How slow muscle fibers convince their neighbors to join them

The university is Tokyo Metropolitan University.

A team of researchers from Tokyo Metropolitan University have found a way to make myoblasts differentiate into type I fibers. The prevailing wisdom is that our fast/ slow fiber ratio can't be changed. They were able to identify the pathway by which the molecule affects the cells. One day, these findings could lead to therapies for slow muscle health.

Skeletal muscles are made up of hundreds of thousands of fibers. They aren't all the same. There are two types of muscle fibers: slow type I and fast type II. There are two types of fibers: type I and type II. The ratio of type I to type II fibers in our muscles is largely determined at birth.

Scientists are finding that this isn't the case. A team of researchers from Tokyo Metropolitan University led by Professor Nobuharu Fujii have found that Rspo3 may be the key to the development of new type I fibers. When myoblasts were treated with Rspo3 they began to produce more Myosin Heavy Chain I.

The effect was unique to myoblasts. This means that the formation of more type I fibers is stimulated by excreting Rspo3 and acting on nearby cells. Conventional wisdom says that the ratio of type I to type II fibers cannot be changed, but the finding sheds new light on the role of muscles in our bodies. The team was able to show that this happened through a specific cascade of chemical reactions called the Wnt/Beta-catenin pathway. Experiments to artificially reduce the amount of beta-catenin in cells resulted in suppression of MyHC I expression.

Lack of exercise and type 2 diabetes are two of the causes of slow muscle fibers. It is possible to encourage the development of type I fibers through therapeutic means, according to the findings of the team. It is possible to differentiate muscle cells taken from a patient before the tissue is replanted. The benefits will be more than just the mass that is reintroduced if cells can excrete Rspo3. A key challenge for aging populations and society is the improvement of muscular function.

The study was published in scientific reports.

More information: Yoshitaka Mita et al, R-spondin3 is a myokine that differentiates myoblasts to type I fibres, Scientific Reports (2022). DOI: 10.1038/s41598-022-16640-2 Journal information: Scientific Reports Provided by Tokyo Metropolitan University