Stem Cells: Nature’s DIY Kit For Fixing Anything (Except Broken Hearts)

By Hamsini

What if I told you that the cure to practically every human ailment—from Alzheimer’s to Autoimmune diseases, from broken bones to blood cancer—is in our bodies? What if I told you that we all have little superhero cells in us, just waiting to be unleashed? What if I told you that these miracles are, quite literally, the very things that everything in us is made of?

Too far-fetched? Try this on for size: We could regrow limbs and organs, erase spinal injuries, and even get rid of wrinkles—permanently. Ageing would no longer be a one-way street. Amputees would get their arms, legs, and fingers back. We wouldn’t need pacemakers or hearing aids.

Okay, let’s back up and look at the science. Stem cells are cells with the potential to develop into any type of cell in the body. They’re the cells that take us from microscopic embryos to the walking, talking, thinking human beings we are. They tend to serve as a joker card for our bodies—standing in for any position that needs filling, adapting and differentiating to any role. That means they can rush in to fix a broken bone or replace damaged bone marrow. In theory, we could grow new limbs and replace cells as they die.

Sounds too good to be true? That’s because it is. Stem cells might be extremely useful when it comes to turning an embryo into an adult, but they can get out of hand. As a cell whose entire purpose in life is to multiply, they’re incredibly susceptible to uncontrollable division. That usually causes tumours or cancer, which we’d all like to avoid. Remember Dr Curtis Conners from Spiderman? He turned himself into a scaly, tail-wagging creature after a risky experiment with stem cells—a good reminder that we’re playing with the human body here. We’re working with things we don’t fully understand, and it’s important to be careful, take precautions, and never—ever—turn yourself (or the entire human race) into green toothy lizards.

But while Dr Connors might have been misguided in his attempt to begin a new race of half-lizard humans, his original idea is still one scientists think about. Why can’t we regenerate limbs? Our liver regenerates itself, and so does our skin, so why not complex organs? Geckos do it all the time, don’t they? They can drop their tails and then regrow them, thanks to special stem cells called radial glia. They not only regrow the flesh part of the tail but also the scales and bones and even a new spinal cord. Many animals can do this—salamanders, nematodes, starfish, jellyfish, and, of course, the poster child of regeneration, the axolotl. If we could find a way to safely replicate their mechanisms in our bodies, there’s no telling what we could achieve.

So why can’t we regrow limbs? If a gecko can find a way to prevent cancer, why can’t we? Well, when we lose a limb, we form a blood clot to close the wound, and then eventually, we form scar tissue. When a gecko loses something, scar tissue never forms. The wound closes more rapidly, and the cells revert to a less specialised form. The cells form a blastema—the bud of the new limb—which then multiplies, growing into an outline of the limb, then specialising into bones and muscles and nerves. The clever thing is that the blastema knows its location and grows accordingly. It doesn’t, for example, grow an entirely new arm for an amputation at the wrist.

But how?

The simple answer is that we don’t know yet. Axolotl DNA is huge—ten times longer than the human genetic code. There are so many fail-safes and contingencies written in that we don’t even know where to start. It’s challenging to study the basis of their abilities, but we do know that it’s not some simple gene that we can isolate and replicate. We could have the genes we need for regeneration, but they could be switched off in humans. Axolotls and humans do share a common ancestor, after all. Somewhere along the way, evolution favoured regeneration in axolotls but not humans. A piece of evidence for this? Sometimes a clump of nerves can grow from the stump of an amputee, creating a painful condition called a neuroma. This could be a remnant of regeneration that fails to reach completion.

But back to the original question. Why can’t we regrow limbs? Our immune systems are a lot more sensitive to cancer, and we mammals have a higher energy requirement. That might make the quick fix of scarring a better evolutionary choice than the time-and-energy-consuming process of regrowing a lost limb. Both these reasons are still theories, though. We don’t really know why our stem cells don’t work the same way theirs do.

But wait. If we could regrow limbs and bones and nerves—perfectly—would it really be useful? It takes axolotls hundreds of days to regrow a limb that functions precisely as the old one, so for humans, we’d be looking at years of work. That’s years of energy that could be devoted to something else. But that’s not to say that axolotls don’t have anything to give us—we could speed up wound healing with minimal scarring and side effects. They could also show us how to fight cancer—by controlling a cancer cell’s environment and just forcing it to behave normally.

So while it doesn’t make much sense to take another animal’s ability and force it into our bodies—looking at you, Dr Connors—we can still learn a lot from them. Advancements in lab-grown organs and prosthetics improve every day, and those provide amputees with options that don’t result in scaly green sewer monsters. No superpowers, maybe, but there’s a lot of really cool stuff down the line.