All-in-one nerve guidance: transplanting a gradient scaffold with immobilized Schwann cells for peripheral nerve regeneration

Peripheral nerve injury (PNI), especially those with long-distance transected defects, remains a major clinical challenge due to limited regenerative capacity associated with inadequate endogenous Schwann cell (SC) support. Here, we developed a biomimetic nerve graft with a defined spatial gradient of immobilized SCs to facilitate effective transplantation and axonal guidance, thus enhancing peripheral nerve regeneration. SCs were initially encapsulated within decellularized nerve matrix (DNM) microgels using a customized flow-focusing microfluidic device. The DNM microgels supported good viability, facilitated cellular proliferation, and preserved the repair phenotype of the encapsulated SCs, while maintaining their advantageous paracrine activity conducive to axon extension. Furthermore, these microgels were incorporated into the density-gradient pores of a pre-designed scaffold, resulting in a gradient SC-laden scaffold, designated as MGs@G-scaffold. Notably, the spatially graded SCs within the MGs@G-scaffold created a stable environmental gradient of neurotrophic factors, thereby providing sustained biochemical cues to guide axonal elongation. Finally, when transplanted into a 15-mm rat sciatic nerve defect model, the SC-laden scaffolds exhibited significantly improved axonal regeneration, remyelination, and functional recovery compared with the SC-free scaffolds. Additionally, MGs@G-scaffolds outperformed scaffolds with uniform SC distribution (MGs@H-scaffolds), achieving therapeutic outcomes comparable to autografts. Overall, this study demonstrates that transplanting spatially graded SCs embedded in a tissue-engineered bioactive scaffold offers sustained ongoing support for cells, gradient biochemical signals, and a pro-regenerative microenvironment for nerve regeneration and functional recovery, which holds great promise for long-distance PNI repair.