Understanding how to manipulate the signaling systems that command stem cells into action will enable many of the same beneficial results as stem cell transplants: "The chemical which summons stem cells from bone marrow to the site of a wound has been discovered by scientists. The study identified the distress signal - HMGB1. The authors believe it can be used to put 'a megaphone in the system' to improve the treatment of injuries such as burns and leg ulcers. ... Bone marrow was thought to play a role in repairing damaged skin, but the exact process was unknown. Scientists [gave] mice bone marrow cells that glow green - which can be tracked while moving round the body. They then wounded the mice and some were given skin grafts. In mice without grafts, very few stem cells travelled to the wound. Those with grafts had many stem cells travelling to the wound. ... grafted skin tissue has no blood vessels and therefore no oxygen. ... this environment leads to the release of HMGB1 [which] results in stem cells moving to the wound. ... Researchers [are] developing a drug to mimic HMGB1. They hope to begin animal testing by the end of the year and human clinical trials shortly afterwards."