CRISPR/Cas9 therapeutics for liver diseases

Optimizing CRISPR/Cas9 precision: Mitigating off-target effects for safe integration with photodynamic and stem cell therapies in cancer treatment

CRISPR/Cas9 precision genome editing has revolutionized cancer treatment by introducing specific alterations to the cancer genome. But the therapeutic potential of CRISPR/Cas9 is limited by off-target effects, which can cause undesired changes to genomic regions and create major safety concerns. The primary emphasis lies in their implications within the realm of cancer photodynamic therapy (PDT), where precision is paramount. PDT is a promising cancer treatment method; nevertheless, its effectiveness is severely limited and readily leads to recurrence due to the therapeutic resistance of cancer stem cells (CSCs). With a focus on targeted genome editing into cancer cells during PDT and stem cell treatment (SCT), the review aims to further the ongoing search for safer and more accurate CRISPR/Cas9-mediated methods. At the core of this exploration are recent advancements and novel techniques that offer promise in mitigating the risks associated with off-target effects. With a focus on cancer PDT and SCT, this review critically assesses the landscape of off-target effects in CRISPR/Cas9 applications, offering a comprehensive knowledge of their nature and prevalence. A key component of the review is the assessment of cutting-edge delivery methods, such as technologies based on nanoparticles (NPs), to optimize the distribution of CRISPR components. Additionally, the study delves into the intricacies of guide RNA design, focusing on advancements that bolster specificity and minimize off-target effects, crucial elements in ensuring the precision required for effective cancer PDT and SCT. By synthesizing insights from various methodologies, including the exploration of innovative genome editing tools and leveraging robust validation methods and bioinformatics tools, the review aspires to chart a course towards more reliable and precise CRISPR-Cas9 applications in cancer PDT and SCT. For safe PDT and SCT integration in cancer therapy, CRISPR/Cas9 precision optimization is essential. Utilizing sophisticated molecular and computational techniques to address off-target effects is crucial to realizing the therapeutic promise of these technologies, which will ultimately lead to the development of individualized and successful cancer treatment strategies. Our long-term goals are to improve precision genome editing for more potent cancer therapy approaches by refining the way CRISPR/Cas9 is integrated with photodynamic and stem cell therapies.

CRISPR-Cpf1 system and its applications in animal genome editing

The clustered regularly interspaced short palindromic repeats (CRISPR) and their associated protein (Cas) system is a gene editing technology guided by RNA endonuclease. The CRISPR-Cas12a (also known as CRISPR-Cpf1) system is extensively utilized in genome editing research due to its accuracy and high efficiency. In this paper, we primarily focus on the application of CRISPR-Cpf1 technology in the construction of disease models and gene therapy. Firstly, the structure and mechanism of the CRISPR-Cas system are introduced. Secondly, the similarities and differences between CRISPR-Cpf1 and CRISPR-Cas9 technologies are compared. Thirdly, the main focus is on the application of the CRISPR-Cpf1 system in cell and animal genome editing. Finally, the challenges faced by CRISPR-Cpf1 technology and corresponding strategies are analyzed. Although CRISPR-Cpf1 technology has certain off-target effects, it can effectively and accurately edit cell and animal genomes, and has significant advantages in the preclinical research.

Natural Biopolymer-Based Delivery of CRISPR/Cas9 for Cancer Treatment

Over the last decade, the clustered, regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) system has become the most promising gene editing tool and is broadly utilized to manipulate the gene for disease treatment, especially for cancer, which involves multiple genetic alterations. Typically, CRISPR/Cas9 machinery is delivered in one of three forms: DNA, mRNA, or ribonucleoprotein. However, the lack of efficient delivery systems for these macromolecules confined the clinical breakthrough of this technique. Therefore, a variety of nanomaterials have been fabricated to improve the stability and delivery efficiency of the CRISPR/Cas9 system. In this context, the natural biopolymer-based carrier is a particularly promising platform for CRISPR/Cas9 delivery due to its great stability, low toxicity, excellent biocompatibility, and biodegradability. Here, we focus on the advances of natural biopolymer-based materials for CRISPR/Cas9 delivery in the cancer field and discuss the challenges for their clinical translation.

Antioxidant and anti-inflammatory agents in chronic liver diseases: Molecular mechanisms and therapy

Chronic liver disease (CLD) is a continuous process that causes a reduction of liver function lasting more than six months. CLD includes alcoholic liver disease (ALD), non-alcoholic fatty liver disease (NAFLD), chronic viral infection, and autoimmune hepatitis, which can lead to liver fibrosis, cirrhosis, and cancer. Liver inflammation and oxidative stress are commonly associated with the development and progression of CLD. Molecular signaling pathways such as AMP-activated protein kinase (AMPK), C-Jun N-terminal kinase, and peroxisome proliferator-activated receptors (PPARs) are implicated in the pathogenesis of CLD. Therefore, antioxidant and anti-inflammatory agents from natural products are new potent therapies for ALD, NAFLD, and hepatocellular carcinoma (HCC). In this review, we summarize some powerful products that can be potential applied in all the stages of CLD, from ALD/NAFLD to HCC. The selected agents such as β-sitosterol, curcumin, genistein, and silymarin can regulate the activation of several important molecules, including AMPK, Farnesoid X receptor, nuclear factor erythroid 2-related factor-2, PPARs, phosphatidylinositol-3-kinase, and lysyl oxidase-like proteins. In addition, clinical trials are undergoing to evaluate their efficacy and safety.

Exosome-mediated delivery of Cas9 ribonucleoprotein complexes for tissue-specific gene therapy of liver diseases

CRISPR-Cas9 gene editing has emerged as a powerful therapeutic technology, but the lack of safe and efficient in vivo delivery systems, especially for tissue-specific vectors, limits its broad clinical applications. Delivery of Cas9 ribonucleoprotein (RNP) owns competitive advantages over other options; however, the large size of RNPs exceeds the loading capacity of currently available delivery vectors. Here, we report a previously unidentified genome editing delivery system, named exosome^RNP, in which Cas9 RNPs were loaded into purified exosomes isolated from hepatic stellate cells through electroporation. Exosome^RNP facilitated effective cytosolic delivery of RNP in vitro while specifically accumulated in the liver tissue in vivo. Exosome^RNP showed vigorous therapeutic potential in acute liver injury, chronic liver fibrosis, and hepatocellular carcinoma mouse models via targeting p53 up-regulated modulator of apoptosis (PUMA), cyclin E1 (CcnE1), and K (lysine) acetyltransferase 5 (KAT5), respectively. The developed exosome^RNP provides a feasible platform for precise and tissue-specific gene therapies of liver diseases.

State-of-the-Art 2019 on Gene Therapy for Phenylketonuria

Phenylketonuria (PKU) is considered to be a paradigm for a monogenic metabolic disorder but was never thought to be a primary application for human gene therapy due to established alternative treatment. However, somewhat unanticipated improvement in neuropsychiatric outcome upon long-term treatment of adults with PKU with enzyme substitution therapy might slowly change this assumption. In parallel, PKU was for a long time considered to be an excellent test system for experimental gene therapy of a Mendelian autosomal recessive defect of the liver due to an outstanding mouse model and the easy to analyze and well-defined therapeutic end point, that is, blood l-phenylalanine concentration. Lifelong treatment by targeting the mouse liver (or skeletal muscle) was achieved using different approaches, including (1) recombinant adeno-associated viral (rAAV) or nonviral naked DNA vector-based gene addition, (2) genome editing using base editors delivered by rAAV vectors, and (3) by delivering rAAVs for promoter-less insertion of the PAH-cDNA into the Pah locus. In this article we summarize the gene therapeutic attempts of correcting a mouse model for PKU and discuss the future implications for human gene therapy.

Low-density lipoprotein receptor-deficient hepatocytes differentiated from induced pluripotent stem cells allow familial hypercholesterolemia modeling, CRISPR/Cas-mediated genetic correction, and productive hepatitis C virus infection

BACKGROUND

Familial hypercholesterolemia type IIA (FH) is due to mutations in the low-density lipoprotein receptor (LDLR) resulting in elevated levels of low-density lipoprotein cholesterol (LDL-c) in plasma and in premature cardiovascular diseases. As hepatocytes are the only cells capable of metabolizing cholesterol, they are therefore the target cells for cell/gene therapy approaches in the treatment of lipid metabolism disorders. Furthermore, the LDLR has been reported to be involved in hepatitis C virus (HCV) entry into hepatocytes; however, its role in the virus infection cycle is still disputed.

METHODS

We generated induced pluripotent stem cells (iPSCs) from a homozygous LDLR-null FH-patient (FH-iPSCs). We constructed a correction cassette bearing LDLR cDNA under the control of human hepatic apolipoprotein A2 promoter that targets the adeno-associated virus integration site AAVS1. We differentiated both FH-iPSCs and corrected FH-iPSCs (corr-FH-iPSCs) into hepatocytes to study statin-mediated regulation of genes involved in cholesterol metabolism. Upon HCV particle inoculation, viral replication and production were quantified in these cells.

RESULTS

We showed that FH-iPSCs displayed the disease phenotype. Using homologous recombination mediated by the CRISPR/Cas9 system, FH-iPSCs were genetically corrected by the targeted integration of a correction cassette at the AAVS1 locus. Both FH-iPSCs and corr-FH-iPSCs were then differentiated into functional polarized hepatocytes using a stepwise differentiation approach (FH-iHeps and corr-FH-iHeps). The correct insertion and expression of the correction cassette resulted in restoration of LDLR expression and function (LDL-c uptake) in corr-FH-iHeps. We next demonstrated that pravastatin treatment increased the expression of genes involved in cholesterol metabolism in both cell models. Moreover, LDLR expression and function were also enhanced in corr-FH-iHeps after pravastatin treatment. Finally, we demonstrated that both FH-iHeps and corr-FH-iHeps were as permissive to viral infection as primary human hepatocytes but that virus production in FH-iHeps was significantly decreased compared to corr-FH-iHeps, suggesting a role of the LDLR in HCV morphogenesis.

CONCLUSIONS

Our work provides the first LDLR-null FH cell model and its corrected counterpart to study the regulation of cholesterol metabolism and host determinants of HCV life cycle, and a platform to screen drugs for treating dyslipidemia and HCV infection.

Potentials of CRISPR in liver research and therapy

The CRISPR technology is rapidly transforming the field of liver research by its versatility and easy use. In vivo gene editing of hepatocytes in adult mice can be achieved using a broad toolbox for both fundamental research and development of therapeutic strategies for future clinical applications. Recent studies showed that CRISPR has a real potential to treat hereditary liver diseases as well as virally induced pathologies. This short review recapitulates very recent advancements regarding the use of CRISPR in liver research and therapy.

Generation of the Adenovirus Vector-Mediated CRISPR/Cpf1 System and the Application for Primary Human Hepatocytes Prepared from Humanized Mice with Chimeric Liver

The clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein (Cas) 9 system is now widely used as a genome editing tool. CRISPR-associated endonuclease in Prevotella and Francisella 1 (Cpf1) is a recently discovered Cas endonuclease that is designable and highly specific with efficiencies comparable to those of Cas9. Here we generated the adenovirus (Ad) vector carrying an Acidaminococcus sp. Cpf1 (AsCpf1) expression cassette (Ad-AsCpf1) for the first time. Ad-AsCpf1 was applied to primary human hepatocytes prepared from humanized mice with chimeric liver in combination with the Ad vector expressing the guide RNA (gRNA) directed to the Adeno-associated virus integration site 1 (AAVS1) region. The mutation rates were estimated by T7 endonuclease I assay around 12% of insertion/deletion (indel). Furthermore, the transduced human hepatocytes were viable (ca. 60%) at two weeks post transduction. These observations suggest that the Ad vector-mediated delivery of the CRISPR/AsCpf1 system provides a useful tool for genome manipulation of human hepatocytes.