Blood vessels that are available off the shelf are looking more feasible since the announcement this week that vessels grown in the lab from donor skin cells were successfully implanted into kidney dialysis patients in a small clinical trial. Such "allogeneic tissue-engineered vascular grafts" have the potential to make kidney dialysis and other procedures, such as repairing diseased arteries and heart defects, more cost-effective.

The American Heart Association's Emerging Science Series 27 June 2011 webinar was the forum for the announcement, where study lead author Dr Todd N. McAllister, co-founder and chief executive officer of Cytograft Tissue Engineering Inc, of Novato, California, presented the results of the first study to test the feasibility of grafting blood vessels grown in the lab from donor cells into living human patients.

McAllister told his on-line audience that while more tests are needed, the availability of "off-the-shelf" blood vessels came a step closer. Such grafts could improve the process and affordability of kidney dialysis and other procedures:

"Our approach could allow hundreds of thousands of patients to be treated from one master cell line," said McAllister.

Such affordable and effective blood vessels could for example help children with congenital heart defects, and patients with diseased arteries in their legs (where tissue-engineered vessels could be implanted to bypass the blood flow around the defective vessel). They could also help soldiers who might otherwise lose a limb, said McAllister.

Kidney dialysis is a treatment for patients with kidney failure. The kidneys remove waste from the body, effectively by filtering it from the blood, and they help maintain blood pressure and safe levels of chemicals like sodium and potassium.

Patients with kidney failure can't do this for themselves and have to undergo regular dialysis, sometimes several times a week, to keep their blood "clean" and their blood pressure and essential blood chemicals at safe levels.

A common type of dialysis is hemodialysis where, via a needle inserted in a vein, the dialysis machine removes some blood, "cleans" it, and then puts it back into the body via a needle inserted into an artery.

Unfortunately, a side complication of the treatment is the "wear and tear" on the veins and arteries accessed by the dialysis needles.

One option around this is to implant access shunts, either from patients' own vessels or from synthetic materials, but these are prone to failure, said McAllister.

In this trial, he and his colleagues, including members from Poland and Argentina, grew sheets of cultured cells from donor skin cells around temporary support structures to make the tubular shape of blood vessels they could use as grafts.

They then implanted the grafts, which were 30 cm long and 4.8 mm in diameter, into the arms of three kidney dialysis patients as shunts to provide the dialysis machine access to a vein and an artery.

They monitored the patients for eight months after the transplant. After this time, none of the patients had developed an immune reaction to the grafts, and the implanted vessels were able to stand the high pressure and frequent needle punctures of regular dialysis sessions.

In a previous trial, the researchers showed that it was possible to reduce shunt complications 2.4-fold over 3 years by growing vessels from the patient's own skin cells.

However, if similar results could be achieved with "off-the-shelf" vessels this would make the procedure significantly more affordable and also avoid the need to wait for months while the customized vessels grew.

The off-the-shelf grafts are now being tested in a larger randomized trial with kidney dialysis patients, and trials to test their safety and effectiveness in lower-limb bypasses in humans are also under way.

Kidney failure is one of the most costly diseases to treat in the industrialized world. The US spends more than $27 billion a year in caring for 400,000 dialysis patients, and about 15% of this is spent on creating and maintaining access shunts, said the researchers.

Cytograft funded the study, and as well as McAllister, some of the other team members work in the company.

"First Human Use of an Allogeneic Tissue Engineered Vascular Graft."
Todd N. McAllister, Wojciech Wystrychowski, Lech Cierpka, Krzysztof Zagalski, Sergio A. Garrido, Samuel Radochonski, Nathalie Dusserre, and Nicolas L'Heureux.
Abstracts From the Emerging Science Series, June 27, 2011 (automatic PDF download)
Circulation, Published Ahead of Print.

Additional source: AHA.

: Catharine Paddock, PhD

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