One day artificial penis tissue could be grown to help men, new findings in rabbits now suggest.
After implantation with replacement tissue, lab rabbits that once had damaged penises had working organs and could produce offspring.
"Further studies are required, of course, but our results are encouraging and suggest that the technology has considerable potential for patients who need penile reconstruction," said researcher Anthony Atala, director of Wake Forest University Baptist Medical Center's Institute for Regenerative Medicine in Winston-Salem, N.C.
Such methods could potentially aid men who just want to enhance their normal penises, rather than repairing any damage.
"Our intent and the goal of our work is to provide a solution for men who need penile erectile tissue for medical reasons," Atala told LiveScience. "Of course, you cannot control how the technology is used in terms of what patients want."
The real hope is "that patients with congenital abnormalities, penile cancer, traumatic injury and some cases of erectile dysfunction will benefit from this technology in the future," Atala said.
The challenge
Reconstructing the spongy erectile tissue in damaged or diseased penises has traditionally been a challenge because of its complex structure and the intricate cellular interactions needed to make it work properly. A number of different kinds of surgery have been attempted — often procedures with multiple stages that can involve a silicone penis prosthesis — but natural erectile function is generally not restored.
"There is nothing more devastating for a surgeon than to be in the operating room and to have no tissue to give a patient who needs it," Atala said. "We want to find a solution to that dilemma."
The researchers sought to solve this problem by engineering replacement tissues in the lab. They first harvested the kinds of cells that line blood vessels — smooth muscle cells and endothelial cells — from the erectile tissue of rabbits. During an erection, the endothelial cells release nitric oxide, which makes the smooth muscle tissue relax, permitting an influx of blood into the penis.
After letting the cells multiply, millions of them were injected into scaffolds made from rabbit penises stripped of all their cells with detergents. These scaffolds provided support as the injected cells developed. After implanting the scaffolds in the penises of 12 male New Zealand White rabbits, organized tissue with vessels began to form as early as one month afterward.
"In much of our work, we have learned that 'nature knows best,' and this is certainly true with decellularized organs — they are ideal to support cells as they multiply and as tissue develops," Atala said.
The cells were injected into scaffolds on two separate days, enabling them to hold nearly six times as many smooth muscle cells as in the prior research, which the scientists believe was a major key to success. Tests showed that blood pressure and flow within the erectile tissue was normal and that veins drained normally after erection.
Just like rabbits
All rabbits with the bioengineered penises were just as active as normal rabbits — they tried sex within a minute of introduction to females. Swabs from the females held sperm in eight of 12 instances and four of the females became pregnant, delivering healthy pups.
"Although many scientists shy away from doing research in this critical area, these are all very important body structures — especially if you're a man," said stem cell scientist Robert Lanza, chief scientific officer of Advanced Cell Technology in Worcester, Mass., who did not take part in this research. "Certainly no one wants to be known as the 'penis doctor' — so bravo to Tony for having the courage to develop this reconstructive procedure, which could potentially help thousands of people suffering from congenital anomalies, penile cancer, and traumatic injuries. This is the most complete functional replacement of erectile tissue reported to date."
If the scientists do try and help people with this research, naturally they will not use rabbit cells with men.
"We would take a small sample of a patient's erectile tissue, extract the cells we need and multiply them in the laboratory," Atala explained. "The resulting tissue would be a perfect match for the patient.
Future research also might not depend on scaffolds made from decellularized penises. Instead, Atala and his colleagues could print three-dimensional scaffolds out from materials such as collagen. "We can print structures to make them to order as needed," he said.
"Regenerative medicine isn't science fiction as many people believe — it is benefiting patients right now and has the potential for even wider use in the future," Atala added.
The scientists detailed their findings online November 9 in the Proceedings of the National Academy of Sciences.
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