Exosomes and their role in the intercellular trafficking of normal and disease associated prion proteins

Exosomes in Vascular/Neurological Disorders and the Road Ahead

Neurodegenerative diseases, such as Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), Huntington's disease (HD), stroke, and aneurysms, are characterized by the abnormal accumulation and aggregation of disease-causing proteins in the brain and spinal cord. Recent research suggests that proteins linked to these conditions can be secreted and transferred among cells using exosomes. The transmission of abnormal protein buildup and the gradual degeneration in the brains of impacted individuals might be supported by these exosomes. Furthermore, it has been reported that neuroprotective functions can also be attributed to exosomes in neurodegenerative diseases. The potential neuroprotective functions may play a role in preventing the formation of aggregates and abnormal accumulation of proteins associated with the disease. The present review summarizes the roles of exosomes in neurodegenerative diseases as well as elucidating their therapeutic potential in AD, PD, ALS, HD, stroke, and aneurysms. By elucidating these two aspects of exosomes, valuable insights into potential therapeutic targets for treating neurodegenerative diseases may be provided.

Beyond the Pump: A Narrative Study Exploring Heart Memory

The field of organ transplantation, particularly heart transplantation, has brought to light interesting phenomena challenging traditional understandings of memory, identity, and consciousness. Studies indicate that heart transplant recipients may exhibit preferences, emotions, and memories resembling those of the donors, suggesting a form of memory storage within the transplanted organ. Mechanisms proposed for this memory transfer include cellular memory, epigenetic modifications, and energetic interactions. Moreover, the heart's intricate neural network, often referred to as the "heart brain," communicates bidirectionally with the brain and other organs, supporting the concept of heart-brain connection and its role in memory and personality. Additionally, observations from hemispherectomy procedures highlight the brain's remarkable plasticity and functional preservation beyond expectations, further underscoring the complex interplay between the brain, body, and identity. However, ethical and philosophical questions regarding the implications of these findings, including the definition of death and the nature of personal identity, remain unresolved. Further interdisciplinary research is needed to unravel the intricacies of memory transfer, neuroplasticity, and organ integration, offering insights into both organ transplantation and broader aspects of neuroscience and human identity. Understanding these complexities holds promise for enhancing patient care in organ transplantation and deepens our understanding of fundamental aspects of human experience and existence.

Challenges and future scope of exosomes in the treatment of cardiovascular diseases

Exosomes are nanosized vesicles that carry biologically diverse molecules for intercellular communication. Researchers have been trying to engineer exosomes for therapeutic purposes by using different approaches to deliver biologically active molecules to the various target cells efficiently. Recent technological advances may allow the biodistribution and pharmacokinetics of exosomes to be modified to meet scientific needs with respect to specific diseases. However, it is essential to determine an exosome's optimal dosage and potential side effects before its clinical use. Significant breakthroughs have been made in recent decades concerning exosome labelling and imaging techniques. These tools provide in situ monitoring of exosome biodistribution and pharmacokinetics and pinpoint targetability. However, because exosomes are nanometres in size and vary significantly in contents, a deeper understanding is required to ensure accurate monitoring before they can be applied in clinical settings. Different research groups have established different approaches to elucidate the roles of exosomes and visualize their spatial properties. This review covers current and emerging strategies for in vivo and in vitro exosome imaging and tracking for potential studies.

The human neurosecretome: extracellular vesicles and particles (EVPs) of the brain for intercellular communication, therapy, and liquid-biopsy applications

Emerging evidence suggests that brain derived extracellular vesicles (EVs) and particles (EPs) can cross blood-brain barrier and mediate communication among neurons, astrocytes, microglial, and other cells of the central nervous system (CNS). Yet, a complete understanding of the molecular landscape and function of circulating EVs & EPs (EVPs) remain a major gap in knowledge. This is mainly due to the lack of technologies to isolate and separate all EVPs of heterogeneous dimensions and low buoyant density. In this review, we aim to provide a comprehensive understanding of the neurosecretome, including the extracellular vesicles that carry the molecular signature of the brain in both its microenvironment and the systemic circulation. We discuss the biogenesis of EVPs, their function, cell-to-cell communication, past and emerging isolation technologies, therapeutics, and liquid-biopsy applications. It is important to highlight that the landscape of EVPs is in a constant state of evolution; hence, we not only discuss the past literature and current landscape of the EVPs, but we also speculate as to how novel EVPs may contribute to the etiology of addiction, depression, psychiatric, neurodegenerative diseases, and aid in the real time monitoring of the "living brain". Overall, the neurosecretome is a concept we introduce here to embody the compendium of circulating particles of the brain for their function and disease pathogenesis. Finally, for the purpose of inclusion of all extracellular particles, we have used the term EVPs as defined by the International Society of Extracellular Vesicles (ISEV).

Exosomes, microvesicles, and other extracellular vesicles-a Keystone Symposia report

Extracellular vesicles (EVs) are small, lipid-bilayer-bound particles released by cells that can contain important bioactive molecules, including lipids, RNAs, and proteins. Once released in the extracellular environment, EVs can act as messengers locally as well as to distant tissues to coordinate tissue homeostasis and systemic responses. There is a growing interest in not only understanding the physiology of EVs as signaling particles but also leveraging them as minimally invasive diagnostic and prognostic biomarkers (e.g., they can be found in biofluids) and drug-delivery vehicles. On October 30-November 2, 2022, researchers in the EV field convened for the Keystone symposium "Exosomes, Microvesicles, and Other Extracellular Vesicles" to discuss developing standardized language and methodology, new data on the basic biology of EVs and potential clinical utility, as well as novel technologies to isolate and characterize EVs.

Human prion diseases and the prion protein - what is the current state of knowledge?

Prion diseases and the prion protein are only partially understood so far in many aspects. This explains the continued research on this topic, calling for an overview on the current state of knowledge. The main objective of the present review article is to provide a comprehensive up-to-date presentation of all major features of human prion diseases bridging the gap between basic research and clinical aspects. Starting with the prion protein, current insights concerning its physiological functions and the process of pathological conversion will be highlighted. Diagnostic, molecular, and clinical aspects of all human prion diseases will be discussed, including information concerning rare diseases like prion-associated amyloidoses and Huntington disease-like 1, as well as the question about a potential human threat due to the transmission of prions from prion diseases of other species such as chronic wasting disease. Finally, recent attempts to develop future therapeutic strategies will be addressed.

CARDIOPULMONARY BYPASS-DERIVED PLASMA EXOSOMAL HMGB1 CONTRIBUTES TO ALVEOLAR EPITHELIAL CELL NECROPTOSIS VIA mtDNA/CGAS/STING PATHWAY

ABSTRACT

Our previous study confirmed that cardiopulmonary bypass (CPB) leads to acute lung injury (ALI) via inducing high-mobility group box 1 (HMGB1) release. Recent research showed that HMGB1 promotes pulmonary injury mainly via exosomes transport. Currently, alveolar epithelial cell (AEC) necroptosis has been demonstrated to be involved in ALI. However, it is unknown whether exosomal inflammatory cytokine HMGB1 promotes ALI by inducing AEC necroptosis, and its underlying mechanisms remain elusive. Here, a prospective cohort study was carried out, in which plasma samples from 21 CPB patients were isolated at four specific time points: pre-CPB, 2, 12, and 24 h after initiation of CPB. Plasma exosomes were extracted via ultra-high-speed centrifugation and cocultured with AEC cell line-A549 cells at increasing concentrations of 50, 100, and 150 μg/mL. Then, HMGB1 antagonist-Box A and mtDNA deficiency ethidium bromide (EtBr) were applied to explore the underlying role of exosomal HMGB1 and cytoplasm mitochondrial DNA in AEC. Western blot analysis showed that plasma exosomal HMGB1 expression gradually increased and peaked at 24 h after CPB. Twenty-four-hour treatment of CPB-derived exosomes at 150 μg/mL for 24 h could induce necroptosis by promoting mitochondrial fission and further elevating cytoplasm mtDNA levels in A549 cells, which was successfully blocked by Box A or EtBr. Most importantly, EtBr significantly inhibited cytoplasm mtDNA downstream guanosine monophosphate (GMP)-AMP synthase (cGAS)/stimulator of interferon gene (STING) signal pathway. Collectively, these data demonstrate that CPB-derived plasma exosomal HMGB1 contributes to AEC necroptosis through the mtDNA/cGAS/STING pathway.

Exosomes─Nature's Lipid Nanoparticles, a Rising Star in Drug Delivery and Diagnostics

Exosomes are a subgroup of nanosized extracellular vesicles enclosed by a lipid bilayer membrane and secreted by most eukaryotic cells. They represent a route of intercellular communication and participate in a wide variety of physiological and pathological processes. The biological roles of exosomes rely on their bioactive cargos, including proteins, nucleic acids, and lipids, which are delivered to target cells. Their distinctive properties─innate stability, low immunogenicity, biocompatibility, and good biomembrane penetration capacity─allow them to function as superior natural nanocarriers for efficient drug delivery. Another notably favorable clinical application of exosomes is in diagnostics. They hold various biomolecules from host cells, which are indicative of pathophysiological conditions; therefore, they are considered vital for biomarker discovery in clinical diagnostics. Here, we use data from the CAS Content Collection and provide a landscape overview of the current state and delineate trends in research advancement on exosome applications in therapeutics and diagnostics across time, geography, composition, cargo loading, and development pipelines. We discuss exosome composition and pathway, from their biogenesis and secretion from host cells to recipient cell uptake. We assess methods for exosome isolation and purification, their clinical applications in therapy and diagnostics, their development pipelines, the exploration goals of the companies, the assortment of diseases they aim to treat, development stages of their research, and publication trends. We hope this review will be useful for understanding the current knowledge in the field of medical applications of exosomes, in an effort to further solve the remaining challenges in fulfilling their potential.

Extracellular microRNA and cognitive function in a prospective cohort of older men: The Veterans Affairs Normative Aging Study

BACKGROUND

Aging-related cognitive decline is an early symptom of Alzheimer's disease and other dementias, and on its own can have substantial consequences on an individual's ability to perform important everyday functions. Despite increasing interest in the potential roles of extracellular microRNAs (miRNAs) in central nervous system (CNS) pathologies, there has been little research on extracellular miRNAs in early stages of cognitive decline. We leverage the longitudinal Normative Aging Study (NAS) cohort to investigate associations between plasma miRNAs and cognitive function among cognitively normal men.

METHODS

This study includes data from up to 530 NAS participants (median age: 71.0 years) collected from 1996 to 2013, with a total of 1,331 person-visits (equal to 2,471 years of follow up). Global cognitive function was assessed using the Mini-Mental State Examination (MMSE). Plasma miRNAs were profiled using small RNA sequencing. Associations of expression of 381 miRNAs with current cognitive function and rate of change in cognitive function were assessed using linear regression (N = 457) and linear mixed models (N = 530), respectively.

RESULTS

In adjusted models, levels of 2 plasma miRNAs were associated with higher MMSE scores (p < 0.05). Expression of 33 plasma miRNAs was associated with rate of change in MMSE scores over time (p < 0.05). Enriched KEGG pathways for miRNAs associated with concurrent MMSE and MMSE trajectory included Hippo signaling and extracellular matrix-receptor interactions. Gene targets of miRNAs associated with MMSE trajectory were additionally associated with prion diseases and fatty acid biosynthesis.

CONCLUSIONS

Circulating miRNAs were associated with both cross-sectional cognitive function and rate of change in cognitive function among cognitively normal men. Further research is needed to elucidate the potential functions of these miRNAs in the CNS and investigate relationships with other neurological outcomes.

A new paradigm for diagnosis of neurodegenerative diseases: peripheral exosomes of brain origin

Neurodegenerative diseases are a heterogeneous group of maladies, characterized by progressive loss of neurons. These diseases involve an intricate pattern of cross-talk between different types of cells to maintain specific signaling pathways. A component of such intercellular cross-talk is the exchange of various types of extracellular vesicles (EVs). Exosomes are a subset of EVs, which are increasingly being known for the role they play in the pathogenesis and progression of neurodegenerative diseases, e.g., synucleinopathies and tauopathies. The ability of the central nervous system exosomes to cross the blood–brain barrier into blood has generated enthusiasm in their study as potential biomarkers. However, the lack of standardized, efficient, and ultra-sensitive methods for the isolation and detection of brain-derived exosomes has hampered the development of effective biomarkers. Exosomes mirror heterogeneous biological changes that occur during the progression of these incurable illnesses, potentially offering a more comprehensive outlook of neurodegenerative disease diagnosis, progression and treatment. In this review, we aim to discuss the challenges and opportunities of peripheral biofluid-based brain-exosomes in the diagnosis and biomarker discovery of Alzheimer’s and Parkinson’s diseases. In the later part, we discuss the traditional and emerging methods used for the isolation of exosomes and compare their advantages and disadvantages in clinical settings.

Cellular prion protein in human plasma-derived extracellular vesicles promotes neurite outgrowth via the NMDA receptor-LRP1 receptor system

Exosomes and other extracellular vesicles (EVs) participate in cell–cell communication. Herein, we isolated EVs from human plasma and demonstrated that these EVs activate cell signaling and promote neurite outgrowth in PC-12 cells. Analysis of human plasma EVs purified by sequential ultracentrifugation using tandem mass spectrometry indicated the presence of multiple plasma proteins, including α₂-macroglobulin, which is reported to regulate PC-12 cell physiology. We therefore further purified EVs by molecular exclusion or phosphatidylserine affinity chromatography, which reduced plasma protein contamination. EVs subjected to these additional purification methods exhibited unchanged activity in PC-12 cells, even though α₂-macroglobulin was reduced to undetectable levels. Nonpathogenic cellular prion protein (PrP^C) was carried by human plasma EVs and essential for the effects of EVs on PC-12 cells, as EV-induced cell signaling and neurite outgrowth were blocked by the PrP^C-specific antibody, POM2. In addition, inhibitors of the N-methyl-d-aspartate (NMDA) receptor (NMDA-R) and low-density lipoprotein receptor–related protein-1 (LRP1) blocked the effects of plasma EVs on PC-12 cells, as did silencing of Lrp1 or the gene encoding the GluN1 NMDA-R subunit (Grin1). These results implicate the NMDA-R–LRP1 complex as the receptor system responsible for mediating the effects of EV-associated PrP^C. Finally, EVs harvested from rat astrocytes carried PrP^C and replicated the effects of human plasma EVs on PC-12 cell signaling. We conclude that interaction of EV-associated PrP^C with the NMDA-R–LRP1 complex in target cells represents a novel mechanism by which EVs may participate in intercellular communication in the nervous system.

Role of Exosomes in Brain Diseases

Exosomes are a subset of extracellular vesicles that act as messengers to facilitate communication between cells. Non-coding RNAs, proteins, lipids, and microRNAs are delivered by the exosomes to target molecules (such as proteins, mRNAs, or DNA) of host cells, thereby playing a key role in the maintenance of normal brain function. However, exosomes are also involved in the occurrence, prognosis, and clinical treatment of brain diseases, such as Alzheimer's disease, Parkinson's disease, stroke, and traumatic brain injury. In this review, we have summarized novel findings that elucidate the role of exosomes in the occurrence, prognosis, and treatment of brain diseases.

Exosomal Proteins and miRNAs as Mediators of Amyotrophic Lateral Sclerosis

Recent advances in the neurobiology and neurogenerative diseases have attracted growing interest in exosomes and their ability to carry and propagate active biomolecules as a means to reprogram recipient cells. Alterations in exosomal protein content and nucleic acid profiles found in human biological fluids have been correlated with various diseases including amyotrophic lateral sclerosis (ALS). In ALS pathogenesis, these lipid-bound nanoscale vesicles have emerged as valuable candidates for diagnostic biomarkers. Moreover, their capacity to spread misfolded proteins and functional non-coding RNAs to interconnected neuronal cells make them putative mediators for the progressive motor degeneration found remarkably apparent in ALS. This review outlines current knowledge concerning the biogenesis, heterogeneity, and function of exosomes in the brain as well as a comprehensive probe of currently available literature on ALS-related exosomal proteins and microRNAs. Lastly, with the rapid development of employing nanoparticles for drug delivery, we explore the therapeutic potentials of exosomes as well as underlying limitations in current isolation and detection methodologies.

Bovine extracellular vesicles contaminate human extracellular vesicles produced in cell culture conditioned medium when 'exosome-depleted serum' is utilised

Extracellular vesicles (EVs) are important intercellular communication messengers. Half of the published studies in the field are in vitro cell culture based in which bovine serum in various concentrations and forms is used to facilitate the production of extracellular vesicles. 'Exosome depleted serum' is the type of bovine serum most widely used in the production of human EVs. Herein, we demonstrate that, despite the initial caution raised in 2014 about the persistence of bovine EVs, 'exosome depleted serum' was still used in 46% of publications on human or rodent EVs between 2015 and 2019. Using nanoparticle tracking analysis combined with detergent lysis of vesicles as well as bovine CD9 ELISA, we show that there were approximately 5.33 x 107/mL of bovine EVs remaining in the 'exosome depleted serum'. Importantly, the 'exosome depleted serum' was relatively enriched in small EVs by approximately 2.7-fold relative to the large EVs compared to that in the original serum. Specifically, the percentage of small EVs in total vesicles had increased from the original 48% in the serum before ultracentrifugation to 92% in the 'exosome depleted serum'. Furthermore, the pervasive bovine EVs carried over by the 'exosome depleted serum', even when the lowest concentration (0.5%) was used in cell culture, resulted in a significant contamination of human EVs in cell culture conditioned medium. Our findings indicate that the use 'exosome depleted serum' in cell culture-based studies may introduce artefacts into research examining the function of human and rodent EVs, in particular those involving EV miRNA. Thus, we appeal to the researchers in the EV field to seriously reconsider the practice of using 'exosome depleted serum' in the production of human and other mammalian EVs in vitro.

Accurate and Nonpurified Identification of Extracellular Vesicles Using Dual-Binding Recognition Mode

Circulating extracellular vesicles (EVs) are promising biomarkers for the early diagnosis and prognosis of cancer in a non-invasive manner. However, the rapid and accurate identification of EVs in complex biological samples is technically challenging, which is attributed to the requirement of extensive sample purification and unsatisfactory detection accuracy due to the disturbance of interfering proteins. Herein, a simultaneous binding of double-positive EV membrane protein-based recognition mode (DRM) is proposed. By the combination of DRM-mediated toehold activation and G-quadruplex DNAZyme-catalyzed etching of Au@Ag nanorods (Au@Ag NRs), we have developed an accurate, non-purified, low-cost, and visual strategy for EV identification. The synchronous binding of double-positive proteins on EV membranes is validated by confocal laser scanning microscopy analysis. This approach exhibits excellent specificity and sensitivity toward EVs ranging from 1.0 × 10⁵ to 1.0 × 10⁹ particles/mL with a detection limit of 6.31 × 10⁴ particles/mL. Moreover, we have successfully realized non-purified EV quantification in complex biological media. In addition, target-initiated catalyzed hairpin assembly (CHA) is integrated with G-quadruplex DNAZyme-catalyzed color variation of Au@Ag NRs; thus, low-background EV detection can be achieved by the naked eye. Furthermore, our strategy is easy to adapt to high-throughput formats by using an automatic microplate reader, which could be expected to meet the requirements for high-throughput detection of clinical samples. With its capacities of rapidness, portability, affordability, high throughput, non-purification, and visual detection, this strategy could provide a practical tool for accurate identification of EVs and early diagnosis of cancer.

Tissue-derived extracellular vesicles: Research progress from isolation to application

Extracellular vesicles (EVs) are the structures that all cells release into the environment. They are separated by a lipid bilayer and contain the cellular components that release them. To date, most studies have been performed on EVs derived from cell supernatants or different body fluids, while the number of studies on EV isolation directly from tissues is still limited. Studies of EV isolation directly from tissues may provide us with better information. This review summarizes the role of EV in the extracellular matrix, the protocol for isolation of EV in the tissue interstitium, and the application of the protocol in different tissues.

Extracellular Vesicles-The Next Frontier in Endocrinology

Extracellular vesicles (EVs), including exosomes, are emerging as important carriers of signals in normal and pathological physiology. As EVs are a long-range communication or signaling modality-just like hormones are-the field of endocrinology is uniquely poised to offer insight into their functional biology and regulation. EVs are membrane-bound particles secreted by many different cell types and can have local or systemic effects, being transported in body fluids. They express transmembrane proteins, some of which are shared between EVs and some being specific to the tissue of origin, that can interact with target cells directly (much like hormones can). They also contain cargo within them that includes DNA, RNA, miRNA, and various metabolites. They can fuse with target cells to empty their cargo and alter their target cell physiology in this way also. Similar to the endocrine system, the EV system is likely to be under homeostatic control, making the regulation of their biogenesis and secretion important aspects to study. In this review, we briefly highlight select examples of how EVs are implicated in normal physiology and disease states. We also discuss what is known about their biogenesis and regulation of secretion. We hope that this paper inspires the endocrinology field to use our collective expertise to explore these new multimodal "hormones."

Exosomal delivery of therapeutic modulators through the blood-brain barrier; promise and pitfalls

Nowadays, a large population around the world, especially the elderly, suffers from neurological inflammatory and degenerative disorders/diseases. Current drug delivery strategies are facing different challenges because of the presence of the BBB, which limits the transport of various substances and cells to brain parenchyma. Additionally, the low rate of successful cell transplantation to the brain injury sites leads to efforts to find alternative therapies. Stem cell byproducts such as exosomes are touted as natural nano-drug carriers with 50-100 nm in diameter. These nano-sized particles could harbor and transfer a plethora of therapeutic agents and biological cargos to the brain. These nanoparticles would offer a solution to maintain paracrine cell-to-cell communications under healthy and inflammatory conditions. The main question is that the existence of the intact BBB could limit exosomal trafficking. Does BBB possess some molecular mechanisms that facilitate the exosomal delivery compared to the circulating cell? Although preliminary studies have shown that exosomes could cross the BBB, the exact molecular mechanism(s) beyond this phenomenon remains unclear. In this review, we tried to compile some facts about exosome delivery through the BBB and propose some mechanisms that regulate exosomal cross in pathological and physiological conditions.

Function of exosomes in neurological disorders and brain tumors

Exosomes are a subtype of extracellular vesicles released from different cell types including those in the nervous system, and are enriched in a variety of bioactive molecules such as RNAs, proteins and lipids. Numerous studies have indicated that exosomes play a critical role in many physiological and pathological activities by facilitating intercellular communication and modulating cells' responses to external environments. Particularly in the central nervous system, exosomes have been implicated to play a role in many neurological disorders such as abnormal neuronal development, neurodegenerative diseases, epilepsy, mental disorders, stroke, brain injury and brain cancer. Since exosomes recapitulate the characteristics of the parental cells and have the capacity to cross the blood-brain barrier, their cargo can serve as potential biomarkers for early diagnosis and clinical assessment of disease treatment. In this review, we describe the latest findings and current knowledge of the roles exosomes play in various neurological disorders and brain cancer, as well as their application as promising biomarkers. The potential use of exosomes to deliver therapeutic molecules to treat diseases of the central nervous system is also discussed.

Exosomes in Parkinson disease

Parkinson disease (PD) is a prevalent neurodegenerative disease, in which the formation of misfolded and aggregated α-synuclein is a key neuropathological hallmark. Recent studies reveal that extracellular vesicles such as exosomes present a potential mechanism for propagation of pathological α-synuclein throughout the brain. The ability of exosomes to transport proteins and genetic material between cells, including mRNA and microRNAs which have been implicated in PD pathology, provides critical insights as to how exosomes may contribute to pathological progression in PD. Advances have also been made in the investigation of exosomes as potential tools for the modulation of Parkinson's pathology; their detection extracellularly may facilitate their use as biomarkers, while their small size could be utilised as vectors for the delivery of therapeutics. The aim of this review was to highlight our current knowledge of the role of exosomes in PD and potential clinical application.

Expression and function of Ndel1 during the differentiation of neural stem cells induced by hippocampal exosomesticle

BACKGROUND

In the brain of adult mammals, neural stem cells persist in the subventricular zone of the lateral ventricle and the subgranular zone of the dentate gyrus, which are specialized niches with proliferative capacity. Most neural stem cells are in a quiescent state, but in response to extrinsic stimuli, they can exit from quiescence and become reactivated to produce new neurons, so neural stem cells are considered to be a potential source for cell replacement therapy of many nervous system diseases. We characterized the expression of Ndel1 during the differentiation of neural stem cells induced by hippocampus exosomes, and assessed the effect of Ndel1 on neural stem cells differentiation.

METHODS

Hippocampal exosomes were isolated and extracted, and co-cultured exosomes with neural stem cells. Western blot, flow cytometry, and immunofluorescence analyses were used to analyze expression of neuronal markers. Further, utilizing high-throughput RNA sequencing technology, we found that nudE neurodevelopment protein 1-like 1 was significantly upregulated in exosomes derived from denervated hippocampus, and then characterized its mechanism and function during neural stem cells differentiation by qRT-PCR, western blot, flow cytometry, and immunofluorescence analyses.

RESULTS

Our results revealed that exosomes of denervated hippocampus promoted the differentiation of neural stem cells into neuron. Hence, we identified that nudE neurodevelopment protein 1-like 1 was significantly upregulated and highly expressed in the nervous system. In addition, we found that miR-107-3p may regulate neural stem cell differentiation by targeting Ndel1.

CONCLUSIONS

Our results revealed that deafferentation of the hippocampal exosomes co-cultured with neural stem cells could promote them to differentiate into neurons. Hence, we found that miR-107-3p may regulate neural stem cells differentiation by targeting Ndel1. Importantly, Ndel1 enhanced spatial learning and hippocampal neurogenesis in rats after fimbria fornix transection in vivo. These findings set the stage for a better understanding of neurogenesis, a process that 1 day may inspire new treatments for central nervous system diseases.

Targeted delivery of extracellular vesicles in heart injury

Extracellular vesicles (EVs) are nanoscale extracellular vesicles derived from endocytosis that are crucial to intercellular communication. EVs possess natural biocompatibility and stability that allow them to cross biological membranes and that protect them from degradation. Recent studies have shown that EVs-mediated crosstalk between different cell types in the heart could play important roles in the maintenance of cardiac homeostasis and the pathogenesis of heart diseases. In particular, EVs secreted by different types of stem cells exhibit cardioprotective effects. However, numerous studies have shown that intravenously injected EVs are quickly cleared by macrophages of the mononuclear phagocyte system (MPS) and preferentially accumulate in MPS organs such as the liver, spleen, and lung. In this review, we discuss exosome biogenesis, the role of EVs in heart diseases, and challenges in delivering EVs to the heart. Furthermore, we extensively discuss the targeted delivery of EVs for treating ischemic heart disease. These understandings will aid in the development of effective treatment strategies for heart diseases.

A New Take on Prion Protein Dynamics in Cellular Trafficking

The mobility of cellular prion protein (PrP^C) in specific cell membrane domains and among distinct cell compartments dictates its molecular interactions and directs its cell function. PrP^C works in concert with several partners to organize signaling platforms implicated in various cellular processes. The scaffold property of PrP^C is able to gather a molecular repertoire to create heterogeneous membrane domains that favor endocytic events. Dynamic trafficking of PrP^C through multiple pathways, in a well-orchestrated mechanism of intra and extracellular vesicular transport, defines its functional plasticity, and also assists the conversion and spreading of its infectious isoform associated with neurodegenerative diseases. In this review, we highlight how PrP^C traffics across intra- and extracellular compartments and the consequences of this dynamic transport in governing cell functions and contributing to prion disease pathogenesis.

Mesenchymal stem cell-derived extracellular vesicle-based therapies protect against coupled degeneration of the central nervous and vascular systems in stroke

Stem cell-based treatments have been suggested as promising candidates for stroke. Recently, mesenchymal stem cells (MSCs) have been reported as potential therapeutics for a wide range of diseases. In particular, clinical trial studies have suggested MSCs for stroke therapy. The focus of MSC treatments has been directed towards cell replacement. However, recent research has lately highlighted their paracrine actions. The secretion of extracellular vesicles (EVs) is offered to be the main therapeutic mechanism of MSC therapy. However, EV-based treatments may provide a wider therapeutic window compared to tissue plasminogen activator (tPA), the traditional treatment for stroke. Exosomes are nano-sized EVs secreted by most cell types, and can be isolated from conditioned cell media or body fluids such as plasma, urine, and cerebrospinal fluid (CSF). Exosomes apply their effects through targeting their cargos such as microRNAs (miRs), DNAs, messenger RNAs, and proteins at the host cells, which leads to a shift in the behavior of the recipient cells. It has been indicated that exosomes, in particular their functional cargoes, play a significant role in the coupled pathogenesis and recovery of stroke through affecting the neurovascular unit (NVU). Therefore, it seems that exosomes could be utilized as diagnostic and therapeutic tools in stroke treatment. The miRs are small endogenous non-coding RNA molecules which serve as the main functional cargo of exosomes, and apply their effects as epigenetic regulators. These versatile non-coding RNA molecules are involved in various stages of stroke and affect stroke-related factors. Moreover, the involvement of aging-induced changes to specific miRs profile in stroke further highlights the role of miRs. Thus, miRs could be utilized as diagnostic, prognostic, and therapeutic tools in stroke. In this review, we discuss the roles of stem cells, exosomes, and their application in stroke therapy. We also highlight the usage of miRs as a therapeutic choice in stroke therapy.

Alix and Syntenin-1 direct amyloid precursor protein trafficking into extracellular vesicles

BACKGROUND

Endosomal trafficking and amyloidogenic cleavage of amyloid precursor protein (APP) is believed to play a role in the neurodegeneration observed in Alzheimer's disease (AD). Recent evidence has suggested that packaging and secretion of APP and its amyloidogenic cleaved products into small extracellular vesicles (EVs) may facilitate uptake of these neurotoxic factors during disease progression. However, the molecular mechanisms underlying trafficking of APP into EVs are poorly understood.

RESULTS

In this study, the mechanism and impact of APP trafficking into extracellular vesicles (EVs) were assessed by a series of inducible gene knockdowns. We demonstrate that vesicle-associated proteins Alix and Syntenin-1 are essential for proper subcellular localization and efficient EV secretion of APP via an endosomal sorting complexes required for transport (ESCRT)-independent pathway. The neurotoxic C-terminal fragment (CTFβ) of APP is similarly secreted in association with small vesicles. These mechanisms are conserved in terminally differentiated neuron-like cells. Furthermore, knockdown of Alix and Syntenin-1 alters the subcellular localization of APP, sequestering the precursor protein to endoplasmic reticulum and endolysosomal compartments, respectively. Finally, transfer of small EVs containing mutant APP confers an increase in reactive oxygen species production and neurotoxicity to human induced pluripotent stem cell-derived cortical neurons and naïve primary neurons, an effect that is ameliorated by Alix and Syntenin-1 depletion.

CONCLUSIONS

Altogether these findings elucidate a novel mechanism for understanding the intracellular trafficking of APP and CTFβ into secreted extracellular vesicles, and the resultant potential impact on neurotoxicity in the context of Alzheimer's disease amyloidopathy.

Advances in Exosomes Derived from Different Cell Sources and Cardiovascular Diseases

Exosomes can reach distant tissues through blood circulation to communicate directly with target cells and rapidly regulate intracellular signals. Exosomes play an important role in cardiovascular pathophysiology. Different exosomes derived from different sources, and their cargos have different mechanisms of action. In addition to being biomarkers, exosomes also have a certain significance in the diagnosis, treatment, and even prevention of cardiovascular diseases. Here, we provide a review of the up-to-date applications of exosomes, derived from various sources, in the prognosis and diagnosis of cardiovascular diseases.

Exosomes

Exosomes are small, single-membrane, secreted organelles of ∼30 to ∼200 nm in diameter that have the same topology as the cell and are enriched in selected proteins, lipids, nucleic acids, and glycoconjugates. Exosomes contain an array of membrane-associated, high-order oligomeric protein complexes, display pronounced molecular heterogeneity, and are created by budding at both plasma and endosome membranes. Exosome biogenesis is a mechanism of protein quality control, and once released, exosomes have activities as diverse as remodeling the extracellular matrix and transmitting signals and molecules to other cells. This pathway of intercellular vesicle traffic plays important roles in many aspects of human health and disease, including development, immunity, tissue homeostasis, cancer, and neurodegenerative diseases. In addition, viruses co-opt exosome biogenesis pathways both for assembling infectious particles and for establishing host permissiveness. On the basis of these and other properties, exosomes are being developed as therapeutic agents in multiple disease models.

Neurotoxic and Neuroprotective Role of Exosomes in Parkinson’s Disease

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Exosomes are extracellular vesicles produced by eukaryotic cells that are also found in most biological fluids and tissues. While they were initially thought to act as compartments for removal of cellular debris, they are now recognized as important tools for cell-to-cell communication and for the transfer of pathogens between the cells. They have attracted particular interest in neurodegenerative diseases for their potential role in transferring prion-like proteins between neurons, and in Parkinson’s disease (PD), they have been shown to spread oligomers of α-synuclein in the brain accelerating the progression of this pathology. A potential neuroprotective role of exosomes has also been equally proposed in PD as they could limit the toxicity of α-synuclein by clearing them out of the cells. Exosomes have also attracted considerable attention for use as drug vehicles. Being nonimmunogenic in nature, they provide an unprecedented opportunity to enhance the delivery of incorporated drugs to target cells. In this review, we discuss current knowledge about the potential neurotoxic and neuroprotective role of exosomes and their potential application as drug delivery systems in PD.

Bone marrow mesenchymal stem cell-derived exosome uptake and retrograde transport can occur at peripheral nerve endings

We investigated the occurrence of mesenchymal stem cell (MSC)-derived exosome uptake and retrograde transport at peripheral nerve endings using bone marrow MSCs (bMSCs) transduced with recombinant CD63-green fluorescent protein (GFP) lentiviral plasmid. GFP was used to track the release of bMSC-derived exosomes and the uptake and transport at peripheral nerve terminals, the dorsal root ganglion (DRG), and the spinal cord. In vitro cell culture and injection of a CD63-GFP exosome suspension into the right gastrocnemius muscle of an in vivo rat model were also performed. Fluorescence microscopy of co-cultured CD63-GFP exosomes and SH-SY5Y or BV2 cell lines and primary cultured DRG cells in a separate experiment demonstrated exosome uptake into DRG neurons and glia. Moreover, we observed both retrograde axoplasmic transport and hematogenous transport of exosomes injected into rat models at the DRG and the ipsilateral side of the anterior horn of the spinal cord using fluorescence microscopy, immunohistochemistry, and Western blot analyses. In conclusion, we showed that exosome uptake at peripheral nerve endings and retrograde transport of exosomes to DRG neurons and spinal cord motor neurons in the anterior horn can occur. In addition, our findings propose a novel drug delivery approach for treating neuronal diseases.

Initiation and Transmission of α-Synuclein Pathology in Parkinson's Disease

The pathogenesis of Parkinson's disease (PD) involves the accumulation of aggregated forms of α-synuclein in the body. The location for the initiation of misfolded forms of α-synuclein is now a contentious issue, what was once thought to be a disease of the central nervous system (CNS) now appears to involve multiple organs in the body. In particular, the two regions in the body where the nervous system is exposed to the environment, the olfactory bulb and the enteric nervous system, are now thought to play an important role in the initial phase of the disease. Epidemiological studies point to the gastrointestinal tract, including the appendix, as a potential site for the misfolding and transmission of α-synuclein, with the vagus nerve providing a conduit between the gut and brain. A growing body of animal studies also support this pathway, implicating the transmission of pathological α-synuclein from outside the CNS in the development of PD.

Personality changes following heart transplantation: The role of cellular memory

Personality changes following heart transplantation, which have been reported for decades, include accounts of recipients acquiring the personality characteristics of their donor. Four categories of personality changes are discussed in this article: (1) changes in preferences, (2) alterations in emotions/temperament, (3) modifications of identity, and (4) memories from the donor's life. The acquisition of donor personality characteristics by recipients following heart transplantation is hypothesized to occur via the transfer of cellular memory, and four types of cellular memory are presented: (1) epigenetic memory, (2) DNA memory, (3) RNA memory, and (4) protein memory. Other possibilities, such as the transfer of memory via intracardiac neurological memory and energetic memory, are discussed as well. Implications for the future of heart transplantation are explored including the importance of reexamining our current definition of death, studying how the transfer of memories might affect the integration of a donated heart, determining whether memories can be transferred via the transplantation of other organs, and investigating which types of information can be transferred via heart transplantation. Further research is recommended.

Role of Exosomes in Central Nervous System Diseases

There are many types of intercellular communication, and extracellular vesicles are one of the important forms of this. They are released by a variety of cell types, are heterogeneous, and can roughly be divided into microvesicles and exosomes according to their occurrence and function. Of course, exosomes do not just play a role in cell-to-cell communication. In the nervous system, exosomes can participate in intercellular communication, maintain the myelin sheath, and eliminate waste. Similarly, exosomes in the brain can play a role in central nervous system diseases, such as stroke, Alzheimer's disease (AD), Parkinson's disease (PD), prion disease, and traumatic encephalopathy (CTE), with both positive and negative effects (such as the transfer of misfolded proteins). Exosomes contain a variety of key bioactive substances and can therefore be considered as a snapshot of the intracellular environment. Studies have shown that exosomes from the central nervous system can be found in cerebrospinal fluid and peripheral body fluids, and that their contents will change with disease occurrence. Because exosomes can penetrate the blood brain barrier (BBB) and are highly stable in peripheral circulation, they can protect disease-related molecules well and therefore, using exosomes as a biomarker of central nervous system diseases is an attractive prospect as they can be used to monitor disease development and enable early diagnosis and treatment optimization. In this review, we discuss the current state of knowledge of exosomes, and introduce their pathophysiological roles in different diseases of the central nervous system as well as their roles and applications as a viable pathological biomarker.

Cardiomyocyte-Derived Exosomes: Biological Functions and Potential Therapeutic Implications

Exosomes, which are membrane-enclosed nanovesicles released by almost all cell types, have been recognized to play important roles in mediating cell-cell communication. In recent years, the physiological and pathological effects of exosomes on cardiovascular disease have been extensively studied. Exosomes can transfer proteins, mRNAs, microRNAs, and other bioactive molecules to recipient cells to influence their biological properties. In recent years, accumulating evidence has suggested that cardiomyocyte-derived exosomes play an important role in the progression of cardiovascular disease. Here, we summarize the functional roles of cardiomyocyte-derived exosomes in cardiovascular physiology and pathology.

Biophysical Characterization and Drug Delivery Potential of Exosomes from Human Wharton's Jelly-Derived Mesenchymal Stem Cells

Cell-derived exosomes (30-200 nm) as biological "nanocarriers" have attracted a great deal of interest for therapeutic applications due to their ability to internalize in in vivo biological systems (i.e., cells). Although they can be harvested from various sources including stem cells, yet an appropriate isolation and characterization protocol to obtain "pure" exosomal population is needed. For potential clinical applications, understanding the functional ability of exosomes and their purity, that is, free from microvesicles, apoptotic bodies, and protein aggregates, is a pre-requisite. To achieve high purity and yield of exosomes from human Wharton's jelly-derived mesenchymal stem cells (hWJ-MSCs) in the size range of 30-200 nm, we have performed and compared three isolation procedures: ultracentrifugation (UC), sucrose cushion (SC), and commercially available reagent (CR). The isolated exosomes were characterized using nanoparticle tracking analysis (NTA), field emission scanning electron microscopy (FESEM), and atomic force microscopy (AFM). Furthermore, to understand the therapeutic potential of the hWJ-MSC-derived exosomes (hWJ-ME) to target pancreatic tumor cells, the internalization efficacy has been evaluated on the MiaPaCa-2 cell lines using confocal microscopy and flow cytometry. The NTA results showed sucrose cushion to be an optimal method for exosome isolation with high purity (86.8%), as compared to UC (40.5%; p = 0.050) and CR (38%; p = 0.050). Optical analysis by FESEM and AFM revealed that SC-isolated exosomes presented a spherical morphology, whereas UC- and CR-isolated exosomes exhibited an uneven morphology. Furthermore, the data from confocal images and flow cytometry showed that hWJ-ME were internalized by MiaPaCa-2, demonstrating the feasibility of exosomes as a "potential nanocarrier". Thus, our study suggests that a combination of NTA (yield), AFM (dimensions), and FESEM (morphology and topography) could provide sensitive biophysical characterization of hWJ-ME. In the future, enriched exosomes could be used as a delivery vehicle to transport target-specific drugs or gene-silencing constructs to tumors.

Loss of exosomal miR-3188 in cancer-associated fibroblasts contributes to HNC progression

BACKGROUND

Head and neck cancer (HNC) is one of the most common deadly diseases worldwide. An increasing number of studies have recently focused on the malignant functions of cancer-associated fibroblasts (CAFs) in numerous cancers. However, the underlying mechanisms by which CAF-derived exosomes promote tumor progression need to be further elucidated. This study aims to determine whether the loss of specific miRNAs in CAF-derived exosomes may be involved in the malignant transformation of HNC.

METHODS

MiRNA array and real-time PCR assays were used to analyze the differential expression of miRNAs in exosomes from normal fibroblasts (NFs) and CAFs. Cell proliferation, EdU incorporation, colony formation, apoptosis, cell cycle distribution and xenograft assays were performed to examine the effects of miR-3188 on HNC in vitro and in vivo. Real-time PCR, western blotting and luciferase reporter assays were used to identify the target genes of miR-3188. Furthermore, tumor-bearing mouse models were used to prove the potential therapeutic value of miR-3188-loaded exosomes in HNC.

RESULTS

Our results showed that miR-3188 expression is reduced in exosomes and their parental CAFs from HNC tissues. In addition, miR-3188 can be transferred from fibroblasts to HNC cells by exosomes. Further exploration demonstrated that exosomal miR-3188 can influence the proliferation and apoptosis of HNC cells by directly targeting B-cell lymphoma 2 (BCL2) in vitro and in vivo. More importantly, we also found that miR-3188-loaded exosomes significantly inhibited tumor growth in vivo.

CONCLUSIONS

Our findings revealed that CAF-derived exosomes contain lower miR-3188 levels than NFs, and the loss of miR-3188 in exosomes contributes to the malignant phenotypes of HNC cells through the derepression of BCL2. Furthermore, these data suggest the potential therapeutic value of exosomal miR-3188 for inhibiting HNC growth.

Exosomes of pasteurized milk: potential pathogens of Western diseases

Milk consumption is a hallmark of western diet. According to common believes, milk consumption has beneficial effects for human health. Pasteurization of cow's milk protects thermolabile vitamins and other organic compounds including bioactive and bioavailable exosomes and extracellular vesicles in the range of 40-120 nm, which are pivotal mediators of cell communication via systemic transfer of specific micro-ribonucleic acids, mRNAs and regulatory proteins such as transforming growth factor-β. There is compelling evidence that human and bovine milk exosomes play a crucial role for adequate metabolic and immunological programming of the newborn infant at the beginning of extrauterine life. Milk exosomes assist in executing an anabolic, growth-promoting and immunological program confined to the postnatal period in all mammals. However, epidemiological and translational evidence presented in this review indicates that continuous exposure of humans to exosomes of pasteurized milk may confer a substantial risk for the development of chronic diseases of civilization including obesity, type 2 diabetes mellitus, osteoporosis, common cancers (prostate, breast, liver, B-cells) as well as Parkinson's disease. Exosomes of pasteurized milk may represent new pathogens that should not reach the human food chain.

An optimized method for enrichment of whole brain-derived extracellular vesicles reveals insight into neurodegenerative processes in a mouse model of Alzheimer's disease

BACKGROUND

Alzheimer's disease (AD) is the major cause of dementia that has increased dramatically in prevalence over the past several decades. Yet many questions still surround the etiology of AD. Recently, extracellular vesicles (EVs) that transport protein, lipid, and nucleic acids from cell to cell have been implicated in the clearance and propagation of misfolded proteins. Investigation of EVs in AD progression, and their potential diagnostic utility may contribute to understanding and treating AD. However, the challenges of isolating brain-derived EVs have in part hindered these studies.

NEW METHOD

Here, we provide an optimized method for the enrichment of brain-derived EVs by iodixanol floatation density gradient for mass spectrometry analysis.

RESULTS

We demonstrate the isolation of these vesicles and the enrichment of EV proteins compared to sedimentation gradient isolation of vesicles. Moreover, comparative proteomic analysis of brain-derived EVs from healthy and AD mouse brains revealed differences in vesicular content including proteins involved in aging, immune response, and oxidation-reduction maintenance. These changes provide insight into AD-associated neurodegeneration and potential biomarkers of AD. Comparison with existing methods: Recent techniques have used sedimentation sucrose gradients to isolate EVs from brain tissue. However, here we demonstrate the advantages of floatation iodixanol density gradient isolation of small EVs, and provide evidence of EV enrichment by electron microscopy, immunoblot analysis, and quantitative mass spectrometry.

CONCLUSIONS

Together these findings offer a rigorous technique for enriching whole tissue-derived EVs for downstream analyses, and application of this approach to uncovering molecular changes in AD progression and other neurological conditions.