How does Covid-19 increase the risk of stroke?

A study by researchers at the University of California- Los Angeles Health Sciences may help explain how Covid-19 increases the risk of stroke.

Researchers tried to understand how the disease may increase the risk of a heart stroke using a 3D-printed model of the arteries of a patient who had suffered a stroke. As part of the study, researchers ran a fluid spiked with a Covid-19-like protein through the 3D model.

The 3D-printed silicone model of blood vessels in the brain was used “to mimic the forces generated by blood pushing through an artery that is abnormally narrowed, a condition called intracranial atherosclerosis,” as per an official release.

Through the study, researchers were able to show that these forces act on the cells lining the artery, and increase the production of a molecule called angiotensin-converting enzyme 2, or ACE2, which the coronavirus uses to enter cells on the surface of blood vessels.

“The flow directly influences ACE2 expression,” said Dr Jason Hinman, an assistant professor of neurology at the David Geffen School of Medicine at UCLA and the study's senior author.

The 3D models used by UCLA researchers for the study were created based on data from CT scans of blood vessels in a human brain. The inner surfaces of the models were then lined with endothelial cells similar to human blood vessels.

After observing the effect that imitation “viruses” in the bloodstream, researchers confirmed that the particles did indeed interact with the cells lining the blood vessel, mostly in the regions of the brain with higher levels of ACE2.

“This finding could explain the increased incidence of strokes seen in Covid-19 infections,” Hinman said.

The scientists further analysed which genes were turned on in the endothelial cells after binding with the coronavirus spike proteins. This led to the conclusion that a specific set of immune-response genes that are found in brain blood vessel cells were activated, but not in endothelial cells from other organs of the body.

“There's a unique brain endothelial response to the virus that may be helpful in identifying patients who have a higher risk for stroke,” Hinman explained.

The researchers intend to conduct follow-up studies using a live coronavirus in the 3D-printed blood vessel model to further confirm the findings of the study.

Other authors of the study include neurologists at the Geffen School of Medicine and scientists from UC San Francisco and the Veterans Health Administration. The paper was published in the journal Stroke.

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