Oct 21 1998
UPI Science News
NEW HAVEN, Conn., October 21 (UPI) -- Genetically engineered pigs may one day help paralyzed people walk again, say scientists.
The research is in its very early stage, but the pig cells could be tested on humans with spinal cord injuries in as little as two years, says Dr. Leonard Bell, presdient and CEO of Alexion Pharmaceuticals, Inc., the small biotechnology company developing the technique.
The New Haven, Ct.-based firm just got a vote of confidence from the U.S. government, in the form of a $2 million three-year grant to create pigs that could donate spinal tissues to people who have been paralyzed. The funding comes from the Advanced Technology Program of the National Institute of Standards and Technology.
The pigs will be genetically engineered to prevent the body from destroying the new tissues immediately in a process called hyperacute rejection. Alexion has a broad program to develop these pigs, mainly targeting organs like hearts and kidneys. But Bell says the genetic engineering should work the same with nerve and other cells as well.
No scientific papers have been published on the research, which has been underway for about a year. Until the work is published, which Bell anticipates in about six months, the company will be close-mouthed about many of the details of the experiment.
Bell tells UPI, however, that early stage studies on the spinal transplants -- in which rodents received gene-altered cells from pigs -- have been promising, showing some recovery of function in the treated animals.
Bell says, ''We've seen occasional episodes where the nerve impulse travels normally. The next step, he says, is to test the approach in monkeys.''
Bell says the aim of the research will be to repair a layer of cells that cover the nerve fibers of the spine. This layer, known as the myelin sheath, helps conduct electrical impulses through the spinal column, in much the same way that insulation helps an electrical wire conduct current.
Strip away the insulation and the wire will no longer conduct electricity, Bell says. In many spinal cord injuries, he points out, nerves themselves are not severed, but the myelin sheath -- the all- important insulation -- has been damaged.
This is where the pig cells may help most, filling in the gaps with a variety of cells that can nourish the cells of the myelin sheath.
He says, ''We're laying down the foundation for myelin.''
Alexion researchers experimented with animals that had either damaged or severed spinal cords.
Bell says there were some signs that the technique may help nerve cells regenerate.
But, Bell acknowledges there are a certain amount of unknowns.
Questions and controversies surround both spinal regeneration and xenotransplantation -- two scientific fields in their infancy -- and then there's always the question of whether encouraging results in animals will ever lead to cures in humans, he says.
Dr. Naomi Kleitman of the Miami Project to Cure Paralysis says that using genetically engineered cells in spinal cord injury is very promising technology.
But she adds, ''We don't know exactly how these technologies will be applied. We don't know if xenografts will be needed. She says other scientists have been experimenting with the use of pig tissues in another central nervous system disorder, Parkinsons disease.
At the Miami Project, scientists led by Dr. Mary Bartlett Bunge have been using cells found in peripheral nerves, such as those in arms and legs, and transplanting them to the injured spine.
The scientists hope these transplanted cells, known as Schwann cells, will help nerves regenerate and bridge the communication gap between the brain and the paralyzed parts of the body.
They are also investigating the use of other cells, such as nerves that carry scent sensations from nose to brain, in reconnecting the damaged spinal cords.
Kleitman says that repairing spinal cords will probably require combinations of approaches, including genetically engineered cells, proteins, drugs and tissues transplanted from peripheral nerves
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