"This is the world's first implantation of a tissue-engineered blood vessel produced in the laboratory," says Todd McAllister, PhD, president and chief operating officer of Cytograft Tissue Engineering. "What is novel about this approach is we are able to build the vessel without any exogenous materials. The vessels are built with the patient's own cells."
The tissue-engineered blood vessels have either been grown or are in the process of being grown for six patients. Two have been implanted in kidney dialysis patients to offset damage in shunts placed in blood vessels of their arms used for dialysis. A third patient is expected to have the implant early next year.
The team is able to take two cell types -- skin and the inner lining of vessels -- from the patient's own body. The skin is grown into sheets, wrapped around a medical tube, and fused together, forming a vessel. Just before implantation into the patient, cells grown from the inner lining of the patient's own veins are cultured and grown within the engineered vessel.
But the largest benefit is that because the cells are the patient's own, there are no problems with rejection, McAllister explains. "There are no signs of failure or blood clots thus far in either patient receiving the implant."
Kidney Patients Get First Try
Initially the researchers plan to use the engineered vessels in patients with end-stage kidney disease undergoing regular dialysis. Because blood must be pumped through a shunt in the arm, often patients have failure of the shunts with damage from repeated use.
While synthetic vessels work well in larger vessels, the grafts don't work as well in smaller vessels in the arm, he says. "Roughly 25% of the grafts fail."
The second projected usage will be for lower limb salvage to prevent some of the 180,000 amputations that occur annually due to lack of blood flow in the legs, he says. Although stenting can be used in the thigh region, it is not as successful in the lower leg, he says.
One day, the engineered vessels may also provide heart patients without suitable vessels for harvest with engineered ones to bypass blockages in the heart arteries as well as repairs of some heart defects, he says.
Although the first patient to receive an implant has only had it for six weeks, the engineered vein appears to be strong, McAllister says. "This is an incredible challenge because the vein must be punctured up to six times a week for dialysis."
The researchers now are planning a trial of the biologically engineered blood vessels in kidney dialysis patients with vessel failure in the arm. They plan to recruit 200 patients and follow them for 12 to 18 months.
"This is quite an exciting area of research," comments Robert Eckel, MD, president of the American Heart Association and professor of medicine at the University of Colorado at Denver and the Health Sciences Center, Denver. "There is a great need. This is an important area of bioengineering. The applications are broad and could benefit the quality of life of a great number of people."