Guest blogger Alan Trounson: What A Mouse’s Toe Tells Us about CIRM’s Investment

Guest blogger Alan Trounson is President of CIRM

Yesterday, my colleague Uta Grieshammer used this space to describe a Nature paper out of Irv Weissman’s Stanford lab that sought to pin down which cells are responsible for the regrowth of the tip of a mouse’s toe after amputation.

Salamanders and many lower organisms have the ability to regenerate whole limbs and most of their organs. However, while mice and men have the capacity to regrow parts of certain organs, notably the liver, they have lost the ability to replace any part of our limbs other than the very tip of digits—fingers and toes.

How does this relate to CIRM’s research investments? Some critics of our model, notably one writer at the New York Times, have suggested that we would have better spent our taxpayer investment entirely trying to figure out how salamanders accomplish their more robust regeneration. Specifically, the recommendation was that CIRM should be directing researchers to investigate the salamander cells responsible for this feat – called the blastema.

A long-held theory suggested that in salamanders, adult cells at the site of injury can be dedifferentiated into a stem-like state called a blastema that can then go on to produce all the cell types—bones, skin, tendon, vessels and nerves—needed to regrow the digit tip. The Stanford work very clearly showed no evidence of such a blastema cell in mice. They labeled the adult cells of each tissue type with a different color florescent marker and after regrowth they saw very clear demarcations of color between the various tissue types. The skin cells formed skin and the bone cells formed bone.

CIRM funded this work in keeping with our philosophy of funding the full spectrum of stem cell research, across all cell types, and in basic research funding work that looks at all aspects of stem cell growth and maturation. By funding stem cell research broadly, we believe we have had more successes than if we had concentrated our funding on any one aspect of stem cell research.