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Scientists believe humans might someday regrow lost limbs, just like we formed them during development. A fascinating new study suggests that humans share regenerative capabilities with creatures like salamanders and starfish – we just haven’t figured out how to activate them yet.
By studying axolotls (salamanders that can regrow severed limbs), researchers think we could unlock similar abilities in human bodies. James Monaghan, a molecular biologist at Northeastern University, and his team have identified that axolotls use “positional memory” to regenerate limbs. The National Library of Medicine describes this as “a property of steady-state cells (e.g., connective tissue cells), with the potential to maintain information over a lifetime.”
The regeneration process begins with two chemicals that humans also possess.
Monaghan’s team discovered that retinoic acid and the enzyme CYP26B1 – both present in human bodies – play crucial roles in the axolotl’s remarkable regenerative abilities. The difference is that axolotls have learned to utilize these chemicals in ways humans haven’t yet mastered.
“It could help with scar-free wound healing but also something even more ambitious, like growing back an entire finger,” Monaghan explained in a press release. “It’s not out of the realm [of possibility] to think that something larger could grow back like a hand.”
Their findings, recently published in Nature Communications, reveal that axolotls maintain a gradient of retinoic acid signaling throughout their bodies. For instance, their shoulders contain more retinoic acid and less of the CYP26B1 enzyme (which breaks down retinoic acid), while their hands have less retinoic acid. This gradient acts as a blueprint, telling regenerative cells called fibroblasts exactly what to regrow and how much to regenerate.
Understanding these regenerative signals represents a major breakthrough toward potential human applications. While humans have the same basic biological components – retinoic acid and fibroblasts – our cells don’t respond to these signals in the same way as axolotls’ cells do.
When humans injure an arm, our fibroblasts create collagen and form scars. In contrast, axolotl fibroblasts respond to retinoic acid by essentially rewinding development – they grow an entirely new skeleton instead of scarring.
Monaghan believes the key lies in teaching human cells to listen to these regenerative cues. “If we can find ways of making our fibroblasts listen to these regenerative cues, then they’ll do the rest,” he said. “They know how to make a limb already because, just like the salamander, they made it during development.”
