Nanotechnological Strategies to Promote Skeletal Muscle Regeneration in Aging.

During aging, skeletal muscle undergoes a decline in mass and strength. This condition, known as sarcopenia, involves many physiological and metabolic impairments, thus representing a healthcare, social, and economic burden. Various pharmacological and non-pharmacological approaches have been explored to counteract sarcopenia; however, no definite treatment has so far been found. The present narrative review summarizes nanotechnology-based strategies designed to promote muscle preservation and functional recovery in aging. Synthetic organic or inorganic nanoconstructs and natural extracellular vesicles have been used as nanocarriers for drug delivery, have been active as intrinsic therapeutic agents, have been employed to build biomimetic nanoscaffolds to sustain muscle regeneration, or have been combined to form hybrid nanosystems with multiple therapeutic functions. These nanotools demonstrated promising results in vitro and in animal models, being able to counteract major factors responsible for sarcopenia, such as oxidative stress, inflammation, mitochondrial dysfunction, increased proteolysis, and impaired stem cell function. However, nanotools have mostly been tested on biological models far from the physiologically aged human muscle. Moreover, limitations still remain to be solved to make these nanotools suitable for regenerative medicine; in particular, the systemic administration requires nanoconstruct functionalization for skeletal muscle targeting, and proper clearance should be ensured to avoid toxicity and immunogenicity related to long-term use.