Bioengineering researchers at UCSD's Jacobs School of Engineering will report in the Nov. 1 issue of Proceedings of the National Academy of Sciences (PNAS) that arterial endothelial cells subjected to repeated stretching (10 percent of their length, 60 times per minute) produced intracellular arrays of parallel "stress fibers" in a few hours.
The tests were performed on endothelial cells lining the aorta of a cow, but the endothelial cells of the human aorta are expected to react similarly. The stress fibers were made of actin, a fibrous protein that is part of the machinery that gives muscle its ability to contract. Actin also gives virtually all cells their ability to make an internal "cytoskeleton." The stress fibers of endothelial cells in arteries are aligned parallel to the long axis of blood vessels, and this alignment is perpendicular to the direction of rhythmic stretching caused by a beating heart. Such an orientation of stress fibers is a hallmark of healthy blood vessels, but scientists currently understand few of the factors responsible for generating that configuration.
Rubber bands and most other flexible materials react to stretching by forming stress wrinkles parallel to the direction in which they are being pulled. However, the healthy bovine aorta endothelial cells did not behave that way in tests performed in the laboratory of Shu Chien, a coauthor of the PNAS paper and a professor of bioengineering and medicine and director of the Whitaker Institute of Biomedical Engineering at UCSD. When Chien and his collaborators stretched the cells back and forth along one axis in the miniature workout chambers, the cells formed stress fibers perpendicular to the direction of stretch. "This orientation o
Contact: Rex Graham
University of California - San Diego