Medical Science Question
December 15, 2013 4:26 PM   Subscribe

Hello, I have a stem-cell related question which I hope someone familiar with said information can help me out with. Basically, I was wondering if it's theoretically possible to grow a brand new male reproductive organ within an existing male organ as its eventual replacement with the aid of stem cells (i.e. via stem cell injection into the organ tissue). The cells could then differentiate into specialized organ cells which could then divide, etc. What are your fact-based opinions about this?
posted by Neutron12 to Science & Nature (16 answers total)
 
I was wondering if it's theoretically possible to grow a brand new male reproductive organ within an existing male organ as its eventual replacement with the aid of stem cells (i.e. via stem cell injection into the organ tissue).

Uhh. . . no? Any time people talk about creating replacement organs, it's always growing the new one in some other location, whether that be a test tube, in a pig, or even elsewhere on the recipient's body.

But you can't just inject stem cells into something and have it basically regenerate itself. Or, at least, no one is talking about doing that as a plausible thing. That's basically magic.
posted by valkyryn at 4:41 PM on December 15, 2013 [1 favorite]


In fact, I do remember reading about an experimental model where cardiac stem cells were injected into an injured heart (with dead tissue). I believe the animal was a pig but I'm not sure. Anyway, the stem cells definitely survived and integrated themselves structurally into the heart as desired but they were not really functional. They didn't beat with the rest if the heart. They never really got hooked up to the rest of the heart so they didn't replace the original tissue. It seems some cues besides just being at the rigt place are required. I read this study due to my interest in endothelial function - I am not a stem cell expert. I'll see if i can find the paper. Hopefully someone with more than anecdotal can give you more info.
posted by Tandem Affinity at 5:00 PM on December 15, 2013


No, not until we understand the "symphony" of signaling pathways better for the tissue folding events that take place during human fetal development, which create all manner of organs, including genitalia.

We'd need to understand how to coordinate those chemical events so that the stem cells form the correct tissue type and grow a way that mimics how the original tissue developed. We don't yet have that capability.

Further, there are all kinds of hormones and other signaling molecules floating around your body at all times, tuned to different levels based on your age, genetics and environment. You'd need to manage fetal development processes that are now competing with those signals already firing in your adult body. We have only barely started to document how the human body works on a molecular level right now; throwing fetal tissue into the mix will introduce a whole huge set of unknowns and technical challenges.

It would probably be easier to grow a spare organ outside of the body in controlled lab conditions, in the functional equivalent of a test tube, then introduce that new organ into the body through some surgical procedure. I suspect you will see this within the next 20-30 years, as life sciences in that area improve, and most likely only for those who can afford the exorbitant costs that will be involved to recoup the research investment it will take to get there. I do not expect to see stem cell injections to regrow in situ organs on demand, before then.
posted by Blazecock Pileon at 5:00 PM on December 15, 2013 [2 favorites]


No way. If you think about how we get from "blob of undifferentiated cells" to "human being", there are a TON of developmental steps, chemical cues, etc, that are required, and even those steps go wrong in many, many ways. (If you're interested in this, a developmental bio textbook is the place to start.)

Very few of the signals that create a given organ will be present in a grownup human body (outside of a fetus in a uterus). The process of old cells slowly dying off and being replaced by new cells is totally different, and uses cells that are already highly differentiated, with many feedback loops presenting unchecked growth (thus why we don't all die from cancer in infancy). There are certain subcategories of tissues and cells for which I can imagine this happening at a small scale (the heart example above, for one), but one whole functional organ being made by putting stem cells near another whole functional organ as a template, no way.
posted by tchemgrrl at 5:28 PM on December 15, 2013


Warning: Wild Out-Of-Field Speculation Ahead!

Well... ok. I'm a biologist but not a cell biologist, so I'm definitely not an expert on stem cells, but I'll take a shot anyway. It's actually not totally clear to me what you're proposing (Grow a penis inside a penis? What happens to the original penis during and after this process? Why not just modify the existing penis? It's confusing.) My understanding though is that a lot of the techniques that people are working on regarding stem cells do in fact focus on augmenting the body's natural ability to heal and regenerate – growing new tissue within existing tissue.

All of that is really early days – even the simplest of these new treatments aren't ready for clinical use yet – but since you asked about what's "theoretically possible" rather than what is "doable with current or near-future techniques", I'll go ahead and speculate. I'll also mention that asking if we can "use stem cells" to solve some medical problem is kind of like asking if we can "use chemicals" to do it. "Stem cells" are a really broad category of (potential) therapies and without narrowing it down some it's hard to say much that's very meaningful.

Setting aside the confusing idea of growing a penis inside another penis and assuming for the moment that we're just looking to "use stem cells" to give someone a "new and better" penis, I'm going to go out on a limb and say that yes, in theory this should be possible if we can ever get good enough at controlling the growth and differentiation of stem cells. We're nowhere close to being able to do that right now (I think that right now we're working on much simpler things like helping people regrow tendon or muscle tissue) but I wouldn't be surprised if we could do it fifty years from now.

The issue that makes this so hard is that a penis is a pretty complicated organ. It's got lots of different tissue types in it and is structurally pretty complex. It would be more like growing a new hand or eye than a new tendon or nerve. It would require very fine control over the growth and differentiation process, shepherding the stem cells to grow into the types of tissues we want them to become, and to grow those tissues in the shapes that we want them to grow in. As has been alluded to above, this is really really hard to do. It should be theoretically possible since after all they did it once (when the person was a fetus) but we're nowhere close to being able to do it on demand.

It would probably (I think) be best to keep the existing penis and use it as a sort of framework for the new growth to occur around. That would avoid having to deal with removing the existing penis after the process was done, and I imagine it would probably make it easier to guide the process while it was happening. Whether this is being done to reconstruct a damaged penis or for cosmetic reasons (i.e. the patient wants a bigger dong) it would probably be easiest to use the existing tissue as the basis for new growth.

I can't think of anything that would make it impossible to grow a penis-inside-a-penis (since we're already waving our hands in the air quite vigorously I'll go ahead and say that it ought to be theoretically possible to grow a penis wherever we want) but I would imagine that it would be harder for a couple of reasons. One, the growing new penis would probably interfere with the structure and function of the existing one; you can't just shove a large object into a penis and expect it to keep working normally. Two, the existing penis would probably want to incorporate the new tissue into itself and so you would have to stop the two penises from getting sort of enmeshed with each other in a really weird and problematic way. So I can't imagine this ever being the preferred method of penis augmentation, though I can't say that it's theoretically impossible if we're assuming near-perfect control over tissue growth and differentiation.

Short version: yes, I think that it's theoretically possible. No, I don't think it's likely that we'll ever start doing it, at least not in exactly the way you proposed. No, I don't think we're likely to be able to do it at all anytime soon.
posted by Scientist at 5:34 PM on December 15, 2013 [1 favorite]


Is this potentially what you're thinking about?

There've been some animal studys involving regrowing the corpus cavernosum (i.e. the internal erectile tissue) using stem cells.

In a nut shell it involved, removing the cells from the corpus cavernosum of a Rabbit A, which left a completely decelled collagen matrix in the correct shape, this matrix was then implanted with stem cells from Rabbit B which then grew into a new corpus cavernosum (technically a CC-like structure), and this was then implanted into Rabbit B.

Here's article citations (I could only get abstracts, since I'm not on my university network right now, sorry : ( )

Article 1

Article 2

I know I read a pop sci type article about this somewhere (with MRI images even), but can't seem to find it again.

This is as close as we can get to a true transplantation for now.
posted by Chicoreus at 6:40 PM on December 15, 2013


Yes. Definitely not in my lifetime, though, not sure about yours.

We don't even know the right questions to ask, to get the information we need to even begin to test this stuff out, but a similar version of what you describe is pretty much the holy grail of tissue regeneration. Lots of attempts over the last few decades, no major progress the last time I checked the literature.
posted by hobo gitano de queretaro at 11:13 PM on December 15, 2013


Here's an analogy for you to consider that is probably more like how stem cell based regenerative medicine is likely to work in real life (as opposed to just growing bits and pieces in a big tank). No one in London alive today was alive in 1900 and yet, despite the fact that all the Londoners have died and been replaced with new people, we consider it to be the same London. Now cross out London and write in some organ, replace people with cells and 1900 to present with some period more appropriate to cell cultures.

We have already grown organs for implant using tissue culture and a scaffolding but it's a technique with limitations.
posted by Kid Charlemagne at 2:01 PM on December 16, 2013


quote 'Blazecock Pileon':
'It would probably be easier to grow a spare organ outside of the body in controlled lab conditions, in the functional equivalent of a test tube then introduce that new organ into the body through some surgical procedure.' [/quote]

Yes, perhaps, and there has been current progress in that regard as it pertains to and concerns human beings.

(See
http://www.medindia.net/news/Lab-Grown-Penis-Brings-Hope-for-Men-With-Erectile-Dysfunction-60682-1.htm

However, apparently I had been mistaken since I believed that in an actual procedure something would be done to the patient's current organ first (i.e. surgical detachment) prior to the successful implant of the new one which was grown inside a test tube (or a functional equivalent thereof). There doesn't seem to be any current research in that regard now let alone actual availability of procedure- (just like growing in situ organs)?
posted by Neutron12 at 5:07 PM on December 16, 2013


quote 'tchemgrrl':
'There are certain subcategories of tissues and cells for which I can imagine this happening at a small scale (the heart example above, for one), but one whole functional organ being made by putting stem cells near another whole functional organ as a template, no way. [/quote]

That wasn't exactly what I was talking about -(if you paid closer attention to my question)- not a functional organ being made by putting stem cells NEAR another functional organ (as a template) but rather via injection of stem cells (obtained either from bone marrow, adipose tissue or blood) into the male organ tissue. The stem cells would then differentiate and divide, eventually creating a brand new functional male organ which would replace the old one.
posted by Neutron12 at 9:50 AM on December 17, 2013


The stem cells would then differentiate

The question is where the stem cells get their cue to differentiate from, what cue is being sent, and what cells they are differentiating into. The signaling cues being sent in an adult — cues which manage a healthy adult — are much different from those in a developing fetus. It's not just injecting cells, but guiding their developmental paths to reconstruct the original organ.
posted by Blazecock Pileon at 1:27 PM on December 17, 2013


'Blazecock Pileon'

quote:
'The question is where the stem cells get their cue to differentiate from, what cue is being sent, and what cells they are differentiating into.' [/quote]

Well we (would) know which cue would be sent (to differentiate into male organ-type cells (different from those in other parts of the person's body)) and the cells to which they would differentiate to (male organ-type cells). The better question here obviously is where the stem cells would get their cue to differentiate from and I think the answer here is from the new microenvironment (a different part of the person's body) in which they would find themselves in
(and perhaps a lacking of male organ-type cells (if say we were to take a sample first)).
.

quote:
'It's not just injecting cells, but guiding their developmental paths to reconstruct the original organ. [/quote]

Yes, and I think we would need to develop specific advanced (medical) technology for that.
posted by Neutron12 at 10:32 AM on December 19, 2013


In response to your latest reply, this is where "theoretically possible" diverges sharply from "possible in practice". The reality of the situation is that we currently know very little about what causes stem cells to differentiate and grow in specific ways. We know a very few of the most fundamental basics of the process, but nothing even close to how to get stem cells to become a structurally complex organ composed of multiple tissues and tissue types. Not only do we not know how it happens in nature, we are also even further from knowing how to make it happen artificially. Making it happen artificially inside the very complex environment of an adult body, where there are undoubtably many hormones rushing around (doing important jobs that we wouldn't want to interfere with) which would act as unhelpful and contradictory signalers to our growing new organ, would involve yet another leap in terms of both understanding and control.

So while it ought in principal to be possible to do what you propose, it is nowhere close to being possible given our current levels of biological understanding and medical practice. Stem cells have to be guided in their development in extremely complex, time-sensitive, multi-factor, delicate ways if they are to develop into anything remotely resembling a functional body part. We currently don't even know what most of even the very most obvious factors even are, let alone how they work or how to manipulate them in the context of the overall developmental process.

It's a horrendously complex problem, and a very very active area of biological research right now. We're learning things, and some of the things we're learning are even useful, but being able to do something like grow a penis on an adult body is several orders of magnitude more complex than what we are currently capable of. My best non-expert estimate for when we'll be able to do things like that is somewhere between "fifty years from now" and "never", depending on how complicated it turns out to be. Right now we are so far from understanding the situation that we don't even really know how hard a problem it is. We know it's somewhere between "really, really hard" and "impossible". That's about where we're at.
posted by Scientist at 10:06 PM on December 19, 2013


Wait, I think I just understood your question finally. You are asking if you could simply inject stem cells into an existing penis and then let the existing penis guide the stem cells to become a new penis? If that's your question, the answer is a flat "No". Not possible, not even in theory.

What stem cells need to become a penis (absent the kind of near-godlike artificial manipulation I was talking about above) is a fetus and a womb, working together. A penis is not that. It is not even close to that. Also, the stem cells available in adult bodies do not have the ability to become any type of cell -- unlike fetal stem cells, they can only become any one of a limited selection of cell types.

What would almost certainly happen if you injected stem cells harvested from someone's fat or marrow into their penis and then let the body do it's own thing is that they would immediately be identified as being something that didn't belong there, whereupon they would be attacked by the immune system and destroyed. Or maybe they'd just sit there and not differentiate at all. Or maybe, if you were extremely unlucky, they would become a tumor. They would absolutely not grow into a new penis. It doesn't work that way.
posted by Scientist at 10:19 PM on December 19, 2013


>not a functional organ being made by putting stem cells NEAR another functional organ (as a template) but rather via injection of stem cells (obtained either from bone marrow, adipose tissue or blood) into the male organ tissue

That's what I meant, too. Cells injected into tissue are in close proximity to that tissue. The point I'm making is that proximity to already-differentiated tissue is not going to change anything. The chemical and mechanical cues required to make a whole, functional, complex organ--composed of a variety of tissues, with very specific architectures at the macro and micro scale, working together in close concert--are in no way present in an adult male.

Also, adult stem cells are not the same thing as fetal stem cells; although adult stem cells are capable of undergoing greater differentiation, they have gone through *some* differentiation; some avenues have been blocked. There's been some really interesting work done on de-differentiation which may bear some fruit someday, but even if that's theoretically possible, the differentiation cues that would be required are very rarely present in adult tissue.

>The better question here obviously is where the stem cells would get their cue to differentiate from and I think the answer here is from the new microenvironment

No. The environmental cues required to form a complex organ are not present in adult tissue. Stem cells are not magic.

There are small bits of this that might be possible, as I said upthread. Fixing damaged skin, improving blood circulation to damaged tissue by taking advantage of what we're learning about angiogenesis in tumors, replacing cells in decellularized tissue, figuring out the electrical cues required to get muscle cells to work together and increasing the amount of smooth muscle tissue. But injecting adult (or any!) stem cells into a healthy functioning organ and expecting it to template a copy of both all of the cells present in the organ and all the levels of structure, no.
posted by tchemgrrl at 6:09 AM on December 20, 2013


Scientist

quote: 'In response to your latest reply, this is where "theoretically possible" diverges sharply from "possible in practice".'

Well something being "theoretically possible" implies that it is not CURRENTLY possible in practice, not necessarily that it will NEVER be possible.

quote: "Wait, I think I just understood your question finally. You are asking if you could simply inject stem cells into an existing penis and then let the existing penis guide the stem cells to become a new penis? If that's your question, the answer is a flat "No". Not possible, not even in theory."

Actually I didn't mention anything about the existing penis guiding the development process of the new one. Rather, I implied that the new microenvironment (the existing male-organ tissue) in which the newly injected stem cells would find themselves in (if and after the injection of the cells into the male organ tissue) could serve as a natural impulse for the differentiation process (of the stem cells) to begin.


tchemgrrl


quote: "Cells injected into tissue are in close proximity to that tissue."

Well in such an instance they're already INSIDE the tissue so it's kind of redundant to say that they're in close proximity to it.

quotes "The chemical and mechanical cues required to make a whole, functional, complex organ--composed of a variety of tissues, with very specific architectures at the macro and micro scale, working together in close concert--are in no way present in an adult male. "-

"No. The environmental cues required to form a complex organ are not present in adult tissue. Stem cells are not magic."


Perhaps. If they're truly all absent, we would require something (or someone) like a child donor for the stem cells for the patient adult male.
posted by Neutron12 at 1:49 PM on December 20, 2013


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