Albinoaxolotl3

Researchers are studying the axolotl Ambystoma mexicanum, a salamander that regenerates its limbs perfectly, searching for clues to the mechanism behind the process. “In some ways this study of the axoltol’s proteins was a fishing expedition,” says David Stocum. “Fishing expedition can be a derogatory term in biology, but for us it was positive, since we caught some important ‘fish’ that enable us to formulate hypotheses as to how limb regeneration occurs.”

INDIANA (US)—A salamander that can regrow appendages may provide important clues to how similar regeneration could be induced in humans.

Researchers from the School of Science at Indiana University-Purdue University investigated more than 300 proteins in the amputated limbs of axolotls, a type of salamander that has the unique, natural ability to regenerate appendages from any level of amputation. Findings suggest that quantities of enzymes involved in metabolism decreased significantly during the regeneration process.

“In some ways this study of the axoltol’s proteins was a fishing expedition,” says David Stocum, professor of biology and director of the Indiana University Center for Regenerative Biology and Medicine, who led the study.

“Fishing expedition can be a derogatory term in biology, but for us it was positive, since we caught some important ‘fish’ that enable us to formulate hypotheses as to how limb regeneration occurs,” Stocum says.

“Comparison of these proteins to those expressed in the amputated frog limb, which regenerates poorly, will hopefully allow us to determine how we might enhance limb regeneration in the frog and ultimately in humans, Stocum adds.

With few exceptions—notably the antlers of moose, deer and their close relatives, the tips of the fingers and toes of humans and rodents, and the ear tissue of certain strains of mice and rabbits—the appendages of mammals do not regenerate after amputation.

Limb regeneration in the axolotl occurs when undifferentiated cells accumulate under the wound epidermis at the amputation site, a process known as the establishment of a blastema. These cells are derived by the reprogramming of differentiated cells to a less specialized state, and from resident stem cells.

The team found that a protein that appears to keep cells from dividing until they are fully dedifferentiated and reprogrammed to begin forming a new limb was expressed at high levels throughout blastema formation. Details were published in the journal Biomedical Central Biology.

They also noted that there are many proteins that appear to help cells avoid cell death. Because amputation is very traumatic, this is critical.

“We found proteins that point to several areas that need to be studied closely to give us vital information about the mechanisms that operate to form a blastema that then goes on to regenerate the missing parts of the limb,” says Stocum.

Researchers from Central Michigan University, the University of Kentucky, and the University of Illinois contributed to the study, which was funded by the W. M. Keck Foundation.

Indiana University news: http://www.indiana.edu/news/