Growing new blood vessels for kidney dialysis
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California researchers have developed a technique to grow artificial blood vessels from a patient’s own skin cells, a technique that could quickly find application in kidney failure victims undergoing dialysis and that, in the longer term, could be used in coronary artery bypass surgery and other procedures. The technique has so far been tested in 10 patients and preliminary results, published Thursday in the international medical journal Lancet, suggest that the blood vessels can remain viable for long periods.
‘This technology is very very promising,’ wrote Dr. Vladimir Mironov of the Medical University of South Carolina in an editorial accompanying the report.
Kidney failure patients must have a shunt passing through their skin and connecting to their circulatory system to allow the dialysis machine to be connected for the thrice-weekly cleansings. The ideal material for such a shunt is a blood vessel taken from the patient, but only about half of all patients have a satisfactory vessel available. For the rest of the patients, the shunt is typically made from a plastic such as Gore-Tex. Such foreign materials are prone to infection and inflammation, reducing their long-term survival.
Several groups are attempting to produce artificial vessels in which the patient’s own cells are grown on a scaffolding of plastic or some other material that provides structural integrity. But such hybrid vessels can also provoke problems, although not as severe as those with all-plastic tubes.
Researchers at Cytograft Tissue Engineering in Novato, Calif., have developed a way to make blood vessels that do not rely on synthetic materials for integrity. They take skin cells from the back of the patient’s hand and extract two types of cells -- fibroblasts that provide the structural framework of the vessels and endothelial cells that provide the lining. The combined cells are grown in flat sheets in the laboratory, then formed into a tube about 6 to 8 inches long that is allowed to fuse closed. The process takes about six months.
The shunts have been tested in 10 patients in Buenos Aires and Katowice, Poland, according to Dr. Todd McAllister of Cytograft in Lancet. All the patients were older than 21 and had suffered a previous graft failure or were slated to receive a plastic implant. Three of the patients suffered a failure of the vessel during the first three months of the safety trial -- a not-unexpected result considering the high-risk profile of the patients, McAllister said. Another withdrew from the study and a fifth died of unrelated causes. The rest of the grafts survived and have functioned for as long as 20 months.
The chief drawback of the new vessels is likely to be cost, Mironov cautioned. They are expected to cost $15,000 to $20,000, compared with about $3,000 for a plastic vessel. But part of that cost could be recouped if they survive longer than plastic implants, McAllister said.
He said that the vessels might be available in the United States in as little as three years.
-- Thomas H. Maugh II