All sorts of animals can lose a limb and walk it off, assuming the limbs they lost weren’t their legs. They don’t freak out because they know they’ll grow them back anyway. However, there aren’t many creatures on the planet that can do that after they’ve lost their heads.
The freshwater flatworm Schmidtea mediterranea is one such creature. In fact, this flat invertebrate can regenerate any part of its body it wants to, including its head, guts, tail, whatever.
Chop it to bits. See if it gives a s**t. If you try to kill this thing, you’d better hope you’ve annihilated every single part of its corpse, because even a little bit of it remains, it can rebuild itself back into a full-on slithering worm. It’s the Wolverine of worms.
The secret to his regenerative powers is in his stem cells. While humans have only a relatively small number of precious stem cells hiding deep down in our bone marrow, the planarian has more stem cells than it knows what to do with. About 15 percent of his body is made of these little self-regenerating machines.
These stem cells can turn into any other kind of cell, and unlike human ones, they’re not locked down in tightly regulated “niches” controlled by neighboring cells. In fact, planarian stem cells seem to work just fine without the usual micromanagement.
Humans May Be Able to Regrow Limbs One Day Thanks to This Tiny Worm
In a new study published in Cell Reports, scientists from the Stowers Institute explored how these stem cells still mostly manage to follow the rules and rebuild exactly what’s missing without accidentally manifesting a bunch of tumors, which is what happens in us when our cells turn into little rebels and don’t do what they’re told.
The team, led by biologist Frederick Mann Jr., discovered a few unusual findings, such as the large, many-armed cells surrounding the stem cells called “hecatonoblasts,” which turned out to be completely uninvolved in the regeneration process.
That sounds like nothing, but it actually is a significant find. It means that, unlike most cells, planarian stem cells don’t let other types of cells influence their own processes. They’re stubborn.
Something that ended up playing a larger role in the process than anticipated was the worms on intestinal cells, which weren’t even in direct contact with the stem cells. Those intestinal cells were coordinating where and how regeneration happens.
That’s unusual for stem cell biology, where the cell’s location and its neighboring cells determine its fate.
According to researcher Alejandro Sánchez Alvarado, the ultimate goal is to understand how to get human stem cells to regenerate tissues on command without triggering cancer. If planarians can pull it off, and they’re just a bunch of dumb flatworms, then maybe we can too with a bit of help from science.
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