Regeneration and repair: new findings in stem cell research and aging." When it comes to the capacity to regenerate damaged parts of the body, humans are by no means the most advanced among animal species. At the level of single cell populations, humans do exhibit some degree of regenerative potential--for example, hepatocytes have the ability to restore up to 75% of a surgically removed or damaged liver. However, as every schoolchild knows, salamanders and starfish can regrow entire amputated appendages, a remarkable feat well beyond the scope of human capacity. Accordingly, the standing consensus position of the scientific community has deemed mammals fundamentally and unalterably different from those more ""primitive"" yet regeneration-competent species. Current approaches for the restoration of organ function in humans have therefore been limited to allogeneic organ or cell transplantation--strategies that, while effective, nonetheless exhibit major limitations based on availability of donor tissues and the risk of rejection unless extensive immunosuppression is induced."