* Graft contains no foreign material
* Helps patients grow-their-own vein transplants
CHICAGO, April 23 (Reuters) - The first vein grafts made entirely of a patient's own cells showed promise in a long-term study of 10 seriously ill kidney dialysis patients, U.S. researchers said on Thursday.
The tissue-engineered grafts were grown over a period of six months and tested in patients undergoing kidney dialysis.
"We had extremely good long-term performance," said Dr. Todd McAllister, chief executive of Cytograft Tissue Engineering of California, whose study appears in the Lancet.
Many dialysis patients have their blood filtered through a plastic tube or access graft, but these have a higher failure rate. Grafts made from a segment of a person's own vein typically work better, but many patients do not have a suitable vein segment that can be used to make a graft.
McAllister's company offers a new option. It is part of a new field called regenerative medicine in which tailor-made transplants of tissues and perhaps organs can be grown from a patient's own cells.
"What we have done is provide something that has no foreign material, therefore minimizing or eliminating the foreign body (rejection) response so the body doesn't degrade the tissue," McAllister said in a telephone interview.
He said other labs are developing vein grafts using cells from a person's own tissue, but most incorporate some sort of plastic scaffolding to give the vein strength. "The fact that there is no synthetic material makes this novel," he said.
To make the graft, the company takes tissue from the back of a patient's hand and extracts two cell types -- fibroblasts from the skin which provide the structural backbone of the vein, and endothelial cells to form the lining of the vein.
SHEETS OF CELLS
McAllister said the researchers use growth factors to grow the cells into a sheet that can be used to build complex, 3-D designs. "This is the basic building block," he said.
They wind the sheet into a tube and allow the cells to fuse at the seam. The whole process takes about six months.
McAllister said the company hopes to make replacement veins for a range of conditions including patients with diseased veins who would otherwise need an amputation.
Kidney dialysis patients were chosen first because they make frequent visits to doctors and they could be closely watched.
For their study, they implanted 10 patients from centers in Buenos Aires, Argentina and Katowice, Poland, between 2004 and 2007.
They started dialysis and checked the grafts for strength and stability during an initial three-month safety phase. Three of the grafts failed, which McAllister said is about the rate expected in this high-risk group of patients.
One patient dropped out because of severe stomach bleeding, and one died of unrelated causes. The five remaining patients were followed for six to 20 months, and only one patient needed surgical correction to keep the graft open.
McAllister said the company wants to study the graft in a much larger trial to make sure it works and hopes to have a product on the U.S. market in about three years.
Growing replacement veins would not be cheap. McAllister said it would initially cost $10,000 to $15,000 more than a conventional $3,000 product made using plastic. But because it has less risk for rejection, it might last longer, he said. (Editing by Maggie Fox and Eric Walsh)
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