What do researchers do after they 3D-print a heart with human tissue and vessels, in a development described as a “major medical breakthrough” that advances possibilities for transplants? Do they pop open the champagne? Go out for a festive dinner?

Apparently not. They go right back to work.

“I don’t think there was any day that was more significant than others in the whole process,” said Tal Dvir, 45, a researcher at Tel Aviv University whose team in April unveiled a 3D-printed heart (albeit the size of a rabbit’s) with human cells, blood vessels, ventricles and chambers, in a groundbreaking move.

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“I am one of those people who, when we get a result, I already think about the next thing,” Dvir said in an interview at his Tel Aviv University lab earlier this month. “I don’t get excited over what has been till now, but more about the thought of what the next stage is.”

There was no real “eureka” moment during the process of developing the printed heart, he acknowledged. It was a one-step-at-a-time process, trying and testing and trying again. Until they were successful.

“We are a lab that develops technologies. We make things and many times it doesn’t work, and so we fix it, and do it again,” Dvir related. “Each time we improve the result a little, and in the end we get to the final result.”

Their research involved taking a biopsy of fatty tissue from patients that was used in the development of the “ink” for the 3D print.

First they created patient-specific cardiac patches, then an entire heart, based on a detailed software model of the organ.

The process was somewhat like child-rearing, explained Assaf Shapira, who together with Dvir and doctoral student Nadav Moor worked on the project. You don’t notice how big your children have grown because you see them every day, and you only realize it when someone from the outside notices.

Asked whether he and Moor, at least, had gone out to celebrate, perhaps with a bottle of bubbly, Shapira quipped: “We have no budget for champagne, maybe fizzy water.”

Dvir’s team works out of a labyrinth of simple rooms at the Tel Aviv University campus. Shapira and a colleague were huddled over a computer when this reporter walked in. Behind them stood the 3D printer they used to print the heart. Alongside the machine, encased in tiny, square open-lid boxes, stood three tiny hearts immersed in a pink liquid. The hearts on display were those that were printed for the demonstration in April, said Shapira.

Since then, the researchers have furthered their work, fine-tuning and improving details, he said.

The 15 researchers in Dvir’s lab work on engineering various kinds of tissue, including heart, marrow, spine, brain, eyes and intestine. Together with the 3D heart, they are working on a total of 20 projects, including the regeneration of spinal cord tissue and cells to fight Parkinson’s disease; non-3D-printed heart patches; and projects that combine electronics with tissue.

To the left of the 3D printer stands another, newer one, which will help the researchers advance their work. They have also ordered a machine that will incubate and grow the hearts, so they can take the research forward.

Many challenges remain before fully working 3D-printed hearts will be available for transplant into patients, the scientists have emphasized.

“What we did was print a very basic heart. A heart with big blood vessels made up of cells and materials of humans and according to a model of a human heart,” Dvir said.

They must now teach the printed hearts to act like real ones. The heart cells are currently able to contract, but do not yet have the ability to pump.

“The cells contract, but not in a synchronized way, so the heart doesn’t pump,” said Dvir. “The next stage is to teach the heart how to get all of its cells to work in synchrony.”

With the heart in the incubator, the researchers will also finesse other details, ensuring for example that the smaller blood vessels necessary for the heart to function will also be generated.

“We have a lot of work to do, to make the heart mature, create more blood vessels and help the cells synchronize in the right way. There is still a lot, lot of work. This is just the first stage,” Dvir said.

The printing of the heart is a turning point for the technology, he allowed. “But it will take time before there’s a breakthrough in which we can transplant this heart.”

He will reserve his excitement, he said, for “when this heart will start pumping and will be put into an animal and survive there.”

The researchers are also well aware that, as so often happens in science, they could easily be overtaken by others on the way to the goalpost of creating the first transplantable 3D-printed heart.

“We have written patents on the technology,” Dvir said. But someone could use their approach to make their own 3D-printed hearts, with their own patents, cells and materials.

“And that is okay, because this is the way science moves forward,” he said. “We built our approach on what others have done before us. This is the game. We hope we will be the first; we are not resting on our laurels. We are working constantly, thinking ahead. But many others are also working on this.”