Muscle and Bone Biology - Similarities and Differences

Muscle and bone are similar in many ways, and factors that can stimulate anabolism or catabolism in one of these tissues may have the same effect(s) either directly or indirectly on the other tissue. Factors that may enhance the mass and strength of both tissues include pleiotropic genes such as Methyltransferase-Like Protein 21C (METTL21C) and Myocyte Enhancer Factor 2C (MEF2C), hormones such as growth hormone (GH) and Insulin like growth factor-1 (IGF-1), dietary amino acids, resident populations of mesenchymal stem cells (e.g., satellite cells and bone marrow derived stem cells [BMSCs]) and resistance exercise early in life. Shared mechanisms of tissue loss and dysfunction include fatty infiltration, cellular senescence, and molecules such as myostatin that can drive both muscle and bone loss. Important differences between these two tissues include the decoupling of muscle and bone patterning early in limb development, contrasting mechanotransduction pathways (e.g., wnt signaling in bone and p70S6K signaling in muscle), and contrasting bone geometry between males and females and between the upper and lower limb relative to lean mass. Overall the number of similarities between muscle and bone exceed the differences. Dietary protein and resistance exercise early in life can together promote the accumulation of lean mass and bone mineral, whereas novel therapies such as senolytic agents or NAD+ repletion may potentially prevent loss of muscle and bone with aging.