Structural impact of hydrodynamic injection on mouse liver

Morphomolecular pathology and Genomic Insights into the Cells of Origin of Cholangiocarcinoma and combined Hepatocellular-Cholangiocarcinoma

Cholangiocarcinoma is a highly heterogenous group of malignancies that, despite recent progress in the understanding of its molecular pathogenesis and clinical management, continue to pose a major challenge to public health. The traditional view posits that cholangiocarcinomas derive from the neoplastic transformation of cholangiocytes lining the biliary tree. However, increasing genetic and experimental evidence has recently pointed to a more complex - and nuanced - scenario for the potential cell of origin of cholangiocarcinomas, with hepatocytes as well as hepatic stem/progenitor cells being considered as additional potential sources, depending on microenvironmental contexts including liver injury. The hypothesis of potentially diverse cells of origin for CCA, albeit controversial, is certainly not surprising given the plasticity of the cells populating the liver as well as the existence of liver cancer subtypes with mixed histological and molecular features. This review carefully looks at the current pathological, genomic and experimental evidence supporting the existence of multiple cells of origin of liver and biliary tract cancers, with particular focus on cholangiocarcinoma and combined hepatocellular-cholangiocarcinoma.

Aldehydes alter TGF-β signaling and induce obesity and cancer

Obesity and fatty liver diseases-metabolic dysfunction-associated steatotic liver disease (MASLD) and metabolic dysfunction-associated steatohepatitis (MASH)-affect over one-third of the global population and are exacerbated in individuals with reduced functional aldehyde dehydrogenase 2 (ALDH2), observed in approximately 560 million people. Current treatment to prevent disease progression to cancer remains inadequate, requiring innovative approaches. We observe that Aldh2-/- and Aldh2-/-Sptbn1+/- mice develop phenotypes of human metabolic syndrome (MetS) and MASH with accumulation of endogenous aldehydes such as 4-hydroxynonenal (4-HNE). Mechanistic studies demonstrate aberrant transforming growth factor β (TGF-β) signaling through 4-HNE modification of the SMAD3 adaptor SPTBN1 (β2-spectrin) to pro-fibrotic and pro-oncogenic phenotypes, which is restored to normal SMAD3 signaling by targeting SPTBN1 with small interfering RNA (siRNA). Significantly, therapeutic inhibition of SPTBN1 blocks MASH and fibrosis in a human model and, additionally, improves glucose handling in Aldh2-/- and Aldh2-/-Sptbn1+/- mice. This study identifies SPTBN1 as a critical regulator of the functional phenotype of toxic aldehyde-induced MASH and a potential therapeutic target.

OBSERVE: guidelines for the refinement of rodent cancer models

Existing guidelines on the preparation (Planning Research and Experimental Procedures on Animals: Recommendations for Excellence (PREPARE)) and reporting (Animal Research: Reporting of In Vivo Experiments (ARRIVE)) of animal experiments do not provide a clear and standardized approach for refinement during in vivo cancer studies, resulting in the publication of generic methodological sections that poorly reflect the attempts made at accurately monitoring different pathologies. Compliance with the 3Rs guidelines has mainly focused on reduction and replacement; however, refinement has been harder to implement. The Oncology Best-practices: Signs, Endpoints and Refinements for in Vivo Experiments (OBSERVE) guidelines are the result of a European initiative supported by EurOPDX and INFRAFRONTIER, and aim to facilitate the refinement of studies using in vivo cancer models by offering robust and practical recommendations on approaches to research scientists and animal care staff. We listed cancer-specific clinical signs as a reference point and from there developed sets of guidelines for a wide variety of rodent models, including genetically engineered models and patient derived xenografts. In this Consensus Statement, we systematically and comprehensively address refinement and monitoring approaches during the design and execution of murine cancer studies. We elaborate on the appropriate preparation of tumor-initiating biologicals and the refinement of tumor-implantation methods. We describe the clinical signs to monitor associated with tumor growth, the appropriate follow-up of animals tailored to varying clinical signs and humane endpoints, and an overview of severity assessment in relation to clinical signs, implantation method and tumor characteristics. The guidelines provide oncology researchers clear and robust guidance for the refinement of in vivo cancer models.

HDI-STARR-seq: Condition-specific enhancer discovery in mouse liver in vivo

Background

STARR-seq and other massively-parallel reporter assays are widely used to discover functional enhancers in transfected cell models, which can be confounded by plasmid vector-induced type-I interferon immune responses and lack the multicellular environment and endogenous chromatin state of complex mammalian tissues.

Results

Here, we describe HDI-STARR-seq, which combines STARR-seq plasmid library delivery to the liver, by hydrodynamic tail vein injection (HDI), with reporter RNA transcriptional initiation driven by a minimal Albumin promoter, which we show is essential for mouse liver STARR-seq enhancer activity assayed 7 days after HDI. Importantly, little or no vector-induced innate type-I interferon responses were observed. Comparisons of HDI-STARR-seq activity between male and female mouse livers and in livers from males treated with an activating ligand of the transcription factor CAR (Nr1i3) identified many condition-dependent enhancers linked to condition-specific gene expression. Further, thousands of active liver enhancers were identified using a high complexity STARR-seq library comprised of ~ 50,000 genomic regions released by DNase-I digestion of mouse liver nuclei. When compared to stringently inactive library sequences, the active enhancer sequences identified were highly enriched for liver open chromatin regions with activating histone marks (H3K27ac, H3K4me1, H3K4me3), were significantly closer to gene transcriptional start sites, and were significantly depleted of repressive (H3K27me3, H3K9me3) and transcribed region histone marks (H3K36me3).

Conclusions

HDI-STARR-seq offers substantial improvements over current methodologies for large scale, functional profiling of enhancers, including condition-dependent enhancers, in liver tissue in vivo, and can be adapted to characterize enhancer activities in a variety of species and tissues by selecting suitable tissue- and species-specific promoter sequences.

HDI-STARR-seq: Condition-specific enhancer discovery in mouse liver in vivo

STARR-seq and other massively-parallel reporter assays are widely used to discover functional enhancers in transfected cell models, which can be confounded by plasmid vector-induced type-I interferon immune responses and lack the multicellular environment and endogenous chromatin state of complex mammalian tissues. Here, we describe HDI-STARR-seq, which combines STARR-seq plasmid library delivery to the liver, by hydrodynamic tail vein injection (HDI), with reporter RNA transcriptional initiation driven by a minimal Albumin promoter, which we show is essential for mouse liver STARR-seq enhancer activity assayed 7 days after HDI. Importantly, little or no vector-induced innate type-I interferon responses were observed. Comparisons of HDI-STARR-seq activity between male and female mouse livers and in livers from males treated with an activating ligand of the transcription factor CAR (Nr1i3) identified many condition-dependent enhancers linked to condition-specific gene expression. Further, thousands of active liver enhancers were identified using a high complexity STARR-seq library comprised of ~50,000 genomic regions released by DNase-I digestion of mouse liver nuclei. When compared to stringently inactive library sequences, the active enhancer sequences identified were highly enriched for liver open chromatin regions with activating histone marks (H3K27ac, H3K4me1, H3K4me3), were significantly closer to gene transcriptional start sites, and were significantly depleted of repressive (H3K27me3, H3K9me3) and transcribed region histone marks (H3K36me3). HDI-STARR-seq offers substantial improvements over current methodologies for large scale, functional profiling of enhancers, including condition-dependent enhancers, in liver tissue in vivo, and can be adapted to characterize enhancer activities in a variety of species and tissues by selecting suitable tissue- and species-specific promoter sequences.

Severity Classification of Laboratory Animal Procedures in Two Belgian Academic Institutions

According to the EU Directive 2010/63, all animal procedures must be classified as non-recovery, mild, moderate or severe. Several examples are included in the Directive to help in severity classification. Since the implementation of the Directive, different publications and guidelines have been disseminated on the topic. However, due to the large variety of disease models and animal procedures carried out in many different animal species, guidance on the severity classification of specific procedures or models is often lacking or not specific enough. The latter is especially the case in disease models where the level of pain, suffering, distress and lasting harm depends on the duration of the study (for progressive disease models) or the dosage given (for infectious or chemically induced disease models). This, in turn, may lead to inconsistencies in severity classification between countries, within countries and even within institutions. To overcome this, two Belgian academic institutions with a focus on biomedical research collaborated to develop a severity classification for all the procedures performed. This work started with listing all in-house procedures and assigning them to 16 (sub)categories. First, we determined which parameters, such as clinical signs, dosage or duration, were crucial for severity classification within a specific (sub)category. Next, a severity classification was assigned to the different procedures, which was based on professional judgment by the designated veterinarians, members of the animal welfare body (AWB) and institutional animal ethics committee (AEC), integrating the available literature and guidelines. During the classification process, the use of vague terminology, such as 'minor impact', was avoided as much as possible. Instead, well-defined cut-offs between severity levels were used. Furthermore, we sought to define common denominators to group procedures and to be able to classify new procedures more easily. Although the primary aim is to address prospective severity, this can also be used to assess actual severity. In summary, we developed a severity classification for all procedures performed in two academic, biomedical institutions. These include many procedures and disease models in a variety of animal species for which a severity classification was not reported so far, or the terms that assign them to a different severity were too vague.

Dyrk2 gene transfer suppresses hepatocarcinogenesis by promoting the degradation of Myc and Hras

Background & Aims

Hepatocellular carcinoma (HCC) is one of the most common cancers worldwide, and has a poor prognosis. However, the molecular mechanisms underlying hepatocarcinogenesis and progression remain unknown. In vitro gain- and loss-of-function analyses in cell lines and xenografts revealed that dual-specificity tyrosine-regulated kinase 2 (DYRK2) influences tumour growth in HCC.

Methods

To investigate the role of Dyrk2 during hepatocarcinogenesis, we developed liver-specific Dyrk2 conditional knockout mice and an in vivo gene delivery system with a hydrodynamic tail vein injection and the Sleeping Beauty transposon. The antitumour effects of Dyrk2 gene transfer were investigated in a murine autologous carcinogenesis model.

Results

Dyrk2 expression was reduced in tumours, and that its downregulation was induced before hepatocarcinogenesis. Dyrk2 gene transfer significantly suppressed carcinogenesis. It also suppresses Myc-induced de-differentiation and metabolic reprogramming, which favours proliferative, and malignant potential by altering gene profiles. Dyrk2 overexpression caused Myc and Hras degradation at the protein level rather than at the mRNA level, and this degradation mechanism was regulated by the proteasome. Immunohistochemical analyses revealed a negative correlation between DYRK2 expression and MYC and longer survival in patients with HCC with high-DYRK2 and low-MYC expressions.

Conclusions

Dyrk2 protects the liver from carcinogenesis by promoting Myc and Hras degradation. Our findings would pave the way for a novel therapeutic approach using DYRK2 gene transfer.

Impact and Implications

Hepatocellular carcinoma (HCC) is one of the most common cancers, with a poor prognosis. Hence, identifying molecules that can become promising targets for therapies is essential to improve mortality. No studies have clarified the association between DYRK2 and carcinogenesis, although DYRK2 is involved in tumour growth in various cancer cells. This is the first study to show that Dyrk2 expression decreases during hepatocarcinogenesis and that Dyrk2 gene transfer is an attractive approach with tumour suppressive activity against HCC by suppressing Myc-mediated de-differentiation and metabolic reprogramming that favours proliferative and malignant potential via Myc and Hras degradation.

Liver lobe-specific hydrodynamic gene delivery to baboons: A preclinical trial for hemophilia gene therapy

Hydrodynamics-based gene transfer has been successfully employed for in vivo gene delivery to the liver of small animals by tail vein injection and of large animals using a computer-assisted and image-guided protocol. In an effort to develop a hydrodynamic gene delivery procedure clinically applicable for gene therapy, we have evaluated the safety and effectiveness of a lobe-specific hydrodynamic delivery procedure for hepatic gene delivery in baboons. Reporter plasmid was used to assess the gene delivery efficiency of the lobe-specific hydrodynamic gene delivery, and plasmid-carrying human factor IX gene was used to examine the pattern of long-term gene expression. The results demonstrated liver lobe-specific gene delivery, therapeutic levels of human factor IX gene expression lasting for >100 days, and the efficacy of repeated hydrodynamic gene delivery into the same liver lobes. Other than a transient increase in blood concentration of liver enzymes right after the injection, no significant adverse events were observed in animals during the study period. The results obtained from this first non-human primate study support the clinical applicability of the procedure for lobe-specific hydrodynamic gene delivery to liver.

Hydrodynamic Delivery: Characteristics, Applications, and Technological Advances

The principle of hydrodynamic delivery was initially used to develop a method for the delivery of plasmids into mouse hepatocytes through tail vein injection and has been expanded for use in the delivery of various biologically active materials to cells in various organs in a variety of animal species through systemic or local injection, resulting in significant advances in new applications and technological development. The development of regional hydrodynamic delivery directly supports successful gene delivery in large animals, including humans. This review summarizes the fundamentals of hydrodynamic delivery and the progress that has been made in its application. Recent progress in this field offers tantalizing prospects for the development of a new generation of technologies for broader application of hydrodynamic delivery.

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.

Intravital electrochemical nanosensor as a tool for the measurement of reactive oxygen/nitrogen species in liver diseases

Reactive oxygen/nitrogen species (ROS/RNS) are formed during normal cellular metabolism and contribute to its regulation, while many pathological processes are associated with ROS/RNS imbalances. Modern methods for measuring ROS/RNS are mainly based on the use of inducible fluorescent dyes and protein-based sensors, which have several disadvantages for in vivo use. Intravital electrochemical nanosensors can be used to quantify ROS/RNS with high sensitivity without exogenous tracers and allow dynamic ROS/RNS measurements in vivo. Here, we developed a method for quantifying total ROS/RNS levels in the liver and evaluated our setup in live mice using three common models of liver disease associated with ROS activation: acute liver injury with CCl4, partial hepatectomy (HE), and induced hepatocellular carcinoma (HCC). We have demonstrated using intravital electrochemical detection that any exposure to the peritoneum in vivo leads to an increase in total ROS/RNS levels, from a slight increase to an explosion, depending on the procedure. Analysis of the total ROS/RNS level in a partial hepatectomy model revealed oxidative stress, both in mice 24 h after HE and in sham-operated mice. We quantified dose-dependent ROS/RNS production in CCl4-induced injury with underlying neutrophil infiltration and cell death. We expect that in vivo electrochemical measurements of reactive oxygen/nitrogen species in the liver may become a routine approach that provides valuable data in research and preclinical studies.

Advances in CRISPR Delivery Methods: Perspectives and Challenges

With the advent of new genome editing technologies and the emphasis placed on their optimization, the genetic and phenotypic correction of a plethora of diseases sit on the horizon. Ideally, genome editing approaches would provide long-term solutions through permanent disease correction instead of simply treating patients symptomatically. Although various editing machinery options exist, the clustered regularly interspaced short palindromic repeats (CRISPR)-Cas (CRISPR-associated protein) editing technique has emerged as the most popular due to its high editing efficiency, simplicity, and affordability. However, while CRISPR technology is gradually being perfected, optimization is futile without accessible, effective, and safe delivery to the desired cell or tissue. Therefore, it is important that scientists simultaneously focus on inventing and improving delivery modalities for editing machinery as well. In this review, we will discuss the critical details of viral and nonviral delivery systems, including payload, immunogenicity, efficacy in delivery, clinical application, and future directions.

CRISPR-Cas9-Based Technology and Its Relevance to Gene Editing in Parkinson's Disease

Parkinson's disease (PD) and other chronic and debilitating neurodegenerative diseases (NDs) impose a substantial medical, emotional, and financial burden on individuals and society. The origin of PD is unknown due to a complex combination of hereditary and environmental risk factors. However, over the last several decades, a significant amount of available data from clinical and experimental studies has implicated neuroinflammation, oxidative stress, dysregulated protein degradation, and mitochondrial dysfunction as the primary causes of PD neurodegeneration. The new gene-editing techniques hold great promise for research and therapy of NDs, such as PD, for which there are currently no effective disease-modifying treatments. As a result, gene therapy may offer new treatment options, transforming our ability to treat this disease. We present a detailed overview of novel gene-editing delivery vehicles, which is essential for their successful implementation in both cutting-edge research and prospective therapeutics. Moreover, we review the most recent advancements in CRISPR-based applications and gene therapies for a better understanding of treating PD. We explore the benefits and drawbacks of using them for a range of gene-editing applications in the brain, emphasizing some fascinating possibilities.

CRISPR somatic genome engineering and cancer modeling in the mouse pancreas and liver

Genetically engineered mouse models (GEMMs) transformed the study of organismal disease phenotypes but are limited by their lengthy generation in embryonic stem cells. Here, we describe methods for rapid and scalable genome engineering in somatic cells of the liver and pancreas through delivery of CRISPR components into living mice. We introduce the spectrum of genetic tools, delineate viral and nonviral CRISPR delivery strategies and describe a series of applications, ranging from gene editing and cancer modeling to chromosome engineering or CRISPR multiplexing and its spatio-temporal control. Beyond experimental design and execution, the protocol describes quantification of genetic and functional editing outcomes, including sequencing approaches, data analysis and interpretation. Compared to traditional knockout mice, somatic GEMMs face an increased risk for mouse-to-mouse variability because of the higher experimental demands of the procedures. The robust protocols described here will help unleash the full potential of somatic genome manipulation. Depending on the delivery method and envisaged application, the protocol takes 3-5 weeks.

Current approaches in CRISPR-Cas9 mediated gene editing for biomedical and therapeutic applications

A single gene mutation can cause a number of human diseases that affect quality of life. Until the development of clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPR-associated protein (Cas) systems, it was challenging to correct a gene mutation to avoid disease by reverting phenotypes. The advent of CRISPR technology has changed the field of gene editing, given its simplicity and intrinsic programmability, surpassing the limitations of both zinc-finger nuclease and transcription activator-like effector nuclease and becoming the method of choice for therapeutic gene editing by overcoming the bottlenecks of conventional gene-editing techniques. Currently, there is no commercially available medicinal cure to correct a gene mutation that corrects and reverses the abnormality of a gene's function. Devising reprogramming strategies for faithful recapitulation of normal phenotypes is a crucial aspect for directing the reprogrammed cells toward clinical trials. The CRISPR-Cas9 system has been promising as a tool for correcting gene mutations in maladies including blood disorders and muscular degeneration as well as neurological, cardiovascular, renal, genetic, stem cell, and optical diseases. In this review, we highlight recent developments and utilization of the CRISPR-Cas9 system in correcting or generating gene mutations to create model organisms to develop deeper insights into diseases, rescue normal gene functionality, and curb the progression of a disease.

Organoids as research models for hepatocellular carcinoma

Organoid culture is an emerging research tool that has proved tremendously useful in a multitude of aspects, one of which is cancer research. They largely overcome the limitations of previous cancer models by their faithful recapitulation of the in vivo biology, while still remaining amenable to perturbations. Using a cocktail of biologicals that mimic the stem cell niche signaling, hepatocellular carcinoma (HCC) organoids could be generated from tissue samples of both human and murine origin. Existing reports show that HCC organoids retain key characteristics of their parental tumor tissue, including the histological architecture, genomic landscape, expression profile and intra-tumor heterogeneity. There is ongoing effort to establish living biobanks of patient-derived cancer organoids, annotated with multi-omics data and clinical data, and they can be particularly valuable in stratification of HCC subtypes, pre-clinical drug discovery and personalized medicine. In the future, efforts in the standardization of procedures and nomenclature, refinement of protocols, as well as engineering of the culture systems will enable scientists to unleash the full potential of organoid technology.

Delivery of synthetic mRNAs for tissue regeneration

In recent years, nucleic acid-based therapeutics have gained increasing importance as novel treatment options for disease prevention and treatment. Synthetic messenger RNAs (mRNAs) are promising nucleic acid-based drugs to transiently express desired proteins that are missing or defective. Recently, synthetic mRNA-based vaccines encoding viral proteins have been approved for emergency use against COVID-19. Various types of vehicles, such as lipid nanoparticles (LNPs) and liposomes, are being investigated to enable the efficient uptake of mRNA molecules into desired cells. In addition, the introduction of novel chemical modifications into mRNAs increased the stability, enabled the modulation of nucleic acid-based drugs, and increased the efficiency of mRNA-based therapeutic approaches. In this review, novel and innovative strategies for the delivery of synthetic mRNA-based therapeutics for tissue regeneration are discussed. Moreover, with this review, we aim to highlight the versatility of synthetic mRNA molecules for various applications in the field of regenerative medicine and also discuss translational challenges and required improvements for mRNA-based drugs.

Modulation of Immune Reaction in Hydrodynamic Gene Therapy for Hemophilia A

Hemophilia A (HA) is a monogenic disease characterized by plasma clotting factor 8 (F8) deficiency due to F8 mutation. We have been attempting to cure HA permanently using a CRISPR-Cas9 gene-editing strategy. Here, we induced targeted integration of BDDF8 (B-domain-deleted F8) gene into the albumin locus of HA mice by hydrodynamic tail vein injection of editing plasmid vectors. One week after treatment, a high F8 activity ranging from 70% to 280% of normal serum levels was observed in all treated HA mice but dropped to background levels 3-5 weeks later. We found that the humoral immune reaction targeting F8 is the predominant cause of the decreased F8 activity. We hypothesized that hydrodynamic injection-induced liver damage triggered the release of large quantities of inflammatory cytokines. However, co-injection of plasmids expressing a dozen immunomodulatory factors failed to curtail the immune reaction and stabilize F8 activity. The spCas9 plasmid carrying a miR-142-3p target sequence alleviated the cellular immune response but was unable to deliver therapeutic efficacy. Strikingly, immunosuppressant cyclo-phosphamide virtually abolished the immune response, leading to a year-long stable F8 level. Our findings should have important implications in developing therapies in mouse models using the hydrodynamic gene delivery approach, highlighting the ne-cessity of modulating the innate immune response triggered by liver damage.

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.

From Pinocytosis to Methuosis-Fluid Consumption as a Risk Factor for Cell Death

The volumes of a cell [cell volume (CV)] and its organelles are adjusted by osmoregulatory processes. During pinocytosis, extracellular fluid volume equivalent to its CV is incorporated within an hour and membrane area equivalent to the cell's surface within 30 min. Since neither fluid uptake nor membrane consumption leads to swelling or shrinkage, cells must be equipped with potent volume regulatory mechanisms. Normally, cells respond to outwardly or inwardly directed osmotic gradients by a volume decrease and increase, respectively, i.e., they shrink or swell but then try to recover their CV. However, when a cell death (CD) pathway is triggered, CV persistently decreases in isotonic conditions in apoptosis and it increases in necrosis. One type of CD associated with cell swelling is due to a dysfunctional pinocytosis. Methuosis, a non-apoptotic CD phenotype, occurs when cells accumulate too much fluid by macropinocytosis. In contrast to functional pinocytosis, in methuosis, macropinosomes neither recycle nor fuse with lysosomes but with each other to form giant vacuoles, which finally cause rupture of the plasma membrane (PM). Understanding methuosis longs for the understanding of the ionic mechanisms of cell volume regulation (CVR) and vesicular volume regulation (VVR). In nascent macropinosomes, ion channels and transporters are derived from the PM. Along trafficking from the PM to the perinuclear area, the equipment of channels and transporters of the vesicle membrane changes by retrieval, addition, and recycling from and back to the PM, causing profound changes in vesicular ion concentrations, acidification, and-most importantly-shrinkage of the macropinosome, which is indispensable for its proper targeting and cargo processing. In this review, we discuss ion and water transport mechanisms with respect to CVR and VVR and with special emphasis on pinocytosis and methuosis. We describe various aspects of the complex mutual interplay between extracellular and intracellular ions and ion gradients, the PM and vesicular membrane, phosphoinositides, monomeric G proteins and their targets, as well as the submembranous cytoskeleton. Our aim is to highlight important cellular mechanisms, components, and processes that may lead to methuotic CD upon their derangement.

Parameters of biliary hydrodynamic injection during endoscopic retrograde cholangio-pancreatography in pigs for applications in gene delivery

The biliary system is routinely accessed for clinical purposes via endoscopic retrograde cholangiopancreatography (ERCP). We previously pioneered ERCP-mediated hydrodynamic injection in large animal models as an innovative gene delivery approach for monogenic liver diseases. However, the procedure poses potential safety concerns related mainly to liver or biliary tree injury. Here, we sought to further define biliary hydrodynamic injection parameters that are well-tolerated in a human-sized animal model. ERCP was performed in pigs, and hydrodynamic injection carried out using a novel protocol to reduce duct wall stress. Each pig was subjected to multiple repeated injections to expedite testing and judge tolerability. Different injection parameters (volume, flow rate) and injection port diameters were tested. Vital signs were monitored throughout the procedure, and liver enzyme panels were collected pre- and post-procedure. Pigs tolerated repeated biliary hydrodynamic injections with only occasional, mild, isolated elevation in aspartate aminotransferase (AST), which returned to normal levels within one day post-injection. All other liver tests remained unchanged. No upper limit of volume tolerance was reached, which suggests the biliary tree can readily transmit fluid into the vascular space. Flow rates up to 10 mL/sec were also tolerated with minimal disturbance to vital signs and no anatomic rupture of bile ducts. Measured intrabiliary pressure was up to 150 mmHg, and fluid-filled vesicles were induced in liver histology at high flow rates, mimicking the changes in histology observed in mouse liver after hydrodynamic tail vein injection. Overall, our investigations in a human-sized pig liver using standard clinical equipment suggest that ERCP-guided hydrodynamic injection will be safely tolerated in patients. Future investigations will interrogate if higher flow rates and pressure mediate higher DNA delivery efficiencies.

Gene and epigenetic editing in the treatment of primary ciliopathies

Primary ciliopathies are inherited human disorders that arise from mutations in ciliary genes. They represent a spectrum of severe, incurable phenotypes, differentially involving several organs, including the kidney and the eye. The development of gene-based therapies is opening up new avenues for the treatment of ciliopathies. Particularly attractive is the possibility of correcting in situ the causative genetic mutation, or pathological epigenetic changes, through the use of gene editing tools. Due to their versatility and efficacy, CRISPR/Cas-based systems represent the most promising gene editing toolkit for clinical applications. However, delivery and specificity issues have so far held back the translatability of CRISPR/Cas-based therapies into clinical practice, especially where systemic administration is required. The eye, with its characteristics of high accessibility and compartmentalization, represents an ideal target for in situ gene correction. Indeed, studies for the evaluation of a CRISPR/Cas-based therapy for in vivo gene correction to treat a retinal ciliopathy have reached the clinical stage. Further technological advances may be required for the development of in vivo CRISPR-based treatments for the kidney. We discuss here the possibilities and the challenges associated to the implementation of CRISPR/Cas-based therapies for the treatment of primary ciliopathies with renal and retinal phenotypes.

Proliferative polyploid cells give rise to tumors via ploidy reduction

Polyploidy is a hallmark of cancer, and closely related to chromosomal instability involved in cancer progression. Importantly, polyploid cells also exist in some normal tissues. Polyploid hepatocytes proliferate and dynamically reduce their ploidy during liver regeneration. This raises the question whether proliferating polyploids are prone to cancer via chromosome missegregation during mitosis and/or ploidy reduction. Conversely polyploids could be resistant to tumor development due to their redundant genomes. Therefore, the tumor-initiation risk of physiologic polyploidy and ploidy reduction is still unclear. Using in vivo lineage tracing we here show that polyploid hepatocytes readily form liver tumors via frequent ploidy reduction. Polyploid hepatocytes give rise to regenerative nodules with chromosome aberrations, which are enhanced by ploidy reduction. Although polyploidy should theoretically prevent tumor suppressor loss, the high frequency of ploidy reduction negates this protection. Importantly, polyploid hepatocytes that undergo multiple rounds of cell division become predominantly mononucleated and are resistant to ploidy reduction. Our results suggest that ploidy reduction is an early step in the initiation of carcinogenesis from polyploid hepatocytes.

Delivery Approaches for Therapeutic Genome Editing and Challenges

Impressive therapeutic advances have been possible through the advent of zinc-finger nucleases and transcription activator-like effector nucleases. However, discovery of the more efficient and highly tailorable clustered regularly interspaced short palindromic repeats (CRISPR) and associated proteins (Cas9) has provided unprecedented gene-editing capabilities for treatment of various inherited and acquired diseases. Despite recent clinical trials, a major barrier for therapeutic gene editing is the absence of safe and effective methods for local and systemic delivery of gene-editing reagents. In this review, we elaborate on the challenges and provide practical considerations for improving gene editing. Specifically, we highlight issues associated with delivery of gene-editing tools into clinically relevant cells.

Somatic Liver Knockout (SLiK): A Quick and Efficient Way to Generate Liver-Specific Knockout Mice Using Multiplex CRISPR/Cas9 Gene Editing

Somatic liver knockout (SLiK) is a method developed to rapidly generate a liver-specific knockout of one or several genes. This technique combines the strengths of CRISPR/Cas9 gene editing and hydrodynamic tail-vein injection, a simple in vivo method for transfection of hepatocytes, to harness the powerful selection pressure of tyrosinemic livers to replace host hepatocytes with any desired gene deletion. In this protocol, we will describe sgRNA design and cloning, hydrodynamic tail-vein injection of targeting constructs, and screening and validation methods for efficient in vivo gene editing. © 2020 by John Wiley & Sons, Inc. Support Protocol 1: sgRNA design Support Protocol 2: sgRNA construction: daisy chaining multiple sgRNAs Basic Protocol: Delivery of DNA by hydrodynamic tail-vein injection and liver repopulation of edited hepatocytes Support Protocol 3: Validation of CRISPR/Cas9 cutting in vivo.

Tissue suction-mediated gene transfer to the beating heart in mice

We previously developed an in vivo site-specific transfection method using a suction device in mice; namely, a tissue suction-mediated transfection method (tissue suction method). The aim of this study was to apply the tissue suction method for cardiac gene transfer. Naked plasmid DNA (pDNA) was intravenously injected in mice, followed by direct suction on the beating heart by using a suction device made of polydimethylsiloxane. We first examined the effects of suction conditions on transgene expression and toxicity. Subsequently, we analyzed transgene-expressing cells and the transfected region of the heart. We found that heart suction induced transgene expression, and that −75 kPa and −90 kPa of suction achieved high transgene expression. In addition, the inner diameter of the suction device was correlated with transgene expression, but the pressure hold time did not change transgene expression. Although the tissue suction method at −75 kPa induced a transient increase in the serum cardiac toxicity markers at 6 h after transfection, these markers returned to normal at 24 h. The cardiac damage was also analyzed through the measurement of hypertrophic gene expression, but no significant differences were found. In addition, the cardiac function monitored by echocardiography remained normal at 11 days after transfection. Immunohistochemical analysis revealed that CD31-positive endothelial cells co-expressed the ZsGreen1-N1 reporter gene. In conclusion, the tissue suction method can achieve an efficient and safe gene transfer to the beating heart in mice.

Liver gene transfection by retrograde intrabiliary infusion facilitated by temporary biliary obstruction

BACKGROUND

The hepatobiliary tract may be a valuable administration site for gene delivery. We demonstrated the role of temporary biliary obstruction for gene transfection by retrograde intrabiliary infusion.

METHODS

Male Sprague-Dawley rats received intrabiliary infusion of luciferase plasmid via an artificial common bile duct, with temporary biliary obstruction for 0 minutes (NO group), 30 minutes (30 min group) and 24 hours (24 h group), respectively (n = 4 for each group). Gene expression levels were evaluated by luciferase bioluminescence on postoperative days (POD) 1, 2 and 7. Serum and livers were collected on POD 1 and 14 for liver biochemistry, hematoxylin and eosin staining, and immunohistochemistry.

RESULTS

On POD 1, luciferase chemoluminescence was significantly higher in the 24 h group than in the NO group (p = 0.002) and the 30 min group (p = 0.002). However, it decreased rapidly after reversal of the obstruction in the 24 h group (POD 1 versus POD 2, p = 0.002; POD 1 versus POD 7, p = 0.002). Liver biochemistry was changed on POD 1, but no significant differences were detected after 14 days of recovery (p > 0.05). Similar histological changes were found in the three groups, with no unwanted proliferation of biliary epithelial cells. The obstruction did not cause serious liver damage.

CONCLUSIONS

Temporary biliary obstruction for 24 hours facilitated the safe, feasible and effective transfection of plasmid DNA into the liver via the hepatobiliary tract. In the future, endoscopic retrograde cholangiopancreatography and its dilation balloon could be used to create biliary obstruction and allow the direct gene delivery into the liver. More research is necessary for achieving stable gene expression, as well as in terms of weighing its benefits against potential complications.

Treatment of Cystathionine β-Synthase Deficiency in Mice Using a Minicircle-Based Naked DNA Vector

Cystathionine β-synthase (CBS) deficiency is a recessive inborn error of metabolism characterized by extremely elevated total homocysteine (tHcy) in the blood. Patients diagnosed with CBS deficiency have a variety of clinical problems, including dislocated lenses, osteoporosis, cognitive and behavioral issues, and a significantly increased risk of thrombosis. Current treatment strategies involve a combination of vitamin supplementation and restriction of foods containing the homocysteine precursor methionine. Here, a mouse model for CBS deficiency (Tg-I278T Cbs-/-) was used to evaluate the potential of minicircle-based naked DNA gene therapy to treat CBS deficiency. A 2.3 kb DNA-minicircle containing the liver-specific P3 promoter driving the human CBS cDNA (MC.P3-hCBS) was delivered into Tg-I278T Cbs-/- mice via a single hydrodynamic tail vein injection. Mean serum tHcy decreased from 351 μM before injection to 176 μM 7 days after injection (p = 0.0005), and remained decreased for at least 42 days. Western blot analysis reveals significant minicircle-directed CBS expression in the liver tissue. Liver CBS activity increased 34-fold (12.8 vs. 432 units; p = 0.0004) in MC.P3-hCBS-injected animals. Injection of MC.P3-hCBS in young mice, subsequently followed for 202 days, showed that the vector can ameliorate the mouse homocystinuria alopecia phenotype. The present findings show that minicircle-based gene therapy can lower tHcy in a mouse model of CBS deficiency.

Identification of Factors Complicating Bioluminescence Imaging

In vivo bioluminescence imaging (BLI) has become a standard, non-invasive imaging modality for following gene expression or the fate of proteins and cells in living animals. Currently, bioluminescent reporters used in laboratories are mostly derivatives of two major luciferase families: ATP-dependent insect luciferases and ATP-independent marine luciferases. Inconsistent results of experiments using different bioluminescent reporters, such as Akaluc and Antareas2, have been reported. Herein, we re-examined the inconsistency in several experimental settings and identified the factors, such as ATP dependency, stability in serum, and molecular sizes of luciferases, that contributed to the observed differences. We expect this study will make the research community aware of these factors and facilitate more accurate interpretation of BLI data by considering the nature of each bioluminescent reporter.

Delivering CRISPR: a review of the challenges and approaches

Gene therapy has long held promise to correct a variety of human diseases and defects. Discovery of the Clustered Regularly-Interspaced Short Palindromic Repeats (CRISPR), the mechanism of the CRISPR-based prokaryotic adaptive immune system (CRISPR-associated system, Cas), and its repurposing into a potent gene editing tool has revolutionized the field of molecular biology and generated excitement for new and improved gene therapies. Additionally, the simplicity and flexibility of the CRISPR/Cas9 site-specific nuclease system has led to its widespread use in many biological research areas including development of model cell lines, discovering mechanisms of disease, identifying disease targets, development of transgene animals and plants, and transcriptional modulation. In this review, we present the brief history and basic mechanisms of the CRISPR/Cas9 system and its predecessors (ZFNs and TALENs), lessons learned from past human gene therapy efforts, and recent modifications of CRISPR/Cas9 to provide functions beyond gene editing. We introduce several factors that influence CRISPR/Cas9 efficacy which must be addressed before effective in vivo human gene therapy can be realized. The focus then turns to the most difficult barrier to potential in vivo use of CRISPR/Cas9, delivery. We detail the various cargos and delivery vehicles reported for CRISPR/Cas9, including physical delivery methods (e.g. microinjection; electroporation), viral delivery methods (e.g. adeno-associated virus (AAV); full-sized adenovirus and lentivirus), and non-viral delivery methods (e.g. liposomes; polyplexes; gold particles), and discuss their relative merits. We also examine several technologies that, while not currently reported for CRISPR/Cas9 delivery, appear to have promise in this field. The therapeutic potential of CRISPR/Cas9 is vast and will only increase as the technology and its delivery improves.

Determining Transgene Expression Characteristics Using a Suction Device with Multiple Hole Adjusting a Left Lateral Lobe of the Mouse Liver

We developed a tissue suction-mediated transfection method (suction method) as a relatively reliable and less invasive technique for in vivo transfection. In this study, we determined hepatic transgene expression characteristics in the mouse liver, using a suction device, collecting information relevant to gene therapy and gene functional analysis by the liver suction method. To achieve high transgene expression levels, we developed a suction device with four holes (multiple hole device) and applied it to the larger portion of the left lateral lobe of the mouse liver. Hepatic transfection with physical stimuli was potentially controlled by activator protein-1 (AP-1) and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB). We examined the spatial distribution of transgene expression in the suctioned lobe by 2-dimensional imaging with histochemical staining and 3-dimensional multicolor deep imaging with tissue clearing methods. Through monitoring spatial distribution of transgene expression, the liver suction method was used to efficiently transfect extravascular hepatocytes in the suction-deformable upper lobe of the liver. Moreover, long-term transgene expression, at least 14 d, was achieved with the liver suction method when cytosine-phosphate-guanine (CpG)-free plasmid DNA was applied.

Improved Lentiviral Gene Delivery to Mouse Liver by Hydrodynamic Vector Injection through Tail Vein

Delivery of genes to mouse liver is routinely accomplished by tail-vein injections of viral vectors or naked plasmid DNA. While viral vectors are typically injected in a low-pressure and -volume fashion, uptake of naked plasmid DNA to hepatocytes is facilitated by high pressure and volumes, also known as hydrodynamic delivery. In this study, we compare the efficacy and specificity of delivery of vesicular stomatitis virus G glycoprotein (VSV-G) pseudotyped lentiviral vectors to mouse liver by a number of injection schemes. Exploiting in vivo bioluminescence imaging as a readout after lentiviral gene transfer, we compare delivery by (1) “conventional” tail-vein injections, (2) “primed” injections, (3) “hydrodynamic” injections, or (4) direct “intrahepatic” injections into exposed livers. Reporter gene activity demonstrate potent and targeted delivery to liver by hydrodynamic injections. Enhanced efficacy is confirmed by analysis of liver sections from mice treated with GFP-encoding vectors, demonstrating 10-fold higher transduction rates and gene delivery to ∼80% of hepatocytes after hydrodynamic vector delivery. In summary, lentiviral vector transfer to mouse liver can be strongly augmented by hydrodynamic tail-vein injections, resulting in both reduced off-target delivery and transduction of the majority of hepatocytes. Our findings pave the way for more effective use of lentiviral gene delivery in the mouse.

Hydrodynamic Renal Pelvis Injection for Non-viral Expression of Proteins in the Kidney

Hydrodynamic injection creates a local, high-pressure environment to transfect various tissues with plasmid DNA and other substances. Hydrodynamic tail vein injection, for example, is a well-established method by which the liver can be transfected. This manuscript describes an application of hydrodynamic principles by injection of the mouse kidney directly with plasmid DNA for kidney-specific gene expression. Mice are anesthetized and the kidney is exposed by a flank incision followed by a fast injection of a plasmid DNA-containing solution directly into the renal pelvis. The needle is kept in place for ten seconds and the incision site is sutured. The following day, live animal imaging, Western blot, or immunohistochemistry may be used to assay gene expression, or other assays suited to the transgene of choice are used for detection of the protein of interest. Published methods to prolong gene expression include transposon-mediated transgene integration and cyclophosphamide treatment to inhibit the immune response to the transgene.

Easi-CRISPR for creating knock-in and conditional knockout mouse models using long ssDNA donors

CRISPR/Cas9-based genome editing can easily generate knockout mouse models by disrupting the gene sequence, but its efficiency for creating models that require either insertion of exogenous DNA (knock-in) or replacement of genomic segments is very poor. The majority of mouse models used in research involve knock-in (reporters or recombinases) or gene replacement (e.g., conditional knockout alleles containing exons flanked by LoxP sites). A few methods for creating such models have been reported that use double-stranded DNA as donors, but their efficiency is typically 1-10% and therefore not suitable for routine use. We recently demonstrated that long single-stranded DNAs (ssDNAs) serve as very efficient donors, both for insertion and for gene replacement. We call this method efficient additions with ssDNA inserts-CRISPR (Easi-CRISPR) because it is a highly efficient technology (efficiency is typically 30-60% and reaches as high as 100% in some cases). The protocol takes ∼2 months to generate the founder mice.

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.

Suppression of GRK2 expression reduces endothelial dysfunction by restoring glucose homeostasis

Despite the associations between diabetic complications and vascular endothelial dysfunction, a direct therapeutic method targeting endothelial dysfunction remains poorly characterized. We have previously shown that chemical inhibition of G-protein-coupled receptor kinase 2 (GRK2) slightly enhances insulin sensitivity and reduces endothelial dysfunction in type 2 diabetic mice. In this study, we identified GRK2 as a novel therapeutic target of diabetic endothelial dysfunction and investigated the effect on diabetic endothelial dysfunction through the systemic administration of GRK2 siRNA using a hydrodynamic-based procedure, resulting in suppression of increased GRK2 protein levels in the liver. Suppressed GRK2 levels in the liver markedly improved glucose homeostasis, as well as improved the impaired endothelial Akt/eNOS-dependent signal activation (insulin-stimulated phosphorylation of Akt and eNOS) and vascular responses (clonidine-induced and insulin-induced endothelial-dependent relaxation response and phenylephrine-induced contractile response) in type 2 diabetic aortas. Interestingly, insulin-stimulated Akt/eNOS signaling was increased only by normalizing the glucose concentration in human umbilical vein endothelial cells (HUVECs) with GRK2 overexpression, suggesting of an important role of hepatic GRK2. Our results clarified the relationship among hepatic GRK2, glucose homeostasis, and vascular endothelial function. Liver-targeting GRK2 siRNA delivery represents a novel therapeutic tool to restore glucose homeostasis and reduce endothelial dysfunction.

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.

Feasibility of the functional expression of the human organic anion transporting polypeptide 1B1 (OATP1B1) and its genetic variant 521T/C in the mouse liver

The objective of this study was to examine the feasibility of functional expression of the human organic anion transporting polypeptide 1B1 (hOATP1B1) forms in the liver of the mouse. After the mouse received the gene of interest (i.e., luciferase as the reporter or hOATP1B1) via hydrodynamic gene delivery (HGD) method, the expression was found to be liver-specific while alterations in the serum biochemistry and hepatocyte histology were apparently transient and reversible. The reporter activity was also detected in the plasma, but not in the blood cell in mice that received HGD, suggesting that the protein is probably released due to transiently increased permeability in hepatocytes by HGD. Using this delivery condition, the expression of hOATP1B1 was readily detected in the liver, but not in other tissues, of the mice receiving HGD for the transporter gene. Compared with the sham control mice, the uptake of pravastatin into the liver increased significantly in mice receiving hOATP1B1 wild type; the uptake parameters decreased consistently in mice expressing the 521T>C variant compared with that of the wild type control. These observations suggest that the functional expression of human transporter gene in mice is feasible, further suggesting that this treatment is practically useful in the pharmacokinetic studies for hOATP1B1 substrates.

Hydrodynamic HBV Transfection Mouse Model

Hydrodynamic HBV transfection mouse model is an established method of the last decade where macromolecules, non-normally permeable to cell membrane, are delivered intracellular. The basic principle is that a large volume of solution, containing HBV plasmid construct, is infused rapidly in circulation to permit the preferential entrance of these macromolecules to liver parenchymal cells. The aim of this chapter is to describe the basic principles of the hydrodynamic HBV transfection in mouse models.

Episomal Nonviral Gene Therapy Vectors Slow Progression of Atherosclerosis in a Model of Familial Hypercholesterolemia

Familial hypercholesterolemia (FH) is a life-threatening genetic disorder characterized by elevated levels of plasma low-density lipoprotein cholesterol (LDL-cholesterol). Current attempts at gene therapy for FH have been limited by the use of strong heterologous promoters which lack genomic DNA elements essential for regulated expression. Here, we have combined a mini-gene vector expressing the human LDLR cDNA from a 10 kb native human LDLR locus genomic DNA promoter element, with an efficient miRNA targeting 3-hydroxy-3-methylgutaryl-coenzyme A reductase (Hmgcr), to further enhance LDLR expression. We show that the combined vector suppresses endogenous Hmgcr transcripts in vivo, leading to an increase in LDLR transgene expression. In a diet-induced Ldlr^-/- mouse model of FH, we show that administration of the combined vector reduces atherogenic plasma lipids by ~32%. Finally, we demonstrate that our episomal nonviral vectors are able to reduce atherosclerosis by ~40% after 12 weeks in vivo. Taken together, the vector system we describe exploits the normal cellular regulation of the LDLR to provide prolonged expression of LDLR through targeted knockdown of Hmgcr. This novel gene therapy system could act alone, or in synergy with current therapies that modulate intracellular cholesterol, such as statins, greatly enhancing its therapeutic application for FH.

Liver-targeted hydrodynamic gene therapy: Recent advances in the technique

One of the major research focuses in the field of gene therapy is the development of clinically applicable, safe, and effective gene-delivery methods. Since the first case of human gene therapy was performed in 1990, a number of gene-delivery methods have been developed, evaluated for efficacy and safety, and modified for human application. To date, viral-vector-mediated deliveries have shown effective therapeutic results. However, the risk of lethal immune response and carcinogenesis have been reported, and it is still controversial to be applied as a standard therapeutic option. On the other hand, delivery methods for nonviral vector systems have been developed, extensively studied, and utilized in in vivo gene-transfer studies. Compared to viral-vector mediated gene transfer, nonviral systems have less risk of biological reactions. However, the lower gene-transfer efficiency was a critical hurdle for applying them to human gene therapy. Among a number of nonviral vector systems, our studies focus on hydrodynamic gene delivery to utilize physical force to deliver naked DNA into the cells in the living animals. This method achieves a high gene-transfer level by DNA solution injections into the tail vein of rodents, especially in the liver. With the development of genome editing methods, in vivo gene-transfer therapy using this method is currently the focus in this research field. This review explains the method principle, efficiency, safety, and procedural modifications to achieve a high level of reproducibility in large-animal models.

Studying Closed Hydrodynamic Models of "In Vivo" DNA Perfusion in Pig Liver for Gene Therapy Translation to Humans

INTRODUCTION

Expressing exogenous genes after naked DNA delivery into hepatocytes might achieve sustained and high expression of human proteins. Tail vein DNA injection is an efficient procedure for gene transfer in murine liver. Hydrodynamic procedures in large animals require organ targeting, and improve with liver vascular exclusion. In the present study, two closed liver hydrofection models employing the human alpha-1-antitrypsin (hAAT) gene are compared to reference standards in order to evaluate their potential clinical interest.

MATERIAL AND METHODS

A solution of naked DNA bearing the hAAT gene was retrogradely injected in 7 pig livers using two different closed perfusion procedures: an endovascular catheterization-mediated procedure (n = 3) with infrahepatic inferior vena cava and portal vein blockage; and a surgery-mediated procedure (n = 4) with completely sealed liver. Gene transfer was performed through the suprahepatic inferior cava vein in the endovascular procedure and through the infrahepatic inferior vena cava in the surgical procedure. The efficiency of the procedures was evaluated 14 days after hydrofection by quantifying the hAAT protein copies per cell in tissue and in plasma. For comparison, samples from mice (n = 7) successfully hydrofected with hAAT and healthy human liver segments (n = 4) were evaluated.

RESULTS

Gene decoding occurs efficiently using both procedures, with liver vascular arrest improving its efficiency. The surgically closed procedure (sealed organ) reached higher tissue protein levels (4x10^5- copies/cell) than the endovascular procedure, though the levels were lower than in human liver (5x10^6- copies/cell) and hydrofected mouse liver (10^6- copies/cell). However, protein levels in plasma were lower (p<0.001) than the reference standards in all cases.

CONCLUSION

Hydrofection of hAAT DNA to "in vivo" isolated pig liver mediates highly efficient gene delivery and protein expression in tissue. Both endovascular and surgically closed models mediate high tissue protein expression. Impairment of protein secretion to plasma is observed and might be species-related. This study reinforces the potential application of closed liver hydrofection for therapeutic purposes, provided protein secretion improves.

LTβR signalling preferentially accelerates oncogenic AKT-initiated liver tumours

OBJECTIVES

The relative contributions of inflammatory signalling and sequential oncogenic dysregulation driving liver cancer pathogenesis remain incompletely understood. Lymphotoxin-β receptor (LTβR) signalling is critically involved in hepatitis and liver tumorigenesis. Therefore, we explored the interdependence of inflammatory lymphotoxin signalling and specific oncogenic pathways in the progression of hepatic cancer.

DESIGN

Pathologically distinct liver tumours were initiated by hydrodynamic transfection of oncogenic V-Akt Murine Thymoma Viral Oncogene Homolog 1 (AKT)/β-catenin or AKT/Notch expressing plasmids. To investigate the relationship of LTβR signalling and specific oncogenic pathways, LTβR antagonist (LTβR-Fc) or agonist (anti-LTβR) were administered post oncogene transfection. Initiated livers/tumours were investigated for changes in oncogene expression, tumour proliferation, progression, latency and pathology. Moreover, specific LTβR-mediated molecular events were investigated in human liver cancer cell lines and through transcriptional analyses of samples from patients with intrahepatic cholangiocarcinoma (ICC).

RESULTS

AKT/β-catenin-transfected livers displayed increased expression of LTβ and LTβR, with antagonism of LTβR signalling reducing tumour progression and enhancing survival. Conversely, enforced LTβR-activation of AKT/β-catenin-initiated tumours induced robust increases in proliferation and progression of hepatic tumour phenotypes in an AKT-dependent manner. LTβR-activation also rapidly accelerated ICC progression initiated by AKT/Notch, but not Notch alone. Moreover, LTβR-accelerated development coincides with increases of Notch, Hes1, c-MYC, pAKT and β-catenin. We further demonstrate LTβR signalling in human liver cancer cell lines to be a regulator of Notch, pAKTser473 and β-catenin. Transcriptome analysis of samples from patients with ICC links increased LTβR network expression with poor patient survival, increased Notch1 expression and Notch and AKT/PI3K signalling.

CONCLUSIONS

Our findings link LTβR and oncogenic AKT signalling in the development of ICC.

Potential for cellular stress response to hepatic factor VIII expression from AAV vector

Hemophilia A and B are coagulation disorders resulting from the loss of functional coagulation factor VIII (FVIII) or factor IX proteins, respectively. Gene therapy for hemophilia with adeno-associated virus vectors has shown efficacy in hemophilia B patients. Although hemophilia A patients are more prevalent, the development of therapeutic adeno-associated virus vectors has been impeded by the size of the F8 cDNA and impaired secretion of FVIII protein. Further, it has been reported that over-expression of the FVIII protein induces endoplasmic reticulum stress and activates the unfolded protein response pathway both in vitro and in hepatocytes in vivo, presumably due to retention of misfolded FVIII protein within the endoplasmic reticulum. Engineering of the F8 transgene, including removal of the B domain (BDD-FVIII) and codon optimization, now allows for the generation of adeno-associated virus vectors capable of expressing therapeutic levels of FVIII. Here we sought to determine if the risks of inducing the unfolded protein response in murine hepatocytes extend to adeno-associated virus gene transfer. Although our data show a mild activation of unfolded protein response markers following F8 gene delivery at a certain vector dose in C57BL/6 mice, it was not augmented upon further elevated dosing, did not induce liver pathology or apoptosis, and did not impact FVIII immunogenicity.

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.