In vivo targeted gene delivery to peripheral neurons mediated by neurotropic poly(ethylene imine)-based nanoparticles

A major challenge in neuronal gene therapy is to achieve safe, efficient, and minimally invasive transgene delivery to neurons. In this study, we report the use of a nonviral neurotropic poly(ethylene imine)-based nanoparticle that is capable of mediating neuron-specific transfection upon a subcutaneous injection. Nanoparticles were targeted to peripheral neurons by using the nontoxic carboxylic fragment of tetanus toxin (HC), which, besides being neurotropic, is capable of being retrogradely transported from neuron terminals to the cell bodies. Nontargeted particles and naked plasmid DNA were used as control. Five days after treatment by subcutaneous injection in the footpad of Wistar rats, it was observed that 56% and 64% of L4 and L5 dorsal root ganglia neurons, respectively, were expressing the reporter protein. The delivery mediated by HC-functionalized nanoparticles spatially limited the transgene expression, in comparison with the controls. Histological examination revealed no significant adverse effects in the use of the proposed delivery system. These findings demonstrate the feasibility and safety of the developed neurotropic nanoparticles for the minimally invasive delivery of genes to the peripheral nervous system, opening new avenues for the application of gene therapy strategies in the treatment of peripheral neuropathies.We acknowledge Dr Teresa Summavielle (i3S – Instituto de Investigação e Inovação em Saúde/IBMC – Instituto de Bio­logia Molecular e Celular) and Dr Meriem Lamghari (i3S – Instituto de Investigação e Inovação em Saúde/INEB – Instituto de Engenharia Biomédica,) for their precious help regarding the in vivo study design and optimization; Dr Fani Neto, Dr António Avelino, and Dr Sara Adães (FMUP – Faculdade de Medicina da Universidade do Porto) for their help in tissue isolation; and Dr Rui Fernandes for the help with TEM analy­sis. This work was financed by FEDER – Fundo Europeu de Desenvolvimento Regional funds through the COMPETE 2020 – Operational Programme for Competitiveness and Internationalisation (POCI), Portugal 2020, and by Portu­guese funds through Fundação para a Ciência e a Tecnologia (FCT)/Ministério da Ciência, Tecnologia e Inovação in the framework of the project “Institute for Research and Innova­tion in Health Sciences” (POCI-01-0145-FEDER-007274). Cátia DF Lopes acknowledges FCT for her PhD scholarship (SFRH/BD/77933/2011)