A collaborative group of German and American researchers has identified the important biochemical processes involved in the regeneration of limbs of salamanders. Nearly unique in their great ability to replace lost appendages, salamanders were thought to possess pluripotent stem cells with greater abilities to differentiate than those of mammals. Turns out that in salamanders cells located at the location where the damage has occurred keep a memory of what was in the vicinity, providing guidance for regrowth of future cells. The finding opens the possibility that scientists will be able to replicate this phenomenon in humans, leading to treatments for spinal cord injury, loss of arms and legs, and other serious injury.
From the study abstract:
During limb regeneration adult tissue is converted into a zone of undifferentiated progenitors called the blastema that reforms the diverse tissues of the limb. Previous experiments have led to wide acceptance that limb tissues dedifferentiate to form pluripotent cells. Here we have reexamined this question using an integrated GFP transgene to track the major limb tissues during limb regeneration in the salamander Ambystoma mexicanum (the axolotl). Surprisingly, we find that each tissue produces progenitor cells with restricted potential. Therefore, the blastema is a heterogeneous collection of restricted progenitor cells. On the basis of these findings, we further demonstrate that positional identity is a cell-type-specific property of blastema cells, in which cartilage-derived blastema cells harbour positional identity but Schwann-derived cells do not. Our results show that the complex phenomenon of limb regeneration can be achieved without complete dedifferentiation to a pluripotent state, a conclusion with important implications for regenerative medicine.
Full story: Scientists: Salamanders, regenerative wonders, heal like mammals, people….
Abstract in Nature: Cells keep a memory of their tissue origin during axolotl limb regeneration
Images: Top: Axolotl salamander by cataclico; Side: Green nerve cells cluster around a growing nerve in this cross-section of a regenerating limb. D.Knapp/E.Tanaka.