The role of extracellular vesicles in the physiological and pathological regulation of the blood-brain barrier

MSC-derived extracellular vesicles: Precision miRNA delivery for overcoming cancer therapy resistance

Cancer remains a prominent worldwide health concern, presenting existing therapies with frequent difficulties, including major toxicity, limited effectiveness, and treatment resistance emergence. These issues highlight the necessity for novel and enhanced remedies. Exosomes, tiny extracellular vesicles that facilitate intercellular communication, have attracted interest for their potential medicinal applications. Carrying a variety of molecules, including microRNAs, small interfering RNAs, long non-coding RNAs, proteins, lipids, and DNA, these vesicles are positioned as promising cancer treatment options. Current studies have increasingly investigated the capacity of microRNAs as a strategic approach for combating malignancy. Mesenchymal stem cells (MSC) are recognized for their aptitude to augment blood vessel formation, safeguard against cellular death, and modulate immune responses. Consequently, researchers examine exosomes derived from MSCs as a safer, non-cellular choice over therapies employing MSCs, which risk undesirable differentiation. The focus is shifting towards employing miRNA-encapsulated exosomes sourced from MSCs to target and heal cancerous cells selectively. However, the exact functions of miRNAs within MSC-derived exosomes in the context of cancer are still not fully understood. Additional exploration is necessary to clarify the role of these miRNAs in malignancy progression and to pinpoint viable therapeutic targets. This review offers a comprehensive examination of exosomes derived from mesenchymal stem cells, focusing on the encapsulation of miRNAs, methods for enhancing cellular uptake and stability, and their potential applications in cancer treatment. It also addresses the difficulties linked to this methodology and considers future avenues, including insights from current clinical oncology research.

Tumor-derived vesicles in immune modulation: focus on signaling pathways

Tumor-derived extracellular vesicles (TDEVs) represent a heterogeneous population of extracellular vesicles (EVs), including exosomes, microvesicles, and apoptotic bodies, which are essential for tumor growth. EVs function as natural carriers of bioactive molecules, including lipids, proteins, and nucleic acids, enabling them to influence and regulate complex cellular interactions within the tumor microenvironment (TME). The TDEVs mainly have immunosuppressive functions as a result of the inhibitory signals disrupting the immune cell anti-tumor activity. They enhance tumor progression and immune evasion by inhibiting the effector function of immune cells and by altering critical processes of immune cell recruitment, polarization, and functional suppression by different signaling pathways. In this sense, TDEVs modulate the NF-κB pathway, promoting inflammation and inducing immune evasion. The Janus kinase (JAK)-signal transducer and activator of transcription (STAT) signaling is required for TDEV-mediated immune suppression and the manifestation of tumor-supporting features. The phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt)/mammalian target of rapamycin (mTOR) signaling, necessary for metabolic reprogramming, is orchestrated by TDEV to abrogate immune response and drive cancer cell proliferation. Finally, exosomal cargo can modulate the NOD-, LRR-, and pyrin domain-containing protein 3 (NLRP3) inflammasome, activating pro-inflammatory responses that influence tumor development and immunomodulation. In this review, we take a deep dive into how TDEVs affect the immune cells by altering key signaling pathways. We also examine emerging therapeutic approaches aimed at disrupting EV-mediated pathways, offering promising avenues for the development of novel EV-based cancer immunotherapy.

Platelet Extracellular Vesicles as Natural Delivery Vehicles for Mitochondrial Dysfunction Therapy?

Mitochondria are vital for energy production, metabolic regulation, and cellular signaling. Their dysfunction is strongly implicated in neurological, cardiovascular, and muscular degenerative diseases, where energy deficits and oxidative stress accelerate disease progression. Platelet extracellular vesicles (PEVs), once called "platelet dust", have emerged as promising agents for mitigating mitochondrial dysfunction. Like other extracellular vesicles (EVs), PEVs carry diverse molecular cargo and surface markers implicated in disease processes and therapeutic efficacy. Notably, they may possibly contain intact or partially functional mitochondrial components, making them tentatively attractive for targeting mitochondrial damage. Although direct research on PEVs-mediated mitochondrial rescue remains limited, current evidence suggests that PEVs can modulate diseases associated with mitochondrial dysfunction and potentially enhance mitochondrial health. This review explores the therapeutic potential of PEVs in neurodegenerative and cardiovascular disorders, highlighting their role in restoring mitochondrial health. By examining recent advancements in PEVs research, we aim to shed light on novel strategies for utilizing PEVs as therapeutic agents. Our goal is to underscore the importance of further fundamental and applied research into PEVs-based interventions, as innovative tools for combating a wide range of diseases linked to mitochondrial dysfunction.

Exosome-mediated communication between T cells and dendritic cells: Implications for therapeutic strategies

Cell communication is crucial for coordinating physiological functions in multicellular organisms, with exosomes playing a significant role. Exosomes mediate intercellular communication by transporting proteins, lipids, and nucleic acids between cells. These small, membrane-bound vesicles, derived from the endosomal pathway, are integral to various biological processes, including signal transmission and cellular behavior modulation. Recent advances highlight the potential of exosomes, especially dendritic cell-derived exosomes (DEXs), for diagnostic and therapeutic applications, particularly in cancer immunotherapy. DEXs are distinguished by their ability to present antigens and stimulate immune responses more effectively than exosomes from other cell types. They carry a cargo rich in immunostimulatory molecules and MHC-peptide complexes, which facilitate robust T-cell activation and enhance tumor-specific immune responses. The unique properties of DEXs, such as their ability to cross biological barriers and resist tumor-induced immunosuppression, position them as promising candidates for therapeutic applications. Here, I review the reports on the bidirectional interaction between dendritic cells and T cells through exosomes and their role in medicine.

Preserving Blood-Brain Barrier Integrity in Ischemic Stroke: a Review on MSCs-sEVs Content and Potential Molecular Targets

Ischemic stroke (IS) is a life-threatening condition that constitutes the second leading cause of death globally. Despite its high impact on public health, there is a shortage of treatments due to the complexity of the cellular and molecular mechanisms implicated. One main limiting factor for successful IS therapeutic intervention is stroke-induced blood-brain barrier (BBB) damage, particularly over tight junction proteins (TJs). BBB disruption is a well-established feature of IS, accelerating ischemic tissue damage and worsening prognosis. In recent years, mesenchymal stem cells (MSCs) and their small extracellular vesicles (MSCs-sEVs) have emerged as promising therapeutic interventions for several neurological disorders, including IS. However, its effects on BBB repair after IS are not completely understood. In this review, we will discuss novel experimental evidence of MSCs-sEVs effects in BBB protection and highlight the relevance of molecules reported in MSCs-sEVs, their potential cellular and molecular targets, and putative mechanisms implicated in BBB repair, providing a promising research avenue that may translate into effective therapeutic strategies for IS.

Impact of Psychological Stress and Spontaneous Tumour Regression on the Hippocampal Proteome in a Mouse Model of Breast Cancer

Cognitive impairment is common in people diagnosed with breast cancer, but the molecular mechanisms that underlie maladaptive changes in the brain are unknown. The psychological stress of a cancer diagnosis is certainly a contributing factor. Here, we investigated alterations in the hippocampal proteome in response to both cancer and psychological stress using label-free quantitative mass spectrometry techniques. An orthotopic syngeneic model of triple-negative breast cancer (TNBC) was established by injecting Py230 cells into the mammary fat pads of female C57Bl/6 mice. Half of the mice were subjected to a daily restraint stress paradigm. Mice that experienced both cancer and restraint stress lost weight and displayed larger tumours compared to non-stressed mice. Their urinary corticosterone levels were also elevated, as measured by enzyme-linked immunosorbent assay. Non-stressed tumour-bearing mice displayed higher levels of TNFα in the prefrontal cortex (PFC) compared to stressed mice with cancer. Flow cytometry results suggested that the CD4+/CD8+ T cell ratios were also raised in non-stressed tumour-bearing mice compared to both controls and stressed mice with TNBC. Bioinformatic analysis of hippocampal proteomes indicated that cancer alone causes reduced mitochondrial respiration and ATP synthesis, as well as impaired glutamate recycling and synaptic plasticity. Moreover, daily stress in TNBC mice caused further mitochondrial dysfunction, increased oxidative phosphorylation, and altered lipid metabolism. Importantly, over half of the mammary tumours that initially developed spontaneously regressed after 7-9 weeks in these young immunocompetent mice. Tumour regression inhibited TNFα increases in the PFC. However, the hippocampal proteomes of tumour-bearing mice were largely similar to mice in which tumours regressed, suggesting that spontaneous regression of breast cancer confers lasting physiological dysregulations that impact hippocampal protein expression. This study in mice may help to identify molecular mechanisms responsible for long-term memory impairments in cancer survivors and reveal novel drug targets for cancer-related cognitive impairment.

Exosome-based miRNA delivery: Transforming cancer treatment with mesenchymal stem cells

Recently, increasing interest has been in utilizing mesenchymal stem cell-derived extracellular vesicles (MSC-EVs), especially exosomes, as nanocarriers for miRNA delivery in cancer treatment. Due to such characteristics, nanocarriers are specific: biocompatible, low immunogenicity, and capable of spontaneous tumor accumulation. MSC-EVs were loaded with therapeutic miRNAs and minimized their susceptibility to degradation by protecting the miRNA from accessibility to degrading enzymes and providing targeted delivery of the miRNAs to the tumor cells to modulate oncogenic pathways. In vitro and in vivo experiments suggest that MSC-EVs loaded with miRNAs may inhibit tumor growth, prevent metastasis, and increase the effectiveness of chemotherapy and radiotherapy. However, these improvements present difficulties such as isolation, scalability, and stability of delivered miRNA during storage. Furthermore, the issues related to off-target effects, as well as immunogenicity, can be a focus. The mechanisms of miRNA loading into MSC-EVs, as well as their targeting efficiency and therapeutic potential, can be outlined in this manuscript. For the final part of the manuscript, the current advances in MSC-EV engineering and potential strategies for clinical application have been described. The findings of MSC-EVs imply that they present MSC-EVs as a second-generation tool for precise oncology.

Platelets tune fear memory in mice

Several lines of evidence have shown that platelet-derived factors are key molecules in brain-body communication in pathological conditions. Here, we identify platelets as key actors in the modulation of fear behaviors in mice through the control of inhibitory neurotransmission and plasticity in the hippocampus. Interfering with platelet number or activation reduces hippocampal serotonin (5-HT) and modulates fear learning and memory in mice, and this effect is reversed by serotonin replacement by serotonin precursor (5-HTP)/benserazide. In addition, we unravel that natural killer (NK) cells participate in this mechanism, regulating interleukin-13 (IL-13) levels in the gut, with effects on serotonin production by enterochromaffin cells and uptake by platelets. Both NK cells and platelet depletion reduce the activation of hippocampal inhibitory neurons and increase the long-term potentiation of synaptic transmission. Understanding the role of platelets in the modulation of neuro-immune interactions offers additional tools for the definition of the molecular and cellular elements involved in the growing field of brain-body communication.

Congenital Zika Syndrome: Insights from Integrated Proteomic and Metabolomic Analysis

Background: In this study, we investigated the role of extracellular vesicles (EVs) in the pathogenesis of Congenital Zika Syndrome (CZS). Previous studies have highlighted the role of EVs in intercellular communication and the modulation of biological processes during viral infections, motivating our in-depth analysis. Our objective was to identify specific molecular signatures in the EVs of patients with CZS, focusing on their potential as biomarkers and on cellular pathways affected by the infection. Methods: We conducted advanced proteomic and metabolomic analyses using mass spectrometry for protein and metabolite identification. EVs were isolated from CZS patient samples and control groups using Izon qEV size-exclusion chromatography columns. Results: The analyzed EVs presented distinct molecular profiles in patients with CZS. Proteomic analysis revealed significant alterations in specific proteins, suggesting involvement in the PI3K-AKT-mTOR pathway, while metabolomics highlighted metabolites related to critical processes in Zika virus pathogenesis. These findings suggest a key role for the PI3K-AKT-mTOR pathway in regulating cellular processes during infection and indicate the involvement of EVs in intercellular communication. Additionally, the results identified potential biomarkers capable of aiding early diagnosis and assessing disease progression. Conclusions: This study demonstrates that EVs play a crucial role in intercellular communication during Zika virus infection. The identification of specific alterations in the PI3K-AKT-mTOR pathway highlights a possible therapeutic target, providing new opportunities for the development of more effective treatment strategies for CZS. Our findings significantly advance the understanding of CZS and underscore the need for further investigations using advanced techniques to validate and explore these potential molecular targets.

Valosin-containing protein (VCP), a component of tumor-derived extracellular vesicles, impairs the barrier integrity of brain microvascular endothelial cells

Metastases are the leading cause of cancer-related deaths, and their origin is not fully elucidated. Recently, studies have shown that extracellular vesicles (EVs), particularly small extracellular vesicles (sEV), can disrupt the homeostasis of organs, promoting the development of a secondary tumor. However, the role of sEV in brain endothelium and their association with metastasis related to breast cancer is unknown. Thus, this study aimed to investigate sEV-triggered changes in the phosphorylation state of proteins on the surface of brain endothelial cells, as they form the first barrier in contact with circulating tumor cells and EVs, and once identified, to modulate its interactors and effects from this through different functional assays. We used the most aggressive breast cancer cell line, MDA-MB-231, and its brain-seeking variant, MDA-MB-231-br. From these cells, small and large extracellular vesicles were harvested to treat hCMEC/D3 cells, an immortalized cell line from the human brain microvasculature. Higher levels of phosphorylation of VEGFR1 and VEGFR2 were found in hCMEC/D3 cells treated with MDA-MB-231-br sEV. By computational analysis, the Valosin-Containing Protein (VCP) was predicted to be an important sEV cargo affecting the VEGFR2 intracellular trafficking, validated by western blotting analysis. Then, VCP was modulated by cell transfection or chemical inhibition in hCMEC/D3 cells and assessed in different functional in vitro assays evidencing a significant effect on the functionality of these cells. Thus, this study demonstrates that the VCP-containing sEVs induce modifications at different phosphor sites of VEGFR2 and effectively modulate the state of brain microvascular endothelial cells.

Engineering extracellular vesicles to transiently permeabilize the blood-brain barrier

BACKGROUND

Drug delivery to the brain is challenging due to the restrict permeability of the blood brain barrier (BBB). Recent studies indicate that BBB permeability increases over time during physiological aging likely due to factors (including extracellular vesicles (EVs)) that exist in the bloodstream. Therefore, inspiration can be taken from aging to develop new strategies for the transient opening of the BBB for drug delivery to the brain.

RESULTS

Here, we evaluated the impact of small EVs (sEVs) enriched with microRNAs (miRNAs) overexpressed during aging, with the capacity to interfere transiently with the BBB. Initially, we investigated whether the miRNAs were overexpressed in sEVs collected from plasma of aged individuals. Next, we evaluated the opening properties of the miRNA-enriched sEVs in a static or dynamic (under flow) human in vitro BBB model. Our results showed that miR-383-3p-enriched sEVs significantly increased BBB permeability in a reversible manner by decreasing the expression of claudin 5, an important tight junction protein of brain endothelial cells (BECs) of the BBB, mediated in part by the knockdown of activating transcription factor 4 (ATF4).

CONCLUSIONS

Our findings suggest that engineered sEVs have potential as a strategy for the temporary BBB opening, making it easier for drugs to reach the brain when injected into the bloodstream.

The hemostatic system in chronic brain diseases: A new challenging frontier?

Neurological diseases (ND), including neurodegenerative diseases (NDD) and psychiatric disorders (PD), present a significant public health challenge, ranking third in Europe for disability and premature death, following cardiovascular diseases and cancers. In 2017, approximately 540 million cases of ND were reported among Europe's 925 million people, with strokes, dementia, and headaches being most prevalent. Nowadays, more and more evidence highlight the hemostasis critical role in cerebral homeostasis and vascular events. Indeed, hemostasis, thrombosis, and brain abnormalities contributing to ND form a complex and poorly understood equilibrium. Alterations in vascular biology, particularly involving the blood-brain barrier, are implicated in ND, especially dementia, and PD. While the roles of key coagulation players such as thrombin and fibrinogen are established, the roles of other hemostasis components are less clear. Moreover, the involvement of these elements in psychiatric disease pathogenesis is virtually unstudied, except in specific pathological models such as antiphospholipid syndrome. Advanced imaging techniques, primarily functional magnetic resonance imaging and its derivatives like diffusion tensor imaging, have been developed to study brain areas affected by ND and to improve our understanding of the pathophysiology of these diseases. This literature review aims to clarify the current understanding of the connections between hemostasis, thrombosis, and neurological diseases, as well as explore potential future diagnostic and therapeutic strategies.

Perivascular Adipose Tissue and Perivascular Adipose Tissue-Derived Extracellular Vesicles: New Insights in Vascular Disease

Perivascular adipose tissue (PVAT) is a special deposit of fat tissue surrounding the vasculature. Previous studies suggest that PVAT modulates the vasculature function in physiological conditions and is implicated in the pathogenesis of vascular diseases. Understanding how PVAT influences vasculature function and vascular disease progression is important. Extracellular vesicles (EVs) are novel mediators of intercellular communication. EVs encapsulate molecular cargo such as proteins, lipids, and nucleic acids. EVs can influence cellular functions by transferring the carried bioactive molecules. Emerging evidence indicates that PVAT-derived EVs play an important role in vascular functions under health and disease conditions. This review will focus on the roles of PVAT and PVAT-EVs in obesity, diabetic, and metabolic syndrome-related vascular diseases, offering novel insights into therapeutic targets for vascular diseases.

Effect of the 35 nm and 70 nm Size Exclusion Chromatography (SEC) Column and Plasma Storage Time on Separated Extracellular Vesicles

The technical difficulty of separating extracellular vesicles (EVs) from plasma proteins in human blood presents a significant hurdle in EV research, particularly during nano ultra-high-performance liquid chromatography-tandem mass spectrometric (UHPLC-MS/MS) analysis, where detecting "vesicular" proteins among abundant plasma proteins is challenging. Standardisation is a pressing issue in EV research, prompting collaborative global efforts to address it. While the MISEV guidelines offer valuable recommendations, unanswered questions remain, particularly regarding sample storage. We compared size exclusion chromatography (SEC) columns with pore sizes of 35 nm and 70 nm to identify fractions with minimal contaminating proteins and the highest concentration of small EVs (sEVs). Following column selection, we explored potential differences in the quality and quantity of sEVs isolated from platelet-free plasma (PFP) after long-term storage at -80 °C (>2.5 years) compared to freshly drawn blood. Our methodologically rigorous study indicates that prolonged storage, under correct storage and processing conditions, does not compromise sEV quality. Both columns effectively isolated vesicles, with the 70 nm column exhibiting a higher abundance of "vesicular" proteins. We propose a relatively rapid and moderately efficient protocol for obtaining a comparatively pure sEV fraction from plasma, facilitating sEV processing in clinical trials.

Involvement of Astrocytes in the Formation, Maintenance, and Function of the Blood-Brain Barrier

The blood-brain barrier (BBB) is a fundamental structure that protects the composition of the brain by determining which ions, metabolites, and nutrients are allowed to enter the brain from the blood or to leave it towards the circulation. The BBB is structurally composed of a layer of brain capillary endothelial cells (BCECs) bound to each other through tight junctions (TJs). However, its development as well as maintenance and properties are controlled by the other brain cells that contact the BCECs: pericytes, glial cells, and even neurons themselves. Astrocytes seem, in particular, to have a very important role in determining and controlling most properties of the BBB. Here, we will focus on these latter cells, since the comprehension of their roles in brain physiology has been continuously expanding, even including the ability to participate in neurotransmission and in complex functions such as learning and memory. Accordingly, pathological conditions that alter astrocytic functions can alter the BBB's integrity, thus compromising many brain activities. In this review, we will also refer to different kinds of in vitro BBB models used to study the BBB's properties, evidencing its modifications under pathological conditions.

Biogenesis and delivery of extracellular vesicles: harnessing the power of EVs for diagnostics and therapeutics

Extracellular vesicles (EVs) are membrane-enclosed particles secreted by a variety of cell types. These vesicles encapsulate a diverse range of molecules, including proteins, nucleic acids, lipids, metabolites, and even organelles derived from their parental cells. While EVs have emerged as crucial mediators of intercellular communication, they also hold immense potential as both biomarkers and therapeutic agents for numerous diseases. A thorough understanding of EV biogenesis is crucial for the development of EV-based diagnostic developments since the composition of EVs can reflect the health and disease status of the donor cell. Moreover, when EVs are taken up by target cells, they can exert profound effects on gene expression, signaling pathways, and cellular behavior, which makes these biomolecules enticing targets for therapeutic interventions. Yet, despite decades of research, the intricate processes underlying EV biogenesis by donor cells and subsequent uptake by recipient cells remain poorly understood. In this review, we aim to summarize current insights and advancements in the biogenesis and uptake mechanisms of EVs. By shedding light on the fundamental mechanisms governing EV biogenesis and delivery, this review underscores the potential of basic mechanistic research to pave the way for developing novel diagnostic strategies and therapeutic applications.

Extracellular Vesicles' Role in Angiogenesis and Altering Angiogenic Signaling

Angiogenesis, the process of new blood vessels formation from existing vasculature, plays a vital role in development, wound healing, and various pathophysiological conditions. In recent years, extracellular vesicles (EVs) have emerged as crucial mediators in intercellular communication and have gained significant attention for their role in modulating angiogenic processes. This review explores the multifaceted role of EVs in angiogenesis and their capacity to modulate angiogenic signaling pathways. Through comprehensive analysis of a vast body of literature, this review highlights the potential of utilizing EVs as therapeutic tools to modulate angiogenesis for both physiological and pathological purposes. A good understanding of these concepts holds promise for the development of novel therapeutic interventions targeting angiogenesis-related disorders.

Extracellular Vesicles: A Promising Therapeutic Approach to Alzheimer's Disease

Extracellular vesicles (EVs) are nano-sized membranous particles that are secreted by various cell types and play a critical role in intercellular communication. Their unique properties and remarkable ability to deliver bioactive cargo to target cells have made them promising tools in the treatment of various diseases, including Alzheimer's disease (AD). AD is a devastating neurodegenerative disease characterized by progressive cognitive decline and neuropathological hallmarks, such as amyloid-beta plaques and neurofibrillary tangles. Despite extensive research, no disease-modifying therapy for AD is currently available. However, EVs have emerged as a potential therapeutic agent in AD due to their ability to cross the blood-brain barrier, deliver bioactive cargo, and modulate neuroinflammation. This review provides a comprehensive overview of the current knowledge on the role of EVs in AD and discusses their potential as a therapeutic approach. It covers the mechanisms of action, potential therapeutic targets, and challenges and limitations of EV-based therapies for AD.

Cerebral microvascular endothelial cell-derived extracellular vesicles regulate blood - brain barrier function

Autoreactive T lymphocytes crossing the blood-brain barrier (BBB) into the central nervous system (CNS) play a crucial role in the initiation of demyelination and neurodegeneration in multiple sclerosis (MS). Recently, extracellular vesicles (EV) secreted by BBB endothelial cells (BBB-EC) have emerged as a unique form of cell-to-cell communication that contributes to cerebrovascular dysfunction. However, the precise impact of different size-based subpopulations of BBB-EC-derived EV (BBB-EV) on the early stages of MS remains unclear. Therefore, our objective was to investigate the content and function of distinct BBB-EV subpopulations in regulating BBB integrity and their role in T cell transendothelial migration, both in vitro and in vivo. Our study reveals that BBB-ECs release two distinct size based EV populations, namely small EV (sEV; 30-150 nm) and large EV (lEV; 150-300 nm), with a significantly higher secretion of sEV during inflammation. Notably, the expression patterns of cytokines and adhesion markers differ significantly between these BBB-EV subsets, indicating specific functional differences in the regulation of T cell migration. Through in vitro experiments, we demonstrate that lEV, which predominantly reflect their cellular source, play a major role in BBB integrity loss and the enhanced migration of pro-inflammatory Th1 and Th17.1 cells. Conversely, sEV appear to protect BBB function by inducing an anti-inflammatory phenotype in BBB-EC. These findings align with our in vivo data, where the administration of sEV to mice with experimental autoimmune encephalomyelitis (EAE) results in lower disease severity compared to the administration of lEV, which exacerbates disease symptoms. In conclusion, our study highlights the distinct and opposing effects of BBB-EV subpopulations on the BBB, both in vitro and in vivo. These findings underscore the need for further investigation into the diagnostic and therapeutic potential of BBB-EV in the context of MS.

Enhancing Antibody Exposure in the Central Nervous System: Mechanisms of Uptake, Clearance, and Strategies for Improved Brain Delivery

Antibodies (mAbs) are attractive molecules for their application as a diagnostic and therapeutic agent for diseases of the central nervous system (CNS). mAbs can be generated to have high affinity and specificity to target molecules in the CNS. Unfortunately, only a very small number of mAbs have been specifically developed and approved for neurological indications. This is primarily attributed to their low exposure within the CNS, hindering their ability to reach and effectively engage their potential targets in the brain. This review discusses aspects of various barriers such as the blood-brain barrier (BBB) and blood-cerebrospinal fluid (CSF) barrier (BCSFB) that regulate the entry and clearance of mAbs into and from the brain. The roles of the glymphatic system on brain exposure and clearance are being described. We also discuss the proposed mechanisms of the uptake of mAbs into the brain and for clearance. Finally, several methods of enhancing the exposure of mAbs in the CNS were discussed, including receptor-mediated transcytosis, osmotic BBB opening, focused ultrasound (FUS), BBB-modulating peptides, and enhancement of mAb brain retention.

Neuro-HIV-New insights into pathogenesis and emerging therapeutic targets

HIV-associated neurocognitive disorders (HAND) is a term describing a complex set of cognitive impairments accompanying HIV infection. Successful antiretroviral therapy (ART) reduces the most severe forms of HAND, but milder forms affect over 50% of people living with HIV (PLWH). Pathogenesis of HAND in the ART era remains unknown. A variety of pathogenic factors, such as persistent HIV replication in the brain reservoir, HIV proteins released from infected brain cells, HIV-induced neuroinflammation, and some components of ART, have been implicated in driving HAND pathogenesis in ART-treated individuals. Here, we propose another factor-impairment of cholesterol homeostasis and lipid rafts by HIV-1 protein Nef-as a possible contributor to HAND pathogenesis. These effects of Nef on cholesterol may also underlie the effects of other pathogenic factors that constitute the multifactorial nature of HAND pathogenesis. The proposed Nef- and cholesterol-focused mechanism may provide a long-sought unified explanation of HAND pathogenesis that takes into account all contributing factors. Evidence for the impairment by Nef of cellular cholesterol balance, potential effects of this impairment on brain cells, and opportunities to therapeutically target this element of HAND pathogenesis are discussed.

Unravelling the Role of Cancer Cell-Derived Extracellular Vesicles in Muscle Atrophy, Lipolysis, and Cancer-Associated Cachexia

Cancer-associated cachexia is a metabolic syndrome that causes significant reduction in whole-body weight due to excessive loss of muscle mass accompanied by loss of fat mass. Reduced food intake and several metabolic abnormalities, such as increased energy expenditure, excessive catabolism, and inflammation, are known to drive cachexia. It is well documented that cancer cells secrete EVs in abundance which can be easily taken up by the recipient cell. The cargo biomolecules carried by the EVs have the potential to alter the signalling pathways and function of the recipient cells. EV cargo includes proteins, nucleic acids, lipids, and metabolites. Tumour-secreted EVs have been found to alter the metabolic and biological functions of adipose and muscle tissue, which aids in the development of the cachexia phenotype. To date, no medical intervention or FDA-approved drug exists that can completely reverse cachexia. Therefore, understanding how cancer-derived EVs contribute to the onset and progression of cancer-associated cachexia may help with the identification of new biomarkers as well as provide access to novel treatment alternatives. The goal of this review article is to discuss the most recent research on cancer-derived EVs and their function in cellular crosstalk that promotes catabolism in muscle and adipose tissue during cancer-induced cachexia.

No-stain protein labeling as a potential normalization marker for small extracellular vesicle proteins

Western blot analysis of relative protein expression relies on appropriate reference proteins for data normalization. Small extracellular vesicles (sEVs), or exosomes, are increasingly recognized as potential indicators of the physiological state of cells due to their protein composition. Therefore, accurate relative sEVs protein quantification is crucial for disease detection and prognosis applications. Currently, no documented ubiquitous reference proteins are identified for precise normalization of a protein of interest in sEVs. Here we showed the use of total protein staining method for sEVs protein normalization in western blots of samples where conventional housekeeping proteins like β-actin and glyceraldehyde 3-phosphate dehydrogenase (GAPDH) are not always detected in the sEVs western blots. The No-Stain™ Protein Labeling (NSPL) method showed high sensitivity in sEVs-protein labeling and facilitated quantitative evaluation of changes in the expression pattern of the protein of interest. Further, to show the robustness of NSPL for expression analysis, the results were compared with quantitative mass spectroscopy analysis results. Here, we outline a comprehensive method for protein normalization in sEVs that will increase the value of protein expression study of therapeutically significant sEVs.

Smart nano-sized extracellular vesicles for cancer therapy: Potential theranostic applications in gastrointestinal tumors

Extracellular vesicles (EVs) have gained tremendous interest in the search for next-generation therapeutics for the treatment of a range of pathologies, including cancer, especially due to their small size, biomolecular cargo, ability to mediate intercellular communication, high physicochemical stability, low immunogenicity and biocompatibility. The theranostic potential of EVs have been enhanced by adopting several strategies such as genetic or metabolic engineering, parental cell modification or direct functionalization to incorporate therapeutic compounds into these nanoplatforms. The smart nano-sized EVs indeed offer huge opportunities in the field of cancer, and current research is set at overcoming the existing pitfalls. Smart EVs are already being applied in the clinics despite the challenges faced. We provide, herein, an update on the technologies employed for EV functionalization in order to achieve optimal tumor cell targeting and EV tracking in vivo with bio-imaging modalities, as well as the preclinical and clinical studies making use of these modified EVs, in the context of gastrointestinal tumors.

Assessment of technical and clinical utility of a bead-based flow cytometry platform for multiparametric phenotyping of CNS-derived extracellular vesicles

BACKGROUND

Extracellular vesicles (EVs) originating from the central nervous system (CNS) can enter the blood stream and carry molecules characteristic of disease states. Therefore, circulating CNS-derived EVs have the potential to serve as liquid-biopsy markers for early diagnosis and follow-up of neurodegenerative diseases and brain tumors. Monitoring and profiling of CNS-derived EVs using multiparametric analysis would be a major advance for biomarker as well as basic research. Here, we explored the performance of a multiplex bead-based flow-cytometry assay (EV Neuro) for semi-quantitative detection of CNS-derived EVs in body fluids.

METHODS

EVs were separated from culture of glioblastoma cell lines (LN18, LN229, NCH82) and primary human astrocytes and measured at different input amounts in the MACSPlex EV Kit Neuro, human. In addition, EVs were separated from blood samples of small cohorts of glioblastoma (GB), multiple sclerosis (MS) and Alzheimer's disease patients as well as healthy controls (HC) and subjected to the EV Neuro assay. To determine statistically significant differences between relative marker signal intensities, an unpaired samples t-test or Wilcoxon rank sum test were computed. Data were subjected to tSNE, heatmap clustering, and correlation analysis to further explore the relationships between disease state and EV Neuro data.

RESULTS

Glioblastoma cell lines and primary human astrocytes showed distinct EV profiles. Signal intensities were increasing with higher EV input. Data normalization improved identification of markers that deviate from a common profile. Overall, patient blood-derived EV marker profiles were constant, but individual EV populations were significantly increased in disease compared to healthy controls, e.g. CD36+EVs in glioblastoma and GALC+EVs in multiple sclerosis. tSNE and heatmap clustering analysis separated GB patients from HC, but not MS patients from HC. Correlation analysis revealed a potential association of CD107a+EVs with neurofilament levels in blood of MS patients and HC.

CONCLUSIONS

The semi-quantitative EV Neuro assay demonstrated its utility for EV profiling in complex samples. However, reliable statistical results in biomarker studies require large sample cohorts and high effect sizes. Nonetheless, this exploratory trial confirmed the feasibility of discovering EV-associated biomarkers and monitoring circulating EV profiles in CNS diseases using the EV Neuro assay. Video Abstract.

Advancement in Cellular Topographic and Nanoparticle Capture Imaging by High Resolution Microscopy Incorporating a Freeze-Drying and Gaseous Nitrogen-based Approach

Scanning electron microscopy (SEM) offers an unparalleled view of the membrane topography of mammalian cells by using a conventional osmium (OsO4) and ethanol-based tissue preparation. However, conventional SEM methods limit optimal resolution due to ethanol and lipid interactions and interfere with visualization of fluorescent reporter proteins. Therefore, SEM correlative light and electron microscopy (CLEM) has been hindered by the adverse effects of ethanol and OsO4 on retention of fluorescence signals. To overcome this technological gap in achieving high-resolution SEM and retain fluorescent reporter signals, we developed a freeze-drying method with gaseous nitrogen (FDGN). We demonstrate that FDGN preserves cyto-architecture to allow visualization of detailed membrane topography while retaining fluorescent signals and that FDGN processing can be used in conjunction with a variety of high-resolution imaging systems to enable collection and validation of unique, high-quality data from these approaches. In particular, we show that FDGN coupled with high resolution microscopy provided detailed insight into viral or tumor-derived extracellular vesicle (TEV)-host cell interactions and may aid in designing new approaches to intervene during viral infection or to harness TEVs as therapeutic agents.

Exosomes: Potential Next-Generation Nanocarriers for the Therapy of Inflammatory Diseases

Inflammatory diseases are common pathological processes caused by various acute and chronic factors, and some of them are autoimmune diseases. Exosomes are fundamental extracellular vesicles secreted by almost all cells, which contain a series of constituents, i.e., cytoskeletal and cytosolic proteins (actin, tubulin, and histones), nucleic acids (mRNA, miRNA, and DNA), lipids (diacylglycerophosphates, cholesterol, sphingomyelin, and ceramide), and other bioactive components (cytokines, signal transduction proteins, enzymes, antigen presentation and membrane transport/fusion molecules, and adhesion molecules). This review will be a synopsis of the knowledge on the contribution of exosomes from different cell sources as possible therapeutic agents against inflammation, focusing on several inflammatory diseases, neurological diseases, rheumatoid arthritis and osteoarthritis, intestinal bowel disease, asthma, and liver and kidney injuries. Current knowledge indicates that the role of exosomes in the therapy of inflammation and in inflammatory diseases could be distinctive. The main limitations to their clinical translation are still production, isolation, and storage. Additionally, there is an urgent need to personalize the treatments in terms of the selection of exosomes; their dosages and routes of administration; and a deeper knowledge about their biodistribution, type and incidence of adverse events, and long-term effects of exosomes. In conclusion, exosomes can be a very promising next-generation therapeutic option, superior to synthetic nanocarriers and cell therapy, and can represent a new strategy of effective, safe, versatile, and selective delivery systems in the future.

Recent Advances in Extracellular Vesicles in Amyotrophic Lateral Sclerosis and Emergent Perspectives

Amyotrophic lateral sclerosis (ALS) is a severe and incurable neurodegenerative disease characterized by the progressive death of motor neurons, leading to paralysis and death. It is a rare disease characterized by high patient-to-patient heterogeneity, which makes its study arduous and complex. Extracellular vesicles (EVs) have emerged as important players in the development of ALS. Thus, ALS phenotype-expressing cells can spread their abnormal bioactive cargo through the secretion of EVs, even in distant tissues. Importantly, owing to their nature and composition, EVs' formation and cargo can be exploited for better comprehension of this elusive disease and identification of novel biomarkers, as well as for potential therapeutic applications, such as those based on stem cell-derived exosomes. This review highlights recent advances in the identification of the role of EVs in ALS etiopathology and how EVs can be promising new therapeutic strategies.

Engineered Extracellular Vesicles with Compound-Induced Cargo Delivery to Solid Tumors

Efficient delivery of functional factors into target cells remains challenging. Although extracellular vesicles (EVs) are considered to be potential therapeutic delivery vehicles, a variety of efficient therapeutic delivery tools are still needed for cancer cells. Herein, we demonstrated a promising method to deliver EVs to refractory cancer cells via a small molecule-induced trafficking system. We generated an inducible interaction system between the FKBP12-rapamycin-binding protein (FRB) domain and FK506 binding protein (FKBP) to deliver specific cargo to EVs. CD9, an abundant protein in EVs, was fused to the FRB domain, and the specific cargo to be delivered was linked to FKBP. Rapamycin recruited validated cargo to EVs through protein-protein interactions (PPIs), such as the FKBP-FRB interaction system. The released EVs were functionally delivered to refractory cancer cells, triple negative breast cancer cells, non-small cell lung cancer cells, and pancreatic cancer cells. Therefore, the functional delivery system driven by reversible PPIs may provide new possibilities for a therapeutic cure against refractory cancers.

Inflammatory Response and Exosome Biogenesis of Choroid Plexus Organoids Derived from Human Pluripotent Stem Cells

The choroid plexus (ChP) is a complex structure in the human brain that is responsible for the secretion of cerebrospinal fluid (CSF) and forming the blood-CSF barrier (B-CSF-B). Human-induced pluripotent stem cells (hiPSCs) have shown promising results in the formation of brain organoids in vitro; however, very few studies to date have generated ChP organoids. In particular, no study has assessed the inflammatory response and the extracellular vesicle (EV) biogenesis of hiPSC-derived ChP organoids. In this study, the impacts of Wnt signaling on the inflammatory response and EV biogenesis of ChP organoids derived from hiPSCs was investigated. During days 10-15, bone morphogenetic protein 4 was added along with (+/-) CHIR99021 (CHIR, a small molecule GSK-3β inhibitor that acts as a Wnt agonist). At day 30, the ChP organoids were characterized by immunocytochemistry and flow cytometry for TTR (~72%) and CLIC6 (~20%) expression. Compared to the -CHIR group, the +CHIR group showed an upregulation of 6 out of 10 tested ChP genes, including CLIC6 (2-fold), PLEC (4-fold), PLTP (2-4-fold), DCN (~7-fold), DLK1 (2-4-fold), and AQP1 (1.4-fold), and a downregulation of TTR (0.1-fold), IGFBP7 (0.8-fold), MSX1 (0.4-fold), and LUM (0.2-0.4-fold). When exposed to amyloid beta 42 oligomers, the +CHIR group had a more sensitive response as evidenced by the upregulation of inflammation-related genes such as TNFα, IL-6, and MMP2/9 when compared to the -CHIR group. Developmentally, the EV biogenesis markers of ChP organoids showed an increase over time from day 19 to day 38. This study is significant in that it provides a model of the human B-CSF-B and ChP tissue for the purpose of drug screening and designing drug delivery systems to treat neurological disorders such as Alzheimer's disease and ischemic stroke.

Emerging role of extracellular vesicles in multiple sclerosis: From cellular surrogates to pathogenic mediators and beyond

Multiple Sclerosis (MS) is a chronic, inflammatory demyelinating disease of the central nervous system (CNS) driven by a complex interplay of genetic and environmental factors. While the therapeutic arsenal has expanded significantly for management of relapsing forms of MS, treatment of individuals with progressive MS is suboptimal. This treatment inequality is in part due to an incomplete understanding of pathomechanisms at different stages of the disease-underscoring the critical need for new biomarkers. Extracellular vesicles (EVs) and their bioactive cargo have emerged as endogenous nanoparticles with great theranostic potential-as diagnostic and prognostic biomarkers and ultimately as therapeutic candidates for precision nanotherapeutics. The goals of this review are to: 1) summarize the current data investigating the role of EVs and their bioactive cargo in MS pathogenesis, 2) provide a high level overview of advances and challenges in EV isolation and characterization for translational studies, and 3) conclude with future perspectives on this evolving field.

Melanoma Cells Produce Large Vesicular-Bodies That Cause Rapid Disruption of Brain Endothelial Barrier-Integrity and Disassembly of Junctional Proteins

It is known that many cells produce extracellular vesicles, and this includes a range of different cancer cell types. Here we demonstrate the profound effects of large vesicular-like bodies produced by melanoma cells on the barrier integrity of human brain endothelial cells. These vesicular-bodies have not been fully characterised but range in size from ~500 nm to >10 µm, are surrounded by membrane and are enzymatically active based on cell-tracker incorporation. Their size is consistent with previously reported large oncosomes and apoptotic bodies. We demonstrate that these melanoma-derived vesicular-bodies rapidly affect brain endothelial barrier integrity, measured using ECIS biosensor technology, where the disruption is evident within ~60 min. This disruption involves acquisition of the vesicles through transcellular uptake into the endothelial cells. We also observed extensive actin-rearrangement, actin removal from the paracellular boundary of the endothelial cells and envelopment of the vesicular-bodies by actin. This was concordant with widespread changes in CD144 localisation, which was consistent with the loss of junctional strength. High-resolution confocal imaging revealed proximity of the melanoma vesicular-bodies juxtaposed to the endothelial nucleus, often containing fragmented DNA themselves, raising speculation over this association and potential delivery of nuclear material into the brain endothelial cells. The disruption of the endothelial cells occurs in a manner that is faster and completely distinct to that of invasion by intact melanoma cells. Given the clinical observation of large vesicles in the circulation of melanoma patients by others, we hypothesize their involvement in weakening or priming the brain vasculature for melanoma invasion.

Engineered EVs designed to target diseases of the CNS

Diseases of the central nervous system (CNS) are challenging to treat, mainly due to the blood-brain barrier (BBB), which restricts drugs in circulation from entering target regions in the brain. To address this issue extracellular vesicles (EVs) have gained increasing scientific interest as carriers able to cross the BBB with multiplex cargos. EVs are secreted by virtually every cell, and their escorted biomolecules are part of an intercellular information gateway between cells within the brain and with other organs. Scientists have undertaken efforts to safeguard the inherent features of EVs as therapeutic delivery vehicles, such as protecting and transferring functional cargo, as well as loading them with therapeutic small molecules, proteins, and oligonucleotides and targeting them to specific cell types for the treatment of CNS diseases. Here, we review current emerging approaches that engineer the EV surface and cargo to improve targeting and functional responses in the brain. We summarize existing applications of engineered EVs as a therapeutic delivery platform for brain diseases, some of which have been evaluated clinically.

Drug Delivery Systems in Regenerative Medicine: An Updated Review

Modern drug discovery methods led to evolving new agents with significant therapeutic potential. However, their properties, such as solubility and administration-related challenges, may hinder their benefits. Moreover, advances in biotechnology resulted in the development of a new generation of molecules with a short half-life that necessitates frequent administration. In this context, controlled release systems are required to enhance treatment efficacy and improve patient compliance. Innovative drug delivery systems are promising tools that protect therapeutic proteins and peptides against proteolytic degradation where controlled delivery is achievable. The present review provides an overview of different approaches used for drug delivery.

Engineered mesenchymal stem cell-derived extracellular vesicles: A state-of-the-art multifunctional weapon against Alzheimer's disease

With the increase of population aging, the number of Alzheimer's disease (AD) patients is also increasing. According to current estimates, approximately 11% of people over 65 suffer from AD, and that percentage rises to 42% among people over 85. However, no effective treatment capable of decelerating or stopping AD progression is available. Furthermore, AD-targeted drugs composed of synthetic molecules pose concerns regarding biodegradation, clearance, immune response, and neurotoxicity. Mesenchymal stem cell-derived extracellular vesicles (MSC-EVs) are essential intercellular communication mediators holding great promise as AD therapeutics owing to their biocompatibility, versatility, effortless storage, superior safety, and the ability to transport messenger and noncoding RNAs, proteins, lipids, DNAs, and other bioactive compounds derived from cells. The functionalisation and engineering strategies of MSC-EVs are highlighted (e.g. preconditioning, drug loading, surface modification, and artificial EV fabrication), which could improve AD treatment by multiple therapeutic effects, including clearing abnormal protein accumulation and achieving neuroprotection and immunomodulatory effects. Herein, this review summarises state-of-the-art strategies to engineer MSC-EVs, discusses progress in their use as AD therapeutics, presents the perspectives and challenges associated with the related clinical applications, and concludes that engineered MSC-EVs show immense potential in AD therapy.

Mechanistic Insights, Treatment Paradigms, and Clinical Progress in Neurological Disorders: Current and Future Prospects

Neurodegenerative diseases (NDs) are a major cause of disability and are related to brain development. The neurological signs of brain lesions can vary from mild clinical shortfalls to more delicate and severe neurological/behavioral symptoms and learning disabilities, which are progressive. In this paper, we have tried to summarize a collective view of various NDs and their possible therapeutic outcomes. These diseases often occur as a consequence of the misfolding of proteins post-translation, as well as the dysfunctional trafficking of proteins. In the treatment of neurological disorders, a challenging hurdle to cross regarding drug delivery is the blood-brain barrier (BBB). The BBB plays a unique role in maintaining the homeostasis of the central nervous system (CNS) by exchanging components between the circulations and shielding the brain from neurotoxic pathogens and detrimental compounds. Here, we outline the current knowledge about BBB deterioration in the evolving brain, its origin, and therapeutic interventions. Additionally, we summarize the physiological scenarios of the BBB and its role in various cerebrovascular diseases. Overall, this information provides a detailed account of BBB functioning and the development of relevant treatments for neurological disorders. This paper will definitely help readers working in the field of neurological scientific communities.

Dual role of brain-derived extracellular vesicles in dementia-related neurodegenerative disorders: cargo of disease spreading signals and diagnostic-therapeutic molecules

Neurodegenerative disorders are one of the most common causes of disability and represent 6.3% of the global burden of disease. Among them, Alzheimer's, Parkinson's, and Huntington's diseases cause cognitive decline, representing the most disabling symptom on both personal and social levels. The molecular mechanisms underlying the onset and progression of dementia are still poorly understood, and include secretory factors potentially affecting differentiated neurons, glial cells and neural stem cell niche. In the last decade, much attention has been devoted to exosomes as novel carriers of information exchanged among both neighbouring and distant cells. These vesicles can be generated and internalized by different brain cells including neurons, neural stem cells, astrocytes, and microglia, thereby affecting neural plasticity and cognitive functions in physiological and pathological conditions. Here, we review data on the roles of exosomes as carriers of bioactive molecules potentially involved in the pathogenesis of neurodegenerative disorders and detectable in biological fluids as biomarkers of dementia. We also discuss the experimental evidence of the therapeutic potential of stem cell-derived vesicles in experimental models of neurodegeneration-dependent cognitive decline.

Extracellular vesicles over adeno-associated viruses: Advantages and limitations as drug delivery platforms in precision medicine

Tissue-specific uptake and sufficient biodistribution are central goals in drug development. Crossing the blood-brain barrier (BBB) represents a major challenge in delivering therapeutics to the central nervous system (CNS). Since its discovery in the late 19th century, considerable efforts have been invested in an attempt to decipher the BBB structure complexity and plasticity. In parallel, another prevalent approach is to improve a delivery system by harnessing the biological machinery in an attempt to enhance therapeutic-agent permeability. Here, we review the advantages and limitations of using extracellular vesicles over AAV systems as a delivery system for therapy, focusing on neurodevelopmental disorders.

Molecular Docking and Intracellular Translocation of Extracellular Vesicles for Efficient Drug Delivery

Extracellular vesicles (EVs), including exosomes, mediate intercellular communication by delivering their contents, such as nucleic acids, proteins, and lipids, to distant target cells. EVs play a role in the progression of several diseases. In particular, programmed death-ligand 1 (PD-L1) levels in exosomes are associated with cancer progression. Furthermore, exosomes are being used for new drug-delivery systems by modifying their membrane peptides to promote their intracellular transduction via micropinocytosis. In this review, we aim to show that an efficient drug-delivery system and a useful therapeutic strategy can be established by controlling the molecular docking and intracellular translocation of exosomes. We summarise the mechanisms of molecular docking of exosomes, the biological effects of exosomes transmitted into target cells, and the current state of exosomes as drug delivery systems.

The evolving role of extracellular vesicles (exosomes) as biomarkers in traumatic brain injury: Clinical perspectives and therapeutic implications

Developing effective disease-modifying therapies for neurodegenerative diseases (NDs) requires reliable diagnostic, disease activity, and progression indicators. While desirable, identifying biomarkers for NDs can be difficult because of the complex cytoarchitecture of the brain and the distinct cell subsets seen in different parts of the central nervous system (CNS). Extracellular vesicles (EVs) are heterogeneous, cell-derived, membrane-bound vesicles involved in the intercellular communication and transport of cell-specific cargos, such as proteins, Ribonucleic acid (RNA), and lipids. The types of EVs include exosomes, microvesicles, and apoptotic bodies based on their size and origin of biogenesis. A growing body of evidence suggests that intercellular communication mediated through EVs is responsible for disseminating important proteins implicated in the progression of traumatic brain injury (TBI) and other NDs. Some studies showed that TBI is a risk factor for different NDs. In terms of therapeutic potential, EVs outperform the alternative synthetic drug delivery methods because they can transverse the blood–brain barrier (BBB) without inducing immunogenicity, impacting neuroinflammation, immunological responses, and prolonged bio-distribution. Furthermore, EV production varies across different cell types and represents intracellular processes. Moreover, proteomic markers, which can represent a variety of pathological processes, such as cellular damage or neuroinflammation, have been frequently studied in neurotrauma research. However, proteomic blood-based biomarkers have short half-lives as they are easily susceptible to degradation. EV-based biomarkers for TBI may represent the complex genetic and neurometabolic abnormalities that occur post-TBI. These biomarkers are not caught by proteomics, less susceptible to degradation and hence more reflective of these modifications (cellular damage and neuroinflammation). In the current narrative and comprehensive review, we sought to discuss the contemporary knowledge and better understanding the EV-based research in TBI, and thus its applications in modern medicine. These applications include the utilization of circulating EVs as biomarkers for diagnosis, developments of EV-based therapies, and managing their associated challenges and opportunities.

The profile of inflammatory extracellular vesicles in intracerebral hemorrhage patients

Background

Intracerebral hemorrhage (ICH) is one of the leading life-threatening types of strokes with high mortality. A prominent feature of ICH is neuroinflammation involving leukocytes, such as neutrophils and macrophages. Large extracellular vesicles (lEV) and small extracellular vesicles (sEV) released from various cells are used as biomarkers for different diseases. Here, we aimed to determine the concentration/population of lEV and sEV from different leukocytes in ICH patients and analyze the correlation of these lEV/sEV with clinical parameters.

Methods

lEV and sEV were isolated from the plasma of ICH patients (n = 39) by using the serial centrifuge methods. Nanoparticle tracking analysis (NTA, NS300) was used to determine the type and concentration of different leukocytes-released lEV/sEV. Specific antibodies, CD66b, P2RY12, and CD80 were used for different leukocyte types.

Results

A predictive relationship between both hospital length of stay (R 2 = 0.83) and Intensive care units (ICU) length of stay (R 2 = 0.88) was found with lEV and sEV and patient data [including low-density lipoprotein (LDL), ICH volume, etc.]. Further predictive-multiple linear regression relationship was seen between lEV and sEV concentrations and MRSV3 (Modified Rankin Scale at 90 days) (R 2 = 0.46) and MRSV5 (modified Rankin Scale at 180 days) (R 2 = 0.51). Additionally, a slight, but statistically significant (p = 0.0151), multiple linear regression relationship was seen between lEV and sEV concentrations and ICU length of stay (R 2 = 0.26).

Conclusion

This study found predictive relationships between patient outcomes and lEV and sEV. When combined with generally collected patient data (LDL, etc.), measurements of lEV and sEV are strongly predictive of overall patient outcome. Further, larger studies should investigate these effects.

Neurovascular Unit-Derived Extracellular Vesicles: From Their Physiopathological Roles to Their Clinical Applications in Acute Brain Injuries

Extracellular vesicles (EVs) form a heterogeneous group of membrane-enclosed structures secreted by all cell types. EVs export encapsulated materials composed of proteins, lipids, and nucleic acids, making them a key mediator in cell–cell communication. In the context of the neurovascular unit (NVU), a tightly interacting multicellular brain complex, EVs play a role in intercellular communication and in maintaining NVU functionality. In addition, NVU-derived EVs can also impact peripheral tissues by crossing the blood–brain barrier (BBB) to reach the blood stream. As such, EVs have been shown to be involved in the physiopathology of numerous neurological diseases. The presence of NVU-released EVs in the systemic circulation offers an opportunity to discover new diagnostic and prognostic markers for those diseases. This review outlines the most recent studies reporting the role of NVU-derived EVs in physiological and pathological mechanisms of the NVU, focusing on neuroinflammation and neurodegenerative diseases. Then, the clinical application of EVs-containing molecules as biomarkers in acute brain injuries, such as stroke and traumatic brain injuries (TBI), is discussed.

The roles of extracellular vesicles in the immune system

The twenty-first century has witnessed major developments in the field of extracellular vesicle (EV) research, including significant steps towards defining standard criteria for the separation and detection of EVs. The recent recognition that EVs have the potential to function as biomarkers or as therapeutic tools has attracted even greater attention to their study. With this progress in mind, an updated comprehensive overview of the roles of EVs in the immune system is timely. This Review summarizes the roles of EVs in basic processes of innate and adaptive immunity, including inflammation, antigen presentation, and the development and activation of B cells and T cells. It also highlights key progress related to deciphering the roles of EVs in antimicrobial defence and in allergic, autoimmune and antitumour immune responses. It ends with a focus on the relevance of EVs to immunotherapy and vaccination, drawing attention to ongoing or recently completed clinical trials that aim to harness the therapeutic potential of EVs.

Role of pericytes in blood-brain barrier preservation during ischemia through tunneling nanotubes

Crosstalk mechanisms between pericytes, endothelial cells, and astrocytes preserve integrity and function of the blood-brain-barrier (BBB) under physiological conditions. Long intercellular channels allowing the transfer of small molecules and organelles between distant cells called tunneling nanotubes (TNT) represent a potential substrate for energy and matter exchanges between the tripartite cellular compartments of the BBB. However, the role of TNT across BBB cells under physiological conditions and in the course of BBB dysfunction is unknown. In this work, we analyzed the TNT's role in the functional dialog between human brain endothelial cells, and brain pericytes co-cultured with human astrocytes under normal conditions or after exposure to ischemia/reperfusion, a condition in which BBB breakdown occurs, and pericytes participate in the BBB repair. Using live time-lapse fluorescence microscopy and laser-scanning confocal microscopy, we found that astrocytes form long TNT with pericytes and endothelial cells and receive functional mitochondria from both cell types through this mechanism. The mitochondrial transfer also occurred in multicellular assembloids of human BBB that reproduce the three-dimensional architecture of the BBB. Under conditions of ischemia/reperfusion, TNT formation is upregulated, and astrocytes exposed to oxygen-glucose deprivation were rescued from apoptosis by healthy pericytes through TNT-mediated transfer of functional mitochondria, an effect that was virtually abolished in the presence of TNT-destroying drugs. The results establish a functional role of TNT in the crosstalk between BBB cells and demonstrate that TNT-mediated mitochondrial transfer from pericytes rescues astrocytes from ischemia/reperfusion-induced apoptosis. Our data confirm that the pericytes might play a pivotal role in preserving the structural and functional integrity of BBB under physiological conditions and participate in BBB repair in brain diseases.

Extracellular Vesicles at CNS barriers: Mode of action

The exchange of molecules between the brain and periphery is limited by cellular barriers such as the blood-brain barrier (BBB) and the blood-CSF barrier (BCB). Extracellular vesicles (EVs) secreted by brain cells or circulating in the blood stream interact with these barriers and provide a pathway for brain-periphery communication. This review briefly summarizes the main current concepts of EVs signaling over the BBB/BCB. EVs can either be released by barrier cells upon stimulation, act on barrier cells modulating barrier properties, or cross the barrier transferring cargo between the circulation and the brain. The mechanisms of EV signaling and passage over the BBB are increasingly being explored, with inflammation being a main driver. EVs acting at or through the barriers possess wide-ranging effects on brain-periphery communication in both healthy and pathological states. A deeper understanding of the mechanisms of action is important for translation into biomedical applications for brain diseases.

Huntingtin Co-Isolates with Small Extracellular Vesicles from Blood Plasma of TgHD and KI-HD Pig Models of Huntington's Disease and Human Blood Plasma

(1) Background: Huntington’s disease (HD) is rare incurable hereditary neurodegenerative disorder caused by CAG repeat expansion in the gene coding for the protein huntingtin (HTT). Mutated huntingtin (mHTT) undergoes fragmentation and accumulation, affecting cellular functions and leading to neuronal cell death. Porcine models of HD are used in preclinical testing of currently emerging disease modifying therapies. Such therapies are aimed at reducing mHTT expression, postpone the disease onset, slow down the progression, and point out the need of biomarkers to monitor disease development and therapy efficacy. Recently, extracellular vesicles (EVs), particularly exosomes, gained attention as possible carriers of disease biomarkers. We aimed to characterize HTT and mHTT forms/fragments in blood plasma derived EVs in transgenic (TgHD) and knock-in (KI-HD) porcine models, as well as in HD patients’ plasma. (2) Methods: Small EVs were isolated by ultracentrifugation and HTT forms were visualized by western blotting. (3) Results: The full length 360 kDa HTT co-isolated with EVs from both the pig model and HD patient plasma. In addition, a ~70 kDa mutant HTT fragment was specific for TgHD pigs. Elevated total huntingtin levels in EVs from plasma of HD groups compared to controls were observed in both pig models and HD patients, however only in TgHD were they significant (p = 0.02). (4) Conclusions: Our study represents a valuable initial step towards the characterization of EV content in the search for HD biomarkers.

Challenges in the Development of Drug Delivery Systems Based on Small Extracellular Vesicles for Therapy of Brain Diseases

Small extracellular vesicles (sEVs) have ∼30–200 nm diameter size and may act as carriers of different cargoes, depending on the cell of origin or on the physiological/pathological condition. As endogenous nanovesicles, sEVs are important in intercellular communication and have many of the desirable features of an ideal drug delivery system. sEVs are naturally biocompatible, with superior targeting capability, safety profile, nanometric size, and can be loaded with both lipophilic and hydrophilic agents. Because of their biochemical and physical properties, sEVs are considered a promising strategy over other delivery vehicles in the central nervous system (CNS) since they freely cross the blood-brain barrier and they can be directed to specific nerve cells, potentiating a more precise targeting of their cargo. In addition, sEVs remain stable in the peripheral circulation, making them attractive nanocarrier systems to promote neuroregeneration. This review focuses on the recent progress in methods for manufacturing, isolating, and engineering sEVs that can be used as a therapeutic strategy to overcome neurodegeneration associated with pathologies of the CNS, with particular emphasis on Alzheimer’s, Parkinson’s, and amyotrophic lateral sclerosis diseases, as well as on brain tumors.

Center-Periphery Structure in Research Communities

Clustering and community detection in networks are of broad interest and have been the subject of extensive research that spans several fields. We are interested in the relatively narrow question of detecting communities of scientific publications that are linked by citations. These publication communities can be used to identify scientists with shared interests who form communities of researchers. Building on the well-known k-core algorithm, we have developed a modular pipeline to find publication communities with center-periphery structure. Using a quantitative and qualitative approach, we evaluate community finding results on a citation network consisting of over 14 million publications relevant to the field of extracellular vesicles. We compare our approach to communities discovered by the widely used Leiden algorithm for community finding.

Alzheimer's disease and depression in the elderly: A trajectory linking gut microbiota and serotonin signaling

The occurrence of neuropsychiatric symptoms in the elderly is viewed as an early sign of subsequent cognitive deterioration and conversion from mild cognitive impairment to Alzheimer's disease. The prognosis in terms of both the severity and progression of clinical dementia is generally aggravated by the comorbidity of neuropsychiatric symptoms and decline in cognitive function. Undeniably, aging and in particular unhealthy aging, is a silent "engine of neuropathology" over which multiple changes take place, including drastic alterations of the gut microbial ecosystem. This narrative review evaluates the role of gut microbiota changes as a possible unifying concept through which the comorbidity of neuropsychiatric symptoms and Alzheimer's disease can be considered. However, since the heterogeneity of neuropsychiatric symptoms, it is improbable to describe the same type of alterations in the bacteria population observed in patients with Alzheimer's disease, as well as it is improbable that the variety of drugs used to treat neuropsychiatric symptoms might produce changes in gut bacterial diversity similar to that observed in the pathophysiology of Alzheimer's disease. Depression seems to be another very intriguing exception, as it is one of the most frequent neuropsychiatric symptoms in dementia and a mood disorder frequently associated with brain aging. Antidepressants (i.e., serotonin reuptake inhibitors) or tryptophan dietary supplementation have been shown to reduce Amyloid β-loading, reinstate microbial diversity and reduce the abundance of bacterial taxa dominant in depression and Alzheimer's disease. This review briefly examines this trajectory by discussing the dysfunction of gut microbiota composition, selected bacterial taxa, and alteration of tryptophan and serotonin metabolism/neurotransmission as overlapping in-common mechanisms involved with depression, Alzheimer's disease, and unhealthy aging.

Nanocarriers Call the Last Shot in the Treatment of Brain Cancers

Our brain is protected by physio-biological barriers. The blood–brain barrier (BBB) main mechanism of protection relates to the abundance of tight junctions (TJs) and efflux pumps. Although BBB is crucial for healthy brain protection against toxins, it also leads to failure in a devastating disease like brain cancer. Recently, nanocarriers have been shown to pass through the BBB and improve patients’ survival rates, thus becoming promising treatment strategies. Among nanocarriers, inorganic nanocarriers, solid lipid nanoparticles, liposomes, polymers, micelles, and dendrimers have reached clinical trials after delivering promising results in preclinical investigations. The size of these nanocarriers is between 10 and 1000 nm and is modified by surface attachment of proteins, peptides, antibodies, or surfactants. Multiple research groups have reported transcellular entrance as the main mechanism allowing for these nanocarriers to cross BBB. Transport proteins and transcellular lipophilic pathways exist in BBB for small and lipophilic molecules. Nanocarriers cannot enter via the paracellular route, which is limited to water-soluble agents due to the TJs and their small pore size. There are currently several nanocarriers in clinical trials for the treatment of brain cancer. This article reviews challenges as well as fitting attributes of nanocarriers for brain tumor treatment in preclinical and clinical studies.