the co-culture medium decreased TNF-α, COX-2, IL-1β, and IL-6 levels to approximately zero within 3 h in HMEECs. Expression of miR-638 and amyloid-β A4 precursor protein-binding family A member 2 was analyzed using microarrays and gene ontology analysis, respectively. Conclusions In conclusion, stem cells of different origins have different payloads through crosstalk with recipient-specific cells. Inducing specific factors in EVs by co-culture with MSCs could be valuable in regenerative medicine. Graphical abstract