How a Tiny, “Beating” Human Heart Was Created in a Lab

The device, filled with human heart cells, could dramatically reduce the time it takes to test new drugs and end testing on animals

Heart on a chip
Mini-organs grow around the tiny scaffolds (lower left). The magnified image (right) shows the hair-thin channels that serve as blood vessels. Tyler Irving/Boyang Zhang/Kevin Soobrian

Not many inventions are as expensive to create or as likely to fail as new medications. 

It’s estimated that, on average, developing and testing a new pharmaceutical drug now takes 10 years and costs almost $1.4 billion. About 85 percent never make it past early clinical trials, and of those that do, only half are actually approved by the FDA to go on the market. That’s one of the reasons drugs cost so much.

Now, the good news. Scientists focusing on how to improve the odds of success and speed up the process while keeping drugs safe have developed a promising innovation: “organs on a chip.” They’re pretty much what they sound like—tiny, functioning versions of human organs grown on a device roughly the size of a computer memory stick. 

The latest leap forward comes from a team of biomedical engineers at the University of Toronto. Earlier this week, in an article in the journal Nature Materials, these scientists explained how they have been able to get both heart and liver tissues to grow on a small, three-dimensional scaffold, honeycombed with hair-thin artificial blood vessels, and then watch the organs function as they would inside the human body.

They call their device an AngioChip, and according to the head of the team, Milica Radisic, its potential goes beyond revolutionizing the drug testing process. She envisions a day when it could be implanted in a human body to repair diseased or damaged organs.

“It really is multifunctional, and solves many problems in the tissue engineering space,” said Radisic, a professor at the university’s Institute of Biomaterials & Biomedical Engineering, in a press release. “It’s truly next-generation.” 

Building mini-organs

Researchers are already able to grow organ tissue in labs, but it’s generally on a flat plate, and results in a two-dimensional model different from what actually happens inside us. That limits how much researchers can learn about the effectiveness and risk of using a new drug to treat a particular organ.

But technology like the AngioChip provides a more realistic, if tiny, version of human organs and that, says Radisic, will allow researchers to identify early on those drugs that merit moving on to clinical trials. It also could greatly reduce the need to test them on animals.

Building the device was no small challenge. Graduate student Boyang Zhang first had to use a technique called 3D stamping to create extremely thin layers of a clear, flexible polymer. Each layer contained a pattern of channels no wider than a human hair. These would serve as the organ’s blood vessels. 

He then manually stacked the layers and used UV light to cause a chemical reaction that melded them together. That created the scaffolding around which the organ would grow. To see if their invention would actually work, the researchers implanted it in a rat. They were thrilled to see blood passing through the device’s narrow channels without clotting.

They then bathed an AngioChip in a liquid filled with living human heart cells. Soon, those cells started growing inside and outside the artificial blood vessels just as they would in a human body. As the cells continued to grow over the next month, the flexible device began to act like an actual organ, eventually contracting and expanding in a steady rhythm, just like a heartbeat.

"What makes the AngioChip unique is that we built a vascular system in the tissue," Zhang explains. "This network of vessels will, in the future, help us to connect multiple organs together just like how our organs are linked together in our blood system." 

Replacing transplants?

The engineers created a liver on a chip the same way. In time, it too began behaving like its human counterpart, producing urea, the main compound in urine, and also metabolizing drugs. Eventually, the scientists will be able to connect chips of different organs to see not only how a drug would affect each organ, but also its impact on both of them at the same time.

Or, as Radisic has suggested, a tumor and heart cells could be linked together to see which drugs might destroy the tumor without harming the heart. 

"The smallest vessels in this tissue were only as wide as a human hair, but blood was still able to flow easily through them," said Radisic."This means that we will be able to build human tumors in animals using this platform to help discover new, more effective anti-cancer drugs."   

Clearly, lab-grown organs have the potential to bring much more precision and speed to the drug testing process. But once the AngioChip can be implanted in humans, Radisic notes, it could replace the need for transplanting organs from another person. Instead, organs could be grown with cells taken from the host, which could significantly lower the risk of rejection.

On average, 21 people die every day because suitable organs aren’t available for transplants. 

The next step for the University of Toronto team is to work with a manufacturer to develop a process for building multiple AngioChips at the same time. Right now, they're hand built, one at a time. 

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