07-20-2008, 06:55 AM
Join Date: Jul 2008
Location: Out of sight
Breakthrough Over Animal Spare Parts for Humans
This is groundbreaking if these scientists really have overcome the problem of animal tissue rejection. Most transplant patients have lower life expectancy due to the use of immune suppressing drugs and consequently are unable to fight cancer and infections.
Breakthrough in animal spare part transplants for humans
By Richard Gray, Science Correspondent
Last Updated: 12:01am BST 20/07/2008
Blood vessels, tendons and bladders from animals are to be used in humans for the first time after a breakthrough in transplant surgery.
Scientists have overcome the problem of rejection, which has previously prevented animal tissues from being used in patients.
It opens the way for a range of new procedures using animal parts.
Children could be given pigs' heart valves that can grow with them, avoiding the need for repeated surgery; tissues such as ligaments, which have previously been difficult or impossible to repair, could be replaced; and eye patients could even be provided with new corneas.
By stripping the animal tissue of its cells with a series of chemical treatments, the scientists were left with a biological scaffold that provides a structure but no longer carries the factors that can trigger a recipient's body to reject a transplant. When the scaffold is surgically inserted into the patient's body, his or her own cells grow into it to create new tissue.
Because the patient's own cells fill the scaffold to create the tissue, scientists say there are no problems with rejection and the tissues are also able to regenerate, allowing them to last longer.
Professor John Fisher, a biological engineer at Leeds University who was one of the scientists behind the research, said they hoped to begin clinical trials on humans next year. He said that preclinical trials in animals had already been successful.
He added: "The problem that surgeons have always faced with transplanted tissues is the risk of rejection by the patient's body. All tissues carry messages on their surfaces that identify them as foreign to a patient's body when they are transplanted and this causes the immune system to attack them.
"We can take a tissue from an animal, remove all the cells that carry the signals that trigger the immune system so just the biological scaffold is left. When this is implanted, the patient's own cells then grow in to replace the original cells we have removed. This has advantages as the transplant can then grow with the patient - something that is very important in younger patients."
The scientists, who have formed a company, Tissue, are also working with the NHS Blood and Transplant Service to develop the technique so they can create new heart valves for children.
Surgeons have been able to transplant heart valves from pigs into patients for more than a decade, but these have a limited life span as they do not become populated by the patients own cells and are unable to repair any damage, meaning they must be replaced every 10 years.
For young patients this poses a particular problem as the valves do not grow with the child and so must be replaced frequently.
With the new technique the heart valves grow with the patient as if they were part of the original heart. The scientists use a combination of freezing, chemical baths and ultrasound to strip the animal tissue of its cells and prime the remaining biological scaffold so the patient's cells are encouraged to grow into it.
Scientists have already demonstrated the technique with blood vessels and heart valves and are developing transplants that can replace damaged ligaments, tendons, cartilage and bladders.
Professor Fisher said they were unable to use the method on complex organs such as kidneys and full-grown hearts, but American researchers recently used similar techniques to regrow hearts in rats.