A healthy heart beats around two billion times throughout a person’s life, thanks to the interaction of a large number of proteins. And, thanks to a team of researchers from Munich, we now know exactly how many: more than 10,000.
Researchers from the Max Planck Institute for Biochemistry (MPIB) and the German Heart Center of the Technical University of Munich (TUM) have determined how many individual proteins are present in each cell type and function of the heart.
This finding represents the first map of the healthy human heart, known as the cardiac proteome.
This new map will make it easier to identify the differences between healthy and diseased hearts in the future.
Proteins are molecular machines in cells, in which a wide variety of functions are involved. Changes that occur at the DNA or protein level can lead to disorders. For these changes to be recognized as underlying causes of heart disease, it is important to know precisely which proteins are present in a healthy heart and in what quantities.
One function for each half
One of the most surprising discoveries this map has allowed is that the right and left halves of the heart are similar, despite having quite different functions.
Specifically, the right half pumps oxygen-poor blood to the lungs, while the left half pumps oxygen-rich blood from the lungs to the body.
To design it, the scientists determined the protein profile of cells in all regions of the heart, such as the heart valves, heart chambers and major blood vessels.
In addition, they investigated the protein composition in three different types of heart cells : cardiac fibroblasts, smooth muscle cells, and endothelial cells.
In this way, the researchers were able to ‘map’ the distribution of proteins in the various regions of the heart. Using mass spectrometry, they identified nearly 11,000 different proteins throughout the heart.
Previous studies mostly focused on individual cell types only, or used tissue from diseased hearts. “There were two problems with this approach,” according to Sophia Doll, lead author of the study. “The first, that the results did not provide a complete picture of the heart in all its regions and tissues; second, comparative data on healthy hearts was often lacking.
But the new study eliminates both problems. Now, the data can be used as a reference for future studies.
By looking at the protein map of the human heart, it can be seen that all healthy hearts function similarly : the researchers measured similar protein compositions in all regions with little difference between them.
In addition, the team wanted to see if the data from healthy hearts could serve as a control to detect changes in diseased hearts. Thus, they compared their values with the cardiac proteomes of patients with atrial fibrillation , a very common heart rhythm disorder.
And indeed, the results provided initial clues to the cause of this disease : the tissue of diseased hearts was very different in the proteins responsible for supplying energy to cells.
The importance of personalized medicine
The map also provided another interesting finding: although the proteins involved in energy metabolism were modified in all patients, these changes differed between individuals. Although all the patients had very similar symptoms, they present a different molecular dysfunction in each case.
Therefore, we need to learn to recognize and treat such individual differences, especially in cardiac medicine.
