A Monolithic 3D-Printed Platform for Functional Maturation and In Situ Contractility Assessment of 3D Skeletal Muscle

Sarcopenia-a debilitating consequence of global population aging characterized by the loss of muscle mass and function-demands in vitro platforms that enable a rigorous and quantitative assessment of muscle contractility. Pillar-displacement-based microphysiological systems are promising for this purpose but suffer from tension loss as tissues compact, creating variable boundary conditions and undermining reliability. We developed a monolithic, 3-dimensional printed Fast-Optimizing and Regeneration/Contraction-Evaluating platform featuring a detachable polydimethylsiloxane spacer that maintains a constant interpillar distance during long-term culture. The monolithic structure, fabricated by stereolithography, ensures high architectural reproducibility. Under the fixed-length boundary conditions, engineered muscles exhibited improved cellular alignment, enhanced myogenic differentiation, and more advanced structural maturation, resulting in markedly higher twitch and tetanic forces upon electrical stimulation. Together, these results establish the Fast-Optimizing and Regeneration/Contraction-Evaluating platform as a robust and reproducible muscle microphysiological system with fixed-length boundary conditions, enabling reliable, long-term quantitative evaluation of morphological and functional changes for tissue-engineering, drug-screening, and muscular-disease-modeling applications.