Injected biomaterial allows new blood vessels to grow, scientists say
Published Tuesday January 13th, 2009
TORONTO - Canadian scientists have successfully grown new blood vessels in laboratory animals by injecting a collagen-based material that attracts new cells to regenerate tissue.
The researchers at the University of Ottawa Heart Institute are among a number of groups worldwide working on growing blood vessels to replace those that have been damaged. Diseased coronary arteries, for instance, can lead to potentially fatal heart attacks.
The Heart Institute team has created an injectable material that forms a "smart scaffold" inside the body, which sends out signals to particular cells in the blood. Those cells, called progenitors, can give rise to the type of cells that make up the lining of blood vessel walls.
"The biomaterial attracts cells to it," principal investigator Erik Suuronen said Tuesday from Ottawa. "And then once the cells are there, it promotes their survival - so it keeps them alive once they get there - and it basically helps them to provide further signals to tell other cells to come to that area in order to regenerate the blood vessels."
In experiments with laboratory rats, the team injected the scaffolding material into the muscle of a back leg, which had no blood flow after the main artery was cut. Then they watched what happened over the next two weeks.
"We found that our smart scaffold caused a greater number of progenitor cells within the blood," Suuronen said. "And then when you look at the tissue after that two-week period, there were more of those cells in the muscle tissue that was treated with smart scaffold, there were more blood vessels."
"And using a device that can measure blood flow, we found greater perfusion and blood circulation in the limb."
To understand how the biomaterial works to form the framework for blood vessel growth, he suggested picturing a muscle as an anthill filled up with water.
"It's not just a tube. I guess I could describe it as an anthill that has all the different tunnels and chambers. If you turn your garden hose into that anthill, it would fill the spaces - the tunnels and chambers."
"So that's sort of how the scaffold works when you inject the material into a muscle. All those spaces that it finds is where the scaffold will enter in and gel."
He said a number of new blood vessels were formed in the rats' legs, bypassing the cut artery, and normal blood flow was restored.
Among the group's eventual goals is to grow new coronary arteries to prevent heart attacks, possibly doing away with the need for bypass surgery or stenting.
Dr. Anthony Atala, director of regenerative medicine at Wake Forest University in Winston-Salem, N.C., called the research "a nice advance in terms of using these biomaterials."
"And what this paper demonstrates clearly is that by adding specific factors you do enhance the regeneration of certain tissues. And that's a very good observation, which actually leads to more promising applications in the future," said Atala, whose lab has successfully regenerated some tissue types, as well as working on growing new blood vessels.
Commenting on the work, Toronto researcher Dr. Ren-Ke Li called the study "a very good paper. I'm pretty impressed."
Li, a principal investigator at the McEwen Centre for Regenerative Medicine, said reduced blood flow is a problem that can affect any of the major organs, and scientists have long dreamed of finding a way to induce new blood vessel growth to treat a variety of diseases.
By using "recruiting factors" in their biomaterial, the Ottawa researchers have demonstrated a way to get progenitor cells to home in on a specific area, said Li, noting that McEwen scientists are also working on a biomaterial to create new blood vessels, but using different components.
Suuronen said it could be years before the Heart Institute's biomaterial is tested in people.
Further animal research is needed, he said, including trying it out on larger animals like pigs to see if new arteries to supply the heart could be formed.
The work was recently published online in the Journal of the Federation of American Societies for Experimental Biology.
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