The organoid developed at the Technical University of Munich could prove helpful to researchers studying heart development and cardiovascular diseases.

Scientists from Germany have made a major breakthrough in stem cell research, successfully inducing stem cells to replicate the earliest stages of human heart development. This breakthrough has the potential to revolutionize the study of heart development and cardiovascular diseases.

The human heart starts forming approximately three weeks after conception. This means that the early phase of heart development occurs during a time when women are often still unaware of their pregnancy, making it difficult to gain a comprehensive understanding of how the heart forms.

The organoid developed at the Technical University of Munich (TUM) could prove helpful to researchers in connecting the dots.

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A ball of 35,000 cells

Researchers have created a technique for developing a “mini-heart” out of pluripotent stem cells. Around 35,000 cells are spun into a sphere in a centrifuge.

“In this way, we mimic the signaling pathways in the body that control the developmental program for the heart,” explains Alessandra Moretti, senior researcher in the team.

First-ever “epicardioids”

The resulting organoids are about half a millimeter in diameter. Although they do not pump blood, they can be stimulated electrically and are capable of contracting like human heart chambers. Prof Moretti and her team are the first researchers in the world to successfully create an organoid containing both heart muscle cells (cardiomyocytes) and cells of the outer layer of the heart wall (epicardium).

“To understand how the heart is formed, epicardium cells are decisive,” says Dr. Anna Meier, first author of the study. “Other cell types in the heart, for example in connecting tissues and blood vessels, are formed from these cells. The epicardium also plays a very important role in forming the heart chambers.”

The team has appropriately named the new organoids “epicardioids”.

New cell type discovered

Along with the method for producing the organoids, the team has reported its first new discoveries: By examining individual cells, they have determined that precursor cells of a type only recently discovered in mice are formed around the seventh day of the development of the organoid. The epicardium is formed from these cells.

“We assume that these cells also exist in the human body – if only for a few days,” says Prof Moretti.

These insights may also offer clues as to why the fetal heart can repair itself, a capability almost entirely absent in the heart of an adult human. This knowledge could help find new treatment methods for heart attacks and other conditions.

‘Personalized organoids’

The research that was published in Nature Biotechnology also showed that the organoids can be used to investigate the illnesses of individual patients. Over the coming months, the team plans to use comparable personalized organoids to investigate other congenital heart defects. With the possibility of emulating heart conditions in organoids, drugs could be tested directly on them in the future.

“It is conceivable that such tests could reduce the need for animal experiments when developing drugs,” says Alessandra Moretti.

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