Researchers from Osaka University may have discovered an adult vascular endothelial stem cell (VESC). This discovery may open the door to generating fully functional blood vessels for individuals with blood vessel disorders. The study was published in Cell Stem Cell.
Prior research done by the team had identified a population of endothelial cells (ECs) from the inner most layer of blood vessels with properties resembling stem cells. From there, the team sought to find cell-surface protein markers that specifically define these endothelial stem cells.
The researchers uncovered a highly abundant glycoprotein called CD157 expressed on a small fraction of the EC population. After isolating CD157+ ECs, they tested their ability to regenerate blood vessels by injecting them into mice with damaged liver vessels.
"The results were more than we could have hoped for," said Nobuyuki Takakura, who led this study. "A month after transplantation, the CD157-enriched cells generated fully functional portal veins, portal venules, sinusoids, hepatic venules, and arteries—essentially, every type of blood vessel found in a healthy liver."
To further prove they had discovered a VESC, the team used a fluorescent reporter to follow the fate of the cells in healthy mice. A year after injection, the cells continued to replenish normal blood vessel tissue in the liver as a functioning, native stem cell would. The team also tried treating another blood vessel-related disorder called Hemophilia A, a rare bleeding disorder in which blood does not clot properly. When the VESCs from healthy mice were injected into a mouse model of hemophilia A, the cells began generating new liver blood vessels and levels of clotting factor shot up.
It also appears that the therapeutic potential of the cells extends beyond liver defects. VESCs from muscle tissue were used by the researchers to treat limb ischemia in mice. The study could offer options for cell-based treatments of a variety of blood vessel disorders.
Image: Vascular Endothelial stem cell (VESC) system in the liver. Vascular injury induces activation of VESCs. VESCs proliferate and replace the damaged ECs. New blood vessels are derived from VESCs. Image courtesy of ©2018 Wakabayashi et al., Cell Stem Cell 22, 1-14.