For the first time, doctors have repaired brain damage in patients by implanting brain tissue from aborted fetuses.
Experts say the findings offer the first unequivocal evidence that implanted fetal cells can make crucial brain chemicals in place of brain cells that have died.
Though the technique has been tested in only a few patients, the experts said it could eventually lead to treatments for degenerative brain diseases, including Parkinson's disease, Alzheimer's disease and Huntington's disease.
Until now, fetal cell implants have had modest effects at best, and some experts questioned whether it was worth continuing the research. But the results reported today, in two patients treated in Sweden and others treated in the United States, suggest that the method can fulfill the almost excessive promise it long has held.
The findings, reported in today's issue of the New England Journal of Medicine, involve patients with Parkinson's disease or a similar condition.
The Swedish study, by Dr. Hakan Widner of the University of Lund and his colleagues, involved two Americans, George Carillo, 52, and Juanita Lopez, 40.
They became complete invalids in 1982, when tainted synthetic heroin damaged the areas in their brains that are also affected in Parkinson's disease, a movement disorder caused by brain cell death.
Now, the researchers reported, the patients can live independently and move almost normally; Mr. Carillo even rode a bicycle. Brain scans showed that the fetal cells were producing chemicals that the patients' brains had lacked, the researchers said.
Although the number of patients was small, the improvements were completely consistent with what had occurred in animal studies and were so marked that experts felt they could never have occurred by chance.
Especially in the cases of Mr. Carillo and Ms. Lopez, so many brain cells were lost that it was inconceivable that they could ever have any semblance of a normal life with conventional treatments. "They had been sick for seven years and we had tried every procedure in the book," Dr. Widner said.
The U.S. research groups, led by Dr. D. Eugene Redmond Jr. of Yale University and Dr. Curt R. Freed of the University of Colorado, implanted fetal tissue into 10 patients with Parkinson's disease.
They reported small, but definite, effects. Patients did better in tests such as touching their thumbs to their forefingers and tapping their feet, for example. They were less likely to freeze, unable to move, and had smoother movements in general.
But the methods used by Dr. Redmond and Dr. Freed differed from those of Dr. Widner. With one exception, the U.S. researchers used just one fetus per patient, for example; Dr. Widner and his colleagues used as many as seven. Dr. Widner also implanted the tissue into a larger area of the brain. Experts said these methodological changes could account for the different results.
The U.S. results are promising, experts said, but they were even more heartened by the Swedish results.
"It's spectacular," said Dr. C. Warren Olanow, a neurologist at the University of South Florida and a leader in fetal tissue work. "The results are terrific. It's an order of magnitude greater improvement than anything we've seen."
Dr. Widner said that he and his colleagues recently used the same method with two patients who have Parkinson's disease. "The effects are about as large" as in the patients he reported today, he said.
But Dr. Widner cautioned that much work remains to be done before fetal cell implants move beyond experiment and become therapy. For example, he said, "we need to boost the survival rate of transplanted tissue."
To obtain enough tissue, he said, multiple abortions must be scheduled for within hours of the five-hour fetal implant operation. The scientists need tissue from multiple fetuses because only 10 percent of the implanted fetal cells survive.
Because the federal government will not finance research involving fetal tissue, the work in the United States was supported with private money. President-elect Bill Clinton has said he intends to lift the financing ban.