Pig cells used for Parkinson's disease.

Mired in political and ethical controversy, fetal cell research has inched forward during the last decade. In a provocative study that may eliminate such controversy and avoid problems of supply, researchers have taken the first steps toward routinely using fetal cells from pigs, not humans.

Mounting evidence indicates that human fetal cells transplanted into the brain can replace the nerve cells ravaged by neurological illnesses such as Parkinson's disease (SN: 4/29/95, p.262). Yet investigators must struggle to obtain enough human fetal tissue to pursue their studies.

Much of the tissue derived from miscarriages and ectopic pregnancies is unsuitable (SN: 1/7/95, p.6). And even if obtaining fetal cells from induced abortions weren't an explosive issue, researchers doubt that this option can provide enough tissue to meet the demands of all potential patients.

Treating one Parkinson's patient, for example, requires tissue from five or more intact fetuses. "Getting the number of cells needed to treat the disease is very difficult," says neurosurgeon James M. Schumacher of the Lahey Hitchcock Clinic in Burlington, Mass.

"There is a real need to identify an alternative cell source," adds Jonathan H. Dinsmore, director of cell transplantation at Diacrin, a Boston biotech firm.

Both Dinsmore and Schumacher belong to a team that in April began transplanting cells from pig fetuses into the brains of Parkinson's patients. This is the first such experiment approved by the Food and Drug Administration.

"It's a bold move," says Paul R. Sanberg of the University of South Florida in Tampa, president of the American Society for Neural Transplantation.

In Boston last week, at a meeting focused on xenotransplantation--the transplanting of tissue across species--Dinsmore announced that the three patients treated so far have apparently not rejected the fetal pig cells. To prevent rejection, the patients were given a powerful drug that suppresses the immune system.

"We've done a PET scan on [the brain] of the first patient, and after 5 months it appears there's a living, dopamine-producing graft," Schumacher says. Parkinson's disease destroys brain cells that make dopamine, a neurotransmitter, producing problems with speech and motor coordination.

Though these initial studies are designed to test only the safety of the xenotransplant, researchers note that two of the three patients have improved. "Although the clinical data is preliminary, it looks promising," Dinsmore reported at the Third International Congress for Xenotransplantation.

This week, says Schumacher, he and his colleagues will begin transplanting fetal pig cells into three more patients. But instead of using an immunosuppressive drug, which can eventually leave patients vulnerable to infections and cancer, the investigators will try to prevent rejection of the cells by treating them first with antibody fragments.

These antibody fragments should mask the pig-specific proteins that stud the surface of the fetal cells (SN: 6/22/91, p.391) and give the patient's immune system time to learn to ignore the foreign cells, says Dinsmore.

Once investigators complete their trials with the Parkinson patients, they plan to move forward with a small FDA-approved trial of fetal pig cells for people with Huntington's disease, another neurological illness resulting from a loss of specific brain cells. Obtaining the proper human fetal cells to treat Huntington's is almost impossible, because the abortion procedure normally destroys the part of the fetus that makes them, notes fetal cell researcher Curt R. Freed of the University of Colorado in Denver. --