Medical Discovery News
By Drs. David Niesel and Norbert Herzog
 
3-D printers have proven capable of creating guns that actually fire bullets, pizza (although there’s no assurance of its taste), and now, livers. 3-D printing technology or stereolithography has been used to create miniature human livers, the first step toward producing full-sized livers and eliminating the long wait for a liver transplant.

3-D printing originated with the invention of the inkjet printer in 1976, which was then adapted to print with materials other than inks in 1984. The first machine to print in 3-D was created in 1992 to make objects by applying layer after layer of material governed by computer. By 2002, engineers and scientists developed methods to print biomaterials and make functional miniature kidneys. Since then, 3-D printers have been used to make cars, robotic aircraft, blood vessels, jewelry and even prosthetics.

The miniature livers produced thus far by a company called Organovo are only one-half of a millimeter thick and four millimeters long. To create them the printer lays down about 20 layers of liver cells called hepatocytes and stellate cells. Hepatocytes are the most prevalent type of cell in the liver and stellate cells are vital in liver regeneration and other functions. The printing also includes cells that line blood vessels in order to create a meshwork of small channels to provide oxygen and nutrients, thereby extending the life of these printed livers. The printer used by Organovo was able to place the cells in precise spatial patterns that resemble the natural liver.

These printed livers functioned like healthy, natural livers. They produced albumin, which is a protein that helps move many small molecules through the blood, including bilirubin, calcium, progesterone and medications. It also plays an important role in keeping the fluid in the blood from leaking out into the tissues. They also synthesized cholesterol and detoxified key enzymes called cytochrome P450s that metabolize drugs and toxins to protect the body.

The goal of this research is to eventually print full-sized livers that could be transplanted into those who need them. Currently, over 15,000 people are waiting for a liver, and last year, 1,550 died while waiting for a liver transplant. Liver transplants can be the only option for people whose livers are damaged by alcoholism, infections like hepatitis, clots that block blood flow, autoimmune liver diseases, cancer, birth defects and genetic disorders. Liver failure causes many health problems including malnutrition, blood clotting, bleeding from the gastrointestinal tract and jaundice. Because the human body needs a functioning liver, a person experiencing liver failure will die without a transplant.

One of the major challenges to printing full-sized human livers is developing a way to print larger branched networks of blood vessels, as these are absolutely essential to the survival of the printed organ. But medical uses for 3-D printing, such as using it to model facsimiles of patients’ organs in preparation for surgeries, show that this technology has the potential to save lives.

Medical Discovery News is a weekly radio and print broadcast highlighting medical and scientific breakthroughs hosted by professor emeritus Norbert Herzog and professor David Niesel, biomedical scientists at the University of Texas Medical Branch at Galveston. Learn more at www.medicaldiscoverynews.com.