A new study might solve the riddle of this perplexing complication and point the way to new treatments for a range of long COVID symptoms.
By Becky Upham
December 30, 2022
Scientists observed unusual inflammation and cell destruction in the noses of people with ongoing smell loss.
According to recent study, some patients who have COVID-19 may not be able to regain their sense of smell since there is persistent inflammation that harms and kills nasal cells.
The study, a result of a partnership between scientists at Duke, Harvard, and the University of California, San Diego, contributes crucial new information about a problem that has afflicted millions of patients whose sense of smell has not entirely restored following COVID-19. On December 21, 2022, the journal Science Translational Medicine published the findings online.
Millions Have Not Fully Recovered Their Sense Of Smell After COVID-19
According to the senior author of the study and associate professor of head and neck surgery, communication sciences, and neurobiology at Duke University School of Medicine in Durham, North Carolina, Bradley Goldstein, MD, PhD, loss of smell is a symptom that has long been linked to COVID-19 infection.
The majority of patients who experience changed smell during the acute phase of a viral illness will regain scent within the next one to two weeks, but some people may not, according to Dr. Goldstein.
According to a research published in July 2022 in The BMJ, an estimated 15 million COVID-19 survivors worldwide experience ongoing loss of smell even after they have recovered from the virus.
There is a significant unmet need for developing these kinds of medicines, according to Goldstein. "One of the main motivations for our study is that we really don't have extremely specialized or effective treatments for these types of scent loss," he adds.
Researchers Found Inflammation In The Noses Of People With Long COVID Smell Loss
Researchers were able to closely study the cells of people who have long-term COVID smell loss versus others who have a normal sense of smell by employing a biopsy-based technique (taking a small sample of tissue) in the olfactory part of the nose, according to Goldstein.
Researchers examined 24 biopsies, including those from nine patients who had long-term smell loss as a result of COVID-19, for olfactory epithelial (the layer of tissue in the nose where smell nerve cells are situated).
T-cells, a type of white blood cell that is crucial to the immune system, as well as inflammation were widely present, according to the researchers. This form of inflammation is "not what we would ordinarily anticipate to see; it almost resembles an autoimmune-like disease in the nose," according to Goldstein.
There was no sign of the particular inflammation among those who did not have long-term scent loss as a result of COVID-19.
In addition, the researchers discovered less olfactory sensory neurons in the sufferers of olfactory loss, which may indicate that the aberrant immune response killed those crucial sensory cells in the nose.
Findings May Point The Way To Potential Treatments For Long COVID Loss Of Smell
The director of the Center for Infection and Immunity at the Yale School of Medicine in New Haven, Connecticut, Akiko Iwasaki, PhD, states that these findings "give critical insights into what can induce long-term smell loss in some persons who have chronic COVID." Dr. Iwasaki is the co-lead investigator of numerous research on extended COVID, despite the fact that she was not part in this investigation.
The first step in developing medicines to restore smell, according to Goldstein, is to identify the areas in the nose that are destroyed and the cell types involved. Researchers found it reassuring that the sensory neurons continued to show signs of healing even after the prolonged aberrant immune response.
According to the study's authors, therapies that lessen this immune response or boost the healing processes inside these patients' nostrils may aid in at least partial restoration of smell. They suggested using lotions or sprays as one therapy option to stop the immune cells that cause inflammation in the nasal epithelium.
According to Goldstein, researchers should conduct future studies on a bigger sample size. "A lot of concerns remain regarding what these cells are doing. To try to solve the issue, we need to determine whether there are any particular medication targets we can utilize, the expert explains.
Smell Research May Help Studies On Other Long COVID Symptoms Like Fatigue
According to Goldstein, long-term COVID can have a variety of various effects on the body's organs and systems, with scent loss being only one of several symptoms. We were lucky that the olfactory lining in the nose, which is the tissue we were interested in examining, is easily accessible and rather simple to biopsy, the researcher explains.
Researchers studying other long-term COVID symptoms that can't be researched in the same way as loss of smell, such as weariness, shortness of breath, and brain fog, may find this information to be helpful.
For understanding what is occurring in those other parts of the body that might be driven by comparable biological mechanisms, Goldstein says, "our observations on T-cells and inflammation in the nose could be potentially relevant."
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