" Accelerated wound healing is an application of particular interest to NASA , as wounds heal slowly in microgravity. In 2009, NASA researchers catalogued 219 in-flight injuries, primarily abrasions and lacerations, sustained by astronauts during spacewalks or their daily work. It is important to heal these types of injuries quickly to ensure full mobility for astronauts. In vitro studies on mice and rats found that LED light therapy caused a 140 to 200 percent increase in fibroblasts (the precursors of collagen, which is crucial for wound healing) and a 155 to 171 percent increase in the growth of human epithelial cells . These cells are found in the skin and blood vessels, where they serve as a physical barrier to prevent infection from pathogens ."