A Japanese-led research team has said it has identified how infections with the coronavirus can cause inflammation in blood vessels and blood clots, resulting in severe COVID-19 cases.

In severe cases, blood clots form in blood vessels throughout the body, leading to multiple organ failure.

The team, including researchers from Osaka University, Tokyo Medical and Dental University and Takeda Pharmaceutical, elucidated the mechanism by using vascular tissue made from induced pluripotent stem (iPS) cells.

The research results, published Friday in the U.S. journal Cell Stem Cell, are expected to facilitate the development of drugs to prevent serious COVID-19 complications.

Osaka University professor Takanori Takebe and other team members succeeded in producing vascular organoids, or miniature tissue, about 1 millimeter in diameter from human iPS cells and infecting them with the virus.

After the infected tissue was transplanted into mice, blood clots formed, meaning that the team succeeded in reproducing the symptom of the disease.

In addition, a comprehensive examination of the functions of genes after the infection showed that the so-called CFD factor, which supports immune response, has become active.

In experiments on monkeys, the team found that the administration of a drug that suppresses this factor weakens the immune response and curbs inflammation in blood vessels and the formation of blood clots.

"By utilizing organoids, we've become able to understand the detailed mechanism of vascular inflammation and promote research on infectious diseases," Takebe said. "By targeting CFD, we can also open up the possibility of diagnosing and treating people who are seriously ill."