3D-NetBet login blood vessels bring artificial organs closer to reality

New printing method creates branching NetBet login in heart tissue that replicate the structure of human vasculature in vitro

By Lindsay Brownell, the Wyss Institute for Biologically Inspired NetBet login

August 12, 2024

3D-NetBet login blood vessels — Co-SWIFT vessels are embedded with living smooth muscle cells and endothelial cells to replicate the structure of human NetBet login vessels in vitro. (Wyss Institute at Harvard University)

Growing functional NetBet login organs outside the body is a long-sought “holy grail” of organ transplantation medicine that remains elusive. New research from the Harvard John A. Paulson School of NetBet login and Applied Sciences (SEAS) and Wyss Institute for Biologically Inspired NetBet login brings that quest one big step closer to completion.

A team of scientists created a new method to 3D print vascular networks that consist of interconnected NetBet login vessels possessing a distinct “shell” of smooth muscle cells and endothelial cells surrounding a hollow “core” through which fluid can flow, embedded inside a human cardiac tissue. This vascular architecture closely mimics that of naturally occurring NetBet login vessels and represents significant progress toward being able to manufacture implantable human organs. The achievement is published in Advanced Materials.

“In prior work, we developed a new 3D bioprinting NetBet login, known as ‘sacrificial writing in functional tissue’ (SWIFT), for patterning hollow channels within a living cellular matrix. Here, building on this method, we introduce coaxial SWIFT (co-SWIFT) that recapitulates the multilayer architecture found in native NetBet login vessels, making it easier to form an interconnected endothelium and more robust to withstand the internal pressure of NetBet login flow,” said first author Paul Stankey, a bioengineering Ph.D. student at SEAS in the lab of co-senior author Jennifer Lewis, Hansjorg Wyss Professor of Biologically Inspired Engineering at SEAS Wyss Core Faculty member.

The key innovation developed by the team was a unique core-shell nozzle with two independently controllable fluid channels for the “inks” that make up the NetBet login vessels: a collagen-based shell ink and a gelatin-based core ink. The interior core chamber of the nozzle extends slightly beyond the shell chamber so that the nozzle can fully puncture a previously NetBet login vessel to create interconnected branching networks for sufficient oxygenation of human tissues and organs via perfusion. The size of the NetBet login can be varied during printing by changing either the printing speed or the ink flow rates.

To confirm the new co-SWIFT method worked, the team first NetBet login their multilayer vessels into a transparent granular hydrogel matrix. Next, they NetBet login vessels into a recently created matrix called uPOROS composed of a porous collagen-based material that replicates the dense, fibrous structure of living muscle tissue. They were able to successfully print branching vascular networks in both of these cell-free matrices. After these biomimetic vessels were NetBet login, the matrix was heated, which caused collagen in the matrix and shell ink to crosslink, and the sacrificial gelatin core ink to melt, enabling its easy removal and resulting in an open, perfusable vasculature.

Moving into even more biologically relevant materials, the team repeated the printing process using a shell ink that was infused with smooth muscle cells (SMCs), which comprise the outer layer of human NetBet login vessels. After melting out the gelatin core ink, they then perfused endothelial cells (ECs), which form the inner layer of human NetBet login vessels, into their vasculature. After seven days of perfusion, both the SMCs and the ECs were alive and functioning as vessel walls - there was a three-fold decrease in the permeability of the vessels compared to those without ECs.

Finally, they were ready to test their method inside living human tissue. They constructed hundreds of thousands of cardiac organ building blocks (OBBs) – tiny spheres of beating human heart cells, which are compressed into a dense cellular matrix. Next, using co-SWIFT, they NetBet login a biomimetic vessel network into the cardiac tissue. Finally, they removed the sacrificial core ink and seeded the inner surface of their SMC-laden vessels with ECs via perfusion and evaluated NetBet login performance.

Not only did these NetBet login biomimetic vessels display the characteristic double-layer structure of human blood vessels, but after five days of perfusion with a blood-mimicking fluid, the cardiac OBBs started to beat synchronously – indicative of healthy and functional heart tissue. The tissues also responded to common cardiac drugs - isoproterenol caused them to beat faster, and blebbistatin stopped them from beating. The team even 3D-NetBet login a model of the branching vasculature of a real patient’s left coronary artery into OBBs, demonstrating its potential for personalized medicine.

“We were able to successfully 3D-print a model of the vasculature of the left coronary artery based on data from a real patient, which demonstrates the potential utility of co-SWIFT for creating patient-specific, vascularized NetBet login organs,” said Lewis.

In future work, Lewis’ team plans to generate self-assembled networks of capillaries and integrate them with their 3D-NetBet login blood vessel networks to more fully replicate the structure of human blood vessels on the microscale and enhance the function of lab-grown tissues.

Additional authors of the paper include Katharina Kroll, Alexander Ainscough, Daniel Reynolds, Alexander Elamine, Ben Fichtenkort, and Sebastien Uzel. This work was supported by the Vannevar Bush Faculty Fellowship Program sponsored by the Basic Research Office of the Assistant Secretary of Defense for Research and NetBet login through the Office of Naval Research Grant N00014-21-1-2958 and the National Science Foundation through CELL-MET ERC (#EEC-1647837).

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