Nucleic acid delivery: roles in biogerontological interventions

Prolongation of longevity is a history-long desire of humans. Driven by the genetic contribution to longevity and the remarkable plasticity of healthy lifespan as demonstrated in animal models, arduous efforts have been directed to aging and longevity research over the years. Today, our understanding of lifespan determination is much greater than it was in the past, but administrable interventions for longevity enhancement are still virtually absent. The aim of this article is to highlight the technical gap between basic biogerontological research and intervention development, and to explore the importance of nucleic acid (NA) delivery technologies in bridging the gap. It is hoped that this article can engender more awareness of the roles of NA delivery technologies in biogerontological interventions, particularly NA therapy.

Subcellular trafficking and transfection efficacy of polyethylenimine-polyethylene glycol polyplex nanoparticles with a ligand to melanocortin receptor-1

We have synthesized and investigated properties of new PEI-PEG-based polyplexes containing MC1SP-peptide, a ligand specific for melanocortin receptor-1 (targeted polyplexes), and control polyplexes without this ligand peptide (non-targeted polyplexes). The targeted polyplexes demonstrated receptor-mediated transfection of Cloudman S91 (clone M-3) murine melanoma cells that was more efficient than with the non-targeted ones. Transfection with the targeted polyplexes was inhibited by chlorpromazine, an inhibitor of the clathrin-mediated endocytosis pathway, and, to a lesser extent, by filipin III or nystatin, inhibitors of the lipid-raft endocytosis pathway, whereas transfection with the non-targeted polyplexes was inhibited mainly by nystatin or filipin III. The targeted polyplexes caused significantly higher in vivo transfection of melanoma tumor cells after intratumoral administration compared to the non-targeted control. The targeted polyplexes carrying the HSVtk gene, after ganciclovir administration, more efficiently inhibited melanoma tumor growth and prolonged the lifespan of DBA/2 tumor-bearing mice compared to the non-targeted ones. Packed targeted polyplexes appeared and accumulated in the melanoma cells 6h earlier than the non-targeted ones. The targeted polyplexes enter into the nuclei of the melanoma cells more rapidly than the non-targeted control, and this difference may also be attributed to processes of receptor-mediated endocytosis. We believe that these data may be useful for the optimization of polyplex systems.

A rapid and convenient method to enhance transgenic expression in target cells

Gene therapy provides a novel strategy and a new hope for patients with cancer. Unfortunately, the specifics of the delivery systems or the promoters have not achieved the specified efficacy so far, and the perfection of either system will be extremely difficult. In this study, we introduce a simple concept that a combination of a partially specific delivery system and a partially specific promoter activity may achieve a more specific effect on transgenic expression in target cells. The first section describes tumor-related transcription factors that were assayed in tumors or rapidly proliferating cells to determine their activities. The activities of nuclear factor (NF)-κB, CREB, and HIF-1 were higher, and three copies of each response element were used to construct a transcription factor-based synthetic promoter (TSP). The results showed that the expression of the TSP was active and partially specific to cell types. As described in the second section, the multifunctional peptide RGD-4C-HA was designed to absorb polyethyleneimine (PEI) molecules, and this complex was targeted to integrin αvβ3 on B16F10 cells. The results indicated that RGD-4C-HA could associate with PEI to mediate specific targeting in vitro. Finally, the combination of the PEI-peptide complex and TSP could enhance the specifically transgenic expression in B16F10 cells. This strategy has been proven to work in vitro and might potentially be used for specific gene therapy in vivo.

PLGA Nanoparticles for Ultrasound-Mediated Gene Delivery to Solid Tumors

This paper focuses on novel approaches in the field of nanotechnology-based carriers utilizing ultrasound stimuli as a means to spatially target gene delivery in vivo, using nanoparticles made with either poly(lactic-co-glycolic acid) (PLGA) or other polymers. We specifically discuss the potential for gene delivery by particles that are echogenic (amenable to destruction by ultrasound) composed either of polymers (PLGA, polystyrene) or other contrast agent materials (Optison, SonoVue microbubbles). The use of ultrasound is an efficient tool to further enhance gene delivery by PLGA or other echogenic particles in vivo. Echogenic PLGA nanoparticles are an attractive strategy for ultrasound-mediated gene delivery since this polymer is currently approved by the US Food and Drug Administration for drug delivery and diagnostics in cancer, cardiovascular disease, and also other applications such as vaccines and tissue engineering. This paper will review recent successes and the potential of applying PLGA nanoparticles for gene delivery, which include (a) echogenic PLGA used with ultrasound to enhance local gene delivery in tumors or muscle and (b) PLGA nanoparticles currently under development, which could benefit in the future from ultrasound-enhanced tumor targeted gene delivery.

Nucleic acid therapy for lifespan prolongation: present and future

Lifespan prolongation is a common desire of the human race. With advances in biotechnology, the mechanism of aging has been gradually unraveled, laying the theoretical basis of nucleic acid therapy for lifespan prolongation. Regretfully, clinically applicable interventions do not exist without the efforts of converting theory into action, and it is the latter that has been far from adequately addressed at the moment. This was demonstrated by a database search on PubMed and Web of Science, from which only seven studies published between 2000 and 2010 were found to directly touch on the development of nucleic acid therapy for anti-aging and/or longevity enhancing purposes. In light of this, the objective of this article is to overview the current understanding of the intimate association between genes and longevity, and to bring the prospect of nucleic acid therapy for lifespan prolongation to light.

Cyclodextrin-PEI-Tat Polymer as a Vector for Plasmid DNA Delivery to Placenta Mesenchymal Stem Cells

This study aims to modify a cyclodextrin-PEI-based polymer, PEI-β-CyD, with the TAT peptide for plasmid DNA delivery to placenta mesenchymal stem cells (PMSCs). By using the disulfide exchange between the SPDP-activated PEI-β-CyD and TAT peptide, the TAT-PEI-β-CyD polymer was fabricated and the success of this was confirmed by the presence of characteristic peaks for PEI (at δ 2.8-3.2 ppm), CyD (at δ 5.2, 3.8-4.0 and 3.4-3.6 ppm) and TAT (at δ 1.6-1.9 and 6.8-7.2 ppm) in the (1)H NMR spectrum of TAT-PEI-β-CyD. The polymer-plasmid-DNA polyplex could condense DNA at an N/P ratio of 7.0-8.0, and form nanoparticles with the size of 150.6±5.6 nm at its optimal N/P ratio (20/1). By examining the transfection efficiency and cytotoxicity of TAT-PEI-β-CyD, conjugation of the TAT peptide onto PEI-β-CyD was demonstrated to improve the transfection efficiency of PEI-β-CyD in PMSCs after 48 and 96 hours of post-transfection incubation. The viability of PEI-β-CyD-treated PMSCs was shown to be over 80% after 5 h of treatment and 24 h of post-treatment incubation. In summary, this study showed that the TAT-PEI-β-CyD polymer as a vector for plasmid DNA delivery to PMSCs and other cells warrants further investigations. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s12668-011-0010-9) contains supplementary material, which is available to authorized users.