In the first U.S. operation of its kind, Vanderbilt University surgeons Thursday implanted adrenal gland cells into the brain of a 42-year-old woman suffering from Parkinson's disease.
During a five-hour operation in Nashville, Tenn., the surgeons removed one of the two walnut-sized adrenal glands from its normal location above the kidney, minced it into small pieces, and injected the pieces deep into the right caudate nucleus of Dickye Baggett.
Baggett, who has had the disease for 10 years, was described as resting comfortably after the surgery.
Similar transplants of adrenal cells have previously been attempted in 15 other human patients, four at the Karolinska Institutet in Stockholm, Sweden, and 11 at Centro Medico La Raza in Mexico City. The transplants in Sweden produced only modest and transient improvements in the four patients' symptoms, whereas those in Mexico City suggest significant and long-lasting improvement.
Parkinson's disease, which afflicts as many as 1.5 million Americans, most of them over the age of 50, is characterized by severe tremors and rigidity of the limbs. About 30% of the victims also suffer dementia, an impairment of mental functions.
Its cause is unknown, but victims exhibit a deficiency of the hormone dopamine, which participates in the transmission of messages between brain cells.
Parkinson's symptoms can be controlled in the early stages with a drug called L-dopa, which replaces the dopamine in the brain. Most Parkinson's patients eventually develop a tolerance for the drug, however, so that larger and larger amounts are required before it finally becomes ineffective.
The adrenal glands also secrete dopamine, but that dopamine is prevented from reaching the brain by the blood-brain barrier, which shields the delicate brain cells from large molecules and foreign organisms while allowing nutrients to enter.
By transplanting the adrenal tissues into the brain, scientists hope to bypass the barrier and allow the dopamine to reach brain cells directly. The technique has been studied extensively in rats and mice, but in only a few primates.
Many scientists had argued for testing in a much larger number of primates before human trials were attempted in this country. "I think they are jumping in somewhat prematurely," said neurobiologist Curt Freed of the University of Colorado Medical Center.
Freed expressed surprise that the Vanderbilt scientists used the same procedure as the Swedes, in which the cells are implanted deep within the caudate nucleus of the brain. At that site, the implanted cells receive few nutrients, and most scientists believe that they die within weeks, accounting for the poor results obtained in Sweden.
The Mexican researchers, in contrast, implanted the cells in a naturally occurring cavity in the brain where the cells are bathed in nutrients and, most importantly, a nerve growth factor that stimulates growth. Their first patient, who received the implant 14 months ago, is still improving, indicating that the implanted cells are thriving.