COVID-19: Cells causing odor loss identified

Temporary loss of odor and anolence is one of the first common symptoms of COVID-19. An international research team led by a neuroscientist at Harvard Medical School (HMS) has discovered what causes COVID patients to temporarily lose their sense of smell.

In a report issued by Scientific progress On Friday, July 24, researchers found that olfactory neurons (OSNs) do not express a specific gene that encodes ACE2. This is the receptor protein for SARS-CoV-2, the virus that causes COVID-19, to enter cells of the human body.

In the report published on HMS websiteInstead, receptor proteins are expressed in cells that provide metabolic and structural support for OSN. ACE2 was also found in specific populations of stem and vascular cells.

No need to replace olfactory neurons

These findings suggest that anosmia may be caused by a non-neuronal type of infection rather than olfactory neurons.

“Our findings show that the new coronavirus alters a patient’s sense of smell by affecting the function of supporting cells rather than directly infecting neurons.”

Datta added that their findings mean that, in most cases, SARS-CoV-2 infections are unlikely to cause permanent damage to the olfactory circuit and permanent anesthesia. Extended cases of odor loss, added by neurobiologists, are associated with mental and social health conditions such as depression and anxiety.

Relation: New study suggests causal relationship between loss of olfaction and memory problems

“Once the infection goes away, I think it’s good news, because there’s no need to replace olfactory neurons or rebuild them from scratch,” Datta said. However, HMS neurobiologists acknowledged that “more data and a better understanding of the underlying mechanism are needed to confirm this conclusion.”

CoV-2 entry gene tracking

The team poured previously published RNA-Seq from macaques, marmosets, and the entire human olfactory mucosa (WOM). All CoV entry-related genes were found in all WOM samples. Further validation was performed by studying data from mice to verify that ACE2 and other genes associated with CoV-2 entry are expressed in the olfactory epithelium.

Researchers then quantified gene expression of scSeq obtained from four human nasal biopsy samples from a previously published study Natural neuroscience February last year. Quantified gene expression did not result in the presence of ACE2 and TMPRSS2, another genes involved in the entry of SARS-CoV-2 into human cells. However, both genes were found in feeder cells and horizontal basal cells (HBC). Supporting cells wrap sensory neurons, provide structural and metabolic support, and also help regenerate the olfactory epithelium after injury.

Additional testing also revealed that after injury, ACE2 and TMPRSS2 were expressed in feeder cells and a subset of HBCs, and activated HBCs expressed higher levels of ACE2 compared to their resting counterparts. It was.

Anosmia: one of the earliest SARS-CoV-2 indicators

Temporary loss of olfaction or anorexia is one of the most commonly reported indicators of COVID-19. Compared to other reported symptoms such as cough and fever, Research suggests Its anosmia is a more reliable indicator.

Relation: Loss of olfaction and taste: unique manifestations of COVID-19

April 13th last year, University of California-San Diegoo Established empirical results strongly link sensory loss such as anesthesia to COVID-19. The UCSD team investigated 1,480 patients with flu-like symptoms. In this sample, 102 individuals tested positive for the new coronavirus. Dr. Carrollyan explained that more than 70% of COVID-19 positive patients reported improved olfaction at the time of the study.

Research published in medRXiv On May 24, last year, we will investigate the effects of SARS-CoV-2 on odor loss as well as taste and chemosensory-chemosensory disorders. The studies included in the report showed an average of 80% loss in normal olfactory function, 69% in taste and 39% in normal chemical function.