In vitro development of a muscle-tendon junction construct using decellularised extracellular matrix: Effect of cyclic tensile loading

This study evaluated decellularised extracellular matrix (DECM) derived from sheep muscle-tendon junction (MTJ) as a scaffold to drive MTJ marker expression and lineage-specific differentiation of human mesenchymal stem cells (MSCs), and assessed how cyclic uniaxial strain modulates these outcomes. DECM retained MTJ-region structure, supported high MSC viability (>90% through 14 days), and increased MTJ-associated marker expression versus 2D controls, including collagen type 22 (COL22A1) and paxillin at gene and protein levels. When cyclic strain was applied, COL22 protein deposition increased (notably at day 14), but MTJ marker gene expression (COL22A1,PAX,TALIN2) was reduced compared with static DECM culture. Spatially, MTJ markers were most prominent in cells located adjacent to the MTJ region, supporting the concept that the native MTJ-derived matrix provides positional differentiation cues. Strain shifted lineage outcomes: cyclic loading enhanced myogenic differentiation (increased desmin and other myogenic markers on the muscle side) while reducing tenogenic differentiation signals (reduced scleraxis expression and reduced tenomodulin deposition on the tendon side), indicating that the selected loading regimen may be closer to an “overload” condition for tenogenic commitment in this DECM context.