Abstract
Intramuscular expression of functional proteins is a promising strategy for therapeutic purposes. Previously, we developed an intramuscular gene delivery method by combining Pluronic L64 and optimized electropulse, which is among the most efficient methods to date. However, plasmid DNAs (pDNAs) in this method were not compressed, making them unstable and inefficient in vivo. We considered that a proper compression of pDNAs by an appropriate material should facilitate gene expression in this L64-electropulse system. Here, we reported our finding of such a material, Epigallocatechin gallate (EGCG), a natural compound in green teas, which could compress and protect pDNAs and significantly increase intramuscular gene expression in the L64-electropulse system. Meanwhile, we found that polyethylenimine (PEI) could also slightly improve exogenous gene expression in the optimal procedure. By analysing the characteristic differences between EGCG and PEI, we concluded that negatively charged materials with strong affinity to nucleic acids and/or other properties suitable for gene delivery, such as EGCG, are better alternatives than cationic materials (like PEI) for muscle-based gene delivery. The results revealed that a critical principle for material/pDNA complex benefitting intramuscular gene delivery/expression is to keep the complex negatively charged. This proof-of-concept study displays the breakthrough in compressing pDNAs and provides a principle and strategy to develop more efficient intramuscular gene delivery systems for therapeutic applications.
Highlights
It is an attractive strategy to produce therapeutic molecules using myocytes in skeletal muscles through intramuscular delivery of functional genes [1]
Epigallocatechin gallate (EGCG) can inhibit the activity of some nucleases by blocking their active sites [37,38,39], which may further strengthen the protective effect on DNA against enzymatic degradation. In this proof-of-concept study, we investigated if the EGCGcompressed plasmid DNAs (pDNAs) can significantly improve intramuscular gene expression based on the L64-electropulse method
Morphology analysis by AFM showed that both PEI/pDNA (N/P 1⁄4 0.5) and EGCG/pDNA were well compressed to nanoscale with nearly spherical 3D architectures (Fig. 1C and D)
Summary
It is an attractive strategy to produce therapeutic molecules using myocytes in skeletal muscles through intramuscular delivery of functional genes [1]. In this kind of gene therapy trials, naked plasmids have distinct advantages over viral vectors, such as biosafety, simplicity and cost efficiency [2].
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