Cells from pigs' testes may soon undergo human trials for the treatment of Parkinson's and Alzheimer's diseases, according to a leading researcher in neural transplantation.
"Our research goal is to look for ways to repair the brain," explained Dr Paul Sanberg, professor of neuro-sciences at the University of South Florida. Dr Sanberg and researchers at the University of Pittsburgh last year announced that cells from a human tumour of the testicles had helped to reduce stroke damage in several patients.
Trials involving a range of approaches are under way, he said, including the use of foetal cells and animal cells, to treat some important brain diseases. The work could be applicable to spinal and nerve injuries and other neurological disorders.
In a session on cell transplants as a way to repair the brain and nerves, he said "the field is fairly young", but rapid developments in microbiology and genetics had helped to speed up research.
Dr Evan Snyder of Harvard Medical School and Children's Hospital, Boston, described his work on the use of cloned human neural stem cells to repair damage, likening it to the repair of a damaged lawn. Stem cells are an elemental type of cell that can grow into many different cell types and neural stem cells are linked to the brain.
"If you think of stem cells as the seeds of the brain, then the way to approach fixing a broken brain is to re-seed it like a lawn," he said. Parkinson's or Alzheimer's patients would receive a transplant of cultured stem cells that would halt progression of the disease. The concept is based on many years of successful work using mouse models to show that stem cells had a therapeutic potential if transplanted into the brain.
Dr Snyder and his group used cells taken from the brain of a dead human foetus several years ago and then cloned them to sustain the cell line. These were grafted into a mouse with a specific brain disorder. The human cells integrated into the surrounding brain tissue and restored the damaged area, he said, although it was not yet clear if the new brain tissue would operate as normal.
The goal would be to produce a "universal donor cell", a continuous line of cells so there would be fewer ethical concerns about the source of transplant tissues.
Dr Sanberg described his work using sertoli cells from rat testes which were implanted into the brains of rats. Also known as nurse cells, these protect sperm from the immune system and pass nutrients and oxygen to them.
They also produce a number of growth factors. It was found that they retained these properties when transplanted into the brain, so the animal's immune system did not destroy them.
The researchers found that when embryonic rat neurons were then added to the sertoli cells, these nerve tissues survived longer and grew in the rat's brain tissue. The growth factors seemed to enhance the work done by the undamaged brain cells, Dr Sanberg said.
They have a human cell line originally taken 20 years ago from a testicular tumour and these could be used, he said, but sertoli cells derived from pig testes held out more promise. Large amounts of the tissue would be needed for clinical use and it was easy to get these cells from pigs.
Virus-free pig lines were available, but once transplanted the pig sertoli cells produced similar growth factors and resisted rejection like the human equivalent. He predicted that the technique could go into human trials in as little as two years.
His results suggested that sertoli cells could help re-grow the neural connections to the brain lost in Parkinson's, or keep the remaining cells alive and well.