Small interfering RNA (siRNA) delivery into murine bone marrow-derived dendritic cells by electroporation

Development of Lipid Nanoparticles for the Delivery of Macromolecules Based on the Molecular Design of pH-Sensitive Cationic Lipids

Considerable efforts have been made on the development of lipid nanoparticles (LNPs) for delivering of nucleic acids in LNP-based medicines, including a first-ever short interfering RNA (siRNA) medicine, Onpattro, and the mRNA vaccines against the coronavirus disease 2019 (COVID-19), which have been approved and are currently in use worldwide. The successful rational design of ionizable cationic lipids was a major breakthrough that dramatically increased delivery efficiency in this field. The LNPs would be expected to be useful as a platform technology for the delivery of various therapeutic modalities for genome editing and even for undiscovered therapeutic mechanisms. In this review, the current progress of my research, including the molecular design of pH-sensitive cationic lipids, their applications for various tissues and cell types, and for delivering various macromolecules, including siRNA, antisense oligonucleotide, mRNA, and the clustered regularly interspaced short palindromic repeats (CRISPR)-associated (Cas) system will be described. Mechanistic studies regarding relationships between the physicochemical properties of LNPs, drug delivery, and biosafety are also summarized. Furthermore, current issues that need to be addressed for next generation drug delivery systems are discussed.

Physical transfection technologies for macrophages and dendritic cells in immunotherapy

INTRODUCTION

Dendritic cells (DCs) and macrophages, two important antigen presenting cells (APCs) of the innate immune system, are being explored for the use in cell-based cancer immunotherapy. For this application, the therapeutic potential of patient-derived APCs is increased by delivering different types of functional macromolecules, such as mRNA and pDNA, into their cytosol. Compared to the use of viral and non-viral delivery vectors, physical intracellular delivery techniques are known to be more straightforward, more controllable, faster and generate high delivery efficiencies.

AREAS COVERED

This review starts with electroporation as the most traditional physical transfection method, before continuing with the more recent technologies such as sonoporation, nanowires and microfluidic cell squeezing. A description is provided of each of those intracellular delivery technologies with their strengths and weaknesses, especially paying attention to delivery efficiency and safety profile.

EXPERT OPINION

Given the common use of electroporation for the production of therapeutic APCs, it is recommended that more detailed studies are performed on the effect of electroporation on APC fitness, even down to the genetic level. Newer intracellular delivery technologies seem to have less impact on APC functionality but further work is needed to fully uncover their suitability to transfect APCs with different types of macromolecules.

Enhanced intracellular delivery via coordinated acoustically driven shear mechanoporation and electrophoretic insertion

Delivery of large and structurally complex target molecules into cells is vital to the emerging areas of cellular modification and molecular therapy. Inadequacy of prevailing in vivo (viral) and in vitro (liposomal) gene transfer methods for delivery of proteins and a growing diversity of synthetic nanomaterials has encouraged development of alternative physical approaches. Efficacy of injury/diffusion-based delivery via shear mechanoporation is largely insensitive to cell type and target molecule; however, enhanced flexibility is typically accompanied by reduced gene transfer effectiveness. We detail a method to improve transfection efficiency through coordinated mechanical disruption of the cell membrane and electrophoretic insertion of DNA to the cell interior. An array of micromachined nozzles focuses ultrasonic pressure waves, creating a high-shear environment that promotes transient pore formation in membranes of transmitted cells. Acoustic Shear Poration (ASP) allows passive cytoplasmic delivery of small to large nongene macromolecules into established and primary cells at greater than 75% efficiency. Addition of an electrophoretic action enables active transport of target DNA molecules to substantially augment transfection efficiency of passive mechanoporation/diffusive delivery without affecting viability. This two-stage poration/insertion method preserves the compelling flexibility of shear-based delivery, yet substantially enhances capabilities for active transport and transfection of plasmid DNA.

A lipid nanoparticle for the efficient delivery of siRNA to dendritic cells

Applying small interfering RNA (siRNA) to dendritic cell (DC) based therapy represents a potential candidate for cancer immunotherapy. However, delivering siRNA to DCs is a challenging issue for non-viral vectors. To date, only viral vectors have achieved efficient gene silencing in DCs. We report herein that a novel cationic lipid, YSK12-C4, when loaded in a nanoparticle with siRNA (YSK12-C4 multifunctional envelope type nano device [YSK12-MEND]), greatly facilitated gene silencing in mouse DCs. The use of the YSK12-MEND resulted in a gene silencing efficiency in excess of 90%, with a median effective dose (ED50) of 1.5nM, whereas the maximum gene silencing efficiency of Lipofectamine RNAiMAX was less than 60% and the ED50 was 25nM. Furthermore, suppressor of cytokine signaling 1, an immune suppressive molecule in DCs, silenced in the mouse DC by the YSK12-MEND showed a drastic enhancement in cytokine production, resulting in the significant suppression of tumor growth when it was applied to DC-based therapy against a mouse lymphoma. These results clearly indicate that YSK12-MEND overcomes the obstacle associated with non-viral vectors and can be considered to be a promising non-viral vector for siRNA delivery to DCs, thus accelerating DC-based therapies with siRNA.

Connexin43 knockdown in bone marrow‑derived dendritic cells by small interfering RNA leads to a diminished T-cell stimulation

Dendritic cells, the most powerful type of antigen‑presenting cells, have the unique ability to induce primary immune responses. Connexin43 expression is upregulated to increase gap junctions when immune cells are exposed to inflammatory factors. The present study applied small‑interfering RNA (siRNA) to decrease connexin43 expression. The results showed that silencing of connexin43 using siRNA resulted in arrest of bone marrow‑derived dendritic cell (BM‑DC) maturation as evidenced by reduced expression of major histocompatibility complex II, CD40, CD80 and CD86. Functionally, connexin43‑silenced BM‑DC showed a markedly decreased capability to induce T-cell stimulation. In conclusion, the present study demonstrated that antigens present on BM‑DCs can be suppressed by connexin43 knockdown in BM‑DCs. The present study therefore presented an effective method to modulate the immunology of BM‑DCs.

The intracellular pharmacodynamics of siRNA is responsible for the low gene silencing activity of siRNA-loaded nanoparticles in dendritic cells

The delivery of small interfering RNA (siRNA) to dendritic cells (DCs) is a challenging issue for siRNA-loaded lipid nanoparticles. The cause of this difficulty is unknown. The findings reported herein indicate that the rate-limiting step in gene silencing using siRNA-loaded lipid nanoparticles in DCs, as evidenced by a quantitative analysis of each process in siRNA delivery between mouse bone marrow derived DC (BMDC) and other cell lines, was not associated with the actual delivery of siRNA. A gene silencing of only 50% was observed in BMDC, even when a high dose was used. Contrary to our expectation, the interval between cellular uptake and the delivery of siRNA to the cytosol was not responsible for the low gene silencing. Meanwhile, a drastic difference was found in the relationship between the efficiency of gene silencing and the amount of intracellular intact siRNA. This fact indicates that the processes after cytosolic delivery of siRNA, namely the intracellular pharmacodynamics (PD) of siRNA, appear to be the rate-limiting step in gene silencing in BMDC. The findings reported here demonstrate the importance of the intracellular PD of siRNA delivered to cytosol in the development of siRNA delivery systems for gene silencing in DCs.

Cholesterol Modification of p40-Specific Small Interfering RNA Enables Therapeutic Targeting of Dendritic Cells

Small interfering RNA (siRNA)-based therapies allow targeted correction of molecular defects in distinct cell populations. Although efficient in multiple cell populations, dendritic cells (DCs) seem to resist siRNA delivery. Using fluorescence labeling and radiolabeling, we show that cholesterol modification enables siRNA uptake by DCs in vitro and in vivo. Delivery of cholesterol-modified p40 siRNA selectively abolished p40 transcription and suppressed TLR-triggered p40 production by DCs. During immunization with peptide in CFA, cholesterol-modified p40 siRNA generated p40-deficient, IL-10-producing DCs that prevented IL-17/Th17 and IFN-γ/Th1 responses. Only cholesterol-modified p40-siRNA established protective immunity against experimental autoimmune encephalomyelitis and suppressed IFN-γ and IL-17 expression by CNS-infiltrating mononuclear cells without inducing regulatory T cells. Because cholesterol-modified siRNA can thus modify selected DC functions in vivo, it is intriguing for targeted immune therapy of allergic, autoimmune, or neoplastic diseases.

Cyclic peptide-capped gold nanoparticles for enhanced siRNA delivery

Previously, we have reported the synthesis of a homochiral l-cyclic peptide [WR]5 and its use for delivery of anti-HIV drugs and biomolecules. A physical mixture of HAuCl4 and the peptide generated peptide-capped gold nanoparticles. Here, [WR]5 and [WR]5-AuNPs were tested for their efficiency to deliver a small interfering RNA molecule (siRNA) in human cervix adenocarcinoma (HeLa) cells. Flow cytometry investigation revealed that the intracellular uptake of a fluorescence-labeled non-targeting siRNA (200 nM) was enhanced in the presence of [WR]5 and [WR]5-AuNPs by 2- and 3.8-fold when compared with that of siRNA alone after 24 h incubation. Comparative toxicity results showed that [WR]5 and [WR]5-AuNPs were less toxic in cells compared to other available carrier systems, such as Lipofectamine.

siRNA delivery via electropulsation: a review of the basic processes

Due to their capacity for inducing strong and sequence specific gene silencing in cells, small interfering RNAs (siRNAs) are now recognized not only as powerful experimental tools for basic research in Molecular biology but with promising potentials in therapeutic development. Delivery is a bottleneck in many studies. There is a common opinion that full potential of siRNA as therapeutic agent will not be attained until better methodologies for its targeted intracellular delivery to cells and tissues are developed. Electropulsation (EP) is one of the physical methods successfully used to transfer siRNA into living cells in vitro and in vivo. This review will describe how siRNA electrotransfer obeys characterized biophysical processes (cell-size-dependent electropermeabilization, electrophoretic drag) with a strong control of a low loss of viability. Protocols can be easily adjusted by a proper setting of the electrical parameters and pulsing buffers. EP can be easily directly applied on animals. Preclinical studies showed that electropermeabilization brings a direct cytoplasmic distribution of siRNA and an efficient silencing of the targeted protein expression. EP appears as a promising tool for clinical applications of gene silencing. A panel of successful trials will be given.

Direct type I IFN but not MDA5/TLR3 activation of dendritic cells is required for maturation and metabolic shift to glycolysis after poly IC stimulation

Type I interferons (IFNs) play an important role in direct antiviral defense as well as linking the innate and adaptive immune responses. On dendritic cells (DCs), IFNs facilitate their activation and contribute to CD8(+) and CD4(+) T cell priming. However, the precise molecular mechanism by which IFNs regulate maturation and immunogenicity of DCs in vivo has not been studied in depth. Here we show that, after in vivo stimulation with the TLR ligand poly IC, IFNs dominate transcriptional changes in DCs. In contrast to direct TLR3/mda5 signaling, IFNs are required for upregulation of all pathways associated with DC immunogenicity. In addition, metabolic pathways, particularly the switch from oxidative phosphorylation to glycolysis, are also regulated by IFNs and required for DC maturation. These data provide evidence for a metabolic reprogramming concomitant with DC maturation and offer a novel mechanism by which IFNs modulate DC maturation.

Electroporation of siRNA into mouse bone marrow-derived macrophages and dendritic cells

Dendritic cells (DC) and macrophages (MΦ) play a pivotal role in antimicrobial defense, in the regulation of immune responses, and in maintaining tissue homeostasis. The analysis of DC and MΦ function relies on primary cells albeit these cells are known to be difficult to transfect. This makes the use of small interfering RNA (siRNA) for targeted manipulation of gene expression by RNA interference difficult. In the following chapter, we provide a detailed protocol for the successful transfer of siRNA via electroporation into a defined population of mouse bone marrow-derived MΦ or DC that does not cause toxicity to the myeloid cells or nonspecific alterations of their biological functions. Factors that influence the transfection and knockdown rate will be highlighted.

Cell-based interventions to halt autoimmunity in type 1 diabetes mellitus

Type 1 diabetes mellitus (T1DM) results from death of insulin-secreting β cells mediated by self-immune cells, and the consequent inability of the body to maintain insulin levels for appropriate glucose homeostasis. Probably initiated by environmental factors, this disease takes place in genetically predisposed individuals. Given the autoimmune nature of T1DM, therapeutics targeting immune cells involved in disease progress have been explored over the last decade. Several high-cost trials have been attempted to prevent and/or reverse T1DM. Although a definitive solution to cure T1DM is not yet available, a large amount of information about its nature and development has contributed greatly to both the improvement of patient's health care and design of new treatments. In this study, we discuss the role of different types of immune cells involved in T1DM pathogenesis and their therapeutic potential as targets and/or modified tools to treat patients. Recently, encouraging results and new approaches to sustain remnant β cell mass and to increase β cell proliferation by different cell-based means have emerged. Results coming from ongoing clinical trials employing cell therapy designed to arrest T1DM will probably proliferate in the next few years. Strategies under consideration include infusion of several types of stem cells, dendritic cells and regulatory T cells, either manipulated genetically ex vivo or non-manipulated. Their use in combination approaches is another therapeutic alternative. Cell-based interventions, without undesirable side effects, directed to block the uncontrollable autoimmune response may become a clinical reality in the next few years for the treatment of patients with T1DM.

Delivery systems and local administration routes for therapeutic siRNA

With the increasing number of studies proposing new and optimal delivery strategies for the efficacious silencing of gene-related diseases by the local administration of siRNAs, the present review aims to provide a broad overview of the most important and latest developments of non-viral siRNA delivery systems for local administration. Moreover, the main disease targets for the local delivery of siRNA to specific tissues or organs, including the skin, the lung, the eye, the nervous system, the digestive system and the vagina, were explored.

Novel protein transduction domain mimics as nonviral delivery vectors for siRNA targeting NOTCH1 in primary human T cells

RNA interference technology has recently been highlighted as a powerful research method as well as a potential therapeutic treatment for several diseases. However, the delivery of small interfering RNA (siRNA) into T cell lines and primary blood cells is exceedingly challenging, as they are resistant to transfection by conventional reagents. As a result, there is an unmet need for nonviral, efficient, and easily prepared carriers for siRNA delivery into hard-to-transfect cell types. Here, we report a novel system based on protein transduction domain mimics (PTDMs), generated by ring opening metathesis polymerization, for intracellular delivery of siRNA molecules. PTDM-based siRNA delivery induced efficient NOTCH1 knockdown in Jurkat T cells and human peripheral blood mononuclear cells without any measured toxicity. Furthermore, delivering siRNA to NOTCH1 in human peripheral blood cells modulated cell proliferation and differentiation of T cells into T(H)1 cells.

microRNA-181a represses ox-LDL-stimulated inflammatory response in dendritic cell by targeting c-Fos

Oxidized LDL (ox-LDL) activates dendritic cells (DCs), thereby initiating inflammation responses in atherosclerosis, yet the modulatory mechanisms remain unclear. MicroRNAs (miRNAs) are important regulators for DC functions. This study evaluated the regulation by miRNAs of the ox-LDL-induced DC immune response. In CD11c⁺ DCs from ApoE-deficient mice with hyperlipidemia, microRNA miR-181a was significantly up-regulated. In cultured bone marrow-derived DCs (BMDCs), ox-LDL promoted DC maturation and up-regulated miR-181a expression. Abundance of miR-181a attenuated ox-LDL-induced CD83 and CD40 expression, inhibited the secretion of interleukin (IL)-6 and TNF-α, and up-regulated IL-10, an important anti-inflammatory cytokine that was inhibited by ox-LDL. Inhibition of the endogenous miR-181a reversed the effects on CD83 and CD40 as well as the effects on IL-6 and TNF-α. The putative target genes of miR-181a were evaluated by gene ontology assessment, and the c-Fos-mediated inflammation pathway was identified. miR-181a targeted the 3′ untranslated region of c-Fos mRNA by luciferase experiments. Thus, abundance of miR-181a reduced c-Fos protein, whereas inhibition of miR-181a increased c-Fos protein in BMDCs. We therefore suggest that miR-181a attenuates ox-LDL-stimulated immune inflammation responses by targeting c-Fos in DCs.

Hypoxia-mediated impairment of the mitochondrial respiratory chain inhibits the bactericidal activity of macrophages

In infected tissues oxygen tensions are low. As innate immune cells have to operate under these conditions, we analyzed the ability of macrophages (Mφ) to kill Escherichia coli or Staphylococcus aureus in a hypoxic microenvironment. Oxygen restriction did not promote intracellular bacterial growth but did impair the bactericidal activity of the host cells against both pathogens. This correlated with a decreased production of reactive oxygen intermediates (ROI) and reactive nitrogen intermediates. Experiments with phagocyte NADPH oxidase (PHOX) and inducible NO synthase (NOS2) double-deficient Mφ revealed that in E. coli- or S. aureus-infected cells the reduced antibacterial activity during hypoxia was either entirely or partially independent of the diminished PHOX and NOS2 activity. Hypoxia impaired the mitochondrial activity of infected Mφ. Inhibition of the mitochondrial respiratory chain activity during normoxia (using rotenone or antimycin A) completely or partially mimicked the defective antibacterial activity observed in hypoxic E. coli- or S. aureus-infected wild-type Mφ, respectively. Accordingly, inhibition of the respiratory chain of S. aureus-infected, normoxic PHOX(-/-) NOS2(-/-) Mφ further raised the bacterial burden of the cells, which reached the level measured in hypoxic PHOX(-/-) NOS2(-/-) Mφ cultures. Our data demonstrate that the reduced killing of S. aureus or E. coli during hypoxia is not simply due to a lack of PHOX and NOS2 activity but partially or completely results from an impaired mitochondrial antibacterial effector function. Since pharmacological inhibition of the respiratory chain raised the generation of ROI but nevertheless phenocopied the effect of hypoxia, ROI can be excluded as the mechanism underlying the antimicrobial activity of mitochondria.

Delivery of AP-2α siRNA into cultured bovine trophoblast cells by electroporation repressed key placenta-specific gene expression

Binucleate trophoblast giant cells (BNC) characteristically appear early in gestation in the bovine placenta. They secret pivotal hormones and cytokines for feto-maternal communication, for example, expression of placental lactogens (CSH1), prolactin-related protein 1 (PRP1) and pregnancy-associated glycoprotein 1 (PAG1) are necessary for pregnancy establishment in bovine. These genes transcription are regulated in a temporal and spatial manner, however, molecular mechanisms by which these gene transcriptions are regulated in this manner have not been firmly elucidated. In this study, a cell culture model for bovine trophoblast cells was initially established, small interfering RNA duplexes against Activator Protein-2α (TFAP2A) was transfected into the cells by electroporation, and transcripts of CSH1, PRP1 and PAG1 were measured by qPCR. The results showed that trophoblast giant cells were confluent for 90% after cultured for 10 days, and BNC constituted of a population of more than 45% of the total cells. Using a fluorescein-labeled non-silencing siRNA duplex, an electroporation protocol yielding routinely >93% positive cells could be established, and siRNA duplex transfection demonstrated an efficient knockdown of cellular AP-2α mRNA level by 72.30 ± 3.28% in electroporated cells. Finally, CSH1, PRP1 and PAG1 genes expression were effectively down-regulated by 65.45 ± 6.38% (P<0.01), 40.73±11.72% (P<0.01) and 11.59 ± 1.88% (P<0.05), respectively. It was therefore suggested that electroporating siRNA into bovine trophoblast cells could be an efficient method to manipulate BNC function and to study the regulation mechanism of specific gene transcription without the use of chemical transfection reagents. It was suggested that AP-2α could be at least involved in the regulation of expression CSH1 and PRP1 transcripts.

Engineering and identifying supercharged proteins for macromolecule delivery into mammalian cells

Supercharged proteins are a class of engineered or naturally occurring proteins with unusually high positive or negative net theoretical charge. Both supernegatively and superpositively charged proteins exhibit a remarkable ability to withstand thermally or chemically induced aggregation. Superpositively charged proteins are also able to penetrate mammalian cells. Associating cargo with these proteins, such as plasmid DNA, siRNA, or other proteins, can enable the functional delivery of these macromolecules into mammalian cells both in vitro and in vivo. The potency of functional delivery in some cases can exceed that of other current methods for macromolecule delivery, including the use of cell-penetrating peptides such as Tat and adenoviral delivery vectors. This chapter summarizes methods for engineering supercharged proteins, optimizing cell penetration, identifying naturally occurring supercharged proteins, and using these proteins for macromolecule delivery into mammalian cells.

Toll-like receptor activation and hypoxia use distinct signaling pathways to stabilize hypoxia-inducible factor 1α (HIF1A) and result in differential HIF1A-dependent gene expression

HIF1A is a transcription factor that plays a central role for the adaptation to tissue hypoxia and for the inflammatory response of myeloid cells, including DCs. HIF1A is stabilized by hypoxia but also by TLR ligands under normoxic conditions. The underlying signaling events leading to the accumulation of HIF1A in the presence of oxygen are still poorly understood. Here, we show that in contrast to hypoxic stabilization of HIF1A, normoxic, TLR-mediated HIF1A accumulation in DCs follows a different pathway that predominantly requires MYD88-dependent NF-κB activity. The TLR-induced HIF1A controls a subset of proinflammatory genes that are insufficiently induced following hypoxia-mediated HIF1A induction. Thus, TLR activation and hypoxia stabilize HIF1A via distinct signaling pathways, resulting in differential HIF1A-dependent gene expression.

Inhibition of pathogen-induced apoptosis by a Coxiella burnetii type IV effector protein

Coxiella burnetii and Legionella pneumophila are evolutionarily related pathogens with different intracellular infection strategies. C. burnetii persists within and is transmitted by mammalian hosts, whereas, L. pneumophila is found primarily in the environment associated with protozoan hosts. Although a type IV secretion system encoded by the defect in organelle trafficking (dot) and intracellular multiplication (icm) genes is a virulence determinant that remains highly conserved in both bacteria, the two pathogens encode a different array of effector proteins that are delivered into host cells by the Dot/Icm machinery. This difference suggests that adaptations to evolutionarily distinct hosts may be reflected in the effector protein repertoires displayed by these two pathogens. Here we provide evidence in support of this hypothesis. We show that a unique C. burnetii effector from the ankyrin repeat (Ank) family called AnkG interferes with the mammalian apoptosis pathway. AnkG was found to interact with the host protein gC1qR (p32). Either the addition of AnkG to the repertoire of L. pneumophila effector proteins or the silencing of p32 in mouse dendritic cells resulted in a gain of function that allowed intracellular replication of L. pneumophila in these normally restrictive mammalian host cells by preventing rapid pathogen-induced apoptosis. These data indicate that p32 regulates pathogen-induced apoptosis and that AnkG functions to block this pathway. Thus, emergence of an effector protein that interferes with a proapoptotic signaling pathway directed against intracellular bacteria correlates with adaptation of a pathogen to mammalian hosts.

Small interfering RNA (siRNA) delivery into murine bone marrow-derived macrophages by electroporation

Selective gene silencing by RNA interference (RNAi) is a valuable tool for the targeted manipulation of the development and/or function of cells. Using a fluorescein-labeled non-silencing siRNA duplex, we established a protocol for the electroporation of primary mouse macrophages which routinely yielded >95% transfected cells. Electroporation of siRNAs directed against MAPK1 and CD86 led to an efficient knock-down of cellular protein in bone marrow-derived mouse macrophages (BM-Mphi). Importantly, the electroporation procedure did not impair the viability of BM-Mphi, their ability to ingest or degrade E. coli or their capacity to express iNOS mRNA, to produce NO or to upregulate TNF and IL-6 mRNA in response to inflammatory stimuli such as LPS. Therefore, we propose that electroporation of silencing siRNAs into murine BM-Mphi is a highly efficient method to manipulate gene expression of BM-Mphi that does not cause toxicity or a non-specific alteration of macrophage biology.

A comparative study of transfection methods for RNA interference in bone marrow-derived murine dendritic cells

Selective gene silencing using RNA interference (RNAi) has been shown to be an efficient method for manipulation of cellular functions. In this study, we compare three previously established methods for transfection of murine bone marrow-derived DC (BM-DC). We tested the efficacy of electroporation with the Mouse Nucleofector kit((R)) from Amaxa Biosystems and lipid-based transfection methods using transfection reagents from Santa Cruz Biotechnology or Genlantis. To analyse the transfection efficacy we used FITC-conjugated siRNA as a positive control together with CD80 and CD86 specific siRNA. We show that electroporation using the Mouse Nucleofector kit((R)) from Amaxa Biosystems was not an efficient method to transfect BM-DC with siRNA in our hands. Transfection with Santa Cruz Biotechnology reagents resulted in up to 59% FITC-siRNA positive cells, but did not result in effective silencing of CD80 surface expression. In contrast, the most effective method was the lipid-based method using the siRNA transfection reagent GeneSilencer((R)) from Genlantis. This protocol resulted in up to 92% FITC-siRNA positive cells after 4 h which declined to 62% and 59% 24 and 48 h post-transfection, respectively. The transfected BM-DC remained CD11c positive, expressed high MHC class II and intermediate CD40 and were functional as APC. In conclusion, this protocol was effective for manipulation of murine BM-DC function through the use of specific siRNA and such methods can be important for the future study of DC-T cell interactions.

siRNA delivery systems for cancer treatment

With increasing knowledge on the molecular mechanisms of endogenous RNA interference, small interfering RNAs (siRNAs) have been emerging as innovative nucleic acid medicines for treatment of incurable diseases such as cancers. Although several siRNA candidates for the treatment of ocular and respiratory diseases are undergoing clinical trials, there are challenges inherent in the further development of siRNAs for anti-cancer therapeutics, because systemic administration will be required in most cases. In addition to nonspecific off-target and immune stimulation problems, appropriate delivery remains a major hurdle. The technologies developed for delivery of nucleic acid medicines such as plasmid DNA and antisense oligonucleotides have paved the way to rapid progress for in vivo delivery of siRNAs. Here, we review various in vivo delivery strategies including chemical modification, conjugation, lipid-based techniques, polymer-based nanosystems, and physical methods. Moreover, the current progress in siRNA delivery systems for gynecologic, liver, lung, and prostate cancers is discussed.

Macrophages regulate salt-dependent volume and blood pressure by a vascular endothelial growth factor-C-dependent buffering mechanism

In salt-sensitive hypertension, the accumulation of Na(+) in tissue has been presumed to be accompanied by a commensurate retention of water to maintain the isotonicity of body fluids. We show here that a high-salt diet (HSD) in rats leads to interstitial hypertonic Na(+) accumulation in skin, resulting in increased density and hyperplasia of the lymphcapillary network. The mechanisms underlying these effects on lymphatics involve activation of tonicity-responsive enhancer binding protein (TonEBP) in mononuclear phagocyte system (MPS) cells infiltrating the interstitium of the skin. TonEBP binds the promoter of the gene encoding vascular endothelial growth factor-C (VEGF-C, encoded by Vegfc) and causes VEGF-C secretion by macrophages. MPS cell depletion or VEGF-C trapping by soluble VEGF receptor-3 blocks VEGF-C signaling, augments interstitial hypertonic volume retention, decreases endothelial nitric oxide synthase expression and elevates blood pressure in response to HSD. Our data show that TonEBP-VEGF-C signaling in MPS cells is a major determinant of extracellular volume and blood pressure homeostasis and identify VEGFC as an osmosensitive, hypertonicity-driven gene intimately involved in salt-induced hypertension.

The DC-HIL/syndecan-4 pathway inhibits human allogeneic T-cell responses

T-cell activation is regulated by binding of ligands on APC to corresponding receptors on T cells. In mice, we discovered that binding of DC-HIL on APC to syndecan-4 (SD-4) on activated T cells potently inhibits T-cell activation. In humans, we now show that DC-HIL also binds to SD-4 on activated T cells through recognition of its heparinase-sensitive saccharide moiety. DC-HIL blocks anti-CD3-induced T-cell responses, reducing secretion of pro-inflammatory cytokines and blocking entry into the S phase of the cell cycle. Binding of DC-HIL phosphorylates SD-4's intracellular tyrosine and serine residues. Anti-SD-4 Ab mimics the ability of DC-HIL to attenuate anti-CD3 response more potently than Ab directed against other inhibitory receptors (CTLA-4 or programmed cell death-1). Among leukocytes, DC-HIL is expressed highest by CD14(+) monocytes and this expression can be upregulated markedly by TGF-beta. Among APC, DC-HIL is expressed highest by epidermal Langerhans cells, an immature type of dendritic cells. Finally, the level of DC-HIL expression on CD14(+) monocytes correlates inversely with allostimulatory capacity, such that treatment with TGF-beta reduced this capacity, whereas knocking down the DC-HIL gene augmented it. Our findings indicate that the DC-HIL/SD-4 pathway can be manipulated to treat T-cell-driven disorders in humans.

Mammalian cell penetration, siRNA transfection, and DNA transfection by supercharged proteins

Nucleic acid reagents, including small interfering RNA (siRNA) and plasmid DNA, are important tools for the study of mammalian cells and are promising starting points for the development of new therapeutic agents. Realizing their full potential, however, requires nucleic acid delivery reagents that are simple to prepare, effective across many mammalian cell lines, and nontoxic. We recently described the extensive surface mutagenesis of proteins in a manner that dramatically increases their net charge. Here, we report that superpositively charged green fluorescent proteins, including a variant with a theoretical net charge of +36 (+36 GFP), can penetrate a variety of mammalian cell lines. Internalization of +36 GFP depends on nonspecific electrostatic interactions with sulfated proteoglycans present on the surface of most mammalian cells. When +36 GFP is mixed with siRNA, protein-siRNA complexes approximately 1.7 mum in diameter are formed. Addition of these complexes to five mammalian cell lines, including four that are resistant to cationic lipid-mediated siRNA transfection, results in potent siRNA delivery. In four of these five cell lines, siRNA transfected by +36 GFP suppresses target gene expression. We show that +36 GFP is resistant to proteolysis, is stable in the presence of serum, and extends the serum half-life of siRNA and plasmid DNA with which it is complexed. A variant of +36 GFP can mediate DNA transfection, enabling plasmid-based gene expression. These findings indicate that superpositively charged proteins can overcome some of the key limitations of currently used transfection agents.