Friday Weird Science: Let’s go at it like rabbits

It was ALL OVER the internet (check out Observations of the Nerd for some particularly good coverage), of course you know I HAD to blog it, right? Sadly, it got taken over in the first week by the Oxytocin weeks of DOOM (oh, it was doom, there were a lot of late nights that week, Sci can’t give up her day job, you know).
But here I am. And here it is. And for those media outlets that complained that you couldn’t find the paper in the PNAS issue and acted all mysterious, Sci got the paper. Cause Sci’s got CONNECTIONS. Connections which involve emailing the PR people who put out the press release. Simple, yet effective! May I recommend it to you sometime.
Chen et al. “Bioengineered corporeal tissue for structural and functional reconstruction of the penis.” PNAS, 2009.

(By the power of SCIENCE, some day this could be you)
(Also, some of the pics are probably NSFW for those of you who have coworkers sensitive to scientific depictions of the anatomy of the penis. You were warned.)

So before we go into just what they did exactly, let’s go into the anatomy of the penis. This will be a quick review, for most on how erections form and the anatomy of the penis, see my previous post on the topic.

This would be the human version, and what you need to note here are the things they’ve sort of drawn in this light lavender color. Those are the corpus cavernosa, long tube structures that are spongy in texture. During the formation of an erection, blood flows into the corpus canverosa and muscles and veins contract to keep it in there, causing them to stiffen and the whole thing to rise. One of the most common causes of erectile dysfunction in men is when the corpus cavernosa is problems with the arteries and veins going in and out. The veins will sometimes lose their plasticity, allowing blood to flow back out and the erection to lose it. This is obviously a problem.
There are other problems that can occur with the corpus cavernosa. For example, a lot of penile injuries can result in injuries to the corpus cavernosa and long-term complications. Many of these injuries require reconstructive surgery, but that’s hard to do, as it’s not like you can just graft any old piece of tissue on to your penis and get it to work. Muscle is muscle pretty much anyway, and skin is always skin, but you only have two corpus cavernosa, and you kind of need both.
So this study didn’t set out to reconstruct the PENIS. It set out to reconstruct the corpus cavernosa. Basically, they took out the corpus cavernosa of 12 very unhappy boy rabbits. They then took some of the original tissue, and put it onto a matrix. This matrix is the thing that made Dr. Atala (the final author on this study) famous, and which will probably provide the groundwork for a lot of future tissue engineering. It’s basically a cell photocopier. You put the cells from the rabbit on the matrix, which is basically in the shape of what you want to come up with. Add the right kinds of growth factor. The cells grow. The overall method looks like this:

Harvest the smooth muscle cells and endothelial lining from the rabbit. Grow cells. Seed the cells on the matrix with growth factors to make sure they grow into the right shape.

You can see here the matrix on which they seeded the cells (on the right). Inserted into the matrix, the cells grew into the same shape as those of the original rabbit corpus cavernosa (left).

You can see here the stained pictures of the muscle cells in a natural rabbit penis and the newly reconstructed version. The smooth muscle cells look good and almost entirely normal. Reinsert the result in a gratified rabbit…
And it worked! They performed studies showing that the smooth muscle and endothelial cells were functional and responded electrically like naturally grown counterparts, contracting in response to phenylephrine and electrical stimulation, and relaxing in response to sodium nitroprusside and carbachol. Implantation was successful (the tissue wasn’t rejected because it was the rabbit’s native tissue, after all), and the tissue was even successfully revascularized and got its own blood supply.
But the big test: Could they use it? YES THEY COULD. The rabbits appeared to know right away that things were better, and started going at it…like rabbits…within a minute of introduction to a receptive female. Not only that, it REALLY worked. Of the total of 12 rabbits that underwent the procedure, 8 ejaculated successfully into the female, and 4 became daddies! It looks like this technique ain’t just for looks.
What really geeks Sci out is the cell matrix on which the scientists were able to grow tissue. So far, it’s worked for fairly simple kinds of cells, like smooth muscle cells (which make up the corpus cavernosa), and the endothelial cells with cover the smooth muscle. It appears that what is limiting the work with the matrix right now is how many types of cells you can grow on it at once. After all, there aren’t a lot of things in the body that are as simple as a corpus cavernosa. Hopefully, soon, it will be able to work with more complicated things like the cell layers that make up skin.
So what’s the point? When the study came out, Sci heard a lot of things about how we’ll have penis enlargement before we cure cancer. Yeah…probably. But this is also useful for things other than penis enlargement and erectile dysfunction. It can be used for reconstructive surgery following traumatic injury. Even if it doesn’t work, it will still look better than peeing through a plastic tube for the rest of your life. And the technique might even be able to work for transmen, people who are born physically female who wish to become male. A combination of hormones can enlarge the clitoris somewhat, but only a technique like this could produce the possibility of a real, possibly even “functioning” penis (not releasing sperm, but possibly capable of erection). So it isn’t just for enlargement, though once they CAN use it for enlargement, the possibilities are probably endless. Remember that woman with the breasts she had enlarged to be over 1 gallon of silicone each? Wait until you see the guy with the three foot penis!