Blood Vessels Grown From Donated Cells Closer to Reality
3 Patients Have Received Engineered Vessels; No Signs of Rejection
June 27, 2011 -- For the first time, blood vessels grown from donor cells have been successfully implanted in human patients, an early report of new research shows.
The tissue-engineered vascular grafts, which were grown from donated skin cells, were implanted in the arms of three patients in Poland to create shunts, or access points, for kidney dialysis.
Though the oldest graft was implanted just eight months ago, none of the patients has shown signs of rejection, and none requires medication to suppress immune function, says Todd N. McAllister, PhD, co-founder and chief executive officer of Cytograft Tissue Engineering Inc. of Novato, Calif., the company that sponsored the study.
Previously, researchers have used cells taken from individual patients to grow tubes of tissue that can be grafted onto natural blood vessels. But that process takes months and is expensive. Each graft costs between $10,000 and $20,000.
The new vessels can be made in advance and refrigerated until doctors are ready to use them, and they could cost less, around $6,000, McAllister estimates.
Researchers acknowledge that their data are preliminary. But thus far, patients who have gotten the engineered grafts have had fewer complications than they had experienced with previous shunts, which are typically built from a person's own tissue or from a chemical polymer.
The research was presented during the American Heart Association's Emerging Science Series, an online presentation of new research.
"This is tremendously exciting," says Robert A. Harrington, MD, director of the Duke Clinical Research Institute in Durham, N.C., in remarks made during a news briefing. "If the work as has been demonstrated thus far continues in such a positive way, this is big news."
How the Grafts Are Made
To make the grafts, McAllister says they start with a scrap of donated skin about the size of a postage stamp. The cells are grown under conditions that encourage the production of collagen until a sheet of tissue forms. The tissue sheet is then wrapped several times around temporary support and placed in a bioreactor where its layers fuse and form a tube. The tube is dried and refrigerated until it's needed.
So far, the longest a vessel has been refrigerated before being implanted in a patient has been two months. But McAllister says that mechanical testing and animal studies suggest that the bioengineered tubes could sit in a refrigerator for up to a year and still be vital.
Just three patients have gotten the new grafts. McAllister says his company plans to try the tissue tubes in as many as 40 patients over the next 12 to 18 months. The company hopes to present its technology for FDA approval within two years.
In addition to helping to make shunts for kidney dialysis patients, researchers said the grafts could be refined and used to help people who need vessels to bypass blockages around their hearts or to help save the limbs of people who have blocked arteries in their legs due to peripheral artery disease.
"There are literally hundreds of thousands of patients that could use this technology," McAllister says.
These findings should be considered preliminary as they have not yet undergone the "peer review" process, in which outside experts scrutinize the data prior to publication in a medical journal.