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Photodynamic therapy is expected to be a less invasive treatment, and strategies for targeting mitochondria, the main sources of singlet oxygen, are attracting attention to increase the efficacy of photodynamic therapy and reduce its side effects. To date, we have succeeded in encapsulating the photosensitizer rTPA into MITO-Porter (MP), a mitochondria-targeted Drug Delivery System (DDS), aimed at mitochondrial delivery of the photosensitizer while maintaining its activity. In this study, we report the results of our studies to alleviate rTPA aggregation in an effort to improve drug efficacy and assess the usefulness of modifying the rTPA side chain to improve the mitochondrial retention of MITO-Porter, which exhibits high therapeutic efficacy. Conventional rTPA with anionic side chains and two rTPA analogs with side chains that were converted to neutral or cationic side chains were encapsulated into MITO-Porter. Low-MP (MITO-Porter with Low Drug/Lipid) exhibited high drug efficacy for all three types of rTPA, and in Low-MP, charged rTPA-encapsulated MP exhibited high drug efficacy. The cellular uptake and mitochondrial translocation capacities were similar for all particles, suggesting that differences in aggregation rates during the incorporation of rTPA into MITO-Porter resulted in differences in drug efficacy. [ABSTRACT FROM AUTHOR]

Photodynamic therapy is expected to be a less invasive treatment, and strategies for targeting mitochondria, the main sources of singlet oxygen, are attracting attention to increase the efficacy of photodynamic therapy and reduce its side effects. To date, we have succeeded in encapsulating the photosensitizer rTPA into MITO-Porter (MP), a mitochondria-targeted Drug Delivery System (DDS), aimed at mitochondrial delivery of the photosensitizer while maintaining its activity. In this study, we report the results of our studies to alleviate rTPA aggregation in an effort to improve drug efficacy and assess the usefulness of modifying the rTPA side chain to improve the mitochondrial retention of MITO-Porter, which exhibits high therapeutic efficacy. Conventional rTPA with anionic side chains and two rTPA analogs with side chains that were converted to neutral or cationic side chains were encapsulated into MITO-Porter. Low-MP (MITO-Porter with Low Drug/Lipid) exhibited high drug efficacy for all three types of rTPA, and in Low-MP, charged rTPA-encapsulated MP exhibited high drug efficacy. The cellular uptake and mitochondrial translocation capacities were similar for all particles, suggesting that differences in aggregation rates during the incorporation of rTPA into MITO-Porter resulted in differences in drug efficacy.

Activation of autophagy represents a potential therapeutic strategy for the treatment of diseases that are caused by the accumulation of defective proteins and the formation of abnormal organelles. Methylated β-cyclodextrins-threaded polyrotaxane (Me-PRX), a supramolecular structured polymer, induces autophagy by interacting with the endoplasmic reticulum. We previously reported on the successful activation of mitochondria-targeted autophagy by delivering Me-RRX to mitochondria using a MITO-Porter, a mitochondria-targeted nanocarrier. The same level of autophagy induction was achieved at one-twentieth the dosage for the MITO-Porter (Me-PRX) compared to the naked Me-PRX. We report herein on the quantitative evaluation of the intracellular organelle localization of both naked Me-PRX and the MITO-Porter (Me-PRX). Mitochondria, endoplasmic reticulum and lysosomes were selected as target organelles because they would be involved in autophagy induction. In addition, organelle injury and cell viability assays were performed. The results showed that the naked Me-PRX and the MITO-Porter (Me-PRX) were localized in different intracellular organelles, and organelle injury was different, depending on the route of administration, indicating that different organelles contribute to autophagy induction. These findings indicate that the organelle to which the autophagy-inducing molecules are delivered plays an important role in the level of induction of autophagy. [ABSTRACT FROM AUTHOR]

The recent rapid progress in the area of drug delivery systems (DDS) has opened a new era in medicine with a strong linkage to understanding the molecular mechanisms associated with cancer survival. In this review, we summarize new cancer strategies that have recently been developed based on our DDS technology. Cancer immunotherapy will be improved based on the concept of the cancer immunity cycle, which focuses on dynamic interactions between various types of cancer and immune cells in our body. The new technology of genome editing will also be discussed with reference to how these new DDS technologies can be used to introduce therapeutic cargoes into our body. Lastly, a new organelle, mitochondria will be the focus of creating a new cancer treatment strategy by a MITO-Porter which can deliver macromolecules directly to mitochondria of cancer cells via a membrane fusion approach and the impact of controlled intracellular trafficking will be discussed. [Display omitted] [ABSTRACT FROM AUTHOR]

Activation of autophagy represents a potential therapeutic strategy for the treatment of diseases that are caused by the accumulation of defective proteins and the formation of abnormal organelles. Methylated β-cyclodextrins-threaded polyrotaxane (Me-PRX), a supramolecular structured polymer, induces autophagy by interacting with the endoplasmic reticulum. We previously reported on the successful activation of mitochondria-targeted autophagy by delivering Me-RRX to mitochondria using a MITO-Porter, a mitochondria-targeted nanocarrier. The same level of autophagy induction was achieved at one-twentieth the dosage for the MITO-Porter (Me-PRX) compared to the naked Me-PRX. We report herein on the quantitative evaluation of the intracellular organelle localization of both naked Me-PRX and the MITO-Porter (Me-PRX). Mitochondria, endoplasmic reticulum and lysosomes were selected as target organelles because they would be involved in autophagy induction. In addition, organelle injury and cell viability assays were performed. The results showed that the naked Me-PRX and the MITO-Porter (Me-PRX) were localized in different intracellular organelles, and organelle injury was different, depending on the route of administration, indicating that different organelles contribute to autophagy induction. These findings indicate that the organelle to which the autophagy-inducing molecules are delivered plays an important role in the level of induction of autophagy.

Large amounts of ATP are produced in mitochondria especially in the brain and heart, where energy consumption is high compared with other organs. Thus, a decrease in ATP production in such organs could be a cause of many diseases such as neurodegenerative diseases and heart disease. Based on thus assumption, increasing intracellular ATP production in such organs could be a therapeutic strategy. In this study, we report on the delivery of vitamin B 1 , a coenzyme that activates the tricarboxylic acid (TCA) cycle, to the inside of mitochondria. Since the TCA cycle is responsible for ATP production, we hypothesized delivering vitamin B 1 to mitochondria would enhance ATP production. To accomplish this, we used a mitochondrial targeted liposome a "MITO-Porter" as the carrier. Using SH-SY5Y cells, a model neuroblast, cellular uptake and intracellular localization were analyzed using flow cytometry and confocal laser scanning microscopy. The optimized MITO-Porter containing encapsulated vitamin B 1 (MITO-Porter (VB 1)) was efficiently accumulated in mitochondria of SH-SY5Y cells. Further studies confirmed that the level of ATP production after the MITO-Porter (VB 1) treatment was significantly increased as compared to a control group that was treated with naked vitamin B 1. This study provides the potential for an innovative therapeutic strategy in which the TCA cycle is activated, thus enhancing ATP production. [ABSTRACT FROM AUTHOR]

Here, we report on validating a mitochondrial gene therapy by delivering nucleic acids to mitochondria of diseased cells by a MITO-Porter, a liposome-based carrier for mitochondrial delivery. We used cells derived from a patient with a mitochondrial disease with a G625A heteroplasmic mutation in the tRNAPhe of the mitochondrial DNA (mtDNA). It has been reported that some mitochondrial gene diseases are caused by heteroplasmic mutations, in which both mutated and wild-type (WT) genes are present, and the accumulation of pathological mutations leads to serious, intractable, multi-organ diseases. Therefore, the decrease of the mutated gene rate is considered to be a useful gene therapy strategy. To accomplish this, wild-type mitochondrial pre-tRNAPhe (pre-WT-tRNAPhe), prepared by in vitro transcription, was encapsulated in the MITO-Porter. The pre-WT-tRNAPhe encapsulated in the MITO-Porter was transfected into diseased mitochondrial cells, and the resulting mutant levels were examined by an amplification refractory mutation system (ARMS)-quantitative PCR. The mutation rate of tRNAPhe was decreased, and this therapeutic effect was sustained even on the 8th day after transfection. Furthermore, mitochondrial respiratory activity of the disease cells was increased after the transfection of therapeutic pre-WT-tRNAPhe. These results support the conclusion that the mitochondrial delivery of therapeutic nucleic acids represents a viable strategy for mitochondrial gene therapy.

The era of Nanomedicine has arrived with the approval of ONPATTRO™ by the FDA in 2018. Lipid nanoparticle (LNP) technology has succeeded in delivering siRNA to the human liver in genetic diseases and has also been applied to mRNA vaccinations for COVID-19 using a similar LNP technology. In this review, we focus on the current status of new lipids for use in LNP formulations including our original lipids (CL4H6/CL4C6/CL4D6) as well as mechanisms of targeting without a ligand. Clinical applications of nano DDS are moving forward rapidly in the field of cancer immunology since the successful introduction of OPDIVO™ in 2014. Antigen presentation and the maturation of immune cells can be controlled by nano DDS for cancer immunotherapy. YSK12-C4, a newly designed ionizable amino lipid can induce successful immune activation by silencing mRNA in DC and NK cells, which are expected to be evaluated for clinical use. Finally, new cancer therapy by targeting mitochondria involving the use of a MITO-Porter, a membrane fusion-type mitochondrial delivery system, has been introduced. The importance of delivering a photo sensitizer to mitochondria was clearly demonstrated in photodynamic cancer therapy. Clinical applications of MITO-Porters started in collaborative efforts with LUCA Science Co., Ltd. And was established in 2018. The future direction of Nanomedicine is discussed. Unlabelled Image [ABSTRACT FROM AUTHOR]

Due to the rapid changes that have occurred in the field of drug discovery and the recent developments in the early 21st century, the role of drug delivery systems (DDS) has become increasingly more important. For the past 20 years, our laboratory has been developing gene delivery systems based on lipid-based delivery systems. One of our efforts has been directed toward developing a multifunctional envelope-type nano device (MEND) by modifying the particle surface with octaarginine, which resulted in a remarkably enhanced cellular uptake and improved intracellular trafficking of plasmid DNA (pDNA). When we moved to in vivo applications, however, we were faced with the PEG-dilemma and we shifted our strategy to the incorporation of ionizable cationic lipids into our system. This resulted in some dramatic improvements over our original design and this can be attributed to the development of a new lipid library. We have also developed a mitochondrial targeting system based on a membrane fusion mechanism using a MITO-Porter, which can deliver nucleic acids/pDNA into the matrix of mitochondria. After the appearance of antibody medicines, Opdivo, an immune checkpoint inhibitor, has established cancer immunology as the 4th strategy in cancer therapy. Our DDS technologies can also be applied to this new field of cancer therapy to cure cancer by controlling our immune mechanisms. The latest studies are summarized in this review article. Unlabelled Image • Evolution of our DDS from original multifunctional envelope-type nano device (MEND). • Endogenous and exogenous ligands facilitate LNP-mediated hepatic delivery of RNAs. • The structure of cationic lipids impact efficiency of endosomal escape of RNAs. • Challenge for mitochondrial RNA therapy by MITO-Porter, a mitochondrial DDS. • Delivering immunofunctional molecules by nano DDS enhances the Cancer-Immunity Cycle. [ABSTRACT FROM AUTHOR]

• We report on validating mitochondrial RNA therapeutic strategy by mitochondrial DDS. • Therapeutic rRNA was encapsulated in a mitochondrial targeting rRNA-MITO-Porter. • rRNA-MITO-Porter significantly improved mitochondrial activities of diseased cells. 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. [ABSTRACT FROM AUTHOR]

Mitochondrial delivery of an anticancer drug targeting cancer cells would eventually result in cell death. To achieve this, a drug delivery system targeting mitochondria is needed. We recently developed a MITO-Porter, a liposome that delivers its cargo to mitochondria. We reported that such a MITO-Porter could deliver doxorubicin (DOX), an anticancer drug, to mitochondria in OS-RC-2 cells, a drug resistant cancer cell, resulting in inhibiting the cell growth, based in in vitro experiments. Herein, we report on validating the benefit of such a therapeutic strategy for treating drug resistant cancers by the in vivo targeting of mitochondria. We prepared a DOX-MITO-Porter, in which DOX was encapsulated in the MITO-Porter and optimized its retention in blood circulation. When the DOX-MITO-Porter was administered to mice bearing OS-RC-2 cells via tail vein injection, tumor size was significantly decreased, compared to DOX itself and to the DOX-encapsulated polyethylene glycol-modified liposome (DOX-PEG-LP). Intracellular observation confirmed that the DOX-MITO-Porter had accumulated in tumor mitochondria. It was also found a relationship between anti-tumor effect and the mitochondrial function, as indicated by the depolarization of mitochondrial membrane potential. This study provides support for the utility of an in vivo mitochondrial delivery system in drug resistant cancer therapies. [ABSTRACT FROM AUTHOR]

Mitochondria carry out various essential functions including ATP production, the regulation of apoptosis and possess their own genome (mtDNA). Delivering target molecules to this organelle, it would make it possible to control the functions of cells and living organisms and would allow us to develop a better understanding of life. Given the fact that mitochondrial dysfunction has been implicated in a variety of human disorders, delivering therapeutic molecules to mitochondria for the treatment of these diseases is an important issue. To date, several mitochondrial drug delivery system (DDS) developments have been reported, but a generalized DDS leading to therapy that exclusively targets mitochondria has not been established. This review focuses on mitochondria-targeted therapeutic strategies including antioxidant therapy, cancer therapy, mitochondrial gene therapy and cell transplantation therapy based on mitochondrial DDS. A particular focus is on nanocarriers for mitochondrial delivery with the goal of achieving mitochondria-targeting therapy. We hope that this review will stimulate the accelerated development of mitochondrial DDS. Unlabelled Image [ABSTRACT FROM AUTHOR]

There have been many reports on the relationship between mitochondrial oxidative stress and various types of diseases. This review covers mitochondrial targeting photodynamic therapy and photothermal therapy as a therapeutic strategy for inducing mitochondrial oxidative stress. We also discuss other mitochondrial targeting phototherapeutic methods. In addition, we discuss anti-oxidant therapy by a mitochondrial drug delivery system (DDS) as a therapeutic strategy for suppressing oxidative stress. We also describe cell therapy for reducing oxidative stress in mitochondria. Finally, we discuss the possibilities and problems associated with clinical applications of mitochondrial DDS to regulate mitochondrial oxidative stress. [ABSTRACT FROM AUTHOR]

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. • We succeeded in developing a nano carrier for mitochondrial delivery using myoblasts. • We also report on successful mitochondrial transgene expression using this carrier. • A KALA peptide modification to a liposome was effective for mitochondrial delivery. [ABSTRACT FROM AUTHOR]

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. • Antisense RNA was efficiently packaged in the MITO-Porter for mitochondrial delivery. • The constructed carrier showed a decrease in the target mRNA levels. • MITO-Porter could be used in therapies designed to regulate mitochondrial function. [ABSTRACT FROM AUTHOR]

Mitochondrial transplantation therapy is an innovative strategy for the treatment of mitochondrial dysfunction. The approach has been reported to be useful in the treatment of cardiac ischemic reperfusion injuries in human clinical trials and has also been shown to be useful in animal studies as a method for treating mitochondrial dysfunction in various tissues, including the heart, liver, lungs, and brain. On the other hand, there is no methodology for using preserved mitochondria. Research into the pharmaceutical formulation of mitochondria to promote mitochondrial transplantation therapy as the next step in treating many patients is urgently needed. In this review, we overview previous studies on the therapeutic effects of mitochondrial transplantation. We also discuss studies related to immune responses that occur during mitochondrial transplantation and methods for preserving mitochondria, which are key to their stability as medicines. Finally, we describe research related to mitochondrial targeting drug delivery systems (DDS) and discuss future perspectives of mitochondrial transplantation.

To achieve mitochondrial gene therapy, developing a mitochondrial transgene expression system that produces therapeutic proteins in mitochondria of disease cells is essential. We previously reported on the design of pCMV-mtLuc (CGG) containing a CMV promotor and a NanoLuc (Nluc) luciferase gene that records adjustments to the mitochondrial codon system, and showed that the mitochondrial transfection of pCMV-mtLuc (CGG) resulted in the efficient production of the Nluc luciferase protein in human HeLa cells. This mitochondrial transfection was achieved using a MITO-Porter, a liposome-based carrier for delivering a cargo to mitochondria via membrane fusion. We report herein that mitochondrial transfection using the MITO-Porter results in mitochondrial transgene expression in G625A fibroblasts obtained from a patient with a mitochondrial disease. We investigated the effect of promoters and the basic structure of pCMV-mtLuc (CGG) on gene expression efficiency, and were able to construct a high performance mitochondrial DNA vector, pCMV-mtLuc (CGG) [hND4] that contains a human mitochondrial endogenous gene. We also constructed an RP/KALA-MITO-Porter composed of the KALA peptide (cell-penetrating peptide) with a mitochondrial RNA aptamer to enhance cellular uptake and mitochondrial targeting. Finally, the mitochondrial transfection of pCMV-mtLuc (CGG) [hND4] in G625A fibroblasts using the RP/KALA-MITO-Porter resulted in strong mitochondrial transgene expression. [ABSTRACT FROM AUTHOR]

It has been reported that transplanting native cells would lack efficiency without producing artificial cell-tissue, due to the exaggerated oxidative stress in doxorubicin-induced cardiomyopathy. We attempted to activate cardiac progenitor cells (CPCs) by delivering resveratrol to mitochondria using a mitochondrial drug delivery system (MITO-Porter system). We first evaluated the viability of H9c2 cells (a cardio myoblast cell line) after doxorubicin treatment, where H9c2 cells were co-cultured with or without the mitochondria activated CPCs (referred to herein as MITO cell). We next evaluated the survival rate of doxorubicin treated mice, with or without the injection of MITO cells into the myocardium. Finally, we examined the molecular mechanism of the cell therapy by detecting oxidative stress and the induction of apoptosis in addition to quantification of the mRNA and protein levels about oxidative phosphorylation (OXPHOS). The MITO cell transplanted mice lived significantly longer than the conventional CPC transplanted ones. Oxidative stress and massive cell death were both significantly reduced in the MITO cell transplanted hearts, in which the expression levels of OXPHOS protein and gene were also higher than the control group. In doxorubicin-induced cardiomyopathy, the transplantation of MITO cells, which possess activated mitochondria, is more efficient compared to conventional CPC transplantation. [ABSTRACT FROM AUTHOR]

We herein report on a mitochondrial therapeutic effect based on the delivery of coenzyme Q 10 (CoQ 10 ), an anti-oxidant, to in vivo mitochondria using a MITO-Porter, a liposome-based mitochondrial delivery system that functions via membrane fusion. To evaluate the effects, we used a mouse liver ischemia/reperfusion injury (I/R injury) model, in which mitochondrial reactive oxygen species are overexpressed. We packaged CoQ 10 in the lipid phase of a MITO-Porter and optimized the mitochondrial fusogenic activities to produce the CoQ 10 -MITO-Porter. A histological observation of the carriers in the liver by confocal laser scanning microscopy was done and the accumulation of the carrier labeled with a radio isotope in the liver confirmed that the CoQ 10 -MITO-Porter was delivered to liver mitochondria via systemic injection. These analytical results permitted us to optimize the compositions of the CoQ 10 -MITO-Porter so as to permit it to efficiently accumulate in mouse liver mitochondria. Finally, we applied the optimized CoQ 10 -MITO-Porter to mice via tail vein injection, and hepatic I/R injury was then induced, followed by measuring serum alanine aminotransferase (ALT) levels, a marker of liver injury. We confirmed that the use of the CoQ 10 -MITO-Porter resulted in a significant decrease in serum ALT levels, indicating that in vivo mitochondrial delivery of the CoQ 10 via MITO-Porter prevents I/R injury in mice livers. This provides a demonstration of the potential use of such a delivery system in mitochondrial therapies. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Abstract: 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. [Copyright &y& Elsevier]

This study focused on the intracellular observation of nanocarriers modified with a mitochondrial targeting signal peptide (MTS). The nanocarriers showed an efficient cellular uptake, and the MTS had a positive effect on their mitochondrial targeting. This is the first report of an intracellular observation of nanocarriers modified with MTS. [Copyright &y& Elsevier]

Introduction: After the emergence of lipid nanoparticles (LNP) containing therapeutic mRNA as vaccines for use against the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the clinical usefulness of nucleic acid-encapsulated LNPs is now a fact. In addition to the nucleus and cytoplasm, mitochondria, which have their own genome, are a site where nucleic acids function in the cell. Gene therapies targeting mitochondria are expected to pave the way for the next generation of therapies., Areas Covered: Methods for delivering nucleic acids to mitochondria are needed in order to realize such innovative therapies. However, only a few reports on delivery systems targeting mitochondria have appeared. In this review, we summarize the current state of research on RNA-based therapeutics targeted to mitochondria, with emphasis on mitochondrial RNA delivery therapies and on therapies that involve the use of mitochondrial genome editing devices., Expert Opinion: We hope that this review article will focus our attention to this area of research, stimulate more interest in this field of research, and lead to the development of mitochondria-targeted nucleic acid medicine. It has the potential to become a major weapon against urgent and unknown diseases, including SARS-CoV-2 infections.

Abstract: 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 &y& Elsevier]

The fact that mitochondrial dysfunction has been implicated in a variety of human diseases suggests that they would be expected as a target organelle for these diseases. Bongkrekic acid (BKA) is a chemical that functions as a ligand of the adenine nucleotide translocator and is known to potently inhibit the mitochondrial permeability transition that is associated with apoptosis. Thus, delivering it to mitochondria would be an innovative therapy for the treatment of mitochondrial diseases that are largely associated with apoptosis. Here, we report on the use of a MITO-Porter, an innovative nanocarrier for mitochondrial delivery via mitochondrial membrane fusion, for delivering BKA to mitochondria. We first constructed a BKA-MITO-Porter, in which BKA is contained in lipid envelopes of a MITO-Porter. We then confirmed that the BKA-MITO-Porter was efficiently internalized into cells and is delivered to mitochondria, similar to a conventional MITO-Porter. Moreover, we evaluated the antiapoptosis effect of the BKA-MITO-Porter in HeLa cells by measuring caspase 3/7 activity. The findings confirmed that the BKA-MITO-Porter showed a strong antiapoptosis effect compared with naked BKA. The results reported here demonstrate its potential for the use in therapies aimed at mitochondrial diseases, as a mitochondrial medicine candidate. © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 102:1008-1015, 2013 [ABSTRACT FROM AUTHOR]

Mitochondrial gene therapy has the potential for curing a variety of diseases that are associated with mitochondrial DNA mutations and/or defects. To achieve this, it will be necessary to deliver therapeutic agents into the mitochondria in diseased cells. A number of mitochondrial drug delivery systems have been reported to date. However, reports of mitochondrial-targeted DNA delivery are limited. To achieve this, the therapeutic agent must be taken up by the cell (1), after which, the multi-processes associated with intracellular trafficking must be sophisticatedly regulated so as to release the agent from the endosome and deliver it to the cytosol (2) and to pass through the mitochondrial membrane (3). We report herein on the mitochondrial delivery of oligo DNA as a model therapeutic using a Dual Function (DF)-MITO-Porter, an innovative nano carrier designed for mitochondrial delivery. The critical structural elements of the DF-MITO-Porter include mitochondria-fusogenic inner envelopes and endosome-fusogenic outer envelopes, modified with octaarginine which greatly assists in cellular uptake. Inside the cell, the carrier passes through the endosomal and mitochondrial membranes via step-wise membrane fusion. When the oligo DNA was packaged in the DF-MITO-Porter, cellular uptake efficiency was strongly enhanced. Intracellular observation using confocal laser scanning microscopy showed that the DF-MITO-Porter was effectively released from endosomes. Moreover, the findings confirmed that the mitochondrial targeting activity of the DF-MITO-Porter was significantly higher than that of a carrier without outer endosome-fusogenic envelopes. These results support the conclusion that mitochondrial-targeted DNA delivery using a DF-MITO-Porter can be achieved when intracellular trafficking is optimally regulated. [ABSTRACT FROM AUTHOR]

Abstract: Mitochondrial dysfunction has been implicated in a variety of human diseases. It is now well accepted that mutations and defects in the mitochondrial genome form the basis of these diseases. Therefore, mitochondrial gene therapy and diagnosis would be expected to have great medical benefits. To achieve such a strategy, it will be necessary to deliver therapeutic agents into mitochondria in living cells. We report here on an approach to accomplish this via the use of a Dual Function (DF)-MITO-Porter, aimed at the mitochondrial genome, so-called mitochondrial DNA (mtDNA). The DF-MITO-Porter, a nano carrier for mitochondrial delivery, has the ability to penetrate the endosomal and mitochondrial membranes via step-wise membrane fusion. We first constructed a DF-MITO-Porter encapsulating DNase I protein as a bioactive cargo. It was expected that mtDNA would be digested, when the DNase I was delivered to the mitochondria. We observed the intracellular trafficking of the carriers, and then measured mitochondrial activity and mtDNA-levels after the delivery of DNase I by the DF-MITO-Porter. The findings confirm that the DF-MITO-Porter effectively delivered the DNase I into the mitochondria, and provides a demonstration of its potential use in therapies that are selective for the mitochondrial genome. [Copyright &y& Elsevier]

Abstract: Mitochondria are the principal producers of energy in cells of higher organisms. It was recently reported that mutations and defects in mitochondrial DNA (mtDNA) are associated with various mitochondrial diseases including a variety of neurodegenerative and neuromuscular diseases. Therefore, an effective mitochondrial gene therapy and diagnosis would be expected to have great medical benefits. To achieve this, therapeutic agents need to be delivered into the innermost mitochondrial space (mitochondrial matrix), which contains the mtDNA pool. We previously reported on the development of MITO-Porter, a liposome-based carrier that introduces macromolecular cargos into mitochondria via membrane fusion. In this study, we provide a demonstration of mitochondrial matrix delivery and the visualization of mitochondrial genes (mtDNA) in living cells using the MITO-Porter. We first prepared MITO-Porter containing encapsulated propidium iodide (PI), a fluorescent dye used to stain nucleic acids to detect mtDNA. We then confirmed the emission of red-fluorescence from PI by conjugation with mtDNA, when the carriers were incubated in the presence of isolated rat liver mitochondria. Finally, intracellular observation by confocal laser scanning microscopy clearly verified that the MITO-Porter delivered PI to the mitochondrial matrix. [Copyright &y& Elsevier]

Abstract: Mitochondrial dysfunction has been implicated in a variety of human disorders—the so-called mitochondrial diseases. Therefore, the organelle is a promising therapeutic drug target. In this review, we describe the key role of mitochondria in living cells, a number of mitochondrial drug delivery systems and mitochondria-targeted therapeutic strategies. In particular, we discuss mitochondrial delivery of macromolecules, such as proteins and nucleic acids. The discussion of protein delivery is limited primarily to the mitochondrial import machinery. In the section on mitochondrial gene delivery and therapy, we discuss mitochondrial diseases caused by mutations in mitochondrial DNA, several gene delivery strategies and approaches to mitochondrial gene therapy. This review also summarizes our current efforts regarding liposome-based delivery system including use of a multifunctional envelope-type nano-device (MEND) and mitochondrial liposome-based delivery as anti-cancer therapies. Furthermore, we introduce the novel MITO-Porter—a liposome-based mitochondrial delivery system that functions using a membrane-fusion mechanism. [Copyright &y& Elsevier]

Abstract: Mitochondria are the principal producers of energy in higher cells. Mitochondrial dysfunction is implicated in a variety of human diseases, including cancer and neurodegenerative disorders. Effective medical therapies for such diseases will ultimately require targeted delivery of therapeutic proteins or nucleic acids to the mitochondria, which will be achieved through innovations in the nanotechnology of intracellular trafficking. Here we describe a liposome-based carrier that delivers its macromolecular cargo to the mitochondrial interior via membrane fusion. These liposome particles, which we call MITO-Porters, carry octaarginine surface modifications to stimulate their entry into cells as intact vesicles (via macropinocytosis). We identified lipid compositions for the MITO-Porter which promote both its fusion with the mitochondrial membrane and the release of its cargo to the intra-mitochondrial compartment in living cells. Thus, the MITO-Porter holds promise as an efficacious system for the delivery of both large and small therapeutic molecules into mitochondria. [Copyright &y& Elsevier]

Mitochondrial transplantation therapy is an innovative strategy for the treatment of mitochondrial dysfunction. The approach has been reported to be useful in the treatment of cardiac ischemic reperfusion injuries in human clinical trials and has also been shown to be useful in animal studies as a method for treating mitochondrial dysfunction in various tissues, including the heart, liver, lungs, and brain. On the other hand, there is no methodology for using preserved mitochondria. Research into the pharmaceutical formulation of mitochondria to promote mitochondrial transplantation therapy as the next step in treating many patients is urgently needed. In this review, we overview previous studies on the therapeutic effects of mitochondrial transplantation. We also discuss studies related to immune responses that occur during mitochondrial transplantation and methods for preserving mitochondria, which are key to their stability as medicines. Finally, we describe research related to mitochondrial targeting drug delivery systems (DDS) and discuss future perspectives of mitochondrial transplantation. [ABSTRACT FROM AUTHOR]

Genetic mutations and defects in mitochondrial DNA (mtDNA) are associated with certain types of mitochondrial dysfunctions, ultimately resulting in the emergence of a variety of human diseases. To achieve an effective mitochondrial gene therapy, it will be necessary to deliver therapeutic agents to the innermost mitochondrial space (the mitochondrial matrix), which contains the mtDNA pool. We recently developed a MITO-Porter, a liposome-based nanocarrier that delivers cargo to mitochondria via a membrane-fusion mechanism. In this chapter, we discuss the methodology used to deliver bioactive molecules to the mitochondrial matrix using a Dual Function (DF)-MITO-Porter, a liposome-based nanocarrier that delivers it cargo by means of a stepwise process, and an evaluation of mtDNA levels and mitochondrial activities in living cells. We also discuss mitochondrial gene silencing by the mitochondrial delivery of antisense RNA oligonucleotide (ASO) targeting mtDNA-encoded mRNA using the MITO-Porter system.

Here, we report on validating a mitochondrial gene therapy by delivering nucleic acids to mitochondria of diseased cells by a MITO-Porter, a liposome-based carrier for mitochondrial delivery. We used cells derived from a patient with a mitochondrial disease with a G625A heteroplasmic mutation in the tRNA Phe of the mitochondrial DNA (mtDNA). It has been reported that some mitochondrial gene diseases are caused by heteroplasmic mutations, in which both mutated and wild-type (WT) genes are present, and the accumulation of pathological mutations leads to serious, intractable, multi-organ diseases. Therefore, the decrease of the mutated gene rate is considered to be a useful gene therapy strategy. To accomplish this, wild-type mitochondrial pre-tRNA Phe (pre-WT-tRNA Phe ), prepared by in vitro transcription, was encapsulated in the MITO-Porter. The pre-WT-tRNA Phe encapsulated in the MITO-Porter was transfected into diseased mitochondrial cells, and the resulting mutant levels were examined by an amplification refractory mutation system (ARMS)-quantitative PCR. The mutation rate of tRNA Phe was decreased, and this therapeutic effect was sustained even on the 8th day after transfection. Furthermore, mitochondrial respiratory activity of the disease cells was increased after the transfection of therapeutic pre-WT-tRNA Phe . These results support the conclusion that the mitochondrial delivery of therapeutic nucleic acids represents a viable strategy for mitochondrial gene therapy., (Copyright © 2020 The Authors. Published by Elsevier Inc. All rights reserved.)

There have been many reports on the relationship between mitochondrial oxidative stress and various types of diseases. This review covers mitochondrial targeting photodynamic therapy and photothermal therapy as a therapeutic strategy for inducing mitochondrial oxidative stress. We also discuss other mitochondrial targeting phototherapeutic methods. In addition, we discuss anti-oxidant therapy by a mitochondrial drug delivery system (DDS) as a therapeutic strategy for suppressing oxidative stress. We also describe cell therapy for reducing oxidative stress in mitochondria. Finally, we discuss the possibilities and problems associated with clinical applications of mitochondrial DDS to regulate mitochondrial oxidative stress.