the consequence of a quasi-autoimmune reaction
In the nose of patients whose sense of smell does not return after Covid-19, scientists discover an abnormal presence of the immune system and a decline in olfactory neurons.
No longer being able to smell the smell of loved ones or a gas leak in the kitchen is the daily life of 80% of people with the Delta variant of Covid-19, and around 13% with the Omicron variant. If 95% of them regain their sense of smell within six months, some must undergo a long rehabilitation. To hope to avoid anosmia (loss of smell) to future patients, researchers analyzed the cells present in the nose of those who suffered from it. The strong presence of immune cells in the absence of the virus itself suggests preventive perspectives, intended to prevent destructive inflammation of the olfactory mucosa.
Fewer olfactory neurons in the nose of anosmic patients
“We expected to find evidence of changes or damage in the olfactory epithelium, but what we found on the immune level struck us”, tells Science and Future Dr. Bradley Goldstein, ENT doctor and surgeon at Duke University School of Medicine (USA), who led this work published in Science Translational Medicine. Three main types of cells are involved in the proper functioning of a healthy olfactory mucosa. Olfactory sensory neurons detect odors and transmit signals to the brain. Placed between the neurons, the sustentacular cells form a protective barrier. Behind, basal cells function as reserve stem cells. They are activated to help rebuild the olfactory epithelium after severe damage. These three cell types are affected in patients with lasting anosmia, observe the researchers.
To reach this conclusion, the scientists took a biopsy (a sample) of the olfactory mucosa from nine people who had post-Covid anosmia for at least four months. They then compared them to those of 15 people with a normal sense of smell, whether or not they had been infected.[…]
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