Tissue Engineering a Functioning Penis
Rabbits with an engineered penis can reproduce.
In a unique feat of tissue engineering, scientists from Wake
Forest University Baptist Medical Center have created penile erectile tissue
and implanted it into male rabbits, allowing the animals to, well, go at it
like rabbits.
Researchers implanted scaffolds seeded with cells from rabbit penile tissue. One month later, organized tissue with blood vessels began to grow. Tests showed that the new tissue functioned like a normal penis, with
normal blood flow and drainage of the veins. The rabbits even fathered
offspring. The research was published today in the Proceedings of the National
Academy of Sciences.
“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,” said Anthony Atala, M.D., director of
Wake Forest’s Institute for Regenerative Medicine, in a statement. “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.”
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During an erection, sponge-like tissue called copora cavernosa fills with blood. This tissue can be damaged by disease, injury, or lack of use, such as after prostate surgery. But according to a press
release from Wake Forest, fixing these structures has been a challenge because of “the tissue’s unique structure and complex function.” Also, “there is no replacement
for this tissue that allows for normal sexual function. Various surgeries have
been attempted, often multi-stage procedures that can involve a silicone penile
prosthesis, but natural erectile function is generally not restored.”
Atala’s team has previously engineered replacement bladders,
which have been implanted in close to 30 people to date. The researchers used
similar engineering techniques in the new research. According to the release:
The scientists first
harvested smooth muscle cells and endothelial cells, the same type of cells
that line blood vessels, from the animals’ erectile tissue. These cells were
multiplied in the laboratory. Using a two-step process, the cells were injected
into a three-dimensional scaffold that provided support while the cells
developed. As early as one month after implanting the scaffold in the animal’s
penis, organized tissue with vessel structures began to form.
The cells were
injected into scaffolds on two separate days, enabling them to hold almost six
times as many smooth muscle cells as in the previous studies – which the
scientists believe was a key to success. During an erection, it is the
relaxation of smooth muscle tissue that allows an influx of blood into the
penis. The relaxation is triggered by the release of nitric oxide from endothelial
cells.
