Mineral Coated Micropaarticles Delivering Chondroitinase ABC mRNA Improves Motor Function After Spinal Cord Injury in Rats

INTRODUCTION: Currently, there are no treatments to help regain a significant amount of the function that is lost after spinal cord injury (SCI). A primary reason for the lack in functional recovery is the glial scar, which forms after SCI and inhibits axonal regeneration. Chondroitinase ABC (ChABC), a bacterial enzyme, digests one of the main axonal inhibitors in the glial scar, chondroitin sulfate proteoglycans (CSPGs), and results in axonal regeneration and functional recovery. However, ChABC is not thermally stable and quickly becomes inactive at body temperature. Recently, messenger RNA (mRNA) delivery has emerged as an attractive strategy for non-virally producing proteins in vivo with higher activity than recombinant proteins and a more desirable safety profile than viral gene delivery. METHODS: ChABC mRNA synthesis was designed in Benchling Molecular Biology Suite and ordered as-synthesized plasmid (Genscript). Mineral coatings were grown on hydroxyapatite microparticles and lipoplexes with mRNA were bound to the coatings. Rat spinal cords were contused at the T10 level and the glial scar was allowed to form. Seven days post-injury MCMs with ChABC mRNA were injected into the epicenter of the injury. Rat Hindlimb function was assessed for seven weeks before the rats were harvested. Lastly, immunohistochemistry was used to assess CSPG digestion and axonal sprouting. RESULTS: MCMs delivering ChABC mRNA forced local overexpression of ChABC and significantly digested CSPGs after SCI, resulting in axonal sprouting and a significant improvement in hindlimb function. CONCLUSIONS: MCMs efficiently delivered ChABC mRNA to digest CSPGs in the glial scar after SCI.