An axolotl salamander's limb in the process of regeneration. Image: Nature
I am a human, so if my limbs fall off, they stay off. This is unfortunate. It's also why Australian scientists are working to enable "salamander-like" limb repair in people. A new study published in the Proceedings of the National Academy of Sciences offers new insights into how salamanders self-repair, and holds clues as to how humans might learn from their example.
Salamanders, you see, are one of the few vertebrates with full-fledged regenerative capabilities: they can repair their hearts, brains, and spines, and they regrow entire limbs. What makes all that regeneration possible are cells called macrophages. These cells not only kill off invasive bacteria and fungi, study author Dr. James Godwin, of the Australian Regenerative Medicine Institute at Monash University, tells ABC Australia, they "actively determine repair."
Image: Georgia Tech University
Humans have macrophages, too, but no limb repair. So Godwin and his team of researchers set out to study what makes the salamander's restorative cells different. They extracted the macrophages from an axolotl, an aquatic species of salamander, and discovered that without macrophages, limb regeneration shut down entirely—the salamanders became like us, with lost limbs turning into stumps. But the scientists found that "Full limb regenerative capacity of failed stumps was restored by reamputation once endogenous macrophage populations had been replenished."
The discovery led Godwin to believe that a chemical release accompanying the deployment of macrophages is essential to limb regeneration—and that it's entirely possible that by emulating that chemical release, we may be able to spur human limb regeneration. As he writes in the study's abstract: "Promotion of a regeneration-permissive environment by identification of macrophage-derived therapeutic molecules may ... aid in the regeneration of damaged body parts in adult mammals."
In other words, if he can identify which chemicals are driving that limb repair, he may be able to concoct a medicinal treatment that could actually help humans regrow limbs right in the emergency room.
"The long-term plan," he said, "is that we'll know exactly what cocktail to add to a wound site to allow salamander-like regeneration under hospital conditions."