One of the Coronavirus symptoms among many includes loss of smell in infected people. Likewise, people with a common cold or flu also experience loss of smell but there is a difference between the two. In a new study, researchers 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 the study, researchers found that extremely high levels of angiotensin-converting enzyme II (ACE-2) only in the area of the nose responsible for the smell. This Enzyme is thought to be the ‘entry point’ that allows coronavirus to get into the cells of the body and cause an infection. To begin with, 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 sinus. 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 compare levels of ACE2 in different cell types and parts of the nose and upper airway. 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 smells. The levels of ACE2 in these cells was between 200 and 700 times higher than other tissue in the nose and trachea, and they found similarly high levels in all the samples of the olfactory epithelium, regardless of whether the patient had been treated for chronic rhinosinusitis or another condition. ACE2 was not detected on olfactory neurons, the nerve cells that pass information about the smell to the brain.
The study was done by Professor Andrew P. Lane, director of the division of rhinology and skull base surgery, and Dr. Mengfei Chen, research associate, and colleagues from Johns Hopkins University School of Medicine, Baltimore, USA.
“This technique allowed us to see that the levels of ACE2 – the COVID-19 ‘entry point’ protein were highest in the part of the nose that enables us to smell. These results suggest that this area of the nose could be where the coronavirus is gaining entry to the body. The olfactory epithelium is quite an easy part of the body for a virus to reach, it’s not buried away deep in our body, and the very high levels of ACE2 that we found there might explain why it’s so easy to catch COVID-19,” said by Dr. Mengfei Chen.
In an experiment to find why people suffering from COVID-19 lose the sense of smell, researchers found extremely high levels of angiotensin-converting enzyme II (ACE-2) only in the area of the nose responsible for the smell. One of the main differences that have surfaced is also COVID-19 patients lose their sense of smell, but they can breathe freely without any running or blocked nose.
They can also not detect sweet and bitter taste.