New Insights into Neuromuscular Junction Biology: Evidence from Human and Animal Research

Neuromuscular junctions (NMJs) are highly specialized synapses that enable efficient communication between motor neurons and skeletal muscle fibers. Impaired formation or maintenance of NMJs is implicated in the pathogenesis of multiple neuromuscular disorders and contributes to age-related declines in skeletal muscle mass and strength. NMJ functionality is governed by complex regulatory crosstalk among different cells and is mediated by a diverse network of proteins. Moreover, immune cells often reside at NMJs and exhibit phenotypically different characteristics depending on the regenerative state of the muscle. These complex interfaces have posed a significant challenge for elucidating pathogenic mechanisms and developing biomarkers or effective targeted treatments. Many animal models have been developed to address this challenge by characterizing the fundamental structural features of neuromuscular junctions (NMJs) and their transmission capacity under both healthy and disease conditions. In contrast, studies of human NMJs remain limited, although emerging evidence is increasingly revealing substantial morphological and functional differences from animal NMJs. This review provides an overview of animal research on NMJs over the past decades, highlighting interspecies differences and key advances in our understanding of human NMJs.