At the time of publication, surgeons hadn't implanted an organ printed from scratch into a human. That doesn't mean there haven't been successes. Replacing parts of the skeleton is one area being revolutionized by 3-D printing. Some dentists now take an intra-oral scan of a patient's teeth and send the scan to a lab that fashions a porcelain bridge using a 3-D printer. Prosthetic manufacturers also have changed their approach to designing artificial limbs. Now, many are able to print fairings -- prosthetic limb covers -- that mold perfectly to a person's anatomy, giving the wearer a more comfortable fit. These are just preludes to what the future may hold: printing entire bones for placement in the body. Doctors in the Netherlands have already created a lower mandible on a 3-D printer and implanted the jaw -- made from bioceramic-coated titanium -- in a patient suffering from a chronic bone infection.
Scientists have also successfully printed cartilaginous structures, such as ears and tracheas. To make the former, bioengineers take a 3-D scan of a patient's ear, design a mold using CAD software and then print it out. Then they inject the mold with cartilage cells and collagen. After spending some time in an incubator, the ear comes out, ready for attachment to the patient. A trachea can be made in a similar fashion. In 2012, doctors at the University of Michigan printed a sleeve, made from a 3-D model generated from a CT scan, to wrap and support a baby's trachea, which had been rendered weak and floppy by a rare defect.
The holy grail, of course, is a bioprinted organ, and skin -- the body's largest organ -- may be the first item on the list. Researchers at the Wake Forest Institute for Regenerative Medicine already have developed a complete system to print skin grafts. The system includes a scanner to map a patient's wound and a purpose-built inkjet printer that lays down the cells, proteins and enzymes necessary to form human skin. The goal is to build portable printers for use in field hospitals, where doctors can output skin directly onto patients.
Until these marvels come online, 3-D organs will play an important role in education and drug development. They might even factor into the development of food and clothing products (lab-grown meat and leather). Some medical schools have invested in 3-D printing technology to create surgical models of organs from CT or MRI images. This allows students to practice on hearts, livers and other structures that look and feel just like the real thing. Having access to such lifelike tissues also benefits pharmaceutical companies, which can test candidate drugs to see their effects. Organovo houses several printers capable of printing out three-dimensional models of liver, kidney and cancer tissues. These aren't full organs meant to live indefinitely. Instead, they're "organs on a chip" -- small, biologically active tissue samples designed to respond as native tissues would.
Perhaps one day, bioprinting will make anyone a Victor Frankenstein, capable of printing out organs, bones and muscles and assembling it all into a reasonable facsimile of a human. Then again, there's the issue of a nervous system. Even the best scanners, printers, inks and gels will fall short when it comes to recreating a thinking, dreaming brain. And without that, our efforts would leave us with a collection of anatomically correct, three-dimensionally accurate organs, but nothing to control them.