Page last updated at 10:17 GMT, Monday, 21 July 2008 11:17 UK

Animal tissue rejection advance

There are long waits for many transplant operations

Scientists have found a way to overcome the problem of the human body rejecting animal parts used in transplants.

The work, by the University of Leeds, means the use of animal tissue such as blood vessels, tendons and bladders may become common in surgery.

Human organs for transplant are constantly in short supply, meaning long waits for many patients.

Currently, the use of animal tissue for human transplant is restricted, and of limited effectiveness.

If we have a means of stripping away the first, and most major cause of rejection that is certainly something that requires further investigation
Mr John Forsythe
Edinburgh Royal Infirmary

For instance, chemically treated heart valves from pigs have been transplanted into patients for more than a decade, but have a limited life span as they are inert and cannot be populated by the patient's own cells, and ruling out any possibility of repair to damage.

This poses a particular problem for young patients, as the valves do not grow with the child, and must be replaced frequently.

The Leeds team used a combination of freezing, chemical baths and ultrasound to strip the animal tissue of the cells and biological molecules that trigger a response from the immune system.

This left a biological scaffold which could then be populated by cells from a patient's own body, creating a tissue which carries no risk of rejection, which can be repaired, and which can grow with the body.

So far tests have only been carried out on animals, but researcher Professor John Fisher said it was hoped to begin clinical trials on humans next year.

Better alternative

Professor Fisher said: "We are talking about relatively simple tissues, such as blood vessels, heart valves, ligaments, tendons, surgical patches for internal repair.

"At the present time the surgeon has only got two choices, either sacrifice some tissue from somewhere else in the patient's body, or wait for a donor tissue from another human being, and clearly they are in short supply.

"This is a very attractive alternative, because it can be available off the shelf for the surgeon to use."

The scientists have formed a company, Tissue Regenix, and are working to develop the technique so they can create new heart valves for children.

However, transplant expert John Forsythe, based at the Edinburgh Royal Infirmary, said much work was needed before the use of animal parts was routine in transplant surgery.

He said it was possible that the biological scaffold left behind after cells had been stripped away could still provoke a longer-term immune reaction, as it would still be different to that found in humans.

In addition, using tissue which was not inert carried a potential risk of infection.

However, he added: "If we have a means of stripping away the first, and most major cause of rejection that is certainly something that requires further investigation."


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