The cause of olfactory defects caused by sinusitis is identified

experiments in mice and human tissue, U.S. scientists recently discovered that the nasal neural stem cells responsible for smelling can be transformed to persist long-term inflammation of chronic sinusitis. The researchers believe the results suggest that the ability of stem cells to change their identity to participate in the immune response may be a protective mechanism used to keep olfactory tissue regenerated after inflammation subsides.
the paper, published in the September issue of Cell-Stem Cells, scientists say the study could also lead to the search for better treatments for the olfactory defects commonly associated with chronic sinusitis.
addition to nasal congestion, chronic sinusitis is characterized by persistent inflammation of the skull and nasal tissue, resulting in congestion, thick mucus and facial pain. Most patients have some degree of olfactory deficiency. A percentage of patients also experience worrying loss of sense of smell, but it is not clear how sinusitis affects the sense of smell.
for many patients, separate mucus and tissue swelling blockages do not explain why they lose their sense of smell. "Losing that feeling is a real disability." Andrew Lane, professor of head and neck surgery at Johns Hopkins University School of Medicine, said: "People can't sense smells that warn them they're about to face danger, such as smoke, gas leaks or food decay. Since most of the perceived food flavor comes from the sense of smell, these people lose the ability to taste, affecting their overall enjoyment of life. The
Lane is an otolaryngologist who specializes in the treatment of sinus disease patients in clinical practice. Standard treatments for reducing inflammation with steroids are not always effective and are accompanied by side effects such as bone weakness, vision changes, weight gain and vulnerability to infection, he said. Local steroids in nasal sprays and flushes can improve sinus charge and other symptoms, but usually do not restore a sense of smell.
, the neurons responsible for smell in the mucous membrane lining are called olfactory neurons, and they usually have significant regenerative abilities, even if they are severely damaged. In previous studies, Lane and Randall Reed, a molecular biologist at the university, created and studied mouse models that showed that olfactory neurons damaged by chronic sinusitis and nasal inflammation could not regenerate from olfactory stem cells called horizontal substrate cells.
In order to find out why this stem cell regenerative substrate cell cannot regenerate olfactory neurons in cases of chronic sinusitis, Lane and postdoctoral researcher Mengfei Chen studied tissue samples and cultivated olfactory inflammation model mice in patients with chronic sinusitis, a human model of chronic sinusitis.
they sampled the olfactory tissue in mice early in the experiment, then caused widespread inflammation in the mice and took samples again after 6 to 8 weeks.
researchers used specific markers to isolate olfactory horizontal substrate cells. The study found that in the later stages of inflammation, the base cells increase in size and number, but their ability to regenerate is turned off, which means that the substrate cells do not form new neurons.
similar to the mouse model, in olfactory tissue samples from patients with chronic sinusitis, scientists found an increase in the number and size of substrate cells and the production of inflammatory cytokines.
we now know that stem cells not only passively receive signals indicating that they are regenerateing new neurons, but actually convert their identities to participate in the immune response. "Our study also shows that as long as inflammation persists, these cells are in stem cell status and do not restore olfactory neuron regeneration. "
a possible evolutionary interpretation of this state of non-switching as a key protection function." These cells are close to the brain, which is an important defense. Lane said, "The body does not want any infectious substances that can cause sinus inflammation to enter the brain." As a result, these substrate cells are likely to evolve as the last line of defense and participate in the immune response, not just to create more olfactory cells.
researchers note that a deeper understanding of how inflammation affects olfactory tissue and olfactory sensory neuron deficiency should help identify treatments for nonsteroidal drugs to restore the sense of smell in patients with chronic sinusitis.
In addition to developing new drugs to protect neurons from damage or regenerate them after inflammation, the study could help scientists understand why new inflammatory treatments currently on the market, such as Dupilimab, can block protein pathologies in asthma and sinus dips to restore the sense of smell in patients with these diseases. (Source: China Science Journal Zhao Xixi)
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