Healing by Design

Plastic parts in your shoulder? Tissue engineers say it could happen as they research ways to help bodies heal themselves. You've torn your rotator cuff delivering heat across the plate. What now? You're in for tendon-repair surgery, significant rehab, and the ever-present risk of re-injury. But tissue engineers want to change all that. For decades medical researchers have been looking into what makes tissues grow and heal effectively. The factors are as varied as the tissues they study, but one constant remains: Cells heal better with a framework to grow on. Called extra cellular matrices (ECMs), these frameworks occur naturally in healthy tissue. Tissue engineers are investigating new ways to artificially create and deliver the scaffolding that can speed healing. In damaged tissues, such as torn tendons or bones that fail to knit, a scaffold can be surgically implanted to support the body's natural construction processes. Natural ECMs provide mechanical support to growing cells, but they also give them places to anchor and contain molecules that trigger the body's repair mechanisms. Researchers are evaluating different types of natural ECMs and investigating cells' ability to assemble themselves without a scaffold. They're also applying what they've learned to develop synthetic scaffolds from biodegradable polymers that can mimic and, perhaps, improve on ECM functions. Natural ECMs come from healthy tissues in the patient's body or from tissues in other mammals. Parts of the skin, the small intestine, the sack around the heart (pericardium), and the tissue between layers of muscle (fascia) are already used surgically as scaffolds after they are treated to remove living or dead cells. Dr. Kathleen Derwin of the Cleveland Clinic has compared the tensile responses of commercially available natural ECMs to each other and to the tendons damaged in rotator-cuff injuries. "We can mechanically load the scaffold to represent real-world