A study conducted on mouse and human brain tissue highlights the ability of the new coronavirus to infect neurons and alter blood vessels in the brain, which can decrease its oxygen supply and lead to cell death.
- Research conducted in vivo in mice and in vitro in human brain organoids shows that SARS-CoV-2 infects neurons in the brain by binding to a protein called ACE2.
- This has the effect of reducing the oxygen supply to neuronal cells and leading, in the most serious cases, to ischemic strokes.
A Covid-19 infection doesn’t just damage the lungs. In addition to causing pulmonary, cardiovascular and renal complications, SARS-CoV-2 is also capable of infiltrating the central nervous system and causing major damage there.
This is highlighted by a new study by researchers from Yale University (United States), Inserm and AP-HP, published in the Journal of Experimental Medicine. By conducting three experiments in vitro on human cells, and in vivo on mice, the authors found that SARS-CoV-2 can infiltrate the central nervous system, where infection is associated with a variety of symptoms ranging from ailments headache and loss of taste and smell to impaired consciousness, delirium, strokes and cerebral hemorrhage.
A lack of oxygen supply to neurons
To find out if SARS-CoV-2 could infect neurons and other brain cell types, researchers conducted a first lab experiment on human brain organoids, 3D miniature organs grown in the lab from human stem cells. They then discovered that the new coronavirus could invade these organoids, and use the neuronal cells to replicate. The virus appears to facilitate its replication by boosting the metabolism of infected cells, while neighboring uninfected neurons die when their oxygen supply is reduced. SARS-CoV-2 uses the same process that allows it to enter lung cells. It binds to a protein called ACE2, which is also produced by neurons.
According to in vivo research on mice genetically modified to produce human ACE2, the new coronavirus was also able to infect their brains, which caused serious damage to cerebral blood vessels. In humans, such damage could disrupt the oxygen supply to the brain. Central nervous system infection was much more lethal in mice than infections limited to the lungs.
A risk of ischemic stroke
In a third experiment, the researchers analyzed the brains of three patients who died of Covid-19. SARS-CoV-2 was detected in cortical neurons of one such patient, and infected brain regions were associated with ischemic strokes, in which decreased blood supply leads to localized tissue damage and cell death. Micro-infarctions were detected during the brain autopsies of the three patients.
For the researchers, these results show that “neurons can become a target of SARS-CoV-2 infection, with devastating consequences of localized brain ischemia and cell death”.
They now intend to continue their research in order to study “which could predispose some patients to central nervous system infections”as well as “to determine the route of invasion of SARS-CoV-2 in the brain and the sequence of infection in different types of central nervous system cells, which will help validate the temporal relationship between SARS-CoV-2 and infarcts ischemic in patients”.
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