The study found that the SARS-CoV-2 virus can infect the inner ear

Many Covid-19 patients have reported symptoms affecting their ears, including hearing loss and tinnitus

A new study from the Massachusetts Institute of Technology (MIT) and the Massachusetts Eye and Ear Institute provides evidence that the virus does infect cells in the inner ear, including hair cells that are essential for hearing and balance

The researchers used a new type of human inner ear cell model they developed, as well as hard-to-obtain adult human inner ear tissue for research

Professor Lee Gehrke, Hermann L.

Konstantina Stankovic, former associate professor of Harvard Medical School and former chief otology neurotology of Massachusetts Eye and Ear, he is now a former Foundation professor and head of the Department of Otorhinolaryngology-Head and Neck Surgery Stanford University School of Medicine who co-led the research

Ear infection model

Before the beginning of the Covid-19 pandemic, Gerke and Stankovic began a collaborative project to develop cell models to study human inner ear infections

In early 2020, after the SARS-CoV-2 virus appeared, the researchers changed their plans

She and Gerke decided to use the model system they were working on to study the SARS-CoV-2 infection

These cells can grow in a flat two-dimensional layer, or they can be organized into three-dimensional organoids
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In addition, the researchers obtained some hard-to-obtain samples of inner ear tissue.
Patients with these inner ear tissues are undergoing surgery because of a disease that causes severe dizziness, or a tumor that causes hearing loss and dizziness
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In human inner ear samples and stem cell-derived cell models, the researchers found that certain types of cells—hair cells and Schwann cells—express the proteins necessary for the SARS-CoV-2 virus to enter the cell
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These proteins include the ACE2 receptor found on the cell surface, as well as two enzymes, furan and the transmembrane protease serine 2, which help the virus to fuse with the host cell
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The researchers later discovered that this virus can actually infect the inner ear, especially hair cells, and to a lesser extent Schwann cells
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They found that other cell types in the model are not sensitive to SARS-CoV-2 infection
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The human hair cells studied by the researchers are vestibular hair cells, which are involved in sensing head movement and maintaining balance
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Cochlear hair cells related to hearing are difficult to obtain or produce in cell models
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However, the researchers showed that mouse cochlear hair cells also contain proteins that allow SARS-CoV-2 to enter
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Virus connection

The infection pattern the researchers found in their tissue samples appeared to be consistent with the symptoms of 10 Covid-19 patients who reported ear-related symptoms after infection
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Nine of these patients had tinnitus, six had dizziness, and all experienced mild to severe hearing loss
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Damage to cochlear hair cells can cause hearing loss, which is usually assessed by measuring otoacoustic emissions
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Otoacoustic emission is the sound made by sensory hair cells in response to auditory stimuli
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Of the six Covid-19 patients who underwent this test in the study, all of them had reduced or no otoacoustic emissions
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Although this study strongly suggests that Covid-19 may cause hearing and balance problems, the overall proportion of Covid-19 patients experiencing ear-related problems is unclear
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Stankovic said: "Initially, this was because routine testing was not easy for patients diagnosed with Covid, and when patients had more life-threatening complications, they would not pay too much attention to whether their hearing was Decline or whether there is tinnitus
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" "We still don't know what the incidence is, but our findings do call for more attention to the hearing symptoms of people who have been exposed to the new coronavirus
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Possible ways for the virus to enter the ear include the Eustachian tube connecting the nose and middle ear
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Stankovic said the virus may also escape from the nose through small openings around the olfactory nerve
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This will allow it to enter the brain space and infect the cranial nerves, including the cranial nerves that connect to the inner ear
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"This article provides very strong evidence that Sars-CoV-2 infects the inner ear and may be causally linked to hearing and balance problems.
Covid-19 patients have many symptoms of infection," said Yuri Agrawal, Professor of Head and Neck Surgery John Hope He was not involved in this research from Kings Medical School
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"Another exciting development in our field is the use of 2D and 3D external organs to observe the inner ear Sars-CoV-2 infection
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This provides a powerful platform for studying the effects of other exposures on the inner ear, including other infections, toxins and Cancer
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Researchers now hope to use their human cell model to test possible treatments for inner ear infections caused by SARS-CoV-2 and other viruses
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The research was funded by the National Institutes of Health, the Remondi Foundation, the Nancy Sayles Day Foundation, and the Barnes Foundation.
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