A group of Wake Forest University researchers has grown fully functional penile erectile tissue in rabbits, using a procedure that one day may be used to treat erectile dysfunction in men.
Dr. Anthony Atala said Monday that he has been researching growing the tissue for 18 years. In earlier experiments, the researchers were able to restore about 50 percent of the male rabbit's function.
But in results released Monday in the online edition of the Proceedings of the National Academy of Sciences, the researchers were able to fully restore the sensitive part of the penises of lab rabbits, giving them the ability to have sex and even produce offspring.
The research was done at Wake Forest University Baptist Medical Center's Institute for Regenerative Medicine. Rabbits were used because of the similarity of their penile cells compared to humans, Atala said. In the experiments, when the animals with engineered tissue mated with females, sperm was detected on vaginal swabs in eight of 12 samples, and four of the female rabbits were impregnated.
The research marks the latest breakthrough for the regenerative center and Atala, who was recruited to Wake Forest from Harvard University in 2004. Since then, the number of scientists, researchers and technicians on the center's staff has almost quadrupled, and numbers almost 100 people now, said Karen Richardson, a Wake Forest Baptist spokeswoman.
In 2005, scientists at the Regenerative Medicine Center announced that they had grown fat, muscle and bone cells using stem cells isolated from human skin. The next year, researchers had engineered tissues to rebuild human bladders. To date, those bladders have been implanted in almost 30 patients.
Atala said that growing skin tissue was relatively simple because the tissues are flat. Hollow organs such as the bladder are harder because they are more complex.
He said the most complex and difficult tissues to grow in the lab are for solid organs such as the penis, in part because they require so many more cells than other types of tissues in order to have adequate blood supply.
Atala said the department will now work to see if the results can be replicated using human penile tissue.
"We're going to be doing that experimentally at our center," he said.
If those experiments are successful, they could help address a wide variety of problems.
The tissue could be used to help improve the size of males with congenital anomalies resulting in small penises. The restored tissue could also potentially help men whose penises have been damaged through surgery or by injury.
Atala said there may also be a benefit of growing new tissue for the up to 25 percent of men with erectile dysfunction who do not respond to drug treatments.
"A lack of erectile tissue currently prevents us from restoring sexual functions to these patients," he said.
Atala said that he knows there will be interest in the results from some who may be interested in the potential for male enhancement. Atala said he's more interested in the potential medical benefits of the research than the cosmetic ones.
"There are so many medical conditions that could benefit," he said.
Using the engineered penile tissues would require surgery, which always involves some risk, Atala said.
"You have to weigh the risks," he said.
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