Damaged, sick and old muscles will be restored by Pax7

Muscle Repair Protein
Scientists have found out how damaged muscles are repairedNadezhda Markina, <url>

The restoration of damaged muscle tissue is due to satellite cells.

And they can't function without a special protein, scientists have found out.

Muscles have a remarkable ability to heal themselves. With the help of training, you can restore them after injury, and age-related atrophy is overcome with an active lifestyle. When stretching, the muscles hurt, but usually the pain goes away after a few days.

Muscles owe this ability to satellite cells - special cells of muscle tissue that are adjacent to myocytes, or muscle fibers. The muscle fibers themselves – the main structural and functional elements of the muscle – are long multinucleated cells that have the property of contraction, since they include contractile protein filaments – myofibrils.

Satellite cells are, in fact, stem cells of muscle tissue. In case of damage to muscle fibers that occur due to injuries or with age, satellite cells divide intensively. They repair damage by merging together and forming new multicore muscle fibers. With age, the number of satellite cells in muscle tissue decreases, respectively, the ability of muscles to recover, as well as muscle strength, decreases.

Scientists from the Max Planck Society's Institute for the Study of the Heart and Lungs (Germany) have found out the molecular mechanics of muscle self-repair using satellite cells, which has not been thoroughly known until now. They wrote about the results in the journal Cell Stem Cell (Gunther et al., Myf5-Positive Satellite Cells Contribute to Pax7-Dependent Long-Term Maintenance of Adult Muscle Stem Cells).

Their discovery, according to scientists, will help to create a method of muscle recovery, which one day can be transferred from the laboratory to a clinic for the treatment of muscular dystrophy. And maybe muscle old age.

Researchers have identified a key factor – a protein called Pax7, which plays a major role in muscle regeneration. Actually, this protein in satellite cells has been known for a long time, but experts believed that the protein plays the main role immediately after birth. It turned out that it is indispensable at all stages of the body's life.

To find out exactly its role, biologists created genetically modified mice in which the Pax7 protein in satellite cells did not work. This led to a radical reduction of the satellite cells themselves in the muscle tissue. The scientists then caused damage to the mouse muscles by injecting the toxin. In normal animals, the muscles began to regenerate intensively, and the damage healed. But in genetically modified mice without the Pax7 protein, muscle regeneration has become almost impossible. As a result, biologists observed a large number of dead and damaged muscle fibers in their muscles. Scientists regarded this as proof of the leading role of the Pax7 protein in muscle regeneration.

The muscle tissue of the mice was examined under an electron microscope. In mice without the Pax7 protein, biologists found very few preserved satellite cells that were very different in structure from normal stem cells. Organelle damage was noted in the cells, and the state of chromatin – DNA in combination with proteins, which is normally structured in a certain way, was disturbed.

Diagram from an article in Cell Stem Cell – VMInterestingly, similar changes appeared in satellite cells that were cultured for a long time in the laboratory in an isolated state, without their "hosts" – myocytes.

The cells degraded in the same way as in the body of genetically modified mice. And scientists found in these degraded cells signs of deactivation of the Pax7 protein, which was observed in mutant mice. Further – more: isolated satellite cells stopped dividing after some time, that is, stem cells ceased to be stem cells.

If, on the contrary, the activity of the Pax7 protein in satellite cells is increased, they begin to divide more intensively. Everything points to the key role of the Pax7 protein in the regenerative function of satellite cells. It remains to figure out how to use it in potential cellular therapy of muscle tissue.

"When muscles degrade, for example, in muscular dystrophy, implantation of muscle stem cells will stimulate regeneration,– explains Thomas Brown, director of the institute. – Understanding how Pax7 works will help to modify satellite cells in such a way as to make them as active as possible. This may lead to a revolution in the treatment of muscular dystrophy and, perhaps, will preserve muscle strength in old age."

And healthy muscles and physical activity in old age are the best way to push back age–related diseases.

Portal "Eternal youth" http://vechnayamolodost.ru26.08.2013