Influence of Touch-Spun Nanofiber Diameter on Contact Guidance during Peripheral Nerve Repair

Peripheral nerve regeneration across large gaps remains clinically challenging and scaffold design plays a key role in nerve tissue engineering. One strategy to encourage regeneration has utilized nanofibers or conduits to exploit contact guidance within the neural regenerative milieu. Herein, we report the effect of nanofiber topography on two key aspects of regeneration: Schwann cell migration and neurite extension. Substrates possessing distinct diameter distributions (300 ± 40 to 900 ± 70 nm) of highly aligned poly(ε-caprolactone) nanofibers were fabricated by touch-spinning. Cell migratory behavior and contact guidance were then evaluated both at the tissue level using dorsal root ganglion tissue explants and the cellular level using dissociated Schwann cells. Explant studies showed that Schwann cells emigrated significantly farther on fibers than control. However, both Schwann cells and neurites emigrated from the tissue explants directionally along the fibers regardless of their diameter, and the data were characterized by high variation. At the cellular level, dissociated Schwann cells demonstrated biased migration in the direction of fiber alignment and exhibited a significantly higher biased velocity (0.2790 ± 0.0959 μm·min^-1) on 900 ± 70 nm fibers compared to other nanofiber groups and similar to the velocity found during explant emigration on 900 nm fibers. Therefore, aligned, nanofibrous scaffolds of larger diameters (900 ± 70 nm) may be promising materials to enhance various aspects of nerve regeneration via contact guidance alone. While cells track along with the fibers, this contact guidance is bidirectional along the fiber, moving in the plane of alignment. Therefore, the next critical step to direct regeneration is to uncover haptotactic cues that enhance directed migration.