Regenerating human limbs not easy, says study

Regenerating a new limb or organ in humans may not be as easy as mad scientist Curt Connors makes it out to be in the Spider-man movies.

But by studying a real lizard-like amphibian, the salamander, which can grow missing limbs, Salk Institute of Biological Studies researchers discovered that it isn’t enough to activate genes that kick start the regenerative process.

In fact, one of the first steps is to halt the activity of so-called jumping genes.
In the Mexican axolotl (tadpole-like form of salamander), jumping genes have to be shackled or they might move around in the genomes of cells in the tissue destined to become a new limb, and disrupt the process of regeneration, the journal Developmental Biology reported.

They found that two proteins, piwi-like 1 (PL1) and  piwi-like 2 (PL2), perform the job of quieting down jumping genes in axolotl, which can regenerate everything from parts of its brain to eyes, spinal cord, and tail, according to a Salk statement.

“What our work suggests is that jumping genes would be an issue in any situation where you wanted to turn on regeneration,” said senior study author Tony Hunter, professor of molecular and cell biology and director of the Salk Institute Cancer Centre.
“As complex as it already seems, it might seem a hopeless task to try to regenerate a limb or body part in humans, especially since we don’t know if humans even have all the genes necessary for regeneration,” said Hunter.

“For this reason, it is important to understand how regeneration works at a molecular level in a vertebrate that can regenerate as a first step.

“What we learn may eventually lead to new methods for treating human conditions, such as wound healing and regeneration of simple tissues,” concluded Hunter.