Mini heart for research: Organoid is smaller than a pinhead

German researchers have developed a novel miniature heart. It's significantly smaller than the head of a pin, yet can beat independently. The so-called organoid is intended to help researchers identify early on which medications could damage the heart. Many new drugs used to combat diseases like cancer fail in later stages of development due to their "potential cardiotoxicity," according to a press release from the Fraunhofer Society .

New active ingredients can be researched more specifically in human mini-organs than in animal experiments, which are already being restricted. For the mini-heart, researchers have developed so-called pluripotent stem cells into cardiac muscle, connective tissue, and vascular cells.

They allowed the cell mix to grow in a Petri dish. Within four days, the cells self-organized and formed a spherical organoid structure with approximately 2,000 cells. The miniature heart began beating spontaneously and can also be stimulated to contract using electrical stimulation.

Beating mini heart even has its own immune system

Scientists from the Fraunhofer Institute for Toxicology and Experimental Medicine (ITEM) and the Hannover Medical School were involved in its development. Their miniature heart can be used to test the effects of virtually any drug down to the single-cell level. This includes cutting-edge immune, cell, and gene therapies.

Diseases can also be modeled here – from cardiac arrhythmias and heart attacks to cardiac hypertrophy, the thickening of the heart muscle. The miniature heart even has its own immune system – thanks to the addition of macrophages, or phagocytes.

The importance of the heart for overall human health was recently the focus of an international conference in Heidelberg with the participation of the Max Delbrück Center (MDC) Berlin. We now know that the heart and blood vessels together "form a kind of communication center and exchange information with all other organs," said Norbert Hübner, a researcher at the MDC. A new field of research—AngioCardioScience—aims to explore this dynamic interplay, which is also considered the key to healthy aging.

The heart is more than just a pump. Or, as Leo Tolstoy once put it: "In the human heart lies the beginning and the end of all things."