Heart cells © Cell

Scientists have grown a beating mini heart organoid in the lab

The new heart models – about the size of a sesame seed – were created using 'self-organising' cells.

Here’s news that should get your blood pumping: researchers from Vienna’s Austrian Academy of Sciences have grown tiny 3D heart-like organs in a petri-dish. Made from human stem cells, these sesame-seed-sized cardiac models even beat like the real thing.

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Significantly, unlike previous versions of these tiny heart organs (called cardioids), the scientists didn’t use artificial scaffolding to bind the cells together. Instead, the cells organised themselves to grow a hollow chamber.

By creating more lifelike heart models, scientists are hoping to gain a better understanding of how the cardiac system responds to disease.

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While useful to past studies, cardioids created with the old scaffolding technique – known as tissue engineering, which arranges cells into artificial support frames akin to building a house out of brick and mortar – didn’t show the same physiological responses that a full-sized human heart does to damage.

In the embryo, human organs develop from stem cells through a process called self-organisation. This is where cellular building blocks interact with each other, move and change shape until an organic structure emerges.

The scientists in Vienna were able to replicate this process by activating signalling pathways in the stem cells. After one week of development, a hollow organoid grew that contracted rhythmically, able to squeeze liquid around its cavity.

“Self-organization is how nature makes snowflake crystals or birds behave in a flock. This is difficult to engineer because there seems to be no plan, but still something very ordered and robust comes out,” said lead researcher Dr Sasha Mendjan.

“The self-organization of organs is much more dynamic, and a lot is going on that we do not understand. We think that this ‘hidden magic’ of development, the stuff we do not yet know about, is the reason why currently diseases are not modelled very well.

“We want to come up with human heart models that develop more naturally and are therefore predictive of disease.”

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The scientists already have plans to grow cardioids with multiple chambers to improve understandings of how heart defects develop in foetuses.