Over the last decade, scientists have experimented with using stem cells to heal or replace the scarred tissue that mars the heart after a heart attack. While the cells do spur some level of repair in animals, human tests have resulted in modest or transient benefits at best. Now researchers have developed a new kind of biological sutures, made from polymer strands infused with stem cells, that might help surmount two major obstacles to using stem cells to heal the heart: getting the cells to the right spot and keeping them there long enough to trigger healing.
Scientists from the Worcester Polytechnic Institute, in Massachusetts, have shown that cells derived from human bone marrow, known as mesenchymal stem cells, can survive on the threads and maintain their ability to differentiate into different cell types after being sewn through a collagen matrix that mimics tissue. Preliminary tests in rats suggest that the technology helps the cells survive in the heart.
“This is an out-of-the-box approach,” says Charles Murry, a director of the Center for Cardiovascular Biology at the University of Washington, who was not involved in the study. “Putting cells on thread—once you hear it, it seems simple. But I’ve been in this field for 15 years, and I never thought of it.”
One major challenge has been to get an adequate number of cells to remain in the area of injury. For example, in human studies of injected mesenchymal stem cells, only one percent to about 10 percent of injected cells remained at the site after injection. “Presumably the cells will be much happier if they have something to adhere to than if you just put them in and left them to fend for themselves,” says Murry.
Glenn Gaudette and collaborators at Worcester Polytechnic created the sutures with hair-thin threads made of fibrin, a protein polymer that the body uses to initiate wound healing and a common ingredient in tissue engineering. The microthread technology was developed by George Pins, associate professor of bioengineering at the institute.
The strands are transferred to a tube filled with stem cells and growth solution; the tube slowly rotates, so the stem cells can adhere to the full circumference of the suture. Once populated by cells, the suture is attached to a surgical needle.