Enhanced transfection efficiency of human embryonic stem cells by the incorporation of DNA liposomes in extracellular matrix

A Cell-Based Optimised Approach for Rapid and Efficient Gene Editing of Human Pluripotent Stem Cells

Introducing or correcting disease-causing mutations through genome editing in human pluripotent stem cells (hPSCs) followed by tissue-specific differentiation provide sustainable models of multiorgan diseases, such as cystic fibrosis (CF). However, low editing efficiency resulting in extended cell culture periods and the use of specialised equipment for fluorescence activated cell sorting (FACS) make hPSC genome editing still challenging. We aimed to investigate whether a combination of cell cycle synchronisation, single-stranded oligodeoxyribonucleotides, transient selection, manual clonal isolation, and rapid screening can improve the generation of correctly modified hPSCs. Here, we introduced the most common CF mutation, ΔF508, into the CFTR gene, using TALENs into hPSCs, and corrected the W1282X mutation using CRISPR-Cas9, in human-induced PSCs. This relatively simple method achieved up to 10% efficiency without the need for FACS, generating heterozygous and homozygous gene edited hPSCs within 3-6 weeks in order to understand genetic determinants of disease and precision medicine.

LINE-1 Retrotransposition Assays in Embryonic Stem Cells

The ongoing mobilization of active non-long terminal repeat (LTR) retrotransposons continues to impact the genomes of most mammals, including humans and rodents. Non-LTR retrotransposons mobilize using an intermediary RNA and a copy-and-paste mechanism termed retrotransposition. Non-LTR retrotransposons are subdivided into long and short interspersed elements (LINEs and SINEs, respectively), depending on their size and autonomy; while active class 1 LINEs (LINE-1s or L1s) encode the enzymatic machinery required to mobilize in cis, active SINEs use the enzymatic machinery of active LINE-1s to mobilize in trans. The mobilization mechanism used by LINE-1s/SINEs was exploited to develop ingenious plasmid-based retrotransposition assays in cultured cells, which typically exploit a reporter gene that can only be activated after a round of retrotransposition. Retrotransposition assays, in cis or in trans, are instrumental tools to study the biology of mammalian LINE-1s and SINEs. In fact, these and other biochemical/genetic assays were used to uncover that endogenous mammalian LINE-1s/SINEs naturally retrotranspose during early embryonic development. However, embryonic stem cells (ESCs) are typically used as a cellular model in these and other studies interrogating LINE-1/SINE expression/regulation during early embryogenesis. Thus, human and mouse ESCs represent an excellent model to understand how active retrotransposons are regulated and how their activity impacts the germline. Here, we describe robust and quantitative protocols to study human/mouse LINE-1 (in cis) and SINE (in trans) retrotransposition using (human and mice) ESCs. These protocols are designed to study the mobilization of active non-LTR retrotransposons in a cellular physiologically relevant context.

Liposomal Thiostrepton Formulation and Its Effect on Breast Cancer Growth Inhibition

Forkhead box M1 (FOXM1) is known to play a role in breast cancer progression. FOXM1 inhibition becomes one of the strategies in developing the novel cancer therapy. Recently, thiostrepton has been recognized as a potent FOXM1 inhibitor. To improve its potential, we aimed to develop a nanodelivery system for thiostrepton. Here, liposome-encapsulated thiostrepton (TSLP) was developed. Physiochemical properties were characterized by TEM and dynamic light scattering technique. The biological activities were also evaluated, by cellular internalization, MTT assay, spheroid formation assay and RT-PCR. The result showed that the range sizes of TSLP were 152 ± 2 nm, polydispersity index (PdI) of 0.23 ± 0.02 and zeta potential of -20.2 ± 0.1 mV. As expected, TSLP showed a higher potential in reducing FOXM1 levels in MCF-7 cells than free thiostrepton. Additionally, TSLP significantly improved the efficiently and specificity of thiostrepton in reducing cell viability of MCF-7, but not of the fibroblast (HDFn) cells. Interestingly, TSLP had an ability to induce MCF-7 cell death in both 2D monolayer and 3D spheroid culture. In conclusions, TSLP could possibly be one of the potential developments using nano-delivery system to improve abilities and specificity of thiostrepton in breast cancer cell inhibition and death inducing, with decreasing non-specific toxicity.

Molecular mechanism of Forkhead box M1 inhibition by thiostrepton in breast cancer cells

Breast cancer is the most common type of malignancies in women worldwide, and genotoxic chemotherapeutic drugs are effective by causing DNA damage in cancer cells. However, >90% of patients with metastatic cancer are resistant to chemotherapy. The Forkhead box M1 (FOXM1) transcription factor plays a pivotal role in the resistance of breast cancer cells to chemotherapy by promoting DNA damage repair following genotoxic drug treatment. The aim of the present study was to investigate the inhibition of the FOXM1 protein by thiostrepton, a natural antibiotic produced by the Streptomyces species. Experimental studies were designed to examine the effectiveness of thiostrepton in downregulating FOXM1 mRNA expression and activity, leading to senescence and apoptosis of breast cancer cells. The cytotoxicity of thiostrepton in breast cancer was determined using cell viability assay. Additionally, thiostrepton treatment decreased the mRNA expression of cyclin B1 (CCNB1), a downstream target of FOXM1. The present results indicated that thiostrepton inhibited FOXM1 mRNA expression and its effect on CCNB1. Molecular dynamic simulations were performed to study the interactions between FOXM1-DNA and thiostrepton after molecular docking. The results revealed that the possible mechanism underlying the inhibitory effect of thiostrepton on FOXM1 function was by forming a tight complex with the DNA and FOXM1 via its binding domain. Collectively, these results indicated that thiostrepton is a specific and direct inhibitor of the FOXM1 protein in breast cancer. The findings of the present study may lead to the development of novel therapeutic strategies for breast cancer and help overcome resistance to conventional chemotherapeutic drugs.

Improved Transfection Efficiency and Metabolic Activity in Human Embryonic Stem Cell Using Non-Enzymatic Method

Human embryonic stem cells (hESCs) are pluripotent cells widely used in conventional and regenerative medicine due to their ability to self-renew, proliferate and differentiate. Recently, genetic modification of stem cells using genome editing is the most advanced technique for treating hereditary diseases. Nevertheless, the low transfection efficiency of hESCs using enzymatic methods is still limited in in vitro preclinical research. To overcome these limitations, we have developed transfection methods using non-enzymatic treatments on hESCs. In this study, hESCs were transfected following enzymatic (TrypLE and trypsin) and non-enzymatic treatment ethylenediaminetetraacetic acid (EDTA) to increase transfection efficiency. Flow cytometric analysis using an enhanced green fluorescent protein vector showed a significantly increased transfection efficiency of EDTA method compared to standard enzyme method. In addition, the EDTA approach maintained stable cell viability and recovery rate of hESCs after transfection. Also, metabolic activity by using Extracellular Flux Analyzer revealed that EDTA method maintained as similar levels of cell functionality as normal group comparing with enzymatic groups. These results suggest that transfection using EDTA is a more efficient and safe substitute for transfection than the use of standard enzymatic methods.

An improved method for increasing the efficiency of gene transfection and transduction

Transfection and transduction using lentivirus has gained attention in biomedical research. To date, how to reach the maximum transfection and viral transduction efficiency is still challenging. Here we compared the transfection and viral transduction efficiency using commercially available transfection reagents including FuGENE 6, Lipofectamine 2000 and Lipofectamine 3000 in different cell lines and primary cultured cells. Enhanced green fluorescent protein (EGFP) was clearly seen in Eppendorf tubes from harvested cells using Lipofectamine 3000 without using a microscope and UV activation. Strong expression of EGFP was observed in HEK293 cells, mouse primary cortical neurons and human umbilical vein endothelial cells (HUVECs) using confocal microscopy. Western blot showed the strongest EGFP expression using cell lysates from Lipofectamine 3000 transfected HEK293 cells and transduced HUVECs compared with Lipofectamine 2000 or FuGENE 6 reagents. Using Cx43 shRNA lentivirus combined with Lipofectamine 3000 transfection reagent, we can achieve about 90% Cx43 knockdown efficacy in HUVECs. Therefore, our results suggest that a much higher transfection and viral transduction efficiency can be attained by using Lipofectamine 3000 transfection reagent.

Lentiviral Transduction of Rat Schwann Cells and Dorsal Root Ganglia Neurons for In Vitro Myelination Studies

Lentiviral transduction is a gene delivery method that provides numerous advantages over direct transfection and traditional retroviral or adenoviral delivery methods. It facilitates for the transduction of primary cells inherently difficult to transfect, delivers constructs of interest to nondividing as well as dividing cells, and permits the long-term expression of sizable DNA inserts (e.g., <7 kb). The study of peripheral nerve myelination at the molecular level has long benefited from the Schwann cells/dorsal root ganglia (DRG) neurons myelinating co-culture system. As this culture system takes about a month to develop and perform experiments with, lentiviral-delivered constructs can be used to manipulate gene expression in Schwann cells and DRG neurons, primary cells that are otherwise resilient to direct transfection. Here we present our protocol for lentiviral production and purification and subsequent infection of large numbers of Schwann cells and/or DRG neurons for the molecular study of peripheral nerve myelination in vitro.

Adoption of the Q Transcriptional System for Regulating Gene Expression in Stem Cells

The field of mammalian synthetic biology seeks to engineer enabling technologies to create novel approaches for programming cells to probe, perturb, and regulate gene expression with unprecedented precision. To accomplish this, new genetic parts continue to be identified that can be used to build novel genetic circuits to re-engineer cells to perform specific functions. Here, we establish a new transcription-based genetic circuit that combines genes from the quinic acid sensing metabolism of Neorospora crassa and the bacterial Lac repressor system to create a new orthogonal genetic tool to be used in mammalian cells. This work establishes a novel genetic tool, called LacQ, that functions to regulate gene expression in Chinese hamster ovarian (CHO) cells, human embryonic kidney 293 (HEK293) cells, and in mouse embryonic stem (ES) cells.

Functionalization of microparticles with mineral coatings enhances non-viral transfection of primary human cells

Gene delivery to primary human cells is a technology of critical interest to both life science research and therapeutic applications. However, poor efficiencies in gene transfer and undesirable safety profiles remain key limitations in advancing this technology. Here, we describe a materials-based approach whereby application of a bioresorbable mineral coating improves microparticle-based transfection of plasmid DNA lipoplexes in several primary human cell types. In the presence of these mineral-coated microparticles (MCMs), we observed up to 4-fold increases in transfection efficiency with simultaneous reductions in cytotoxicity. We identified mechanisms by which MCMs improve transfection, as well as coating compositions that improve transfection in three-dimensional cell constructs. The approach afforded efficient transfection in primary human fibroblasts as well as mesenchymal and embryonic stem cells for both two- and three-dimensional transfection strategies. This MCM-based transfection is an advancement in gene delivery technology, as it represents a non-viral approach that enables highly efficient, localized transfection and allows for transfection of three-dimensional cell constructs.

Engineered LINE-1 retrotransposition in nondividing human neurons

Half the human genome is made of transposable elements (TEs), whose ongoing activity continues to impact our genome. LINE-1 (or L1) is an autonomous non-LTR retrotransposon in the human genome, comprising 17% of its genomic mass and containing an average of 80-100 active L1s per average genome that provide a source of inter-individual variation. New LINE-1 insertions are thought to accumulate mostly during human embryogenesis. Surprisingly, the activity of L1s can further impact the somatic human brain genome. However, it is currently unknown whether L1 can retrotranspose in other somatic healthy tissues or if L1 mobilization is restricted to neuronal precursor cells (NPCs) in the human brain. Here, we took advantage of an engineered L1 retrotransposition assay to analyze L1 mobilization rates in human mesenchymal (MSCs) and hematopoietic (HSCs) somatic stem cells. Notably, we have observed that L1 expression and engineered retrotransposition is much lower in both MSCs and HSCs when compared to NPCs. Remarkably, we have further demonstrated for the first time that engineered L1s can retrotranspose efficiently in mature nondividing neuronal cells. Thus, these findings suggest that the degree of somatic mosaicism and the impact of L1 retrotransposition in the human brain is likely much higher than previously thought.

Comparison of Different Electroporation Parameters on Transfection Efficiency of Sheep Testicular Cells

OBJECTIVE

Electroporation can be a highly efficient method for introducing the foreign genetic materials into the targeted cells for transient and/or permanent genetic modification. Considering the application of this technique as a very efficient method for drug, oligonucleotide, antibody and plasmid delivery for clinical applications and production of transgenic animals, the present study aimed to optimize the transfection efficiency of sheep testicular cells including spermatogonial stem cells (SSCs) via electroporation.

MATERIALS AND METHODS

This study is an experimental research conducted in Biotechnology Research Center (Avicenna Research Institute, Tehran, Iran) from September 2013 to March 2014. Following isolation and propagation of one-month lamb testicular cells (SSCs and somatic testicular cells including; Sertoli, Leydig, and myoid cells), the effect of different electroporation parameters including total voltages (280, 320, and 350 V), burst durations (10, 8, and 5 milliseconds), burst modes (single or double) and addition of dimethyl sulfoxide (DMSO) were evaluated on transfection efficiency, viability rate and mean fluorescent intensity (MFI) of sheep testicular cells.

RESULTS

The most transfection efficiency was obtained in 320 V/8 milliseconds/single burst group in transduction medium with and without DMSO. There was a significantly inverse correlation between transfection efficiency with application of both following parameters: addition of DMSO and double burst. After transfection, the highest and lowest viability rates of testicular cells were demonstrated in 320 V/8 milliseconds with transduction medium without DMSO and 350 V/5 milliseconds in medium containing DMSO. Ad- dition of DMSO to transduction medium in all groups significantly decreased the viability rate. The comparison of gene expression indicated that Sertoli and SSCs had the most fluorescence intensity in 320 V/double burst/DMSO positive. However, myoid and Leydig cells showed the maximum expression in 320 V/single burst and/or 350 V/double burst/ DMSO positive.

CONCLUSION

We optimized the electroporation method for transfection of sheep testicular cells and recommended the application of 320 V/8 milliseconds/single pulse/DMSO negative for transduction of plasmid vector into these cells. Among testicular cells, the most external gene expression was demonstrated in SSC population.

Influence of Growth Characteristics of Induced Pluripotent Stem Cells on Their Uptake Efficiency for Layer-by-Layer Microcarriers

Induced pluripotent stem cells (iPSCs) have the ability to differentiate into any specialized somatic cell type, which makes them an attractive tool for a wide variety of scientific approaches, including regenerative medicine. However, their pluripotent state and their growth in compact colonies render them difficult to access and, therefore, restrict delivery of specific agents for cell manipulation. Thus, our investigation focus was set on the evaluation of the capability of layer-by-layer (LbL) designed microcarriers to serve as a potential drug delivery system to iPSCs, as they offer several appealing advantages. Most notably, these carriers allow for the transport of active agents in a protected environment and for a rather specific delivery through surface modifications. As we could show, charge and mode of LbL carrier application as well as the size of the iPSC colonies determine the interaction with and the uptake rate by iPSCs. None of the examined conditions had an influence on iPSC colony properties such as colony morphology and size or maintenance of pluripotent properties. An overall interaction rate of LbL carriers with iPSCs of up to 20% was achieved. Those data emphasize the applicability of LbL carriers for stem cell research. Additionally, the potential use of LbL carriers as a promising delivery tool for iPSCs was contrasted to viral particles and liposomes. The identified differences among those delivery tools have substantiated our major conclusion that LbL carrier uptake rate is influenced by characteristic features of the iPSC colonies (most notably colony size) in addition to their surface charges.

Single-Cell-State Culture of Human Pluripotent Stem Cells Increases Transfection Efficiency

Efficient gene transfer into human pluripotent stem cells (hPSCs) holds great promise for regenerative medicine and pharmaceutical development. In the past decade, various methods were developed for gene transfer into hPSCs; however, hPSCs form tightly packed colonies, making gene transfer difficult. In this study, we established a stable culture method of hPSCs at a single-cell state to reduce cell density and investigated gene transfection efficiency followed by gene editing efficiency. hPSCs cultured in a single-cell state were transfected using nonliposomal transfection reagents with plasmid DNA or mRNA encoding enhanced green fluorescent protein. We found that most cells (DNA > 90%; mRNA > 99%) were transfected without the loss of undifferentiated PSC marker expression or pluripotency. Moreover, we demonstrated an efficient gene editing method using transcription activator-like effector nucleases (TALENs) targeting the adenomatous polyposis coli (APC) gene. Our new method may improve hPSC gene transfer techniques, thus facilitating their use for human regenerative medicine.

High-Efficient Transfection of Human Embryonic Stem Cells by Single-Cell Plating and Starvation

Nowadays, the low efficiency of small interfering RNA (siRNA) or plasmid DNA (pDNA) transfection is a critical issue in genetic manipulation of human embryonic stem (hES) cells. Development of an efficient transfection method for delivery of siRNAs and plasmids into hES cells becomes more and more imperative. In this study, we tried to modify the traditional transfection protocol by introducing two crucial processes, single-cell plating and starvation, to increase the transfection efficiency in hES cells. Furthermore, we comparatively examined the transfection efficiency of some commercially available siRNA or pDNA transfection reagents in hES cells. Our results showed that the new developed method markedly enhanced the transfection efficiency without influencing the proliferation and pluripotency of hES cells. Lipofectamine RNAiMAX exhibited much higher siRNA transfection efficiency than the other reagents, and FuGENE HD was identified as the best suitable reagent for efficient pDNA transfection of hES cells among the tested reagents.

DPPA5 Supports Pluripotency and Reprogramming by Regulating NANOG Turnover

Although a specific group of transcription factors such as OCT4, SOX2, and NANOG are known to play essential roles in pluripotent stem cell (PSC) self-renewal, pluripotency, and reprogramming, other factors and the key signaling pathways regulating these important properties are not completely understood. Here, we demonstrate that the PSC marker Developmental Pluripotency Associated 5 (DPPA5) plays an important role in human PSC (hPSC) self-renewal and cell reprogramming in feeder-free conditions. Compared to hPSCs grown on mouse embryonic fibroblasts, cells cultured on feeder-free substrates, such as Matrigel, Laminin-511, Vitronectin, or the synthetic polymer poly[2-(methacryloyloxy) ethyl dimethyl-(3-sulfopropyl) ammonium hydroxide], had significantly higher DPPA5 gene expression and protein levels. Overexpression of DPPA5 in hPSCs increased NANOG protein levels via a post-transcriptional mechanism. Coimmunoprecipitation, protein stability assays, and quantitative RT-PCR, demonstrated that DPPA5 directly interacted, stabilized, and enhanced the function of NANOG in hPSCs. Additionally, DPPA5 increased the reprogramming efficiency of human somatic cells to induced pluripotent stem cells (hiPSCs). Our study provides new insight into the function of DPPA5 and NANOG regulation in hPSCs.

Cationic star copolymers based on β-cyclodextrins for efficient gene delivery to mouse embryonic stem cell colonies

A cationic star copolymer with a β-cyclodextrin core was developed for nonviral gene transfer to mouse embryonic stem cells (mESCs).

A novel formulation based on 2,3-di(tetradecyloxy)propan-1-amine cationic lipid combined with polysorbate 80 for efficient gene delivery to the retina

PURPOSE

The aim of the present study was to evaluate the potential application of a novel formulation based on a synthesized cationic lipid 2,3-di(tetradecyloxy)propan-1-amine, combined with polysorbate 80 to deliver the pCMS-EGFP plasmid into the rat retina.

METHODS

We elaborated lipoplexes by mixing the formulation containing the cationic lipid and the polysorbate 80 with the plasmid at different cationic lipid/DNA ratios (w/w). Resulted lipoplexes were characterized in terms of size, charge, and capacity to condense, protect and release the DNA. In vitro transfection studies were performed in HEK-293 and ARPE-19 cells. Formulations were also tested in vivo by monitoring the expression of the EGFP after intravitreal and subretinal injections in rat eyes.

RESULTS

At 2/1 cationic lipid/DNA mass ratio, the resulted lipoplexes had 200 nm of hydrodynamic diameter; were positive charged, spherical, protected DNA against enzymatic digestion and transfected efficiently HEK-293 and ARPE-19 cultured cells exhibiting lower cytotoxicity than LipofectamineTM 2000. Subretinal administrations transfected mainly photoreceptors and retinal pigment epithelial cells; whereas intravitreal injections produced a more uniform distribution of transfection through the inner part of the retina.

CONCLUSIONS

These results hold great expectations for other gene delivery formulations based on this cationic lipid for retinal gene therapy purposes.

Preparation of cell-culturing glass surfaces that release branched polyethyleneimine triggered by thiol-disulfide exchange

To develop a chemical stimulus-responsive substrate for culturing cells, polyethyleneimine (PEI) having a pyridyl disulfide moiety was attached via disulfide linkages to a glass coverslip modified with a silane coupling agent having a thiol group. The surface modification was confirmed by X-ray photoelectron spectroscopy and zeta potential analysis. The obtained surface exhibited sufficiently high cell adhesiveness. Zeta potential measurements revealed that the PEI derivatives were released from the surface through thiol-disulfide exchange when the modified glass coverslip was immersed in a neutral pH buffer containing cysteine. The cell viability assay demonstrated that this chemical stimulus was substantially nontoxic to 293T cells. Because PEI is a widely used transfection reagent, this functional glass coverslip would be potentially useful as an experimental platform for reverse transfection.

Porous membrane substrates offer better niches to enhance the Wnt signaling and promote human embryonic stem cell growth and differentiation

Human embryonic stem cells (hESCs) require specific niches for adhesion, expansion, and lineage-specific differentiation. In this study, we showed that a membrane substrate offers better tissue niches for hESC attachment, spreading, proliferation, and differentiation. The cell doubling time was shortened from 46.3±5.7 h for hESCs grown on solid substrates to 25.6±2.6 h for those on polyester (PE) membrane substrates with pore size of 0.4 μm. In addition, we observed an increase of approximately five- to ninefold of definitive endoderm marker gene expression in hESCs differentiated on PE or polyethylene terephthalate membrane substrates. Global gene expression analysis revealed upregulated expressions of a number of extracellular matrix and cell adhesion molecules in hESCs grown on membrane substrates. Further, an enhanced nuclear translocation of β-catenin was detected in these cells. These observations suggested the augmentation of Wnt signaling in hESCs grown on membrane substrates. These results also demonstrated that a membrane substrate can offer better physicochemical cues for enhancing in vitro hESC attachment, proliferation, and differentiation.