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Analysis: Stem Cells Create Blood Vessels

Posted on: Friday, 6 July 2007, 18:38 CDT

By ED SUSMAN

Doctors have succeeded in growing new blood vessels from a person's own bone marrow cells, but researchers said Friday they are still some years away from being able to use these test-tube grown vessels to replace diseased arteries.

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.

The blood vessels created in the test tube contain smooth muscle and endothelial cells, Andreadis said. These stem cells can be used in regenerative medicine for cardiovascular applications, he said.

The blood vessels created in his laboratory are capable of being used as veins in humans now, Andreadis said, but the main reason for creating new blood vessels is for use in arteries, especially for arteries in and around the heart.

He explained that in order to have the strength to be used to replace diseased coronary arteries, the new blood vessels should be engineered to withstand internal pressures as high as 1,200 millimeters of mercury -- or about 10 times normal. He said the blood vessels that have been grown from bone marrow stem cells have a top strength of about 200 mmHg.

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.

Andreadis recently published his preliminary work in Cardiovascular Research. The paper demonstrated the potential for eventually growing tissue-engineered vessels out of stem cells harvested from the patients who need them, providing a desirable alternative to the venous grafts now routinely done in patients undergoing coronary bypass operations.

Disadvantages with venous grafts include limited availability of vessels, pain and discomfort at the donor site and a high 10-year failure rate.

Andreadis reported on a novel method for isolating functional smooth muscle cells from bone marrow by using a fluorescent marker protein and a tissue-specific promoter for alpha-actin, a protein found in muscles that is responsible for their ability to contract and relax.

The tissue-engineered vessels performed similarly to native blood vessels in their expression of several smooth muscle cell proteins, the ability to proliferate and the ability to contract in response to vasoconstrictors, one of the most important properties of blood vessels.

The vessels also produce both collagen and elastin, which give connective tissue their strength and elasticity and are critical to the functioning of artificial blood vessels.

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.

Wong and colleagues are working on another aspect of stem cell research in producing more coronary blood vessels. They are involved in multicenter clinical trials in which stem cells are injected directly into the heart muscle in attempts to generate blood vessel growth. His work is funded by Baxter.

Andreadis' funding came from 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. His work is also funded by the John R. Oishei Foundation of Buffalo.

Source: United Press International

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