Scientists at Harvard’s Wyss Institute have achieved a breakthrough in 3D printing blood vessels, advancing the goal of creating functional, implantable organs grown in labs. Collaborating with the John A. Paulson School of Engineering and Applied Science (SEAS), the team has introduced a technique called coaxial SWIFT (co-SWIFT), which can replicate the complex structure of human vasculature.

Co-SWIFT allows for the production of vascular networks embedded within human cardiac tissue, featuring a hollow core surrounded by a shell of smooth muscle and endothelial cells—closely mimicking the natural structure of blood vessels. This innovative method improves upon the 2019-developed SWIFT technique, which was groundbreaking for printing hollow channels within living tissue. However, SWIFT lacked the ability to replicate the multilayered, pressure-resistant nature of real blood vessels.

With co-SWIFT, researchers have created 3D-printed vessels that not only have a hollow core for fluid flow but also a layered shell resembling real blood vessels, making them more robust and capable of handling blood pressure. These advancements represent a significant improvement over the original SWIFT method, bringing scientists closer to replicating human tissue functions.

Graduate student and study lead author Paul Stankey explained that their breakthrough lies in a core-shell nozzle design, which uses two fluid channels: one for a collagen-based shell and the other for a gelatin-based core. This design enables the creation of branching, strong vascular structures that can withstand internal blood pressure and support living tissues.

To test these 3D-printed vessels, the team first used materials without cells, such as collagen mimicking muscle tissue. After printing, the gelatin core was melted away, leaving open channels for blood flow. Smooth muscle cells were added to the outer shell, and endothelial cells to the inner layer, ensuring the vessels performed similarly to real blood vessels. After seven days of testing, the vessel walls remained intact, and the endothelial cells reduced permeability, confirming the vessels’ functionality.

The team further applied this technique to living human tissue, creating small clusters of human heart cells, known as cardiac organ building blocks (OBBs). These were compressed into a dense matrix to mimic human tissue. Using co-SWIFT, they printed vascular networks within the living tissue, creating a more realistic model. After removing the gelatin core and perfusing the vessels with endothelial cells, the cardiac tissue began beating synchronously after five days—indicating healthy, functional tissue.

Beyond supporting living tissue, the researchers successfully 3D printed a model of the left coronary artery based on patient data, showcasing the potential of co-SWIFT for creating patient-specific, vascularized organs. Jennifer Lewis, co-senior author and Wyss Professor of Biologically Inspired Engineering at SEAS, emphasized the next steps include creating capillary networks, vital for replicating tissue function at a microscale.

While the road to fully lab-grown, transplantable organs is still long, this achievement marks tremendous progress. Donald Ingber, Founding Director of the Wyss Institute and co-senior author of the study, praised the team’s creativity and determination, expressing optimism for future advancements and their potential to implant lab-grown tissues in patients.

By Impact Lab