CHICAGO, Nov. 17 (UPI) -- Using a postage-stamp-sized skin biopsy, researchers reported Sunday they now can grow an endless supply of blood vessels to replace blocked arteries in the heart or legs.
Currently, surgeons use vessels harvested from other areas of the body to replace blocked vessels in the heart or legs. But some patients require so many bypass surgeries that "they have no more vessels available for transplant. These are the patients who could benefit from this new technology," said Dr. Todd McAllister, president and CEO of Cytograft Tissue Engineering in Novato, Calif.
McAllister said he already has performed bypass surgeries on dogs using the engineered vessels and studies on humans will begin "in 12 to 18 months."
McAllister presented his research at the American Heart Association's Scientific Sessions 2002. So far he has grown new blood vessels from cells harvested from 11 patients with advanced heart disease. The skin cells were combined with cells taken from the inner lining of blood vessels in dogs.
The cells then were spread on a 9-inch-square scaffold and placed in a solution that promotes cells to grow into tissue.
When a thin "sheet of tissue" forms, the sheet is wrapped around a stainless steel tube that is the same size as a blood vessel. The tissue matures or grows around this tube until all the cells are fused into an "engineered" vessel.
The process takes about three months, McAllister told United Press International. After that, the steel support tube is removed and the engineered blood vessel is ready to be surgically implanted.
Researchers grafted new vessels into dogs that were then monitored for 14 days. During that time, the vessels functioned as well as native blood vessels with no clots or blockages, said McAllister.
The vessels were surgically removed and examined and again, he said, the vessels were virtually indistinguishable from healthy, native blood vessels.
Dr. Valentin Fuster, director of the cardiovascular institute at Mount Sinai Medical Center in New York City, said the new vessel-growing technology could be especially useful for persons with diabetes because they have widespread vascular disease that affects their hearts as well as circulation in their legs.
Fuster, who was not part of the study, told UPI the genetically engineered vessels also could be used by kidney dialysis patients. After repeated dialysis treatments, veins collapse and must be replaced with vein grafts.
McAllister said the first human studies will be done in dialysis patients. If successful, further studies will be conducted on patients needing bypass procedures for blocked arteries in their legs and, finally, the engineered vessels will be used in heart bypass surgery.
While McAllister's team is working to grow new blood vessels, other heart researchers reported success with injection of bone marrow cells or muscle cells into hearts damaged by heart attacks.
A heart attack scars the heart muscle, said cardiovascular surgeon Dr. Timothy Gardner, of the University of Pennsylvania in Philadelphia, who chaired a news conference on cell transplants.
Dr. Nabil Dib, director of the cardiovascular research at the Arizona Heart Institute in Phoenix, conducted a pilot study of the safety of injecting skeletal muscle cells into damaged hearts. He harvested the immature cells from the legs of 16 heart patients who underwent bypass surgery or had mechanical assistance devices implanted.
During the surgery, the cells were injected directly into the scarred area of the heart.
After 12 weeks, all the patients who received the cell transplants had improved pumping function, said Dib. The skeletal muscle cells were able to differentiate or mature into cells that mimic the work of heart muscle cells, he said.
Dr. Manuel Galinanes, of the University of Leicester in the United Kingdom, reported similar positive results with transplanted bone marrow cells that he injected into 14 patients who had heart bypass surgery.
Gardner said the research is promising -- especially since it relies on cells donated from adults rather than cells from embryos -- but he cautioned the results are preliminary. He noted some cases patients who received the cell transplants developed dangerous irregular heart beats.
