Scientists from the Institut Pasteur, the National Center for Scientific Research (France) and the University of Paris
Until recently it remained unclear whetherwhether the virus has a direct role in anosmia. According to one of the generally accepted hypotheses, it was assumed that temporary swelling of the olfactory gaps suppresses the air currents that transport odor molecules to the olfactory neurons.
French scientists have shed light on the mechanisms involved in anosmia during coronavirus infection. The study was conducted with the participation of patients with COVID-19 and supplemented with tests on model organisms.
Due to viral infection, sensory neurons loseolfactory cilia, which are necessary for "catching" stimulus molecules. The virus also enters sensory neurons, disrupting their function, and contributes to the death of epithelial cells as a result of apoptosis (programmed cell death). In the future, the coronavirus enters the olfactory bulb, where it provokes inflammatory reactions, and from there spreads to other nerve structures.
Diagram representing the different stages in the sensory system that contribute to anosmia associated with COVID-19. Credit: Institut Pasteur
ANDresearch demonstrates that loss of smellalso caused by damage to the sensory organs in the back of the nasal cavities. Scientists have noticed that SARS-CoV-2 affects not only sensory neurons, but also the olfactory nerve and olfactory nerve centers in the brain.
Another key finding from this studywas made as a result of observation in animal models, which showed that once the virus enters the olfactory bulb, it spreads to other nerve structures, where it causes a serious inflammatory response.
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Model organisms are organisms used as models for studying certain properties, processes or phenomena of living nature.