For years biologists were so focused on the internal workings of cells that they pretty much ignored the “glue” that holds those cells together in a body, human or otherwise. And yet once researchers started looking deeper into the stuff between cells, known as the extracellular matrix, they began to realize just how dynamic the whole arrangement is. Not only does the overlooked matrix provide the biological scaffolding necessary to keep animal tissues and organs from dissolving into a gooey mess, but it also releases molecular signals that, among other things, help the body heal itself.
Building on this insight, investigators are now developing a new approach to tissue engineering—one in which the regenerative power of nature's own scaffolding plays a starring role. The idea is to harvest extracellular matrix from, for example, pigs and implant it in patients suffering from a large internal injury (after first stripping away the components that would have triggered a destructive attack by the recipient's immune system). The newly placed scaffold would then release molecules that attract semispecialized stem cells from the rest of the body to fill the various niches and to differentiate into exactly the type of tissue that should be there. Eventually even the implanted latticework would be replaced with human proteins and fibers, entirely erasing all trace of its barnyard origins.