A functionalized self-assembling peptide containing E7 and YIGSR sequences enhances neuronal differentiation of spermatogonial stem cells on aligned PCL fibers for spinal cord injury repair

Background: Spinal cord injury (SCI) induces neuronal death and disrupts the nerve fiber bundles, which leads to partial or complete sensorimotor function loss of the limbs. Transplantation of exogenous neurons derived from stem cells to the lesion site becomes a new neurorestorative strategy for SCI treatment. Spermatogonial stem cells (SSCs) can attain pluripotency features by converting to embryonic stem-like cells in vitro. However, differentiating SSCs into lineage-specific neurons is quite difficult and low efficiency. Methods: Immunofluorescence, immunohistochemistry, Western blotting, whole-cell patch clamp, and behavioral tests were performed to verify that self-assembled hydrogels could improve the directional differentiation efficiency of SSCs and the feasibility of SSC-derived neurons in the treatment of spinal cord injury. Results: We developed a novel self-assembled peptide Nap-FFGEPLQLKMCDPGYIGSR (Nap-E7-YIGSR) coated with aligned electrospun PCL fibers to enhance neuronal differentiation of SSCs. The Nap-E7-YIGSR peptide could evenly self-assemble on the surface of PCL fibers, enhanced the materials's hydrophilicity, and improved the SSC affinity of PCL fibers through the stem cell adhesion peptide sequence EPLQLKM domain. In addition, Nap-E7-YIGSR could effectively induce SSC neuron differentiation by activating the integrin β1/GSK3β/β-catenin signaling pathway. Moreover, implanting the induced neurons derived from SSCs into SCI lesion sites in rats resulted in the formation of new relay circuits, myelination, and synapse formation. Furthermore, SSC-derived neurons could survive and function in the spinal cord injury microenvironment, boosting the recovery of locomotion. Conclusion: The combination of the multifunctional peptide and aligned fibers can potentially trigger SSC differentiation to neurons, facilitating neuronal replacement therapy and promoting functional recovery after SCI.