Culture time-dependent gene expression in isolated primary cultured rat hepatocytes by transfection with the cationic liposomal vector TFL-3

Preparation and evaluation of N-caproyl chitosan nanoparticles surface modified with glycyrrhizin for hepatocyte targeting

BACKGROUND

The development of an efficient targeted drug delivery system into cells is an important subject for the advancement of drug carriers. In this study, a novel hepatocyte-targeted delivery system with glycyrrhizin (GL) surface modification based on N-caproyl chitosan (CCS) has been developed.

METHOD

CCS was synthesized by acylation of amino group of chitosan, and GL was oxidized to be conjugated to the surface of N-caproyl chitosan nanoparticles (CCS-NPs-GL). The synthesized nanoparticles were first characterized for their morphology, particle size, zeta potential, in vitro stability in plasma, tissue distribution, and hepatocyte-targeting uptake in vivo.

RESULTS

The obtained results showed that the spherical and discrete nanoparticles prepared with oxidized GL/CCS ratio of 0.14:1 (w/w) exhibited a positive electrical charge and associated adriamycin quite efficiently (association efficiency: 87.5%). The prepared nanoparticles also possessed dimensional and GL surface-binding stability and slow release property in plasma in vitro. The biodistribution of these particles after intravenous injections in mice revealed accumulating drug concentrations in the liver, spleen, and lungs while decreasing drug concentrations in the heart and kidney. The content of adriamycin-loaded CCS-NPs-GL in the liver was 1.6 times higher than that of non-GL-modified CCS-NPs. Furthermore, in vivo uptake of CCS-NPs-GL by rat hepatocytes showed 2.1 times higher nanoparticle uptake compared with non-GL-modified CCS-NPs, which suggested that CCS-NPs-GL were preferentially distributed in hepatocytes by a ligand-receptor interaction.

CONCLUSION

This article indicated that CCS-NPs-GL was a stable and effective drug delivery vehicle for hepatocyte targeting.

Cationic glycolipids with cyclic and open galactose head groups for the selective targeting of genes to mouse liver

Toward probing an hitherto unexplored structure-activity issue namely, the relative in vitro and in vivo efficacies of cationic glycolipids with cyclic and acyclic sugar heads for targeting of genes to liver, we have designed and synthesized two novel series of cationic glycolipids with cyclic (lipids 1-5) and open d-galactose heads (lipids 6-10) containing varying spacer arm lengths in between the sugar and positively charged nitrogen atoms. Among the cyclic glycolipids, lipid 3 with six methylene units spacer in between the quaternary nitrogen atom and among the glycolipids with the open-sugar heads, lipid 6 with only two methylene units spacer were found to be the most efficacious in targeting genes to cultured HepG2 (human hepatocarcinoma cells) and primary hepatocytes. Findings in the fluorescence resonance energy transfer (FRET) studies revealed biomembrane fusibilities as important physico-chemical parameters behind the varying spacer arm dependencies in the two series. Importantly, both the serum compatible glycolipids 3 &6 were found to be equally efficacious in selectively targeting genes to mouse livers under systemic settings. The significantly reduced efficiencies of the glycolipids 3 &6 in transfecting primary hepatocytes as well as mice pretreated with asialofetuin (the ligands of asialoglycoprotein receptors) support the notion that the cellular uptake of the lipoplexes prepared from both the open and the cyclic sugar-head series is mediated via asialoglycoprotein receptor. In summary, our present findings demonstrate for the first time that cationic glycolipids with cyclic sugar-head require longer spacer arms than their acyclic sugar-head counterparts for efficient gene transfection and both the series hold equal promise for selective gene targeting to liver under systemic settings.

The gene-silencing effect of siRNA in cationic lipoplexes is enhanced by incorporating pDNA in the complex

Efficient delivery is a key issue in translating interference RNA technology into a feasible therapy. The efficiency of carrier systems used for this technology is commonly tested by co-transfection, i.e. simultaneous transfection with an exogenous gene and with the siRNA. Two approaches can be distinguished: (1) with the two transfectants in the same carrier complex (siRNA/pDNA/carrier) and (2) with the two transfectants in different carrier complexes (pDNA/carrier and siRNA/carrier). The process to prepare the nucleic acid(s)-carrier complexes and the transfection procedure may affect the effectiveness of the gene-silencing process. In this study, two preparation methods were compared, namely the co-preparation of an siRNA/pDNA/liposome lipoplex (Method I) and the separate preparation of an siRNA/liposome lipoplex and a pDNA/liposome lipoplex (Method II). siRNA in the lipoplex produced by Method I showed a stronger gene-silencing effect than that in the lipoplexes prepared by Method II. There was no significant difference between the two methods in the amount of siRNA delivered to cells. Cellular entry and intracellular trafficking of siRNA/pDNA/liposome lipoplex is likely to differ from those of the separate lipoplexes. When in Method II non-transcriptional pDNA was included in the complex with siRNA, the gene-silencing effect was significantly enhanced. If and to what extent the experimental design is suitable to quantify RNA interference remains to be demonstrated.

Stimulatory effect of polyethylene glycol (PEG) on gene expression in mouse liver following hydrodynamics-based transfection

BACKGROUND

Rapid intravenous injection of a large volume of plasmid DNA (pDNA), i.e. a transfection procedure based on hydrodynamics, is known to be an efficient and liver-specific method of in vivo gene delivery. However, the gene expression is transient.

METHODS

We investigated the effect of addition of polyethylene glycol (PEG) to a solution of naked pDNA (luciferase) on the expression of the gene in mouse liver following transfection by the hydrodynamics-based technique. In addition, the mechanism leading to the enhancement of the gene expression was studied.

RESULTS

The addition of 1% (w/v) PEG2000 to the pDNA solution enhanced the resulting gene expression in the liver. Increasing the PEG2000 concentration to more than 1 and up to 10% (w/v) rather diminished the gene expression level. By contrast, increasing the molecular weight of PEG to over 2000 up to 10 000 did not affect the level of gene expression. Histopathological and serum-chemistry examinations indicated that hydrostatic or osmotic pressure increased tissue and hepatocellular damage in a PEG-concentration-dependent manner, and resulted in a decrease in gene expression. Quantitative evaluation showed that the enhanced gene expression resulted from stabilization of the pDNA introduced into the hepatocytes and an enhancement of the transport of intact pDNA to the nucleus.

CONCLUSIONS

For most gene therapy applications and gene function studies, sustained expression of the introduced gene(s) is necessary. This simple method to achieve enhanced gene expression in liver may have a great potential for a wide variety of laboratory studies in molecular and cellular biology as well as possibly for future clinical applications in humans.

Increased gene expression by cationic liposomes (TFL-3) in lung metastases following intravenous injection

We recently showed that size, not surface charge, is a major determinant of the in vitro lipofection efficiency of pDNA/TFL-3 complex (lipoplex), even in the presence of serum. In this study, the effect of lipoplex size as a result of interaction with serum proteins on in vitro lipofection and the relationship of this with in vivo lipofection was examined in a murine lung metastasis model. As previously described, the pDNA to lipid ratio (P/L ratio) affected both the size and zeta potential of the lipoplex. In vitro studies also indicated that transgene expression in B16BL6 cells was largely dependent on the size of the lipoplex, both in the absence or presence (50% (v/v)) of serum. An in vivo lipofection experiment showed that predominant gene expression in lungs occurred only in tumor-bearing mice, not in normal mice. Based on the in vitro study, this tumor-related gene expression was not related to lipoplex size in the presence of serum (50% (v/v)), suggesting that the size alteration, as the result of interactions with serum proteins in the blood stream may not play an important role in the case of systemic injections. In addition, the efficient gene expression in tumor-bearing lung was not related to the progression of lung metastases. The area-specific gene expression in tumor-bearing lungs, which was largely dependent on the P/L ratio of the lipoplexes, was observed by fluorescent microscopy. Although the underlying mechanism for the area-specific transgene expression is not clear, it may be related to the interaction of lipoplexes with tumor cells, vascular endothelial cells under angiogenesis and normal cells in the lungs. The possibility that TFL-3 is a useful utility to the targeted delivery of pDNA to lungs and tumor-related lipofection is demonstrated. This result suggests that area-specific gene expression in lung metastases may be achieved by controlling the physicochemical properties of the lipoplex, i.e. the P/L ratio.

Gene Expression in Primary Cultured Mouse Hepatocytes with a Cationic Liposomal Vector, TFL-3: Comparison with Rat Hepatocytes

We recently reported that a cationic liposomal vector, TFL-3, could be used to achieve significant gene expression in primary cultured rat hepatocytes (Nguyen et al., Biol. Pharm. Bull., 26, 880-885 (2003)). A combination of hepatocyte transplantation and hepatocyte-targeted gene transfer represents a potentially important strategy for expanding treatment options for liver disease. A widely applied approach to support cross-species is necessary before human applications can be realized. Therefore, in this study, we examined the utility of TFL-3 in another species of rodent hepatocytes, namely mouse hepatocytes. Gene expression in mouse hepatocytes by TFL-3 was successful and the level was higher than those in rat hepatocytes that we recently reported on. Interestingly, it appears that both the degree and rate of gene expression were dependent on the incubation time prior to lipofection as well as on the density of cells per dish, but these parameters were independent of the amount of pDNA associated with the cells. These significantly suggest that the culture time prior to and following lipofection, which are related to the biological condition of the cells, may be one of major factors that affect gene expression in hepatocytes and non- or less dividing cells.

Cell type-specific gene expression, mediated by TFL-3, a cationic liposomal vector, is controlled by a post-transcription process of delivered plasmid DNA

The issue of whether the TFL-3, a recently developed cationic liposome, achieves efficient gene expression in different mammalian cell lines (NIH/3T3, LLC, A431 and HeLa cells) was examined. The issue of whether gene expression is related to the amount of plasmid DNA (pDNA) delivered in cells or nuclei following transfection was also examined. The cells were transfected for 1h with pDNA/TFL-3 lipoplexes, and the transfection efficiency was determined by means of a luciferase activity assay. The amount of intracellular and intranuclear pDNA following the transfection was also quantitatively determined. Successful transgene expressions in all cell lines we tested were observed under our experimental conditions, suggesting that the TFL-3 represents a suitable nonviral vector system for the successful gene expression in mammalian cells in vitro. The degree and rate of gene expression were dependent on the type of cells used as well as the incubation time after transfection, but these parameters were independent of the amount of gene delivered to cells and nuclei. These results suggest that TFL-3 mediated gene expression is largely controlled by the process of post-transcription of the delivered pDNA, and not by the process of cellular entry of pDNA and cytoplasmic trafficking of pDNA into nuclei, which is dependent on the cell type. Therefore, the results obtained here clearly suggest that the cell type-specific improvement in transcription efficiency of pDNA and translation of the derived mRNA, together with an improved delivery system to enhance the nuclear delivery of pDNA, is necessary to achieve efficient transgene expression in mammalian cells.