Progress in Rebuilding Penile Erectile Tissue

Nov. 9, 2009 -- Wake Forest University researchers say they've found a way to replace penile erectile tissue and function in animals.

Reporting online in the Nov. 9-13 issue of the Proceedings of the National Academy of Sciences, researchers from the Wake Forest Institute for Regenerative Medicine say their tissue engineering methods could one day help reconstruct and restore function to damaged or diseased penile tissue in men.

"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," says Anthony Atala, MD, director of the institute and co-author of the study. "Our 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."

The authors say they've had success using cells from rabbits to grow replacement penile tissue in the laboratory for the animals. But repairing diseased or damaged penile tissue, they say, has been a challenge because of its complex function and structure.

There's currently no replacement for the tissue. A number of surgeries have been tried, but natural erectile function has generally not been restored, the researchers say.

Engineering Erectile Tissue

At Wake Forest, scientists set out to find a solution by working to engineer replacement tissue in the laboratory. In an earlier study, they engineered short segments of erectile tissue for rabbits that had 50% of the function of native tissue.

First the scientists harvested smooth muscle cells and cells that line blood vessels (called endothelial cells) from the rabbits' penile tissue. The cells were multiplied in the lab, then seeded onto a three-dimensional scaffold that provided support during tissue growth.

As early as a month after implanting the scaffold, organized tissue began to form in rabbit penises, the researchers say. Six times as many smooth muscle cells were seeded onto the scaffolding compared to their previous studies, the researchers say, which they contend was a key to success.

"Increasing the density of smooth muscle cells led to normal erectile pressures within the tissue," says Atala.

Testing showed that blood vessel measures of erectile function were comparable to normal erectile tissue. When the rabbits' with re-engineered penises mated with females, vaginal swabs contained sperm in eight of 12 instances, and four of 12 females became pregnant.

Rabbits with the engineered penises attempted to have sex with females within a minute of the time they met. Rabbits that had not been given the implanted tissue did not attempt copulation, in most cases, and there was no evidence of sperm on any swabs.

Atala says the results are encouraging and "indicate the possibility of using laboratory-engineered tissue in men" who need reconstructive procedures. Currently, a lack of erectile tissue prevents scientists from restoring sexual function to such men, the researchers say.

Atala worked with researchers Kuo-Liang Chen, MD, at China Medical University Hospital in Taiwan, Daniel Eberli, MD, University of Zurich in Switzerland, and James Yoo, MD, PhD, at Wake Forest. Both Chen and Eberli were at Wake Forest when the research was done.