Image-Guided Hydrodynamic Gene Delivery: Current Status and Future Directions

A non-viral DNA delivery system consisting of multifunctional chimeric peptide fused with zinc-finger protein

Non-viral gene delivery systems have received sustained attention as a promising alternative to viral vectors for disease treatment and prevention in recent years. Numerous methods have been developed to enhance gene uptake and delivery in the cytoplasm; however, due to technical difficulties and delivery efficiency, these systems still face challenges in a range of biological applications, especially in vivo. To alleviate this challenge, we devised a novel system for gene delivery based on a recombinant protein eTAT-ZF9-NLS, which consisted of a multifunctional chimeric peptide and a zinc-finger protein with sequence-specific DNA-binding activity. High transfection efficiency was observed in several mammalian cells after intracellular delivery of plasmid containing ZF9-binding sites mediated by eTAT-ZF9-NLS. Our new approach provides a novel transfection strategy and the transfection efficiency was confirmed both in vitro and in vivo, making it a preferential transfection reagent for possible gene therapy.

Prospects and challenges of CRISPR/Cas9 gene-editing technology in cancer research

Cancer, one of the leading causes of death, usually commences and progresses as a result of a series of gene mutations and dysregulation of expression. With the development of clustered regularly interspaced palindromic repeat (CRISPR)/Cas9 gene-editing technology, it is possible to edit and then decode the functions of cancer-related gene mutations, markedly advance the research of biological mechanisms and treatment of cancer. This review summarizes the mechanism and development of CRISPR/Cas9 gene-editing technology in recent years and describes its potential application in cancer-related research, such as the establishment of human tumor disease models, gene therapy and immunotherapy. The challenges and future development directions are highlighted to provide a reference for exploring pathological mechanisms and potential treatment protocols of cancer.

In vivo bioluminescence imaging of labile iron in xenograft models and liver using FeAL-1, an iron-activatable form of D-luciferin

Dysregulated iron homeostasis underlies diverse pathologies, from ischemia-reperfusion injury to epithelial-mesenchymal transition and drug-tolerant "persister" cancer cell states. Here, we introduce ferrous iron-activatable luciferin-1 (FeAL-1), a small-molecule probe for bioluminescent imaging of the labile iron pool (LIP) in luciferase-expressing cells and animals. We find that FeAL-1 detects LIP fluctuations in cells after iron supplementation, depletion, or treatment with hepcidin, the master regulator of systemic iron in mammalian physiology. Utilizing FeAL-1 and a dual-luciferase reporter system, we quantify LIP in mouse liver and three different orthotopic pancreatic ductal adenocarcinoma tumors. We observed up to a 10-fold increase in FeAL-1 bioluminescent signal in xenograft tumors as compared to healthy liver, the major organ of iron storage in mammals. Treating mice with hepcidin further elevated hepatic LIP, as predicted. These studies reveal a therapeutic index between tumoral and hepatic LIP and suggest an approach to sensitize tumors toward LIP-activated therapeutics.

Delivery of gene editing therapeutics

For the past decades, gene editing demonstrated the potential to attenuate each of the root causes of genetic, infectious, immune, cancerous, and degenerative disorders. More recently, Clustered Regularly Interspaced Short Palindromic Repeats-CRISPR-associated protein 9 (CRISPR-Cas9) editing proved effective for editing genomic, cancerous, or microbial DNA to limit disease onset or spread. However, the strategies to deliver CRISPR-Cas9 cargos and elicit protective immune responses requires safe delivery to disease targeted cells and tissues. While viral vector-based systems and viral particles demonstrate high efficiency and stable transgene expression, each are limited in their packaging capacities and secondary untoward immune responses. In contrast, the nonviral vector lipid nanoparticles were successfully used for as vaccine and therapeutic deliverables. Herein, we highlight each available gene delivery systems for treating and preventing a broad range of infectious, inflammatory, genetic, and degenerative diseases. STATEMENT OF SIGNIFICANCE: CRISPR-Cas9 gene editing for disease treatment and prevention is an emerging field that can change the outcome of many chronic debilitating disorders.

Early Subcellular Hepatocellular Alterations in Mice Post Hydrodynamic Transfection: An Explorative Study

Hydrodynamic transfection (HT) or hydrodynamic tail vein injection (HTVi) is among the leading technique that is used to deliver plasmid genes mainly into the liver of live mice or rats. The DNA constructs are composed of coupled plasmids, while one contains the gene of interest that stably integrate into the hepatocyte genome with help of the other consisting sleeping beauty transposase system. The rapid injection of a large volume of DNA-solution through the tail vein induces an acute cardiac congestion that refluxed into the liver, mainly in acinus zone 3, also found through our EM study. Although, HT mediated hydrodynamic force can permeabilizes the fenestrated sinusoidal endothelium of liver, but the mechanism of plasmid incorporation into the hepatocytes remains unclear. Therefore, in the present study, we have hydrodynamically injected 2 mL volume of empty plasmid (transposon vector) or saline solution (control) into the tail vein of anesthetized C57BL/6J/129Sv mice. Liver tissue was resected at different time points from two animal group conditions, i.e., one time point per animal (1, 5, 10-20, 60 min or 24 and 48 hrs after HT) or multiple time points per animal (0, 1, 2, 5, 10, 20 min) and quickly fixed with buffered 4% osmium tetroxide. The tissues fed with only saline solution was also resected and fixed in the similar way. EM evaluation from the liver ultrathin sections reveals that swiftly after 1 min, the hepatocytes near to the central venule in the acinus zone 3 shows cytoplasmic membrane-bound vesicles. Such vesicles increased in both numbers and size to vacuoles and precisely often found in the proximity to the nucleus. Further, EM affirm these vacuoles are also optically empty and do not contain any electron dense material. Although, some of the other hepatocytes reveals sign of cell damage including swollen mitochondria, dilated endoplasmic reticulum, Golgi apparatus and disrupted plasma membrane, but most of the hepatocytes appeared normal. The ultrastructural findings in the mice injected with empty vector or saline injected control mice were similar. Therefore, we have interpreted the vacuole formation as nonspecific endocytosis without specific interactions at the plasma membrane.

In Vivo Tissue-Specific DNA Demethylation in Mouse Liver Through a Hydrodynamic Tail Vein Injection

A new technique called the dCas9-SunTag and scFv-TET1CD epigenome editing system has recently been developed to edit the DNA methylation status of specific genes. The transfection of an all-in-one vector containing this system into cells is feasible and induces the DNA demethylation of specific genes; however, due to the large size of the vector, difficulties are associated with its introduction into mice. We herein used a hydrodynamic tail vein injection (HTVi) to introduce the all-in-one vector into mice for in vivo epigenome editing. HTVi needs to be considered for inducing the targeted DNA demethylation of particular genes in the mouse liver.

A review of the tortuous path of nonviral gene delivery and recent progress

Gene therapy encompasses the transfer of exogenous genetic materials into the patient's target cells to treat or prevent diseases. Nevertheless, the transfer of genetic material into desired cells is challenging and often requires specialized tools or delivery systems. For the past 40 years, scientists are mainly pursuing various viruses as gene delivery vectors, and the overall progress has been slow and far from the expectation. As an alternative, nonviral vectors have gained substantial attention due to their several advantages, including superior safety profile, enhanced payload capacity, and stealth abilities. Since nonviral vectors encounter multiple extra- and intra-cellular barriers limiting the transfer of genetic payload into the target cell nucleus, we have discussed these barriers in detail for this review. A direct approach, utilizing physical methods like electroporation, sonoporation, gene gun, eliminate the requirement for a specific carrier for gene delivery. In contrast, chemical methods of gene transfer exploit natural or synthetic compounds as carriers to increase cellular targeting and gene therapy effectiveness. We have also emphasized the recent advancements aimed at enhancing the current nonviral approaches. Therefore, in this review, we have focused on discussing the current evolving state of nonviral gene delivery systems and their future perspectives.

Evolutionary Timeline of Genetic Delivery and Gene Therapy

There are more than 3,500 genes that are being linked to hereditary diseases or correlated with an elevated risk of certain illnesses. As an alternative to conventional treatments with small molecule drugs, gene therapy has arisen as an effective treatment with the potential to not just alleviate disease conditions but also cure them completely. In order for these treatment regimens to work, genes or editing tools intended to correct diseased genetic material must be efficiently delivered to target sites. There have been many techniques developed to achieve such a goal. In this article, we systematically review a variety of gene delivery and therapy methods that include physical methods, chemical and biochemical methods, viral methods, and genome editing. We discuss their historical discovery, mechanisms, advantages, limitations, safety, and perspectives.

Gene therapy for the mitochondrial genome: Purging mutations, pacifying ailments

In the recent years, the reported cases of mitochondrial disorders have reached a colossal number. These disorders spawn a sundry of pathological conditions, which lead to pernicious symptoms and even fatality. Due to the unpredictable etiologies, mitochondrial diseases are putatively referred to as "mystondria" (mysterious diseases of mitochondria). Although present-day research has greatly improved our understanding of mitochondrial disorders, effective therapeutic interventions are still at the precursory stage. The conundrum becomes further complicated because these pathologies might occur due to either mitochondrial DNA (mtDNA) mutations or due to mutations in the nuclear DNA (nDNA), or both. While correcting nDNA mutations by using gene therapy (replacement of defective genes by delivering wild-type (WT) ones into the host cell, or silencing a dominant mutant allele that is pathogenic) has emerged as a promising strategy to address some mitochondrial diseases, the complications in correcting the defects of mtDNA in order to renovate mitochondrial functions have remained a steep challenge. In this review, we focus specifically on the selective gene therapy strategies that have demonstrated prospects in targeting the pathological mutations in the mitochondrial genome, thereby treating mitochondrial ailments.

Translational Advances of Hydrofection by Hydrodynamic Injection

Hydrodynamic gene delivery has proven to be a safe and efficient procedure for gene transfer, able to mediate, in murine model, therapeutic levels of proteins encoded by the transfected gene. In different disease models and targeting distinct organs, it has been demonstrated to revert the pathologic symptoms and signs. The therapeutic potential of hydrofection led different groups to work on the clinical translation of the procedure. In order to prevent the hemodynamic side effects derived from the rapid injection of a large volume, the conditions had to be moderated to make them compatible with its use in mid-size animal models such as rat, hamster and rabbit and large animals as dog, pig and primates. Despite the different approaches performed to adapt the conditions of gene delivery, the results obtained in any of these mid-size and large animals have been poorer than those obtained in murine model. Among these different strategies to reduce the volume employed, the most effective one has been to exclude the vasculature of the target organ and inject the solution directly. This procedure has permitted, by catheterization and surgical procedures in large animals, achieving protein expression levels in tissue close to those achieved in gold standard models. These promising results and the possibility of employing these strategies to transfer gene constructs able to edit genes, such as CRISPR, have renewed the clinical interest of this procedure of gene transfer. In order to translate the hydrodynamic gene delivery to human use, it is demanding the standardization of the procedure conditions and the molecular parameters of evaluation in order to be able to compare the results and establish a homogeneous manner of expressing the data obtained, as ‘classic’ drugs.

High and long-term von Willebrand factor expression after Sleeping Beauty transposon-mediated gene therapy in a mouse model of severe von Willebrand disease

Essentials von Willebrand disease (VWD) is the most common inherited bleeding disorder. Gene therapy for VWD offers long-term therapy for VWD patients. Transposons efficiently integrate the large von Willebrand factor (VWF) cDNA in mice. Liver-directed transposons support sustained VWF expression with suboptimal multimerization.

SUMMARY

Background Type 3 von Willebrand disease (VWD) is characterized by complete absence of von Willebrand factor (VWF). Current therapy is limited to treatment with exogenous VWF/FVIII products, which only provide a short-term solution. Gene therapy offers the potential for a long-term treatment for VWD. Objectives To develop an integrative Sleeping Beauty (SB) transposon-mediated VWF gene transfer approach in a preclinical mouse model of severe VWD. Methods We established a robust platform for sustained transgene murine VWF (mVWF) expression in the liver of Vwf-/- mice by combining a liver-specific promoter with a sandwich transposon design and the SB100X transposase via hydrodynamic gene delivery. Results The sandwich SB transposon was suitable to deliver the full-length mVWF cDNA (8.4 kb) and supported supra-physiological expression that remained stable for up to 1.5 years after gene transfer. The sandwich vector stayed episomal (~60 weeks) or integrated in the host genome, respectively, in the absence or presence of the transposase. Transgene integration was confirmed using carbon tetrachloride-induced liver regeneration. Analysis of integration sites by high-throughput analysis revealed random integration of the sandwich vector. Although the SB vector supported long-term expression of supra-physiological VWF levels, the bleeding phenotype was not corrected in all mice. Long-term expression of VWF by hepatocytes resulted in relatively reduced amounts of high-molecular-weight multimers, potentially limiting its hemostatic efficacy. Conclusions Although this integrative platform for VWF gene transfer is an important milestone of VWD gene therapy, cell type-specific targeting is yet to be achieved.

Engineering the Delivery System for CRISPR-Based Genome Editing

Clustered regularly interspaced short palindromic repeat-CRISPR-associated protein (CRISPR-Cas) systems, found in nature as microbial adaptive immune systems, have been repurposed into an important tool in biological engineering and genome editing, providing a programmable platform for precision gene targeting. These tools have immense promise as therapeutics that could potentially correct disease-causing mutations. However, CRISPR-Cas gene editing components must be transported directly to the nucleus of targeted cells to exert a therapeutic effect. Thus, efficient methods of delivery will be critical to the success of therapeutic genome editing applications. Here, we review current strategies available for in vivo delivery of CRISPR-Cas gene editing components and outline challenges that need to be addressed before this powerful tool can be deployed in the clinic.

Efficacy and Safety of Pancreas-Targeted Hydrodynamic Gene Delivery in Rats

Development of an effective, safe, and convenient method for gene delivery to the pancreas is a critical step toward gene therapy for pancreatic diseases. Therefore, we tested the possibility of applying the principle of hydrodynamic gene delivery for successful gene transfer to pancreas using rats as a model. The established procedure involves the insertion of a catheter into the superior mesenteric vein with temporary blood flow occlusion at the portal vein and hydrodynamic injection of DNA solution. We demonstrated that our procedure achieved efficient pancreas-specific gene expression that was 2,000-fold higher than that seen in the pancreas after the systemic hydrodynamic gene delivery. In addition, the level of gene expression achieved in the pancreas by the pancreas-specific gene delivery was comparable to the level in the liver achieved by a liver-specific hydrodynamic gene delivery. The optimal level of reporter gene expression in the pancreas requires an injection volume equivalent to 2.0% body weight with flow rate of 1 mL/s and plasmid DNA concentration at 5 μg/mL. With the exception of transient expansion of intercellular spaces and elevation of serum amylase levels, which recovered within 3 days, no permanent tissue damage was observed. These results suggest that pancreas-targeted hydrodynamic gene delivery is an effective and safe method for gene delivery to the pancreas and clinically applicable.

Transgene Expression in Dogs After Liver-Directed Hydrodynamic Delivery of Sleeping Beauty Transposons Using Balloon Catheters

The Sleeping Beauty transposon system has been extensively tested for integration of reporter and therapeutic genes in vitro and in vivo in mice. Dogs were used as a large animal model for human therapy and minimally invasive infusion of DNA solutions. DNA solutions were delivered into the entire liver or the left side of the liver using balloon catheters for temporary occlusion of venous outflow. A peak intravascular pressure between 80 and 140 mmHg supported sufficient DNA delivery in dog liver for detection of secretable reporter proteins. Secretable reporters allowed monitoring of the time course of gene products detectable in the circulation postinfusion. Canine secreted alkaline phosphatase reporter protein levels were measured in plasma, with expression detectable for up to 6 weeks, while expression of canine erythropoietin was detectable for 7-10 days. All animals exhibited a transient increase in blood transaminases that normalized within 10 days; otherwise the treated animals were clinically normal. These results demonstrate the utility of a secreted reporter protein for real-time monitoring of gene expression in the liver in a large animal model but highlight the need for improved delivery in target tissues to support integration and long-term expression of Sleeping Beauty transposons.

In vivo direct reprogramming of liver cells to insulin producing cells by virus-free overexpression of defined factors

Direct reprogramming of autologous cells from diabetes patients to insulin producing cells is a new method for pancreatic cell replacement therapy. At present, transdifferentiation among mature cells is achieved mainly by introducing foreign genes into the starting tissue with viral vector, but there are potentical safety problems. In the present study, we delivered plasmids carrying Pdx1, Neurog3 and MafA genes (PNM) into mouse hepatocytes by hydrodynamics tail vein injection, investigated islet β cells markers in transfected cells from protein and mRNA level, and then observed the long-term control of blood glucose in diabetic mice. We found that hepatocytes could be directly reprogrammed into insulin-producing cells after PNM gene transfection by non-viral hydrodynamics injection, and fasting blood glucose was reduced to normal, and lasted until 100 days after transfection. Intraperitoneal glucose tolerance test (IPGTT) showed that glucose regulation ability was improved gradually and the serum insulin level approached to the level of normal mice with time. Insulin-positive cells were found in the liver tissue, and the expression of various islet β-cell-specific genes were detected at the mRNA level, including islet mature marker gene Ucn3. In conclusion, we provide a new approach for the treatment of diabetes by in vivo direct reprogramming of liver cells to insulin producing cells through non-viral methods.

Kidney-specific transposon-mediated gene transfer in vivo

Methods enabling kidney-specific gene transfer in adult mice are needed to develop new therapies for kidney disease. We attempted kidney-specific gene transfer following hydrodynamic tail vein injection using the kidney-specific podocin and gamma-glutamyl transferase promoters, but found expression primarily in the liver. In order to achieve kidney-specific transgene expression, we tested direct hydrodynamic injection of a DNA solution into the renal pelvis and found that luciferase expression was strong in the kidney and absent from extra-renal tissues. We observed heterogeneous, low-level transfection of the collecting duct, proximal tubule, distal tubule, interstitial cells, and rarely glomerular cells following injection. To assess renal injury, we performed the renal pelvis injections on uninephrectomised mice and found that their blood urea nitrogen was elevated at two days post-transfer but resolved within two weeks. Although luciferase expression quickly decreased following renal pelvis injection, the use of the piggyBac transposon system improved long-term expression. Immunosuppression with cyclophosphamide stabilised luciferase expression, suggesting immune clearance of the transfected cells occurs in immunocompetent animals. Injection of a transposon expressing erythropoietin raised the haematocrit, indicating that the developed injection technique can elicit a biologic effect in vivo. Hydrodynamic renal pelvis injection enables transposon mediated-kidney specific gene transfer in adult mice.

Long-Term Prevention of Congenital Thrombotic Thrombocytopenic Purpura in ADAMTS13 Knockout Mice by Sleeping Beauty Transposon-Mediated Gene Therapy

OBJECTIVE

Severe deficiency in the von Willebrand factor-cleaving protease ADAMTS13 (a disintegrin and metalloproteinase with thrombospondin type 1 motif, member 13) because of mutations in the ADAMTS13 gene can lead to acute episodes of congenital thrombotic thrombocytopenic purpura (TTP), requiring prompt treatment. Current treatment consists of therapeutic or prophylactic infusions of fresh frozen plasma. However, lifelong treatment with plasma products is a stressful therapy for TTP patients. Here, we describe the use of the nonviral sleeping beauty (SB) transposon system as a gene therapeutic approach to realize lifelong expression of ADAMTS13 and subsequent protection against congenital TTP.

APPROACH AND RESULTS

We demonstrated that hydrodynamic tail vein injection of the SB100X system expressing murine ADAMTS13 in Adamts13^-/- mice resulted in long-term expression of supraphysiological levels of transgene ADAMTS13 over a period of 25 weeks. Stably expressed ADAMTS13 efficiently removed the prothrombotic ultralarge von Willebrand factor multimers present in the circulation of Adamts13^-/- mice. Moreover, mice stably expressing ADAMTS13 were protected against TTP. The treated mice did not develop severe thrombocytopenia or did organ damage occur when triggered with recombinant von Willebrand factor, and this up to 20 weeks after gene transfer.

CONCLUSIONS

These data demonstrate the feasibility of using SB100X-mediated gene therapy to achieve sustained expression of transgene ADAMTS13 and long-term prophylaxis against TTP in Adamts13^-/- mice.

Effects of Fibrotic Tissue on Liver-targeted Hydrodynamic Gene Delivery

Hydrodynamic gene delivery is a common method for gene transfer to the liver of small animals, and its clinical applicability in large animals has been demonstrated. Previous studies focused on functional analyses of therapeutic genes in animals with normal livers and little, however, is known regarding its effectiveness and safety in animals with liver fibrosis. Therefore, this study aimed to examine the effects of liver fibrosis on hydrodynamic gene delivery efficiency using a rat liver fibrosis model. We demonstrated for the first time, using pCMV-Luc plasmid, that this procedure is safe and that the amount of fibrotic tissue in the liver decreases gene delivery efficiency, resulting in decrease in luciferase activity depending on the volume of fibrotic tissue in the liver and the number of hepatocytes that are immunohistochemically stained positive for transgene product. We further demonstrate that antifibrotic gene therapy with matrix metalloproteinase-13 gene reduces liver fibrosis and improves efficiency of hydrodynamic gene delivery. These results demonstrate the negative effects of fibrotic tissue on hydrodynamic gene delivery and its recovery by appropriate antifibrotic therapy.