Genital damage could be reversed after tissue is grown in laboratory

timesonline.co.uk - Mark Henderson, Science Editor

Damaged human genitals could eventually be restored to full function after penis tissue has been successfully grown in the laboratory and implanted into animals.

Scientists in the United States have replaced the erectile tissue of rabbits with a cultured version grown from cells in a dish, restoring normal sexual function and allowing the animals to father offspring.

The research is the most successful attempt yet to engineer penis tissue that works normally when implanted, and promises to have benefits for reconstructive surgery for human patients.

At present there are few options for men who suffer penis damage because of injury or cancer, or who are born with genital abnormalities. While the penis can sometimes be rebuilt for cosmetic effect, it is rarely possible to restore sexual function because erectile tissue cannot be replaced.

The research suggests that it should, ultimately, be possible to grow new erectile tissue using cells from the penis seeded on to a shaped 3-D lattice.

This could also be used to help men with certain forms of impotence caused by tissue damage. Another potential application is in cosmetic surgery for penis enlargement, though this will be limited by the risk of damage to a healthy organ.

The procedure is unlikely to be useful for female-to-male transsexuals, however, because the erectile tissue has been grown from penis cells. Stem-cell methods could provide a solution but further research would be needed.

Anthony Atala, director of the Wake Forest Institute for Regenerative Medicine in North Carolina, who led the research, said: “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.

“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 success of reconstructive surgery for damaged male genitals has been limited by the complex structure of the mammalian penis. Erections rely on a pair of chambers of sponge-like tissue, known as the corpora cavernosa penis (cave-like bodies of the penis), which fill with blood on sexual arousal to make the organ stiff.

These can be lost because of surgery for penile cancer or traumatic injury, or they can be small or absent because of congenital abnormalities. The corpora cavernosa can also atrophy in some forms of impotence, for example among prostate cancer patients who have no erections for a long time after surgery.

Reconstructive techniques generally rely on rebuilding the penis using skin and tissue from the arm or leg and rolled up around the urethra. This can then be attached to nerves to provide some sexual sensation, and stiffened for intercourse by inserting a silicone prosthesis.

In the research, which was published in the journal, Proceedings of the National Academy of Sciences, Dr Atala’s team first removed smooth muscle cells and endothelial cells, which line blood vessels, from the erectile tissue of rabbit penises.

These were then injected into a 3-D scaffold and cultured so that they multiplied along it. The tissue-covered scaffold was then implanted back into the rabbits’ penises, from which erectile tissue had been excised.

The results were an improvement on previous experiments, in which the Wake Forest team had managed to create erectile tissue with about 50 per cent of normal function. A new technique was used to seed the scaffold with smooth muscle cells twice, allowing it to hold six times as many as was previously possible.

The extra smooth muscle cells seem to be important to restoring sexual function because they play an important role in erections. The muscle cells relax during arousal, triggered by the release of nitric oxide from endothelial cells, allowing blood to engorge the penis.

“Increasing the density of smooth muscle cells led to normal erectile pressures within the tissue,” Dr Atala said. “These results are encouraging. They indicate the possibility of using laboratory-engineered tissue in men who require reconstructive procedures. A lack of erectile tissue currently prevents us from restoring sexual function to these patients.”