Current Gene Therapy (v.17, #1)

Meet Our Editorial Board Member by Assumpcio Bosch (1-3).

Introduction: The first human adeno-associated virus (AAV) was originally discovered in 1960s as a contaminant of adenovirus stock preparation and thus it had not been of medical interest. Throughout the last three decades AAV has gained popularity to be used in gene therapy, mainly due to its replicative defectiveness and lack of pathogenicity in human. In addition, its ability to mediate stable and long-term expression in both non-dividing and dividing cells with specific tissue tropism makes AAV one of the most promising candidates for therapeutic gene transfer to treat many inherited as well as non-inherited disorders. Moreover, the use of AAV is not only restricted to overexpression of recombinant transgene, but also to over-express short hairpin RNA and microRNA to knockdown the expression of genes in targeted tissues.

Discussion and Conclusion: This review is organized into four parts. In the first part of the review, we discuss about the discovery and history of AAV, followed by detailed AAV biology such as virus genome, virus structure and its life cycle. In the second part of the review, the discussion is centred on the molecular mechanisms of AAV and tissue transduction, including receptor recognition and cell binding, endosomal entry, virus uncoating, nuclear entry and genome replication. Advantages and limitations of using AAV as a safe vehicle for gene delivery is also discussed. In the third part of the review, we discuss about the most commonly used AAV serotypes and variants isolated from human and non-human primates, focusing on their diverse tissue tropisms, transduction efficiency, immunological profiles and their applications in animal studies. Final part of the review focuses on the recent progress of in-vivo gene transfer using AAV for inherited and non-inherited diseases in both preclinical and clinical settings with a special emphasis on potential clinical applications of AAV in the field of liver disease.

Introduction: In Japan, the Pharmaceuticals and Medical Devices Law was passed in 2014. In this new law, regenerative medical products were defined, and a conditional and term-limited approval system only for regenerative medical products was instituted. Therefore, regenerative medical products can be approved based on phase I and/or II trials. Gene therapy and adoptive cellular therapy are categorized as regenerative medical products. This law is intended for registration trials for marketing authorization. The Act on the Safety of Regenerative Medicine was also implemented in 2014. This act is intended for clinical research and medical practice involving processed cells other than registration trials. Under this act, a review of plans on medical treatments or clinical studies by a certified committee and submission of the plans to the Ministry of Health, Labour and Welfare (MHLW) are mandatory. The MHLW instituted the SAKIGAKE (meaning a pioneer or forerunner in Japanese) designation system in 2015. This designation is similar to the breakthrough therapy designation in the US and PRIME in the EU. In addition, the MHLW started the 'Project for Enhanced Practical Application of Innovative Drugs, Medical Devices and Regenerative Medical Products' to promote personnel exchange and cooperation in writing of guidelines on the evaluation of innovative medical products between the Pharmaceuticals and Medical Devices Agency and academia. Some new guidelines regarding gene and cellular therapy were published.

Conclusion: In this review, we comprehensively described these complicated regulations and problems to be solved in order to facilitate global readers' understanding of Japanese regulatory frameworks.

Mesenchymal Stem Cell-derived Extracellular Vesicles for Renal Repair by Arash Aghajani Nargesi, Lilach O. Lerman, Alfonso Eirin (29-42).
Introduction: Transplantation of autologous mesenchymal stem cells (MSCs) has been shown to attenuate renal injury and dysfunction in several animal models, and its efficacy is currently being tested in clinical trials for patients with renal disease. Accumulating evidence indicates that MSCs release extracellular vesicles (EVs) that deliver genes, microRNAs and proteins to recipient cells, acting as mediators of MSC paracrine actions. In this context, it is critical to characterize the MSC-derived EV cargo to elucidate their potential contribution to renal repair. In recent years, researchers have performed high-throughput sequencing and proteomic analysis to detect and identify genes, microRNAs, and proteins enriched in MSC-derived EVs.

Conclusion: The present review summarizes the current knowledge of the MSC-derived EV secretome to shed light into the mechanisms mediating MSC renal repair, and discusses preclinical and clinical studies testing the efficacy of MSC-derived EVs for treating renal disease.

Perspectives of Gene Therapies in Autosomal Dominant Polycystic Kidney Disease by Yuchen Xu, Ao Li, Guanqing Wu, Chaozhao Liang (43-49).
Background: Autosomal dominant polycystic kidney disease (ADPKD) is the most common inherited kidney disease in the clinic. The predominant clinical manifestation is bilateral and progressive cysts formation in the kidneys, impairs normal renal parenchyma, and ultimately leads to endstage renal disease (ESRD). ADPKD is a heterogenic disease which is resulted from the mutations of PKD1 or PKD2 genes which encode polycystin-1 (PC1) and -2 (PC2), thereby multiple cell signaling pathways are involved.

Method: Although causative genes and aberrant signaling pathways have been investigated for decades, lack of effective and less side-effect treatment for the disease still perplex vast clinicians. Therefore, development of new therapeutic approaches for ADPKD is currently very much desired.

Conclusion: This review will center on pathogenesis of ADPKD, and thereafter gene transfer will be discussed as potential treatment for the disease. New therapeutic interventions will bring further hope to improve prognosis of this incurable disease.

Readthrough of SCN5A Nonsense Mutations p.R1623X and p.S1812X Questions Gene-therapy in Brugada Syndrome by Siyong Teng, Jian Huang, Zhan Gao, Jie Hao, Yuejin Yang, Shu Zhang, Jielin Pu, Rutai Hui, Yongjian Wu, Zheng Fan (50-58).
Purpose: Nonsense mutation readthrough is used as a gene-specific treatment in some genetic diseases. The response to readthrough treatment is determined by the readthrough efficiency of various nonsense mutations. In this manuscript, we aimed to explore the harmful effects of nonsense mutation suppression.

Methods: HEK293 cells were transfected with two SCN5A (encode cardiac Na+ channel) nonsense mutations, p.R1623X and p.S1812X. We applied two readthrough-enhancing methods (either aminoglycosides or a siRNA-targeting eukaryotic release factor eRF3a (a GTPase that binds eRF1)) to suppress these SCN5A nonsense mutations. When either of readthrough methods was used, the sodium channel proteins were examined by western blot and immunoblotting and recorded by whole cell patch-clamp to observe the functional characterization of the restored channels.

Results: Upon readthrough treatment, the sodium currents were restored to the mutant cDNAs. These mutations reduced full-length sodium channel protein levels, and the sodium currents were reduced to 3% of wild-type. The mutant cDNA sodium currents were increased to 30% of wild-type, and the fulllength proteins also increased. However, the functional characterization of these channels from cDNAs carrying p.R1623X and p.S1812X exhibited abnormal biophysical properties, including a negative shift in steady-state sodium channel inactivation, a positive shift in sodium channel activation and robust late sodium currents. The ramp test showed prolonged QT intervals.

Conclusion: These results demonstrated that readthrough-enhancing methods effectively suppressed nonsense mutations in SCN5A and restored the expression of full-length channels. However, the restored channels may increase the risk of arrhythmia.

Glioblastoma Targeted Gene Therapy Based on pEGFP/p53-Loaded Superparamagnetic Iron Oxide Nanoparticles by Touba Eslaminejad, Seyed Noureddin Nematollahi-Mahani, Mehdi Ansari (59-69).
Background: Blood-brain barrier (BBB) separates the neural tissue from circulating blood because of its high selectivity. This study focused on the in vitro application of magnetic nanoparticles to deliver Tp53 as a gene of interest to glioblastoma (U87) cells across a simulated BBB model that comprised KB cells.

Material and Method: After magnetic and non-magnetic nanoparticles were internalized by KB cells, their location in these cells was examined by transmission electron microscopy. Transfection efficiency of DNA to U87 cells was evaluated by fluorescence microscopy, real time PCR, flowcytometry, and Western immuno-blotting. When a magnetic field was applied, a large number of magnetic nanoparticles accumulated in KB cells, appearing as black dots scattered in the cytoplasm of cells. Fluorescence microscope examination showed that transfection of the DNA to U87 target cells was highest in cells treated with magnetic nanoparticles and exposed to a magnetic field. Also it was reflected in significantly increased mRNA level while the p53 protein level was decreased.

Conclusion: It could be concluded that a significant increase in total apoptosis was induced in cells by magnetic nanoparticles, coupled with exposure to a magnetic force (p ≤0.01) as compared with cells that were not exposed to magnetism.