Mesenchymal stem cell repression of Th17 cells is triggered by mitochondrial transfer

Regulatory Effect of Mesenchymal Stem Cells on T Cell Phenotypes in Autoimmune Diseases

Research on mesenchymal stem cells (MSCs) starts from the earliest assumption that cells derived from the bone marrow have the ability to repair tissues. Several scientists have since documented the crucial role of bone marrow-derived MSCs (BM-MSCs) in processes such as embryonic bone and cartilage formation, adult fracture and tissue repair, and immunomodulatory activities in therapeutic applications. In addition to BM-MSCs, several sources of MSCs have been reported to possess tissue repair and immunoregulatory abilities, making them potential treatment options for many diseases. Therefore, the therapeutic potential of MSCs in various diseases including autoimmune conditions has been explored. In addition to an imbalance of T cell subsets in most patients with autoimmune diseases, they also exhibit complex disease manifestations, overlapping symptoms among diseases, and difficult treatment. MSCs can regulate T cell subsets to restore their immune homeostasis toward disease resolution in autoimmune conditions. This review summarizes the role of MSCs in relieving autoimmune diseases via the regulation of T cell phenotypes.

Musculoskeletal Progenitor/Stromal Cell-Derived Mitochondria Modulate Cell Differentiation and Therapeutical Function

Musculoskeletal stromal cells’ (MSCs’) metabolism impacts cell differentiation as well as immune function. During osteogenic and adipogenic differentiation, BM-MSCs show a preference for glycolysis during proliferation but shift to an oxidative phosphorylation (OxPhos)-dependent metabolism. The MSC immunoregulatory fate is achieved with cell polarization, and the result is sustained production of immunoregulatory molecules (including PGE2, HGF, IL1RA, IL6, IL8, IDO activity) in response to inflammatory stimuli. MSCs adapt their energetic metabolism when acquiring immunomodulatory property and shift to aerobic glycolysis. This can be achieved via hypoxia, pretreatment with small molecule-metabolic mediators such as oligomycin, or AKT/mTOR pathway modulation. The immunoregulatory effect of MSC on macrophages polarization and Th17 switch is related to the glycolytic status of the MSC. Indeed, MSCs pretreated with oligomycin decreased the M1/M2 ratio, inhibited T-CD4 proliferation, and prevented Th17 switch. Mitochondrial activity also impacts MSC metabolism. In the bone marrow, MSCs are present in a quiescent, low proliferation, but they keep their multi-progenitor function. In this stage, they appear to be glycolytic with active mitochondria (MT) status. During MSC expansion, we observed a metabolic shift toward OXPhos, coupled with an increased MT activity. An increased production of ROS and dysfunctional mitochondria is associated with the metabolic shift to glycolysis. In contrast, when MSC underwent chondro or osteoblast differentiation, they showed a decreased glycolysis and inhibition of the pentose phosphate pathway (PPP). In parallel the mitochondrial enzymatic activities increased associated with oxidative phosphorylation enhancement. MSCs respond to damaged or inflamed tissue through the transfer of MT to injured and immune cells, conveying a type of signaling that contributes to the restoration of cell homeostasis and immune function. The delivery of MT into injured cells increased ATP levels which in turn maintained cellular bioenergetics and recovered cell functions. MSC-derived MT may be transferred via tunneling nanotubes to undifferentiated cardiomyocytes and leading to their maturation. In this review, we will decipher the pathways and the mechanisms responsible for mitochondria transfer and activity. The eventual reversal of the metabolic and pro-inflammatory profile induced by the MT transfer will open new avenues for the control of inflammatory diseases.

The diversity and coexistence of extracellular mitochondria in circulation: A friend or foe of the immune system

The diversity and coexistence of extracellular mitochondria may have a key role in the maintenance of health and progression of disease. Studies report that active mitochondria can be found physiologically outside of cells and circulating in the blood without inducing an inflammatory response. In addition, inactive or harmed mitochondria have been recognized as activators of immune cells, as they play an essential role in diseases characterized by the metabolic deregulation of these cells, such as sepsis. In this review we analyze key aspects regarding the existence of a diversity of extracellular mitochondria, their coexistence in body fluids and their effects on various immune cells. Additionally, we introduce models of how extracellular mitochondria could be interacting to maintain health and affect disease prognosis. Unwrapped mitochondria (freeMitos) can exist as viable, active, inactive or harmed organelles. Mitochondria can also be found wrapped in a membrane (wrappedMitos) that may differ depending on the cell of origin. Mitochondrial fragments can also be present in various body fluids as DAMPs, as mtDNA enclosed in vesicles or as circulating-cell-free mtDNA (ccf-mtDNA). Interestingly, the great quantity of evidence regarding the levels of ccf-mtDNA and their correlation with aging and disease allows for the identification of the diversity, but not type, of extracellular mitochondria. The existence of a diversity of mitochondria and their effects on immune cells opens a new concept in the biomedical field towards the understanding of health, the progression of disease and the development of mitochondria as therapeutic agents.

Extracellular mitochondria in the cerebrospinal fluid (CSF): Potential types and key roles in central nervous system (CNS) physiology and pathogenesis

The cerebrospinal fluid (CSF) has an important role in the transport of nutrients and signaling molecules to the central nervous and immune systems through its circulation along the brain and spinal cord tissues. The mitochondrial activity in the central nervous system (CNS) is essential in processes such as neuroplasticity, neural differentiation and production of neurotransmitters. Interestingly, extracellular and active mitochondria have been detected in the CSF where they act as a biomarker for the outcome of pathologies such as subarachnoid hemorrhage and delayed cerebral ischemia. Additionally, cell-free-circulating mitochondrial DNA (ccf-mtDNA) has been detected in both the CSF of healthy donors and in that of patients with neurodegenerative diseases. Key questions arise as there is still much debate regarding if ccf-mtDNA detected in CSF is associated with a diversity of active or inactive extracellular mitochondria coexisting in distinct pathologies. Additionally, it is of great scientific and medical importance to identify the role of extracellular mitochondria (active and inactive) in the CSF and the difference between them being damage associated molecular patterns (DAMPs) or factors that promote homeostasis. This review analyzes the different types of extracellular mitochondria, methods for their identification and their presence in CSF. Extracellular mitochondria in the CSF could have an important implication in health and disease, which may lead to the development of medical approaches that utilize mitochondria as therapeutic agents.

The role and mechanism of mitochondrial functions and energy metabolism in the function regulation of the mesenchymal stem cells

Mesenchymal stem cells (MSCs) are multipotent cells that show self-renewal, multi-directional differentiation, and paracrine and immune regulation. As a result of these properties, the MSCs have great clinical application prospects, especially in the regeneration of injured tissues, functional reconstruction, and cell therapy. However, the transplanted MSCs are prone to ageing and apoptosis and have a difficult to control direction differentiation. Therefore, it is necessary to effectively regulate the functions of the MSCs to promote their desired effects. In recent years, it has been found that mitochondria, the main organelles responsible for energy metabolism and adenosine triphosphate production in cells, play a key role in regulating different functions of the MSCs through various mechanisms. Thus, mitochondria could act as effective targets for regulating and promoting the functions of the MSCs. In this review, we discuss the research status and current understanding of the role and mechanism of mitochondrial energy metabolism, morphology, transfer modes, and dynamics on MSC functions.

Intercellular mitochondrial transfer as a means of tissue revitalization

As the crucial powerhouse for cell metabolism and tissue survival, the mitochondrion frequently undergoes morphological or positional changes when responding to various stresses and energy demands. In addition to intracellular changes, mitochondria can also be transferred intercellularly. Besides restoring stressed cells and damaged tissues due to mitochondrial dysfunction, the intercellular mitochondrial transfer also occurs under physiological conditions. In this review, the phenomenon of mitochondrial transfer is described according to its function under both physiological and pathological conditions, including tissue homeostasis, damaged tissue repair, tumor progression, and immunoregulation. Then, the mechanisms that contribute to this process are summarized, such as the trigger factors and transfer routes. Furthermore, various perspectives are explored to better understand the mysteries of cell-cell mitochondrial trafficking. In addition, potential therapeutic strategies for mitochondria-targeted application to rescue tissue damage and degeneration, as well as the inhibition of tumor progression, are discussed.

Immunomodulatory Properties of Mesenchymal Stromal Cells: An Update

Mesenchymal stromal cells (MSCs) are characterized by an extraordinary capacity to modulate the phenotype and functional properties of various immune cells that play an essential role in the pathogenesis of inflammatory disorders. Thus, MSCs efficiently impair the phagocytic and antigen-presenting capacity of monocytes/macrophages and promote the expression of immunosuppressive molecules such as interleukin (IL)-10 and programmed cell death 1 ligand 1 by these cells. They also effectively inhibit the maturation of dendritic cells and their ability to produce proinflammatory cytokines and to stimulate potent T-cell responses. Furthermore, MSCs inhibit the generation and proinflammatory properties of CD4⁺ T helper (Th)1 and Th17 cells, while they promote the proliferation of regulatory T cells and their inhibitory capabilities. MSCs also impair the expansion, cytokine secretion, and cytotoxic activity of proinflammatory CD8⁺ T cells. Moreover, MSCs inhibit the differentiation, proliferation, and antibody secretion of B cells, and foster the generation of IL-10-producing regulatory B cells. Various cell membrane-associated and soluble molecules essentially contribute to these MSC-mediated effects on important cellular components of innate and adaptive immunity. Due to their immunosuppressive properties, MSCs have emerged as promising tools for the treatment of inflammatory disorders such as acute graft-versus-host disease, graft rejection in patients undergoing organ/cell transplantation, and autoimmune diseases.

Efficacy and safety of mesenchymal stem cells for the treatment of patients infected with COVID-19: a systematic review and meta-analysis protocol

INTRODUCTION

To date, no specific antivirus drugs or vaccines have been available to prevent or treat the COVID-19 pandemic. Mesenchymal stem cell (MSC) therapy may be a promising therapeutic approach that reduces the high mortality in critical cases. This protocol is proposed for a systematic review and meta-analysis that aims to evaluate the efficacy and safety of MSC therapy on patients with COVID-19.

METHODS AND ANALYSIS

Ten databases including PubMed, EMBASE, Cochrane Library, CINAHL, Web of Science, Chinese National Knowledge Infrastructure (CNKI), Chinese Scientific Journals Database (VIP), Wanfang database, China Biomedical Literature Database (CBM) and Chinese Biomedical Literature Service System (SinoMed) will be searched from inception to 1 December 2020. All published randomised controlled trials, clinical controlled trials and case series that meet the prespecified eligibility criteria will be included. The primary outcomes include mortality, incidence and severity of adverse events, respiratory improvement, days from ventilator, duration of fever, progression rate from mild or moderate to severe, improvement of such serious symptoms as difficulty breathing or shortness of breath, chest pain or pressure, and loss of speech or movement, biomarkers of laboratory examination and changes in CT. The secondary outcomes include dexamethasone doses and quality of life. Two reviewers will independently perform study selection, data extraction and assessment of bias risk. Data synthesis will be conducted using RevMan software (V.5.3.5). If necessary, subgroup and sensitivity analysis will be performed. Grading of Recommendations Assessment, Development and Evaluation system will be used to assess the strength of evidence.

ETHICS AND DISSEMINATION

Ethical approval is not necessary since no individual patient or privacy data have been collected. The results of this review will be disseminated in a peer-reviewed journal or an academic conference presentation.

PROSPERO REGISTRATION NUMBER

CRD42020190079.

Immunomodulatory Effects of Mesenchymal Stem Cells and Mesenchymal Stem Cell-Derived Extracellular Vesicles in Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease that affects the joints and other organs for which there is currently no effective treatment. Mesenchymal stem cells (MSCs) have therapeutic potential due to their immunomodulatory and differentiation effects. While extensive experimental studies and clinical trials have demonstrated the effects of MSCs in various diseases, MSCs have been found to cause abnormal differentiation and tumor formation. Therefore, extracellular vesicles derived from MSCs (MSC-EVs) are more effective, less toxic, and more stable than the parental cells. MSC-EVs transfer various nucleic acids, proteins, and lipids from parent cells to recipient cells, and thus participate in chronic inflammatory and immune processes. In this review, we summarize the properties and biological functions of MSCs and MSC-EVs in RA. Improvement in our understanding of the mechanisms underlying MSC and MSC-EVs in RA provides an insight into potential biomarkers and therapeutic strategies for RA.

Bases for Treating Skin Aging With Artificial Mitochondrial Transfer/Transplant (AMT/T)

The perception of mitochondria as only the powerhouse of the cell has dramatically changed in the last decade. It is now accepted that in addition to being essential intracellularly, mitochondria can promote cellular repair when transferred from healthy to damaged cells. The artificial mitochondria transfer/transplant (AMT/T) group of techniques emulate this naturally occurring process and have been used to develop therapies to treat a range of diseases including cardiac and neurodegenerative. Mitochondria accumulate damage with time, resulting in cellular senescence. Skin cells and its mitochondria are profoundly affected by ultraviolet radiation and other factors that induce premature and accelerated aging. In this article, we propose the basis to use AMT/T to treat skin aging by transferring healthy mitochondria to senescent cells, possibly revitalizing them. We provide insightful information about how skin structure, components, and cells could age rapidly depending on the amount of damage received. Arguments are shown in favor of the use of AMT/T to treat aging skin and its cells, among them the possibility to stop free radical production, add new genetic material, and provide an energetic boost to help cells prolong their viability over time. This article intends to present one of the many aspects in which mitochondria could be used as a universal treatment for cell and tissue damage and aging.

Mechanisms behind the Immunoregulatory Dialogue between Mesenchymal Stem Cells and Th17 Cells

Mesenchymal stem cells (MSCs) exhibit potent immunoregulatory abilities by interacting with cells of the adaptive and innate immune system. In vitro, MSCs inhibit the differentiation of T cells into T helper 17 (Th17) cells and repress their proliferation. In vivo, the administration of MSCs to treat various experimental inflammatory and autoimmune diseases, such as rheumatoid arthritis, type 1 diabetes, multiple sclerosis, systemic lupus erythematosus, and bowel disease showed promising therapeutic results. These therapeutic properties mediated by MSCs are associated with an attenuated immune response characterized by a reduced frequency of Th17 cells and the generation of regulatory T cells. In this manuscript, we review how MSC and Th17 cells interact, communicate, and exchange information through different ways such as cell-to-cell contact, secretion of soluble factors, and organelle transfer. Moreover, we discuss the consequences of this dynamic dialogue between MSC and Th17 well described by their phenotypic and functional plasticity.

PPARβ/δ-dependent MSC metabolism determines their immunoregulatory properties

Mesenchymal stem cell (MSC)-based therapy is being increasingly considered a powerful opportunity for several disorders based on MSC immunoregulatory properties. Nonetheless, MSC are versatile and plastic cells that require an efficient control of their features and functions for their optimal use in clinic. Recently, we have shown that PPARβ/δ is pivotal for MSC immunoregulatory and therapeutic functions. However, the role of PPARβ/δ on MSC metabolic activity and the relevance of PPARβ/δ metabolic control on MSC immunosuppressive properties have never been addressed. Here, we demonstrate that PPARβ/δ deficiency forces MSC metabolic adaptation increasing their glycolytic activity required for their immunoregulatory functions on Th1 and Th17 cells. Additionally, we show that the inhibition of the mitochondrial production of ATP in MSC expressing PPARβ/δ, promotes their metabolic switch towards aerobic glycolysis to stably enhance their immunosuppressive capacities significantly. Altogether, these data demonstrate that PPARβ/δ governs the immunoregulatory potential of MSC by dictating their metabolic reprogramming and pave the way for enhancing MSC immunoregulatory properties and counteracting their versatility.

Mesenchymal Stem/Stromal Cell-Mediated Mitochondrial Transfer and the Therapeutic Potential in Treatment of Neurological Diseases

Mesenchymal stem/stromal cells (MSCs) are multipotent stem cells that can be derived from various tissues. Due to their regenerative and immunomodulatory properties, MSCs have been extensively researched and tested for treatment of different diseases/indications. One mechanism that MSCs exert functions is through the transfer of mitochondria, a key player involved in many biological processes in health and disease. Mitochondria transfer is bidirectional and has an impact on both donor and recipient cells. In this review, we discussed how MSC-mediated mitochondrial transfer may affect cellular metabolism, survival, proliferation, and differentiation; how this process influences inflammatory processes; and what is the molecular machinery that mediates mitochondrial transfer. In the end, we summarized recent advances in preclinical research and clinical trials for the treatment of stroke and spinal cord injury, through application of MSCs and/or MSC-derived mitochondria.

Multifaceted Roles of Mitochondrial Components and Metabolites in Metabolic Diseases and Cancer

Mitochondria are essential cellular components that ensure physiological metabolic functions. They provide energy in the form of adenosine triphosphate (ATP) through the electron transport chain (ETC). They also constitute a metabolic hub in which metabolites are used and processed, notably through the tricarboxylic acid (TCA) cycle. These newly generated metabolites have the capacity to feed other cellular metabolic pathways; modify cellular functions; and, ultimately, generate specific phenotypes. Mitochondria also provide intracellular signaling cues through reactive oxygen species (ROS) production. As expected with such a central cellular role, mitochondrial dysfunctions have been linked to many different diseases. The origins of some of these diseases could be pinpointed to specific mutations in both mitochondrial- and nuclear-encoded genes. In addition to their impressive intracellular tasks, mitochondria also provide intercellular signaling as they can be exchanged between cells, with resulting effects ranging from repair of damaged cells to strengthened progression and chemo-resistance of cancer cells. Several therapeutic options can now be envisioned to rescue mitochondria-defective cells. They include gene therapy for both mitochondrial and nuclear defective genes. Transferring exogenous mitochondria to target cells is also a whole new area of investigation. Finally, supplementing targeted metabolites, possibly through microbiota transplantation, appears as another therapeutic approach full of promises.

Use of Human Umbilical Cord and Its Byproducts in Tissue Regeneration

The fresh or cryopreserved human umbilical cord (HUC) and its byproducts, such as cells and extracts, have different uses in tissue regeneration. Defining what HUC byproduct is more effective in a particular application is a challenge. Furthermore, the methods of isolation, culture and preservation, may affect cell viability and regenerative properties. In this article, we review the HUC and its byproducts' applications in research and clinical practice. We present our results of successful use of HUC as a patch to treat gastroschisis and its potential to be applied in other conditions. Our in vitro results show an increase in proliferation and migration of human fibroblasts by using an acellular HUC extract. Our goal is to promote standardization of procedures and point out that applications of HUC and its byproducts, as well as the resulting advances in regenerative medicine, will depend on rigorous quality control and on more research in this area.

Where to Stand with Stromal Cells and Chronic Synovitis in Rheumatoid Arthritis?

The synovium exercises its main function in joint homeostasis through the secretion of factors (such as lubricin and hyaluronic acid) that are critical for the joint lubrication and function. The main synovium cell components are fibroblast-like synoviocytes, mesenchymal stromal/stem cells and macrophage-like synovial cells. In the synovium, cells of mesenchymal origin modulate local inflammation and fibrosis, and interact with different fibroblast subtypes and with resident macrophages. In pathologic conditions, such as rheumatoid arthritis, fibroblast-like synoviocytes proliferate abnormally, recruit mesenchymal stem cells from subchondral bone marrow, and influence immune cell activity through epigenetic and metabolic adaptations. The resulting synovial hyperplasia leads to secondary cartilage destruction, joint swelling, and pain. In the present review, we summarize recent findings on the molecular signature and the roles of stromal cells during synovial pannus formation and rheumatoid arthritis progression.