Organ bioprinting gets a breath of fresh air

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A visually stunning proof-of- principle -- a scale-model of a lung-mimicking air sac with airways and blood vessels that never touch yet still provide oxygen to red blood cells. PIX/Jordan Miller/Rice University

BIOENGINEERS have cleared a major hurdle on the path to 3D printing replacement organs with a breakthrough technique for bio-printing tissues.

The new innovation allows scientists to create exquisitely entangled vascular networks that mimic the body’s natural passageways for blood, air, lymph and other vital fluids.

The research is featured on the cover of this week’s issue of Science. It includes a visually stunning proof-of-principle — a hydrogel model of a lung-mimicking air sac in which airways deliver oxygen to surrounding blood vessels. Also reported are experiments to implant bioprinted constructs containing liver cells into mice.

The work was led by bioengineers Jordan Miller of Rice University and Kelly Stevens of the University of Washington (UW) and included 15 collaborators from Rice, UW, Duke University, Rowan University and Nervous System, a design firm in Somerville, Massachusetts.

“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,” said Miller, assistant professor of bioengineering at Rice’s Brown School of Engineering.

“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.”

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 multivascularisation is important because form and function often go hand in hand.

“Tissue engineering has struggled with this for a generation,” Stevens said.

“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 bioprinted tissue functions will affect how successful it will be as a therapy.” The goal of bioprinting healthy, functional organs is driven by the need for organ transplants. More than 100,000 people are on transplant waiting lists in the United States alone, and those who do eventually receive donor organs still face a lifetime of immune-suppressing drugs to prevent organ rejection.

Bioprinting has attracted intense interest over the past decade because it could theoretically address both problems by allowing doctors to print replacement organs from a patient’s own cells. A ready supply of functional organs could one day be deployed to treat millions of patients worldwide.