Exosomes: mediators of neurodegeneration, neuroprotection and therapeutics

Update on the application of mesenchymal stem cell-derived exosomes in the treatment of Parkinson's disease: A systematic review

Parkinson's disease (PD) has become the second largest neurodegenerative disease after Alzheimer's disease, and its incidence is increasing year by year. Traditional dopamine replacement therapy and deep brain stimulation can only alleviate the clinical symptoms of patients with PD but cannot cure the disease. In recent years, stem cell therapy has been used to treat neurodegenerative diseases. Many studies have shown that stem cell transplantation has a therapeutic effect on PD. Here, we review recent studies indicating that exosomes derived from mesenchymal stem cells also have the potential to treat PD in animal models, but the exact mechanism remains unclear. This article reviews the mechanisms through which exosomes are involved in intercellular information exchange, promote neuroprotection and freely cross the blood-brain barrier in the treatment of PD. The increase in the incidence of PD and the decline in the quality of life of patients with advanced PD have placed a heavy burden on patients, families and society. Therefore, innovative therapies for PD are urgently needed. Herein, we discuss the mechanisms underlying the effects of exosomes in PD, to provide new insights into the treatment of PD. The main purpose of this article is to explore the therapeutic potential of exosomes derived from mesenchymal stem cells and future research directions for this degenerative disease.

Delivering the Promise of Gene Therapy with Nanomedicines in Treating Central Nervous System Diseases

Central Nervous System (CNS) diseases, such as Alzheimer's diseases (AD), Parkinson's Diseases (PD), brain tumors, Huntington's disease (HD), and stroke, still remain difficult to treat by the conventional molecular drugs. In recent years, various gene therapies have come into the spotlight as versatile therapeutics providing the potential to prevent and treat these diseases. Despite the significant progress that has undoubtedly been achieved in terms of the design and modification of genetic modulators with desired potency and minimized unwanted immune responses, the efficient and safe in vivo delivery of gene therapies still poses major translational challenges. Various non-viral nanomedicines have been recently explored to circumvent this limitation. In this review, an overview of gene therapies for CNS diseases is provided and describes recent advances in the development of nanomedicines, including their unique characteristics, chemical modifications, bioconjugations, and the specific applications that those nanomedicines are harnessed to deliver gene therapies.

Perspectives on the Molecular Mediators of Oxidative Stress and Antioxidant Strategies in the Context of Neuroprotection and Neurolongevity: An Extensive Review

Molecules with at least one unpaired electron in their outermost shell are known as free radicals. Free radical molecules are produced either within our bodies or by external sources such as ozone, cigarette smoking, X-rays, industrial chemicals, and air pollution. Disruption of normal cellular homeostasis by redox signaling may result in cardiovascular, neurodegenerative diseases and cancer. Although ROS (reactive oxygen species) are formed in the GI tract, little is known about how they contribute to pathophysiology and disease etiology. When reactive oxygen species and antioxidants are in imbalance in our bodies, they can cause cell structure damage, neurodegenerative diseases, diabetes, hypercholesterolemia, atherosclerosis, cancer, cardiovascular diseases, metabolic disorders, and other obesity-related disorders, as well as protein misfolding, mitochondrial dysfunction, glial cell activation, and subsequent cellular apoptosis. Neuron cells are gradually destroyed in neurodegenerative diseases. The production of inappropriately aggregated proteins is strongly linked to oxidative stress. This review's goal is to provide as much information as possible about the numerous neurodegenerative illnesses linked to oxidative stress. The possibilities of multimodal and neuroprotective therapy in human illness, using already accessible medications and demonstrating neuroprotective promise in animal models, are highlighted. Neuroprotection and neurolongevity may improve from the use of bioactive substances from medicinal herbs like Allium stadium, Celastrus paniculatus, and Centella asiatica. Many neuroprotective drugs' possible role has been addressed. Preventing neuroinflammation has been demonstrated in several animal models.

Circular ribonucleic acid nucleoporin 98 knockdown alleviates high glucose-induced proliferation, fibrosis, inflammation and oxidative stress in human glomerular mesangial cells by regulating the microribonucleic acid-151-3p-high mobility group AT-hook 2 axis

AIMS/INTRODUCTION

This study aimed to investigate the role and mechanism of circular ribonucleic acid nucleoporin 98 (circNUP98) in diabetic nephropathy (DN).

MATERIALS AND METHODS

Human glomerular mesangial cells (HMCs) were stimulated with high glucose (HG) to imitate the growth environment of cells under the DN condition. Levels of genes and proteins were tested by quantitative reverse transcription polymerase chain reaction and western blot. Cell proliferation, apoptosis and inflammatory response were analyzed by using cell counting kit-8, flow cytometry and enzyme-linked immunosorbent assay analysis, respectively. Oxidative stress and fibrosis were evaluated by detecting the activity of reactive oxygen species, malondialdehyde, superoxide dismutase, fibronectin and collagen IV. The binding interaction between microribonucleic acid (miR)-151-3p and high mobility group AT-hook 2 (HMGA2) or circNUP98 was confirmed using dual-luciferase reporter, pull-down and ribonucleic acid immunoprecipitation assays. Exosomes were isolated by ultracentrifugation, and qualified by transmission electron microscopy, nanoparticle tracking analysis and western blot.

RESULTS

CircNUP98 expression was higher in the serum of DN patients and HG-stimulated HMCs. Functionally, circNUP98 knockdown alleviated HG-induced proliferation, fibrosis, inflammatory response and oxidative stress in HMCs. Mechanistically, circNUP98 directly sponged miR-151-3p, which targeted HMGA2. Rescue experiments showed that miR-151-3p reversed the inhibitory effects of circNUP98 knockdown on HG-induced HMC dysfunction. Furthermore, miR-151-3p re-expression also led to an inhibition of the aforementioned biological behaviors, which was attenuated by HMGA2 upregulation. Besides that, CircNUP98 was found to be packaged into exosomes of DN, and exosomal circNUP98 possessed diagnostic value for DN patients.

CONCLUSION

CircNUP98 knockdown alleviates HG-induced proliferation, fibrosis inflammation and oxidative stress in HMCs by regulating the miR-151-3p-HMGA2 axis, which might provide a potential approach for DN therapeutics.

Therapeutic utility of mesenchymal stromal cell (MSC)-based approaches in chronic neurodegeneration: a glimpse into underlying mechanisms, current status, and prospects

Recently, mesenchymal stromal cell (MSC)-based therapy has become an appreciated therapeutic approach in the context of neurodegenerative disease therapy. Accordingly, a myriad of studies in animal models and also some clinical trials have evinced the safety, feasibility, and efficacy of MSC transplantation in neurodegenerative conditions, most importantly in Alzheimer’s disease (AD), Parkinson’s disease (PD), amyotrophic lateral sclerosis (ALS), and Huntington’s disease (HD). The MSC-mediated desired effect is mainly a result of secretion of immunomodulatory factors in association with release of various neurotrophic factors (NTFs), such as glial cell line-derived neurotrophic factor (GDNF) and brain-derived neurotrophic factor (BDNF). Thanks to the secretion of protein-degrading molecules, MSC therapy mainly brings about the degradation of pathogenic protein aggregates, which is a typical appearance of chronic neurodegenerative disease. Such molecules, in turn, diminish neuroinflammation and simultaneously enable neuroprotection, thereby alleviating disease pathological symptoms and leading to cognitive and functional recovery. Also, MSC differentiation into neural-like cells in vivo has partially been evidenced. Herein, we focus on the therapeutic merits of MSCs and also their derivative exosome as an innovative cell-free approach in AD, HD, PD, and ALS conditions. Also, we give a brief glimpse into novel approaches to potentiate MSC-induced therapeutic merits in such disorders, most importantly, administration of preconditioned MSCs.

The Role of Exosomes as Mediators of Neuroinflammation in the Pathogenesis and Treatment of Alzheimer’s Disease

Alzheimer’s disease (AD) is a common neurodegenerative disease characterized by progressive dementia. Accumulation of β–amyloid peptide 1–42 and phosphorylation of tau protein in the brain are the two main pathological features of AD. However, comprehensive studies have shown that neuroinflammation also plays a crucial role in the pathogenesis of AD. Neuroinflammation is associated with neuronal death and abnormal protein aggregation and promotes the pathological process of β-amyloid peptide 1–42 and tau protein. The inflammatory components associated with AD include glial cells, complement system, cytokines and chemokines. In recent years, some researchers have focused on exosomes, a type of membrane nano vesicles. Exosomes can transport proteins, lipids, microRNAs and other signaling molecules to participate in a variety of signaling pathways for signal transmission or immune response, affecting the activity of target cells and participating in important pathophysiological processes. Therefore, exosomes play an essential role in intercellular communication and may mediate neuroinflammation to promote the development of AD. This paper reviews the occurrence and development of neuroinflammation and exosomes in AD, providing a deeper understanding of the pathogenesis of AD. Furthermore, the role of exosomes in the pathogenesis and treatment of AD is further described, demonstrating their potential as therapeutic targets for neuroinflammation and AD in the future.

Extracellular Vesicles Derived From Ex Vivo Expanded Regulatory T Cells Modulate In Vitro and In Vivo Inflammation

Extracellular vehicles (EVs) are efficient biomarkers of disease and participate in disease pathogenesis; however, their use as clinical therapies to modify disease outcomes remains to be determined. Cell-based immune therapies, including regulatory T cells (Tregs), are currently being clinically evaluated for their usefulness in suppressing pro-inflammatory processes. The present study demonstrates that ex vivo expanded Tregs generate a large pool of EVs that express Treg-associated markers and suppress pro-inflammatory responses in vitro and in vivo. Intravenous injection of Treg EVs into an LPS-induced mouse model of inflammation reduced peripheral pro-inflammatory transcripts and increased anti-inflammatory transcripts in myeloid cells as well as Tregs. Intranasal administration of enriched Treg EVs in this model also reduced pro-inflammatory transcripts and the associated neuroinflammatory responses. In a mouse model of amyotrophic lateral sclerosis, intranasal administration of enriched Treg EVs slowed disease progression, increased survival, and modulated inflammation within the diseased spinal cord. These findings support the therapeutic potential of expanded Treg EVs to suppress pro-inflammatory responses in human disease.

Cell-Derived Exosomes as Therapeutic Strategies and Exosome-Derived microRNAs as Biomarkers for Traumatic Brain Injury

Traumatic brain injury (TBI) is a complex, life-threatening condition that causes mortality and disability worldwide. No effective treatment has been clinically verified to date. Achieving effective drug delivery across the blood–brain barrier (BBB) presents a major challenge to therapeutic drug development for TBI. Furthermore, the field of TBI biomarkers is rapidly developing to cope with the many aspects of TBI pathology and enhance clinical management of TBI. Exosomes (Exos) are endogenous extracellular vesicles (EVs) containing various biological materials, including lipids, proteins, microRNAs, and other nucleic acids. Compelling evidence exists that Exos, such as stem cell-derived Exos and even neuron or glial cell-derived Exos, are promising TBI treatment strategies because they pass through the BBB and have the potential to deliver molecules to target lesions. Meanwhile, Exos have decreased safety risks from intravenous injection or orthotopic transplantation of viable cells, such as microvascular occlusion or imbalanced growth of transplanted cells. These unique characteristics also create Exos contents, especially Exos-derived microRNAs, as appealing biomarkers in TBI. In this review, we explore the potential impact of cell-derived Exos and exosome-derived microRNAs on the diagnosis, therapy, and prognosis prediction of TBI. The associated challenges and opportunities are also discussed.

Exosome: The “Off-the-Shelf” Cellular Nanocomponent as a Potential Pathogenic Agent, a Disease Biomarker, and Neurotherapeutics

Exosomes are nanosized “off-the-shelf” lipid vesicles released by almost all cell types and play a significant role in cell–cell communication. Exosomes have already been proven to carry cell-specific cargos of proteins, lipids, miRNA, and noncoding RNA (ribonucleic acid). These vesicles can be selectively taken up by the neighboring cell and can regulate cellular functions. Herein, we have discussed three different roles of exosomes in neuroscience. First, we have discussed how exosomes play the role of a pathogenic agent as a part of cell–cell communication and transmit pathogens such as amyloid-beta (Aβ), further helping in the propagation of neurodegenerative and other neurological diseases. In the next section, the review talks about the role of exosomes in biomarker discovery in neurological disorders. Toward the end, we have reviewed how exosomes can be harnessed and engineered for therapeutic purposes in different brain diseases. This review is based on the current knowledge generated in this field and our comprehension of this domain.

The Expression of Tax and HBZ Genes in Serum-Derived Extracellular Vesicles From HTLV-1 Carriers Correlates to Proviral Load and Inflammatory Markers

Human T-lymphotropic virus 1 (HTLV-1) is the etiologic agent of adult cell leukemia/lymphoma (ATL) and HTLV-1 associated myelopathy/tropical spastic paraparesis (HAM/TSP). One of the major questions in HTLV-1 studies is related to the understanding of causes that lead to different clinical manifestations. However, it is well known that the viral genes tax and HTLV-1 basic leucine zipper factor (HBZ) are related to viral infectivity and the development of neurological and hematological diseases. Currently, there is evidence that HTLV-1 infected cells can release small extracellular vesicles (sEVs) involved in the mechanisms of viral particles spreading. Therefore, we evaluated the expression levels of tax and HBZ viral transcripts in serum-derived sEVs from HTLV-1 carriers, as well as the role of these vesicles in the modulation of the immune response. Three HAM/TSP carriers presented detectable levels of tax and HBZ transcripts in sEVs and were positively correlated to the proviral load (PVL) in peripheral blood mononuclear cells (PBMCs). The viral transcripts were only detectable in individuals with a PVL higher than 6,000/10⁵ PBMCs. Additionally, it was observed that HBZ presented a 2–12-folds increase over tax expression units. Gene expression and secretory protein analysis indicated that PBMCs from blood donors and HTLV-1 carriers exposed to increasing doses of tax+ HBZ+ sEVs showed a dose-dependent increase in interferon (IFN)-γ and interleukin (IL)-8 transcripts and proteins. Interestingly, the increase in IL-8 levels was close to those seen in HTLV-1-infected PBMCs with high PVL. Taken together, these findings indicate that the expression of viral transcripts in serum-derived sEVs of HTLV-1 carriers is related to the PVL presented by the infected individual. Additionally, tax+ HBZ+ sEVs can induce the production of inflammatory cytokines in patients with low PVL, which may be related to the development of symptoms in HTLV-1 infection.

The Therapeutic Potential of Exosomes in Soft Tissue Repair and Regeneration

Soft tissue defects are common following trauma and tumor extirpation. These injuries can result in poor functional recovery and lead to a diminished quality of life. The healing of skin and muscle is a complex process that, at present, leads to incomplete recovery and scarring. Regenerative medicine may offer the opportunity to improve the healing process and functional outcomes. Barriers to regenerative strategies have included cost, regulatory hurdles, and the need for cell-based therapies. In recent years, exosomes, or extracellular vesicles, have gained tremendous attention in the field of soft tissue repair and regeneration. These nanosized extracellular particles (30-140 nm) can break the cellular boundaries, as well as facilitate intracellular signal delivery in various regenerative physiologic and pathologic processes. Existing studies have established the potential of exosomes in regenerating tendons, skeletal muscles, and peripheral nerves through different mechanisms, including promoting myogenesis, increasing tenocyte differentiation and enhancing neurite outgrowth, and the proliferation of Schwann cells. These exosomes can be stored for immediate use in the operating room, and can be produced cost efficiently. In this article, we critically review the current advances of exosomes in soft tissue (tendons, skeletal muscles, and peripheral nerves) healing. Additionally, new directions for clinical applications in the future will be discussed.

The Neurotoxicity of Vesicles Secreted by ALS Patient Myotubes Is Specific to Exosome-Like and Not Larger Subtypes

Extracellular vesicles can mediate communication between tissues, affecting the physiological conditions of recipient cells. They are increasingly investigated in Amyotrophic Lateral Sclerosis, the most common form of Motor Neurone Disease, as transporters of misfolded proteins including SOD1, FUS, TDP43, or other neurotoxic elements, such as the dipeptide repeats resulting from C9orf72 expansions. EVs are classified based on their biogenesis and size and can be separated by differential centrifugation. They include exosomes, released by the fusion of multivesicular bodies with the plasma membrane, and ectosomes, also known as microvesicles or microparticles, resulting from budding or pinching of the plasma membrane. In the current study, EVs were obtained from the myotube cell culture medium of ALS patients or healthy controls. EVs of two different sizes, separating at 20,000 or 100,000 g, were then compared in terms of their effects on recipient motor neurons, astrocytes, and myotubes. Compared to untreated cells, the smaller, exosome-like vesicles of ALS patients reduced the survival of motor neurons by 31% and of myotubes by 18%, decreased neurite length and branching, and increased the proportion of stellate astrocytes, whereas neither those of healthy subjects, nor larger EVs of ALS or healthy subjects, had such effects.

Engineering extracellular vesicles for Alzheimer's disease: An emerging cell-free approach for earlier diagnosis and treatment

Alzheimer's disease (AD) is a debilitating neurodegenerative disorder affecting over five million people globally and has no established cure. Current AD-related treatments only alleviate cognitive and behavioral symptoms and do not address disease onset or progression, underlining the unmet need to create an effective, innovative AD therapeutic. Extracellular vesicles (EVs) have emerged as a new class of nanotherapeutics. These secreted, lipid-bound cellular signaling carriers show promise for potential clinical applications for neurodegenerative diseases like AD. Additionally, analyzing contents and characteristics of patient-derived EVs may address the unmet need for earlier AD diagnostic techniques, informing physicians of altered genetic expression or cellular communications specific to healthy and diseased physiological states. There are numerous recent advances in regenerative medicine using EVs and include bioengineering perspectives to modify EVs, target glial cells in neurodegenerative diseases like AD, and potentially use EVs to diagnose and treat AD earlier. This article is categorized under: Neurological Diseases > Biomedical Engineering Neurological Diseases > Molecular and Cellular Physiology Neurological Diseases > Stem Cells and Development.

Mesenchymal stem cell-originated exosomal circDIDO1 suppresses hepatic stellate cell activation by miR-141-3p/PTEN/AKT pathway in human liver fibrosis

Liver fibrosis is a common pathologic stage of the development of liver failure. It has showed that exosomes loaded with therapeutic circRNAs can be manufactured in bulk by exosome secreted cells in vitro, thus enabling personalized treatment. This study aimed to investigate the role of exosome-based delivery of circDIDO1 in liver fibrosis. Levels of genes and proteins were examined by qRT-PCR and Western blot. Cell proliferation, apoptosis, and cell cycle were analyzed by using cell counting kit-8 (CCK-8) assay, EdU assay, and flow cytometry, respectively. The binding between circDIDO1 and miR-141-3p was confirmed by dual-luciferase reporter, RNA pull-down and RIP assays. Exosomes were isolated by ultracentrifugation, and qualified by transmission electron microscopy (TEM), nanoparticle tracking analysis (NTA) and Western blot. CircDIDO1 overexpression or miR-141-3p inhibition suppressed the proliferation, reduced pro-fibrotic markers, and induced apoptosis as well as cell cycle arrest in hepatic stellate cells (HSCs) by blocking PTEN/AKT pathway. Mechanistically, circDIDO1 acted as an endogenous sponge for miR-141-3p, further rescue experiments showed that circDIDO1 suppressed HSC activation by targeting miR-141-3p. Extracellular circDIDO1 could be incorporated into exosomes isolated from mesenchymal stem cells (MSCs), and transmitted to HSCs to restrain HSC activation. Clinically, low levels of serum circDIDO1 in exosome were correlated with liver failure, and serum exosomal circDIDO1 had a well diagnostic value for liver fibrosis in liver failure patients. Transfer of circDIDO1 mediated by MSC-isolated exosomes suppressed HSC activation through the miR-141-3p/PTEN/AKT pathway, gaining a new insight into the prevention of liver fibrosis in liver failure patients.

Tumor necrosis factor receptor-1 is selectively sequestered into Schwann cell extracellular vesicles where it functions as a TNFα decoy

Schwann cells (SCs) are known to produce extracellular vesicles (EV) that participate in cell-cell communication by transferring cargo to target cells, including mRNAs, microRNAs, and biologically active proteins. Herein, we report a novel mechanism whereby SC EVs may regulate PNS physiology, especially in injury, by controlling the activity of TNFα. SCs actively sequester tumor necrosis factor receptor-1 (TNFR1) into EVs at high density, accounting for about 2% of the total protein in SC EVs (~1000 copies TNFR1/EV). Although TNFR2 was robustly expressed by SCs in culture, TNFR2 was excluded from SC EVs. SC EV TNFR1 bound TNFα, decreasing the concentration of free TNFα available to bind to cells and thus served as a TNFα decoy. SC EV TNFR1 significantly inhibited TNFα-induced p38 MAPK phosphorylation in cultured SCs. When TNFR1 was proteolytically removed from SC EVs using tumor necrosis factor-α converting enzyme (TACE) or neutralized with antibody, the ability of TNFα to activate p38 MAPK in the presence of these EVs was restored. As further evidence of its decoy activity, SC EV TNFR1 modified TNFα activities in vitro including: (1) regulation of expression of other cytokines; (2) effects on SC morphology; and (3) effects on SC viability. SC EVs also modified the effects of TNFα on sciatic nerve morphology and neuropathic pain-related behavior in vivo. By sequestering TNFR1 in EVs, SCs may buffer against the potentially toxic effects of TNFα. SC EVs provide a novel mechanism for the spatial and temporal regulation of neuro-inflammation.

Extracellular Vesicles Derived from Young Neural Cultures Attenuate Astrocytic Reactivity In Vitro

Extracellular vesicles (EVs) play an important role in intercellular communication and are involved in both physiological and pathological processes. In the central nervous system (CNS), EVs secreted from different brain cell types exert a sundry of functions, from modulation of astrocytic proliferation and microglial activation to neuronal protection and regeneration. However, the effect of aging on the biological functions of neural EVs is poorly understood. In this work, we studied the biological effects of small EVs (sEVs) isolated from neural cells maintained for 14 or 21 days in vitro (DIV). We found that EVs isolated from 14 DIV cultures reduced the extracellular levels of lactate dehydrogenase (LDH), the expression levels of the astrocytic protein GFAP, and the complexity of astrocyte architecture suggesting a role in lowering the reactivity of astrocytes, while EVs produced by 21 DIV cells did not show any of the above effects. These results in an in vitro model pave the way to evaluate whether similar results occur in vivo and through what mechanisms.

Integrated view of molecular diagnosis and prognosis of dengue viral infection: future prospect of exosomes biomarkers

Dengue viruses (DENVs) are the viruses responsible for dengue infection which affects lungs, liver, heart and also other organs of individuals. DENVs consist of the group of four serotypically diverse dengue viruses transmitted in tropical and sub-tropical countries of world. Aedes mosquito is the principal vector which spread the infection from infected person to healthy humans. DENVs can cause different syndromes depending on serotype of virus which range from undifferentiated mild fever to dengue hemorrhagic fever resulting in vascular leakage due to release of cytokine and Dengue shock syndrome with fluid loss and hypotensive shock, or other severe manifestations such as bleeding and organ failure. Increase in dengue cases in pediatric population is a major concern. Transmission of dengue depends on various factors like temperature, rainfall, and distribution of Aedes aegypti mosquitoes. The present review describes a comprehensive overview of dengue, pathophysiology, diagnosis, treatment with an emphasis on potential of exosomes as biomarkers for early prediction of dengue in pediatrics.

BDE-47 induced PC-12 cell differentiation via TrkA downstream pathways and caused the loss of hippocampal neurons in BALB/c mice

As the most abundant congener of polybrominated diphenyl ethers (PBDEs) detected in environment and human biotic samples, 2, 2', 4, 4'-tetrabromodiphenyl ether (BDE-47) has been found to accumulate in brain and induce neurotoxicity, however, the detailed mechanism has not been clearly elucidated. To investigate the neurotoxicity of BDE-47, undifferentiated PC-12 cells were exposed to different doses of BDE-47, and BDE-47 dissolved in corn oil was orally administered to mice for 8 consecutive weeks. Our data showed that BDE-47 obviously changed cell morphology, altered cell viability, promoted cell apoptosis, and induced reactive oxygen species (ROS) production. BDE-47 promoted the differentiation of PC-12 cells by enhancing the expression of TrkA receptor and the phosphorylation levels of ERK and Akt. Moreover, BDE-47-induced differentiation of PC-12 cells was suppressed by inhibitors of corresponding pathways (MAPK/ERK and PI3K/Akt). H&E staining of brain showed neurons in DG and CA1 areas of hippocampus decreased after BDE-47 exposure. Transcriptome sequencing of brain tissue suggested that multiple signaling pathways related to neuron death and nerve function were significantly regulated. In conclusion, these results provided new evidence for revealing the neurotoxicity of BDE-47, and offered important experimental basis for environmental controlling and post-exposure health risk assessment of BDE-47.

When stem cells meet COVID-19: recent advances, challenges and future perspectives

Coronavirus disease 2019 (COVID-19) caused by the novel severe acute respiratory coronavirus 2 is currently spreading throughout the world with a high rate of infection and mortality and poses a huge threat to global public health. COVID-19 primarily manifests as hypoxic respiratory failure and acute respiratory distress syndrome, which can lead to multiple organ failure. Despite advances in the supportive care approaches, there is still a lack of clinically effective therapies, and there is an urgent need to develop novel strategies to fight this disease. Currently, stem cell therapy and stem cell-derived organoid models have received extensive attention as a new treatment and research method for COVID-19. Here, we discuss how stem cells play a role in the battle against COVID-19 and present a systematic review and prospective of the study on stem cell treatment and organoid models of COVID-19, which provides a reference for the effective control of the COVID-19 pandemic worldwide.

Harnessing Tissue-derived Extracellular Vesicles for Osteoarthritis Theranostics

Osteoarthritis (OA) is a prevalent chronic whole-joint disease characterized by low-grade systemic inflammation, degeneration of joint-related tissues such as articular cartilage, and alteration of bone structures that can eventually lead to disability. Emerging evidence has indicated that synovium or articular cartilage-secreted extracellular vesicles (EVs) contribute to OA pathogenesis and physiology, including transporting and enhancing the production of inflammatory mediators and cartilage degrading proteinases. Bioactive components of EVs are known to play a role in OA include microRNA, long non-coding RNA, and proteins. Thus, OA tissues-derived EVs can be used in combination with advanced nanomaterial-based biosensors for the diagnostic assessment of OA progression. Alternatively, mesenchymal stem cell- or platelet-rich plasma-derived EVs (MSC-EVs or PRP-EVs) have high therapeutic value for treating OA, such as suppressing the inflammatory immune microenvironment, which is often enriched by pro-inflammatory immune cells and cytokines that reduce chondrocytes apoptosis. Moreover, those EVs can be modified or incorporated into biomaterials for enhanced targeting and prolonged retention to treat OA effectively. In this review, we explore recently reported OA-related pathological biomarkers from OA joint tissue-derived EVs and discuss the possibility of current biosensors for detecting EVs and EV-related OA biomarkers. We summarize the applications of MSC-EVs and PRP-EVs and discuss their limitations for cartilage regeneration and alleviating OA symptoms. Additionally, we identify advanced therapeutic strategies, including engineered EVs and applying biomaterials to increase the efficacy of EV-based OA therapies. Finally, we provide our perspective on the future of EV-related diagnosis and therapeutic potential for OA treatment.

Exosomes derived from bone marrow mesenchymal stromal cells promote remyelination and reduce neuroinflammation in the demyelinating central nervous system

Injury of oligodendrocytes (OLs) induces demyelination, and patients with neurodegenerative diseases exhibit demyelination concomitantly with neurological deficit and cognitive impairment. Oligodendrocyte progenitor cells (OPCs) are present in the adult central nervous system (CNS), and they can proliferate, differentiate, and remyelinate axons after damage. However, remyelination therapies are not in clinical use. Multiple sclerosis (MS) is a major demyelinating disease in the CNS. Mesenchymal stromal cells (MSCs) have demonstrated therapeutic promise in animal models and in clinical trials of MS. Exosomes are nanoparticles generated by nearly all cells and they mediate cell-cell communication by transferring cargo biomaterials. Here, we hypothesize that exosomes harvested from MSCs have a similar therapeutic effect on enhancement of remyelination as that of MSCs. In the present study we employed exosomes derived from rhesus monkey MSCs (MSC-Exo). Two mouse models of demyelination were employed: 1) experimental autoimmune encephalomyelitis (EAE), an animal model of MS; and 2) cuprizone (CPZ) diet model, a toxic demyelination model. MSC-Exo or PBS were intravenously injected twice a week for 4 weeks, starting on day 10 post immunization in EAE mice, or once a week for 2 weeks starting on the day of CPZ diet withdrawal. Neurological and cognitive function were tested, OPC differentiation and remyelination, neuroinflammation and the potential underlying mechanisms were investigated using immunofluorescent staining, transmission electron microscopy and Western blot. Data generated from the EAE model revealed that MSC-Exo cross the blood brain barrier (BBB) and target neural cells. Compared with the controls (p < 0.05), treatment with MSC-Exo: 1) significantly improved neurological outcome; 2) significantly increased the numbers of newly generated OLs (BrdU+/APC+) and mature OLs (APC+), and the level of myelin basic protein (MBP); 3) decreased amyloid-β precursor protein (APP)+ density; 4) decreased neuroinflammation by increasing the M2 phenotype and decreasing the M1 phenotype of microglia, as well as their related cytokines; 5) inhibited the TLR2/IRAK1/NFκB pathway. Furthermore, we confirmed that the MSC-Exo treatment significantly improved cognitive function, promoted remyelination, increased polarization of M2 phenotype and blocked TLR2 signaling in the CPZ model. Collectively, MSC-Exo treatment promotes remyelination by both directly acting on OPCs and indirectly by acting on microglia in the demyelinating CNS. This study provides the cellular and molecular basis for this cell-free exosome therapy on remyelination and modulation of neuroinflammation in the CNS, with great potential for treatment of demyelinating and neurodegenerative disorders.

[Research progress of exosomes in treatment of osteoporosis]

Objective

To review the research progress of exosomes (EXOs) derived from different cells in the treatment of osteoporosis (OP).

Methods

Recent relevant literature about EXOs for OP therapy was extensively reviewed. And the related mechanism and clinical application prospect of EXOs derived from different cells in OP therapy were summarized and analyzed.

Results

EXOs derived from various cells, including bone marrow mesenchymal stem cells, osteoblasts, osteoclasts, osteocytes, and endothelial cells, et al, can participate in many links in the process of bone remodeling, and their mechanisms involve the regulation of proliferation and differentiation of bone-related cells, the promotion of vascular regeneration and immune regulation, and the suppression of inflammatory reactions. A variety of bioactive substances contained in EXOs are the basis of regulating the process of bone remodeling, and the combination of genetic engineering technology and EXOs-based drug delivery can further improve the therapeutic effect of OP.

Conclusion

EXOs derived from different cells have great therapeutic effects on OP, and have the advantages of low immunogenicity, high stability, strong targeting ability, and easy storage. EXOs has broad clinical application prospects and is expected to become a new strategy for OP treatment.

Exosomes, extracellular vesicles and the eye

Exosomes are a subset of extracellular vesicles which accommodate a cargo of bioactive biomolecules that generally includes proteins, nucleic acids, lipids, sugars, and related conjugates depicting the cellular environment and are known to mediate a wide array of biological functions, like cellular communication, cellular differentiation, immunomodulation, neovascularization, and cellular waste management. The exponential implication of exosomes in the pathological development and progression of various disorders including neurodegenerative diseases, cardiovascular diseases, and cancer has offered a tremendous opportunity for exploring their role in ocular conditions. Ocular diseases such as age-related macular disease, glaucoma, infectious endophthalmitis, diabetic retinopathy, autoimmune uveitis etc face various challenges in their early diagnosis and treatments due to contributing factors such as delay in the onset of symptoms, microbial identification, difficulty in obtaining samples for biopsy or being diagnosed as masquerade syndromes. Studies have reported unique exosomal cargos that are involved in successful delivery of miRNA or proteins to recipient cells to express desired expression or exploited as a diagnostic marker for various diseases. Furthermore, engineered exosomes can be used for targeted delivery of therapeutics and exosomes being natural nanoparticles found in all types of cells, host may not elicit an immune response against it. With the rapid advancement of opting personalized therapeutics, extending exosomal research to sight-threatening ocular infections can possibly advance the current diagnostic and therapeutic approaches. This review briefs about the current knowledge of exosomes in visual systems, advancements in exosomal and ophthalmic research, participation of exosomes in the pathogenesis of common ocular diseases, the challenges for exosomal therapies along with the future of this promising domain of research for diseases that fatally threaten billions of people worldwide.

Brain Exosomes: Friend or Foe in Alzheimer's Disease?

Alzheimer's disease (AD) is the most common neurodegenerative disease. It is known to be a multifactorial disease and several causes are associated with its occurrence as well as progression. However, the accumulation of amyloid beta (Aβ) is widely considered its major pathogenic hallmark. Additionally, neurofibrillary tangles (NFT), mitochondrial dysfunction, oxidative stress, and aging (cellular senescence) are considered as additional hits affecting the disease pathology. Several studies are now suggesting important role of inflammation in AD, which shifts our thought towards the brain's resident immune cells, microglia, and astrocytes; how they interact with neurons; and how these interactions are affected by intra and extracellular stressful factors. These interactions can be modulated by different mechanisms and pathways, in which exosomes could play an important role. Exosomes are multivesicular bodies secreted by nearly all types of cells. The exosomes secreted by glial cells or neurons affect the interactions and thus the physiology of these cells by transmitting miRNAs, proteins, and lipids. Exosomes can serve as a friend or foe to the neuron function, depending upon the carried signals. Exosomes, from the healthy microenvironment, may assist neuron function and health, whereas, from the stressed microenvironment, they carry oxidative and inflammatory signals to the neurons and thus prove detrimental to the neuronal function. Furthermore, exosomes can cross the blood-brain barrier (BBB), and from the blood plasma they can enter the brain cells and activate microglia and astrocytes. Exosomes can transport Aβ or Tau, cytokines, miRNAs between the cells, and alter the physiology of recipient cells. They can also assist in Aβ clearance and regulation of synaptic activity. The exosomes derived from different cells play different roles, and this field is still in its infancy stage. This review advocates exosomes' role as a friend or foe in neurodegenerative diseases, especially in the case of Alzheimer's disease.

Exosomal OTULIN from M2 macrophages promotes the recovery of spinal cord injuries via stimulating Wnt/β-catenin pathway-mediated vascular regeneration

Vascularization following spinal cord injury (SCI) provides trophic support for rebuilding up and maintaining the homeostasis of neuronal networks, and the promotion of angiogenesis is beneficial for functional recovery after SCI. M2 macrophages have been reported to exhibit powerful pro-angiogenic functions during tissue repair. Exosomes are important paracrine mediators of their parent cells and play critical roles in tissue regeneration. However, the role of M2 macrophage-derived exosomes (M2-Exos) in SCI is still largely unknown. In the present study, we determined that M2-Exos could augment the angiogenic activities of spinal cord microvascular endothelial cells (SCMECs) in vitro. Hydrogel-mediated sustained release of M2-Exos significantly promoted vascular regeneration and functional recovery in mice after SCI. Furthermore, proteomics analysis showed that ubiquitin thioesterase otulin (OTULIN) protein was highly enriched in M2-Exos. Functional assays demonstrated that OTULIN protein was required for the M2-Exos-induced pro-angiogenic effects in SCMECs, as well as positive effects on vascular regeneration, cell proliferation, and functional recovery in the mouse model of SCI. Mechanically, OTULIN from M2-Exos could activate the Wnt/β-catenin signaling by increasing the protein level of β-catenin via inhibiting its ubiquitination and trigger the expression of angiogenesis-related genes that are reported to be the downstream targets of Wnt/β-catenin signaling. Inhibition of the Wnt/β-catenin signaling by ICG001 markedly attenuated the pro-angiogenic activities of M2-Exos in vitro/vivo. Our findings indicate that M2-Exos positively modulate vascular regeneration and neurological functional recovery after SCI by activating Wnt/β-catenin signaling through the transfer of OTULIN protein. STATEMENT OF SIGNIFICANCE: M2 macrophages have been identified to promote vascular regeneration, cell proliferation and tissue growth after spinal cord injury (SCI), which is beneficial to the functional recovery. Exosomes are essential paracrine mediators involved in cell-to-cell communication and play important roles in tissue regeneration. In the present study, we revealed that M2 macrophages-derived exosomes (M2-Exos) could promote functional recovery post SCI by targeting angiogenesis. We demonstrated for the first time that OTULIN protein from M2-Exos mediated the angiogenic effects through activating Wnt/β-catenin signaling and triggering the expression of angiogenic-related genes in spinal cord microvascular endothelial cells (SCMECs). The hydrogel-M2-Exos sustained released system provides potential therapeutic clues of local cell-free interventions for the treatment of SCI.

Tango of dual nanoparticles: Interplays between exosomes and nanomedicine

Exosomes are lipid bilayer vesicles released from cells as a mechanism of intracellular communication. Containing information molecules of their parental cells and inclining to fuse with targeted cells, exosomes are valuable in disease diagnosis and drug delivery. The realization of their clinic applications still faces difficulties, such as lacking technologies for fast purification and functional reading. The advancement of nanotechnology in recent decades makes it promising to overcome these difficulties. In this article, we summarized recent progress in utilizing the physiochemical properties of nanoparticles (NPs) to enhance exosome purification and detection sensitivity or to derive novel technologies. We also discussed the valuable applications of exosomes in NPs‐based drug delivery. Till now most studies in these fields are still at the laboratory research stage. Translation of these bench works into clinic applications still has a long way to go.

Gene Therapy for Huntington's Disease: The Final Strategy for a Cure?

Huntington's disease (HD) has become a target of the first clinical trials for gene therapy among movement disorders with a genetic origin. More than 100 clinical trials regarding HD have been tried, but all failed, although there were some improvements limited to symptomatic support. Compared to other neurogenetic disorders, HD is known to have a single genetic target. Thus, this is an advantage and its cure is more feasible than any other movement disorder with heterogeneous genetic causes. In this review paper, the authors attempt to cover the characteristics of HD itself while providing an overview of the gene transfer methods currently being researched, and will introduce an experimental trial with a preclinical model of HD followed by an update on the ongoing clinical trials for patients with HD.

Exosomes from Human Umbilical Vein Endothelial Cells Ameliorate Ischemic Injuries by Suppressing the RNA Component of Mitochondrial RNA-processing Endoribonuclease via the Induction of miR-206/miR-1-3p Levels

Exosomes might mediate the effects of remote ischemic post-conditioning (RIPostC) treatment on vital organs. The present study aimed to explore the role of RNA component of mitochondrial RNA-processing endoribonuclease (RMRP) in the effects of human umbilical vein endothelial cell (HUVEC)-derived exosomes on ischemic injuries in vitro and in vivo. HUVECs were subjected to oxygen-glucose deprivation (OGD) treatment and exosomes were collected OGD-treated human neural cells were incubated with HUVEC-derived exosomes. Changes in cell viability, apoptosis, and RMRP-mediated PI3K/Akt/mTOR pathway activity were detected. The role of RMRP inhibition in the anti-OGD effects of exosomes was further determined by upregulating RMRP expression in human neural cells. The potential RMRP inhibitory factors in exosomes were explored using microarray detection. The effects of exosomes were validated with MCAO mouse models. In OGD neurons incubated with the exosomes, cell viability was improved and cell apoptosis was suppressed. At molecular level, exosomes on downregulated RMRP, p-PI3K, p-Akt, and p-mTOR, while induced eNOS. After the overexpression of RMRP, the cell protective effects of exosomes were counteracted, which was associated with the re-activation of PI3K/Akt/mTOR pathway. Based on the detection of microarray, the induced levels of miR-206 and miR-1-3p by OGD in HVUECs contributed to the RMPR inhibition. Additionally, injection of exosomes restricted infarction area and suppressed RMRP in MCAO mice. Collectively, exosomes from OGD HUVECs could protect neurons against ischemia-induced injuries, and the effects were associated with the suppression of RMRP in neurons via distance transfer of miR-206 and miR-1-3p.

Implications of exosomes derived from cholesterol-accumulated astrocytes in Alzheimer's disease pathology

Amyloid β (Aβ) peptides generated from the amyloid precursor protein (APP) play a critical role in the development of Alzheimer's disease (AD) pathology. Aβ-containing neuronal exosomes, which represent a novel form of intercellular communication, have been shown to influence the function/vulnerability of neurons in AD. Unlike neurons, the significance of exosomes derived from astrocytes remains unclear. In this study, we evaluated the significance of exosomes derived from U18666A-induced cholesterol-accumulated astrocytes in the development of AD pathology. Our results show that cholesterol accumulation decreases exosome secretion, whereas lowering cholesterol increases exosome secretion, from cultured astrocytes. Interestingly, exosomes secreted from U18666A-treated astrocytes contain higher levels of APP, APP-C-terminal fragments, soluble APP, APP secretases and Aβ1-40 than exosomes secreted from control astrocytes. Furthermore, we show that exosomes derived from U18666A-treated astrocytes can lead to neurodegeneration, which is attenuated by decreasing Aβ production or by neutralizing exosomal Aβ peptide with an anti-Aβ antibody. These results, taken together, suggest that exosomes derived from cholesterol-accumulated astrocytes can play an important role in trafficking APP/Aβ peptides and influencing neuronal viability in the affected regions of the AD brain.

Human Adipose Mesenchymal Stem Cell-derived Exosomes Protect Mice from DSS-Induced Inflammatory Bowel Disease by Promoting Intestinal-stem-cell and Epithelial Regeneration

Inflammatory bowel disease (IBD) remains a severe disease for most patients, with its incidence and prevalence increasingly globally. Currently, there is no effective treatments for IBD, and traditional treatments have multiple side effects. Therefore, novel therapeutic strategies or alternative drugs are urgently needed. Previous studies have shown that mesenchymal stem cell-derived exosomes have exhibited promising therapeutic effects on inflammatory disease. Here, we performed intravenous injection of human adipose mesenchymal stem cell (hADSC)-derived exosomes (hADSC-Exo) in a DSS-induced IBD mouse model and found that hADSC-Exo promoted functional recovery, downregulated inflammatory responses, reduced intestine cell apoptosis, increased epithelial regeneration and maintained intestinal barrier integrity. Moreover, we established a colon organoid, hADSC-Exo and TNF-α co-cultured system to explore the protective effect of hADSC-Exo on integrity of intestine mucosa and epithelial regeneration. We showed that hADSC-Exo not only can promote the proliferation and regeneration of Lgr5⁺ ISCs and epithelial cells but also ameliorate the inflammation damage in TNF-α induced inflammatory damaged mice colon organoids. Taken together, our findings indicate that hADSC-Exo protects intestine integrity, activates intestine epithelial cell and ISCs proliferation, suggesting that hADSC-Exo might be a potential effective treatment approach for IBD. We also provide a theoretical basis for new therapeutic strategies for cell-free therapy in inflammatory bowel disease.

IFNγ-stimulated dendritic cell extracellular vesicles can be nasally administered to the brain and enter oligodendrocytes

Extracellular vesicles secreted from IFNγ-stimulated rat dendritic cells (referred to here as IFNγ-DC-EVs) contain miRNAs which promote myelination (including but not limited to miR-219), and preferentially enter oligodendrocytes in brain slice cultures. IFNγ-DC-EVs also increase myelination when nasally administered to naïve rats. While we can infer that these extracellular vesicles enter the CNS from functional studies, here we demonstrate biodistribution throughout the brain after nasal delivery by way of imaging studies. After nasal administration, Xenolight DiR-labelled IFNγ-DC-EVs were detected 30 minutes later throughout the brain and the cervical spinal cord. We next examined cellular uptake of IFNγ-DC-EVs by transfecting IFNγ-DC-EVs with mCherry mRNA prior to nasal administration. mCherry-positive cells were found along the rostrocaudal axis of the brain to the brainstem. These cells morphologically resembled oligodendrocytes, and indeed cell-specific co-staining for neurons, astrocytes, microglia and oligodendrocytes showed that mcherry positive cells were predominantly oligodendrocytes. This is in keeping with our prior in vitro results showing that IFNγ-DC-EVs are preferentially taken up by oligodendrocytes, and to a lesser extent, microglia. To confirm that IFNγ-DC-EVs delivered cargo to oligodendrocytes, we quantified protein levels of miR-219 mRNA targets expressed in oligodendrocyte lineage cells, and found significantly reduced expression. Finally, we compared intranasal versus intravenous delivery of Xenolight DiR-labelled IFNγ-DC-EVs. Though labelled IFNγ-DC-EVs entered the CNS via both routes, we found that nasal delivery more specifically targeted the CNS with less accumulation in the liver. Taken together, these data show that intranasal administration is an effective route for delivery of IFNγ-DC-EVs to the CNS, and provides additional support for their development as an EV-based neurotherapeutic that, for the first time, targets oligodendrocytes.

Administration of Purified Exosome Product in a Rat Sciatic Serve Reverse Autograft Model

BACKGROUND

The nerve autograft remains the gold standard when reconstructing peripheral nerve defects. However, although autograft repair can result in useful functional recovery, poor outcomes are common, and better treatments are needed. The purpose of this study was to evaluate the effect of purified exosome product on functional motor recovery and nerve-related gene expression in a rat sciatic nerve reverse autograft model.

METHODS

Ninety-six Sprague-Dawley rats were divided into three experimental groups. In each group, a unilateral 10-mm sciatic nerve defect was created. The excised nerve was reversed and used to reconstruct the defect. Group I animals received the reversed autograft alone, group II animals received the reversed autograft with fibrin glue, and group III animals received the reversed autograft with purified exosome product suspended in the fibrin glue. The animals were killed at 3 and 7 days and 12 and 16 weeks after surgery. Evaluation included compound muscle action potentials, isometric tetanic force, tibialis anterior muscle wet weight, nerve regeneration-related gene expression, and nerve histomorphometry.

RESULTS

At 16 weeks, isometric tetanic force was significantly better in group III (p = 0.03). The average axon diameter of the peroneal nerve was significantly larger in group III at both 12 and 16 weeks (p = 0.015 at 12 weeks; p < 0.01 at 16 weeks). GAP43 and S100b gene expression was significantly up-regulated by purified exosome product.

CONCLUSIONS

Local administration of purified exosome product demonstrated improved nerve regeneration profiles in the reverse sciatic nerve autograft rat model. Thus, purified exosome product may have beneficial effects on nerve regeneration, gene profiles, and motor outcomes.

Oxidative Stress and the Neurovascular Unit

The neurovascular unit (NVU) is a relatively recent concept that clearly describes the relationship between brain cells and their blood vessels. The components of the NVU, comprising different types of cells, are so interrelated and associated with each other that they are considered as a single functioning unit. For this reason, even slight disturbances in the NVU could severely affect brain homeostasis and health. In this review, we aim to describe the current state of knowledge concerning the role of oxidative stress on the neurovascular unit and the role of a single cell type in the NVU crosstalk.

Inhibition of exosome release augments neuroinflammation following intracerebral hemorrhage

Intracerebral hemorrhage (ICH) is a severe stroke subtype without effective pharmacological treatment. Following ICH, peripheral leukocytes infiltrate into the brain and contribute to neuroinflammation and brain edema. However, the intercellular machinery controlling the initiation and propagation of leukocyte infiltration remains elusive. Exosomes are small extracellular vesicles released from donor cells and bridge intercellular communication. In this study, we investigated the effects of inhibition of exosome release on neuroinflammation and ICH injury. Using a mouse model of ICH induced by collagenase injection, we found that ICH induced an increase of exosome level in the brain. Inhibition of exosome release using GW4869 augmented neurological deficits and brain edema after ICH. The exacerbation of ICH injury was accompanied by increased barrier disruption and brain infiltration of leukocytes. The detrimental effects of GW4869 were ablated in ICH mice receiving antibody depletion of Gr-1⁺ myeloid cells. Extracted exosomes from the ICH brains suppressed the production of inflammatory factors by splenocytes. Additionally, exosomes extracted from brain tissues of donor ICH mice reduced ICH injury in recipient mice. These results demonstrate that inhibition of exosome release augments neuroinflammation and ICH injury. The impact of exosomes released from the ICH brain on the immune system deserves further investigation.

Brain-Derived Exosomal Proteins as Effective Biomarkers for Alzheimer's Disease: A Systematic Review and Meta-Analysis

Alzheimer's disease (AD), a progressive neurodegenerative disease, affects approximately 50 million people worldwide, which warrants the search for reliable new biomarkers for early diagnosis of AD. Brain-derived exosomal (BDE) proteins, which are extracellular nanovesicles released by all cell lineages of the central nervous system, have been focused as biomarkers for diagnosis, screening, prognosis prediction, and monitoring in AD. This review focused on the possibility of BDE proteins as AD biomarkers. The articles published prior to 26 January 2021 were searched in PubMed, EMBASE, Web of Science, and Cochrane Library to identify all relevant studies that reported exosome biomarkers in blood samples of patients with AD. From 342 articles, 20 studies were selected for analysis. We conducted a meta-analysis of six BDE proteins and found that levels of amyloid-β42 (standardized mean difference (SMD) = 1.534, 95% confidence interval [CI]: 0.595-2.474), total-tau (SMD = 1.224, 95% CI: 0.534-1.915), tau phosphorylated at threonine 181 (SMD = 4.038, 95% CI: 2.312-5.764), and tau phosphorylated at serine 396 (SMD = 2.511, 95% CI: 0.795-4.227) were significantly different in patients with AD compared to those in control. Whereas, those of p-tyrosine-insulin receptor substrate-1 and heat shock protein 70 did not show significant differences. This review suggested that Aβ42, t-tau, p-T181-tau, and p-S396-tau could be effective in diagnosing AD as blood biomarkers, despite the limitation in the meta-analysis based on the availability of data. Therefore, certain BDE proteins could be used as effective biomarkers for AD.

MSCs‑derived exosomes attenuate ischemia-reperfusion brain injury and inhibit microglia apoptosis might via exosomal miR-26a-5p mediated suppression of CDK6

Background

This study aimed to explore the role of mesenchymal stromal cells (MSCs)-derived exosomes (MSCs-Exo) in the cerebral ischemia–reperfusion (I/R) injury.

Methods

Exosomes were isolated from MSCs of adult C57BL/6J mice by the gradient centrifugation method. The expression of miR-26a-5p and CDK6 in MSCs-Exo and mice brain tissues were evaluated by qRT-PCR and western blot. miR-26a-5p mimics and miR-NC were transfected into MSCs, and exosomes were isolated from the MSCs stably expressing miR-26a-5p. Then MSCs-Exo-miR-26a-5p mimics or MSCs-Exo-miR-NC was injected into mice through the tail vein, or added into medium to stimulate BV-2 cells. Cell viability was evaluated by CCK-8 assay. Cell apoptosis was detected by flow cytometry. The apoptosis in brain tissues was evaluated by TUNEL staining assay. Bioinformatics analysis and luciferase reporter assay were performed to determine the binding relationship between miR-26a-5p and CDK6.

Results

miR-26a-5p was downregulated and CDK6 was upregulated in MSCs-Exo of MCAO-mice and OGD-induced MSCs. MSCs-Exo-miR-26a-5p mimics significantly reduced cell apoptosis of OGD-injured BV-2 cells. MSCs-Exo-miR-26a-5p mimics significantly reduced the infarct volume of MCAO-induced mice. Luciferase reporter assay revealed that CDK-6 was a target of miR-26a-5p. In addition, MSCs-Exo-miR-26a-5p mimics significantly decreased the expression of CDK6 in both OGD-induced BV-2 cells and the brain tissues of MCAO-treated mice.

Conclusion

Our results indicated that MSCs‑Exo attenuated I/R injury in mice by inhibiting microglia apoptosis might via exosomal miR-26a-5p mediated suppression of CDK6. Our study shed light on the application of MSC-Exo as a potential therapeutic tool for cerebral I/R injury.

The emerging role of exosomes in Alzheimer's disease

Alzheimer's disease (AD), manifested by memory loss and a decline in cognitive functions, is the most prevalent neurodegenerative disease accounting for 60-80 % of dementia cases. But, to-date, there is no effective treatment available to slow or stop the progression of AD. Exosomes are small extracellular vesicles that carry constituents, such as functional messenger RNAs, non-coding RNAs, proteins, lipids, DNA, and other bioactive substances of their source cells. In the brain, exosomes are likely to be sourced by almost all cell types and involve in cell communication to regulate cellular functions. The yet, accumulated evidence on the roles of exosomes and their constituents in the AD pathological process suggests their significance as additional biomarkers and therapeutic targets for AD. This review summarizes the current reported research findings on exosomes roles in the pathogenesis, diagnosis, and treatment of AD.

Stem Cell-Derived Exosomes: a New Strategy of Neurodegenerative Disease Treatment

Short-term symptomatic treatment and dose-dependent side effects of pharmacological treatment for neurodegenerative diseases have forced the medical community to seek an effective treatment for this serious global health threat. Therapeutic potential of stem cell for treatment of neurodegenerative disorders was identified in 1980 when fetal nerve tissue was used to treat Parkinson's disease (PD). Then, extensive studies have been conducted to develop this treatment strategy for neurological disease therapy. Today, stem cells and their secretion are well-known as a therapeutic environment for the treatment of neurodegenerative diseases. This new paradigm has demonstrated special characteristics related to this treatment, including neuroprotective and neurodegeneration, remyelination, reduction of neural inflammation, and recovery of function after induced injury. However, the exact mechanism of stem cells in repairing nerve damage is not yet clear; exosomes derived from them, an important part of their secretion, are introduced as responsible for an important part of such effects. Numerous studies over the past few decades have evaluated the therapeutic potential of exosomes in the treatment of various neurological diseases. In this review, after recalling the features and therapeutic history, we will discuss the latest stem cell-derived exosome-based therapies for these diseases.

Increased exosome secretion in neurons aging in vitro by NPC1-mediated endosomal cholesterol buildup

The present study unveils the molecular mechanism through which neurons in vitro compensate age-associated proteostasis defects by increasing exosome release.

As neurons age, they show a decrease in their ability to degrade proteins and membranes. Because undegraded material is a source of toxic products, defects in degradation are associated with reduced cell function and survival. However, there are very few dead neurons in the aging brain, suggesting the action of compensatory mechanisms. We show in this work that ageing neurons in culture show large multivesicular bodies (MVBs) filled with intralumenal vesicles (ILVs) and secrete more small extracellular vesicles than younger neurons. We also show that the high number of ILVs is the consequence of the accumulation of cholesterol in MVBs, which in turn is due to decreased levels of the cholesterol extruding protein NPC1. NPC1 down-regulation is the consequence of a combination of upregulation of the NPC1 repressor microRNA 33, and increased degradation, due to Akt-mTOR targeting of NPC1 to the phagosome. Although releasing more exosomes can be beneficial to old neurons, other cells, neighbouring and distant, can be negatively affected by the waste material they contain.

Orchestrating Extracellular Vesicle With Dual Reporters for Imaging and Capturing in Mammalian Cell Culture

Background: Recent technological advancements have enabled live-cell imaging of intracellular organelles to monitor their biogenesis in mammalian cells. However, applying this method to gain insight into extracellular organelles, such as extracellular vesicles (EVs), presents unique challenges that require special considerations in design and engineering.

Results: We have developed a dual-reporter system that combines genetic fusion, fluorescence microcopy and magnetic beads capture of EVs to study the biogenesis of EVs in mammalian cell cultures. First, we genetically produced a series of reporters by fusing a green fluorescent protein (GFP) and an affinity peptide (6xHis), with either the endogenous transmembrane protein, CD63, or EVs targeting vesicular stomatitis viral glycoprotein (VSVG). Transfection of these reporters into human 293T cells resulted in expression and integration of these reporters into pre-exosome compartments, which were subsequently released into the culture medium. Confocal imaging and nano-particle tracking analysis demonstrated that EVs were appropriately labeled and exhibited a single dominant peak in the 80–110 nm size range, indicating that isolated EVs were comprised of micro-vesicles and/or exosome subpopulations. Incubation of isolated EVs with nickel-coated magnetic beads resulted in successful capture of GFP-positive EVs. Finally, addition of EVs into culture medium was able to reveal the cellular uptake of GFP-labeled EVs by recipient cells. Taken together, our dual-reporter system provides a powerful method for both monitoring and capturing of EVs in mammalian cell culture systems.

Conclusion: A dual-reporter system provides a robust tool to study the life cycle of EVs in mammalian cells from biogenesis and excretion to cellular uptake.

Dysfunction of the Neurovascular Unit in Ischemic Stroke: Highlights on microRNAs and Exosomes as Potential Biomarkers and Therapy

Ischemic stroke is a damaging cerebral vascular disease associated with high disability and mortality rates worldwide. In spite of the continuous development of new diagnostic and prognostic methods, early detection and outcome prediction are often very difficult. The neurovascular unit (NVU) is a complex multicellular entity linking the interactions between neurons, glial cells, and brain vessels. Novel research has revealed that exosome-mediated transfer of microRNAs plays an important role in cell-to-cell communication and, thus, is integral in the multicellular crosstalk within the NVU. After a stroke, NVU homeostasis is altered, which induces the release of several potential biomarkers into the blood vessels. The addition of biological data representing all constituents of the NVU to clinical and neuroradiological findings can significantly advance stroke evaluation and prognosis. In this review, we present the current literature regarding the possible beneficial roles of exosomes derived from the components of the NVU and multipotent mesenchymal stem cells in preclinical studies of ischemic stroke. We also discuss the most relevant clinical trials on the diagnostic and prognostic roles of exosomes in stroke patients.

Stem cell-derived exosomes as a cell free therapy against spinal cord injury

Recent evidence suggests that stem cell therapy has beneficial effects on spinal cord injury. It was subsequently established that these beneficial effects may be mediated through release of paracrine factors, a kind of extracellular vesicle known as exosomes. Stem cell-secreted nano-sized exosomes have shown great potential to reduce apoptosis and inflammation, enhance angiogenesis, and improve functional behavioral recovery following spinal cord injury. This review summarizes current knowledge about the influence of exosomes derived from stem cells on spinal cord protection and regeneration with their molecular mechanisms after injury.

Diagnostic and Therapeutic Potential of Exosomal MicroRNAs for Neurodegenerative Diseases

Neurodegenerative disorders (NDs) are characterized by a gradual loss of neurons and functions that eventually leads to progressive neurological impairment. In view of the heavy burden on the healthcare system, efficient and reliable biomarkers for early diagnosis and therapeutic treatments to reverse the progression of NDs are in urgent need. There has been an increasing interest in using exosomal miRNAs as biomarkers or targeted therapies for neurological diseases recently. In this review, we overviewed the updated studies on exosomal miRNAs as biomarkers and potential therapeutic approaches in NDs, as well as their association with the pathophysiology of this group of disorders, especially Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), and Huntington's disease (HD). The exosomal miRNAs that are commonly dysregulated across different NDs or are commonly used as therapeutic candidates were also identified and summarized. In summary, the feasibility of exosomal miRNAs as biomarkers and potential targeted therapy for NDs has been verified. However, due to the limitations of existing studies and the discrepancies across different studies, high quality laboratory and clinical investigations are still required.

Exosomal microRNAs as Biomarkers and Therapeutic Targets for Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is the fifth most common cancer worldwide and the second most common cause of cancer-related death globally. This type of liver cancer is frequently detected at a late stage by current biomarkers because of the high clinical and biological heterogeneity of HCC tumours. From a plethora of molecules and cellular compounds, small nanoparticles with an endosomal origin are valuable cancer biomarkers or cargos for novel treatments. Despite their small sizes, in the range of 40–150 nm, these particles are delimited by a lipid bilayer membrane with a specific lipid composition and carry functional information—RNA, proteins, miRNAs, long non-coding RNAs (lncRNAs), or DNA fragments. This review summarizes the role of exosomal microRNA (miRNA) species as biomarkers in HCC therapy. After we briefly introduce the exosome biogenesis and the methods of isolation and characterization, we discuss miRNA’s correlation with the diagnosis and prognosis of HCC, either as single miRNA species, or as specific panels with greater clinical impact. We also review the role of exosomal miRNAs in the tumourigenic process and in the cell communication pathways through the delivery of cargos, including proteins or specific drugs.

Exosomes as a potential messenger unit during heterochronic parabiosis for amelioration of Huntington's disease

BACKGROUND

Huntington's disease (HD) starts its pathology long before clinical manifestation, however, there is no therapy to cure it completely and only a few studies have been reported for delaying the progression of HD. Recently, it has been shown that heterochronic parabiosis can modulate the neurodegenerative diseases. Despite the importance of the transportation process of positive factors during heterochronic parabiosis, there were limited understandings because the transportation process is nanoscale, which makes it difficult to identify the messenger unit. We demonstrated that heterochronic parabiosis could modulate HD in R6/2 mice model, and identified the messenger unit for transferring positive factors in the young blood serum.

METHODS

R6/2 mice were surgically connected with young wild-type mice (n = 13), old wild-type mice (n = 8), or R6/2 mice (n = 6) to examine the effect of heterochronic parabiosis. Parabionts composed of 5- to 6-week-old transgenic and wild-type mice were observed for 6 weeks in a single cage. The in vitro cellular model of HD cells were treated by the blood serum of the young or old mice, and by the exosomes isolated from thereof. The in vitro cellular model of HD were developed by differentiating neural stem cells cultured from SVZ of the brain.

RESULTS

After the heterochronic parabiosis, the weight loss and survival of HD mice was improved. Also, mutant Huntingtin aggregation (EM48 p < 0.005), improvement of mitochondria dysfunction (PGC-1a p < 0.05, p-CREB/CREB p < 0.005), cell death (p53 p < 0.05, Bax p < 0.05, Cleaved-caspase3 p < 0.05), and cognition (DCX p < 0.5) showed a near complete restoration. In addition, treating in vitro cellular model of HD by the exosomes from young blood serum improved mutant Huntingtin aggregation (EM48 p < 0.05), mitochondria biogenesis (p-CREB/CREB p < 0.005), cell death (p53 p < 0.05, Bax p < 0.005, Cleaved-caspase3 p < 0.05, Bcl-2 p < 0.05), and cell proliferation (WST-1 p < 0.005).

CONCLUSIONS

We found that the overall pathology of HD could be improved by the shared blood circulation through heterochronic parabiosis, furthermore, we demonstrated that the exosomes could be messengers for transferring positive factors, showing the potential of exosomes from young blood for the amelioration of HD.

Curcuma Longa, the "Golden Spice" to Counteract Neuroinflammaging and Cognitive Decline-What Have We Learned and What Needs to Be Done

Due to the global increase in lifespan, the proportion of people showing cognitive impairment is expected to grow exponentially. As target-specific drugs capable of tackling dementia are lagging behind, the focus of preclinical and clinical research has recently shifted towards natural products. Curcumin, one of the best investigated botanical constituents in the biomedical literature, has been receiving increased interest due to its unique molecular structure, which targets inflammatory and antioxidant pathways. These pathways have been shown to be critical for neurodegenerative disorders such as Alzheimer's disease and more in general for cognitive decline. Despite the substantial preclinical literature on the potential biomedical effects of curcumin, its relatively low bioavailability, poor water solubility and rapid metabolism/excretion have hampered clinical trials, resulting in mixed and inconclusive findings. In this review, we highlight current knowledge on the potential effects of this natural compound on cognition. Furthermore, we focus on new strategies to overcome current limitations in its use and improve its efficacy, with attention also on gender-driven differences.

Genetic Architecture and Molecular, Imaging and Prodromic Markers in Dementia with Lewy Bodies: State of the Art, Opportunities and Challenges

Dementia with Lewy bodies (DLB) is one of the most common causes of dementia and belongs to the group of α-synucleinopathies. Due to its clinical overlap with other neurodegenerative disorders and its high clinical heterogeneity, the clinical differential diagnosis of DLB from other similar disorders is often difficult and it is frequently underdiagnosed. Moreover, its genetic etiology has been studied only recently due to the unavailability of large cohorts with a certain diagnosis and shows genetic heterogeneity with a rare contribution of pathogenic mutations and relatively common risk factors. The rapid increase in the reported cases of DLB highlights the need for an easy, efficient and accurate diagnosis of the disease in its initial stages in order to halt or delay the progression. The currently used diagnostic methods proposed by the International DLB consortium rely on a list of criteria that comprises both clinical observations and the use of biomarkers. Herein, we summarize the up-to-now reported knowledge on the genetic architecture of DLB and discuss the use of prodromal biomarkers as well as recent promising candidates from alternative body fluids and new imaging techniques.

The Therapeutic Applications of Exosomes in Different Types of Diseases: A Review

Exosomes are nano-sized vesicles secreted by nearly all cells and have received massive attention recently. In addition to their roles in pathophysiological processes and diagnostic evaluations, recently, several studies have applied exosomes to design novel therapeutic applications. Exosomes can be derived from a variety of cells and tissues and based on the source, they can carry different native contents such as DNAs, non-coding small RNAs, mRNAs, and proteins. They can also be engineered by adding desirable agents including specific biomolecules or drugs. Both forms can be therapeutically used for delivering their cargoes to the target cells and desirably alter their functions. The present study aimed to provide a comprehensive review of the various studies which applied exosomes as a therapeutic tool in the treatment of different types of diseases including cancer, cardiovascular, neurologic, psychiatric, liver, and kidney diseases.

Neural Basis of Dental Pulp Stem Cells and its Potential Application in Parkinson's disease

Parkinson's disease (PD) is the second most common neurodegenerative disease after Alzheimer's disease. Though significant insights into the molecular-biochemical-cellular-behavioral basis of PD have been understood, there is no appreciable treatment available till date. Current therapies provide symptomatic relief without any influence on the progression of the disease. Stem cell therapy has been vigorously explored to treat PD. In this comprehensive review, we analyze various stem cell candidates for treating PD and discuss the possible mechanisms. We advocate the advantage of using neural crest originated dental pulp stem cells (DPSC) due to their predisposition towards neural differentiation and their potential to regenerate neurons far better than commonly used bone marrow derived mesenchymal stem cells (BM-MSCs). Eventually, we highlight the current challenges in the field and the strategies which may be used for overcoming the impediments.