Fetal tissue: a hope for Huntington's?
A 37-year-old woman suffering from moderate to severe Huntington's symptoms showed "minor signs of improvement" after receiving transplants of fetal brain tissue into multiple sites within her brain, according to Ignacio Madrazo of the Instituto Mexicano del Seguro Social in Mexico City. One year after the operation, she has clearer speech and exhibits fewer of the involuntary, dance-like movements characteristic of Huntington's, Madrazo reported at the Society for Neuroscience's annual meeting.
Madrazo and his colleagues isolated nerve tissue from the brain of a spontaneously aborted human fetus. In contrast to mature nerves, these fetal ones still possess the ability to grow and divide. The Mexican team then surgically transplanted the fetal cells into the foremost region of the woman's caudate, a brain region that helps direct movement.
Afterward, the researchers found slight improvements in the woman's motor control, but no improvement in her memory or comprehension, activities controlled by areas of the brain that did not receive the transplant.
"This opens a new door in neural transplantation," says Madrazo, who has also
treated Parkinson's patients with fetal-tissue transplants. "There is a benefit only in those areas [receiving transplants]," he says, which suggests that the tissue grafts helped.
John Sladek is critical of Madrazo's new work. A physician at the University of Health Sciences Chicago Medical School, Sladek contends that the woman's slight improvement may result from unknown factors activated during postsurgical healing. He says the Mexican team could have eliminated this variable by injecting the fetal tissue through a needle, as was done in the Swedish Parkinson's experiments (SN: 2/3/90, p.70).
"I believe that this test was performed too soon and in the absence of the appropriate [animal] testing," argues Sladek, who has transplanted human fetal tissue into Parkinson's patients.
One such animal study was reported at the meeting by a research group led by Ole Isacson of McLean Hospital in Belmont, Mass. Together with colleagues in France, Isacson created an animal model of Huntington's by giving monkeys a drug that caused them to develop abnormal, Huntington's-like movements. The researchers drastically reduced these symptoms in five animals with grafts of nerve cells harvested from a fetal rat's striatum. In Huntington's patients, this brain region secretes reduced levels of a key neurotransmitter. And when the monkeys were taken off the immunosuppressant drugs that prevented them from rejecting the rat-striatum transplants, their symptoms returned.
"This study shows the potential of the neurotransplantation approach to Huntington's disease" and suggests how the use of human fetal cells can be avoided by using other animal cells, Isacson says.
Patrick Aebischer of Brown University in Providence, R.I., also reported on animal tests involving transplants between species. Prior to transplantation, he coated the fetal tissue to be grafted with a permeable plastic film. This coating shielded the tissue grafts from rejection by the recipient's immune system, while allowing the transplanted cells to secrete beneficial neurotransmitters.
Aebicher's team elicited Parkinson's-like tremors in rats with a drug that destroys the brain's ability to produce the neurotransmitter dopamine. When the researchers transplanted coated clumps of laboratory-grown nerve cells that produced dopamine into the brain of these rats, the rodent's tremors diminished -- a finding that Aebischer attributes to the grafted cells' dopamine production. Moreover, when the transplanted cells were removed, the tremors returned, he reports.
Aebischer says he and his colleagues also used a plastic coating to successfully transplant dopamine-producing cells from the adrenal glands of cows to rats with Parkinson's symptoms. "We can now transplant neural tissue across species without the danger of rejection," he says.
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|Date:||Nov 16, 1991|
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