Donation of mitochondria by iPSC-derived mesenchymal stem cells protects retinal ganglion cells against mitochondrial complex I defect-induced degeneration

Small extracellular vesicles derived from human induced pluripotent stem cell-differentiated neural progenitor cells mitigate retinal ganglion cell degeneration in a mouse model of optic nerve injury

JOURNAL/nrgr/04.03/01300535-202502000-00034/figure1/v/2024-05-28T214302Z/r/image-tiff Several studies have found that transplantation of neural progenitor cells (NPCs) promotes the survival of injured neurons. However, a poor integration rate and high risk of tumorigenicity after cell transplantation limits their clinical application. Small extracellular vesicles (sEVs) contain bioactive molecules for neuronal protection and regeneration. Previous studies have shown that stem/progenitor cell-derived sEVs can promote neuronal survival and recovery of neurological function in neurodegenerative eye diseases and other eye diseases. In this study, we intravitreally transplanted sEVs derived from human induced pluripotent stem cells (hiPSCs) and hiPSCs-differentiated NPCs (hiPSC-NPC) in a mouse model of optic nerve crush. Our results show that these intravitreally injected sEVs were ingested by retinal cells, especially those localized in the ganglion cell layer. Treatment with hiPSC-NPC-derived sEVs mitigated optic nerve crush-induced retinal ganglion cell degeneration, and regulated the retinal microenvironment by inhibiting excessive activation of microglia. Component analysis further revealed that hiPSC-NPC derived sEVs transported neuroprotective and anti-inflammatory miRNA cargos to target cells, which had protective effects on RGCs after optic nerve injury. These findings suggest that sEVs derived from hiPSC-NPC are a promising cell-free therapeutic strategy for optic neuropathy.

Mitochondrial transfer between BMSCs and Müller promotes mitochondrial fusion and suppresses gliosis in degenerative retina

Mitochondrial dysfunction and Müller cells gliosis are significant pathological characteristics of retinal degeneration (RD) and causing blinding. Stem cell therapy is a promising treatment for RD, the recently accepted therapeutic mechanism is cell fusion induced materials transfer. However, whether materials including mitochondrial transfer between grafted stem cells and recipient's cells contribute to suppressing gliosis and mechanism are unclear. In present study, we demonstrated that bone marrow mesenchymal stem cells (BMSCs) transferred mitochondria to Müller cells by cell fusion and tunneling nanotubes. BMSCs-derived mitochondria (BMSCs-mito) were integrated into mitochondrial network of Müller cells, improving mitochondrial function, reducing oxidative stress and gliosis, which protected visual function partially in the degenerative rat retina. RNA sequencing analysis revealed that BMSCs-mito increased mitochondrial DNA (mtDNA) content and facilitated mitochondrial fusion in damaged Müller cells. It suggests that mitochondrial transfer from BMSCs remodels Müller cells metabolism and suppresses gliosis; thus, delaying the degenerative progression of RD.

Horizontal mitochondrial transfer as a novel bioenergetic tool for mesenchymal stromal/stem cells: molecular mechanisms and therapeutic potential in a variety of diseases

Intercellular mitochondrial transfer (MT) is a newly discovered form of cell-to-cell signalling involving the active incorporation of healthy mitochondria into stressed/injured recipient cells, contributing to the restoration of bioenergetic profile and cell viability, reduction of inflammatory processes and normalisation of calcium dynamics. Recent evidence has shown that MT can occur through multiple cellular structures and mechanisms: tunneling nanotubes (TNTs), via gap junctions (GJs), mediated by extracellular vesicles (EVs) and other mechanisms (cell fusion, mitochondrial extrusion and migrasome-mediated mitocytosis) and in different contexts, such as under physiological (tissue homeostasis and stemness maintenance) and pathological conditions (hypoxia, inflammation and cancer). As Mesenchimal Stromal/ Stem Cells (MSC)-mediated MT has emerged as a critical regulatory and restorative mechanism for cell and tissue regeneration and damage repair in recent years, its potential in stem cell therapy has received increasing attention. In particular, the potential therapeutic role of MSCs has been reported in several articles, suggesting that MSCs can enhance tissue repair after injury via MT and membrane vesicle release. For these reasons, in this review, we will discuss the different mechanisms of MSCs-mediated MT and therapeutic effects on different diseases such as neuronal, ischaemic, vascular and pulmonary diseases. Therefore, understanding the molecular and cellular mechanisms of MT and demonstrating its efficacy could be an important milestone that lays the foundation for future clinical trials.

Optic nerve regeneration: Potential treatment approaches

The optic nerve, predominantly constituted by the axons of retinal ganglion cells (RGCs), lacks the ability to regenerate and re-establish function after injury. RGCs are crucial for visual function, and thus, RGC death contributes to the development of numerous progressive neurodegenerative optic neuropathies including glaucoma, ischemic optic neuropathy, and optic neuritis. Regenerating optic nerve axons poses numerous challenges due to factors such as the intricate and inhibitory conditions that exist within their environment, intrinsic breaks to regeneration, and the geometric tortuosity that offers physical hindrance to axon growth. However, recent research advancements offer hope for clinically meaningful regeneration for those who suffer from optic nerve damage. In this review, we highlight the current treatment approaches for optic nerve axon regeneration.

Recent advances in mesenchymal stem cell therapy for myocardial infarction

Myocardial infarction refers to the ischemic necrosis of myocardium, characterized by a sharp reduction or interruption of blood flow in the coronary arteries due to the coronary artery occlusion, resulting in severe and prolonged ischemia in the corresponding myocardium and ultimately leading to ischemic necrosis of the myocardium. Given its high risk, it is considered as one of the most serious health threats today. In current clinical practice, multiple approaches have been explored to diminish myocardial oxygen consumption and alleviate symptoms, but notable success remains elusive. Accumulated clinical evidence has showed that the implantation of mesenchymal stem cell for treating myocardial infarction is both effective and safe. Nevertheless, there persists controversy and variability regarding the standardizing MSC transplantation protocols, optimizing dosage, and determining the most effective routes of administration. Addressing these remaining issues will pave the way of integration of MSCs as a feasible mainstream cardiac treatment.

Endometrial organoids: a reservoir of functional mitochondria for uterine repair

Background: Asherman's syndrome (AS) is a dreadful gynecological disorder of the uterus characterized by intrauterine adhesion with severe fibrotic lesions, resulting in a damaged basalis layer with infertility. Despite extensive research on overcoming AS, evidence-based effective and reproducible treatments to improve the structural and functional morphology of the AS endometrium have not been established. Methods: Endometrial organoids generated from human or mouse endometrial tissues were transplanted into the uterine cavity of a murine model of AS to evaluate their transplantable feasibility to improve the AS uterine environment. The successful engraftment of organoid was confirmed by detection of human mitochondria and cytosol (for human endometrial organoid) or enhanced green fluorescent protein signals (for mouse endometrial organoid) in the recipient endometrium. The therapeutic effects mediated by organoid transplantation were examined by the measurements of fibrotic lesions, endometrial receptivity and angiogenesis, and fertility assessment by recording the number of implantation sites and weighing the fetuses and placenta. To explore the cellular and molecular mechanisms underlying the recovery of AS endometrium, we evaluated the status of mitochondrial movement and biogenetics in organoid transplanted endometrium. Results: Successfully engrafted endometrial organoids with similar morphological and molecular features to the parental tissues dramatically repaired the AS-induced damaged endometrium, significantly reducing fibrotic lesions and increasing fertility outcomes in mice. Moreover, dysfunctional mitochondria in damaged tissues, which we propose might be a key cellular feature of the AS endometrium, was fully recovered by functional mitochondria transferred from engrafted endometrial organoids. Endometrial organoid-originating mitochondria restored excessive collagen accumulation in fibrotic lesions and shifted uterine metabolic environment to levels observed in the normal endometrium. Conclusions: Our findings suggest that endometrial organoid-originating mitochondria might be key players to mediate uterine repair resulting in fertility enhancement by recovering abrogated metabolic circumstance of the endometrium with AS. Further studies addressing the clinical applicability of endometrial organoids may aid in identifying new therapeutic strategies for infertility in patients with AS.

Mesenchymal Stem Cell-Derived Mitochondria Enhance Extracellular Matrix-Derived Grafts for the Repair of Nerve Defect

Peripheral nerve injuries (PNI) can lead to mitochondrial dysfunction and energy depletion within the affected microenvironment. The objective is to investigate the potential of transplanting mitochondria to reshape the neural regeneration microenvironment. High-purity functional mitochondria with an intact structure are extracted from human umbilical cord-derived mesenchymal stem cells (hUCMSCs) using the Dounce homogenization combined with ultracentrifugation. Results show that when hUCMSC-derived mitochondria (hUCMSC-Mitos) are cocultured with Schwann cells (SCs), they promote the proliferation, migration, and respiratory capacity of SCs. Acellular nerve allografts (ANAs) have shown promise in nerve regeneration, however, their therapeutic effect is not satisfactory enough. The incorporation of hUCMSC-Mitos within ANAs has the potential to remodel the regenerative microenvironment. This approach demonstrates satisfactory outcomes in terms of tissue regeneration and functional recovery. Particularly, the use of metabolomics and bioenergetic profiling is used for the first time to analyze the energy metabolism microenvironment after PNI. This remodeling occurs through the enhancement of the tricarboxylic acid cycle and the regulation of associated metabolites, resulting in increased energy synthesis. Overall, the hUCMSC-Mito-loaded ANAs exhibit high functionality to promote nerve regeneration, providing a novel regenerative strategy based on improving energy metabolism for neural repair.

Leber's hereditary optic neuropathy: Update on the novel genes and therapeutic options

A maternal inheritance disorder called Leber's hereditary optic neuropathy (LHON) is the most common primary mitochondrial deoxyribonucleic acid (DNA) disorder. In most studies, there are more male patients than female patients, which contradicts the usual pattern in mitochondrial hereditary diseases. This suggests that nuclear DNA (nDNA) may influence the degeneration of retinal ganglion cells (RGCs) in LHON. The primary cause of this is dysfunction in complex I of the electron transport chain, leading to ineffective adenosine triphosphate (ATP) production. In addition to MT-ND4 or MT-ND1 mutations, genes such as PRICKLE3 , YARS2 , and DNAJC30 , which come from nDNA, also play a role in LHON. These three genes affect the electron chain transport differently. PRICKLE3 interacts with ATP synthase (complex V) at Xp11.23, while YARS2 is a tyrosyl-tRNA synthetase 2 involved in mitochondria . DNAJC30 mutations result in autosomal recessive LHON (arLHON). Understanding how genes impact the disease is crucial for developing new treatments. Idebenone has been approved for treating LHON and has shown safety and efficacy in clinical trials. Mesenchymal stem cell-based therapy has also emerged as a potential treatment for LHON by transferring mitochondria into target cells. Gene therapy research focuses on specific gene mutations, and the wild-type ND4 gene target in the adeno-associated viruses (AAV) vector has shown promise in clinical trials as a potential treatment for LHON.

Uncovering the Genetics and Physiology behind Optic Neuritis

Optic neuritis (ON) is an inflammatory condition affecting the optic nerve, leading to vision impairment and potential vision loss. This manuscript aims to provide a comprehensive review of the current understanding of ON, including its definition, epidemiology, physiology, genetics, molecular pathways, therapy, ongoing clinical studies, and future perspectives. ON is characterized by inflammation of the optic nerve, often resulting from an autoimmune response. Epidemiological studies have shown a higher incidence in females and an association with certain genetic factors. The physiology of ON involves an immune-mediated attack on the myelin sheath surrounding the optic nerve, leading to demyelination and subsequent impairment of nerve signal transmission. This inflammatory process involves various molecular pathways, including the activation of immune cells and the release of pro-inflammatory cytokines. Genetic factors play a significant role in the susceptibility to ON. Several genes involved in immune regulation and myelin maintenance have been implicated in the disease pathogenesis. Understanding the genetic basis can provide insights into disease mechanisms and potential therapeutic targets. Therapy for ON focuses on reducing inflammation and promoting nerve regeneration. Future perspectives involve personalized medicine approaches based on genetic profiling, regenerative therapies to repair damaged myelin, and the development of neuroprotective strategies. Advancements in understanding molecular pathways, genetics, and diagnostic tools offer new opportunities for targeted therapies and improved patient outcomes in the future.

Targeting Mitochondrial Dysfunction and Oxidative Stress to Prevent the Neurodegeneration of Retinal Ganglion Cells

The imbalance of redox homeostasis contributes to neurodegeneration, including that related to the visual system. Mitochondria, essential in providing energy and responsible for several cell functions, are a significant source of reactive oxygen and/or nitrogen species, and they are, in turn, sensitive to free radical imbalance. Dysfunctional mitochondria are implicated in the development and progression of retinal pathologies and are directly involved in retinal neuronal degeneration. Retinal ganglion cells (RGCs) are higher energy consumers susceptible to mitochondrial dysfunctions that ultimately cause RGC loss. Proper redox balance and mitochondrial homeostasis are essential for maintaining healthy retinal conditions and inducing neuroprotection. In this respect, the antioxidant treatment approach is effective against neuronal oxidative damage and represents a challenge for retinal diseases. Here, we highlighted the latest findings about mitochondrial dysfunction in retinal pathologies linked to RGC degeneration and discussed redox-related strategies with potential neuroprotective properties.

Mitochondrial transfer between cell crosstalk - An emerging role in mitochondrial quality control

Intercellular signaling and component conduction are essential for multicellular organisms' homeostasis, and mitochondrial transcellular transport is a key example of such cellular component exchange. In physiological situations, mitochondrial transfer is linked with biological development, energy coordination, and clearance of harmful components, remarkably playing important roles in maintaining mitochondrial quality. Mitochondria are engaged in many critical biological activities, like oxidative metabolism and biomolecular synthesis, and are exclusively prone to malfunction in pathological processes. Importantly, severe mitochondrial damage will further amplify the defects in the mitochondrial quality control system, which will mobilize more active mitochondrial transfer, replenish exogenous healthy mitochondria, and remove endogenous damaged mitochondria to facilitate disease outcomes. This review explores intercellular mitochondrial transport in cells, its role in cellular mitochondrial quality control, and the linking mechanisms in cellular crosstalk. We also describe advances in therapeutic strategies for diseases that target mitochondrial transfer.

Current trends and promising clinical utility of IPSC-derived MSC (iMSC)

Mesenchymal stem cells (MSCs) differentiated from human induced pluripotent stem cells (iPSC) or induced MSC (iMSCs) are expected to address issues of scalability and safety as well as the difficulty in producing homogenous clinical grade MSCs as demonstrated by the promising outcomes from preclinical and clinical trials, currently ongoing. The assessment of iMSCs based in vitro and in vivo studies have thus far showed more superior performance as compared to that of the primary or native human MSCs, in terms of cell proliferation, expansion capacity, immunomodulation properties as well as the influence of paracrine signaling and exosomal influence in cell-cell interaction. In this chapter, an overview of current well-established methods in generating a sustainable source of iMSCs involving well defined culture media is discussed followed by the properties of iMSC as compared to that of MSC and its promising prospects for continuous development into potential clinical grade applications.

Tunneling nanotubes-based intercellular mitochondrial trafficking as a novel therapeutic target in dry eye

Cell-to-cell mitochondria transfer via tunneling nanotubes (TNTs) has recently been revealed as a spontaneous way to protect damaged cells. Previously, we have reported mesenchymal stem cells (MSCs) can rescue retinal ganglion cell and corneal epithelium through intercellular mitochondrial trafficking. Mitochondrial damage and oxidative stress in corneal epithelial cells are vital in dry eye disease (DED). However, whether intercellular mitochondrial transfer is involved in the pathological and repair process of DED is currently unknown. Therefore, in this study, we designed a coculture system to evaluate the role of intercellular mitochondrial transfer between human corneal epithelial cells (CEC) in DED. In addition, we successfully discovered the ROCK inhibitor, Y-27632 as an intensifier to improve the efficiency of intercellular mitochondrial transport. As expected, the enhanced mitochondrial transfer promotes the regeneration of CECs. Moreover, through further exploration of mechanisms, it was demonstrated that F-actin-mediated cell morphological changes and cytoskeletal remodeling may be potential mechanisms for Y-27632 to induce mitochondrial metastasis. In conclusion, we established a new method for cell repair in DED that healthy CEC offered mitochondria to damaged CEC, providing a new insight into the cellular mechanism of corneal epithelium homeostatic regenerative therapeutics in DED.

Screening of the best time window for MSC transplantation to treat acute myocardial infarction with SDF-1α antibody-loaded targeted ultrasonic microbubbles: An in vivo study in miniswine

The present study aimed to screen the best time window for the transplantation of bone marrow mesenchymal stem cells (MSCs) after acute myocardial infarction (MI) through targeted ultrasound microbubbles loaded with SDF-1α antibody. Thirty-six MI miniswine were randomly divided into six experimental groups according to the duration after infarction (1 day, 3 days, 1 week, 2 weeks, 3 weeks, and 4 weeks after infarction). MSCs were labeled with BrdU and then injected through the coronary artery in the stem cell transplantation group to detect the number of transplanted MSCs at different time points after MI. Three miniswine were randomly selected as the control group (sham operation: open chest without ligation of the coronary artery). All SDF-1α groups and control groups were injected with a targeted microbubble ultrasound contrast agent. The values of the myocardial perfusion parameters (A, β, and A × β) were determined. A _T, β _T, and (A × β)_T varied with time and peaked 1 week after MI (P < 0.05). The number of transplanted stem cells in the myocardium through coronary injection of MSCs at 1 week was the greatest and consistent with the changing tendency of A _T, β _T, and (A × β)_T (r = 0.658, 0.778, 0.777, P < 0.05). β _T(X), (A × β)_T(X), and the number of transplanted stem cells was used to establish the regression equation as follows: Y = 36.11 + 17.601X; Y = 50.023 + 3.348X (R ² = 0.605, 0.604, P < 0.05). The best time window for transplanting stem cells was 1 week after MI. The myocardial perfusion parameters of the SDF-1α targeted contrast agent can be used to predict the number of transplanted stem cells in the myocardial tissue.

Advantages of mesenchymal stem cell over the other stem cells

A stem cell is a particular group of cells that has the extraordinary potential to convert within the body into particular cell types. They are used to regenerate tissues and cells in the body that have been damaged or destroyed by the disease. Stem cells come in three different varieties: adult stem cells, embryonic stem cells and induced pluripotent stem cells (iPSCs). Embryonic stem cells have a high chance of immune rejection and also have ethical dilemmas and iPSCs have genetic instability. Adult stem cells are difficult to analyze and extract for research since they are frequently insufficient in native tissues. However, mesenchymal stem cells (MSC) one of the categories of adult stem cells are stromal cells with a variety of potentials that can differentiate into a wide range of cell types. MSCs can be transplanted into a variety of people without worrying about rejection because they have demonstrated the ability to prevent an adverse reaction from the immune system. These transplants have powerful anti-inflammatory and immunosuppressive effects and greatly enhance the body's inherent healing capacity. While MSCs do not offer treatment for illnesses, the idea behind them is to enable the body to recover sufficiently for a protracted reduction in symptoms. In many cases, this is sufficient to significantly enhance the patient's well-being. Inspite of several advantages some potential long-term concerns connected to MSC therapy are maldifferentiation, immunosuppression and cancerous tumor growth. In this review, we will compare the mesenchymal stem cells with other stem cells with respect to the source of origin, their properties and therapeutic applications, and discuss the MSC's disadvantages.

Emerging roles of mitochondria in animal regeneration

The regeneration capacity after an injury is critical to the survival of living organisms. In animals, regeneration ability can be classified into five primary types: cellular, tissue, organ, structure, and whole-body regeneration. Multiple organelles and signaling pathways are involved in the processes of initiation, progression, and completion of regeneration. Mitochondria, as intracellular signaling platforms of pleiotropic functions in animals, have recently gained attention in animal regeneration. However, most studies to date have focused on cellular and tissue regeneration. A mechanistic understanding of the mitochondrial role in large-scale regeneration is unclear. Here, we reviewed findings related to mitochondrial involvement in animal regeneration. We outlined the evidence of mitochondrial dynamics across different animal models. Moreover, we emphasized the impact of defects and perturbation in mitochondria resulting in regeneration failure. Ultimately, we discussed the regulation of aging by mitochondria in animal regeneration and recommended this for future study. We hope this review will serve as a means to advocate for more mechanistic studies of mitochondria related to animal regeneration on different scales.

Rps6ka2 enhances iMSC chondrogenic differentiation to attenuate knee osteoarthritis through articular cartilage regeneration in mice

Articular cartilage (AC) is most susceptible to degeneration in knee osteoarthritis (OA); however, the existing treatments for OA do not target the core link of the pathogenesis-"decreased tissue cell function activity and extracellular matrix (ECM) metabolic disorders" for effective intervention. iMSC hold lower heterogeneity and great promise in biological research and clinical applications. Rps6ka2 may play an important role in the iMSC to treat OA. In this study, the CRISPR/Cas9 gene editing Rps6ka2^-/- iMSC were obtained. Effect of Rps6ka2 on iMSC proliferation and chondrogenic differentiation was evaluated in vitro. An OA model was constructed in mice by surgical destabilization of medial meniscus (DMM). The Rps6ka2^-/- iMSC and iMSC were injected into the articular cavity twice-weekly for 8 weeks. In vitro experiments showed that Rps6ka2 could promote iMSC proliferation and chondrogenic differentiation. In vivo results further confirmed that Rps6ka2 could improve iMSC viability to promote ECM production to attenuate OA in mice.

Mitochondria on the move: Horizontal mitochondrial transfer in disease and health

Mammalian genes were long thought to be constrained within somatic cells in most cell types. This concept was challenged recently when cellular organelles including mitochondria were shown to move between mammalian cells in culture via cytoplasmic bridges. Recent research in animals indicates transfer of mitochondria in cancer and during lung injury in vivo, with considerable functional consequences. Since these pioneering discoveries, many studies have confirmed horizontal mitochondrial transfer (HMT) in vivo, and its functional characteristics and consequences have been described. Additional support for this phenomenon has come from phylogenetic studies. Apparently, mitochondrial trafficking between cells occurs more frequently than previously thought and contributes to diverse processes including bioenergetic crosstalk and homeostasis, disease treatment and recovery, and development of resistance to cancer therapy. Here we highlight current knowledge of HMT between cells, focusing primarily on in vivo systems, and contend that this process is not only (patho)physiologically relevant, but also can be exploited for the design of novel therapeutic approaches.

Mechanisms behind therapeutic potentials of mesenchymal stem cell mitochondria transfer/delivery

Mesenchymal stromal/stem cells (MSCs) perform their therapeutic effects through various mechanisms, including their ability to differentiate, producing different growth factors, immunomodulatory factors, and extracellular vesicles (EVs). In addition to the mentioned mechanisms, a new aspect of the therapeutic potential of MSCs has recently been noticed, which occurs through mitochondrial transfer. Various methods of MSCs mitochondria transfer have been used in studies to benefit from their therapeutic potential. Among these methods, mitochondrial transfer after MSCs transplantation in cell-to-cell contact, EVs-mediated transfer of mitochondria, and the use of MSCs isolated mitochondria (MSCs-mt) are well studied. Pathological conditions can affect the cells in the damaged microenvironment and lead to cells mitochondrial damage. Since the defect in the mitochondrial function of the cell leads to a decrease in ATP production and the subsequent cell death, restoring the mitochondrial content, functions, and hemostasis can affect the functions of the damaged cell. Various studies show that the transfer of MSCs mitochondria to other cells can affect vital processes such as proliferation, differentiation, cell metabolism, inflammatory responses, cell senescence, cell stress, and cell migration. These changes in cell attributes and behavior are very important for therapeutic purposes. For this reason, their investigation can play a significant role in the direction of the researchers'.

Mesenchymal stromal cells donate mitochondria to articular chondrocytes exposed to mitochondrial, environmental, and mechanical stress

Articular cartilage has limited healing capacity and no drugs are available that can prevent or slow the development of osteoarthritis (OA) after joint injury. Mesenchymal stromal cell (MSC)-based regenerative therapies for OA are increasingly common, but questions regarding their mechanisms of action remain. Our group recently reported that although cartilage is avascular and relatively metabolically quiescent, injury induces chondrocyte mitochondrial dysfunction, driving cartilage degradation and OA. MSCs are known to rescue injured cells and improve healing by donating healthy mitochondria in highly metabolic tissues, but mitochondrial transfer has not been investigated in cartilage. Here, we demonstrate that MSCs transfer mitochondria to stressed chondrocytes in cell culture and in injured cartilage tissue. Conditions known to induce chondrocyte mitochondrial dysfunction, including stimulation with rotenone/antimycin and hyperoxia, increased transfer. MSC-chondrocyte mitochondrial transfer was blocked by non-specific and specific (connexin-43) gap-junction inhibition. When exposed to mechanically injured cartilage, MSCs localized to areas of matrix damage and extended cellular processes deep into microcracks, delivering mitochondria to chondrocytes. This work provides insights into the chemical, environmental, and mechanical conditions that can elicit MSC-chondrocyte mitochondrial transfer in vitro and in situ, and our findings suggest a new potential role for MSC-based therapeutics after cartilage injury.

Probing Interleukin-6 in Stroke Pathology and Neural Stem Cell Transplantation

Stem cell transplantation is historically understood as a powerful preclinical therapeutic following stroke models. Current clinical strategies including clot busting/retrieval are limited by their time windows (tissue plasminogen activator: 3-4 h) and inevitable reperfusion injuries. However, 24+ h post-stroke, stem cells reduce infarction size, improve neurobehavioral performance, and reduce inflammatory agents including interleukins. Typically, interleukin-6 (IL-6) is regarded as proinflammatory, and thus, preclinical studies often discuss it as beneficial for neurological recuperation when stem cells reduce IL-6's expression. However, some studies have also demonstrated neurological benefit with upregulation of IL-6 or preconditioning of stem cells with IL-6. This review specifically focuses on stem cells and IL-6, and their occasionally disparate, occasionally synergistic roles in the setting of ischemic cerebrovascular insults.

Mitochondrial Cardiomyopathy: Molecular Epidemiology, Diagnosis, Models, and Therapeutic Management

Mitochondrial cardiomyopathy (MCM) is characterized by abnormal heart-muscle structure and function, caused by mutations in the nuclear genome or mitochondrial DNA. The heterogeneity of gene mutations and various clinical presentations in patients with cardiomyopathy make its diagnosis, molecular mechanism, and therapeutics great challenges. This review describes the molecular epidemiology of MCM and its clinical features, reviews the promising diagnostic tests applied for mitochondrial diseases and cardiomyopathies, and details the animal and cellular models used for modeling cardiomyopathy and to investigate disease pathogenesis in a controlled in vitro environment. It also discusses the emerging therapeutics tested in pre-clinical and clinical studies of cardiac regeneration.

Mesenchymal-Stem-Cell-Based Strategies for Retinal Diseases

Retinal diseases are major causes of irreversible vision loss and blindness. Despite extensive research into their pathophysiology and etiology, pharmacotherapy effectiveness and surgical outcomes remain poor. Based largely on numerous preclinical studies, administration of mesenchymal stem cells (MSCs) as a therapeutic strategy for retinal diseases holds great promise, and various approaches have been applied to the therapies. However, hindered by the retinal barriers, the initial vision for the stem cell replacement strategy fails to achieve the anticipated effect and has now been questioned. Accumulating evidence now suggests that the paracrine effect may play a dominant role in MSC-based treatment, and MSC-derived extracellular vesicles emerge as a novel compelling alternative for cell-free therapy. This review summarizes the therapeutic potential and current strategies of this fascinating class of cells in retinal degeneration and other retinal dysfunctions.

Intercellular mitochondrial transfer as a means of revitalizing injured glomerular endothelial cells

BACKGROUND

Recent studies have demonstrated that mesenchymal stem cells (MSCs) can rescue injured target cells via mitochondrial transfer. However, it has not been fully understood how bone marrow-derived MSCs repair glomeruli in diabetic kidney disease (DKD).

AIM

To explore the mitochondrial transfer involved in the rescue of injured glomerular endothelial cells (GECs) by MSCs, both in vitro and in vivo.

METHODS

In vitro experiments were performed to investigate the effect of co-culture with MSCs on high glucose-induced GECs. The transfer of mitochondria was visualized using fluorescent microscopy. GECs were freshly sorted and ultimately tested for apoptosis, viability, mRNA expression by real-time reverse transcriptase-polymerase chain reaction, protein expression by western blot, and mitochondrial function. Moreover, streptozotocin-induced DKD rats were infused with MSCs, and renal function and oxidative stress were detected with an automatic biochemical analyzer and related-detection kits after 2 wk. Kidney histology was analyzed by hematoxylin and eosin, periodic acid-Schiff, and immunohistochemical staining.

RESULTS

Fluorescence imaging confirmed that MSCs transferred mitochondria to injured GECs when co-cultured in vitro. We found that the apoptosis, proliferation, and mitochondrial function of injured GECs were improved following co-culture. Additionally, MSCs decreased pro-inflammatory cytokines [interleukin (IL)-6, IL-1β, and tumor necrosis factor-α] and pro-apoptotic factors (caspase 3 and Bax). Mitochondrial transfer also enhanced the expression of superoxide dismutase 2, B cell lymphoma-2, glutathione peroxidase (GPx) 3, and mitofusin 2 and inhibited reactive oxygen species (ROS) and dynamin-related protein 1 expression. Furthermore, MSCs significantly ameliorated functional parameters (blood urea nitrogen and serum creatinine) and decreased the production of malondialdehyde, advanced glycation end products, and ROS, whereas they increased the levels of GPx and superoxide dismutase in vivo. In addition, significant reductions in the glomerular basement membrane and renal interstitial fibrosis were observed following MSC treatment.

CONCLUSION

MSCs can rejuvenate damaged GECs via mitochondrial transfer. Additionally, the improvement of renal function and pathological changes in DKD by MSCs may be related to the mechanism of mitochondrial transfer.

Noninvasive Ophthalmic Imaging Measures Retinal Degeneration and Vision Deficits in Ndufs4-/- Mouse Model of Mitochondrial Complex I Deficiency

Purpose

To characterize postnatal ocular pathology in a Ndufs4^−/− mouse model of complex I deficiency using noninvasive retinal imaging and visual testing.

Methods

Ndufs4^−/− mice and wild-type (WT) littermates were analyzed at 3, 5, and 7 weeks postnatal. Retinal morphology was visualized by optical coherence tomography (OCT). OCT images were analyzed for changes in retinal thickness and reflectivity profiles. Visual function was assessed by electroretinogram (ERG) and optomotor reflex (OMR).

Results

Ndufs4^−/− animals have normal OCT morphology at weaning and develop inner plexiform layer atrophy over weeks 5 to 7. Outer retinal layers show hyporeflectivity of the external limiting membrane (ELM) and photoreceptor ellipsoid zone (EZ). Retinal function is impaired at 3 weeks, with profound deficits in b-wave, a-wave, and oscillatory potential amplitudes. The b-wave and oscillatory potential implicit times are delayed, but the a-wave implicit time is unaffected. Ndufs4^−/− animals have normal OMR at 3 weeks and present with increasing acuity and contrast OMR deficits at 5 and 7 weeks. Physiological thinning of inner retinal layers, attenuation of ELM reflectivity, and attenuation of ERG b- and a-wave amplitudes occur in WT C57BL/6 littermates between weeks 3 and 7.

Conclusions

Noninvasive ocular imaging captures early-onset retinal degeneration in Ndufs4^−/− mice and is a tractable approach for investigating retinal pathology subsequent to complex I deficiency.

Translational Relevance

Ophthalmic imaging captures clinically relevant measures of retinal disease in a fast-progressing mouse model of complex I deficiency consistent with human Leigh syndrome.

Mesenchymal Stromal Cell Mitochondrial Transfer as a Cell Rescue Strategy in Regenerative Medicine: A Review of Evidence in Preclinical Models

Mesenchymal stromal cells (MSC) have excellent clinical potential and numerous properties that ease its clinical translation. Mitochondria play a crucial role in energy metabolism, essential for cellular activities, such as proliferation, differentiation, and migration. However, mitochondrial dysfunction can occur due to diseases and pathological conditions. Research on mitochondrial transfer from MSCs to recipient cells has gained prominence. Numerous studies have demonstrated that mitochondrial transfer led to increased adenosine triphosphate (ATP) production, recovered mitochondrial bioenergetics, and rescued injured cells from apoptosis. However, the complex mechanisms that lead to mitochondrial transfer from healthy MSCs to damaged cells remain under investigation, and the factors contributing to mitochondrial bioenergetics recovery in recipient cells remain largely ambiguous. Therefore, this review demonstrates an overview of recent findings in preclinical studies reporting MSC mitochondrial transfer, comprised of information on cell sources, recipient cells, dosage, route of administration, mechanism of transfer, pathological conditions, and therapeutic effects. Further to the above, this research discusses the potential challenges of this therapy in its clinical settings and suggestions to overcome its challenges.

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

Mitochondrial dysfunction is considered to be a key contributor to the development of heart failure. Replacing injured mitochondria with healthy mitochondria to restore mitochondrial bioenergy in myocardium holds great promise for cardioprotection after infarction. This study aimed to investigate whether direct transplantation of exogenous mitochondria derived from mesenchymal stem cells (MSC-mt) is beneficial and superior in protecting cardiac function in a mouse model of myocardial infarction (MI) compared to mitochondria derived from skin fibroblast (FB-mt) and to explore the underlying mechanisms from their effects on the endothelial cells. The isolated MSC-mt presented intact mitochondrial morphology and activity, as determined by electron microscopy, JC-1 mitochondrial membrane potential assay, and seahorse assay. Direct injection of MSC-mt into the peri-infarct region in a mouse MI model enhanced blood vessel density, inhibited cardiac remodeling and apoptosis, thus improving heart function compared with FB-mt group. The injected MSC-mt can be tracked in the endothelial cells. In vitro, the fluorescence signal of MSC-mt can be detected in human umbilical vein endothelial cells (HUVECs) by confocal microscopy and flow cytometry after coculture. Compared to FB-mt, MSC-mt more effectively protected the HUVECs from oxidative stress-induced apoptosis and reduced mitochondrial production of reactive oxygen species. MSC-mt presented superior capacity in inducing tube formation, enhancing SCF secretion, ATP content and cell proliferation in HUVECs compared to FB-mt. Mechanistically, MSC-mt administration alleviated oxidative stress-induced endothelial senescence via activation of ERK pathway. These findings suggest that using MSCs as sources of mitochondria is feasible and that proangiogenesis could be the mechanism by which MSC-mt transplantation attenuates MI. MSC-mt transplantation might serve as a new therapeutic strategy for treating MI.

Japan to Global Eye Genetics Consortium: Extending Research Collaboration for Inherited Eye Diseases

Japan Eye Genetics Consortium (JEGC) was established in 2011 to migrate research system to all-Japan structure for collecting phenotype-genotype information for inherited retinal diseases and other retinal diseases including hereditary optic neuropathy and hereditary glaucoma. Diagnostic team was assembled to maintain quality of diagnostic and to collect phenotype information to database in Tokyo Medical Center (TMC). Over the past 10 years, 1538 pedigree [2788 deoxyribonucleic acid (DNA) samples] was collected from 38 ophthalmology departments and eye hospitals. Whole exome analysis has improved diagnostic rate from ~17% in 2011 to 53% in 2021, with 27% of known variants, 18% of novel variants in known gene, 8% of potential novel disease-causing genes, and 47% of pedigree with unknown cause. Approximately 70% of Japanese patients were affected by novel mutation or by unknown cause. In 2014, Asian Eye Genetics Consortium (AEGC) was established by researchers from Hong Kong, India, Japan, and the US, later renamed to Global Eye Genetics Consortium (GEGC) to expand the idea of collaborative research on rare genetic eye diseases in Asia, Middle East, Africa, and South America. GEGC phenotype-genotype database, GenEye, was constructed to collect and catalog genetic eye diseases at global scale. Over 200 members from 30 countries, GEGC now has 200 members from 30 continents, performing scientific programs, young investigator visiting program, and GEGC organized session at the meetings of the Asia-Pacific Academy of Ophthalmology (APAO), The Association for Research in Vision and Ophthalmology (ARVO), All India Ophthalmological Society (AIOS), World Ophthalmology Congress (WOC), and International Society for Eye Research (ISER).

In vivo study to assess dosage of allogeneic pig retinal progenitor cells: Long-term survival, engraftment, differentiation and safety

Despite notable efforts and significant therapeutical advances, age‐related macular degeneration remains the single most common reason for vision loss. Retinal progenitor cells (RPCs) are considered promising candidates for cellular treatments that repair and restore vision. In this allogenic study, the phenotypic profile of pig and human RPCs derived using similar manufacturing processes is compared. The long‐term (12‐week) survival of green fluorescent protein‐pig retinal progenitor cells GFP‐pRPC after subretinal transplantation into normal miniature pig (mini‐pig) retina is investigated. Human eyes are both anatomically and physiologically mimicked by pig eyes, so the pig is an ideal model to show an equivalent way of delivering cells, immunological response and dosage. The phenotypic equivalency of porcine and clinically intended human RPCs was established. Thirty‐nine mini‐pigs are used in this study, and vehicle‐injected eyes and non‐injected eyes serve as controls. Six groups are given different dosages of pRPCs, and the cells are found to survive well in all groups. At 12 weeks, strong evidence of integration is indicated by the location of the grafted cells within the neuro‐retina, extension of processes to the plexiform layers and expression of key retinal markers such as recoverin, rhodopsin and synaptophysin. No immunosuppression is used, and no immune response is found in any of the groups. No pRPC‐related histopathology findings are reported in the major organs investigated. An initial dose of 250 k cells in 100 µl of buffer is established as an appropriate initial dose for future human clinical trials.

Apelin-13 Pretreatment Promotes the Cardioprotective Effect of Mesenchymal Stem Cells against Myocardial Infarction by Improving Their Survival

Although mesenchymal stem cell- (MSC-) based therapy has shown promising results for myocardial infarction (MI), low cell survival heavily limits its beneficial effects. Apelin plays an essential regulatory role in cell proliferation. This study was aimed at determining whether Apelin-13 pretreatment could improve the survival of MSCs in the ischemic heart and enhance their cardioprotective efficacy against MI. MSCs were pretreated with or without Apelin-13 for 24 hours and then exposed to serum deprivation and hypoxia (SD/H) for 48 hours. The mitochondrial morphology of MSCs was assessed by MitoTracker staining. The apoptosis of MSCs was determined by TUNEL staining. The level of mitochondrial reactive oxygen species (ROS) of MSCs was detected by Mito-Sox staining. MSCs and Apelin-13-pretreated MSCs were transplanted into the peri-infarct region in a mouse MI model. Apelin-13 pretreatment protected MSCs against SD/H-induced mitochondrial fragmentation and apoptosis. Apelin-13 pretreatment reduced ROS generation induced by SD/H in MSCs. Furthermore, Apelin-13 pretreatment enhanced the angiogenesis of MSCs under SD/H conditions. Mechanistically, Apelin-13 pretreatment inhibited SD/H-induced MSC apoptosis by downregulating mitochondrial fission via activation of the ERK pathway, and these effects were partially abrogated by ERK inhibitor U0126. Apelin-13 pretreatment promoted the survival of MSCs in the ischemic heart. Moreover, transplantation with Apelin-13-pretreated MSCs improved heart function and increased angiogenesis accompanied by decreased fibrosis compared with MSC transplantation at 28 days following MI. These findings reveal that pretreatment with Apelin-13 improves MSCs survival and enhances their therapeutic efficacy for MI. Our study provides a novel approach to improve MSC-based therapy for cardiovascular disease.

Ndufs4 knockout mouse models of Leigh syndrome: pathophysiology and intervention

Mitochondria are small cellular constituents that generate cellular energy (ATP) by oxidative phosphorylation (OXPHOS). Dysfunction of these organelles is linked to a heterogeneous group of multisystemic disorders, including diabetes, cancer, ageing-related pathologies and rare mitochondrial diseases. With respect to the latter, mutations in subunit-encoding genes and assembly factors of the first OXPHOS complex (complex I) induce isolated complex I deficiency and Leigh syndrome. This syndrome is an early-onset, often fatal, encephalopathy with a variable clinical presentation and poor prognosis due to the lack of effective intervention strategies. Mutations in the nuclear DNA-encoded NDUFS4 gene, encoding the NADH:ubiquinone oxidoreductase subunit S4 (NDUFS4) of complex I, induce 'mitochondrial complex I deficiency, nuclear type 1' (MC1DN1) and Leigh syndrome in paediatric patients. A variety of (tissue-specific) Ndufs4 knockout mouse models were developed to study the Leigh syndrome pathomechanism and intervention testing. Here, we review and discuss the role of complex I and NDUFS4 mutations in human mitochondrial disease, and review how the analysis of Ndufs4 knockout mouse models has generated new insights into the MC1ND1/Leigh syndrome pathomechanism and its therapeutic targeting.

Characteristics and regulation of mesenchymal stem cell plasticity by the microenvironment — specific factors involved in the regulation of MSC plasticity

Mesenchymal stem cells (MSCs), multipotent stromal cells, have attracted extensive attention in the field of regenerative medicine and cell therapy due to the capacity of self-renewal, multilineage differentiation, and immune regulation. MSCs have different cellular effects in different diseases, and even have markedly different curative effects with different tissue sources, indicating the plasticity of MSCs. The phenotypes, secreted factors, and proliferative, migratory, differentiating, and immunomodulatory effects of MSCs depend on certain mediators present in their microenvironment. Understanding microenvironmental factors and their internal mechanisms in MSC responses may help in subsequent prediction and improvement of clinical benefits. This review highlighted the recent advances in MSC plasticity in the physiological and pathological microenvironment and multiple microenvironmental factors regulating MSC plasticity. It also highlighted some progress in the underlying molecular mechanisms of MSC remodeling in the microenvironment. It might provide references for the improvement in vitro culture of MSCs, clinical application, and in vivo induction.

Human pluripotent stem cell-derived ectomesenchymal stromal cells promote more robust functional recovery than umbilical cord-derived mesenchymal stromal cells after hypoxic-ischaemic brain damage

Aims: Hypoxic-ischaemic encephalopathy (HIE) is one of the most serious complications in neonates and infants. Mesenchymal stromal cell (MSC)-based therapy is emerging as a promising treatment avenue for HIE. However, despite its enormous potential, the clinical application of MSCs is limited by cell heterogeneity, low isolation efficiency and unpredictable effectiveness. In this study, we examined the therapeutic effects and underlying mechanisms of human pluripotent stem cell-derived ectomesenchymal stromal cells (hPSC-EMSCs) in a rat model of HIE.

Methods: hPSC-EMSCs were induced from either human embryonic stem cells or induced pluripotent stem cells. Stem cells or the conditioned medium (CM) derived from stem cells were delivered intracranially or intranasally to neonatal rats with HIE. Human umbilical cord-derived MSCs (hUC-MSCs) were used as the therapeutic comparison control and phosphate-buffered saline (PBS) was used as a negative control. Lesion size, apoptosis, neurogenesis, astrogliosis and microgliosis were evaluated. The rotarod test and Morris water maze were used to determine brain functional recovery. The PC-12 cell line, rat primary cortical neurons and neural progenitor cells were used to evaluate neurite outgrowth and the neuroprotective and neurogenesis effects of hPSC-EMSCs/hUC-MSCs. RNA-seq and enzyme-linked immunosorbent assays were used to determine the secretory factors that were differentially expressed between hPSC-EMSCs and hUC-MSCs. The activation and suppression of extracellular signal-regulated kinase (ERK) and cAMP response element-binding protein (CREB) were characterised using western blotting and immunofluorescent staining.

Results: hPSC-EMSCs showed a higher neuroprotective potential than hUC-MSCs, as demonstrated by a more significant reduction in lesion size and apoptosis in the rat brain following hypoxia-ischaemia (HI). Compared with PBS treatment, hPSC-EMSCs promoted endogenous neurogenesis and alleviated astrogliosis and microgliosis. hPSC-EMSCs were more effective than hUC-MSCs. hPSC-EMSCs achieved a greater recovery of brain function than hUC-MSCs and PBS in rats with HIE. CM derived from hPSC-EMSCs had neuroprotective and neurorestorative effects in vitro through anti-apoptotic and neurite outgrowth- and neurogenesis-promoting effects. Direct comparisons between hPSC-EMSCs and hUC-MSCs revealed the significant enrichment of a group of secretory factors in hPSC-EMSCs, including nerve growth factor (NGF), platelet-derived growth factor-AA and transforming growth factor-β₂, which are involved in neurogenesis, synaptic transmission and neurotransmitter transport, respectively. Mechanistically, the CM derived from hPSC-EMSCs was found to potentiate NGF-induced neurite outgrowth and the neuronal differentiation of NPCs via the ERK/CREB pathway. Suppression of ERK or CREB abolished CM-potentiated neuritogenesis and neuronal differentiation. Finally, intranasal delivery of the CM derived from hPSC-EMSCs significantly reduced brain lesion size, promoted endogenous neurogenesis, mitigated inflammatory responses and improved functional recovery in rats with HIE.

Conclusion: hPSC-EMSCs promote functional recovery after HI through multifaceted neuromodulatory activities via paracrine/trophic mechanisms. We propose the use of hPSC-EMSCs for the treatment of HIE, as they offer an excellent unlimited cellular source of MSCs.

Effects of fluoroquinolones and tetracyclines on mitochondria of human retinal MIO-M1 cells

Our goal was to explore the detrimental impacts of ciprofloxacin (CPFX) and tetracycline (TETRA) on human retinal Müller (MIO-M1) cells in vitro. Cells were exposed to 30, 60 and 120 μg/ml of CPFX and TETRA. The cellular metabolism was measured with the MTT assay. The JC-1 and CM-H2DCFDA assays were used to evaluate the levels of mitochondrial membrane potential (MMP) and ROS (reactive oxygen species), respectively. Mitochondrial DNA (mtDNA) copy number, along with gene expression levels associated with apoptotic (BAX, BCL2-L13, BCL2, CASP-3 and CASP-9), inflammatory (IL-6, IL-1β, TGF-α, TGF-β1 and TGF-β2) and antioxidant pathways (SOD2, SOD3, GPX3 and NOX4) were analyzed via Quantitative Real-Time PCR (qRT-PCR). Bioenergetic profiles were measured using the Seahorse® XF Flux Analyzer. Cells exposed 24 h to 120 μg/ml TETRA demonstrated higher cellular metabolism compared to vehicle-treated cells. At each time points, (i) all TETRA concentrations reduced MMP levels and (ii) ROS levels were reduced by TETRA 120 μg/ml treatment. TETRA caused (i) higher expression of CASP-3, CASP-9, TGF-α, IL-1B, GPX3 and SOD3 but (ii) decreased levels of TGF-B2 and SOD2. ATP production and spare respiratory capacity declined with TETRA treatment. Cellular metabolism was reduced with CPFX 120 μg/ml in all cultures and 60 μg/ml after 72 h. The CPFX 120 μg/ml reduced MMP in all cultures and ROS levels (72 h). CPFX treatment (i) increased expression of CASP-3, CASP-9, and BCL2-L13, (ii) elevated the basal oxygen consumption rate, and (iii) lowered the mtDNA copy numbers and expression levels of TGF-B2, IL-6 and IL-1B compared to vehicle-control cells. We conclude that clinically relevant dosages of bactericidal and bacteriostatic antibiotics can have negative effects on the cellular metabolism and mitochondrial membrane potential of the retinal MIO-M1 cells in vitro. It is noteworthy to mention that apoptotic and inflammatory pathways in exposed cells were affected significantly This is the first study showing the negative impact of fluoroquinolones and tetracyclines on mitochondrial behavior of human retinal MIO-M1 cells.

Allogeneic adipose-derived mesenchymal stromal cell transplantation for refractory lupus nephritis: Results of a phase I clinical trial

BACKGROUND

Mesenchymal stromal/stem cells (MSCs) are known for their immunomodulatory properties. This study was performed to analyse the effects of MSC transplantation on treatment-resistant lupus nephritis (LN).

METHODS

In this phase I trial, nine biopsy-proven LN patients refractory to standard treatments underwent systemic infusion of 2 × 10⁶ allogeneic adipose-derived (AD) MSCs/kg and were followed for 12 months post-intervention.

RESULTS

The treatment protocol resulted in no major adverse events. Urine protein levels significantly decreased during the first month post-intervention (baseline vs. month 1 (median): 1800 vs. 1020, P = 0.008), followed by a gradual increase but remained significantly lower than baseline only up to the 3rd month. During the first 3 months post-intervention, complete renal response (proteinuria < 0.5 g/24 h) and partial response (proteinuria > 0.5 g/24 h, but > 50% decrease in proteinuria) were observed in 33.3% and 44.4% of the patients, respectively, though these rates declined thereafter. Median score of Systemic Lupus Erythematosus Disease Activity Index decreased significantly from 16 at the baseline to 6 at sixth months post-treatment (P = 0.007), though it slightly increased at the 12th month follow-up.

CONCLUSIONS

Allogenic AD-MSC transplantation was associated with favourable safety and efficient to reduce urine protein excretion and disease activity; however, the maximum effect (greatest improvement in outcomes) was observed at 1 month based on the proteinuria, and 6 months post-intervention based on disease activity scores. A single dose of AD-MSCs may not be adequate to maintain long-term remission of refractory LN, and so, additional doses may be required.

Application of mesenchymal stem cells derived from human pluripotent stem cells in regenerative medicine

Mesenchymal stem cells (MSCs) represent the most clinically used stem cells in regenerative medicine. However, due to the disadvantages with primary MSCs, such as limited cell proliferative capacity and rarity in the tissues leading to limited MSCs, gradual loss of differentiation during in vitro expansion reducing the efficacy of MSC application, and variation among donors increasing the uncertainty of MSC efficacy, the clinical application of MSCs has been greatly hampered. MSCs derived from human pluripotent stem cells (hPSC-MSCs) can circumvent these problems associated with primary MSCs. Due to the infinite self-renewal of hPSCs and their differentiation potential towards MSCs, hPSC-MSCs are emerging as an attractive alternative for regenerative medicine. This review summarizes the progress on derivation of MSCs from human pluripotent stem cells, disease modelling and drug screening using hPSC-MSCs, and various applications of hPSC-MSCs in regenerative medicine. In the end, the challenges and concerns with hPSC-MSC applications are also discussed.

Emerging concepts in the treatment of optic neuritis: mesenchymal stem cell-derived extracellular vesicles

BACKGROUND

Optic neuritis (ON) is frequently encountered in multiple sclerosis, neuromyelitis optica spectrum disorder, anti-myelin oligodendrocyte glycoprotein associated disease, and other systemic autoimmune disorders. The hallmarks are an abnormal optic nerve and inflammatory demyelination; episodes of optic neuritis tend to be recurrent, and particularly for neuromyelitis optica spectrum disorder, may result in permanent vision loss.

MAIN BODY

Mesenchymal stem cell (MSC) therapy is a promising approach that results in remyelination, neuroprotection of axons, and has demonstrated success in clinical studies in other neuro-degenerative diseases and in animal models of ON. However, cell transplantation has significant disadvantages and complications. Cell-free approaches utilizing extracellular vesicles (EVs) produced by MSCs exhibit anti-inflammatory and neuroprotective effects in multiple animal models of neuro-degenerative diseases and in rodent models of multiple sclerosis (MS). EVs have potential to be an effective cell-free therapy in optic neuritis because of their anti-inflammatory and remyelination stimulating properties, ability to cross the blood brain barrier, and ability to be safely administered without immunosuppression.

CONCLUSION

We review the potential application of MSC EVs as an emerging treatment strategy for optic neuritis by reviewing studies in multiple sclerosis and related disorders, and in neurodegeneration, and discuss the challenges and potential rewards of clinical translation of EVs including cell targeting, carrying of therapeutic microRNAs, and prolonging delivery for treatment of optic neuritis.

Ndufs4 knockout mouse models of Leigh syndrome: pathophysiology and intervention

Mitochondria are small cellular constituents that generate cellular energy (ATP) by oxidative phosphorylation (OXPHOS). Dysfunction of these organelles is linked to a heterogeneous group of multisystemic disorders, including diabetes, cancer, ageing-related pathologies and rare mitochondrial diseases. With respect to the latter, mutations in subunit-encoding genes and assembly factors of the first OXPHOS complex (complex I) induce isolated complex I deficiency and Leigh syndrome. This syndrome is an early-onset, often fatal, encephalopathy with a variable clinical presentation and poor prognosis due to the lack of effective intervention strategies. Mutations in the nuclear DNA-encoded NDUFS4 gene, encoding the NADH:ubiquinone oxidoreductase subunit S4 (NDUFS4) of complex I, induce ‘mitochondrial complex I deficiency, nuclear type 1’ (MC1DN1) and Leigh syndrome in paediatric patients. A variety of (tissue-specific) Ndufs4 knockout mouse models were developed to study the Leigh syndrome pathomechanism and intervention testing.

Here, we review and discuss the role of complex I and NDUFS4 mutations in human mitochondrial disease, and review how the analysis of Ndufs4 knockout mouse models has generated new insights into the MC1ND1/Leigh syndrome pathomechanism and its therapeutic targeting.

Mitochondrial developmental encephalopathy with bilateral optic neuropathy related to homozygous variants in IMMT gene

IMMT gene codes for mitofilin, a mitochondrial inner membrane protein that regulates the morphology of mitochondrial cristae. The phenotype associated with mutations in this gene has not been yet established, but functional studies carried out show that its loss causes a mitochondrial alteration, both in the morphology of the mitochondrial crests and in their function. We present two cousins from an extended highly consanguineous family with developmental encephalopathy, hypotonia, nystagmus due to optic neuropathy. The likely pathogenic homozygous c.895A>G (p.Lys299Glu) variant in the IMMT gene co-segregates with the disease and associates altered mitochondrial cristae observed by electron microscopy.

Retinal Stem/Progenitor Cells Derived From Adult Müller Glia for the Treatment of Retinal Degeneration

Over the past two decades, progress in our understanding of glial function has been revolutionary. Within the retina, a subset of glial cells termed the “Müller glia (MG),” have been demonstrated to play key roles in retinal homeostasis, structure and metabolism. Additionally, MG have also been shown to possess the regenerative capacity that varies across species. In teleost fish, MG respond to injury by reprogramming into stem-like cells capable of regenerating lost tissue. The expression of stem/progenitor cell markers has been demonstrated broadly in mammalian MG, including human MG, but their in vivo regenerative capacity appears evolutionarily limited. Advances in stem cell therapy have progressively elucidated critical mechanisms underlying innate MG reprogramming in teleost fish, which have shown promising results when applied to rodents. Furthermore, when cultured ex vivo, MG from mammals can differentiate into several retina cell types. In this review, we will explore the reparative and regenerative potential of MG in cellular therapy approaches, and outline our current understanding of embryonic retinal development, the stem-cell potential of MG in adult vertebrate retina (including human), and microenvironmental cues that guide MG reprogramming.

Pluripotent-derived Mesenchymal Stem/stromal Cells: an Overview of the Derivation Protocol Efficacies and the Differences Among the Derived Cells

Mesenchymal stem/stromal cells (MSCs) are remarkable tools for regenerative medicine. Therapeutic approaches using these cells can promote increased activity and viability in several cell types through diverse mechanisms such as paracrine and immunomodulatory activities, contributing substantially to tissue regeneration and functional recovery. However, biological samples of human MSCs, usually obtained from adult tissues, often exhibit variable behavior during in vitro culture, especially with respect to cell population heterogeneity, replicative senescence, and consequent loss of functionality. Accordingly, it is necessary to establish standard protocols to generate high-quality, stable cell cultures, for example, by using pluripotent stem cells (PSCs) in derivation protocols of MSC-like cells since PSCs maintain their characteristics consistently during culture. However, the available protocols seem to generate distinct populations of PSC-derivedMSCs (PSC-MSCs) with peculiar attributes, which do not always resemble bona fide primary MSCs. The present review addresses the developmental basis behind some of these derivation protocols, exposing the differences among them and discussing the functional properties of PSC-MSCs, shedding light on elements that may help determine standard characterizations and criteria to evaluate and define these cells.

Chicken bone marrow mesenchymal stem cells improve lung and distal organ injury

Mesenchymal stem cells (MSCs) are associated with pulmonary protection and longevity. We separated chicken bone marrow-derived mesenchymal stem cells (BM-MSCs); investigated whether BM-MSCs can improve lipopolysaccharide (LPS)-induced lung and distal organ injury; and explored the underlying mechanisms. Ninety-six male ICR (6 weeks old) mice were randomly divided into three groups: Sham, LPS, and LPS + MSC groups. The mice were intratracheally injected with 5 mg/kg LPS to induce acute lung injury (ALI). The histopathological severity of injury to the lung, liver, kidney, heart, and aortic tissues was detected. Wet/dry ratio, protein concentrations in bronchoalveolar lavage fluid (BALF), BALF cell counts, inflammatory cytokine levels in serum, inflammatory cytokine gene expression, and oxidative stress-related indicators were detected. In addition, a survival analysis was performed in sixty male ICR mice (6 weeks old, 18–20 g). This study used chicken BM-MSCs, which are easier to obtain and more convenient than other animal or human MSCs, and have MSC-associated properties, such as a colony forming ability, multilineage differentiation potential, and certain phenotypes. BM-MSCs administration significantly improved the survival rate, systemic inflammation, and the histopathological severity of lung, liver, kidney, and aortic injury during ALI. BM-MSCs administration reduced the levels of inflammatory factors in BALF, the infiltration of neutrophils, and oxidative stress injury in lung tissue. In addition, BM-MSCs administration reduced TRL4 and Mdy88 mRNA expression during ALI. Chicken BM-MSCs serve as a potential alternative resource for stem cell therapy and exert a prominent effect on LPS-induced ALI and extrapulmonary injury, in part through TRL4/Mdy88 signaling and inhibition of neutrophil inflammation and oxidative stress injury.

The Therapeutic Potential of Mesenchymal Stromal Cells for Regenerative Medicine: Current Knowledge and Future Understandings

In recent decades, research on the therapeutic potential of progenitor cells has advanced considerably. Among progenitor cells, mesenchymal stromal cells (MSCs) have attracted significant interest and have proven to be a promising tool for regenerative medicine. MSCs are isolated from various anatomical sites, including bone marrow, adipose tissue, and umbilical cord. Advances in separation, culture, and expansion techniques for MSCs have enabled their large-scale therapeutic application. This progress accompanied by the rapid improvement of transplantation practices has enhanced the utilization of MSCs in regenerative medicine. During tissue healing, MSCs may exhibit several therapeutic functions to support the repair and regeneration of injured tissue. The process underlying these effects likely involves the migration and homing of MSCs, as well as their immunotropic functions. The direct differentiation of MSCs as a cell replacement therapeutic mechanism is discussed. The fate and behavior of MSCs are further regulated by their microenvironment, which may consequently influence their repair potential. A paracrine pathway based on the release of different messengers, including regulatory factors, chemokines, cytokines, growth factors, and nucleic acids that can be secreted or packaged into extracellular vesicles, is also implicated in the therapeutic properties of MSCs. In this review, we will discuss relevant outcomes regarding the properties and roles of MSCs during tissue repair and regeneration. We will critically examine the influence of the local microenvironment, especially immunological and inflammatory signals, as well as the mechanisms underlying these therapeutic effects. Importantly, we will describe the interactions of local progenitor and immune cells with MSCs and their modulation during tissue injury. We will also highlight the crucial role of paracrine pathways, including the role of extracellular vesicles, in this healing process. Moreover, we will discuss the therapeutic potential of MSCs and MSC-derived extracellular vesicles in the treatment of COVID-19 (coronavirus disease 2019) patients. Overall, this review will provide a better understanding of MSC-based therapies as a novel immunoregenerative strategy.

The Immunomodulatory Properties of Mesenchymal Stem Cells Play a Critical Role in Inducing Immune Tolerance after Liver Transplantation

Although liver transplantation is considered to be the best choice for patients with end-stage liver diseases, postoperative immune rejection still cannot be overlooked. Patients with liver transplantation have to take immunosuppressive drugs for a long time or even their entire lives, in which heavy economic burden and side effects caused by the drugs have become the major impediment for liver transplantation. There is a growing body of evidences indicating that mesenchymal stem cell (MSC) transplantation, a promising tool in regenerative medicine, can be used as an effective way to induce immune tolerance after liver transplantation based on their huge expansion potential and unique immunomodulatory properties. MSCs have been reported to inhibit innate immunity and adaptive immunity to induce a tolerogenic microenvironment. In in vitro studies, transplanted MSCs show plasticity in immune regulation by altering their viability, migration, differentiation, and secretion in the interactions with the surrounding host microenvironment. In this review, we aim to provide an overview of the current understanding of immunomodulatory properties of MSCs in liver transplantation, to elucidate the potential mechanisms behind MSCs regulating immune response, especially in vivo and the influence of the microenvironment, and ultimately to discuss the feasible strategies to improve the clinical prognosis of liver transplantation. Only after exhaustive understanding of potential mechanisms of the MSC immunomodulation can we improve the safety and effectiveness of MSC treatment and achieve better therapeutic effects.

Effects of Iron and Zinc on Mitochondria: Potential Mechanisms of Glaucomatous Injury

Glaucoma is the most substantial cause of irreversible blinding, which is accompanied by progressive retinal ganglion cell damage. Retinal ganglion cells are energy-intensive neurons that connect the brain and retina, and depend on mitochondrial homeostasis to transduce visual information through the brain. As cofactors that regulate many metabolic signals, iron and zinc have attracted increasing attention in studies on neurons and neurodegenerative diseases. Here, we summarize the research connecting iron, zinc, neuronal mitochondria, and glaucomatous injury, with the aim of updating and expanding the current view of how retinal ganglion cells degenerate in glaucoma, which can reveal novel potential targets for neuroprotection.

The application of umbilical cord-derived MSCs in cardiovascular diseases

Transplantation of stem cells is a promising, emerging treatment for cardiovascular diseases in the modern era. Mesenchymal stem cells (MSCs) derived from the umbilical cord are one of the most promising cell sources because of their capacity for differentiation into cardiomyocytes, endothelial cells and vascular smooth muscle cells in vitro/in vivo. In addition, umbilical cord‐derived MSCs (UC‐MSCs) secrete many effective molecules regulating apoptosis, fibrosis and neovascularization. Another important and specific characteristic of UC‐MSCs is their low immunogenicity and immunomodulatory properties. However, the application of UC‐MSCs still faces some challenges, such as low survivability and tissue retention in a harmful disease environment. Gene engineering and pharmacological studies have been implemented to overcome these difficulties. In this review, we summarize the differentiation ability, secretion function, immunoregulatory properties and preclinical/clinical studies of UC‐MSCs, highlighting the advantages of UC‐MSCs for the treatment of cardiovascular diseases.

The mini player with diverse functions: extracellular vesicles in cell biology, disease, and therapeutics

Extracellular vesicles (EVs) are tiny biological nanovesicles ranging from approximately 30-1000 nm in diameter that are released into the extracellular matrix of most cell types and in biofluids. The classification of EVs includes exosomes, microvesicles, and apoptotic bodies, dependent on various factors such as size, markers, and biogenesis pathways. The transition of EV relevance from that of being assumed as a trash bag to be a key player in critical physiological and pathological conditions has been revolutionary in many ways. EVs have been recently revealed to play a crucial role in stem cell biology and cancer progression via intercellular communication, contributing to organ development and the progression of cancer. This review focuses on the significant research progress made so far in the role of the crosstalk between EVs and stem cells and their niche, and cellular communication among different germ layers in developmental biology. In addition, it discusses the role of EVs in cancer progression and their application as therapeutic agents or drug delivery vehicles. All such discoveries have been facilitated by tremendous technological advancements in EV-associated research, especially the microfluidics systems. Their pros and cons in the context of characterization of EVs are also extensively discussed in this review. This review also deliberates the role of EVs in normal cell processes and disease conditions, and their application as a diagnostic and therapeutic tool. Finally, we propose future perspectives for EV-related research in stem cell and cancer biology.