Gene therapy is a promising strategy for curing certain types of brain diseases. Supplementation of therapeutic proteins such as aromatic amino acid decarboxylase (AADC) or nerve growth factor (NGF) have been reported to be successful examples of such treatments. However, there are safety concerns because these systems are based on virus-based gene vectors. A safe and efficient artificial carrier is thus urgently needed as an alternative. In this study, an mRNA based artificial gene carrier was introduced into the mouse brain via intracerebroventricular administration. As a carrier, a lipid nanoparticle (LNP) composed of environmentally sensitive lipid-like materials called an SS-cleavable proton-activated lipid-like material is used. The apolipoprotein E mediated cellular uptake of the lipid nanoparticles is one of the key features for its superior and homogeneous transfection activity compared to commercially available transfection reagents in both in vitro and in vivo situations. Immunostaining of brain specimens suggested that exogenous proteins can be introduced into neuronal cells as well as astrocytes using the mRNA-based gene carrier. This cannot be achieved using DNA-based artificial gene carriers. The findings suggest that a combination of an mRNA and a lipid based delivery system have great promise as a platform for the treatment of brain disorders.

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A α-helical GALA peptide (WEAALAEALAEALAEHLAEALAEALEALAA) has been found to possess dual functions: a pH-dependent inducer of endosomal escape, and a ligand that targets lung endothelium. In the present study, the flexibility of GALA was improved by modifying the edge with polyethylene glycol linker, to increase lung-targeting activity. We first investigated the uptake of the GALA-modified liposomes in which GALA was directly conjugated to the lipid (Cholesterol: GALA/Chol) or the phospholipid-PEG (GALA/PEG). The liposomes that were modified with GALA/PEG (GALA/PEG-LPs) were taken up at a higher level by human lung endothelial cells (HMVEC-L), in comparison with particles that were modified with GALA/Chol (GALA/Chol-LPs). Small-interfering RNA-encapsulating liposomal-based nanocarriers (multifunctional envelope-type nano device: MEND) that were formulated with a vitamin E-scaffold SS-cleavable pH-activated lipid-like material, namely GALA/PEG-MEND were also modified with GALA/PEG. Gene silencing activity in the lung endothelium was then evaluated against an endothelial marker; CD31. In comparison with the unmodified MEND, GALA/PEG-MEND exhibited a higher silencing activity in the lung. Optimization of GALA/PEG-MEND resulted in silencing activity in the lung with an ED value of 0.21 mg/kg, while non-specific gene silencing in liver was marginal. Collectively, PEGylated GALA is a promising device for use in targeting the lung endothelium.

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