Scientists have created very small, beating human hearts in a laboratory. These tiny hearts are about the size of a sesame seed and can be seen moving in a dish. They beat regularly, like real hearts. These "cardiac organoids" were made by researchers at Michigan State University, led by Aitor Aguirre. They started developing their methods in 2020.
To make these organoids, the scientists used human stem cells. Stem cells can change into different types of cells, including heart cells. The organoids formed chambers and blood vessels, similar to real hearts. Aguirre explained that these organoids have chambers, muscle, and electrical signals that work like human hearts.
This is important because heart disease is a major cause of death. Previously, scientists used animal models, like mice, to study heart problems. However, mouse hearts are different from human hearts, which made research difficult. For example, a condition called atrial fibrillation, where the heart beats irregularly, affects millions of people. Animal models have not helped find new treatments for it in over 30 years.
The Michigan State University team added immune cells called macrophages to the organoids. These cells help the heart develop and stay healthy. When the organoids were exposed to inflammation, their cells started beating irregularly, just like in human atrial fibrillation. When an anti-inflammatory drug was given, the heart rhythm improved. This shows that scientists can now test medicines on human heart tissue in the lab. They even developed a special sensor to watch how the organoids beat. A company called Cytohub has licensed this technology to develop it further.