Once the brain cells were injected into the adjoining gel, the cells emitted chemicals that impelled the engineered vessels to germinate new branches, widening the network. A similar system could supply blood to engineered tissue before transplant into the body.
After joining the UW last year, Zheng collaborated with the Puget Sound Blood Center to see how this research platform would work to transport real blood.
The engineered vessels could transport human blood smoothly, even around corners. And when treated with an inflammatory compound the vessels developed clots, similar to what real vessels do when they become inflamed.
The system also shows promise as a model for tumor progression. Cancer begins as a hard tumor but secretes chemicals that cause nearby vessels to bulge and then sprout. Eventually tumor cells use these blood vessels to penetrate the bloodstream and colonize new parts of the body.
When the researchers added to their system a signaling protein for vessel growth that's overabundant in cancer and other diseases, new blood vessels sprouted from the originals. These new vessels were leaky, just as they are in human cancers.
"With this system we can dissect out each component or we can put them together to look at a complex problem. That's a nice thing—we can isolate the biophysical, biochemical or cellular components. How do endothelial cells respond to blood flow or to different chemicals, how do the endothelial cells interact with their surroundings, and how do these interactions affect the vessels' barrier function? We have a lot of degrees of freedom," Zheng said.