If the accidentally regenerative MRL mice are anything to go by, there is the strong possibility that salamander-style regeneration of limbs and organs could be brought to mammals - and humans in particular. The biochemistry might just be there, latent and unused ... after all, we all grew the limbs and organs we have once already.

Since this field has some overlap with more mainstream regenerative medicine via the study of stem cells and their role in regrowth in lower animals, money is beginning to move into limb and organ regeneration. Here's news of an interesting study in newts:

When a newt loses a limb, the limb regrows. What is more, a newt can also completely repair damage to its heart. Scientists at the Max Planck Institute for Heart and Lung Research in Bad Nauheim have now started to decode the cellular mechanisms in this impressive ability to regenerate and have discovered the remarkable plasticity of newt heart cells.

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whereas humans cannot regenerate damaged heart muscle adequately after a heart attack and the destroyed muscle tissue scars over instead, following damage, a newt’s heart can be completely repaired and the organ’s function can be completely restored.

The key to this ability to regenerate are the heart muscle cells themselves. When a newt’s heart sustains damage, its cells can lose their characteristic properties; they can dedifferentiate. The researchers were able to show that proteins typical of heart muscle cells - the heavy myosin chain and various troponins - were dramatically down-regulated in this process. At the same time, the cells embark on massive cell division to build up new heart muscle. It takes around two weeks for the heart function to be restored in the newt. The data shows that at this point the expression of the muscle-specific proteins is again normal, i.e. the cells have differentiated again, and have regained their characteristic properties.

The researchers isolated the heart muscle cells and cultured them. In most of the cells, Braun and his colleagues were able to demonstrate the existence of a protein called Phospho-H3. This protein is a marker for the G2 phase of the cell cycle and indicates that the newt heart regenerates without the involvement of stem cells. It also seems that the heart regeneration does not create typical wound healing tissue, called a blastema. Braun explains this finding: "The heart only has a relatively small number of different cell types. This could be a reason why the regeneration of heart tissue does not require a blastema." The researchers in Bad Nauheim found no indication that stem cells were involved in repairing newt hearts.

No stem cells - just heart cells getting up, changing, doing the work of stem cells, and changing back again. What might that mean for the future of regenerative medicine? There is a gleeful sort of "who knows?" with upthrown arms to be given in response to this sort of question at this sort of time - it's a revolution out there. Answers will come soon, and the medicine of the next decade will look very different as a result.

Technorati tags: regenerative medicine

Posted by Reason at December 5, 2006 8:36 PM | TrackBack (1)