Aging in the Skeletal Muscle Revealed by Molecular Immunohistochemical Imaging

The skeletal muscle is a complex organ mainly composed of multinucleated fibres responsible for contractile activity, but it also contains postnatal myogenic stem cells (i.e., satellite cells), connective cells and nervous cells. The skeletal muscle is severely affected by aging, undergoing a progressive reduction in muscle mass, strength and endurance in a condition known as sarcopenia. The mechanisms underlying sarcopenia still need to be completely clarified, but they are undoubtedly multifactorial, involving all cell types constituting the skeletal muscle. Immunohistochemistry has widely been used to investigate skeletal muscle aging, identifying age-related molecular alterations in the various myofibre components, as well as in the satellite cells and peri-fibre environment. The wide range of immunohistochemical data reported in this review is proof of the primary role played by this long-established, yet modern, technique. Its high specificity for the molecules of interest, and the possibility of imaging and quantifying the signal in the real histological or cytological sites where these molecules are located and active, makes immunohistochemistry a unique and irreplaceable tool among the laboratory techniques in biomedicine.