I don’t get why is possible to regrow a lot of stuff (skin, muscles, broken bones etc.), but only to a certain extend. At one moment you are suddenly not able to rebuild things.
Why is that and what determines what we can regrow?
That depends on what you’re referring to. Quick caveat, I’m not an expert in regenerative biology, but I have studied it somewhat.
The trick is that the healing that you’re referring to, it’s not really healing in the way that you’re imagining it. The skin doesn’t really quite grow back in the same way. Instead, there’s more collagen than there normally would be (we would then call that scar tissue). In essence, we’re not really healing, our bodies are just doing a patchwork fix. The presumed reason is that our bodies figure that it’s not going to cause any problems before we die from other causes. This is really quite true of other tissues as well. The liver is known to be able to grow back, but if you look at the microstructures, the regrown stuff is missing a lot of the nuances that the original had. Our bodies expect us to live 70-ish years, and so they don’t care about anything that could happen after that.
In order to truly, really regenerate, you’ll need stem cells. Some animals are remarkably good at keeping around stem cells and regenerating, but somewhere along the evolutionary line, mammals lost the ability to use stem cells. It’s still an ongoing area of research about why this happened and whether we can generate stem cells in the lab and whether we can manipulate stem cells to our benefit. It should also be pointed out though that, by its intrinsic nature, stem cells divide and don’t specialize into any roles, so it’s very easy for them to go cancerous. In the few spots where mammals do keep stem cells around, their division is very tightly controlled, and even then they are the source of the most common cancers in humans
deranger@sh.itjust.works 1 week ago
Mammals can’t de-differentiate cells back to progenitor stem cells, so their ability to heal is limited.
Shou@lemmy.world 1 week ago
This is not true.
It’s not about cancer, it’s about senescence. Mammals’ and many other animals’ only way to adapt to an ever changing enviroment, is: remix genes + mutations + epigenetic factors. And hope for the best.
In order for parents to not compete with their offspring for food or sex, they have to die. Which can simply be a limited lifespan by cells getting sloppy in their maintenance, or by choosing to starve yourself to death.
If you get injured badly, you have failed to survive. It is more energy and evolutionarily speaking to let you die, than expend energy on your recovery. Energy is limited in every enviroment. Depression and lethargy are interesting aspects to self-elimination (not suicide) as well.
Senesence is also why cancer is far more common in older people than in children. Our repair functions stop doing their job well as part of senescence. Increasing the chance and speeding up the development of tumors.
deranger@sh.itjust.works 1 week ago
Those repair functions working better than normal is one of the hallmark signs of cancer, specifically telomerase being reactivated. Senescence is anti cancer, not pro cancer. You know those HeLa cells that are immortal? Cancer cells. Having a time limit or replication limit on cells through senescence is a great way of limiting tumors.
Thavron@lemmy.ca 1 week ago
So how does this apply to Wolverine? Is he a lizard?
mapleseedfall@lemmy.world 1 week ago
He’s fiction. Thats how it apply