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If scientists can help Peter Cottontail get an erection, there may be hope for the other flaccid Peters of the world.

Researchers at Wake Forest University in North Carolina have grown functional rabbit penises that allow male rabbits to mate, ejaculate and procreate. The results of their experiment were published in the latest issue of the Proceedings of the National Academy of Sciences.

The research team took small pieces of tissue and isolated cells from them – both smooth muscle cells (which make the penis's tissue relax during an erection) and endothelial cells (which line blood vessels).

They put the cells in 3-D scaffolds shaped like penises and, over the span of several weeks, grew them and then replaced 12 rabbits' penises with the organs they had engineered.

It didn't take long for lead investigator Anthony Atala, director of the Institute for Regenerative Medicine at Wake Forest University's Baptist Medical Center, to see the success of the experiment spring to life.

The rabbits' mating habits were observed one, three and six months after they received the implants. Within just a minute of being placed near a female rabbit, all the males who received transplants tried to mate with them. Eight of the frisky males successfully ejaculated (researchers took vaginal swabs of the females to check for semen) and four were able to impregnate the female rabbits.

Dr. Atala has made a name for himself as a regenerative medicine wizard, having constructed several fully functional bladders a decade ago, and is also trying his gifted hands at growing everything from livers to breasts. But growing a penis was a taller order – he toiled away at it for 18 years.

“This is a solid organ which is actually hard to engineer – the most complex to engineer,” he said.

Dr. Atala wasn't spurred on to take up this challenge by the millions of men who suffer from sexual dysfunction, but instead from much younger patients, who he has treated clinically as a pediatric urologic surgeon.

“I was working with babies born with inadequate genitalia. That was the true inspiration for the work,” he said.

Dr. Atala says if the rabbit procedure can eventually be replicated in humans, it could be used to give new penises to penile cancer patients or men who have suffered major penile injuries.

But, of course, he understands men who have trouble keeping it up may also be interested in such a development.

At the moment, the most popular treatment option for erectile dysfunction is the little blue pill: Viagra. But 25 per cent of men who suffer from erectile dysfunction don't respond to it or similar medications, Dr. Atala said.

In those cases, there are other treatments such as vacuum devices and penile injections.

The only surgical option is a penile implant, though Dr. Atala says its lack of functionality and the fact that you have to manually “turn it on” leaves many men yearning for something better.

Penile implants come in various forms with wide-ranging prices, said John Aquino, a doctor who works at the Ontario Men's Health clinic in Toronto.

“You have your Hyundai and you have your Lexus,” he said.

The more expensive models involve an intricate system of tubes connected to a reservoir. In order to achieve an erection, a man must use a pump implanted in his scrotum or thigh to fill his penis with liquid.

On the other end of the scale are the more common and cheaper plastic types.

“It's something you have to activate – it's basically a plastic rod that gets put in,” Dr. Atala said. “It's not a natural option, basically.”

Dr. Aquino said 75 per cent of the men that come to the clinic suffer from erectile dysfunction. He encourages his patients to try the least-invasive options first before getting on the operating table.

“I will discourage them from going for the surgical option – I just don't medically feel it's in their best interest,” he said.

Understanding that the road to bringing the penile engineering procedure to humans is littered with obstacles (Dr. Atala still has to run many safety studies before he can start such experiments), Dr. Aquino doesn't expect penile transplants will be an option for his patients any time soon.

“That sounds pretty Star Trek for me,” Dr. Aquino said. “I'm not going to hold my breath during my career.”