Rivares, C. | Search bioRxiv

bioRxiv2025

Long-Term Functional 3D Human Skeletal Muscle Constructs from Human Induced Pluripotent Stem Cells Enable Electrically Controlled Remodelling Studies

Studying skeletal muscle remodelling across large temporal scales is difficult because most 3D tissue-engineered skeletal muscle (3D-TESM) models cannot sustain stable development over prolonged culture. Skeletal muscle adaptations in vivo are strongly influenced by changes in tissue length, but most TESM models are mechanically restrictive, limiting elongation and thereby constraining structural remodelling. The stiffness of the pillars that anchor the tissues is a key determinant of how much they can shorten or elongate during development, thereby shaping both their morphology and force-generating capacity. To address this limitation, we investigated how TESMs derived from human induced pluripotent stem cells (hiPSCs) develop over two weeks when suspended between pillars with distinct mechanical properties, ranging from mechanically compliant to mechanically stiff boundary conditions. We focused on both passive and active force-generating properties. With compliant pillars, tissues compacted primarily along their length (~66% reduction), followed by progressive elongation (~50% increase) from day 5 onward. In contrast, with stiff pillars, tissues compacted across their width, with no longitudinal shortening. Despite these morphological differences, projected tissue area decreased similarly across setups. Spontaneous contractions emerged from day 7 and continued until day 14, typically occurring in bursts at 0.6-0.8 Hz. Passive force peaked early with compliant pillars and declined thereafter, while remaining relatively stable with stiff pillars. Under stepwise electrical stimulation, maximal contractility wasconsistently observed at ~50 Hz. Active force rose sharply between day 12 and day 14, with the steepest increase (up to 2000%) in compliant pillars. Although sample size was limited, the consistency of trends across stiffness conditions and surface treatments provides valuable insights into how boundary mechanics shape 3D-TESM development. These findings offer a foundation for designing next-generation muscle culture systems that support dynamic remodelling, force maturation, and training-responsive behaviours. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=95 SRC="FIGDIR/small/672872v2_ufig1.gif" ALT="Figure 1"> View larger version (27K): org.highwire.dtl.DTLVardef@4caa3borg.highwire.dtl.DTLVardef@13c421dorg.highwire.dtl.DTLVardef@11881a1org.highwire.dtl.DTLVardef@1e673a4_HPS_FORMAT_FIGEXP M_FIG C_FIG

bioengineering↗

bioRxiv2020

Glycine receptor subunit-β -deficiency in a mouse model of spasticity results in attenuated physical performance, growth and muscle strength

Spasticity is the most common neurological disorder associated with increased muscle contraction causing impaired movement and gait. The aim of this study was to characterize physical performance and skeletal muscle function and phenotype of mice with a hereditary spastic mutation (B6.Cg-Glrbspa/J). Motor function, gait and physical activity of juvenile and adult spastic mice and the morphological, histological and mechanical characteristics of their soleus (SO) and gastrocnemius medialis (GM) muscles were compared with their wild-type (WT) littermates. Spastic mice showed attenuated growth, impaired motor function and low physical activity. Gait of spastic mice was characterized by a typical hopping pattern. Spastic mice showed lower muscle forces, which were related to the smaller physiological cross-sectional area of spastic muscles. The muscle-tendon complex length-force relationship of adult GM was shifted towards shorter lengths, which was explained by attenuated longitudinal tibia growth. Spastic GM was more fatigue resistant than WT GM. This was largely explained by a higher mitochondrial content in muscle fibers and relatively higher percentage of slow type muscle fibers. Muscles of juvenile spastic mice showed similar differences compared to WT juvenile mice, but these were less pronounced than between adult mice. This study shows that in spastic mice, disturbed motor function and gait is likely the result hyperactivity of skeletal muscle and impaired skeletal muscle growth, which progress with age.

physiology↗