Israeli scientists have created a minuscule beating heart using stem cells that is smaller than a grain of rice.

The tiny heart model, which is around the same size as half a grain of rice, has been hailed as a “game changing” development, marking a “new era in cardiovascular research”.

Unlike previous models, which have been composed solely of heart muscle cells, this version contains all the essential features of a beating heart including ventricles, atria, an outer shell and inner lining, researchers said.

Known as an “organoid” – a self-organised 3D tissue that is typically derived from stem cells – when the heart is connected to a sensor, researchers can track metabolic and electrical activity. 

The team, led by Professor Yaakov Nahmias of the Hebrew University of Jerusalem, Technion-Israel Institute of Technology and biotech company Tissue Dynamics, said its work has the potential to transform drug testing and cardiovascular research.

Organoids such as this grant scientists a depth of analysis customarily possible only with non-human model organisms, which have their drawbacks.

“If you want to study the heart, you have a huge problem if you’re using animals,” Nahmias told The Times of Israel.

“A lot of things like the channels in the mice hearts are very different from humans and a lot of the drugs and a lot of the diseases simply don’t translate.”

Prof. Nahmias

Professor Nahmias, who led the research team, hopes to start producing brain organoids within the next two years (Photo: handout)

The development of human organoids has been a steadily evolving pursuit. In 2022, a team at Israel’s Weizmann Institute of Science created the first synthetic mouse embryo, while Tissue Dynamics has previously synthesised human kidney and liver models.

This latest research goes a step further  and, thanks to their size, parallel tests can be carried on up to 20,000 organoids at a time.

“One of the most significant features of this heart model is its ability to provide real-time measurements of essential parameters such as oxygen consumption, extracellular field potential, and cardiac contraction,” said Hebrew University.

“This capability enabled the scientists to gain unprecedented insights into heart function and diseases, making it a game-changer in the field of cardiovascular research.”

Scientists have already made “ground-breaking” discoveries thanks to the miniature beating hearts. Notably, the heart model unveiled a new form of cardiac arrhythmia, distinct from those observed in traditional animal models, according to a study published in the journal Nature Biomedical Engineering.

These little hearts are only the beginning, however, according to Nahmias.

“In two years, my lab would like to be producing brain organoids,” he said.

“That is the next frontier.”