Reducing neuroinflammation by delivery of IL‐10 encoding lentivirus from multiple‐channel bridges

The spinal cord is unable to regenerate after injury largely due to growth-inhibition by an inflammatory response to the injury that fails to resolve, resulting in secondary damage and cell death. An approach that prevents inhibition by attenuating the inflammatory response and promoting its resolution through the transition of macrophages to anti-inflammatory phenotypes is essential for the creation of a growth permissive microenvironment. Viral gene delivery to induce the expression of anti-inflammatory factors provides the potential to provide localized delivery to alter the host inflammatory response. Initially, we investigated the effect of the biomaterial and viral components of the delivery system to influence the extent of cell infiltration and the phenotype of these cells. Bridge implantation reduces antigen-presenting cell infiltration at day 7, and lentivirus addition to the bridge induces a transient increase in neutrophils in the spinal cord at day 7 and macrophages at day 14. Delivery of a lentivirus encoding IL-10, an anti-inflammatory factor that inhibits immune cell activation and polarizes the macrophage population towards anti-inflammatory phenotypes, reduced neutrophil infiltration at both day 7 and day 28. Though IL-10 lentivirus did not affect macrophages number, it skewed the macrophage population toward an anti-inflammatory M2 phenotype and altered macrophage morphology. Additionally, IL-10 delivery resulted in improved motor function, suggesting reduced secondary damage and increased sparing. Taken together, these results indicate that localized expression of anti-inflammatory factors, such as IL-10, can modulate the inflammatory response following spinal cord injury, and may be a key component of a combinatorial approach that targets the multiple barriers to regeneration and functional recovery.