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We report on validating a mitochondrial gene therapeutic strategy using fibroblasts derived from patients with an A1555G point mutation in mitochondrial DNA coding 12S ribosomal RNA (rRNA (12S)). Wild-type rRNA (12S) as a therapeutic RNA was encapsulated in a mitochondrial targeting liposome, a MITO-Porter (rRNA-MITO-Porter), and an attempt was made to deliver the MITO-Porter to mitochondria of the diseased cells. It was confirmed that the rRNA-MITO-Porter treatment significantly decreased the ratio of the mutant rRNA content. Moreover, it was shown that the mitochondrial respiratory activities of the diseased cells were improved as the result of the mitochondrial transfection of the rRNA-MITO-Porter., (Copyright © 2020 Elsevier B.V. and Mitochondria Research Society. All rights reserved.)

Mitochondrial function is reduced in skeletal muscles of many patients with systemic diseases and it is difficult to deliver medicinal substances to mitochondria in such tissue. In this study, we report on attempts to develop liposome-based carriers for mitochondrial delivery using mouse myoblasts (C2C12) by varying the lipid composition of the carriers. We found that a liposome that contains an optimal lipid modified with the KALA peptide (a cellular uptake and mitochondrial targeting device) was the most effective nanocarrier for achieving mitochondrial delivery in C2C12 cells. We also report on successful mitochondrial transgene expression using the carriers encapsulating a mitochondrial DNA vector as we previously reported., (Copyright © 2019 Elsevier B.V. and Mitochondria Research Society. All rights reserved.)

Mitochondrial gene therapy will be needed to treat mitochondrial diseases. We previously demonstrated mitochondrial gene silencing by the mitochondrial delivery of antisense RNA oligonucleotide (ASO) targeting mtDNA-encoded mRNA using a MITO-Porter, a liposomal nano carrier system designed for mitochondrial delivery. Here, we report on the efficient packaging of ASO in the MITO-Porter via a nanoparticle packaging method, which showed a 10-fold higher packaging efficiency than the conventional method. The constructed carrier showed a decrease in the target mRNA levels and ATP production. These results indicate that such a MITO-Porter has potential for use in therapies designed to regulate mitochondrial function., (Copyright © 2019 Elsevier B.V. and Mitochondria Research Society. All rights reserved.)

Nanomedicine promises to play an important role in next generation therapy, including Nucleic acid/Gene therapy. To accomplish this, innovative nanotechnologies will be needed to support nanomedicine by controlling not only the biodistribution but also the intracellular trafficking of macromolecules such as RNA/DNA. A multifunctional envelope-type nano device (MEND) was developed to meet this requirement. We herein provide an update regarding the functions of the MEND system focusing on the introduction of different functional biomaterials that enhance efficiency. The octaarginine (R8) peptide enhances cellular uptake and controls intracellular trafficking to induce synergism in transgene expression. The R8 was also used for developing a MITO-Porter system for mitochondrial targeting. The function of the MITO-Porter system was extended by developing a mitochondrial reporter gene for mitochondrial gene therapy. For efficient in vivo gene delivery, new pH-sensitive lipids have been introduced to achieve controlled biodistribution and to enhance endosomal escape. For example, the CL4H6 lipid exerts a more efficient in vivo gene silencing than that of ONPATTRO TM , a preparation that has been approved by the US Food and Drug Administration. We further summarize new technologies that have been successfully applied to cancer immunotherapy leading to the introduction of a new strategy based on the concept of the Cancer-Immunity Cycle., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

To achieve mitochondrial gene therapy, therapeutic molecules need to be transported through the outer and inner membranes of mitochondria into the innermost space (mitochondrial matrix), which contains the mtDNA pool. We previously reported on the construction of a MITO-Porter with a high fusogenic activity for the mitochondrial outer membrane for delivering molecules to the mitochondria of human cells. Here, we report on an investigation of a fusogenic lipid composition for the inner membrane, and an analysis of the fusogenic compositions for the outer and inner membranes. A significant relationship was found between fusion activity and the mitochondrial delivery of nucleic acids., (Copyright © 2015 © Elsevier B.V. and Mitochondria Research Society. Published by Elsevier B.V. All rights reserved.)

Mitochondrial genome-targeting nucleic acids are promising therapeutic candidates for treating mitochondrial diseases. To date, a number of systems for delivering genetic information to the cytosol and the nucleus have been reported, and several successful gene therapies involving gene delivery targeted to the cytosol and the nucleus have been reported. However, much less progress has been made concerning mitochondrial gene delivery systems, and mitochondrial gene therapy has never been achieved. Here, we report on the mitochondrial delivery of an antisense RNA oligonucleotide (ASO) to perform mitochondrial RNA knockdown to regulate mitochondrial function. Mitochondrial delivery of the ASO was achieved using a combination of a MITO-Porter system, which contains mitochondrial fusogenic lipid envelopes for mitochondrial delivery via membrane fusion and D-arm, a mitochondrial import signal of tRNA to the matrix. Mitochondrial delivery of the ASO induces the knockdown of the targeted mitochondria-encoded mRNA and protein, namely cytochrome c oxidase subunit II, a component of the mitochondrial respiratory chain. Furthermore, the mitochondrial membrane potential was depolarized by the down regulation of the respiratory chain as the result of the mitochondrial delivery of ASO. This finding constitutes the first report to demonstrate that the nanocarrier-mediated mitochondrial genome targeting of antisense RNA effects mitochondrial function., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

To achieve mitochondrial therapy, we previously reported on the use of an octaarginine (R8) modified Dual Function (DF)-MITO-Porter for delivering molecules to mitochondria in living cells. In this study, using isolated mitochondria, homogenates and living cells, we evaluated the utility of mitochondrial targeting functional peptides as a ligand for delivering carriers. The S2 peptide modified carrier showed a high mitochondrial targeting activity in homogenates and living cells. In addition, the S2 peptide had a lower cell toxicity compared to R8 modified liposomes. The S2 peptide represents a potentially useful moiety for constructing an efficient and safe mitochondrial delivery system., (© 2013.)

The focus of this study was on the development of a nano carrier targeted to mitochondria, a promising therapeutic drug target. We synthesized a lipid derivative that is conjugated with a mitochondrial targeting signal peptide (MTS), which permits the selective delivery of certain types of proteins to mitochondria. We then explored the use of an innovative technology in which MTS and the MITO-Porter were integrated. The latter is a liposome that delivers cargos to mitochondria via membrane fusion. The results indicate that the combination of MTS and the MITO-Porter would be useful for selective mitochondrial delivery via membrane fusion., (Copyright © 2012 Elsevier B.V. and Mitochondria Research Society. All rights reserved. All rights reserved.)