Researchers discover that released protein aids in muscle repair and growth

According to study from Tokyo Metropolitan University, a protein known as platelet-derived growth factor subunit B (PDGF-B), which is constantly secreted by skeletal muscle cells, has been discovered to help in muscle regeneration by stimulating the creation of myoblasts, or muscle stem cells. Surprisingly, scientists observed that PDGF-B also increases muscle fibre development. They discovered that this corresponded to the greater contraction of the fibres. The drugs they identified have the potential to change the way we treat muscular injuries and atrophy. Skeletal muscle cells release myokines, which are tiny proteins. They serve a variety of roles and can operate on cells both close and far from where they are produced.

A whole picture of how myokines impact cellular processes is yet unknown, although they are thought to play a significant role in exercise-related body activities, notably muscle tissue preservation. A team lead by Associate Professor Yasuko Manabe at Tokyo Metropolitan University has been investigating how myokines influence muscle cell behaviour. They discovered that platelet-derived growth factor subunit B, or PDGF-B, is released by skeletal muscles in a constitutive manner, that is, without any trigger.

They exposed myoblasts, precursor cells that develop into muscle fibres, to PDGF-B to learn more about its involvement. They were able to convincingly demonstrate that PDGF-B increased myoblast proliferation. Surprisingly, they discovered that PDGF-B had an effect on cells that had already differentiated. They subjected myotubes, a step of muscle fibre formation, to the same myokine. Myotubes treated in this manner matured considerably faster, with visible increases in diameter under a microscope.

They also have higher levels of Myosin Heavy Chain, which is a component of the protein structure of myosin, the molecular motor responsible for muscle contraction. This was demonstrated to directly correspond to enhanced contractile strength using a recently developed approach based on examining how myotubes responded to an electric pulse. As a result, PDGF-B not only promotes muscle growth but also strengthens it.

However, this does not imply that both processes are increased haphazardly. They discovered modest changes in PDGF-B signalling pathways between myotubes and myoblasts, which they believe are important in cells transitioning from a proliferating to a maturing phase.