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Scientists work to 3D bioprint a human heart in 5 years

The goal is to implant the heart into a pig before clinical trials could begin on human.
Scientists work to 3D bioprint a human heart in 5 years
Posted at 4:06 PM, Nov 29, 2023

A team of Stanford University engineers, cardiologists, and biology experts are at work to bioprint a fully functioning human heart to implant into a pig.

Inside one of the labs that focuses on medical innovation at Stanford University, there's a small room. It stays cold to protect a cylindrical bioreactor. Inside the cylinder, a light red liquid seems to sparkle when you look closely. Even closer, some of the sparkling segments seem to clump.

Those sparkly bits are stem cells. A little clump equals thousands of them.

Mark Skylar-Scott runs the lab where he and a team of technical minds are working to bioprint a fully functioning human heart to implant into a pig, in five years, funded by $26.3 million federal contract from the Advanced Research Projects Agency for Health.

"I sometimes refer to them as pieces of couscous floating around in the media. And they're being instructed by the media. We added chemicals to the media to tell the, to become heart cells," Mark Skylar-Scott explains. 

This bioreactor will turn out billions of heart cells.

"We're trying to show that biology is escaping the petri dish and becoming a kilogram of tissue that lives, that beats, that functions. That's that's our dream and that's what we're working towards," he said.

When there is a successful batch, the team prepares to bioprint. Bioprinting is 3D printing, where instead of ink or filament, cells are used to make living tissues. They're tackling small print batches: 10 to 40 minutes for a small cube filled with a vascular (aka blood vessel) structure. 

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For scale, we have about 60,000 blood vessels in our body. The printed products are actually channels a researcher flushes out. Eventually blood could flow through.

"We typically print at around 200 million cells per milliliter. So in one of those cubes, it's about 10 milliliters. So that's about two billion cells. But if we wanted to make a whole heart, we need about 10 to 30 billion cells. And so we will need, in the words of "Jaws", 'we're going to need a bigger boat,'" he said. 

That "bigger boat" means a bank of bigger bioreactors. Scientists are also studying how to do this with nine different types of heart cells. They'll need to make: muscle cells, cells that prevent clots, immune cells, cells that pace heart rate to name a few.

One challenge they'll face — small networks of capillaries.

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"We can print pretty dense vessel networks. But if you look very closely at the body, we have capillaries everywhere. There are capillaries for pretty much every single heart cell in the heart. So if you look at how densely packed they are, we simply can't print every tiny, tiny blood vessel. At some point, we will rely on biology taking over for us at the small scale, these blood vessels kind of learn how to grow and where oxygen is needed, they will follow and develop," he told Scripps News. "That's where we're throwing a lot of our sort of brainpower, effort and energy into trying to tackle. We think it will be solvable, but not easy. I can't say we've solved it yet, but we're working very hard on it."

Even at this small print scale just now, the work going on here is a potential solution for a very big real-world problem. Currently, about 100,000 Americans are waiting for an organ transplant.

"While we're focused on the cardiovascular system, ultimately, what we do is try and produce a lot of cells and keep them living by printing blood vessels. And every major organ needs a lot of blood vessels to stay alive," he said. 

The moonshot is on a five-year deadline, ending with a bioprint of a human heart, to implant into a pig for clinical trials before testing in humans. It's a big step, and it's still years away from a bespoke heart. Sklyar-Scott believes it will happen and biotechnology will get there in the next few decades.

"We want to have it in an animal show that it is functional. Prove to everyone that this is feasible. This is no longer a moonshot," he said. 

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