A new technique for improving delivery of stem cells may lead to better and faster tissue repair, a breakthrough with promise for sports medicine and military populations. Researchers at the National Institutes of Health Clinical Center discovered a way to enhance delivery of transplant cells in rodents to a desired site by increasing presence of chemicals that attract the introduced cells. Non-destructive pulsed focused ultrasound interacts with tissue to elevate levels of naturally produced chemicals (such as cytokines, chemokines, and growth factors) on target tissues. Transplanted stem cells have receptors for these chemicals, so an increased presence attracts more of them to the desired site.