In recent issue of Nature (15 May 2008), it has a special serial for regenerative medicine. Prof. Chien from Harvard gave an overview of regenerative medicines in the past 50 years. Prof. Zon talked about internal and external control of stem cell to grow to be any cell which we want them to be. Prof. Gurtner from Standford reviewed how wound is healing and its regeneration process. Prof. Passier explained his research about using stem cells to cure heart disease. Prof. Chidgey dealt with immune problem of transplanting stem cells between different persons. Prof. Xu looked into chemical details of regeneration process while Prof. Schroeder examined the overall possibilities for mammals. It becomes a new frontier for the biological research because it offers many new opportunities and challenges. Because when we grow up like all mammals, neurons or heart cell’s number will be fixed and regenerate no more. It is exactly the reason if neurons of old people die due to some disease, they will gradually lose their memories and the ability to think. If we could restart cell regeneration of mammals, For example, when people have a heart disease, or Brain disease such as Parkinson or Alzimer disease, people can simply grow back a partially new heart and some new neurons .

However, for the simple living creature such as Hydra, it has amazing ability to heal itself. For example, even you cut it to be cell by cell and mix them in the water, it will grow back to be a intact Hydra after a while, see Fig. 1, 2.

Fig. 1 Hydra being cut into pieces and grow back

Fig. 2 Hydro being cut and grow into two smaller one

There are also certain time when chicken is still in the form of embryo cells, you can cut these cell stuff into four parts, and they will grow into four complete chicken.

Fig.3 Champion of regeneration - axolotl

You can watch a YouTube movie here:
http://www.youtube.com/watch?v=OUFAT1WajP4

There is a champion of regeneration of animal that is called axolotl from Mexico. It can grow back any parts which you cut from its body, such as limbs, tail, jaw, even eyes and heart etc, see Fig. 3. Researchers now are working hard to find genes and small molecules that are responsible for this amazing regeneration ability. Hopefully, if it is known, it could be applied to help those people with disabilities and mental disease.