Cell grafts proceed, value uncertain.

Cell grafts proceed, value uncertain

While scientists and public officials continue to debate the ethics of experimenting with human fetal cells, the first transplants of such cells into adults with Parkinson's disease are being performed. Earlier this month, with very little fanfare, Sweden became the first country to officially acknowledge performing such experiments. But the controversial procedure has probably been attempted in as many as four countries in the past two months, according to researchers.

The procedure involves the grafting of fetal brain cells onto the brains of Parkinson patients, who suffer tremors and neuromuscular rigidity because of a lack of the neurotransmitter dopamine.

The Swedish experiments are the culmination of a series of animal and human studies that have hinted at the usefulness of such transplants. There is some debate among scientists, however, as to whether the most recent human trials may be premature. Indeed, recent findings reported in New Orleans at last week's annual meeting of the Society for Neuroscience call into question some of the results of earlier, more promising cell transplant experiments that did not involve transplanting human fetal cells into humans.

"The initial enthusiasm generated only a year ago has waned significantly,' says Fred Gage, a neuroscientist at the University of California at San Diego. "Everyone thought we were seeing a little something,' Gage says of the early transplant experiments. "Well, it was a little something --very little something.'

Those experiments included transplants of dopamine-producing cells onto the brains of animals in which researchers had induced Parkinson-like symptoms with the chemical MPTP, and transplants of adult human adrenal cells onto the brains of patients with Parkinson's disease. Some subjects showed signs of neuromuscular improvement, and it was postulated that dopamine-producing human fetal cells would be more effective (SN: 7/11/87, p.22).

More recent research, however, suggests that much of the initial evidence of improvement in both animals and humans may have been overstated or misinterpreted. For example, there is a surprisingly high rate of spontaneous behavioral recovery among animals that have had Parkinson-like symptoms induced by MPTP. Thus it is now suspected that many test animals would have recovered even without the cell grafts.

Other studies call into question some of the microscopic evidence of nerve cell regrowth seen in the brains of animals receiving grafts. One disturbing bit of research, presented at the meeting by National Institutes of Health scientists, showed that it's possible to induce new sprouting of dopamine-producing cells in monkeys by transplanting any one of a number of tissues--even non-dopamine-producing tissues--into their brains.

Such sprouts, believed until now to be emanating from transplanted tissue, may in fact be outgrowths of dopamine-producing cells that survived the initial exposure to MPTP. The researchers hypothesize that these cells may have been stimulated to grow by some aspect of the brain surgery itself.

Not all the latest research is disappointing. Promising primate and rodent studies, including several experiments by researchers at the University of Rochester (N.Y.) and at the University of Colorado Health Sciences Center in Denver, were reported in New Orleans. Nevertheless, some researchers expressed surprise that human clinical trials were already proceeding in Sweden, and that human trials have likely been done in Mexico, China and possibly Cuba. Several neuroscientists at the meeting noted that U.S. scientists remain split on the ethics of using human fetal tissue for experimental purposes, and that resolution of the issue will likely await the outcome of experiments in other countries.