Toronto Star

U of T professor grows tiny hearts for research

Thumbnail-sized patch of tissue expands and contracts similarly to a beating heart


Tiny bits of human skin are being transforme­d into miniature, beating hearts in a scientific medical breakthrou­gh a University of Toronto researcher believes will not only save lives but alter the course of drug testing forever.

The rod-shaped, elastic-like, thumbnail-sized patch of tissue is only about six millimetre­s long but expands and contracts just like a beating heart. It’s a feat that its creator, U of T chemical engineer- ing professor Milica Radisic, originated from human skin biopsies, such as newborn foreskin tissue.

“When babies are circumcise­d, you can take cells from (the foreskin) instead of throwing it out,” she said.

These skin cells are then re-programmed into stem cells using a technique made famous by Nobel Prize-winning researcher Shinya Yamanaka. The Japanese scientist discovered skin cells from mice could be re-programmed into immature stem cells. The small organisms are then placed into a liquid where proteins encourage them to turn into cardiac cells.

While growing immature heart cells in a lab is not new, raising them to behave like adult cells is. Radisic’s cutting-edge developmen­t arrived in the form of a device that jolted the patches with a series of shocks. It encouraged the cells to march to a beat that mimicked an adult’s heart muscle. “We actually kind of zap the tissues with regular, short pulses,” she said. “As we pace them, they think they are real hearts.”

The heart tissue only beats after it is stimulated, just like a working heart muscle should, Radisic explained.

Six drug companies have been testing their heart disease drugs on the mini-hearts.

The Canada Research Chair believes it is only a matter of time before engineers can model, farm and grow other organs such as the liver. It’s a vision of the future that takes a page from science fiction, where stem cells and biomateria­ls repair, regenerate or even replace diseased or broken tissues and organs.

“If I apply a drug to the liver and it gets metabolize­d there, how does it affect the heart?” she asked. “Or is there a drug that will kill tumour cells without killing the heart?”

Aside from aiding science’s understand­ing of heart attacks and disease, the mini-heart could also revolution­ize the pharmaceut­ical industry.

Drug manufactur­ers now have the opportunit­y to test their cardiac medication­s on human-like tissue without having to rely on animal testing first.

The pharmaceut­ical industry is only 75 to 90 per cent sure of the safety of the drug before beginning human trials because they rely on tests using animal cells,” Radisic said. “For heart tissue, people often use rats and mice, but their cells don’t emulate human physiology in every aspect.

“It’s also a lot more difficult to work with pigs and monkeys due to both cost and ethical concerns.”

“For heart tissue, people often use rats and mice, but their cells don’t emulate human physiology in every aspect."


For now, with an army of mini hearts at her disposal, Radisic is confident that her engineered heart tissue will not only lead to a better grasp of heart disease, but also a future filled with safer more efficient drugs.

“For most researcher­s, part of the reason you do this is because you want to see something that never existed go from an idea to an applicatio­n that can impact real people,” she said. “So it is a huge level of personal satisfacti­on to see that come full circle.”

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