The first 3D printed organ -- a liver -- is expected in 2014

Printed tissue could vastly improve drug testing

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Currently, there are about 120,000 people on the organ waiting list in the U.S., and even those who receive a donated organ face the prospect of ongoing medical challenges because of organ rejection issues. However, if a patient's own stem cells could be used to regenerate a living organ, rejection would become moot.

Research into whole organ regeneration currently receives less than $500 million in funding a year in the U.S., compared to $5 billion for cancer research and $2.8 billion for HIV and AIDS, the Methuselah Foundation said in its contest announcement. "Regenerative medicine is the future of healthcare, but right now the field is falling through the cracks," said Methuselah CEO David Gobel.

Organs on a chip

While it may be a decade or more before human trials for organ transplants are approved by the FDA, the creation of organ tissue still holds the prospect of revolutionizing medicine.

Printing out sustainable organ tissue could allow pharmaceutical companies to develop and test drugs on human and not animal organs. Using human tissue yields more accurate results.

Researchers are now experimenting with laying down a thin layer of human tissue from any number of organs for pharmaceutical development. The process is known as creating an "organ on a chip" or a "human on a chip."

Scientists have for years been able manually grow thin skin tissue for temporary skin grafts that act as a type of bandage while the body heals itself. However, 3D printing has advanced that process.

Instead of the arduous task of manually laying down cells, 3D printing automates the process in an exact and repeatable way using a syringe on the end of a robotic mechanism guided by computer-aided design (CAD) software.

"Using 3D printing has given us the reproducibility and the automation needed to scale up," said Jordan Miller, assistant professor of bioengineering at Rice University. Miller recently helped open a microfabrication lab at Rice University after spending years in a similar lab at the University of Pennsylvania's department of bioengineering.

The key to creating viable, living tissue is first understanding how it works.

As much as scientists know about the human body, the way tissue is formed at the cellular and sub-cellular level is still in large part a mystery. There are about 40 different cell types that make up a human liver, including Kupffer cells for removing debris from the blood, stellate cells for regenerating tissue that has died or been injured, and sinusoidal endothelial cells, which make up the interior surface of blood vessels and lymphatic vessels.

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3D printed breast tissue could someday help to reconstruct breasts in cancer survivors. (Image: TeVido BioDevices)

"It's a complicated challenge," Miller said. "We don't know all the structures in the body. We're still learning. So we don't know to what extent we need to reconstitute all those features. We have some evidence that we may not need to re-create all those functions."

Miller and others believe that if they reconstitute a portion of tissue, even if it's not complete, there's a good chance it will continue to grow into a fully functioning organ once implanted in the body.

"We've had some success in thin tissues, skin, corneas and bladder," Miller said. "It gets more complicated when you're talking about biochemical functions in the liver or kidney. Those are fragile cells that don't do well in labs. Some of the most interesting cells we want to print are hardest to keep alive."

Instead of printing cells 10 layers deep, as might be needed for a skin graft, researchers are attempting to print cells 5,000 or 10,000 layers deep, Miller said.

Just add sugar and water, and voila -- blood vessels

In order to print thick tissues, scientists must also be able to create the vascular system needed for sustainability.

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