July 26, 2012

Adult Stem Cells from Liposuction Used to Create Blood Vessels

By: Katie Williams, Ivanhoe Health Correspondent

(Ivanhoe Newswire) — Millions of patients affected by cardiovascular disease need small-diameter blood vessel grafts to help route their blood around blocked arteries. Now, researchers have created a new way to grow healthy, new small-diameter blood vessels from adult stem cells extracted during liposuction.

These blood vessels are grown in a lab and could solve large problems associated with grafting blood vessels elsewhere in the body, or from using artificial blood vessels that aren´t living tissue.

"For larger vessels that need grafting, one can use a synthetic vessel. If the vessel is greater than about 6 mm in diameter, then synthetic vessels are available and they work reasonably well. But for smaller diameter vessels, less than about 6 mm in diameter, there really is no suitable strategy for grafting," Matthias Nollert, Ph.D., the lead author of the study and associate professor at the University of Oklahoma School of Chemical, Biological and Materials Engineering, in Norman, Oklahoma, told Ivanhoe.

In the study, adult stem cells derived from fat are turned into smooth muscle cells, then "seeded" onto a thin collagen membrane. As the stem cells multiplied, the researchers rolled them into tubes matching the diameter of small blood vessels. "The nice part about this is because we roll the flat sheet, we can make it the appropriate length, the appropriate diameter and with the correct wall thickness because we manufacture them specifically," Dr. Nollert said. After 3 to 4 weeks, they grew into usable blood vessels.

Current small-diameter vessel grafts have an inherent risk of clotting, being rejected, or failing to function normally. However, these liposuction-derived vessels have good mechanical properties and are believed to contract normally when exposed to hormones. They also appear to prevent the accumulation of blood platelets, which cause arteries to narrow. However, Dr. Nollert and his team strive for a better outcome.

"The mechanical properties that we generate for these vessels are good, but we´re not recreating the physiological conditions of native vessels. We need to make these stronger. What your blood vessels really do is they don´t clot, and they have to contract and relax appropriately in response to agonists. Those two things, the thrombosis and the contraction responses, are things that other tissue engineered blood vessels that other people have worked on really have not gotten correct and we´re still working on getting that to the right place as well."

Using this technique has potential for "off-the-shelf" replacement vessels that can be used in graft procedures, and researchers hope to have a working prototype to test in animals within six months.

Source: American Heart Association´s Basic Cardiovascular Sciences 2012 Scientific Sessions