Though it’s much smaller than a human heart—at only 2.5 centimeters, it’s about the size of a rabbit’s—the proof-of-concept still contains a fully vascularized structure, complete with its own cells, ventricles and atria.

The cells are capable of contracting, but they still need to be taught to work together in order to pump blood effectively, before being tested as a transplant material in animal models, according to research lead Tal Dvir, a professor at Tel Aviv University’s School of Molecular Cell Biology and Biotechnology and Sagol Center for Regenerative Biotechnology.

"People have managed to 3D-print the structure of a heart in the past, but not with cells or with blood vessels," Dvir said in a statement. "Our results demonstrate the potential of our approach for engineering personalized tissue and organ replacement in the future."

Building a new heart started with a biopsy of a patient’s fatty tissue, which was then separated into cellular and acellular material. The cells were reprogrammed into pluripotent stem cells, while the extracellular matrix of collagen, sugars and proteins were processed into a personalized hydrogel.

That hydrogel forms the basis of the 3D bioink, which is then mixed with stem cells that have been differentiated into cardiac and endothelial cells. By alternating between the two different inks, the researchers were able to construct patches of heart tissue with blood vessels that are compatible with the patient’s immune system.

"The biocompatibility of engineered materials is crucial to eliminating the risk of implant rejection, which jeopardizes the success of such treatments," Dvir said.

To make sure the heart’s shape matched up with the anatomy of the patient, CT scans were used to gather a basic blueprint of the organ, including the orientation of the major blood vessels in the left ventricle. The vessels’ geometry was then drafted up using computer-aided design software.

But CT scans can’t provide images of the smaller blood vessels crisscrossing heart tissue—there, in order to make sure the entire patch receives enough oxygen, mathematical models were used to create a more-complete vasculature, calculated based on the laws of oxygen consumption and equations for optimal distribution.

"Here, we can report a simple approach to 3D-printed thick, vascularized and perfusable cardiac tissues that completely match the immunological, cellular, biochemical and anatomical properties of the patient," he added. The full study was published in Advanced Science.

by Conor Hale

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