During 2000, about 11,000 people in the United States died from a ruptured abdominal aortic aneurysm. Eighty percent of these aneurysms, which doctors call AAAs for short, occur in men. Scientists know very little about why this often-undetected condition, for which there is no medical treatment, strikes men more often than women. But vascular surgeons at the University of Michigan Medical School have found some intriguing clues.
At this week's American College of Surgeons meeting in New Orleans, Derek T. Woodrum, M.D., a U-M resident in general surgery, will present new research results showing that smooth muscle cells from aortas of male rats contain 2.5 times more destructive MMP-9 protein and 10 times the level of MMP-9 gene expression compared to the same cells from female rat aortas. Known to be involved in AAA formation, MMP-9 is a cell-digesting enzyme that eats away at the wall of the aorta, leaving it vulnerable to expansion and rupture.
However, when Woodrum treated male rats with estradiol, a form of the female hormone estrogen, and then tested their aortas, he found that MMP-9 activity was substantially decreased. At this year's meeting, Woodrum will receive an American College of Surgeons "Excellence in Research Award" for his study.
Woodrum conducted his research in the laboratory of Gilbert Upchurch, M.D., an associate professor of surgery in the U-M Medical School, who studies factors responsible for gender differences in abdominal aortic aneurysms.
"Earlier studies have demonstrated that increased estrogen systemically inhibits the development of AAAs," Upchurch says. "Dr. Woodrum's study extends earlier research and suggests that there also is something inherent in males that increases