Rejuvenating radiation

Radiotherapy rejuvenated the cardiomyocytes of mice and helped them to carry out the pulse faster

Anastasia Kuznetsova-Fantoni, N+1

American doctors have found out that radiotherapy, which is used to treat cardiac arrhythmias, triggers signaling pathways in the myocardium that are active in embryogenesis, and thereby improves its conducting function. To understand this, doctors analyzed RNA from the myocardium of mice that received a dose of ionizing radiation to the heart area. Doctors believe that radiotherapy has helped cardiomyocytes to return to a young state and begin to work better. The study was published in Nature Communications (Zhang et al., Cardiac radiotherapy induces electrical conduction reprogramming in the absence of transmural fibrosis).

In order to eliminate cardiac arrhythmias that occur due to an additional focus of automatism, this focus is removed. Such an operation is called ablation, and to destroy the area generating pathological impulses, it uses either radio frequency electromagnetic energy or freezing of tissues to -70 degrees Celsius. Recently, a new method of ablation using small doses of gamma radiation has appeared. In clinical studies , he has shown its effectiveness in the treatment of patients with treatment—resistant arrhythmia - the number of attacks of ventricular tachycardia in them decreased by 94 percent. In such difficult patients, it is not always possible to achieve a good result by other methods of ablation.

It was believed that ablation with the help of radiation acts similarly to the rest of its types — destroys the focus of automatism. American researchers have noticed that the effect of it develops very quickly — within a few days, not months, as with other types of ablation. A team of cardiologists led by Stacey L. Rentschler from Washington University in St. Louis decided to figure out why after exposure to radiation on the heart muscle, the effect occurs so quickly.

First, doctors analyzed the structure of the heart of four deceased patients who had radiation ablation during their lifetime. The researchers noticed that the spread of fibrosis in the areas after radiotherapy did not differ from the spread of fibrosis in other areas of the heart, which means it is unlikely that fibrosis of the foci of automatism facilitated the condition of patients.

The scientists continued further experiments on the hearts of six mice, which were exposed to ionizing radiation (a dose of 25 gray). Doctors were convinced that radiotherapy accelerates the conduction of an electric pulse through the myocardium. The researchers then sequenced RNA from the heart (using bulk RNA sequencing) 2 weeks and 6 weeks after exposure to radiation to see how gene expression changed. To do this, experimental mice were compared with a control group (6 animals).

It turned out that radiotherapy activated the Notch signaling pathway in the myocardium, and with it the sodium channels. Apparently, this eliminated the arrhythmia in people. The Notch pathway is involved in embryogenesis, and does not work in adult animals.

Doctors believe that activation of the Notch signaling pathway allows cardiomyocytes to return to a young state and improve their functions. In further studies, doctors will work to reduce the dose of ionizing radiation to minimize possible negative side effects in patients.

Cardiology is constantly developing new methods of treating diseases. So recently, a patient with ischemic cardiomyopathy was transplanted patches with cardiomyocytes obtained from induced pluripotent stem cells.

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