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A team of researchers after studying tissue removed from patients’ noses during surgery believe they may have discovered the reason why so many people with COVID-19 lose their sense of smell, even when they have no other symptoms .
In their experiments, they found extremely high levels of angiotensin-converting enzyme II (ACE-2) only in the area of the nose responsible for smoking. This enzyme is thought to be the “entry point” that coronavirus can get into the body’s cells and cause an infection.
The researchers say their findings, published in the European Respiratory Journal, provide clues as to why COVID-19 is so infected and suggest that targeting this part of the body could potentially provide more effective treatments.
The study was conducted by Professor Andrew P Lane, director of the Division of Rhinology and Basal Surgery, and Dr. Mengfei Chen, a research fellow, and colleagues at Johns Hopkins University School of Medicine, Baltimore, USA.
Professor Lane said: “I specialize in nasal and sinus problems, so the loss of smoking in COVID-19 is of special clinical importance to me. While other respiratory viruses generally cause loss of smoking due to the obstruction of airflow due to swelling of the nasal passages, this virus sometimes causes loss of smell in the absence of other nasal symptoms. “
The team used tissue samples from the back of the nose of 23 patients, removed during endoscopic surgical procedures for conditions such as tumors or chronic rhinosinusitis, an inflammatory disease of the nose and sinuses. They also studied biopsies from the trachea (windpipe) of seven patients. None of the patients had been diagnosed with coronavirus.
In the lab, the researchers used fluorescent dyes on the tissue samples to detect and visualize the presence of ACE2 under a microscope and to compare levels of ACE2 in different cell types and parts of the nose and upper airways.
They found by far the most ACE2 on the lining cells of the olfactory epithelium, the area at the back of the nose where the body detects odors. The levels of ACE2 in these cells were between 200 and 700 times higher than in other tissues in the nose and trachea, and they found similarly high levels in all samples of the olfactory epithelium, regardless of whether the patient was treated for chronic rhinosinusitis or a other condition. ACE2 was not detected on oil factor neurons, the nerve cells that transmit odor information to the brain.
Dr Chen said: “This technique showed us that the levels of ACE2 – the COVID-19 ‘entry point’ protein were highest in the part of the nose that enables us. These results suggest that this area of the nose could be where the coronavirus enters the body.The olfactory epithelium is a fairly easy part of the body for a virus to reach, it is not buried deep in our body, and the very high levels of ACE2 that we found there can explain why it is so easy to catch COVID-19. “
Professor Lane added: “We are now doing more experiments in the lab to see if the virus actually uses these cells to gain access and infect the body. If so, we can tackle the infection with antiviral therapies. delivered directly from the nose. “
Tobias Welte, who was not involved in the research, is the European Respiratory Society Past President, Professor of Pulmonary Medicine, and Director of the Department of Pulmonary and Infectious Diseases at Hannover University School of Medicine, Germany. He said: “We know that many common respiratory infections, such as coughs and colds, can cause us to temporarily lose our sense of smell in addition to a stuffy nose or a sore throat. Previous research has shown that COVID-19 is unusual in that it cannot smell alone. This is a clever study that examines why this may be the case. “
“It suggests that the part of our nose responsible for odor may also be the place where the coronavirus has a foot in the body. This finding will need to be confirmed, but it offers possible new possibilities for treating the infection,” added Worlds.
Other researchers who participated in this study include Wenjuan Shen, Nicholas R. Rowan, Heather Kulaga, Alexander Hillel, and Murugappan Ramanathan Jr.
(Except for the header, this story has not been edited by NDTV staff and is published from a syndicated feed.)
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