NEW YORK, Mar 13 (Reuters Health) -- Transplantation of small amounts of
embryonic pig tissue into the areas of the brain affected by Parkinson's disease
(PD) appears to be safe and to offer hope for patients who no longer respond to
medication, researchers report.
Twelve patients were given transplants of pig tissue into one side of their
brain when medication failed to control their advanced symptoms, according to a
report in the March 14th issue of Neurology. None of the patients experienced
serious side effects related to the surgery.
Whereas transplantation of tissue from human embryos has improved the
symptoms of some patients with Parkinson's, limited availability of such tissue
and ethical concerns have prevented widespread use of the procedure. More widely
available is neurological cells from pig embryos, which can produce dopamine,
the neurotransmitter lacking in patients with Parkinson's, according to Dr. J.M.
Schumacher from Lahey Medical Center in Burlington, Massachusetts, and
colleagues.
One concern about animal-to-human transplants is the possible transmission
of bacteria or viruses along with the tissue. A battery of tests suggested that
no microbial contaminants were present in the tissue.
The patients improved an average of 19% in the year after implantation, the
researchers note, although the responses were quite variable among the 10
patients who could be tested thoroughly.
PET scans (which measure the activity in the brain area affected in
Parkinson's and usually show increases with successful transplants) showed no
significant changes 12 months after surgery. In contrast, autopsy specimens from
one patient showed apparent integration of the pig tissue within the surrounding
brain, suggesting that the implanted tissue had survived.
The authors conclude that pig embryonic tissue can safely be transplanted
into the brains of people affected with Parkinson's, but that larger amounts of
tissue may be required for more consistently beneficial effects.
"Clinical trials in which a larger number of (pig brain) cells are implanted
(into both sides of the brain) will be necessary to assess clinical benefit and
safety more fully," the investigators conclude.
