Researchers at Children's Hospital Boston report an important advance in tissue engineering of the penis, raising hopes that men with severe impotence - due to penile trauma, surgery, cancer, congenital malformations or other conditions - may someday be able to regain sexual function. These findings, presented to the American Urological Association, have implications for men who need reconstruction of the penis, and for men whose penis is intact but has suffered nerve damage - such as men who have undergone radical surgery for prostate cancer.
Although the body of the penis can be grown in the lab through tissue engineering using smooth muscle cells, the organ needs a working network of nerves in order to achieve erection and function sexually. This animal study, led by Anthony Atala, MD, director of Tissue Engineering at Children's Hospital Boston, showed that implantation of engineered tissue made of collagen can coax nerves to regenerate in the penis.
The investigators cut the cavernosal nerves - the two bundles of nerves innervating the penis - in 90 rats. At the injury site, they implanted either a graft of the rats' own nerves, or a graft made from collagen, a natural protein found in connective tissue. Some severed nerves were left untreated. The collagen grafts had been engineered to form a channel shape, similar to the natural sheath of a nerve, and follow-up studies three months later showed that the rats' own nerve cells had regenerated and infiltrated this "scaffolding" material. "We used the body's own healing abilities to create the tissue," explains Atala.
The degree of nerve regeneration with the collagen grafts equaled that of both normal, undamaged nerves, and the grafts consisting of the rats' own nerves. The severed nerves that were left untreated showed no signs of regeneration.
Atala's lab previously showed that the tissue making up the body of the penis can be successfully grown in the lab, and successfully used to reconstruct the penises of rabbits that had part of the organ surgically removed. This new study takes penile reconstruction a step further; showing that the nerves required for erectile function can be induced to grow through tissue engineering.
"Right now we can do partial penile repair, but in order to do complete replacements, we need to make sure all the parts are there, including the nerves," Atala said. "This research takes us one step closer." Future work will attempt to tissue-engineer a complete penis, growing the body of the organ and providing it with a functioning set of nerves.
