Nose and throat studies reveal why people with COVID-19 lose their sense of smell

Researchers studying tissue removed from the patient’s nose during surgery have found reasons why so many people with COVID-19 lose their sense of smell in the absence of other symptoms I believe.

In their experiments, they found very high levels of angiotensin-converting enzyme II (ACE-2) only in the odor-causing areas of the nose. This enzyme is believed to be the “entry point” that makes it possible Coronavirus Enter the cells of body Causes infection.

Researchers will use the findings released today (Wednesday) European Respiratory Journal, Provides clues as to why COVID-19 is highly infectious, suggesting that targeting this part of the body may provide a more effective treatment.

The study was conducted by Prof. Andrew P. Lane, Director of Department of Rhinology and Skull Base Surgery, and Dr. Mengfei Chen, a researcher and colleague at Johns Hopkins University School of Medicine, Baltimore, USA.

Professor Lane says: “COVID-19 olfaction loss is of particular clinical interest to me because I specialize in nasal and sinus problems. Other respiratory viruses commonly cause olfaction loss due to airflow obstruction. In addition to swelling of the nasal cavity, the virus can cause loss of olfaction in the absence of other nasal symptoms.”

The team used tissue samples behind the nose of 23 patients resected during endoscopic surgery for conditions such as tumors, chronic rhinosinusitis, and inflammatory disease of the nose and sinuses. They also studied biopsies from the trachea of ​​7 patients. No patient was diagnosed with coronavirus.

In the lab, researchers Tissue sample Detect and visualize the presence of ACE2 under the microscope and compare ACE2 levels in different cell types and parts of the nose and upper respiratory tract.

They found most ACE2 in the cells behind the olfactory epithelium, the region of the back of the nose where body odors were detected. The levels of ACE2 in these cells were 200-700 times higher than in other tissues of the nose and trachea, and were similar in all samples of the olfactory epithelium regardless of whether the patient was treated for chronic sinusitis. It was a high level. Status. ACE2 was not detected in olfactory neurons or neurons that transmit information about olfaction to the brain.

Dr. Chen said: “By this method, we found that the level of ACE2, the “entry point” protein of COVID-19, was highest in the nasal area, which enables olfaction. From these results, it is possible that this area of ​​the nose is where the coronavirus has entered the body.

“The olfactory epithelium is the part of the body that is very easy for the virus to reach, and is not buried deep in the body. It may explain.”

Professor Lane adds: “We are currently conducting further experiments in the laboratory to see if the virus actually uses these cells to access the body and infect it. Nose.”

Not involved in the study, Tobias Welte is a former chairman of the European Respiratory Society, a professor of lung medicine, and a director of the Department of Pulmonary Infectious Diseases at the University of Hanover, Germany. He said: “I know that many common respiratory infections, such as coughs and colds, can temporarily lose us Smell With stuffy nose and sore throat. Previous studies have shown that COVID-19 is abnormal in that lack of off-flavours can be the only symptom. This is a smart study investigating why this is so.

“It’s part of us nose It is also where coronaviruses build a scaffold in the body that causes odors. This finding will need to be confirmed, but it offers a possible new avenue for treating infections. “

Other researchers who participated in this study include Wenjuan Shen, Nicholas R. Rowan Heather Kulaga, Alexander Hillel, Murugappan Ramanathan Jr.