Gene therapy for liver diseases - progress and challenges

Epidemiology of liver diseases: global disease burden and forecasted research trends

We assessed the global incidence, mortality, and disability-adjusted life years (DALYs) associated with various liver diseases, including alcohol-related liver disease (ALD), hepatitis B/C virus infections (HBV or HCV), liver cancer, metabolic dysfunction-associated steatotic liver disease (MASLD), and other chronic liver diseases, from the 2019 Global Burden of Disease study. Additionally, we analyzed the global trends in hepatology research and drug development. From 2000 to 2019, prevalence rates increased for ALD, MASLD and other liver diseases, while they decreased for HBV, HCV, and liver cancer. Countries with a high socio-demographic index (SDI) exhibited the lowest mortality rates and DALYs. The burden of liver diseases varied due to factors like sex and region. In nine representative countries, MASLD, along with hepatobiliary cancer, showed highest increase in funding in hepatology research. Globally, the major research categories in hepatology papers from 2000 to 2019 were cancer, pathobiology, and MASLD. The United States (U.S.) was at the forefront of hepatology research, with China gradually increasing its influence over time. Hepatologists worldwide are increasingly focusing on studying the communication between the liver and other organs, while underestimating the research on ALD. Cancer, HCV, and MASLD were the primary diseases targeted for therapeutic development in clinical trials. However, the proportion of new drugs approved for the treatment of liver diseases was relatively low among all newly approved drugs in the U.S., China, Japan, and the European Union. Notably, there were no approved drug for the treatment of ALD in the world.

Gene editing in liver diseases

The deliberate and precise modification of the host genome using engineered nucleases represents a groundbreaking advancement in modern medicine. Several clinical trials employing these approaches to address metabolic liver disorders have been initiated, with recent remarkable outcomes observed in patients with transthyretin amyloidosis, highlighting the potential of these therapies. Recent technological improvements, particularly CRISPR Cas9-based technology, have revolutionized gene editing, enabling in vivo modification of the cellular genome for therapeutic purposes. These modifications include gene supplementation, correction, or silencing, offering a wide range of therapeutic possibilities. Moving forward, we anticipate witnessing the unfolding therapeutic potential of these strategies in the coming years. The aim of our review is to summarize preclinical data on gene editing in animal models of inherited liver diseases and the clinical data obtained thus far, emphasizing both therapeutic efficacy and potential limitations of these medical interventions.

Development of mRNA Lipid Nanoparticles: Targeting and Therapeutic Aspects

Lipid nanoparticles (LNPs) have emerged as leading non-viral carriers for messenger RNA (mRNA) delivery in clinical applications. Overcoming challenges in safe and effective mRNA delivery to target tissues and cells, along with controlling release from the delivery vehicle, remains pivotal in mRNA-based therapies. This review elucidates the structure of LNPs, the mechanism for mRNA delivery, and the targeted delivery of LNPs to various cells and tissues, including leukocytes, T-cells, dendritic cells, Kupffer cells, hepatic endothelial cells, and hepatic and extrahepatic tissues. Here, we discuss the applications of mRNA-LNP vaccines for the prevention of infectious diseases and for the treatment of cancer and various genetic diseases. Although challenges remain in terms of delivery efficiency, specific tissue targeting, toxicity, and storage stability, mRNA-LNP technology holds extensive potential for the treatment of diseases.

Drug-induced liver injury related to gene therapy: A new challenge to be managed

Gene therapy is being successfully developed for the treatment of several genetic disorders. Various methods of gene transfer have been developed to enable the production of the deficient enzyme or protein. One of the most important is adeno-associated virus vectors, which have been shown to be viable for use in in vivo gene therapy. Several gene therapies have already been approved. They are also promising for acquired diseases. Important examples include gene therapy for haemophilia A and B, X-linked myotubular myopathy, spinal muscular atrophy and several liver diseases such as Criggler-Najjar disease, alpha-1 antitrypsin deficiency and Fabry disease. However, the introduction of a foreign compound into hepatocytes leads to hepatic reactions with heterogeneous phenotypic expression and a wide spectrum of severity, ranging from mild transaminase elevation to acute liver failure. Several mechanisms appear to be involved in liver injury, including an immune response, but also direct toxicity depending on the method of gene transfer. As a result, the incidence, expression and severity of liver injury vary from indication to indication and from patient to patient. Patients treated for haemophilia A are more prone to transaminase elevation than those treated for haemophilia B. Corticosteroids are successfully used to correct liver reactions but also to prevent degradation of the transferred gene and loss of therapeutic activity. The aim of this review is to describe the risk of liver injury according to the indication for gene therapy and the short- and long-term management currently proposed to prevent or correct liver reactions in clinical practice.

Plate-Based High-Throughput Fluorescence Assay for Assessing Enveloped Virus Integrity

Viruses are a considerable threat to global health and place major burdens on economies worldwide. Manufactured viruses are also being widely used as delivery agents to treat (gene therapies) or prevent diseases (vaccines). Therefore, it is vital to study and fully understand the infectious state of viruses. Current techniques used to study viruses are often slow or nonexistent, making the development of new techniques of paramount importance. Here we present a high-throughput and robust, cell-free plate-based assay (FAIRY: Fluorescence Assay for vIRal IntegritY), capable of differentiating intact from nonintact enveloped viruses, i.e, infectious from noninfectious. Using a thiazole orange-terminated polymer, a 99% increase in fluorescence was observed between treated (heat or virucide) and nontreated. The FAIRY assay allowed for the rapid determination of the infectivity of a range of enveloped viruses, highlighting its potential as a valuable tool for the study of viruses and interventions against them.

Intracellular Trafficking Defects in Congenital Intestinal and Hepatic Diseases

Enterocytes and liver cells fulfill important metabolic and barrier functions and are responsible for crucial vectorial secretive and absorptive processes. To date, genetic diseases affecting metabolic enzymes or transmembrane transporters in the intestine and the liver are better comprehended than mutations affecting intracellular trafficking. In this review, we explore the emerging knowledge on intracellular trafficking defects and their clinical manifestations in both the intestine and the liver. We provide a detailed overview including more investigated diseases such as the canonical, variant and associated forms of microvillus inclusion disease, as well as recently described pathologies, highlighting the complexity and disease relevance of several trafficking pathways. We give examples of how intracellular trafficking hubs, such as the apical recycling endosome system, the trans-Golgi network, lysosomes, or the Golgi-to-endoplasmic reticulum transport are involved in the pathomechanism and lead to disease. Ultimately, understanding these processes could spark novel therapeutic approaches, which would greatly improve the quality of life of the affected patients.

Safe and effective liver-directed AAV-mediated homology-independent targeted integration in mouse models of inherited diseases

Liver-directed adeno-associated viral (AAV) vector-mediated homology-independent targeted integration (AAV-HITI) by CRISPR-Cas9 at the highly transcribed albumin locus is under investigation to provide sustained transgene expression following neonatal treatment. We show that targeting the 3' end of the albumin locus results in productive integration in about 15% of mouse hepatocytes achieving therapeutic levels of systemic proteins in two mouse models of inherited diseases. We demonstrate that full-length HITI donor DNA is preferentially integrated upon nuclease cleavage and that, despite partial AAV genome integrations in the target locus, no gross chromosomal rearrangements or insertions/deletions at off-target sites are found. In line with this, no evidence of hepatocellular carcinoma is observed within the 1-year follow-up. Finally, AAV-HITI is effective at vector doses considered safe if directly translated to humans providing therapeutic efficacy in the adult liver in addition to newborn. Overall, our data support the development of this liver-directed AAV-based knockin strategy.

Emerging mRNA Technology for Liver Disease Therapy

Liver diseases have consistently posed substantial challenges to global health. It is crucial to find innovative methods to effectively prevent and treat these diseases. In recent times, there has been an increasing interest in the use of mRNA formulations that accumulate in liver tissue for the treatment of hepatic diseases. In this review, we start by providing a detailed introduction to the mRNA technology. Afterward, we highlight types of liver diseases, discussing their causes, risks, and common therapeutic strategies. Additionally, we summarize the latest advancements in mRNA technology for the treatment of liver diseases. This includes systems based on hepatocyte growth factor, hepatitis B virus antibody, left-right determination factor 1, human hepatocyte nuclear factor α, interleukin-12, methylmalonyl-coenzyme A mutase, etc. Lastly, we provide an outlook on the potential of mRNA technology for the treatment of liver diseases, while also highlighting the various technical challenges that need to be addressed. Despite these difficulties, mRNA-based therapeutic strategies may change traditional treatment methods, bringing hope to patients with liver diseases.

Lipid-nanoparticle-enabled nucleic acid therapeutics for liver disorders

Inherited genetic disorders of the liver pose a significant public health burden. Liver transplantation is often limited by the availability of donor livers and the exorbitant costs of immunosuppressive therapy. To overcome these limitations, nucleic acid therapy provides a hopeful alternative that enables gene repair, gene supplementation, and gene silencing with suitable vectors. Though viral vectors are the most efficient and preferred for gene therapy, pre-existing immunity debilitating immune responses limit their use. As a potential alternative, lipid nanoparticle-mediated vectors are being explored to deliver multiple nucleic acid forms, including pDNA, mRNA, siRNA, and proteins. Herein, we discuss the broader applications of lipid nanoparticles, from protein replacement therapy to restoring the disease mechanism through nucleic acid delivery and gene editing, as well as multiple preclinical and clinical studies as a potential alternative to liver transplantation.

Advances in basic research on glucagon and alpha cells

The regulation of plasma amino acid levels by glucagon in humans first attracted the attention of researchers in the 1980s. Recent basic research using animal models of glucagon deficiency suggested that a major physiological role of glucagon is the regulation of amino acid metabolism rather than to increase blood glucose levels. In this regard, novel feedback regulatory mechanisms that are mediated by glucagon and amino acids have recently been described between islet alpha cells and the liver. Increasingly, hyperglucagonemia in humans with diabetes and/or nonalcoholic fatty liver diseases is reported to likely be a compensatory response to hepatic glucagon resistance. Severe glucagon resistance due to a glucagon receptor mutation in humans causes hyperaminoacidemia and islet alpha cell expansion combined with pancreatic hypertrophy. Notably, a recent report showed that the restoration of glucagon resistance by liver transplantation resolved not only hyperglucagonemia, but also pancreatic hypertrophy and other metabolic disorders. The mechanisms that regulate islet cell proliferation by amino acids largely remain unelucidated. Clarification of such mechanisms will increase our understanding of the pathophysiology of diseases related to glucagon.

Steering the course of CAR T cell therapy with lipid nanoparticles

Lipid nanoparticles (LNPs) have proven themselves as transformative actors in chimeric antigen receptor (CAR) T cell therapy, surpassing traditional methods and addressing challenges like immunogenicity, reduced toxicity, and improved safety. Promising preclinical results signal a shift toward safer and more effective CAR T cell treatments. Ongoing research aims to validate these findings in clinical trials, marking a new era guided by LNPs utility in CAR therapy. Herein, we explore the preference for LNPs over traditional methods, highlighting the versatility of LNPs and their effective delivery of nucleic acids. Additionally, we address key challenges in clinical considerations, heralding a new era in CAR T cell therapy.

A comprehensive review of miR-21 in liver disease: Big impact of little things

microRNAs (miRNAs), a class of non-coding RNA with 20-24 nucleotides, are defined as the powerful regulators for gene expression. miR-21 is a multifunctional miRNA enriched in the circulatory system and multiple organs, which not only serves as a non-invasive biomarker in disease diagnosis, but also participates in many cellular activities. In various chronic liver diseases, the increase of miR-21 affects glycolipid metabolism, viral infection, inflammatory and immune cell activation, hepatic stellate cells activation and tissue fibrosis, and autophagy. Moreover, miR-21 is also a liaison in the deterioration of chronic liver disease to hepatocellular carcinoma (HCC), and it impacts on cell proliferation, apoptosis, migration, invasion, angiogenesis, immune escape, and epithelial-mesenchymal transformation by regulating target genes expression in different signaling pathways. In current research on miRNA therapy, some natural products can exert the hepatoprotective effects depending on the inhibition of miR-21 expression. In addition, miR-21-based therapeutic also play a role in regulating intracellular miR-21 levels and enhancing the efficacy of chemotherapy drugs. Herein, we systemically summarized the recent progress of miR-21 on biosynthesis, biomarker function, molecular mechanism and miRNA therapy in chronic liver disease and HCC, and looked forward to outputting some information to enable it from bench to bedside.

Therapeutic In Vivo Gene Editing Achieved by a Hypercompact CRISPR-Cas12f1 System Delivered with All-in-One Adeno-Associated Virus

CRISPR-based gene therapies are making remarkable strides toward the clinic. But the large size of most widely used Cas endonucleases including Cas9 and Cas12a restricts their efficient delivery by the adeno-associated virus (AAV) for in vivo gene editing. Being exceptionally small, the recently engineered type V-F CRISPR-Cas12f1 systems can overcome the cargo packaging bottleneck and present as strong candidates for therapeutic applications. In this study, the pairwise editing efficiencies of different engineered Cas12f1/sgRNA scaffold combinations are systemically screened and optimized, and the CasMINI_v3.1/ge4.1 system is identified as being able to significantly boost the gene editing activity. Moreover, packaged into single AAV vectors and delivered via subretinal injection, CasMINI_v3.1/ge4.1 achieves remarkably high in vivo editing efficiencies, over 70% in transduced retinal cells. Further, the efficacy of this Cas12f1 system-based gene therapy to treat retinitis pigmentosa in RhoP23H mice is demonstrated by the therapeutic benefits achieved including rescued visual function and structural preservation. And minimal bystander editing activity is detected. This work advances and expands the therapeutic potential of the miniature Cas12f1 system to support efficient and accurate in vivo gene therapy.

Between hope and reality: treatment of genetic diseases through nucleic acid-based drugs

Rare diseases (RD) affect a small number of people compared to the general population and are mostly genetic in origin. The first clinical signs often appear at birth or in childhood, and patients endure high levels of pain and progressive loss of autonomy frequently associated with short life expectancy. Until recently, the low prevalence of RD and the gatekeeping delay in their diagnosis have long hampered research. The era of nucleic acid (NA)-based therapies has revolutionized the landscape of RD treatment and new hopes arise with the perspectives of disease-modifying drugs development as some NA-based therapies are now entering the clinical stage. Herein, we review NA-based drugs that were approved and are currently under investigation for the treatment of RD. We also discuss the recent structural improvements of NA-based therapeutics and delivery system, which overcome the main limitations in their market expansion and the current approaches that are developed to address the endosomal escape issue. We finally open the discussion on the ethical and societal issues that raise this new technology in terms of regulatory approval and sustainability of production.

Innovative pharmacotherapy for hepatic metabolic and chronic inflammatory diseases in China

Liver disease constitutes a significant global health concern, particularly in China where it has distinctive characteristics. China grapples with a staggering 300 million cases, predominantly due to hepatitis B and metabolic non-alcoholic fatty liver disease. Additionally, hepatocellular carcinoma has become a prevalent which is a lethal type of cancer. Despite the scarcity of innovative treatment options, Chinese hepatologists and researchers have achieved notable breakthroughs in the prevention, diagnosis, management and treatment of liver diseases. Traditional Chinese medicines have found widespread application in the treatment of various liver ailments owing to their commendable pharmacological efficacy and minimal side effects. Furthermore, there is a growing body of research in extracellular vesicles, cell therapy and gene therapy, offering new hope in the fight against liver diseases. This paper provides a comprehensive overview of the epidemiological characteristics of liver diseases and the diverse array of treatments that Chinese scholars and scientists have pursued in critical field.

Exploring modified chitosan-based gene delivery technologies for therapeutic advancements

One of the critical steps in gene therapy is the successful delivery of the genes. Immunogenicity and toxicity are major issues for viral gene delivery systems. Thus, non-viral vectors are explored. A cationic polysaccharide like chitosan could be used as a nonviral gene delivery vector owing to its significant interaction with negatively charged nucleic acid and biomembrane, providing effective cellular uptake. However, the native chitosan has issues of targetability, unpacking ability, and solubility along with poor buffer capability, hence requiring modifications for effective use in gene delivery. Modified chitosan has shown that the "proton sponge effect" involved in buffering the endosomal pH results in osmotic swelling owing to the accumulation of a greater amount of proton and chloride along with water. The major challenges include limited exploration of chitosan as a gene carrier, the availability of high-purity chitosan for toxicity reduction, and its immunogenicity. The genetic drugs are in their infancy phase and require further exploration for effective delivery of nucleic acid molecules as FDA-approved marketed formulations soon.

Chemically Modified Platforms for Better RNA Therapeutics

RNA-based therapies have catalyzed a revolutionary transformation in the biomedical landscape, offering unprecedented potential in disease prevention and treatment. However, despite their remarkable achievements, these therapies encounter substantial challenges including low stability, susceptibility to degradation by nucleases, and a prominent negative charge, thereby hindering further development. Chemically modified platforms have emerged as a strategic innovation, focusing on precise alterations either on the RNA moieties or their associated delivery vectors. This comprehensive review delves into these platforms, underscoring their significance in augmenting the performance and translational prospects of RNA-based therapeutics. It encompasses an in-depth analysis of various chemically modified delivery platforms that have been instrumental in propelling RNA therapeutics toward clinical utility. Moreover, the review scrutinizes the rationale behind diverse chemical modification techniques aiming at optimizing the therapeutic efficacy of RNA molecules, thereby facilitating robust disease management. Recent empirical studies corroborating the efficacy enhancement of RNA therapeutics through chemical modifications are highlighted. Conclusively, we offer profound insights into the transformative impact of chemical modifications on RNA drugs and delineates prospective trajectories for their future development and clinical integration.

Zwitterionic materials for nucleic acid delivery and therapeutic applications

Nucleic acid therapeutics have demonstrated substantial potential in combating various diseases. However, challenges persist, particularly in the delivery of multifunctional nucleic acids. To address this issue, numerous gene delivery vectors have been developed to fully unlock the potential of gene therapy. The advancement of innovative materials with exceptional delivery properties is critical to propel the clinical translation of nucleic acid drugs. Cationic vector materials have received extensive attention, while zwitterionic materials remain relatively underappreciated in delivery. In this review, we outline a diverse range of zwitterionic material nucleic acid carriers, predominantly encompassing zwitterionic lipids, polymers and peptides. Their respective chemical structures, synthesis approaches, properties, advantages, and therapeutic applications are summarized and discussed. Furthermore, we highlight the challenges and future opportunities associated with the development of zwitterionic vector materials. This review will aid to understand the zwitterionic materials in aiding gene delivery, contributing to the continual progress of nucleic acid therapeutics.

A20 ameliorates Aspergillus fumigatus keratitis by promoting autophagy and inhibiting NF-κB signaling

Fungal keratitis (FK) is a serious, potentially sight-threatening corneal infection, which is associated with poor prognosis. A20, also called TNFAIP3, plays significant roles in the negative regulation of inflammation and immunity. However, the function of A20 in Aspergillus fumigatus (A. fumigatus) keratitis remains obscure. Herein, we found that the level of A20 is increased in human corneal epithelial cells (HCECs) and in mouse corneas with A. fumigatus infection, and that nuclear factor-κB (NF-κB) signaling is required for A20 upregulation. A20 overexpression inhibits A. fumigatus-mediated inflammatory responses, while A20 knockdown results in opposite effect. Mechanically, we showed that A20 inhibits NF-κB signaling and activates autophagy in infected HCECs. We also showed that inhibition of NF-κB signaling reverses the increased inflammatory responses in infected HCECs with A20 knockdown. Furthermore, autophagy blockage impedes the anti-inflammatory effect of A20 in A. fumigatus infected HCECs. Moreover, A20 ameliorates the corneal damage and inflammation in A. fumigatus infected mouse corneas. In conclusion, this study reveals that A20 alleviates A. fumigatus keratitis by activating autophagy and inhibiting NF-κB signaling. This suggests that exogenous use of A20 protein may be a potentially promising therapeutic strategy for FK treatment.

Topoisomerase Inhibitors Increase Episomal DNA Expression by Inducing the Integration of Episomal DNA in Hepatic Cells

Gene therapy is a promising strategy to treat and cure most inherited metabolic liver disorders. Viral vectors such as those based on adeno-associated viruses (AAVs) and lentiviruses (LVs) are used as vehicles to deliver functional genes to affected hepatocytes. Adverse events associated with the use of high vector doses have motivated the use of small molecules as adjuvants to reduce the dose. In this study, we showed that a one-hour treatment with topoisomerase inhibitors (camptothecin and etoposide) prior to viral transduction is enough to increase AAV and LV reporter expression in non-dividing hepatic cells in culture. Topoisomerase inhibitors increased both integration-competent (ICLV) and integration-deficient (IDLV) LV-derived expression, with a much stronger increase in the IDLV transduction system. In agreement with that, topoisomerase inhibitors increased viral genome integration in both strains, with a greater impact on the IDLV strain, supporting the idea that topoisomerase inhibitors increased episomal DNA integration, especially when viral integrase activity is abolished. These effects correlated with an increase in the DNA damage response produced by the treatments. Our study highlights the need to monitor DNA damage and undesired integration of viral episomal DNAs into the host genome when studying chemical compounds that increase viral transduction.

Hepatic soluble epoxide hydrolase activity regulates cerebral Aβ metabolism and the pathogenesis of Alzheimer's disease in mice

Alzheimer's disease (AD) is caused by a complex interaction between genetic and environmental factors. However, how the role of peripheral organ changes in response to environmental stimuli during aging in AD pathogenesis remains unknown. Hepatic soluble epoxide hydrolase (sEH) activity increases with age. Hepatic sEH manipulation bidirectionally attenuates brain amyloid-β (Aβ) burden, tauopathy, and cognitive deficits in AD mouse models. Moreover, hepatic sEH manipulation bidirectionally regulates the plasma level of 14,15-epoxyeicosatrienoic acid (-EET), which rapidly crosses the blood-brain barrier and modulates brain Aβ metabolism through multiple pathways. A balance between the brain levels of 14,15-EET and Aβ is essential for preventing Aβ deposition. In AD models, 14,15-EET infusion mimicked the neuroprotective effects of hepatic sEH ablation at biological and behavioral levels. These results highlight the liver's key role in AD pathology, and targeting the liver-brain axis in response to environmental stimuli may constitute a promising therapeutic approach for AD prevention.

New Developments and Challenges in Liver Transplantation

Liver disease is increasing in incidence and is the third most common cause of premature death in the United Kingdom and fourth in the United States. Liver disease accounts for 2 million deaths globally each year. Three-quarters of patients with liver disease are diagnosed at a late stage, with liver transplantation as the only definitive treatment. Thomas E. Starzl performed the first human liver transplant 60 years ago. It has since become an established treatment for end-stage liver disease, both acute and chronic, including metabolic diseases and primary and, at present piloting, secondary liver cancer. Advances in surgical and anaesthetic techniques, refined indications and contra-indications to transplantation, improved donor selection, immunosuppression and prognostic scoring have allowed the outcomes of liver transplantation to improve year on year. However, there are many limitations to liver transplantation. This review describes the milestones that have occurred in the development of liver transplantation, the current limitations and the ongoing research aimed at overcoming these challenges.

Non-Invasive Intranasal Delivery of pApoE2: Effect of Multiple Dosing on the ApoE2 Expression in Mice Brain

Chitosan-based polymeric micelles are promising non-viral nanocarriers for safe and targeted gene delivery. Multi-functionalized chitosan polymeric micelles were prepared by grafting fatty acid, cell-penetrating peptide, and mannose on the chitosan backbone. The polymeric micelles were subjected to surface morphology and surface topography using scanning electron microscopy and atomic force microscopy, respectively. The hemotoxic profile of the prepared polymeric micelles was established against erythrocytes and was found to be <5% hemotoxic up to the concentration of 600 µg/mL. In vitro ApoE2 expression in primary astrocytes and neurons was analyzed. Multi-functionalized polymeric micelles produced greater (p < 0.05) transfection in astrocytes and neurons in comparison to mono-functionalized micelles. Intranasal administration of polymeric micelles/pApoE2 polyplex led to significantly higher (p < 0.05) in vivo pApoE2 expression than chitosan and unfunctionalized polymeric micelles-treated mice groups. The outcomes of this study predict that the developed multi-functionalized polymeric micelles could be an effective and safe gene delivery platform to the brain through the intranasal route.