A mechanism has been identified that may explain why some people with COVID-19 lose their sense of smell, according to research published Feb. 1 in Cell.
Researchers from NYU Grossman School of Medicine and Columbia University, both based in New York City, explored the molecular consequences of SARS-CoV-2 infection in golden hamsters and olfactory tissue taken from 23 human autopsies.
They found that the virus indirectly decreases action of olfactory receptors, which detect the molecules associated with odors. According to the study authors, COVID-19 appears to cause longer-lasting disruption in chromosomal regulation of gene expression that could prevent the restoration of olfactory receptor transcription even after the virus is cleared.
The study may also shed light on other neurological lingering effects of COVID-19 such as "brain fog," headaches and depression.
"Our findings provide the first mechanistic explanation of smell loss in COVID-19 and how this may underlie long COVID-19 biology," said co-corresponding author Benjamin tenOever, PhD, professor at NYU Langone Health. "The work, in addition to another study from the tenOever group, also suggests how the pandemic virus, which infects less than 1 percent of cells in the human body, can cause such severe damage in so many organs."
In most cases, loss of smell lasts only a few weeks, but for more than 12 percent of people with COVID-19, olfactory dysfunction persists in the form of ongoing reduction in the ability to smell or changes in how smells are perceived.
"The realization that the sense of smell relies on 'fragile' genomic interactions between chromosomes has important implications," Dr. tenOever said. "If olfactory gene expression ceases every time the immune system responds in certain ways that disrupts inter-chromosomal contacts, then the lost sense of smell may act as the 'canary in the coal mine,' providing early signals that the COVID-19 virus is damaging brain tissue before other symptoms present, and suggesting new ways to treat it."