Nanogel-mediated delivery of oncomodulin secreted from regeneration-associated macrophages promotes sensory axon regeneration in the spinal cord

• Published in: Theranostics 2022-01, Vol.12 (13), p.5856-5876
• Main Authors: Kwon, Min Jung, Seo, Yeojin, Cho, Hana, Kim, Hyung Soon, Oh, Young Joo, Genişcan, Simay, Kim, Minjae, Park, Hee Hwan, Joe, Eun-Hye, Kwon, Myung-Hee, Kang, Han Chang, Kim, Byung Gon
• Format: Article
• Language: English
• Subjects: Research Paper
• ISSN: 1838-7640; 1838-7640
• DOI: 10.7150/thno.73386

Preconditioning nerve injury enhances axonal regeneration of dorsal root ganglia (DRG) neurons in part by driving pro-regenerative perineuronal macrophage activation. How these macrophages influence the neuronal capacity of axon regeneration remains elusive. We report that oncomodulin (ONCM) is produced from the regeneration-associated macrophages and strongly influences regeneration of DRG sensory axons. We also attempted to promote sensory axon regeneration by nanogel-mediated delivery of ONCM to DRGs. Methods: In vitro neuron-macrophage interaction model and preconditioning sciatic nerve injury were used to verify the necessity of ONCM in preconditioning injury-induced neurite outgrowth. We developed a nanogel-mediated delivery system in which electrostatic encapsulation of ONCM by a reducible epsilon-poly( L -lysine)-nanogel (REPL-NG) enabled a controlled release of ONCM. Results: Sciatic nerve injury upregulated ONCM in DRG macrophages. ONCM in macrophages was necessary to produce pro-regenerative macrophages in the in vitro model of neuron-macrophage interaction and played an essential role in preconditioning-induced neurite outgrowth. ONCM increased neurite outgrowth in cultured DRG neurons by activating a distinct gene set, particularly neuropeptide-related genes. Increasing extracellularly secreted ONCM in DRGs sufficiently enhanced the capacity of neurite outgrowth. Intraganglionic injection of REPL-NG/ONCM complex allowed sustained ONCM activity in DRG tissue and achieved a remarkable long-range regeneration of dorsal column sensory axons beyond spinal cord lesion. Conclusion: NG-mediated ONCM delivery could be exploited as a therapeutic strategy for promoting sensory axon regeneration following spinal cord injury.