BUILDING ORGANS IN 3-D

Atala’s group has been experimenting with engineering other organs besides bladders. At Wake Forest, approximately 300 researchers are working on engineering more than 30 different body parts. They have had the most success so far with simple structures, such as ears, which don’t have a lot of blood vessels or nerve connections. These organs are currently being used to treat wounded veterans returning from the Iraq and Afghanistan wars.

Replacement kidneys, ears, and fingers are among the organs being engineered at Wake Forest University’s Institute for Regenerative Medicine.

In partnership with the U.S. military, Atala’s group is also working to make more complex body parts for soldiers whose pelvic regions were harmed by explosive devices. While the treatments are years away from the doctor’s office, the group has had some promising success in animal models. For example, scientists have successfully created functional rabbit penises that are recognized and used by the bunny recipients. The approach could one day help the scores of soldiers returning from Iraq and Afghanistan with genital injuries.

A major hurdle in building more-complex organs is the intricacy of the design. A bladder is essentially a balloon. But solid organs, such has hearts and kidneys, are much more complicated. One way that scientists are attempting to solve that problem is by using computers to design the delicate structures on-screen and then print the results.

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Until recently, most bioprinters were simply modified ink jet printers with cartridges filled with cells instead of ink. The printers that now do this work are specifically designed and built for the purpose. Bioprinters are being used to build new blood vessels as well as more-complex organs like kidneys. Researchers are even developing printers that can scan a wound and print an appropriately shaped skin “bandage.” The first commercial bioprinter was created by the San Diego-based company Organovo in 2009.

A biodegradable scaffold in the shape of a trachea can be seeded with cells and transplanted into a patient.

The idea behind bioprinting is really no different from other types of three-dimensional printing. Commercially available 3-D printers can make just about anything these days, from plastic toys and jewelry to chocolate candies to dental crowns and prosthetic limbs. All these technologies rely on 3-D graphics software that is much like the programs architects have used for years. The designs are fabricated by a printer that uses gel-like substances to build the structure in three dimensions. Bioprinting does the same thing, but instead of plastic, metal, or chocolate, the construction material is your own differentiated cells, produced from stem cells.

Atala and his group at Wake Forest have used organ printing to build miniature kidneys that have been shown to be functional–able to filter blood and produce urine. He printed one of the organs before a live audience during a TED Talk in 2011. These experimental prototypes aren’t ready to be used in people, but the technology is progressing rapidly.

The main difficulty with engineering more-complex solid organs like livers, hearts, and kidneys is ensuring that all the cells in the organ are linked to an adequate blood supply, which in normal tissues is accomplished by an intricate web of capillaries (see Chapter 27). The organs have to be properly hooked up to nerves, too, so that they can send and receive signals from the brain. “It’s a tough challenge, but I think it’s doable,” Atala told Scientific American in 2011.

Researchers in this field look forward to the day, in the not-too-distant future, when patients will be able to order just about any organ they need, designed to work perfectly in their own body. No longer will patients die while waiting for an organ donor.

“With the field of regenerative medicine,” says Atala, “the hope is to be able to have tissues and organs available for patients that wouldn’t otherwise have them.”

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