An experimental gene therapy holds promise for preventing a potentially fatal complication that often happens after a blood vessel in the brain ruptures, new research suggests.

Subarachnoid hemorrhage is a type of stroke that occurs when a brain aneurysm--a weak spot in a blood vessel--bursts. To treat the stroke, a surgeon usually clips and removes the aneurysm. About 30% to 40% of the time, however, patients develop a constriction of brain arteries, which can cause another stroke to occur later.

Earlier research has shown that a molecule called calcitonin gene-related peptide (CGRP) can counteract the constriction of blood vessels that occurs during a subarachnoid hemorrhage. So a team of researchers led by Dr. Donald D. Heistad, of the University of Iowa in Iowa City, conducted a study of the substance in rabbits.

Writing in the October 27th issue of Circulation Research: Journal of the American Heart Association, the researchers report that the approach appears to work.

After mice were injected with a harmless virus containing the CGRP gene, constriction of blood vessels after subarachnoid hemorrhage was blocked, according to the report. And the treatment worked without triggering the dangerous drops in blood pressure that occurred in earlier human studies of CGRP.

"Our ultimate goal using this gene therapy is to be able to administer the (CGRP) locally into the cerebral fluid around the human brain without dangerously lowering blood pressure throughout the body," Heistad said in a statement released by the University of Iowa. "Neurosurgeons would insert the gene that codes for the peptide when they go in to clip the aneurysm."

The researchers report that the treatment appeared to reduce the neurological damage of subarachnoid hemorrhage in the rabbits.

Of course, what works in rabbits may not work in people, and even if the treatment proves to be effective, it may be 5 to 10 years before it is available, according to Heistad.

But despite the limits of an animal study, Heistad and his colleagues conclude in the report that the study "provides evidence, or perhaps proof of principle, that gene transfer may be useful for prevention of (blood vessel constriction) after subarachnoid hemorrhage."

(From Circulation Research: Journal of the American Heart Association 2000, 87.)