In Vitro and In Vivo Comparative Analysis of Muscle Regenerative Processes Induced by Different Microcurrent Waveforms in Skeletal Muscle Atrophy

This study aimed to evaluate the regenerative effects of various microcurrent waveforms in cast-induced gastrocnemius muscle atrophy in rabbits, integrating both in vitro and in vivo analyses. After two weeks of enforced hindlimb immobilization via casting, twenty-four rabbits were divided into four groups and treated for two weeks: Group-1 (control) received sham microcurrent, Group-2 was treated with a square waveform microcurrent, Group-3 with a sine waveform, and Group-4 with a triangular waveform. Treatments were administered daily for one hour. Calf circumference, muscle thickness (via ultrasound), tibial nerve CMAP, muscle fiber CSA, and protein expression (via Western blot analysis) were assessed. Among the groups, the sine waveform microcurrent resulted in significantly enhanced recovery across all measured parameters (<i>p</i> < 0.05), showing superior improvements in muscle thickness, CMAP amplitude, and fiber CSA. Immunohistochemical analysis revealed increased expression of proliferation and angiogenesis markers, including BrdU, PCNA, VEGF, and PECAM-1, while Western blotting demonstrated robust upregulation of myogenic regulatory factors such as MyoD and myogenin. Furthermore, levels of inflammatory and apoptotic markers, including TNF-α, NF-κB, and cleaved caspase-3, and stress response proteins, including p-CHK1 and p-CHK2, were markedly reduced. Collectively, these findings indicate that sine waveform microcurrent stimulation most effectively promotes muscle regeneration in both dexamethasone-induced C2C12 myoblasts and cast-induced muscle atrophy, underscoring its therapeutic potential and warranting further studies to optimize clinical application parameters.