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Tissue engineers grow penis in the lab.
19:00 11 September 2002
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Researchers have grown lengths of the corpus cavernosum in the lab
In
a remarkable feat of
tissue engineering, major parts of the penises of
several
rabbits have been replaced with segments grown in a lab from
their own cells. The animals were able to use the reconstructed organs
to mate.
The
next step is to try to recreate the entire organ from scratch. The
technique could make it possible to reconstruct the penises of men who
have suffered injuries or those of children born with genital
abnormalities.
"If
you have a child born with ambiguous genitalia, it''s a life-changing
event," says Anthony Atala of Harvard Medical School, whose team
carried out the work.
It
could also provide an alternative to the crude methods currently used
to enlarge the organ, such as injecting fat cells or cutting the
penis''s suspensory ligament and "pulling out" more of the internal
part. Instead, a patient would have penile cells removed by a doctor
and, a few weeks later, the organ or parts of it grown using the cells
could be surgically implanted.
More complex
While
the particular nature of the research is likely to attract much
attention, it is also one of the most impressive attempts at tissue and
organ engineering to date. "The penis is more complex than any of the
organs we have engineered so far," says Atala, whose team has already
created fully functional bladders that may soon be implanted in people.
The penis is more difficult to recreate because it has more functions and, unlike the bladder, is also a solid organ.
It
consists of three main cylinders, encased in an outer layer of
connective tissue, skin, blood vessels and nerves. The two biggest
cylinders, made of spongy material that swells during an erection, are
the corpora cavernosa. The third tube encases the urethra.
Of
those structures, the corpus cavernosum is the most challenging to
replace or reconstruct. It contains specialised muscle and endothelial
cells - the cells that line blood vessels - and its structure is hard
to mimic. Yet this is the part that Atala has been able to grow.
Half pressure
His
team first extracted three-dimensional scaffolds of collagen from the
erectile tissue of rabbits. They also took samples of the specialised
muscle and endothelial cells from penises of each of the rabbits
destined to receive the implants.
These
cells were grown separately at first, and then added to the collagen
matrix in the appropriate proportions. After a few days more growth,
the result resembled real erectile tissue.
Next,
Atala removed the corpora cavernosa from almost theire length of
the exterior part of the penises of 18 rabbits, leaving the nerves and
urethra intact. He then replaced them with the engineered erectile
tissues. Because the tissues were grown from the rabbits'' own cells,
there was no problem with immune rejection.
Once
they had recovered from the surgery, the rabbits attempted to have sex
within 30 seconds of being put in a cage with a female. "They were able
to copulate, penetrate and produce sperm," Atala told New Scientist.
More
detailed studies revealed that the penises generated about half of the
normal pressure of an erect penis. "It''s analogous to the penis of a
60-year-old man, versus that of a 30-year-old," says Atala. Details of
the work will be published in the October issue of The Journal of
Urology.