April 5, 2013
Stem Cells Could Build Better Blood Vessels, Boost Tissue Engineering
[Watch the Video: Engineering Blood Vessels ]
redOrbit Staff & Wire Reports - Your Universe Online
Those replacement organs often fail because of the difficulties associated with building blood vessels in order to keep their tissues alive. Now UM associate biomedical engineering professor Andrew Putnam said he has discovered why one of the main techniques used to build blood vessels does not work on a consistent basis, as well as how to correct the problem.
“It's not just enough to make a piece of tissue that functions like your desired target,” Putnam said in a statement obtained by redOrbit. “If you don't nourish it with blood by vascularizing it, it's only going to be as big as the head of a pen. But we need a heart that's this big," he added, displaying his fist as an example.
Currently, there are two primary methods that biomedical researchers use to build new capillaries, which are the smallest of the blood vessels and are responsible for exchanging oxygen, carbon dioxide and nutrients between blood and muscles or organs.
One group is working on drug compounds that would encourage existing blood vessels to branch into new tributaries, while the other is using a cell-based method. The second group includes Putnam´s team, and they are using cells to encourage blood vessel growth. That technique involves injecting cells with a scaffolding carrier known as fibrin near the exact location where new capillaries are supposed to form.
The latter method does not always work out well, though, and Putnam and his colleagues set out to discover why. They analyzed the cells that form blood vessels and found that the identity of the supporting cells was critical to the quality of the blood vessels that are formed.
Putnam and his colleagues found that if they used adult stem cells from bone marrow or fat, they wound up with “very robust vasculature that is that is very high quality,” but using more generic, readily-available connective tissue cells, the vessels that formed tended to be “leaky.” Their findings have been published online in Tissue Engineering Part A, and will also appear in a forthcoming print edition of the medical journal.
“The cells know what to do. You can take these things and mix them and put them in an animal,” the Michigan professor explained. “Literally, it's as easy as a simple injection and over a few days, they spontaneously form new vessels and the animals' own vasculature connects to them.”
“The adult stem cells from fat and bone marrow both work equally well. If we want to use this clinically in five to 10 years, I think it's crucial for the field to focus on a support cell that actually has some stem cell characteristics,” Putnam added. He hopes that eventually doctors will be able to obtain these support cells from the patients themselves and then inject them right at the site where the new blood vessels are required.