June 6, 1995
Media Contact: John Cramer
Phone: (410) 955-1534
Animal studies at Johns Hopkins suggest that as people age they gradually lose their tolerance to the trauma of surgery, but the study results also suggest there may be ways to maintain some of their ability to recover.
Hopkins researchers transplanted old blood vessels into young rats and young blood vessels into old rats to determine whether aging itself reduces the ability to recover from surgical trauma. The results are reported in the July issue of the Journal of Gerontology: Biological Sciences.
"We wanted to see if the young vessels could rejuvenate the heat shock protein 70 stress response -- a type of molecular response in all living organisms, including humans," says study author Robert Udelsman, M.D., director of endocrine surgery at The Johns Hopkins Medical Institutions.
The investigators switched aortas between 100 young and old rats. The old vessels put in young rats behaved like young vessels, while the young vessels put in old rats behaved like old vessels. Investigators measured the effect on heat shock protein 70 (HSP), a primitive kind of protein essential for cell survival in all animals, including people. The study confirmed that in older rats, HSP production decreases along with their tolerance for surgical stress.
"We found that the age of the animal receiving the transplanted blood vessel, rather than the blood vessel's age, determined the amount of this molecular response to stress," Udelsman says.
All of HSPs' precise functions are unknown, but there's plenty of evidence that they are part of the body's natural healing powers, acting as molecular chaperons that help regulate other proteins within cells, says Udelsman. These proteins thereby help fight infection and inflammation, regulate hormone levels, fluid balance, metabolism and blood pressure, and perform other tasks.
Part of the body's biochemical reaction to surgery is to make more HSPs in the adrenal gland and blood vessels in an apparent attempt to stabilize itself. HSP levels increase locally in tissues in several human diseases, including blockage of arteries, arthritis and thyroiditis. They also increase during early rejection of organ transplants and appear necessary for normal wound healing.
If researchers can figure out a way to boost HSP production in elderly patients undergoing operations, surgical recovery and outcomes might improve.
The study was a collaboration between Hopkins and the Gerontology Research Center at the National Institute on Aging, and was supported by a grant from the National Institutes of Health. Coauthors of the study were Ding-gang Li, M.D., and Carole A. Stagg, B.S., both of Hopkins, and Nikki J. Holbrook, Ph.D., of the NIH.