I have believed for a long tiome now that the use of stem cells to regenerate new organs and perhaps even limbs is a real possibility. There are several species that can do just this, such as the Axolotl, starfish, some amphibians, etc., and consider that deer grow new antlers every year. Life isn't possible without regeneration, as even humans 'regrow' every organ every seven years, and skin much faster. It's just that some creatures can grow far more complex structures than others, but the research is still in its infancy. We have already accomplished regrowing dead parts of the heart with the infusion of stem cells that form themselves into heart cells. Check out this link on the subject:
http://www.dailymail.co.uk/health/article-2112522/Transplants-Patients-day-grow-new-organs-stem-cells-replace-failing-body-parts.html 
