3D GelMA–Chitosan constructs regulate mesenchymal stem cell fate via YAP-dependent mechanotransduction for spinal cord injury repair

Spinal cord injury (SCI) results in irreversible neuronal loss, cystic cavitation, and a chronically hostile microenvironment that severely limits endogenous repair. Conventional stem cell transplantation is frequently compromised by low cell survival, uncontrolled differentiation, and rapid cell loss. To address these challenges, we developed a mechano-responsive, three-dimensional bioprinted scaffold composed of gelatin methacryloyl (GelMA) and chitosan (CS), featuring an elastic modulus of 10.0 kPa, interconnected porous architecture, and photocrosslinkable bioactivity that recapitulate key mechanical characteristics of native spinal cord tissue. When loaded with mesenchymal stem cells (MSCs), the scaffold promoted cytoplasmic sequestration of yes-associated protein (YAP), thereby directing MSC fate toward a neurogenic phenotype, accompanied by enhanced expression of stemness markers (NANOG and OCT4) and increased paracrine secretion of neurotrophic factors, including GDNF, NGF, and NT-3. In a rat complete spinal cord transection model, implantation of the MSC-laden scaffold significantly improved BBB locomotor scores and pain thresholds within 4 weeks. Histological analyses further revealed increased MAP2-positive axonal regeneration, enhanced MBP-positive myelination, and reduced GFAP-positive glial scar formation. Collectively, these findings demonstrate a scalable and effective strategy that integrates biomimetic mechanical cues with controlled stem cell fate regulation to promote functional neural regeneration following SCI.