Guided neural stem cell differentiation by dynamic loading of 3D printed elastomeric scaffolds

The limited regenerative ability of "permanent" cells is a major barrier to treating conditions like spinal cord injury (SCI) and myocardial infarction (MI). The delivery of stem cells, which can generate various cell types, offer potential for personalized therapy with reduced immunoreaction and recovery time. However, restoring function to these tissues also requires new or replacement cells to align properly. Neurons, for example, must organize and extend parallel axons, mimicking their natural structure for directional signal propagation. Current stem cell differentiation methods lack guidance, resulting in randomly distributed axons and limited repair effectiveness. Advancing methods and materials to guide stem cell differentiation into functional, aligned nerve bundles is crucial for improving SCI treatment outcomes. This study aimed to develop an in vitro system to promote aligned neural differentiation by applying cyclic uniaxial tension to PC-12 stem cells adhered to 3D-printed elastic scaffolds. We created a simple loading device which can apply cyclic and controllable stretching force to a scaffold, which in turn transmits uniaxial tension to cells adhered to the scaffold during their differentiation. An elastomer ink for 3D printing scaffolds was formulated and surface treatment processes were investigated to enhance the cell-scaffold adhesion to support the dynamic loading. It was revealed that a corona discharge treatment while the scaffold is soaked with type I collagen can significantly enhance cell adhesion. A range of strain magnitudes and frequencies were revealed to enhance the differentiation of neural tissue derived PC-12 cells to neuron cells and increase the length of their neurites up to 76%. The combination of 3% maximum strain and 1 Hz loading frequency maximized differentiation and neurite extension. These findings demonstrate that dynamic mechanical stimulation enhances neural differentiation and organization, offering an alternative approach for regenerative therapies targeting SCI and similar conditions.