Direction-Dependent Stretch Drives Stage-Specific Remodeling in a COPD-Relevant Muscle Model

Respiratory muscle dysfunction contributes to disease progression in chronic obstructive pulmonary disease (COPD), yet the mechanobiological effects of altered strain direction on diaphragm remodeling remain poorly understood. Current in vitro models rarely reproduce the dynamic mechanical transitions experienced by respiratory muscles during COPD progression. To address this limitation, we developed a programmable muscle culture platform capable of delivering uniaxial (U) and equibiaxial (E) cyclic stretch in defined temporal sequences.

Human skeletal muscle cells (SkMCs) cultured on the platform maintained organized myogenic architecture, confirmed by MyoD, α-actinin, Ki67, and vinculin staining. Equibiaxial stretch preserved expression of YAP, WNT1, ITGB6/8, and MYOG, whereas uniaxial stretch increased COX-2 expression and p38 activation, indicating enhanced stress-associated signaling.

To model disease progression, sequential stretch paradigms (E4, E2U2, U2E2, and U4) were applied. Analyses of COL1A1, myogenin, integrin α5, and cytokine profiling of PAI-1 (SERPINE1) and MIF identified stage-specific remodeling phenotypes. E4 represented physiological adaptation, E2U2 early remodeling, U2E2 a maladaptive transition with elevated remodeling mediators, and U4 a sustained pathological state with persistent stress signaling.

These findings demonstrate that altered strain direction alone can induce progressive remodeling signatures relevant to COPD-associated diaphragm dysfunction. This programmable mechanobiology platform provides a physiologically relevant in vitro model for investigating stretch-driven remodeling and evaluating therapeutic strategies for respiratory muscle dysfunction in COPD.