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Extracellular vesicles act as communication mode between stem cells and muscle fibers

Rockville, Md. (July 23, 2020)—A new study suggests that communication between skeletal muscle cells and muscle fibers promotes muscle growth. Adult muscle stem cells, called satellite cells, release extracellular vesicles that are delivered to muscle fibers responsible for contraction to promote this muscle growth. The first-of-its-kind study is published ahead of print in the journal Function.

Satellite cells add new nuclei—containing genetic material—to growing muscle fibers during adult muscle growth (hypertrophy) that occurs in response to activities such as muscle training. This process of adding new nuclei is called fusion. Emerging evidence suggests that satellite cells play a more diverse role, broadly influencing the muscle fiber environment to promote maximal muscle growth.

Extracellular vesicles are message-containing particles released by cells, facilitating communication between cells during processes such as blood clotting and immune response. Satellite cell-derived vesicles have been shown to communicate with cells called fibroblasts to support tissue remodeling in mice during hypertrophy.

Researchers from the University of Kentucky studied satellite cell function using a mouse model of muscle hypertrophy that mimicked resistance training in humans. Satellite cells are located very close to muscle fibers and are known to communicate with non-muscle cells to help promote muscle adaptation and repair. However, little is known about how they communicate with muscle fibers aside from adding new nuclei. The research team discovered that satellite cells communicate with muscle fibers through extracellular vesicles and regulate muscle fiber expression of matrix metalloproteinase 9, an enzyme involved in inflammation, tissue remodeling and wound healing. The researchers found this intercellular communication helped contribute to muscle building even before the satellite cells fused with muscle fibers. This suggests that the addition of new nuclei may not be the only means by which satellite cells support muscle fiber growth. Changes in this communication with muscle fibers may contribute to the loss of muscle adaptability that occurs with aging.

“The effect of satellite cell [extracellular vesicles] directly on muscle fibers should not be overlooked,” the research team wrote. These findings “point to new therapeutic frontiers for targeting these cells to preserve or enhance muscle mass.”

Read the full article, “Fusion-independent satellite cell communication to muscle fibers during load-induced hypertrophy,” published ahead of print in the journal Function.

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