The Therapeutic Potential of Mitochondria Transplantation Therapy in Neurodegenerative and Neurovascular Disorders

Neurodegenerative and neurovascular disorders affect millions of people worldwide and account for a large and increasing health burden on the general population. Thus, there is a critical need to identify potential disease-modifying treatments that can prevent or slow the disease progression. Mitochondria are highly dynamic organelles and play an important role in energy metabolism and redox homeostasis, and mitochondrial dysfunction threatens cell homeostasis, perturbs energy production, and ultimately leads to cell death and diseases. Impaired mitochondrial function has been linked to the pathogenesis of several human neurological disorders. Given the significant contribution of mitochondrial dysfunction in neurological disorders, there has been considerable interest in developing therapies that can attenuate mitochondrial abnormalities and proffer neuroprotective effects. Unfortunately, therapies that target specific components of mitochondria or oxidative stress pathways have exhibited limited translatability. To this end, mitochondrial transplantation therapy (MTT) presents a new paradigm of therapeutic intervention, which involves the supplementation of healthy mitochondria to replace the damaged mitochondria for the treatment of neurological disorders. Prior studies demonstrated that the supplementation of healthy donor mitochondria to damaged neurons promotes neuronal viability, activity, and neurite growth and has been shown to provide benefits for neural and extra-neural diseases. In this review, we discuss the significance of mitochondria and summarize an overview of the recent advances and development of MTT in neurodegenerative and neurovascular disorders, particularly Parkinson's disease, Alzheimer's disease, and stroke. The significance of MTT is emerging as they meet a critical need to develop a diseasemodifying intervention for neurodegenerative and neurovascular disorders.

Mesenchymal stem cell-mediated transfer of mitochondria: mechanisms and functional impact

There is a steadily growing interest in the use of mitochondria as therapeutic agents. The use of mitochondria derived from mesenchymal stem/stromal cells (MSCs) for therapeutic purposes represents an innovative approach to treat many diseases (immune deregulation, inflammation-related disorders, wound healing, ischemic events, and aging) with an increasing amount of promising evidence, ranging from preclinical to clinical research. Furthermore, the eventual reversal, induced by the intercellular mitochondrial transfer, of the metabolic and pro-inflammatory profile, opens new avenues to the understanding of diseases' etiology, their relation to both systemic and local risk factors, and also leads to new therapeutic tools for the control of inflammatory and degenerative diseases. To this end, we illustrate in this review, the triggers and mechanisms behind the transfer of mitochondria employed by MSCs and the underlying benefits as well as the possible adverse effects of MSCs mitochondrial exchange. We relay the rationale and opportunities for the use of these organelles in the clinic as cell-based product.

Investigation of the effect of isolated mitochondria transplantation on renal ischemia-reperfusion injury in rats

Ischemia/Reperfusion (I/R) injury is clinically important in many surgical practice including kidney transplantation. It is known that mitochondria have a key role in the intracellular and extracellular signaling pathways of ischemia and reperfusion injury. In this respect, we pointed to explore the probable effects of isolated mitochondria transplantation from MSCs (mesenchymal stem cells), to alleviate ischemia/reperfusion-induced renal injury. Experiments were held on the 48 male Sprague Dawley rats. Groups were divided as Control (C1), I/R-Control (C2), Vehicle-1 (V1), Vehicle-2 (V2), Transplantation-1 (T1) and Transplantation-2 (T2) group. Unilaterally nephrectomy was performed in all groups. In the groups except the control, the left kidneys ischemized for 45 min and then reperfusion was carried out. According to the study groups, isolated mitochondria or vehicle infused into the renal cortex and rats were monitored for 48 h. Following that mentioned procedure, animals were sacrificed and biological samples were taken for physiological, histological and biochemical examinations. The results of present study show that mitochondrial transplantation promoted proliferation and regeneration of tubular cells after renal injury. Moreover, mitochondrial transplantation reduced mitochondrial dynamics-DRP-1 fission protein of tubular cells and reversed renal deficits. Mitochondrial transplantation diminished apoptotic markers including TUNEL and Caspase-3 levels in injured renal cells. Our results provide a direct link between mitochondria dysfunction and ischemia/reperfusion-induced renal injury and suggest a therapeutic effect of transplanting isolated mitochondria obtained from MSCs against renal injury.

Mitochondrial aspartate regulates TNF biogenesis and autoimmune tissue inflammation

Misdirected immunity gives rise to the autoimmune tissue inflammation of rheumatoid arthritis, in which excess production of the cytokine tumor necrosis factor (TNF) is a central pathogenic event. Mechanisms underlying the breakdown of self-tolerance are unclear, but T cells in the arthritic joint have a distinctive metabolic signature of ATPlo acetyl-CoAhi proinflammatory effector cells. Here we show that a deficiency in the production of mitochondrial aspartate is an important abnormality in these autoimmune T cells. Shortage of mitochondrial aspartate disrupted the regeneration of the metabolic cofactor nicotinamide adenine dinucleotide, causing ADP deribosylation of the endoplasmic reticulum (ER) sensor GRP78/BiP. As a result, ribosome-rich ER membranes expanded, promoting co-translational translocation and enhanced biogenesis of transmembrane TNF. ERrich T cells were the predominant TNF producers in the arthritic joint. Transfer of intact mitochondria into T cells, as well as supplementation of exogenous aspartate, rescued the mitochondria-instructed expansion of ER membranes and suppressed TNF release and rheumatoid tissue inflammation.

Nasal administration of mitochondria reverses chemotherapy-induced cognitive deficits

Up to seventy-five percent of patients treated for cancer suffer from cognitive deficits which can persist for months to decades, severely impairing quality of life. Although the number of cancer survivors is increasing tremendously, no efficacious interventions exist. Cisplatin, most commonly employed for solid tumors, leads to cognitive impairment including deficits in memory and executive functioning. We recently proposed deficient neuronal mitochondrial function as its underlying mechanism. We hypothesized nasal administration of mitochondria isolated from human mesenchymal stem cells to mice, can reverse cisplatin-induced cognitive deficits. Methods: Puzzle box, novel object place recognition and Y-maze tests were used to assess the cognitive function of mice. Immunofluorescence and high-resolution confocal microscopy were employed to trace the nasally delivered mitochondria and evaluate their effect on synaptic loss. Black Gold II immunostaining was used to determine myelin integrity. Transmission electron microscopy helped determine mitochondrial and membrane integrity of brain synaptosomes. RNA-sequencing was performed to analyse the hippocampal transcriptome. Results: Two nasal administrations of mitochondria isolated from human mesenchymal stem cells to mice, restored executive functioning, working and spatial memory. Confocal imaging revealed nasally delivered mitochondria rapidly arrived in the meninges where they were readily internalized by macrophages. The administered mitochondria also accessed the rostral migratory stream and various other brain regions including the hippocampus where they colocalized with GFAP+ cells. The restoration of cognitive function was associated with structural repair of myelin in the cingulate cortex and synaptic loss in the hippocampus. Nasal mitochondrial donation also reversed the underlying synaptosomal mitochondrial defects. Moreover, transcriptome analysis by RNA-sequencing showed reversal of cisplatin-induced changes in the expression of about seven hundred genes in the hippocampus. Pathway analysis identified Nrf2-mediated response as the top canonical pathway. Conclusion: Our results provide key evidence on the therapeutic potential of isolated mitochondria - restoring both brain structure and function, their capability to enter brain meninges and parenchyma upon nasal delivery and undergo rapid cellular internalization and alter the hippocampal transcriptome. Our data identify nasal administration of mitochondria as an effective strategy for reversing chemotherapy-induced cognitive deficits and restoring brain health, providing promise for the growing population of both adult and pediatric cancer survivors.

Pressure-Driven Mitochondrial Transfer Pipeline Generates Mammalian Cells of Desired Genetic Combinations and Fates

Generating mammalian cells with desired mitochondrial DNA (mtDNA) sequences is enabling for studies of mitochondria, disease modeling, and potential regenerative therapies. MitoPunch, a high-throughput mitochondrial transfer device, produces cells with specific mtDNA-nuclear DNA (nDNA) combinations by transferring isolated mitochondria from mouse or human cells into primary or immortal mtDNA-deficient (ρ0) cells. Stable isolated mitochondrial recipient (SIMR) cells isolated in restrictive media permanently retain donor mtDNA and reacquire respiration. However, SIMR fibroblasts maintain a ρ0-like cell metabolome and transcriptome despite growth in restrictive media. We reprogrammed non-immortal SIMR fibroblasts into induced pluripotent stem cells (iPSCs) with subsequent differentiation into diverse functional cell types, including mesenchymal stem cells (MSCs), adipocytes, osteoblasts, and chondrocytes. Remarkably, after reprogramming and differentiation, SIMR fibroblasts molecularly and phenotypically resemble unmanipulated control fibroblasts carried through the same protocol. Thus, our MitoPunch "pipeline" enables the production of SIMR cells with unique mtDNA-nDNA combinations for additional studies and applications in multiple cell types.

From Cell Entry to Engraftment of Exogenous Mitochondria

Mitochondrial transfer has been recognized to play a role in a variety of processes, ranging from fertilization to cancer and neurodegenerative diseases as well as mammalian horizontal gene transfer. It is achieved through either exogeneous or intercellular mitochondrial transfer. From the viewpoint of evolution, exogeneous mitochondrial transfer is quite akin to the initial process of symbiosis between α-protobacterium and archaea, although the progeny have developed more sophisticated machinery to engulf environmental materials, including nutrients, bacteria, and viruses. A molecular-based knowledge of endocytosis, including macropinocytosis and endosomal escape involving bacteria and viruses, could provide mechanistic insights into exogeneous mitochondrial transfer. We focus on exogeneous mitochondrial transfer in this review to facilitate the clinical development of the use of isolated mitochondria to treat various pathological conditions. Several kinds of novel procedures to enhance exogeneous mitochondrial transfer have been developed and are summarized in this review.

Mitochondrial transplantation ameliorates ischemia/reperfusion-induced kidney injury in rat

No real therapeutic modality is currently available for Acute kidney injury (AKI) and if any, they are mainly supportive in nature. Therefore, developing a new therapeutic strategy is crucial. Mitochondrial dysfunction proved to be a key contributor to renal tubular cell death during AKI. Thus, replacement or augmentation of damaged mitochondria could be a proper target in AKI treatment. Here, in an animal model of AKI, we auto-transplanted normal mitochondria isolated from healthy muscle cells to injured kidney cells through injection to renal artery. The mitochondria transplantation prevented renal tubular cell death, restored renal function, ameliorated kidney damage, improved regenerative potential of renal tubules, and decreased ischemia/reperfusion-induced apoptosis. Although further studies including clinical trials are required in this regard, our findings suggest a novel therapeutic strategy for treatment of AKI. Improved quality of life of patients suffering from renal failure and decreased morbidity and mortality rates would be the potential advantages of this therapeutic strategy.

Mitochondria and Critical Illness

Classically, mitochondria have largely been believed to influence the development of illness by modulating cell metabolism and determining the rate of production of high-energy phosphate compounds (eg, adenosine triphosphate). It is now recognized that this view is simplistic and that mitochondria play key roles in many other processes, including cell signaling, regulating gene expression, modulating cellular calcium levels, and influencing the activation of cell death pathways (eg, caspase activation). Moreover, these multiple mitochondrial functional characteristics are now known to influence the evolution of cellular and organ function in many disease states, including sepsis, ICU-acquired skeletal muscle dysfunction, acute lung injury, acute renal failure, and critical illness-related immune function dysregulation. In addition, diseased mitochondria generate toxic compounds, most notably released mitochondrial DNA, which can act as danger-associated molecular patterns to induce systemic toxicity and damage multiple organs throughout the body. This article reviews these evolving concepts relating mitochondrial function and acute illness. The discussion is organized into four sections: (1) basics of mitochondrial physiology; (2) cellular mechanisms of mitochondrial pathophysiology; (3) critical care disease processes whose initiation and evolution are shaped by mitochondrial pathophysiology; and (4) emerging treatments for mitochondrial dysfunction in critical illness.

New Frontiers in IVF: mtDNA and autologous germline mitochondrial energy transfer

Many infertility specialists support the existence of a relationship between the levels of mitochondrial DNA and the quality of the blastocysts. Despite the extensive use of pre-implantation genetic testing for aneuploidy, a significant percentage of euploid embryos do not implant even though the endometrium is normal. Mitochondrial DNA may be used as a new test in evaluating embryonic vitality.Ovarian aging leads to a decrease in the quantity and quality of oocytes and aged oocytes have a reduced number of mitochondria. Mitochondria are the energy factories of the cells and their lacked could leads to lower fertilization rates and poor embryonic development. Various strategies have been tested to increase the mitochondria quantity and thus improve the quality of oocytes used in in vitro fertilization. Results of ovarian rejuvenation techniques such as autologous mitochondrial transplantation have been controversial. In this review, we describe the state of the art concerning the use of mitochondrial DNA and autologous mitochondrial transplantation as new possibilities to increase success in vitro fertilization.

Mitochondrial Targeted Therapies: Where Do We Stand in Mental Disorders?

The neurobiology of psychiatric disorders is still unclear, although changes in multiple neuronal systems, specifically the dopaminergic, glutamatergic, and gamma-aminobutyric acidergic systems as well as abnormalities in synaptic plasticity and neural connectivity, are currently suggested to underlie their pathophysiology. A growing body of evidence suggests multifaceted mitochondrial dysfunction in mental disorders, which is in line with their role in neuronal activity, growth, development, and plasticity. In this review, we describe the main endeavors toward development of treatments that will enhance mitochondrial function and their transition into clinical use in congenital mitochondrial diseases and chronic disorders such as types 1 and 2 diabetes, cardiovascular disorders, and cancer. In addition, we discuss the relevance of mitochondrial targeted treatments to mental disorders and their potential to become a novel therapeutic strategy that will improve the efficiency of the current treatments.

Ooplasmic transfer in human oocytes: efficacy and concerns in assisted reproduction

BACKGROUND

Ooplasmic transfer (OT) technique or cytoplasmic transfer is an emerging technique with relative success, having a significant status in assisted reproduction. This technique had effectively paved the way to about 30 healthy births worldwide. Though OT has long been invented, proper evaluation of the efficacy and risks associated with this critical technique has not been explored properly until today. This review thereby put emphasis upon the applications, efficacy and adverse effects of OT techniques in human.

MAIN BODY

Available reports published between January 1982 and August 2017 has been reviewed and the impact of OT on assisted reproduction was evaluated. The results consisted of an update on the efficacy and concerns of OT, the debate on mitochondrial heteroplasmy, apoptosis, and risk of genetic and epigenetic alteration.

SHORT CONCLUSION

The application of OT technique in humans demands more clarity and further development of this technique may successfully prove its utility as an effective treatment for oocyte incompetence.

A Mitochondrial Story: Mitochondrial Replacement, Identity and Narrative

Mitochondrial replacement techniques (MRT) are intended to avoid the transmission of mitochondrial diseases from mother to child. MRT represent a potentially powerful new biomedical technology with ethical, policy, economic and social implications. Among other ethical questions raised are concerns about the possible effects on the identity of children born from MRT, their families, and the providers or donors of mitochondria. It has been suggested that MRT can influence identity (i) directly, through altering the genetic makeup and physical characteristics of the child, or (ii) indirectly through changing the child's experience of disease, and by generating novel intrafamilial relationships that shape the sense of self. In this article I consider the plausibility and ethical implications of these proposed identity effects, but I focus instead on a third way in which identity may be affected, through the mediating influence of the wider social world on MRT effects on identity. By taking a narrative approach, and examining the nature and availability of identity narratives, I conclude that while neither direct genetic nor indirect experiential effects can be excluded, social responses to MRT are more likely to have a significant and potentially damaging influence on the generation of MRT children's narratives of identity. This conclusion carries some implications for the collective moral responsibility we hold to ensure that MRT, if implemented, are practised in ethically justifiable ways.

Intracoronary Delivery of Mitochondria to the Ischemic Heart for Cardioprotection

We have previously shown that transplantation of autologously derived, respiration-competent mitochondria by direct injection into the heart following transient ischemia and reperfusion enhances cell viability and contractile function. To increase the therapeutic potential of this approach, we investigated whether exogenous mitochondria can be effectively delivered through the coronary vasculature to protect the ischemic myocardium and studied the fate of these transplanted organelles in the heart. Langendorff-perfused rabbit hearts were subjected to 30 minutes of ischemia and then reperfused for 10 minutes. Mitochondria were labeled with ¹⁸F-rhodamine 6G and iron oxide nanoparticles. The labeled mitochondria were either directly injected into the ischemic region or delivered by vascular perfusion through the coronary arteries at the onset of reperfusion. These hearts were used for positron emission tomography, microcomputed tomography, and magnetic resonance imaging with subsequent microscopic analyses of tissue sections to confirm the uptake and distribution of exogenous mitochondria. Injected mitochondria were localized near the site of delivery; while, vascular perfusion of mitochondria resulted in rapid and extensive dispersal throughout the heart. Both injected and perfused mitochondria were observed in interstitial spaces and were associated with blood vessels and cardiomyocytes. To determine the efficacy of vascular perfusion of mitochondria, an additional group of rabbit hearts were subjected to 30 minutes of regional ischemia and reperfused for 120 minutes. Immediately following regional ischemia, the hearts received unlabeled, autologous mitochondria delivered through the coronary arteries. Autologous mitochondria perfused through the coronary vasculature significantly decreased infarct size and significantly enhanced post-ischemic myocardial function. In conclusion, the delivery of mitochondria through the coronary arteries resulted in their rapid integration and widespread distribution throughout the heart and provided cardioprotection from ischemia-reperfusion injury.

UK's Legalisation of Mitochondrial Donation in IVF Treatment: A Challenge to the International Community or a Promotion of Life-saving Medical Innovation to Be Followed by Others?

Mitochondrial DNA diseases are rare genetic disorders, which can have a devastating effect on the patients' health and well-being. There is no cure for such diseases, although recent experiments suggest that there may be a way to prevent them by genetically altering the eggs or embryos through a procedure known as mitochondrial donation. However, such a procedure not only raises serious safety and ethical concerns, but legal challenges as well, since it involves germline gene modification, which until recently was not legal in the UK or elsewhere. In February 2015, the British Parliament amended the relevant legislation to allow such. a procedure, making the UK the first state to openly challenge the global policy on germline gene modification. The article presents the scientific background to the procedure and discusses the regulatory challenges brought by the first case of its legalisation.

Genes and gestation in Australian regulation of egg donation, surrogacy and mitochondrial donation

This article considers genetic and legal relatedness for the purposes of Australian regulation of egg donation, surrogacy and parentage by examination of that regulation through the lens of mitochondrial (mt) donation. The article addresses whether mt donors would be a child's genetic parents following clinical use in that child's conception should mt donation be legalised for such use in Australia. It then considers how genetic and gestational relatedness are relevant in the discourse around legal parentage following egg donation and surrogacy and argues that the current approach is in need of reform so that intending parents of all children are deemed to be the resulting child's legal parents at birth.

Social and ethical issues in mitochondrial donation

INTRODUCTION OR BACKGROUND

The UK is at the forefront of mitochondrial science and is currently the only country in the world to legalize germ-line technologies involving mitochondrial donation. However, concerns have been raised about genetic modification and the 'slippery slope' to designer babies.

SOURCES OF DATA

This review uses academic articles, newspaper reports and public documents.

AREAS OF AGREEMENT

Mitochondrial donation offers women with mitochondrial disease an opportunity to have healthy, genetically related children.

AREAS OF CONTROVERSY

Key areas of disagreement include safety, the creation of three-parent babies, impact on identity, implications for society, definitions of genetic modification and reproductive choice.

GROWING POINTS

The UK government legalized the techniques in March 2015. Scientific and medical communities across the world followed the developments with interest.

AREAS TIMELY FOR DEVELOPING RESEARCH

It is expected that the first cohort of 'three parent' babies will be born in the UK in 2016. Their health and progress will be closely monitored.

Mitochondrial donation--how many women could benefit?

Mitochondrial disease is maternally inherited and refractory to treatment, but assisted reproduction methods can result in unaffected pregnancies. The authors provide estimates of the number of affected pregnancies per year in the United Kingdom and the United States.

Ethics of mitochondrial therapy for deafness

Mitochondrial therapy may provide the relief to many families with inherited mitochondrial diseases. However, it also has the potential for use in non-fatal disorders such as inherited mitochondrial deafness, providing an option for correction of the deafness using assisted reproductive technology. In this paper we discuss the potential for use in correcting mitochondrial deafness and consider some of the issues for the deaf community.

The commercialization of human eggs in mitochondrial replacement research

After the development of induced pluripotent stem cells (IPSCs) in 2007, the pressure to commercialize women's eggs for stem cell research could have been expected to lessen. However, the pressure to harvest human eggs in large quantities for research has not diminished; rather, it has taken different directions, for example in germline mitochondrial research. Yet there has been little acknowledgement of these technologies' need for human eggs, the possible risks to women and the ethical issues concerning potential exploitation. Rather, there has been a renewed campaign to legalize payment for eggs in research, although the actual scientific advances are at best modest. This article shows why a market in women's eggs is ethically problematic in terms of the doctor's duty to do no harm and the limitations of 'informed' consent.

Ethical considerations, safety precautions and parenthood in legalising mitochondrial donation

This article outlines some of the main ethical considerations specifically relating to legalisation of mitochondrial donation. Safety requirements, were the technique to be legalised, are then discussed, followed by an exploration of parenthood in the context of mitochondrial donation. It is concluded that there are no ethical objections specifically relating to the legalisation of mitochondrial donation, but that various safety precautions must be established prior to its use, including the availability of relevant medical information about the mitochondrial donors to any resultant children. It is also found that introduction of this technique would not necessitate modifications to current British legal definitions of parenthood. However, it is clear that societal attitudes in this area are changing, and it is recommended that this opportunity be taken to review concepts of parenthood, particularly the number of parents a child may have at one time.

Oocyte Mitochondria: Strategies to Improve Embrbryogenesis

Mitochondria play a central role to provide ATP for fertilization and preimplantation embryo development in the ooplasm. The mitochondrial dysfunction of oocyte has been proposed as one of the causes of high levels of developmental retardation and arrest that occur in preimplantation embryos generated using Assisted Reproductive Technology. Cytoplasmic transfer (CT) from a donor to a recipient oocyte has been applied to infertility due to dysfunctional ooplasm, with resulting pregnancies and births. However, neither the efficacy nor safety of this procedure has been appropriately investigated. In order to improve embryogenesis, we observed the mitochondrial distribution in ooplasma under the several conditions using mitochondrial GFP-transgenic mice (mtGFP-tg mice) in which the mitochondria are visualized by GFP. In this report, we will present our research about the mitochondrial distribution in ooplasm during early embryogenesis and the fate of injected donor mitochondria after CT using mtGFP-tg mice. The mitochondria in ooplasm from the germinal vesicle stage to the morula stage were accumulated in the perinuclear region. The mitochondria of the mtGFP-tg mouse oocyte transferred into the wild type mouse embryo could be observed until the blastocysts stage, suggesting that the mtGFP-tg mice oocyte is very useful for visual observation of the mitochondrial distribution in the oocyte, and that the aberrant early developmental competences due to the oocyte mitochondrial dysfunction may be overcome by transferring the "normal" mitochondria.

Role of the mitochondrial genome in assisted reproductive technologies and embryonic stem cell-based therapeutic cloning

Mitochondria play a pivotal role in cellular metabolism and are important determinants of embryonic development. Mitochondrial function and biogenesis rely on an intricate coordination of regulation and expression of nuclear and mitochondrial genes. For example, several nucleus-derived transcription factors, such as mitochondrial transcription factor A, are required for mitochondrial DNA replication. Mitochondrial inheritance is strictly maternal while paternally-derived mitochondria are selectively eliminated during early embryonic cell divisions. However, there are reports from animals as well as human patients that paternal mitochondria can occasionally escape elimination, which in some cases has led to severe pathologies. The resulting existence of different mitochondrial genomes within the same cell has been termed mitochondrial heteroplasmy. The increasing use of invasive techniques in assisted reproduction in humans has raised concerns that one of the outcomes of such techniques is an increase in the incidence of mitochondrial heteroplasmy. Indeed, there is evidence that heteroplasmy is a direct consequence of ooplasm transfer, a technique that was used to 'rescue' oocytes from older women by injecting ooplasm from young oocytes. Mitochondria from donor and recipient were found in varying proportions in resulting children. Heteroplasmy is also a byproduct of nuclear transfer, as has been shown in studies on cloned sheep, cattle and monkeys. As therapeutic cloning will depend on nuclear transfer into oocytes and the subsequent generation of embryonic stem cells from resulting blastocysts, the prospect of mitochondrial heteroplasmy and its potential problems necessitate further studies in this area.

Mitochondria transfer can enhance the murine embryo development

PURPOSE

To evaluate the effect of mitochondrial transfer on embryonic development.

MATERIALS AND METHODS

Mitochondria concentrates were collected from murine hepatocytes and fertilized murine zygotes from young and older mice in the 2PN stage were subjected to mitochondrial transfer and cultured in vitro to evaluate the embryonic development.

RESULTS

After extended in vitro culture, 37.65% and 20.91% embryos from the young mice developed to the blastocyst stage in the injected and control groups respectively, which is statistically significant. There was no difference in terms of hatching rates (1.76% and 1.82% respectively). Zygotes from the older mice (>20 weeks old) that received mitochondrial transfer also had a better developmental outcome than the control group (54.35% and 18.92% developed to morula stage, 43.48% and 8.11% developed to the blastocyst stage respectively), which is statistically significant.

CONCLUSIONS

Our results for the murine model provide direct scientific evidence that mitochondrial transfer improves embryonic development. However, potential risks such as mitochondrial heteroplasmy, nuclear-mitochondrial interaction and epigenetic aspects all deserve further evaluation before mitochondrial transfer is applied clinically.

Effects of Granulosa Cell Mitochondria Transfer on the Early Development of Bovine Embryos In Vitro

The objective of this study was to determine the effect of exogenous mitochondria obtained from granulosa cells on the development of bovine embryos in vitro. We classified cumulus oocyte complexes (COCs) as good (G)- and poor (P)-quality oocytes based on cytoplasmic appearance and cumulus characteristics, and assessed mtDNA copy numbers in the G and P oocytes with real-time polymerase chain reaction (PCR). The mitochondria were isolated by fractionation and suspended in mitochondria injection buffer (MIB). Part one of the experiment consisted of the following treatments: (1) G-oocytes + sperm, (2) P-oocytes + mitochondria + MIB + sperm, (3) P-oocytes + MIB + sperm, and (4) P-oocytes + sperm. In part 2, oocytes were parthenogenetically activated. The treatments were: (1) G-oocytes, (2) P-oocytes + mitochondria + MIB, (3) P-oocytes + MIB, and (4) P-oocytes alone. The results indicated a significant difference in mtDNA copy number between G (361 113 +/- 147 114) and P (198 293 +/- 174 178) oocytes (p < 0.01). The rates of morula, blastocyst, and hatched blastocysts derived from P-oocytes + mitochondria were similar to those of G-oocytes, but significantly higher than P-oocytes without exogenous mitochondria in both the ICSI and parthenogenetic activation experiments. We found no difference in blastomere numbers between G-oocytes and P-oocytes + mitochondria in either experiment, but blastomere numbers in these two groups were significantly higher than in P-oocyte groups without exogenous mitochondria. These data suggest that mtDNA content is very important for early embryo development. Furthermore, the transfer of mitochondria from the same breed may improve embryo quality during preimplantation development.

How to prevent 'half-bastard' progeny? or An alternative for three-parent babies: two-parent babies through transplantation of sperm mitochondria

Body development and activity depend on the level of internal energy generation. Therefore, unaffected, optimally active mitochondria are indispensable in a healthy and vital body. A mutation in the DNA of the semi-autonomous mitochondria (mtDNA) may cause an inheritable insufficiency that is due to decreased energy generation needed for adequate development. Sperm mitochondria will not enter the egg cell during fusion of male and female gametocytes. Since women with mutated mtDNA will increasingly know and realize the effect of such mutation in their own body, they will more often ask for treatment to stop the effect of such inconvenient mutation in their progeny. Thus far, solutions for this problem were thought to be: (i) nucleus transplantation just after fertilization into a nucleus-free egg cell of a second healthy woman and later (ii) transplantation of healthy mitochondria from a second woman into the egg cell before fertilization. Although both transplantations create babies with three, instead of two-parents that have contributed to the genetic content, in case of the newer mitochondria transplantation technique the part of the second woman is somewhat more reduced, but still clearly present. Thus, assisted-reproduction techniques that mix egg cell mitochondria from two women may create not only 'three-parents' babies, but also fears for 'three-parents' babies, since this handling may create non-scientific problems, especially regarding emotional, ethical, religious and juridical aspects of life. Transplantation of healthy sperm mitochondria of the partner into the egg cell with insufficient mitochondria is thought to be the best solution for this problem, since it may create a 'two-parents' instead of a 'three-parents' baby. This only implies that at the moment of (successful) transplantation the biological dogma is broken that mitochondria are maternally inherited: the mitochondria of the maternal line of the woman will have been substituted by the mitochondria of the maternal line of the man.

Assaying the probabilities of obtaining maternally inherited heteroplasmy as the basis for modeling OXPHOS diseases in animals

Gross alterations in cell energy metabolism underlie manifestations of hereditary OXPHOS (oxidative phosphorylation) diseases, many of which depend on proportion of mutant mitochondrial DNA (mtDNA) in tissues. An animal model of OXPHOS disease with maternal inheritance of mitochondrial heteroplasmy might help understanding the peculiarities of abnormal mtDNA distribution and its effect on pre- and postnatal development. Previously we obtained mice that carry human mtDNA in some tissues. It co-existed with murine mtDNA (heteroplasmy) and was transmitted maternally to the progeny of animals developed from zygotes injected with human mitochondria. To analyze the probability of obtaining heteroplasmic mice we increased the number of experiments with early embryos and obtained more specimens from F1. About 33% of zygotes injected with human mtDNA developed into post-implantation embryos (7th-13th days). Lower amount of such developed into neonate mice (ca. 21%). Among post-implantation embryos and in generations F0 and F1 percentages of human mtDNA-carriers were ca. 14-16%. Such percentages are sufficient for modeling maternally inherited heteroplasmy in small animal groups. More data are needed to understand the regularities of anomalous mtDNA distribution among cells and tissues and whether heart and muscles frequently carrying human mtDNA in our experiments are particularly susceptible to heteroplasmy.

Mitochondria directly influence fertilisation outcome in the pig

The mitochondrion is explicitly involved in cytoplasmic regulation and is the cell’s major generator of ATP. Our aim was to determine whether mitochondria alone could influence fertilisation outcome.In vitro, oocyte competence can be assessed through the presence of glucose-6-phosphate dehydrogenase (G6PD) as indicated by the dye, brilliant cresyl blue (BCB). Using porcinein vitrofertilisation (IVF), we have assessed oocyte maturation, cytoplasmic volume, fertilisation outcome, mitochondrial number as determined by mtDNA copy number, and whether mitochondria are uniformly distributed between blastomeres of each embryo. After staining with BCB, we observed a significant difference in cytoplasmic volume between BCB positive (BCB+) and BCB negative (BCB−) oocytes. There was also a significant difference in mtDNA copy number between fertilised and unfertilised oocytes and unequal mitochondrial segregation between blastomeres during early cleavage stages. Furthermore, we have supplemented BCB−oocytes with mitochondria from maternal relatives and observed a significant difference in fertilisation outcomes following both IVF and intracytoplasmic sperm injection (ICSI) between supplemented, sham-injected and non-treated BCB−oocytes. We have therefore demonstrated a relationship between oocyte maturity, cytoplasmic volume, and fertilisation outcome and mitochondrial content. These data suggest that mitochondrial number is important for fertilisation outcome and embryonic development. Furthermore, a mitochondrial pre-fertilisation threshold may ensure that, as mitochondria are diluted out during post-fertilisation cleavage, there are sufficient copies of mtDNA per blastomere to allow transmission of mtDNA to each cell of the post-implantation embryo after the initiation of mtDNA replication during the early postimplantation stages.

Mitochondria dysfunction of Alzheimer's disease cybrids enhances Abeta toxicity

Alzheimer's disease (AD) brain reveals high rates of oxygen consumption and oxidative stress, altered antioxidant defences, increased oxidized polyunsaturated fatty acids, and elevated transition metal ions. Mitochondrial dysfunction in AD is perhaps relevant to these observations, as such may contribute to neurodegenerative cell death through the formation of reactive oxygen species (ROS) and the release of molecules that initiate programmed cell death pathways. In this study, we analyzed the effects of beta-amyloid peptide (Abeta) on human teratocarcinoma (NT2) cells expressing endogenous mitochondrial DNA (mtDNA), mtDNA from AD subjects (AD cybrids), and mtDNA from age-matched control subjects (control cybrids). In addition to finding reduced cytochrome oxidase activity, elevated ROS, and reduced ATP levels in the AD cybrids, when these cell lines were exposed to Abeta 1-40 we observed excessive mitochondrial membrane potential depolarization, increased cytoplasmic cytochrome c, and elevated caspase-3 activity. When exposed to Abeta, events associated with programmed cell death are activated in AD NT2 cybrids to a greater extent than they are in control cybrids or the native NT2 cell line, suggesting a role for mtDNA-derived mitochondrial dysfunction in AD degeneration.

Apoptotic cell death of cybrid cells bearing Leber's hereditary optic neuropathy mutations is caspase independent

Leber's hereditary optic neuropathy (LHON) is a maternally inherited disease characterized by selective death of retinal ganglion cells. Three pathogenic mtDNA point mutations induce an impairment of oxidative phosphorylation. We have investigated whether the release of cytochrome c during incubation of LHON cybrids in galactose medium leads to activation of the executive caspase-3 and to alteration of the energetic status of cells. From our research, it can be concluded that apoptotic cell death induced in LHON cybrid by galactose medium is caspase independent. It remains to be explained how the significant fragmentation of intranucleosomal DNA observed in LHON cybrids could also occur in the absence of caspase activation.