It sounds like pure science fiction, but scientists are currently working to unlock the secrets of limb regeneration in mammals, drawing inspiration from salamanders.
So, could someone who is born with, say, an underdeveloped limb be able to grow a new one using this treatment—or does the human body lack the blueprint?
According to Muneoka, it depends on the reason for the underdeveloped limb.
If this treatment has the potential to regrow human limbs, what else could it do?
There’s also research in salamanders that show that two proteins that are important for limb regeneration are also important for regeneration of other structures, such as gills.
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Imagine losing a finger in a kitchen mishap or an entire limb in an accident. Instead of learning to adapt to a prosthetic, your doctor prescribes you a serum. A few months later, your bone, muscle, nerves, and skin have perfectly knit themselves back together. Your limb is entirely regrown.
It sounds like pure science fiction, but scientists are currently working to unlock the secrets of limb regeneration in mammals, drawing inspiration from salamanders. Axolotls, a type of salamander, can take roughly 40 to 50 days to regrow lost limbs, which is a flash compared to humans and other mammals who lack the ability all together. But a new treatment could change that shortcoming.
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In a recent study published in Nature Communications , researchers from Texas A&M University used a specially-formulated serum that encouraged mice to form a blastema—the temporary cellular structure that helps organisms like axolotls regenerate structures.
How were they able to do this? According to study author Ken Muneoka, PhD, professor of veterinary physiology and pharmacology at Texas A&M, he and his team amputated part of a mouse’s finger. From there, researchers followed three steps to regrow the digit:
Wait for initial healing: Instead of treating the wound right away, Muneoka and his team waited for the skin to close up and heal over. The wound actually has the highest potential to regrow right when the skin closes and the body’s natural inflammation peaks, Muneoka explains.
Apply the first protein (FGF2): Once the skin closed, Muneoka and his team implanted a tiny bead containing a protein called FGF2. While this protein doesn’t cause full regrowth on its own in adult mice, it successfully stops the body from forming a scar, according to Muneoka. Instead, it tricks the wound cells into forming a “blastema”—a mass of multiplying, unprogrammed cells that is usually seen when animals like salamanders regrow lost limbs. Simply put, it helps the body form a “blueprint.”
Apply the second protein (BMP2): After the blastema formed, Muneoka and his team treated it with a second protein called BMP2. On its own, BMP2 only helps fix and lengthen broken bones, according to Muneoka. However, because it was applied after the first protein, it uses the newly formed blastema cells to grow an entirely new, complete bone at the tip of the finger.
So, could someone who is born with, say, an underdeveloped limb be able to grow a new one using this treatment—or does the human body lack the blueprint? According to Muneoka, it depends on the reason for the underdeveloped limb.
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“The human body uses the ‘blueprint’ to form the limb in the embryo, and we found evidence that this ‘blueprint’ is re-utilized when regeneration is stimulated by our treatment,” Muneoka says. In other words, someone whose limb was underdeveloped because of external factors in vivo, such as alcohol or drug exposure, might see better results than someone whose underdeveloped limb was caused by a genetic modification—or a damaged blueprint. “If the ‘blueprint’ is intact, then the expectation is that the regeneration should be possible,” he says. The amount of time this would take isn’t yet known.
If this treatment has the potential to regrow human limbs, what else could it do? Could it eventually be used to regrow more complex structures, like organs? There are studies—such as one published in Nature Genetics and another in PNAS —that show lung formation and limb formation share similar genetic requirements, according to Muneoka. There’s also research in salamanders that show that two proteins that are important for limb regeneration are also important for regeneration of other structures, such as gills.
“This suggests that the regenerative process may have universal characteristics, which gives us hope that our strategy for stimulating digit regeneration could have broad application,” Muneoka says. “We believe that our study outlines a general strategy for enhancing regenerative capabilities in humans. The specific details for this strategy will likely differ between organ systems, and that needs to be determined empirically.”
The tricky part, Muneoka says, is that organ regeneration requires time that may not be possible if the organ’s use is required to stay alive. So depending on the extent of the organ’s damage, a transplant from a donor may still be necessary.
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Regeneration of body parts is unlikely to lead to immortality, though, according to Muneoka. “If individuals could regenerate organs throughout their lives, it would improve the quality of life, and it may enhance lifespan,” he says. But he points to a 2021 mouse study that he worked on, which found that blastema formation and the quality of the regenerative response declines with age.
So while we won’t be able to live forever or sprout a new pair of lungs overnight, the blueprint for human regeneration is already coded inside us—an exciting step forward for what’s possible when it comes to human healing.
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