The testicle cells protect brain-cell transplants from immune system rejection, and secrete vital factors that stimulate the recovery of damaged brain tissue normally beyond repair.
Damaged nerves in the brain and spinal cord are notorious for not repairing themselves - unlike other tissues of the body - which makes it difficult to treat neurological diseases such as Alzheimer's and Parkinson's, and physical injuries to the spine. But researchers led by Paul Sanberg of the University of South Florida found that testicle cells taken from pigs can stimulate the growth and partial repair of the damaged brains of rats.
Professor Sanberg told the American Association for the Advancement of Science in Los Angeles that he will apply to the American Food and Drug Administration to begin human trials within two years.
The Sertoli cells of the testes are known as "nurse cells" because they guard the developing sperm against attack by the body's immune defences and bathe them in growth factors. Professor Sanberg believes they could serve a similar role in the brain to help transplanted nerve tissue to grow.
Several attempts have been made to transplant embryonic nerve tissue from aborted foetuses into the brains of patients with degenerative nerve disease, but the work is dogged by tissue rejection - only about 5 per cent of the cells survive for any length of time.
Adding Sertoli cells to foetal-tissue transplants will improve efficiency and make recovery more likely, Professor Sanberg believes. "Because Sertoli cells have these mechanisms for protecting against the immune system, you can get survival of cross-species Sertoli cells," he said.
"We've shown that when pig Sertoli cells are transferred into the rat's brain, and with no drugs to protect those cells, they will survive for months. Perhaps these Sertoli cells could survive cross-species transfer into the human brain."
Human Sertoli cells could not be used because they could come only from a pre-pubescent male, and such ethical approval is unlikely.
Several similar research projects are under way. Last year scientists transferred the nerve cells from a tumour into a woman who had suffered stroke-induced brain damage.
At the University of California in San Diego, Mark Tuszynski, a neuroscientist, intends to use genetically engineered tissue in a damaged brain to treat incurable neurological disorders. Animal experiments have been successful, he said.
"The technique delivers a variety of growth factors and can restore function, which is the holy grail of spinal cord injury and neuroscience in general," said Dr Tuszynski.
Evan Snyder, assistant professor of neurology at Harvard Medical School in Boston, is using human "stem" cells from the nerve tissue of an aborted foetus. Experiments on rats showed the cells appear to restore some of the function of a damaged brain.
He told the conference: "If we had unlimited resources we could maybe get into human trials within two years."Reuse content