Hydrodynamic delivery

Synthetic nanoparticles for the delivery of CRISPR/Cas9 gene editing system: classification and biomedical applications

Gene editing has great potential in biomedical research including disease diagnosis and treatment. Clustered regularly interspaced short palindromic repeats (CRISPR) is the most straightforward and cost-effective method. The efficient and precise delivery of CRISPR can impact the specificity and efficacy of gene editing. In recent years, synthetic nanoparticles have been discovered as effective CRISPR/Cas9 delivery vehicles. We categorized synthetic nanoparticles for CRISPR/Cas9 delivery and discribed their advantages and disadvantages. Further, the building blocks of different kinds of nanoparticles and their applications in cells/tissues, cancer and other diseases were described in detail. Finally, the challenges encountered in the clinical application of CRISPR/Cas9 delivery materials were discussed, and potential solutions were provided regarding efficiency and biosafety issues.

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.

Development and characterization of a chronic hepatitis B murine model with a mutation in the START codon of an HBV polymerase

Chronic hepatitis B (CHB) is caused by the Hepatitis B virus (HBV) and affects millions of people worldwide. Developing an effective CHB therapy requires using in vivo screening methods, such as mouse models reflecting CHB based on hydrodynamic delivery of plasmid vectors containing a replication-competent HBV genome. However, long-term expression of HBV proteins is accompanied by production of progeny virions, thereby requiring a Biosafety Level (BSL) 3 animal facility. In the present study, we introduced a point mutation in the START codon of the HBV polymerase to develop a mouse model reflecting chronic hepatitis B infection without formation of viral progeny. We induced the mouse model by hydrodynamic injection of adeno-associated virus plasmid vector (pAAV) and minicircle plasmid (pMC) constructs into C57Bl/6 and C3H/HeN mouse strains, monitoring HBV antigens and antibodies in blood by enzyme-linked immunosorbent assay and analyzing liver expression of HBV core antigen by immunohistology. Persisting expression of viral antigens over 140 days (study endpoint) was observed only in the C3H/HeN mouse strain when using pAAV/1.2HBV-A and pMC/1.0HBV-D with pre-C and pre-S recombination sites. In addition, pAAV/1.2HBV-A in C3H/HeN sustained HBV core antigen positivity up to the study endpoint in C3H/HeN mice. Moreover, introducing the point mutation in the START codon of polymerase effectively prevented the formation of viral progeny. Our study establishes an accessible and affordable experimental paradigm for developing a robust mouse model reflecting CHB suitable for preclinical testing of anti-HBV therapeutics in a BSL2 animal facility.

Recessive, gain-of-function toxicity in an APOL1 BAC transgenic mouse model mirrors human APOL1 kidney disease

People of recent sub-Saharan African ancestry develop kidney failure much more frequently than other groups. A large fraction of this disparity is due to two coding sequence variants in the APOL1 gene. Inheriting two copies of these APOL1 risk variants, known as G1 and G2, causes high rates of focal segmental glomerulosclerosis (FSGS), HIV-associated nephropathy and hypertension-associated end-stage kidney disease. Disease risk follows a recessive mode of inheritance, which is puzzling given the considerable data that G1 and G2 are toxic gain-of-function variants. We developed coisogenic bacterial artificial chromosome (BAC) transgenic mice harboring either the wild-type (G0), G1 or G2 forms of human APOL1. Expression of interferon gamma (IFN-γ) via plasmid tail vein injection results in upregulation of APOL1 protein levels together with robust induction of heavy proteinuria and glomerulosclerosis in G1/G1 and G2/G2 but not G0/G0 mice. The disease phenotype was greater in G2/G2 mice. Neither heterozygous (G1/G0 or G2/G0) risk variant mice nor hemizygous (G1/-, G2/-) mice had significant kidney injury in response to IFN-γ, although the heterozygous mice had a greater proteinuric response than the hemizygous mice, suggesting that the lack of significant disease in humans heterozygous for G1 or G2 is not due to G0 rescue of G1 or G2 toxicity. Studies using additional mice (multicopy G2 and a non-isogenic G0 mouse) supported the notion that disease is largely a function of the level of risk variant APOL1 expression. Together, these findings shed light on the recessive nature of APOL1-nephropathy and present an important model for future studies.

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.

Development of Novel Heparin/Protamine Nanoparticles Useful for Delivery of Exogenous Proteins In Vitro and In Vivo

We previously reported that heparin/protamine particles (LHPPs) produced as nanoparticles through simple mixing of raw materials exhibit sustained protein release and can be retained in cells. In the present study, we modified LHPPs without employing any organic synthetic approach. The resulting LHPPs were re-named as improved LHPPs (i-LHPPs) and have the ability to retain cell-penetrating peptides (GRKKRRQRRRPPQ) based on electrostatic interactions. We examined whether i-LHPPs can introduce exogenous proteins (i.e., lacZ protein encoding bacterial β-galactosidase) into cultured cells in vitro, or into murine hepatocytes in vivo through intravenous injection to anesthetized mice. We found an accumulation of the transferred protein in both in vitro cultured cells and in vivo hepatocytes. To the best of our knowledge, reports of successful in vivo delivery to hepatocytes are rare. The i-LHPP-based protein delivery technique will be useful for in vivo functional genetic modification of mouse hepatocytes using Cas9 protein-mediated genome editing targeting specific genes, leading to the creation of hepatic disease animal models for research that aims to treat liver diseases.

Application of Various Delivery Methods for CRISPR/dCas9

As gene-editing technology has become more and more popular in the life sciences, CRISPR has brought good news to scientific researchers because of its efficiency, convenience, and wide application. Its wide application has also promoted the development of basic scientific research, agriculture, basic medicine, and clinical treatment. However, how the CRISPR/dCas9 system is effectively delivered to the target organs or cells is still unknown. This paper briefly introduces the CRISPR/dCas9 system and then lists some common delivery methods and their characteristics.

Transplacental Gene Delivery (TPGD) as a Noninvasive Tool for Fetal Gene Manipulation in Mice

Transplacental gene delivery (TPGD) is a technique for delivering nucleic acids to fetal tissues via tail-vein injections in pregnant mice. After transplacental transport, administered nucleic acids enter fetal circulation and are distributed among fetal tissues. TPGD was established in 1995 by Tsukamoto et al., and its mechanisms, and potential applications have been further characterized since. Recently, discoveries of sequence specific nucleases, such as zinc-finger nuclease (ZFN), transcription activator-like effector nucleases (TALEN), and clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein-9 nuclease (Cas9) (CRISPR/Cas9), have revolutionized genome editing. In 2019, we demonstrated that intravenous injection of plasmid DNA containing CRISPR/Cas9 produced indels in fetal myocardial cells, which are comparatively amenable to transfection with exogenous DNA. In the future, this unique technique will allow manipulation of fetal cell functions in basic studies of fetal gene therapy. In this review, we describe developments of TPGD and discuss their applications to the manipulation of fetal cells.

Therapeutic potential of adenovirus-mediated TFF2-CTP-Flag peptide for treatment of colorectal cancer

TFF2 is a small, secreted protein with anti-inflammatory properties. We previously have shown that TFF2 gene delivery via adenovirus (Ad-Tff2) suppresses colon tumor growth in colitis associated cancer. Therefore, systemic administration of TFF2 peptide could potentially provide a similar benefit. Because TFF2 shows a poor pharmacokinetic, we sought to modify the TFF2 peptide in a manner that would lower its clearance rate but retain bioactivity. Given the absence of a sequence-based prediction of TFF2 functionality, we chose to genetically fuse the C-terminus of TFF2 with the carboxyl-terminal peptide of human chorionic gonadotropin β subunit, and inserted into adenoviral vector that expresses Flag. The resulting Ad-Tff2-CTP-Flag construct translates into a TFF2 fused with two CTP and three Flag motifs. Administered Ad-Tff2-CTP-Flag decreased tumorigenesis and suppressed the expansion of myeloid cells in vivo. The fusion peptide TFF2-CTP-Flag delivered by adenovirus Ad-Tff2-CTP-Flag as well purified recombinant fusion TFF2-CTP-Flag was retained in the blood longer compared with wild-type TFF2 delivered by Ad-Tff2 or recombinant TFF2. Consistently, purified recombinant fusion TFF2-CTP-Flag suppressed expansion of myeloid cells by down-regulating cyclin D1 mRNA in vitro. Here, we demonstrate for the very first time the retained bioactivity and possible pharmacokinetic advantages of TFF2 with a modified C-terminus.

Delivery strategies of the CRISPR-Cas9 gene-editing system for therapeutic applications

The CRISPR-Cas9 genome-editing system is a part of the adaptive immune system in archaea and bacteria to defend against invasive nucleic acids from phages and plasmids. The single guide RNA (sgRNA) of the system recognizes its target sequence in the genome, and the Cas9 nuclease of the system acts as a pair of scissors to cleave the double strands of DNA. Since its discovery, CRISPR-Cas9 has become the most robust platform for genome engineering in eukaryotic cells. Recently, the CRISPR-Cas9 system has triggered enormous interest in therapeutic applications. CRISPR-Cas9 can be applied to correct disease-causing gene mutations or engineer T cells for cancer immunotherapy. The first clinical trial using the CRISPR-Cas9 technology was conducted in 2016. Despite the great promise of the CRISPR-Cas9 technology, several challenges remain to be tackled before its successful applications for human patients. The greatest challenge is the safe and efficient delivery of the CRISPR-Cas9 genome-editing system to target cells in human body. In this review, we will introduce the molecular mechanism and different strategies to edit genes using the CRISPR-Cas9 system. We will then highlight the current systems that have been developed to deliver CRISPR-Cas9 in vitro and in vivo for various therapeutic purposes.

Prolonged Expression of Secreted Enzymes in Dogs After Liver-Directed Delivery of Sleeping Beauty Transposons: Implications for Non-Viral Gene Therapy of Systemic Disease

The non-viral, integrating Sleeping Beauty (SB) transposon system is efficient in treating systemic monogenic disease in mice, including hemophilia A and B caused by deficiency of blood clotting factors and mucopolysaccharidosis types I and VII caused by α-L-iduronidase (IDUA) and β-glucuronidase (GUSB) deficiency, respectively. Modified approaches of the hydrodynamics-based procedure to deliver transposons to the liver in dogs were recently reported. Using the transgenic canine reporter secreted alkaline phosphatase (cSEAP), transgenic protein in the plasma was demonstrated for up to 6 weeks post infusion. This study reports that immunosuppression of dogs with gadolinium chloride (GdCl₃) prolonged the presence of cSEAP in the circulation up to 5.5 months after a single vector infusion. Transgene expression declined gradually but appeared to stabilize after about 2 months at approximately fourfold baseline level. Durability of transgenic protein expression in the plasma was inversely associated with transient increase of liver enzymes alanine transaminase and aspartate transaminase in response to the plasmid delivery procedure, which suggests a deleterious effect of hepatocellular toxicity on transgene expression. GdCl₃ treatment was ineffective for repeat vector infusions. In parallel studies, dogs were infused with potentially therapeutic transposons. Activities of transgenic IDUA and GUSB in plasma peaked at 50-350% of wildtype, but in the absence of immunosuppression lasted only a few days. Transposition was detectable by excision assay only when the most efficient transposase, SB100X, was used. Dogs infused with transposons encoding canine clotting factor IX (cFIX) were treated with GdCl₃ and showed expression profiles similar to those in cSEAP-infused dogs, with expression peaking at 40% wt (2 μg/mL). It is concluded that GdCl₃ can support extended transgene expression after hydrodynamic introduction of SB transposons in dogs, but that alternative regimens will be required to achieve therapeutic levels of transgene products.

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.

Preventing High Fat Diet-induced Obesity and Improving Insulin Sensitivity through Neuregulin 4 Gene Transfer

Neuregulin 4 (NRG4), an epidermal growth factor-like signaling molecule, plays an important role in cell-to-cell communication during tissue development. Its function to regulate energy metabolism has recently been reported. This current study was designed to assess the preventive and therapeutic effects of NRG4 overexpression on high fat diet (HFD)-induced obesity. Using the hydrodynamic gene transfer method, we demonstrate that Nrg4 gene transfer in mice suppressed the development of diet-induced obesity, but did not affect pre-existing adiposity and body weight in obese mice. Nrg4 gene transfer curbed HFD-induced hepatic steatosis by inhibiting lipogenesis and PPARγ-mediated lipid storage. Concurrently, overexpression of NRG4 reduced chronic inflammation in both preventive and treatment studies, evidenced by lower mRNA levels of macrophage marker genes including F4/80, Cd68, Cd11b, Cd11c, and macrophage chemokine Mcp1, resulting in improved insulin sensitivity. Collectively, these results demonstrate that overexpression of the Nrg4 gene by hydrodynamic gene delivery prevents HFD-induced weight gain and fatty liver, alleviates obesity-induced chronic inflammation and insulin resistance, and supports the health benefits of NRG4 in managing obesity and obesity-associated metabolic disorders.

ADAMTS13 autoantibodies cloned from patients with acquired thrombotic thrombocytopenic purpura: 2. Pathogenicity in an animal model

BACKGROUND

Acquired thrombotic thrombocytopenic purpura (TTP) is a potentially fatal disease in which ultralarge von Willebrand factor (UL-VWF) multimers accumulate as a result of autoantibody inhibition of the VWF protease, ADAMTS13. Current treatment is not specifically directed at the responsible autoantibodies and in some cases is ineffective or of transient benefit. More rational, reliable, and durable therapies are needed, and a human autoantibody-mediated animal model would be useful for their development. Previously, TTP patient anti-ADAMTS13 single-chain variable-region fragments (scFv's) were cloned that inhibited ADAMTS13 proteolytic activity in vitro and expressed features in common with inhibitory immunoglobulin G in patient plasma. Here, pathogenicity of these scFv's is explored in vivo by transfecting mice with inhibitory antibody cDNA.

STUDY DESIGN AND METHODS

Hydrodynamic tail vein injection of naked DNA encoding human anti-ADAMTS13 scFv was used to create sustained ADAMTS13 inhibition in mice. Accumulation of UL-VWF multimers was measured and formation of platelet (PLT) thrombi after focal or systemic vascular injury was examined.

RESULTS

Transfected mice expressed physiological plasma levels of human scFv and developed sustained ADAMTS13 inhibition and accumulation of unprocessed UL-VWF multimers. Induced focal endothelial injury generated PLT thrombi extending well beyond the site of initial injury, and systemic endothelial injury induced thrombocytopenia, schistocyte formation, PLT thrombi, and death.

CONCLUSIONS

These results demonstrate for the first time the ability of human recombinant monovalent anti-ADAMTS13 antibody fragments to recapitulate key pathologic features of untreated acquired TTP in vivo, validating their clinical significance and providing an animal model for testing novel targeted therapeutic approaches.