In vivo gene transfer using pDNA/chitosan/chondroitin sulfate ternary complexes: Influence of chondroitin sulfate on the stability of freeze-dried complexes and transgene expression in vivo

Background: Chitosan has been investigated as a promising nonviral vector. However, several problems still remain, such as a relatively low transfection efficiency and instability under physiological conditions. We previously demonstrated that a chondroitin sulfate (CS) coating enhanced the transfection efficiency and physicochemical stability of plasmid DNA (pDNA)/chitosan complexes in vitro. In the present study, the effects of coating pDNA/chitosan complexes with CS on the stability in freeze-dry rehydration processes and gene expression in vivo were investigated. Methods: Freeze-drying storage at -20°C, 4°C, or room temperature, freezing storage at -20°C, or liquid storage at 4°C or room temperature, were examined for preservation conditions of pDNA/chitosan/CS ternary complexes by a gel retardation assay, measurements of sizes and zeta potentials, and a luciferase assay. Moreover, to determine the transfection efficiency of the ternary complexes in vivo, suicide gene therapy was carried out in Huh-7-implanted mice using herpes simplex virus thymidine kinase coding pDNA and ganciclovir. Results: The freeze-dried pDNA/chitosan/CS ternary complexes showed sufficient cell transfection ability in vitro and in vivo. In addition, ternary complexes were associated with a significant suppression of tumor growth and a histopathologically high anti-tumor effect by intratumoral injection to tumor-bearing mice. Conclusions: The CS coating enhanced the preservation stability of the pDNA/chitosan complexes after freeze-drying-rehydration and their transgene expression in vivo.