Researchers at the University at Buffalo Department of Chemical and Biological ngineering say that the bone marrow is an excellent source of adult stem cells, containing smooth muscle and endothelial cells, and add that these stem cells can be used in regenerative medicine for cardiovascular applications.
According to Dr. Stelios T. Andreadis, who co-authored the study with lead author Dr. Jin Yu Liu, a post doctoral researcher in Andreadis' Laboratory, the study provides an alternative to venous grafts that are routinely done in patients undergoing coronary bypass operations, the disadvantages of which include limited availability of vessels, pain and discomfort at the donor site, and a high 10-year failure rate.
During the course of study, the researchers used 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, to develop the new method for isolating functional smooth muscle cells from bone marrow.
Although the researchers concede that the tissue-engineered vessels are not yet strong enough for coronary application, they insist that these vessels function like native tissue and have various properties similar to blood vessels-viz. morphology, expression of several smooth muscle cell proteins, the ability to proliferate, and the ability to contract in response to vasoconstrictors.
The tissue-engineered vessels also produced both collagen and elastin, which give connective tissue their strength and elasticity and are critical to the functioning of artificial blood vessels. "These are the first tissue-engineered vessels to demonstrate the ability to make elastin in vivo," said Dr. Andreadis.
He also said that the smooth muscle cells isolated from the bone marrow were mesenchymal cells, the stem cells that can differentiate into several cell types and which would not trigger an immune reaction when transplanted into another individual.
"If true, this means that you may be able to develop a universal cell source for smooth muscle cells, so that you could potentially make these vessels into an 'off-the-shelf' product, available to any patient," Dr. Andreadis said.
The tissue-engineered vessels have already been found to work normally for five weeks upon implantation into sheep.
The researchers are now conducting further research to make these vessels stronger, and to study the differences between stem cells taken from older versus younger individuals.