CNN.com
The emerging process of 3-D printing, which uses computer-created
digital models to create real-world objects, has produced everything
from toys to jewelry to food.
Soon, however, 3-D printers may be spitting out something far more complex, and controversial: human organs.
For years now, medical
researchers have been reproducing human cells in laboratories by hand to
create blood vessels, urine tubes, skin tissue and other living body
parts. But engineering full organs, with their complicated cell
structures, is much more difficult.
Enter 3-D printers, which
because of their precise process can reproduce the vascular systems
required to make organs viable. Scientists are already using the
machines to print tiny strips of organ tissue. And while printing whole
human organs for surgical transplants is still years away, the
technology is rapidly developing.
"The mechanical process isn't all that complicated. The tricky part is the materials, which are biological in nature," said
Mike Titsch, editor-in-chief of 3D Printer World,
which covers the industry. "It isn't like 3-D printing plastic or
metal. Plastic doesn't die if you leave it sitting on an open-air shelf
at room temperature for too long."
Lawrence Bonassar, a professor of biomedical engineering at Cornell
University, with an artificial ear made via 3-D printing and injectable
molds.
The idea of printing a
human kidney or liver in a lab may seem incomprehensible, even creepy.
But to many scientists in the field, bioprinting holds great promise.
Authentic printed organs could be used for drug or vaccine testing,
freeing researchers from less accurate methods such as tests on animals
or on synthetic models.
Then there's the hope
that 3-D printers could someday produce much-needed organs for
transplants. Americans are living longer, and as we get deeper into old
age our organs are failing more.
Some 18 people die in the United States each day waiting in vain for transplants because of a shortage of donated organs -- a problem that
Anthony Atala, director of the Wake Forest Institute for Regenerative Medicine and a pioneer in bioprinting, calls "a major health crisis."
An 'exciting new area of medicine'
Bioprinting works like
this: Scientists harvest human cells from biopsies or stem cells, then
allow them to multiply in a petri dish. The resulting mixture, a sort of
biological ink, is fed into a 3-D printer, which is programmed to
arrange different cell types, along with other materials, into a precise
three-dimensional shape. Doctors hope that when placed in the body,
these 3-D-printed cells will integrate with existing tissues.
The process already is seeing some success. Last year a 2-year-old girl in Illinois, born without a trachea,
received a windpipe built with her own stem cells. The U.S. government has funded
a university-led "body on a chip" project
that prints tissue samples that mimic the functions of the heart,
liver, lungs and other organs. The samples are placed on a microchip and
connected with a blood substitute to keep the cells alive, allowing
doctors to test specific treatments and monitor their effectiveness.
"This is an exciting new
area of medicine. It has the potential for being a very important
breakthrough," said Dr. Jorge Rakela, a gastroenterologist at the Mayo
Clinic in Phoenix and a member of the
American Liver Foundation's medical advisory committee.
One of Organovo's engineers oversees the construction of a vascular tissue construct on a NovoGen MMX bioprinter.
"Three-D printing allows
you to be closer to what is happening in real life, where you have
multiple layers of cells," he said. With current 2-D models, "if you
grow more than one or two layers, the cells at the bottom suffocate from
lack of oxygen."
To accelerate the development of bioprinted organs, a Virginia foundation that supports regenerative medicine research
announced in December it will award a $1 million prize for the first organization to print a fully functioning liver.
One early contender for the prize is
Organovo, a California start-up
that has been a leader in bioprinting human body parts for commercial
purposes. Using cells from donated tissue or stem cells, Organovo is
developing what it hopes will be authentic models of human organs,
primarily livers, for drug testing.
The company has printed
strips of human liver tissue in its labs, although they are still very
small: four by four by one millimeter, or about one-fourth the size of a
dime. Each strip takes about 45 minutes to print, and it takes another
two days for the cells to grow and mature, said Organovo CEO Keith
Murphy. The models can then survive for about 40 days.
Organovo has also built models of human kidneys, bone, cartilage, muscle, blood vessels and lung tissue, he said.
"Basically what it
allows you to do is build tissue the way you assemble something with
Legos," Murphy said. "So you can put the right cells in the right
places. You can't just pour them into a mold."
Ethical concerns
Not everyone is comfortable with this bold new future of lab-built body parts, however.
A research director at
Gartner Inc., the information-technology research and advisory firm,
believes 3-D bioprinting is advancing so quickly that it will spark a
major ethical debate by 2016.
A 3-D printer at Cornell University produces an artificial ear.
"Three-D bioprinting
facilities with the ability to print human organs and tissue will
advance far faster than general understanding and acceptance of the
ramifications of this technology,"
Pete Basiliere said in a recent report.
"These initiatives are
well-intentioned, but raise a number of questions that remain
unanswered," Basiliere added. "What happens when complex 'enhanced'
organs involving nonhuman cells are made? Who will control the ability
to produce them? Who will ensure the quality of the resulting organs?"
Bioprinted organs are also likely to be expensive, which could put them out of reach of all but the wealthiest patients.
Murphy said Organovo
only uses human cells in creating tissues, and doesn't see any ethical
problems with what his company is doing.
"People used to worry
about doing research on cadavers ... and that dissipated very quickly,"
he said. "We don't think there's any controversy if you're producing
good data and helping people with health conditions."
Most experts,
including Wake Forest's Atala,
don't think we'll see complex 3-D-printed organs, suitable for
transplants, for years if not decades. Instead, they believe the next
step will be printing strips of tissue, or patches, that could be used
to repair livers and other damaged organs.
Organovo's NovoGen MMX bioprinter is small enough to fit into a cabinet.
"We are very eager to
put pieces of tissue to work for surgical transplants," said Organovo's
Murphy, who hopes his company will be ready to begin clinical trials
within five years.
Of course, any use of
3-D-printed tissue in surgical procedures would require approval by the
U.S. Food and Drug Administration. That review process could take up to a
decade.
By then, the notion of a
surgeon putting a 3-D-printed kidney into a patient may not seem so
bizarre. Then again, this swiftly evolving technology may create new
moral conundrums.
"The ethical questions
are bound to be the same concerns we have seen in the past. Many major
medical breakthroughs have suffered moral resistance, from organ
transplants to stem cells," said Titsch of 3D Printer World.
"Will only the rich be able to afford it? Are we playing God? In the end, saving lives tends to trump all objections."
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