3D Printed Organs are about to Become a Reality

The image bears no relation to the study

The image bears no relation to the study

A normal kidney transplant costs an average of US $ 330,000, whilst a 3D bio-printed liver would costs around US $10,000.

3D bio-printing is the process of artificially constructing an organ by using bio-ink composed of tissues or human cells. It is a method of layering bio-ink to create 3D tissues which can be used in organ transplants.

While most of the printed organs are in their early stages of development, there are many in there has been some considerable progress, specifically with kidneys, livers, hearts, corneas and bones.

3D printing has come a long way. It provides many benefits, including increased cost efficiency. For instance, according to the National Foundation for Transplants, a normal kidney transplant costs an average of US $330,000. On the other hand, a 3D bio-printed liver costs around US $10,000. The lowered cost can help many people suffering from organ failure in a cost-effective manner.

One of the major challenges in 3D bio-printing is the ability to create a network of blood vessels required to keep 3D printed organs alive. However, Bioengineers have recently found a way to overcome this major hurdle, and scientists can now create exquisitely entangled vascular networks that mimic the body's natural passageways.

The bioengineers; Jordan Miller of Rice University, Kelly Stevens of the University of Washington (UW), 15 collaborators from Rice University, University of Washington, Rowan University, Duke University, and a design firm in Somerville, Massachusetts named ‘Nervous System’ led the research.

Miller, assistant professor of bioengineering at Rice's Brown School of Engineering said, "One of the biggest roadblocks to generating functional tissue replacements has been our inability to print the complex vasculature that can supply nutrients to densely populated tissues." "Further, our organs actually contain independent vascular networks like the airways and blood vessels of the lung or the bile ducts and blood vessels in the liver. These interpenetrating networks are physically and biochemically entangled, and the architecture itself is intimately related to tissue function. Ours is the first bio-printing technology that addresses the challenge of multi-vascularization in a direct and comprehensive way."

Stevens, assistant professor of bioengineering in the UW College of Engineering, assistant professor of pathology in the UW School of Medicine, and an investigator at the UW Medicine Institute for Stem Cell and Regenerative Medicine said ‘’multi-vascularization is important because form and function often go hand in hand.’’ "Tissue engineering has struggled with this for a generation," she added. "With this work, we can now better ask, 'If we can print tissues that look and now even breathe more like the healthy tissues in our bodies, will they also then functionally behave more like those tissues?' This is an important question, because how well a bio-printed tissue functions will affect how successful it will be as a therapy."

The research included visual proof - a hydrogel model of a lung-mimicking air sac in which airways deliver oxygen to surrounding blood vessels.

Stevens said, "The liver is especially interesting because it performs a mind-boggling 500 functions, likely second only to the brain." She further added, "The liver's complexity means there is currently no machine or therapy that can replace all its functions when it fails. Bio-printed human organs might someday supply that therapy."

To address this issue, an experiment was conducted dubbed as the "stereolithography apparatus for tissue engineering," or SLATE. To design it, Miller and Stevens collaborated with study co-authors Jessica Rosenkrantz and Jesse Louis-Rosenberg, co-founders of Nervous System.

Rosenkrantz said, "When we founded Nervous System it was with the goal of adapting algorithms from nature into new ways to design products.’’ He further added, "We never imagined we'd have the opportunity to bring that back and design living tissues."

In this experiment layers of a liquid pre-hydrogel solution are printed. Once it’s exposed to a digital light processing projector, it becomes solid. As the projector light shines from below, it displays sequential 2D slices of the structure at high resolution, with pixel sizes ranging from 10-50 microns. As each layer solidifies, an overhead arm raises the growing 3D gel just enough to expose liquid to the next image from the projector. The key insight is the addition of food dyes that absorb blue light.

Tests showed that the lung-mimicking structure’s tissues were sturdy enough to avoid bursting during blood flow and pulsatile breathing. They further found that red blood cells could take up oxygen as they flowed through a network of blood vessels surrounding the "breathing" air sac and this movement of oxygen was similar to the gas exchange that occurs in the lung's alveolar air sacs. For further testing, the team also implanted the primary liver cells into mice with a chronic liver injury and the test showed that the liver cells survived the implantation.

Miller said, ‘’the new bio-printing system can also produce intravascular features, like bicuspid valves that allow fluid to flow in only one direction. In humans, intravascular valves are found in the heart, leg veins and complementary networks like the lymphatic system that have no pump to drive flow.” He further added, "With the addition of multivascular and intravascular structure, we're introducing an extensive set of design freedoms for engineering living tissue," and "We now have the freedom to build many of the intricate structures found in the body." He also said, "Making the hydrogel design files available will allow others to explore our efforts here, even if they utilize some future 3D printing technology that doesn't exist today."

In the U.S., more than 100,000 people are on the transplant waiting list and those who do eventually receive donor organs still face a lifetime of immune-suppressing drugs to prevent organ rejection. Bio-printing can help in a ready supply of functional organs which could one day be used to treat millions of people worldwide. Miller said that his lab is already using the new design and bio-printing techniques to explore even more complex structures. "We are only at the beginning of our exploration of the architectures found in the human body," he said. "We still have so much more to learn."

Story Source:  Materials provided by Rice University. (Content may be edited for style)