if this method can "scale-up" to any arbitrarily complex tissue, then conceivably could you decellularize and re-implant an entire donor body, and do a head transplant? Effectively, giving someone a brand-new body?
For now it seems you would need a donor body to act as the "scaffolding" for your progenitor cells. Pessimistically, there may one day be a blackmarket for scaffolding cadavers with desirable features.
> While the progenitor cells needed to regenerate all of the tissues that make up a limb could be provided by the potential recipient, what has been missing is the matrix or scaffold on which cells could grow into the appropriate tissues.
> ... living cells are stripped from a donor organ with a detergent solution and the remaining matrix is then repopulated with progenitor cells appropriate to the specific organ.
I wonder if a person could also "upgrade" their body, or invent articulate organs with unique functions, such as printing a scaffolding for wings or a specialized muscle structure attached to the hip for opening beer bottles.
Perhaps they can strip back your own body to a scaffolding and regenerate the tissue. You spend a week as a brain-in-a-vat while your body gets regenerated then you start again.
There's more than just fabrication to consider. The reason they think generated limbs might be useful is that in current hand transplants, pre-existing limb nerves grow into the new hand, giving it sensation. This does not happen with the spinal cord (and anything that made it happen would be a huge therapeutic breakthrough all on its own). The cranial nerves (those going directly from the brain to the heart, gut, ears, nose, etc) are another potential stumbling block.
That said, it does make the (numerous!) science fiction novels that have had something like this as a premise seem somewhat more plausible...
First, you start with a naturally grown bone-in leg of lamb. Then you completely decellularize it by running a detergent solution through it for a week. Then you culture the replacement lamb cells, and inject them into the appropriate places on the limb. Then you place the leg in a bioreactor and wait until the cell cultures spread throughout the existing matrix. Then, when you finish, you have a lab-grown leg that is 80% as good as the natural one!
Having to start with a natural limb seems to be the roadblock here.
So we're going to need to be able to volume-print an extracellular matrix before anybody gets any vat steaks. I'd guess a destructive scan of a single natural beef tenderloin and some stem cells from the World's Most Delicious Bovine would allow for unlimited numbers of vat-grown copies. And then it would still take quite a while to bring the unit cost down below feedlot cattle.
So I guess I just have to wait until we have good enough 3D scanners to build a model of the non-cellular structures in the leg, then we need good enough 3D printers to print edible non-cellular structures at small enough sizes for the re-cellularization to work, and then I can eat a lab grown leg of lamb!
We basically just need a way to print 3D collagen. We largely know what the structure is, the problem is replicating it.
This is compounded because collagen strength/structure increases after deposition through the action of enzymes that crosslink collagen chains - a problem that would need to be overcome in order to print it
No, because for this to work you start with a bone-in leg of lamb, then strip out the cellular material and regrow it with new cells more suitable for the host.
there is no point if you just want to eat it
however, I guess if you want to have different type of legs (picture Pan) then I guess you could strip out the cellular material from a goats leg and repopulate it with human ones then graft it on.. hmm, I wonder if that would work anyway
Wow it must be great to be a Rat :-) There must be a story where the humans die off leaving behind a sentient rat species with a really deep medical knowledge.
That said, this feels like a pretty big bump in the tissue engineering field. I hope it holds up when they move up to larger mammals!
I wonder if there are any applications in building biological robots? I don't know too much about the process so perhaps this is far fetched but if you could build a robot with organic appendages that could be "swapped out" once they are used or damaged I would image you could end up with something far more versatile than the mechanical equivalent with servos/solenoids etc.
It's been several years since I've been active in anything resembling this space (I did my master's in a biorobotics lab and was 50/50 between biomedical and mechanical), so take this with a grain of salt.
However, as awesome as this is (composite cellular constructs have always been very difficult), it's probably not especially applicable to biorobotics, because they're using the "wash and repopulate" method for growing the appendage. Basically, you take an existing appendage from a (presumably NOT living and breathing) fully-developed donor animal and strip it of all cellular material. That leaves what's called the extracellular matrix, which is a little bit like the rebar in a reinforced concrete lattice. So ignoring the obvious ethical questions here -- of which there are many, and which are critically important not to ignore -- but ignoring them, if you wanted to build a cyborg robot thing, you'd be much better off skipping the wash and repopulate, and maybe even skipping the "dead" part.
But from my perspective, that's no fun! I'd much rather design my own system from the ground up and have some flexibility to make improvements to "design" unconstrained by the very slow process of evolution. So in that case, I'd want to be able to 3d-print the extracellular matrix[1] and then populate it however I deemed fit, integrating it with a more efficient nerve-computer interface from the start.
A nervous public will demand that organic robots be given an arbitrarily short lifespan as a failsafe. Say four years. And those robots would also be restricted to working in outer space because it would be too hard to control robots indistinguishable from ordinary humans on Earth.
I'd imagine that rather than being "swapped out", a machine with components that could heal to some degree would be far more useful. But still an interesting idea.
Hm, they claim that it has "functioning" muscle tissue. But in the video the limb doesn't move, so I wonder in what sense the muscle tissue can be said to be "functioning."
From the article: "Functional testing of the isolated limbs showed that electrical stimulation of muscle fibers caused them to contract with a strength 80 percent of what would be seen in newborn animals. "
I don't follow. We're talking about body appendages from dead donors that have been washed of any cellular material so they can be retrofitted with cells from the recipient? I guess I'm not seeing what exactly is "lab-grown" here.
The limb? Animal donor cells do not spontaneously start to reconstruct the tissue when removed from host. Otherwise we would be sprouting all over the place.
Anyway, consider the washed out matrix just as a scaffolding for the proof of concept. We can probably eventually print cartilage so then the scaffolding can be done from first principles.
I'm not a medical expert but I would assume the theory is this. Take a donor part, wash it of the cells, re-populate with cells from the recipient... transplant... no rejection.
The problem like always is reconnecting the nerves which isn't something you have to worry about when transplanting organs.
If say you transplant a heart that heart will never talk to the recipients brain it will always continue to function on it's own, this also means that the brain cannot regulate the heart functions through the nervous system so mental states do not affect the hearts operations as they would with most people, hormonal neurotransmitters like adrenaline will still work tho.
Last year I had dinner with a student getting his PhD in Future Studies. I asked what are the most interesting technologies we would see in our lifetimes that the majority doesn't know about. He said, without hesitation, graphene and growing human body parts.
