Direct administration of mesenchymal stem cell-derived mitochondria improves cardiac function after infarction via ameliorating endothelial senescence

Mitochondrial transplantation: A promising therapy for mitochondrial disorders

As a vital energy source for cellular metabolism and tissue survival, the mitochondrion can undergo morphological or positional change and even shuttle between cells in response to various stimuli and energy demands. Multiple human diseases are originated from mitochondrial dysfunction, but the curative succusses by traditional treatments are limited. Mitochondrial transplantation therapy (MTT) is an innovative therapeutic approach that is to deliver the healthy mitochondria either derived from normal cells or reassembled through synthetic biology into the cells and tissues suffering from mitochondrial damages and finally replace their defective mitochondria and restore their function. MTT has already been under investigation in clinical trials for cardiac ischemia-reperfusion injury and given an encouraging performance in animal models of numerous fatal critical diseases including central nervous system disorders, cardiovascular diseases, inflammatory conditions, cancer, renal injury, and pulmonary damage. This review article summarizes the mechanisms and strategies of mitochondrial transfer and the MTT application for types of mitochondrial diseases, and discusses the potential challenge in MTT clinical application, aiming to exhibit the good therapeutic prospects of MTTs in clinics.

Relevance of real-time analyzers to determine mitochondrial quality in endothelial cells and oxidative stress in preeclampsia

Oxidative stress and mitochondrial dysfunction are important elements for the pathophysiology of preeclampsia (PE), a multisystemic hypertensive syndrome of pregnancy, characterized by endothelial dysfunction and responsible for a large part of maternal and fetal morbidity and mortality worldwide. Researchers have dedicated their efforts to unraveling the intricate ways in which certain molecules influence both energy metabolism and oxidative stress. Exploring established methodologies from existing literature, shows that these investigations predominantly focus on the placenta, identified as a pivotal source that drives the changes observed in the disease. In this review, we discuss the role of oxidative stress in pathophysiology of PE, as well as metabolic/endothelial dysfunction. We further discuss the use of seahorse analyzers to study real-time bioenergetics of endothelial cells. Although the benefits are clear, few studies have presented results using this method to assess mitochondrial metabolism in these cells. We performed a search on MEDLINE/PubMed using the terms "Seahorse assay and endothelial dysfunction in HUVEC" as well as "Seahorse assay and preeclampsia". From our research, we selected 16 original peer-review papers for discussion. Notably, the first search retrieved studies involving Human Umbilical Vein Endothelial Cells (HUVECs) but none investigating bioenergetics in PE while the second search retrieved studies exploring the technique in PE but none of the studies used HUVECs. Additional studies are required to investigate real-time mitochondrial bioenergetics in PE. Clearly, there is a need for more complete studies to examine the nuances of mitochondrial bioenergetics, focusing on the contributions of HUVECs in the context of PE.

Mitochondria transplantation alleviates cardiomyocytes apoptosis through inhibiting AMPKα-mTOR mediated excessive autophagy

The disruption of mitochondria homeostasis can impair the contractile function of cardiomyocytes, leading to cardiac dysfunction and an increased risk of heart failure. This study introduces a pioneering therapeutic strategy employing mitochondria derived from human umbilical cord mesenchymal stem cells (hu-MSC) (MSC-Mito) for heart failure treatment. Initially, we isolated MSC-Mito, confirming their functionality. Subsequently, we monitored the process of single mitochondria transplantation into recipient cells and observed a time-dependent uptake of mitochondria in vivo. Evidence of human-specific mitochondrial DNA (mtDNA) in murine cardiomyocytes was observed after MSC-Mito transplantation. Employing a doxorubicin (DOX)-induced heart failure model, we demonstrated that MSC-Mito transplantation could safeguard cardiac function and avert cardiomyocyte apoptosis, indicating metabolic compatibility between hu-MSC-derived mitochondria and recipient mitochondria. Finally, through RNA sequencing and validation experiments, we discovered that MSC-Mito transplantation potentially exerted cardioprotection by reinstating ATP production and curtailing AMPKα-mTOR-mediated excessive autophagy.

Mitochondrial transfer mediates endothelial cell engraftment through mitophagy

Ischaemic diseases such as critical limb ischaemia and myocardial infarction affect millions of people worldwide1. Transplanting endothelial cells (ECs) is a promising therapy in vascular medicine, but engrafting ECs typically necessitates co-transplanting perivascular supporting cells such as mesenchymal stromal cells (MSCs), which makes clinical implementation complicated2,3. The mechanisms that enable MSCs to facilitate EC engraftment remain elusive. Here we show that, under cellular stress, MSCs transfer mitochondria to ECs through tunnelling nanotubes, and that blocking this transfer impairs EC engraftment. We devised a strategy to artificially transplant mitochondria, transiently enhancing EC bioenergetics and enabling them to form functional vessels in ischaemic tissues without the support of MSCs. Notably, exogenous mitochondria did not integrate into the endogenous EC mitochondrial pool, but triggered mitophagy after internalization. Transplanted mitochondria co-localized with autophagosomes, and ablation of the PINK1-Parkin pathway negated the enhanced engraftment ability of ECs. Our findings reveal a mechanism that underlies the effects of mitochondrial transfer between mesenchymal and endothelial cells, and offer potential for a new approach for vascular cell therapy.

Angiogenic activity of mitochondria; beyond the sole bioenergetic organelle

Angiogenesis is a complex process that involves the expansion of the pre-existing vascular plexus to enhance oxygen and nutrient delivery and is stimulated by various factors, including hypoxia. Since the process of angiogenesis requires a lot of energy, mitochondria play an important role in regulating and promoting this phenomenon. Besides their roles as an oxidative metabolism base, mitochondria are potential bioenergetics organelles to maintain cellular homeostasis via sensing alteration in oxygen levels. Under hypoxic conditions, mitochondria can regulate angiogenesis through different factors. It has been indicated that unidirectional and bidirectional exchange of mitochondria or their related byproducts between the cells is orchestrated via different intercellular mechanisms such as tunneling nanotubes, extracellular vesicles, and gap junctions to maintain the cell homeostasis. Even though, the transfer of mitochondria is one possible mechanism by which cells can promote and regulate the process of angiogenesis under reperfusion/ischemia injury. Despite the existence of a close relationship between mitochondrial donation and angiogenic response in different cell types, the precise molecular mechanisms associated with this phenomenon remain unclear. Here, we aimed to highlight the possible role of mitochondria concerning angiogenesis, especially the role of mitochondrial transport and the possible relation of this transfer with autophagy, the housekeeping phenomenon of cells, and angiogenesis.

The power and potential of mitochondria transfer

Mitochondria are believed to have originated through an ancient endosymbiotic process in which proteobacteria were captured and co-opted for energy production and cellular metabolism. Mitochondria segregate during cell division and differentiation, with vertical inheritance of mitochondria and the mitochondrial DNA genome from parent to daughter cells. However, an emerging body of literature indicates that some cell types export their mitochondria for delivery to developmentally unrelated cell types, a process called intercellular mitochondria transfer. In this Review, we describe the mechanisms by which mitochondria are transferred between cells and discuss how intercellular mitochondria transfer regulates the physiology and function of various organ systems in health and disease. In particular, we discuss the role of mitochondria transfer in regulating cellular metabolism, cancer, the immune system, maintenance of tissue homeostasis, mitochondrial quality control, wound healing and adipose tissue function. We also highlight the potential of targeting intercellular mitochondria transfer as a therapeutic strategy to treat human diseases and augment cellular therapies.

Therapeutic Effects of Mesenchymal Stromal Cells Require Mitochondrial Transfer and Quality Control

Due to their beneficial effects in an array of diseases, Mesenchymal Stromal Cells (MSCs) have been the focus of intense preclinical research and clinical implementation for decades. MSCs have multilineage differentiation capacity, support hematopoiesis, secrete pro-regenerative factors and exert immunoregulatory functions promoting homeostasis and the resolution of injury/inflammation. The main effects of MSCs include modulation of immune cells (macrophages, neutrophils, and lymphocytes), secretion of antimicrobial peptides, and transfer of mitochondria (Mt) to injured cells. These actions can be enhanced by priming (i.e., licensing) MSCs prior to exposure to deleterious microenvironments. Preclinical evidence suggests that MSCs can exert therapeutic effects in a variety of pathological states, including cardiac, respiratory, hepatic, renal, and neurological diseases. One of the key emerging beneficial actions of MSCs is the improvement of mitochondrial functions in the injured tissues by enhancing mitochondrial quality control (MQC). Recent advances in the understanding of cellular MQC, including mitochondrial biogenesis, mitophagy, fission, and fusion, helped uncover how MSCs enhance these processes. Specifically, MSCs have been suggested to regulate peroxisome proliferator-activated receptor-gamma coactivator 1 alpha (PGC1α)-dependent biogenesis, Parkin-dependent mitophagy, and Mitofusins (Mfn1/2) or Dynamin Related Protein-1 (Drp1)-mediated fission/fusion. In addition, previous studies also verified mitochondrial transfer from MSCs through tunneling nanotubes and via microvesicular transport. Combined, these effects improve mitochondrial functions, thereby contributing to the resolution of injury and inflammation. Thus, uncovering how MSCs affect MQC opens new therapeutic avenues for organ injury, and the transplantation of MSC-derived mitochondria to injured tissues might represent an attractive new therapeutic approach.

The beneficial effects of mesenchymal stem cells and their exosomes on myocardial infarction and critical considerations for enhancing their efficacy

Mesenchymal stem cells (MSCs) are multipotent stromal cells with regenerative, anti-inflammatory, and immunomodulatory properties. MSCs and their exosomes significantly improved structural and functional alterations after myocardial infarction (MI) in preclinical studies and clinical trials. By reprograming intracellular signaling pathways, MSCs attenuate inflammatory response, oxidative stress, apoptosis, pyroptosis, and endoplasmic reticulum (ER) stress and improve angiogenesis, mitochondrial biogenesis, and myocardial remodeling after MI. MSC-derived exosomes contain a mixture of non-coding RNAs, growth factors, anti-inflammatory mediators, and anti-fibrotic factors. Although primary results from clinical trials were promising, greater efficacies can be achieved by controlling several modifiable factors. The optimum timing of transplantation, route of administration, origin of MSCs, number of doses, and number of cells per dose need to be further investigated by future studies. Newly, highly effective MSC delivery systems have been developed to improve the efficacy of MSCs and their exosomes. Moreover, MSCs can be more efficacious after being pretreated with non-coding RNAs, growth factors, anti-inflammatory or inflammatory mediators, and hypoxia. Similarly, viral vector-mediated overexpression of particular genes can augment the protective effects of MSCs on MI. Therefore, future clinical trials must consider these advances in preclinical studies to properly reflect the efficacy of MSCs or their exosomes for MI.