3D-Printed Blood Vessels Edge Us Closer to Artificial Organs
Researchers at Harvard's Wyss Institute for Biologically Inspired Engineering and the John A. Paulson School of Engineering and Applied Science (SEAS) have made a leap in the quest to create artificial organs. Their latest innovation involves 3D printing complex vascular networks that mimic human blood vessels, bringing the reality of implantable human organs closer. The achievement is published in Advanced Materials.
co-SWIFT vessels are embedded with living smooth muscle cells and endothelial cells to replicate the structure of human blood vessels in vitro. Credit: Wyss Institute at Harvard University
3D Bioprinting: Introducing co-SWIFT
Led by Jennifer Lewis, Sc.D., and graduate student Paul Stankey, the team has built on their previous 3D bioprinting method, "sacrificial writing in functional tissue" (SWIFT). Their new technique, called "coaxial SWIFT" (co-SWIFT), enables the creation of blood vessels with multiple layers, similar to those in the human body. This development is key for forming the intricate, interconnected networks needed to support living tissues.
co-SWIFT prints 3D vessels that consist of an outer “shell” and an inner “core” that can be easily connected to each other to create a branching network of vasculature that can support living human tissues. Credit: Wyss Institute at Harvard University
At the heart of this breakthrough is a unique core-shell nozzle with two controllable channels for the printing "inks"—a collagen-based shell and a gelatin-based core. This design allows the nozzle to puncture previously printed vessels, forming branching networks essential for delivering oxygen to tissues. By tweaking the printing speed and ink flow rates, the researchers can adjust the vessel sizes with precision.
Proving the Method, Biological Relevance
To validate their approach, the team printed multilayer vessels into both a transparent hydrogel matrix and a porous collagen-based material called uPOROS, which simulates muscle tissue. When heated, the collagen in the matrix and shell ink crosslinked, while the gelatin core ink melted away, leaving a network of open, perfusable blood vessels.
Taking it a step further, the researchers infused the shell ink with smooth muscle cells (SMCs) and perfused endothelial cells (ECs) into the vascular structures. This resulted in functional vessel walls that significantly reduced permeability, indicating robust vessel integrity.
From Innovation to Life
Furthermore, the team constructed tiny clusters of beating human heart cells, known as cardiac organ building blocks (OBBs), and printed a biomimetic vascular network within this dense cell matrix. After removing the gelatin core and seeding ECs into the SMC-laden vessels, they achieved functional vascular structures. Remarkably, after just five days of perfusion with a blood-mimicking fluid, the cardiac OBBs began beating synchronously, signaling healthy, functional heart tissue. These tissues also reacted appropriately to cardiac drugs, confirming their viability.
The original SWIFT method (left) printed hollow channels through living OBBs (green), but had no structure to contain fluid as it flowed through. Co-SWIFT (right) creates a cell-laden vessel (red) surrounding the channel, which isolates blood flow from the tissue and improves their viability. Credit: Wyss Institute at Harvard University
To demonstrate the technology's potential, the team 3D-printed a model of a patient's left coronary artery vasculature into OBBs, showcasing how this method could be used to create patient-specific, vascularized organs.
Future Plans
Next, the team plans to integrate self-assembled networks of capillaries with their 3D-printed vessels to more accurately replicate the fine structure of human vasculature and enhance the function of lab-grown tissues. Their ultimate goal is to implant lab-grown tissues into patients, a breakthrough that could transform organ transplantation.
Donald Ingber, M.D., Ph.D., the Wyss Founding Director, commented:
“To say that engineering functional living human tissues in the lab is difficult is an understatement. I’m proud of the determination and creativity this team showed in proving that they could indeed build better blood vessels within living, beating human cardiac tissues. I look forward to their continued success on their quest to one day implant lab-grown tissue into patients.”
Topics: Bioprinting
