Lab-Grown Penises Are Almost Ready For Human Testing

It was a big weekend in reproductive reconstruction news: The Lancet revealed that last year, a 36-year-old woman in Sweden became the first recipient of a womb transplant to give birth to a baby post-op, while The Guardian reported that researchers at the Wake Forest Institute for Regenerative Medicine are making progress on bioengineered penises that they hope will be FDA-approved for human testing within the next five years.

Currently, penis reconstruction — or construction, in the case of sex-change surgery — typically involves covering a prosthetic implant with skin from another area of a person's body, such as the thigh, forearm, or abdomen. (Those who are undergoing sex reassignment surgery can also opt for a type that creates a penis from a clitoris, which is first enlarged using sex hormones.) Attempts to transplant real penises are few and far between: The actual procedure isn't terribly difficult, but risk of rejection is high, since the body's immune system treats the new penis as if it were a foreign attacker. The problem with the skin-graft-over-prosthesis procedure, though, is that skin from non-genital areas of the body (obviously) lacks erectile tissue: To become erect, those who undergo this surgery have to rely on inserted pumps or rods.

That's why the Wake Forest team is innovating a new penis reconstruction method, through which cis men whose penises have been injured (including combat veterans) or who were born with congenital abnormalities will hopefully be able to achieve erection naturally. Here's how it works: Scientists remove cells from a donor penis, so all that's left is a collagen "scaffold" onto which they "seed" cells taken from what remains of the penis recipient's genitalia. (Unfortunately, the procedure won't be applicable to trans men seeking sex reassignment, as they don't already have erectile cells.)

Smooth muscle cells will be seeded first, and will go on to grow smooth muscle tissue over the penis-scaffold; this type of tissue relaxes when a penis-owner is aroused, letting blood flow into the penis. Next up will be endothelial cells, which line the blood vessels that form an erection. Once the penis has fully "grown," it will be transplanted onto the recipient. This procedure has already proven successful in rabbits, and now, researchers are hopeful that they'll receive the go-ahead to start testing on men in the next few years. Project collaborator James Yoo, MD, PhD, told The Guardian: "As a scientist and clinician, it's this possibility of pushing forward current treatment practice that really keeps you awake at night."