Fetal-cell transplants show few benefits.Fetal-Cell Transplants Show Few Benefits More than a year after the first transplants of human fetal tissues into the brains of adults with 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. , and only a week after the first such reported operation in the United States United States, officially United States of America, republic (2005 est. pop. 295,734,000), 3,539,227 sq mi (9,166,598 sq km), North America. The United States is the world's third largest country in population and the fourth largest country in area. , researchers concede that few of the patients show definite clinical improvement. In cases where improvement has been noted, it's difficult to show that the transplants are responsible, according to reports from scientists this week. Moreover, a flurry of apparently irreconcilable results from researchers performing similar surgeries in animals has sparked renewed uncertainty about how such transplants might work. As basic assumptions about the therapy are called into question, some investigators wonder aloud about the wisdom of pursuing more widespread human trials. "This is still a procedure that has a high morbidity, a high mortality, and patients that have Parkinson's disease do have access to good treatment by conventional means with which they can live a normal life span," says Donald M. Gash, a pioneer in monkey brain-cell transplants at the University of Rochester The University of Rochester (UR) is a private, coeducational and nonsectarian research university located in Rochester, New York. The university is one of 62 elected members of the Association of American Universities. (N.Y.). Gash spoke this week in Toronto at the 18th annual meeting of the Society for Neuroscience For other uses, see SFN (disambiguation). The Society for Neuroscience (SfN) is a professional society for basic scientists and physicians around the world whose research is focused on the study of the brain and nervous system. , where researchers working with both animals and humans presented the most detailed results yet of the experimental therapy (SN: 11/5/88, p.296). "The results have not been impressive," says Anders Bjorklund of the University of Lund, Sweden, describing two Swedish Parkinson's patients who received human fetal-cell transplants last November and December. "The implantations [in Sweden] have not had any clinical significance." Scientists have hoped that transplanted cells producing the 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). dopamine dopamine (dōp`əmēn), one of the intermediate substances in the biosynthesis of epinephrine and norepinephrine. See catecholamine. dopamine One of the catecholamines, widely distributed in the central nervous system. might make up for the dopamine deficits that cause the tremors and rigidity characteristic of Parkinson's. However, Bjorklund reports, sensitive brain scans using positron emission tomography positron emission tomography: see PET scan. positron emission tomography (PET) Imaging technique used in diagnosis and biomedical research. have "not given any evidence of a surviving, dopamine-producing graft" in either patient. In contrast, significant improvements in a few patients are reported by Ignacio Madrazo, who 14 months ago performed in Mexico the world's first reported transplant of human fetal cells into a patient, and by Juan-Jose Lopez-Lozano, who has performed five human fetal-cell transplants in Spain since late 1987. But others express skepticism about those results, with some scientists' questions verging upon accusations of exaggeration. In similarly controversial reports, Cuban researchers now describe positive results in 10 patients -- but these researchers are using their own measures of improvement rather than standard, accepted measures. Scientists now estimate human fetal-cell transplants total 30 to 40 worldwide. With no convincing demonstration that cell grafts are really surviving in humans, and no way to rule out non-graft-related mechanisms contributing to patients' recovery, scientists are counting on more animal studies to help them understand neural regeneration in the brain. For example, some intriguing studies now suggest that long-term, intact graft survival may not be required for clinical improvement. Instead, grafts may secrete secrete /se·crete/ (se-kret´) to elaborate and release a secretion. se·crete v. To generate and separate a substance from cells or bodily fluids. one or more unidentified "trophic trophic /tro·phic/ (tro´fik) (trof´ik) pertaining to nutrition. troph·ic adj. Of, relating to, or characterized by nutrition. substances" that stimulate the brain's own recovery processes. Once those processes are initiated and new cell growth begins, this research suggests, the graft can die. Such a finding could alter transplantation strategies. Among other recent findings discussed this week in Toronto: * University of Colorado University of Colorado may refer to:
* The precise location of a transplant in the brain appears to be more important than researchers had realized. * Fetal brain cells increasingly appear to have advantages over dopamine-producing cells transplanted from an adult patient's own 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 , perhaps in part because the adrenals in Parkinson's patients are often deficient in dopamine to begin with. |
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