Growing Body Parts: Artificial Blood Vessels from Muscle-Derived Stem Cells

Researchers at the University of Pittsburgh School of Medicine have developed artificial blood vessels that may revolutionize the way patients with heart and kidney disease receive treatment. The findings, which were presented at a conference of the Tissue Engineering and Regenerative Medicine International Society (TERMIS) on June 15, move away from traditional vessel grafting procedures to reveal a novel technique utilizing muscle-derived stem cells (MDSCs).

MDSCs are adult stem cells, not the hotly scrutinized embryonic stem cells that have become the subject of national debate. Adult stem cells exist as undifferentiated cells all throughout the body where they might replenish tissue that has become damaged or weakened. They have recently become an attractive subject for researchers due to their ready availability and evident potential for growing artificial tissue.

The University of Pittsburgh investigators, led by David A. Vorp, associate professor of surgery and bioengineering, began their study by spraying MDSCs onto porous, polyester urethane scaffolds in a process termed "bulk seeding." The cells were cultured for seven days in vitro before being implanted into the abdominal aortas of rats, where they remained for eight weeks prior to further studies.

The researchers found the results after this eight week period promising. Guided by signals in the surrounding environment, the novel grafts had assembled into mature arteries displaying the proper layering of cells found in naturally occurring vessels. In the rat model, the arteries remained free of blood clots, which plague other grafts currently on the market. Further studies are needed to confirm the clot-free nature of MDSC grafts.

"The next step is to demonstrate the use of the tissue-engineered blood vessel in a larger animal model, such as a pig, which has a coagulation system more similar to that in humans," Vorp said in a prepared report.

If the artificial vessels hold up against this next round of tests, it would be exciting news for clinicians who are currently limited by inadequate grafting options. If a patient needs a new blood vessel, surgeons will typically remove an artery or vein from her leg and graft them into the desired location. However, this is an imperfect procedure that is prone to blood clots, as are other commercially available synthetic grafts. If MDSC implants prove to be clot free, they would make for quicker, more efficient treatment.

"The advantage of our approach is that the graft could utilize the patient's own stem cells and be ready for implantation almost immediately.This suggests that we could make these available off-the-shelf,' which is an essential element for clinical translation," Vorp explained.

Each year in the United States roughly one million patients undergo revascularization procedures that require vessel grafting. Vorp's team hopes MDSCs will make these procedures quicker, cleaner, and more effective.

- By Neil Majithia.

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