The heart has its own nervous system to control the heartbeat, according to a study in zebrafish, which may provide new insights into treating cardiovascular diseases.

Researchers at the Karolinska Institute, Sweden, and Columbia University, New York, USA, studied the hearts of zebrafish – which share similarities with human heart rate and function – by mapping out the different neurons within the organ.

The team identified a diverse range of neurons and saw that one type had characteristics that were similar to so-called pacemaker neurons – found in the central nervous system (the brain and spinal cord) – which send electrical impulses to the heart to make it beat regularly.  

This challenges the previous assumption that heart rate is controlled through the autonomic nervous system, which transmits signals from the brain to control different functions in the body.

Lead author Konstantinos Ampatzis, at Karolinska, said: “We were surprised to see how complex the nervous system within the heart is.

“Understanding this system better could lead to new insights into heart diseases and help develop new treatments for diseases such as arrhythmias [irregular heartbeat].”

Researchers in Germany have developed a heart organoid that is capable of producing blood, to improve the study of heart development and diseases.

The study at EARA member Hannover Medical School created organoids in the lab from human pluripotent stem cells (HPSCs), which have the ability to develop into any cell type.

With the addition of specific biological and chemical signals to the cell culture, the HPSCs then combine before developing into 3D structures that resemble aspects of the human heart.

The researchers were then able to make the organoid generate blood by adding blood vessel linings to the organoid, from which blood-forming cells emerged.

It is hoped that this breakthrough will allow the biology of the heart to be studied with greater accuracy, while also holding the potential to investigate diseases that attack the heart, such as Covid-19, genetic defects, and the effect of treatments.