If we make skin and muscle cells when we heal cuts and heal/generate bones after breaking them, why wouldn’t we be able to grow a finger if one is cut off?
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Our body heals like a blind handyman repairing a house.
If a ball crashes through a window, you call up the blind handyman and they feel around the impact. Glass shards. Window frame. Must be a broken window so that can be fixed completely by ordering a new window.
One day a car dries through the wall, taking out the entire window frame. After everything is cleaned up, you call up the blind handyman. However, they only feel the large hole in the wall and has no idea there used to be a window. The best and quickest thing they can do is seal up the hole to prevent things outside from getting in and things inside from getting out (scar).
Our body heals based on the surrounding tissues near the wound. If it can’t figure out what was there or if the wound is too large, it becomes a scar.
You can buff the scratches and hammer the dents out of a car with just what’s in your garage, but can you build a new engine?
Your body is decent at fixing minor damage that just requires cells to haphazardly copy themselves to fill in a gap, but fully replacing missing functional tissue is much more difficult. You can’t just tell the fingertip cells to make a little more fingertip, they’re all gone.
During development you undergo an enormously complex series of steps that form your systems and tissues in sequence. You can’t re-start that sequence at some random point in some random location. This is by design, as accidentally turning that function back on would be disastrous.
Figuring out how do do it in a controlled manner is the holy grail of bioscience.
Regrowing a finger requires the generation of muscle, bone, skin, and blood vessels. These would all need to be developed in tandem to ensure that the regrown finger functions as intended, looks like your finger used to look, and doesn’t actively hurt you.
On the other hand, regrowing skin cells is a comparatively easy task. That’s a simple repair in an area bordered by damaged cells, so it’s clear to the body where the repair needs to happen and what kinds of cells need to be repaired.
It’s too complex to generate all of that. The task of regenerating some skin cells or repairing muscle/bone is smaller than regenerating muscles, tendons, nerves, skin, bone, veins, etc.
That’s some really advanced stuff that even the best hand surgeons can’t accomplish. My husband got his hand caught on a table saw back in 2015 and cut one finger off and mangled 2 more. 5 surgeries later and he never regained full use. A body can only do so much.
I like the analogy of the blind handyman/broken window/broken wall. It’s a great example.
in the future man will have Axolotl dna implanted in the human genome so that everybody will regenerate philangies
The joint is the hardest part, we can regenerate(with some medical assistance) a finger up to the first joint.
I no longer recall the specific genes involved (it’s been a while since my days studying evo-devo at uni) but generally, there are certain genes (such as PAX6, HOX genes, among others) which are highly upregulated during development (when you are in your mother’s womb). They direct where cells form tissues, to what shape they form in etc. which essentially becomes your human body plan / body parts once your embryogenesis concludes.
Once that embryogenesis stage is over and you are delivered, these genes generally get downregulated – and in any insult occurring thereafter, they can no longer “help” you reform the lost body part.
This is generally the “rule” amongst mammalians and every other species with the exception of the axolotl (Ambystome mexicanum).
Though I’m no longer updated in the current studies on that species, but as far as I know it is being studied as a model organism of organ regeneration, possibly to learn how to apply it to humans.
**Anyone currently in the field of developmental biology may correct any errors I might have mentioned. Feel free to add any updated insights as well.
Yes in theory, but only of scar tissue does not form at all. Figure that one out any you will help alot of folks amd make $$$.
Imagine Manhattan Island gets blown up, Times Square, Central Park, all of it. Boom, gone.
Now imagine trying to rebuild it, but all you know is how to build walls and fences.
Bridges? Nah they’re walls now.
Trees? Walls.
Pizza joints? Walls.
You’re trying to replicate something very complicated with very few tools to actually do so.
Your body doesn’t know what it looked like before, it can only patch things up with walls.
Every call knows what they are and what is supposed to in their immediate vicinity. That is how we develop from one cell to what we are. There is a gradient and different cells as they form know where they are supposed to be in that gradient. But once one stage is completed, the instructions on how to make that gradient is packed away and sealed, it is no longer needed. After this these cells know where they are and what they must become, and they then proceed to become that and replicate to make that thing. After this has been done these cells forget what these instructions; however some can be tricked in to changing if given the right conditions, like being placed to the correct scaffolding (cellular matrix) or next something like bone. They realise that they are in a certain condition where they are supposed to be come certain things.
Imagine you are about to form a line in alphabetical order with class of kids. No kid needs to know the alphabets fully to form this line. Those with A as a first letter go towards the start and those with Ö go to last. Then every kid just finds the place over time, they don’t need to know their exact position, just who is supposed to be next to them.
Technically there is nothing preventing our bodies from forming new limbs if one is lost, it is just we don’t have the ability to activate those genes after we been fully formed as embryos. And if we could trigger them we aren’t really sure if they would know that they are. You might grow a finger to a cut in your knee.
But here is the thing! We been able to regrow tissues. Bladder, Penis, Vagina, Thymus, been regenerated. Researchers have had some success at regrowing toe- and fingertips so they also grow the nail. Vasectomies reversing themselves is a well known issue. This is actually a exciting field of medicine, tissue engineering. And we are actually close enough that give 20 years and we might be replacing organs all the time with new engineered from the patient’s cells. Add on top of that recent breakthroughs in preventing and reversing aging. A big problem of aging is that cells forget what they are supposed to do and just kinda do nothing but stay alive and drain resources, we been able to get them to remember what they are – in mice. People alive now might be first ones to not have to die from biological issues and might be able to get back body parts they have lost.
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