Digital model of a blood vessel network Credit: The University of California San Diego
Nanoengineers have 3D printed a lifelike, functional blood vessel network that could pave the way toward artificial organs and regenerative therapies.
Researchers at the University of California San Diego have created artificial tissue and organs with functioning vasculature—a networks of blood vessels that can transport blood, nutrients, waste and other biological materials—and do so safely when implanted inside the body.
Previously, researchers have used different 3D printing technologies to create artificial blood vessels but existing technologies are slow, costly and mainly produce simple structures. These blood vessels are not capable of integrating with the body’s own vascular system.
“Almost all tissues and organs need blood vessels to survive and work properly. This is a big bottleneck in making organ transplants, which are in high demand but in short supply,” Shaochen Chen, who leads the Nanobiomaterials, Bioprinting, and Tissue Engineering Lab at UC San Diego, said in a statement. “3D bioprinting organs can help bridge this gap, and our lab has taken a big step toward that goal.”
The research team has 3D printed a vasculature network that can safely integrate with the body’s own network to circulate blood. These blood vessels branch out into many series of smaller vessels, similar to the blood vessel structures found in the body.
They developed a bioprinting technology, using their own homemade 3D printers, to rapidly produce intricate 3D microstructures that mimic the sophisticated designs and functions of biological tissues.
The researchers first created a 3D model of the biological structure on a computer, which then transfers 2D snapshots of the model to millions of microscopic-sized mirrors that are each digitally controlled to project patterns of UV light in the form of these snapshots. The UV patterns are shined onto a solution containing live cells and light-sensitive polymers that solidify when exposed to UV light.
The structure is then rapidly printed one layer at a time, in a continuous fashion, creating a 3D solid polymer scaffold encapsulating live cells that will grow and become biological tissue.
“We can directly print detailed microvasculature structures in extremely high resolution,” Wei Zhu, a postdoctoral scholar in Chen’s lab and a lead researcher on the project. “Other 3D printing technologies produce the equivalent of ‘pixelated’ structures in comparison and usually require sacrificial materials and additional steps to create the vessels.”
This process is extremely quick and only takes a few seconds—an improvement over competing bioprinting methods that normally take hours just to print simple structures. The researchers also deemed the process to be inexpensive and biocompatible.
The research team used medical imaging to create a digital pattern of a blood vessel network found in the body and by using 3D technology, they printed a structure containing endothelial cells—cells that form the inner lining of blood vessels.
The researchers cultured several structures in vitro for one day and then grafted the resulting tissues into skin wounds of mice. Then after two weeks, the researchers examined the implants and found that they had successfully grown into and merged with the host blood vessel network, which allowed blood to circulate normally.
According to Chen, the implanted blood vessels are not yet capable of other functions like transporting nutrients and waste.
Chen said the next step will be to work on building patient-specific tissues using human induced pluripotent stem cells, which would prevent transplants from being attacked by a patient’s immune system.
