Gene Therapy: A Lipofection Approach for Gene Transfer into Primary Endothelial Cells

Cellular transfection using rapid decrease in hydrostatic pressure

Of all methods exercised in modern molecular biology, modification of cellular properties through the introduction or removal of nucleic acids is one of the most fundamental. As such, several methods have arisen to promote this process; these include the condensation of nucleic acids with calcium, polyethylenimine or modified lipids, electroporation, viral production, biolistics, and microinjection. An ideal transfection method would be (1) low cost, (2) exhibit high levels of biological safety, (3) offer improved efficacy over existing methods, (4) lack requirements for ongoing consumables, (5) work efficiently at any scale, (6) work efficiently on cells that are difficult to transfect by other methods, and (7) be capable of utilizing the widest array of existing genetic resources to facilitate its utility in research, biotechnical and clinical settings. To address such issues, we describe here Pressure-jump-poration (PJP), a method using rapid depressurization to transfect even difficult to modify primary cell types such as embryonic stem cells. The results demonstrate that PJP can be used to introduce an array of genetic modifiers in a safe, sterile manner. Finally, PJP-induced transfection in primary versus transformed cells reveals a surprising dichotomy between these classes which may provide further insight into the process of cellular transformation.

Transfection types, methods and strategies: a technical review

Transfection is a modern and powerful method used to insert foreign nucleic acids into eukaryotic cells. The ability to modify host cells’ genetic content enables the broad application of this process in studying normal cellular processes, disease molecular mechanism and gene therapeutic effect. In this review, we summarized and compared the findings from various reported literature on the characteristics, strengths, and limitations of various transfection methods, type of transfected nucleic acids, transfection controls and approaches to assess transfection efficiency. With the vast choices of approaches available, we hope that this review will help researchers, especially those new to the field, in their decision making over the transfection protocol or strategy appropriate for their experimental aims.

A Comprehensive Review on Intracellular Delivery

Intracellular delivery is considered an indispensable process for various studies, ranging from medical applications (cell-based therapy) to fundamental (genome-editing) and industrial (biomanufacture) approaches. Conventional macroscale delivery systems critically suffer from such issues as low cell viability, cytotoxicity, and inconsistent material delivery, which have opened up an interest in the development of more efficient intracellular delivery systems. In line with the advances in microfluidics and nanotechnology, intracellular delivery based on micro- and nanoengineered platforms has progressed rapidly and held great promises owing to their unique features. These approaches have been advanced to introduce a smorgasbord of diverse cargoes into various cell types with the maximum efficiency and the highest precision. This review differentiates macro-, micro-, and nanoengineered approaches for intracellular delivery. The macroengineered delivery platforms are first summarized and then each method is categorized based on whether it employs a carrier- or membrane-disruption-mediated mechanism to load cargoes inside the cells. Second, particular emphasis is placed on the micro- and nanoengineered advances in the delivery of biomolecules inside the cells. Furthermore, the applications and challenges of the established and emerging delivery approaches are summarized. The topic is concluded by evaluating the future perspective of intracellular delivery toward the micro- and nanoengineered approaches.

Lipofection-Mediated Introduction of CRISPR/Cas9 System into Porcine Oocytes and Embryos

Simple Summary

Liposome-mediated gene transfer has become an alternative method for establishing a gene targeting framework, and the production of mutant animals may be feasible even in laboratories without specialized equipment. However, whether blastocyst genome editing can be performed by treatment with lipofection reagent, guide RNA, and Cas9, without performing electroporation or microinjection, remains unclear. In this study, we demonstrated that lipofection treatment successfully induced mutation into zygotes during in vitro fertilization and in embryos at the 2- and 4-cell stages. Although liposome-mediated gene editing is a feasible system for use with zona-pellucida-free oocytes/embryos, several challenges must be overcome.

Abstract

Liposome-mediated gene transfer has become an alternative method for establishing a gene targeting framework, and the production of mutant animals may be feasible even in laboratories without specialized equipment. However, how this system functions in mammalian oocytes and embryos remains unclear. The present study was conducted to clarify whether blastocyst genome editing can be performed by treatment with lipofection reagent, guide RNA, and Cas9 for 5 h without using electroporation or microinjection. A mosaic mutation was observed in blastocysts derived from zona pellucida (ZP)-free oocytes following lipofection treatment, regardless of the target genes. When lipofection treatment was performed after in vitro fertilization (IVF), no significant differences in the mutation rates or mutation efficiency were found between blastocysts derived from embryos treated at 24 and 29 h from the start of IVF. Only blastocysts from embryos exposed to lipofection treatment at 29 h after IVF contained biallelic mutant. Furthermore, there were no significant differences in the mutation rates or mutation efficiency between blastocysts derived from embryos at the 2- and 4-cell stages. This suggests that lipofection-mediated gene editing can be performed in ZP-free oocytes and ZP-free embryos; however, other factors affecting the system efficiency should be further investigated.

Photothermal-assisted surface-mediated gene delivery for enhancing transfection efficiency

The development of gene therapy puts forward the requirements for efficient delivery of genetic information into diverse cells. However, in some cases of transfection, especially those for transfecting some primary cells and for delivering large size plasmid DNA (pDNA), the existing conventional transfection methods show poor efficiency. How to further improve transfection efficiency in these hard-to-achieve issues remains a crucial challenge. Here, we report a photothermal-assisted surface-mediated gene delivery based on a polydopamine-polyethylenimine (PDA-PEI) surface. The PDA-PEI surface was prepared through PEI-accelerated dopamine polymerization, which showed efficiency in the immobilization of PEI/pDNA polyplexes and remarkable photothermal properties. Upon IR irradiation, we observed improved transfection efficiencies of two important hard-to-achieve transfection issues, namely the transfection of primary endothelial cells, which are kinds of typical hard-to-transfect cells, and the transfection of cells with large-size pDNA. We demonstrate that the increases of transfection efficiency were due to the hyperthermia-induced pDNA release, the local cell membrane disturbance, and the polyplex internalization. This work highlights the importance of local immobilization and release of pDNA to gene deliveries, showing great potential applications in medical devices in the field of gene therapy.

Assessment of Different Transfection Parameters in Efficiency Optimization

Achieving optimal transfection efficiency is the most critical step in overcoming the primary obstacle to success in nonviral-mediated gene therapy. Several transfection parameters were being examined including the effects of different types of transfection media, glucose concentration, reporter DNA concentration, and incubation time in lipotransfectant. Efficiency of transfection obtained was highest for Opti-MEM I (29 ± 2.28%; p = 0.001) followed by M199 (24 ± 1.54%; p = 0.009), both of which performed significantly better than DMEM (14 ± 0.28%) as a transfection medium. The rate of transfection was affected by glucose levels in only DMEM with higher efficiency achieved using low glucose containing DMEM (17 ± 0.38%) than its counterpart. Furthermore, transfection rate and cell viability were severely hampered by lengthened exposure to transfection complexes, leading to an overall mean efficiency of 5 ± 0.87%. However, doubling the DNA content in the transfection mixture did not significantly change the mean rate of transfection in M199 medium (24 ± 1.54% to 27 ± 1.54%; p = 0.273). The overall range of mean efficiency acquired with our protocol under different transfection conditions was between 14% and 29%. Hopefully results from this study will further potential success in nonviral-mediated gene transfer.

Gene delivery to pancreatic exocrine cells in vivo and in vitro

BACKGROUND

Effective gene transfer to the pancreas or to pancreatic cells has remained elusive although it is essential for studies of genetic lineage tracing and modulation of gene expression. Different transduction methods and viral vectors were tested in vitro and in vivo, in rat and mouse pancreas.

RESULTS

For in vitro transfection/transduction of rat exocrine cells lipofection reagents, adenoviral vectors, and Mokola- and VSV-G pseudotyped lentiviral vectors were used. For in vivo transduction of mouse and rat pancreas adenoviral vectors and VSV-G lentiviral vectors were injected into the parenchymal tissue. Both lipofection of rat exocrine cell cultures and transduction with Mokola pseudotyped lentiviral vectors were inefficient and resulted in less than 4% EGFP expressing cells. Adenoviral transduction was highly efficient but its usefulness for gene delivery to rat exocrine cells in vitro was hampered by a drastic increase in cell death. In vitro transduction of rat exocrine cells was most optimal with VSV-G pseudotyped lentiviral vectors, with stable transgene expression, no significant effect on cell survival and about 40% transduced cells. In vivo, pancreatic cells could not be transduced by intra-parenchymal administration of lentiviral vectors in mouse and rat pancreas. However, a high efficiency could be obtained by adenoviral vectors, resulting in transient transduction of mainly exocrine acinar cells. Injection in immune-deficient animals diminished leukocyte infiltration and prolonged transgene expression.

CONCLUSIONS

In summary, our study remarkably demonstrates that transduction of pancreatic exocrine cells requires lentiviral vectors in vitro but adenoviral vectors in vivo.

Microporation is a valuable transfection method for gene expression in human adipose tissue-derived stem cells

Stem cells are a promising resource for gene therapy. Adipose tissue-derived stem cells (ADSCs) offer advantages because of their abundance and ease of isolation. However, it is difficult to transduce genes into ADSCs by common transfection methods, especially nonviral methods. We report here the use of a new electroporation method, termed "microporation," to transduce plasmids into human ADSCs (hADSCs). We determined optimal conditions that led to efficient transfection of >76.1% of the microporated hADSCs with only minimal cell damage or cytotoxicity. We demonstrated the expression of both enhanced green fluorescent protein (EGFP) and luciferase from different promoters in microporated hADSCs. More important, the microporated hADSCs retained their multipotency and reporter gene expression was maintained for >2 weeks in vitro and in vivo. We further showed that a Tet-ON-inducible gene expression system could be microporated into hADSCs and that this system was functional following transplantation of the microporated cells into nude mice. Taken together, our data demonstrate that microporation allows a highly efficient transfection of hADSCs, without impairing their stem cell properties.

Nucleofection is an efficient nonviral transfection technique for human bone marrow-derived mesenchymal stem cells

Viral-based techniques are the most efficient systems to deliver DNA into stem cells because they show high gene transduction and transgene expression in many cellular models. However, the use of viral vectors has several disadvantages mainly involving safety risks. Conversely, nonviral methods are rather inefficient for most primary cells. The Nucleofector technology, a new nonviral electroporation-based gene transfer technique, has proved to be an efficient tool for transfecting hard-to-transfect cell lines and primary cells. However, little is known about the capacity of this technique to transfect adult stem cells. In this study, we applied the Nucleofector technology to engineer human bone marrow- derived mesenchymal stem cells (hMSCs). Using a green fluorescent protein reporter vector, we demonstrated a high transgene expression level using U-23 and C-17 pulsing programs: 73.7%+/-2.9% and 42.5%+/-3.4%, respectively. Cell recoveries and viabilities were 38.7%+/-2.9%, 44.5%+/-3.9% and 91.4%+/-1.3%, 94.31%+/-0.9% for U-23 and C-17, respectively. Overall, the transfection efficiencies were 27.4%+/-2.9% (U-23) and 16.6%+/-1.4% (C-17) compared with 3.6%+/-2.4% and 5.4%+/-3.4% of other nonviral transfection systems, such as FUGENE6 and DOTAP, respectively (p<.005 for all comparisons). Nucleofection did not affect the immunophenotype of hM-SCs, their normal differentiation potential, or ability to inhibit T-cell alloreactivity. Moreover, the interleukin-12 gene could be successfully transfected into hMSCs, and the immunomodulatory cytokine was produced in great amount for at least 3 weeks without impairment of its biological activity. In conclusion, nucleofection is an efficient nonviral transfection technique for hMSCs, which then may be used as cellular vehicles for the delivery of biological agents.

High throughput easy microinjection with a single-cell manipulation supporting robot

A single-cell manipulation supporting robot (SMSR) has been developed for the high throughput and easy microinjection. Its concept is to let an experimenter concentrate his/her attention only on the microinjection by facilitating other associated works. SMSR was applied to the microinjection into rice protoplasts and mouse embryonic stem (ES) cells. The microinjection into these cells is exceptionally difficult than usual animal cells such as fibroblasts. In the case of rice protoplast, for example, non-stop microinjection into 100 cells could be done within 1h that was 17-times faster than that of the robot-less work. The success rate was 7-8% that was same level obtained by the robot-less work. The present results indicate that SMSR is a useful machine for the microinjection of specific genes and proteins in living cells to analyze their respective functions, which is an urgent and important subject in the post-genome era.

Reactive oxygen and nitrogen species differentially regulate Toll-like receptor 4-mediated activation of NF-kappa B and interleukin-8 expression

Toll-like receptor 4 (TLR4) has been identified as a transmembrane protein involved in the host innate immune response to gram-negative bacterial lipopolysaccharide (LPS). Upon activation by LPS recognition, the TIR domain of TLR4 signals through MyD88 to activate the nuclear factor kappa B (NF-kappa B) pathway, a critical regulator of many proinflammatory genes, including interleukin-8 (IL-8). Emerging evidence suggests that reactive oxygen species (ROS) can contribute to diverse signaling pathways, including the LPS-induced cascade. In the present study we investigated the role of ROS in TLR-mediated signaling. Purified Escherichia coli LPS, a highly specific TLR4 agonist, elicited an oxidative burst in the monocyte-like cell line THP-1 in a time- and dose-dependent manner. This oxidative burst was shown to be dependent on the presence of TLR4 through transfection studies in HEK cells, which do not normally express this protein, and with bone marrow-derived macrophages from C3H/HeJ mice, which express a mutated TLR4 protein. LPS-stimulated IL-8 expression could be blocked by the antioxidants N-acetyl-L-cysteine and dimethyl sulfoxide at both the protein and mRNA levels. These antioxidants also blocked LPS-induced IL-8 promoter transactivation as well as the nuclear translocation of NF-kappa B. These data provide evidence that ROS regulate immune signaling through TLR4 via their effects on NF-kappa B activation.