Progress in Rebuilding Penile Erectile Tissue

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.

By Bill Hendrick
Reviewed by Louise Chang
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