3D Printing the Intricate Structure’s in Human Organs

A recent innovation in 3D printing allowed bioengineers to recreate the intricate human vascular systems, marking a breakthrough in bioprinting organs. This work, featured on the cover of the May 3 edition of Science, involved a hydrogen model of the lung’s oxygen exchanging sacs known as alveoli. This work was led by Jordan Miller, a bioengineer at Rice University, and Kelly Stevens of the University of Washington, and included work collaborators at Rice, UW, Duke University, Rowan University, and a Massachusetts design firm known as Nervous System.

“One of the biggest road blocks to generating functional tissue replacements has been our inability to print the complex vasculature that can supply nutrients to densely populated tissues,” explained Miller. “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 bioprinting technology that addresses the challenge of multivascularization in a direct and comprehensive way.”

With over 100,000 US citizens on waiting lists for organ transplants, emphasis has been put on 3D printing as a possible remedy. Bioprinting would not only address this shortage in donor organs but would avoid organ rejection as well. Many recipients of donor organs must use immune system suppressing drugs to avoid rejection for the remainder of their lives; however, bioprinting allows these organs to be generated using the patient’s own cells.

“We envision bioprinting becoming a major component of medicine within the next two decades,” Miller said.

READ MORE: Using Ultrasound to Align Cells in 3D Printed Tissue

In their study, the researchers printed layers from a liquid pre-hydrogel that solidifies under blue light. Light was shined from below to display 2D slices of the structure with pixel sizes ranging from 10-50 microns. The 3D gel was then raised to expose the liquid for the next image, gradually growing the gel in size. Miller noted that adding food dyes to absorb blue light was a key component that allowed them to solidify one fine layer at a time, yielding a biocompatible gel with complex structure in a short amount of time.

The team tested this bioprinted lung structure and found the tissue’s durability withstood blood flow and simulations of human breathing. In addition, red blood cells were found to absorb oxygen as it flowed through the blood vessel network surrounding the air sac in a manner similar to gas exchange occurring in the human lung.

Miller explained that the source data involved in the Science-published study are freely available, as are the 3D printing design files for the hydrogels. He noted that his lab is currently using the new design and 3D printing techniques to create structures of even higher complexity than those detailed in the study.

“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,” he said. “We are only at the beginning of our exploration of the architectures found in the human body. We still have so much more to learn.”

Source: Rice UniversityScience