Fetal tissue: a hope for Huntington's?
Four years ago, Swedish researchers pioneered a controversial treatment for Parkinson's disease Parkinson's disease or Parkinsonism, degenerative brain disorder first described by the English surgeon James Parkinson in 1817. When there is no known cause, the disease usually appears after age 40 and is referred to as Parkinson's disease. that involved transplants of brain tissue from aborted human fetuses. At a meeting in New Orleans this week, Mexican scientists reported adapting the same therapeutic technique to ameliorate symptoms in a patient with Huntington's disease Huntington's disease, hereditary, acute disturbance of the central nervous system usually beginning in middle age and characterized by involuntary muscular movements and progressive intellectual deterioration; formerly called Huntington's chorea. , another disabling genetic disorder affecting the brain. At the same meeting, two other researchers reported encouraging results from animal studies aimed at developing fetal-transplant techniques that do not rely on human tissue.
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 nerve tissue
A highly differentiated tissue composed of nerve cells, nerve fibers, dendrites, and neuroglia. 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 caudate /cau·date/ (kaw´dat) having a tail.
having a tail. , 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 The Chicago Medical School is the medical school of the Rosalind Franklin University of Medicine and Science. Founded in 1912, the Chicago Medical School has a nearly 100 year history of a broadly-based socially constructive admission process relatively unlike that of other , 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 striatum /stri·a·tum/ (stri-a´tum) corpus striatum.stria´tal
n. pl. stri·a·ta . In Huntington's patients, this brain region secretes reduced levels of a key neurotransmitter neurotransmitter, chemical that transmits information across the junction (synapse) that separates one nerve cell (neuron) from another nerve cell or a muscle. Neurotransmitters are stored in the nerve cell's bulbous end (axon). . And when the monkeys were taken off the immunosuppressant drugs Immunosuppressant Drugs Definition
Immunosuppressant drugs, also called anti-rejection drugs, are used to prevent the body from rejecting a transplanted organ. 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 immune system
Cells, cell products, organs, and structures of the body involved in the detection and destruction of foreign invaders, such as bacteria, viruses, and cancer cells. Immunity is based on the system's ability to launch a defense against such invaders. , while allowing the transplanted cells to secrete secrete /se·crete/ (se-kret´) to elaborate and release a secretion.
To generate and separate a substance from cells or bodily fluids. 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 dopamine (dōp`əmēn), one of the intermediate substances in the biosynthesis of epinephrine and norepinephrine. See catecholamine.
One of the catecholamines, widely distributed in the central nervous system. . 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 Adrenal glands
The two glands that are located on top of the kidneys. These glands secrete several hormones, including the glucocorticoids which, among other things, influence the way the immune system works, and the mineralocorticoids, which affect retention of of cows to rats with Parkinson's symptoms. "We can now transplant neural tissue across species without the danger of rejection," he says.