Scientists create a working animal limb in a lab

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...

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.

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

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.

Doctor Rat.

But don't read it if easily made unhappy by literature.

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.

Sufficiently advanced robotics is indistinguishable from life. - Adapted from Arthur C Clarke.

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 think you mean an artificial biological creature, rather than a biological robot.

Geez, how far off is Frankenstein?

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.

[1] People are totally working on this which is absolutely amazing. https://www.google.com/search?q=3d+printing+extracellular+ma...

The natural progression is man will create its own replacing species.

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'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 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.

They already can reconnect limbs and other body parts https://en.wikipedia.org/wiki/Replantation.

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.

What kind of job would you get with a PhD in "Future Studies"?

OK, I have to ask: What is Future Studies? Googling, it sounds vague and unspecific. Are they offering PhD's in it...?

Where can I find futures studies PhD's? They sound like fun people to talk to.

PhD in "future studies" --> LOL