Blood Vessels Created Using Adult Bone Marrow Stem Cells
By Ed Susman, United Press International, July 8, 2007
Using a person's own bone marrow, doctors were able to grow new blood vessels. However, in order for patients with diseased arteries to benefit from the test-tube grown vessels, a few more years of research will be required said researchers. Still, the accomplishment is yet another large step for adult stem cells and demonstrative of their therapeutic potential.
"Our studies show that bone marrow is an excellent source of stem cells that can be coaxed into creating blood vessels," Stelios Andreadis, associate professor in the University at Buffalo department of chemical and biological engineering, told United Press International.
Andreadis said that endothelial and smooth muscle cells make up the test tube created blood vessels.
"These stem cells can be used in regenerative medicine for cardiovascular applications," he said.
Especially for those found in and around the heart, the main reason for creating new blood vessels is for use in arteries said Andreadis. However, the blood vessels created in his laboratory are capable of being used, at the very least as, veins in humans right now.
The new blood vessels should be engineered to withstand internal pressures as high as 1,200 millimeters of mercury in order to have the strength to be used to replace diseased coronary arteries. This is 10 times above the normal limit. Having a top strength of about 200 mmHg, bone marrow stem cell derived blood vessels are not yet strong enough.
"We need to improve the matrix around which the cells grow in order to have strong enough blood vessels for replacing human arteries," he said. The researchers have already used tissue engineered vessels in animals such as sheep with good results, he said.
Cardiovascular Research recently published Andreadis' preliminary work. Providing a desirable alternative to the venous grafts now routinely done in patients undergoing coronary bypass operations, the paper demonstrated the potential for eventually growing tissue-engineered vessels out of stem cells harvested from the patients who need them.
A high 10-year failure rate, discomfort and pain at the donor site, and the limited availability of vessels are some of the disadvantages of venous grafts.
Using a tissue-specific promoter for alpha-actin (a protein found in muscles that is responsible for their ability to relax and contract) in conjunction with a fluorescent marker protein, Andreadis reported on a novel method for isolating functional smooth muscle cells from bone marrow.
One of the most important properties of blood vessels is their ability to proliferate and the ability to contract in response to vasoconstrictors. In their expression of several smooth muscle cell proteins, the tissue-engineered vessels performed similarly to native blood vessels.
Critical to the functioning of artificial blood vessels, both elastin and collagen are produced by the vessels. These components also give tissue their elasticity and strength.
The John R. Oishei Foundation of Buffalo and the Integrative Research and Creative Activities Fund in the Office of the Vice President for Research at the University at Buffalo, part of the State University of New York funded Andreadis' research.
"The work in Buffalo shows the promise that stem cells have in their ability to produce different structures," said S. Chiu Wong, associate professor of medicine at the Weill Medical College at Cornell University. "This pre-clinical work shows again that stem cells can be a rich source for development. It certainly remains a fruitful area of research."
Working on producing more coronary blood vessels is another aspect of stem cell research which Wong and his colleagues are working on. In an attempt to generate blood vessel growth, stem cells are injected directly into heart muscle. Wong and his team are part of a multicenter clinical trial involved to this particular study which has been funded by Baxter.