The effect of green laser photobiomodulation on the density of myosatellite cells in regenerating skeletal muscle tissue

The regeneration of skeletal muscle tissue after injuries of various origins is an urgent medical problem. In regenerating muscle, activation of hyperchromic myosatellite cells occurs, associated with the expression of myogenesis factors, including MyoD, proliferation and differentiation of nuclei. The effect of low-intensity green (520 nm) laser photobiomodulation on tissue has been little studied to date, but it can be assumed that laser radiation in the green region of the spectrum has a stimulating effect on the regeneration of skeletal muscle tissue. The purpose of the study was to analyze the effect of low-intensity photobiomodulation with a green laser (520 nm) on the density of MyoD+ nuclei in regenerating muscle. Three experimental groups of animals were formed: 0 - control (rats with an intact muscle); I - rats with an incised wound of m. gastrocnemius; II - rats with green laser exposure to the wound area, 60 s in continuous mode. A morphometric analysis of histological sections stained with hematoxylin-eosin and immune-histochemical methods was carried out. The results of the study showed that under the influence of green photobiomodulation there was an increase in the density of hyperchromic nuclei at periods of 1 and 3 days of the experiment. In the group exposed to the green laser, a significant increase in the distribution density of MyoD+ nuclei were found on the 3rd day of the experiment, both in the wound site and intact zones. At the same time, there was a significant increase in the distribution density of MyoD+ nuclei in the wound site compared to the intact zone on the 1st, 3rd and 14th days of the experiment, which indicates an active replenishment of the pool of nuclei of the destroyed skeletal muscle fibers. For the first time, it was shown that the effect of a green laser on skeletal muscles promotes early activation of myosatellite cells on the 3rd day compared to the 7th day during natural healing of a muscle wound. In addition, there is a wider coverage of muscle tissue by` the reparative process, since after green photobiomodulation the number of MyoD+ nuclei increase not only in the wound site, but also around it.