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For the study, published in the journal Science, the researchers printed in 3D a proof of principle – a hydrogel model of a lung-breathing air sac, in which the airways provide oxygen to the surrounding blood vessels.
"One of the most important barriers to the generation of functional tissue replacements has been our inability to print the complex vascular system that can provide nutrients to densely populated tissues," said Jordan Miller, badistant professor at Rice University. in the USA.
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"In addition, our organs actually contain independent vascular networks, such as the airways and blood vessels of the lung or bile ducts and the blood vessels of the liver," said Miller.
"These interpenetrating networks are physically and biochemically entangled, and the architecture itself is intimately linked to tissue function.Our technology is the first bioimpression technology to address the challenge of multivascularization in a direct and complete way" , did he declare.
Kelly Stevens, an badistant professor at the University of Washington (UW) in the United States, said that multivascularization is important because form and function often go hand in hand.
The goal of bioimprinting healthy and functional organs is dictated by the need for organ transplants.
Thousands of people are on the waiting lists for a transplant around the world, and those who ultimately receive donor organs still have to deal with a lifetime of immunosuppressive drugs to prevent organ rejection.
Bio-printing has attracted considerable interest over the past decade as it could theoretically solve both problems by allowing doctors to print replacement organs from the patient's cells.
A reserve of functional organs could one day be used to treat millions of patients worldwide.
"We envision that bioprinting will become a major component of medicine in the next two decades," Miller said.
"The liver is particularly interesting because it performs 500 amazing functions, probably right after the brain," Stevens said.
"The complexity of the liver means that there is currently no machine or therapy that can replace all of its functions in the event of a failure." The human organs with bioprint may someday provide this therapy, "he said. -he declares.
To meet this challenge, the team has created a new open-source bio-print technology, called the "stereolithography apparatus for tissue engineering" or SLATE.
The system uses additive manufacturing to make soft hydrogels one layer at a time.
The layers are printed from a liquid pre-hydrogel solution that becomes solid when exposed to blue light. A digital light treatment projector illuminates the light from below, displaying sequential 2D slices of the high-resolution structure, with pixel sizes ranging from 10 to 50 microns.
With each layer solidified in turn, a hanging arm lifts the growing 3D gel just enough to expose the liquid to the next image of the projector.
Tests of the structure mimicking the lungs showed that the tissues were robust enough to prevent bursting during blood circulation and pulsatile "breathing", rhythmic air entry and exit simulating pressure and the frequencies of human breathing.
Tests have shown that red blood cells can absorb oxygen when they circulate in a network of blood vessels surrounding the "breathing" air sac.
This movement of oxygen is similar to the gaseous exchange that occurs in the air sacs alveolar lung.
In therapeutic implant tests for liver diseases, the team printed 3D tissues, loaded them with primary liver cells and implanted them into mice.
The tissues had separate compartments for blood vessels and liver cells and were implanted in mice with chronic liver injury. Tests showed that liver cells survived implantation.
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