How zebrafish repair their hearts
Prof. Dr. Nadia Mercader

"Our studies could explain why the human heart regenerates poorly."

Health and medicine

Efficient repair cells identified

Zebrafish can flexibly regenerate their hearts after injury – but how they do it exactly is not yet clear. A study by the University of Bern now shows that certain heart muscle cells play a central role in this process.

The zebrafish shares most of its genes with humans and is therefore an established animal model in biomedical research. The zebrafish are particularly suitable for examining heart regeneration: After a heart injury, their heart muscle cells divide and the scar is replaced by new muscle. A group led by Nadia Mercader at the Institute of Anatomy at the University of Bern has been studying this cellular repair process for ten years. In October 2019, the researchers were able to show that not all heart muscle cells in zebrafish contribute equally to the regeneration of lost muscle, but that there is a special "repair group" of heart muscle cells that does this particularly efficiently.

Essential for regeneration

The group led by Mercader teamed up with colleagues from the Interfaculty Bioinformatics Unit at the University of Bern as well as partner institutes in Germany and Spain. The team identified a small subset of the zebrafish’s heart muscle cells that expanded more than the rest of the cells in response to injury. This group of cells could be identified using transgenic tools labelling cells expressing a specific gene called "sox10". Deleting this small cell population disrupted heart regeneration in the zebrafish. "We were not only able to identify a specific cell population that is more efficient than all other heart muscle cells during regeneration, but also prove that its contribution to repair is essential," says Mercader. 

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"In human beings and other mammals, the heart muscle has trouble recovering from an injury. After an acute coronary, millions of heart muscle cells die and are replaced by a scar. Other vertebrates – such as the zebrafish – can recover from damage to the heart much better."

Significant for the repair process in the human heart

In a next step, the researchers would like to examine this cell population more closely: “We do not know if this is a specific group of cells present in the zebrafish heart of if few muscle cells can at a time activate sox10 and therefore contribute to regeneration", explains Mercader. The researchers believe that this finding could be of great importance in stimulating the repair process in the human heart.