Hydrogel-Assisted Antisense LNA Gapmer Delivery for In Situ Gene Silencing in Spinal Cord Injury

After spinal cord injury (SCI), nerve regeneration is severely hampered due to the establishment of a highly inhibitory microenvironment at the injury site, through the contribution of multiple factors. The potential of antisense oligonucleotides (AONs) to modify gene expression at different levels, allowing the regulation of cell survival and cell function, together with the availability of chemically modified nucleic acids with favorable biopharmaceutical properties, make AONs an attractive tool for novel SCI therapy developments. In this work, we explored the potential of locked nucleic acid (LNA)-modified AON gapmers in combination with a fibrin hydrogel bridging material to induce gene silencing in situ at a SCI lesion site. LNA gapmers were effectively developed against two promising gene targets aiming at enhancing axonal regeneration—RhoA and GSK3ß. The fibrin-matrix-assisted AON delivery system mediated potent RNA knockdown in vitro in a dorsal root ganglion explant culture system and in vivo at a SCI lesion site, achieving around 75% downregulation 5 days after hydrogel injection. Our results show that local implantation of a AON-gapmer-loaded hydrogel matrix mediated efficient gene silencing in the lesioned spinal cord and is an innovative platform that can potentially combine gene regulation with regenerative permissive substrates aiming at SCI therapeutics and nerve regeneration. This work was supported by Fundação para a Ciência e a Tecnologia ( FCT , Portugal) in the framework of the Harvard-Portugal Medical School Program ( HMSP-ICT/0020/2010 ); Project NORTE-01-0145-FEDER-000008 , supported by the Norte Portugal Regional Operational Programme (NORTE 2020) , under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund (ERDF) ; Fundo Europeu de Desenvolvimento Regional funds through COMPETE 2020 - Operational Program for Competitiveness and Internationalization (POCI) , Portugal 2020; by Portuguese funds through FCT/Ministério da Ciência, Tecnologia e Ensino Superior in the framework of the project “Institute for Research and Innovation in Health Sciences” ( POCI-01-0145-FEDER-007274 ); Marie Curie Actions of the European Community’s 7th Framework Program ( PIEF-GA-2011-300485 to P.M.D.M.); Santa Casa da Misericordia de Lisboa – Prémio Neurociências Mello e Castro , and FCT fellowship SFRH/BPD/108738/2015 (to P.M.D.M). Funding for open access charge: Project NORTE-01-0145-FEDER-000012 , financed by Norte Portugal Regional Operational Programme (NORTE 2020) , under the PORTUGAL 2020 Partnership Agreement, through the ERDF . We would like to acknowledge the support from Paula Magalhães and Tânia Meireles from the i3S Cell Culture and Genotyping Core Facility in real-time PCR experiments.