Exosomal transfer of proteins and RNAs at synapses in the nervous system

Role of exosome-derived miRNAs in diabetic wound angiogenesis

Chronic wounds with high disability are among the most common and serious complications of diabetes. Angiogenesis dysfunction impair wound healing in patients with diabetes. Compared with traditional therapies that can only provide symptomatic treatment, stem cells-owing to their powerful paracrine properties, can alleviate the pathogenesis of chronic diabetic wounds and even cure them. Exosome-derived microRNAs (miRNAs), important components of stem cell paracrine signaling, have been reported for therapeutic use in various disease models, including diabetic wounds. Exosome-derived miRNAs have been widely reported to be involved in regulating vascular function and have promising applications in the repair and regeneration of skin wounds. Therefore, this article aims to review the current status of the pathophysiology of exosome-derived miRNAs in the diabetes-induced impairment of wound healing, along with current knowledge of the underlying mechanisms, emphasizing the regulatory mechanism of angiogenesis, we hope to document the emerging theoretical basis for improving wound repair by restoring angiogenesis in diabetes.

Prospects and challenges of tissue-derived extracellular vesicles

Extracellular vesicles (EVs) are considered a vital component of cell-to-cell communication and represent a new frontier in diagnostics and a means to identify pathways for therapeutic intervention. Recently, studies have revealed the importance of tissue-derived EVs (Ti-EVs), which are EVs present in the interstitial spaces between cells, as they better represent the underlying physiology of complex, multicellular tissue microenvironments in biology and disease. EVs are native, lipid bilayer membraned nano-sized particles produced by all cells that are packaged with varied functional biomolecules including proteins, lipids, and nucleic acids. They are implicated in short- and long-range cellular communication and may elicit functional responses in recipient cells. To date, studies have often utilized cultured cells or biological fluids as a source for EVs that do not capture local molecular signatures of the tissue microenvironment. Recent work utilizing Ti-EVs has elucidated novel biomarkers for disease and provided insights into disease mechanisms that may lead to the development of novel therapeutic agents. Still, there are considerable challenges facing current studies. This review explores the vast potential and unique challenges for Ti-EV research and provides considerations for future studies that seek to advance this exciting field.

Restoring Synaptic Function: How Intranasal Delivery of 3D-Cultured hUSSC Exosomes Improve Learning and Memory Deficits in Alzheimer's Disease

Memory problems are often the first signs of cognitive impairment related to Alzheimer's disease (AD), and stem cells and stem cell-derived exosomes (EXOs) have been studied for their therapeutic potential to improve the disease signs. While many studies have shown the anti-inflammatory and immunomodulatory effects of stem cells and exosomes on improving memory in different AD models, there is still insufficient data to determine how they modulate neural plasticity to enhance spatial memory and learning ability. Therefore, we conducted a study to investigate the effects of exosomes derived from 3D-cultured human Unrestricted Somatic Stem Cells (hUSSCs) on spatial memory and neuroplasticity markers in a sporadic rat model of AD. Using male Wistar rats induced by intracerebral ventricle injection of streptozotocin, we demonstrated that intranasal administration of hUSSC-derived exosomes could decrease Aβ accumulation and improve learning and memory in the Morris water maze test. We also observed an increase in the expression of pre-synaptic and post-synaptic molecules involved in neuronal plasticity, including NMDAR1, integrin β1, synaptophysin, pPKCα, and GAP-43, in the hippocampus. Our findings suggest that intranasal administration of exosomes can ameliorate spatial learning and memory deficits in rats, at least in part, by increasing the expression of neuroplasticity proteins. These results may encourage researchers to further investigate the molecular pathways involved in memory improvement after stem cell and exosome therapy, with the goal of increasing the efficacy and safety of exosome-based treatments for AD.

Extracellular vesicles in nanomedicine and regenerative medicine: A review over the last decade

Small extracellular vesicles (sEVs) are known to be secreted by a vast majority of cells. These sEVs, specifically exosomes, induce specific cell-to-cell interactions and can activate signaling pathways in recipient cells through fusion or interaction. These nanovesicles possess several desirable properties, making them ideal for regenerative medicine and nanomedicine applications. These properties include exceptional stability, biocompatibility, wide biodistribution, and minimal immunogenicity. However, the practical utilization of sEVs, particularly in clinical settings and at a large scale, is hindered by the expensive procedures required for their isolation, limited circulation lifetime, and suboptimal targeting capacity. Despite these challenges, sEVs have demonstrated a remarkable ability to accommodate various cargoes and have found extensive applications in the biomedical sciences. To overcome the limitations of sEVs and broaden their potential applications, researchers should strive to deepen their understanding of current isolation, loading, and characterization techniques. Additionally, acquiring fundamental knowledge about sEVs origins and employing state-of-the-art methodologies in nanomedicine and regenerative medicine can expand the sEVs research scope. This review provides a comprehensive overview of state-of-the-art exosome-based strategies in diverse nanomedicine domains, encompassing cancer therapy, immunotherapy, and biomarker applications. Furthermore, we emphasize the immense potential of exosomes in regenerative medicine.

Stem Cell-Derived Exosomal MicroRNAs as Novel Potential Approach for Multiple Sclerosis Treatment

Multiple Sclerosis (MS) is an autoimmune disease of the central nervous system (CNS) characterized by inflammation and demyelination of CNS neurons. Up to now, there are many therapeutic strategies for MS but they are only being able to reduce progression of diseases and have not got any effect on repair and remyelination. Stem cell therapy is an appropriate method for regeneration but has limitations and problems. So recently, researches were used of exosomes that facilitate intercellular communication and transfer cell-to-cell biological information. MicroRNAs (miRNAs) are a class of short non-coding RNAs that we can used to their dysregulation in order to diseases diagnosis. The miRNAs of microvesicles obtained stem cells may change the fate of transplanted cells based on received signals of injured regions. The miRNAs existing in MSCs may be displayed the cell type and their biological activities. Current studies show also that the miRNAs create communication between stem cells and tissue-injured cells. In the present review, firstly we discuss the role of miRNAs dysregulation in MS patients and miRNAs expression by stem cells. Finally, in this study was confirmed the relationship of microRNAs involved in MS and miRNAs expressed by stem cells and interaction between them in order to find appropriate treatment methods in future for limit to disability progression.

Schwann cell-derived extracellular vesicles promote memory impairment associated with chronic neuropathic pain

BACKGROUND

The pathogenesis of memory impairment, a common complication of chronic neuropathic pain (CNP), has not been fully elucidated. Schwann cell (SC)-derived extracellular vesicles (EVs) contribute to remote organ injury. Here, we showed that SC-EVs may mediate pathological communication between SCs and hippocampal neurons in the context of CNP.

METHODS

We used an adeno-associated virus harboring the SC-specific promoter Mpz and expressing the CD63-GFP gene to track SC-EVs transport. microRNA (miRNA) expression profiles of EVs and gain-of-function and loss-of-function regulatory experiments revealed that miR-142-5p was the main cargo of SC-EVs. Next, luciferase reporter gene and phenotyping experiments confirmed the direct targets of miR-142-5p.

RESULTS

The contents and granule sizes of plasma EVs were significantly greater in rats with chronic sciatic nerve constriction injury (CCI)than in sham rats. Administration of the EV biogenesis inhibitor GW4869 ameliorated memory impairment in CCI rats and reversed CCI-associated dendritic spine damage. Notably, during CCI stress, SC-EVs could be transferred into the brain through the circulation and accumulate in the hippocampal CA1-CA3 regions. miR-142-5p was the main cargo wrapped in SC-EVs and mediated the development of CCI-associated memory impairment. Furthermore, α-actinin-4 (ACTN4), ELAV-like protein 4 (ELAVL4) and ubiquitin-specific peptidase 9 X-linked (USP9X) were demonstrated to be important downstream target genes for miR-142-5p-mediated regulation of dendritic spine damage in hippocampal neurons from CCI rats.

CONCLUSION

Together, these findings suggest that SCs-EVs and/or their cargo miR-142-5p may be potential therapeutic targets for memory impairment associated with CNP.

Role of non-coding RNAs and exosomal non-coding RNAs in vasculitis: A narrative review

A category of very uncommon systemic inflammatory blood vessel illnesses known as vasculitides. The pathogenesis and etiology of vasculitis are still poorly known. Despite all of the progress made in understanding the genetics and causes behind vasculitis, there is still more to learn. Epigenetic dysregulation is a significant contributor to immune-mediated illnesses, and epigenetic aberrancies in vasculitis are becoming more widely acknowledged. Less than 2 % of the genome contains protein-encoding DNA. Studies have shown that a variety of RNAs originating from the non-coding genome exist. Long non-coding RNAs (lncRNAs), microRNAs (miRNAs), and circular RNAs (circRNAs) have attracted the most attention in recent years as they are becoming more and more important regulators of different biological processes, such as diseases of the veins. Extracellular vehicles (EVs) such as exosomes, are membrane-bound vesicular structures that break free either during programmed cell death, such as apoptosis, pyroptosis, and necroptosis or during cell activation. Exosomes may be involved in harmful ways in inflammation, procoagulation, autoimmune reactions, endothelial dysfunction/damage, intimal hyperplasia and angiogenesis, all of which may be significant in vasculitis. Herein, we summarized various non-coding RNAs that are involved in vasculitides pathogenesis. Moreover, we highlighted the role of exosomes in vasculitides.

Mobile circular DNAs regulating memory and communication in CNS neurons

Stimuli that stimulate neurons elicit transcription of immediate-early genes, a process which requires local sites of chromosomal DNA to form double-strand breaks (DSBs) generated by topoisomerase IIb within a few minutes, followed by repair within a few hours. Wakefulness, exploring a novel environment, and contextual fear conditioning also elicit turn-on of synaptic genes requiring DSBs and repair. It has been reported (in non-neuronal cells) that extrachromosomal circular DNA can form at DSBs as the sites are repaired. I propose that activated neurons may generate extrachromosomal circular DNAs during repair at DSB sites, thus creating long-lasting "markers" of that activity pattern which contain sequences from their sites of origin and which regulate long-term gene expression. Although the population of extrachromosomal DNAs is diverse and overall associated with pathology, a subclass of small circular DNAs ("microDNAs," ∼100-400 bases long), largely derives from unique genomic sequences and has attractive features to act as stable, mobile circular DNAs to regulate gene expression in a sequence-specific manner. Circular DNAs can be templates for the transcription of RNAs, particularly small inhibitory siRNAs, circular RNAs and other non-coding RNAs that interact with microRNAs. These may regulate translation and transcription of other genes involved in synaptic plasticity, learning and memory. Another possible fate for mobile DNAs is to be inserted stably into chromosomes after new DSB sites are generated in response to subsequent activation events. Thus, the insertions of mobile DNAs into activity-induced genes may tend to inactivate them and aid in homeostatic regulation to avoid over-excitation, as well as providing a "counter" for a neuron's activation history. Moreover, activated neurons release secretory exosomes that can be transferred to recipient cells to regulate their gene expression. Mobile DNAs may be packaged into exosomes, released in an activity-dependent manner, and transferred to recipient cells, where they may be templates for regulatory RNAs and possibly incorporated into chromosomes. Finally, aging and neurodegenerative diseases (including Alzheimer's disease) are also associated with an increase in DSBs in neurons. It will become important in the future to assess how pathology-associated DSBs may relate to activity-induced mobile DNAs, and whether the latter may potentially contribute to pathogenesis.

Therapeutic efficacy and promise of stem cell-derived extracellular vesicles in Alzheimer's disease and other aging-related disorders

The term extracellular vesicles (EVs) refers to a variety of heterogeneous nanovesicles secreted by almost all cell types, primarily for intercellular communication and maintaining cellular homeostasis. The role of EVs has been widely reported in the genesis and progression of multiple pathological conditions, and these vesicles are suggested to serve as 'liquid biopsies'. In addition to their use as biomarkers, EVs secreted by specific cell types, especially with stem cell properties, have shown promise as cell-free nanotherapeutics. Stem cell-derived EVs (SC-EVs) have been increasingly used as an attractive alternative to stem cell therapies and have been reported to promote regeneration of aging-associated tissue loss and function. SC-EVs treatment ameliorates brain and peripheral aging, reproductive dysfunctions and inhibits cellular senescence, thereby reversing several aging-related disorders and dysfunctions. The anti-aging therapeutic potential of SC-EVs depends on multiple factors, including the type of stem cells, the age of the source stem cells, and their physiological state. In this review, we briefly describe studies related to the promising effects of SC-EVs against various aging-related pathologies, and then we focus in-depth on the therapeutic benefits of SC-EVs against Alzheimer's disease, one of the most devastating neurodegenerative diseases in elderly individuals. Numerous studies in transgenic mouse models have reported the usefulness of SC-EVs in targeting the pathological hallmarks of Alzheimer's disease, including amyloid plaques, neurofibrillary tangles, and neuroinflammation, leading to improved neuronal protection, synaptic plasticity, and cognitive measures. Cell culture studies have further identified the underlying molecular mechanisms through which SC-EVs reduce amyloid beta (Aβ) levels or shift microglia phenotype from pro-inflammatory to anti-inflammatory state. Interestingly, multiple routes of administration, including nasal delivery, have confirmed that SC-EVs could cross the blood-brain barrier. Due to this, SC-EVs have also been tested to deliver specific therapeutic cargo molecule/s (e.g., neprilysin) to the brain. Despite these promises, several challenges related to quality control, scalability, and biodistribution remain, hindering the realization of the vast clinical promise of SC-EVs.

A cellular regulator of the niche: telocyte

Interstitial cells are present in the environment of stem cells in order to increase stem cell proliferation and differentiation and they are important to increase the efficiency of their transplantation. Telocytes (TCs) play an important role both in the preservation of tissue organ integrity and in the pathophysiology of many diseases, especially cancer. They make homo- or heterocellular contacts to form the structure of 3D network through their telopodes and deliver signaling molecules via a juxtacrine and/or paracrine association by budding shed vesicles into the vascular, nervous and endocrine systems. During this interaction, along with organelles, mRNA, microRNA, long non-coding RNA, and genomic DNA are transferred. This review article not only specifies the properties of TCs and their roles in the tissue organ microenvironment but also gives information about the factors that play a role in the transport of epigenetic information by TCs.

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.

Receptor-receptor interactions and microvesicle exchange as mechanisms modulating signaling between neurons and astrocytes

It is well known that astrocytes play a significant metabolic role in the nervous tissue, maintaining the homeostasis of the extracellular space and of the blood-brain barrier, and providing trophic support to neurons. In addition, however, evidence exists indicating astrocytes as important elements for brain activity through signaling exchange with neurons. Astrocytes, indeed, can sense synaptic activity and their molecular machinery responds to neurotransmitters released by neurons with cytoplasmic Ca²⁺ elevations that, in turn, stimulate the release of neuroactive substances (gliotransmitters) influencing nearby neurons. In both cell types the recognition and transduction of this complex pattern of signals is mediated by specific receptors that are also involved in mechanisms tuning the intercellular cross-talk between astrocytes and neurons. Two of these mechanisms are the focus of the present discussion. The first concerns direct receptor-receptor interactions leading to the formation at the cell membrane of multimeric receptor complexes. The cooperativity that emerges in the actions of orthosteric and allosteric ligands of the monomers forming the assembly provides the cell decoding apparatus with sophisticated and flexible dynamics in terms of recognition and signal transduction pathways. A further mechanism of plasticity involving receptors is based on the transfer of elements of the cellular signaling apparatus via extracellular microvesicles acting as protective containers, which can lead to transient changes in the transmitting/decoding capabilities of the target cell.

Potential Roles of Exosomes in the Development and Detection of Malignant Mesothelioma: An Update

Malignant mesothelioma (MM) is a devastating cancer of mesothelial cells, caused by asbestos exposure. Limited knowledge regarding the detection of asbestos exposure and the early diagnosis of MM, as well as a lack of successful treatment options for this deadly cancer, project an immediate need to understand the mechanism(s) of MM development. With the recent discovery of nano-vesicles, namely exosomes, and their enormous potential to contain signature molecules representative of different diseases, as well as to communicate with distant targets, we were encouraged to explore their role(s) in MM biology. In this review, we summarize what we know so far about exosomes and MM based on our own studies and on published literature from other groups in the field. We expect that the information contained in this review will help advance the field of MM forward by revealing the mechanisms of MM development and survival. Based on this knowledge, future therapeutic strategies for MM can potentially be developed. We also hope that the outcome of our studies presented here may help in the detection of MM.

Extracellular vesicles in the study of Alzheimer's and Parkinson's diseases: Methodologies applied from cells to biofluids

Extracellular vesicles (EVs) are gaining increased importance in fundamental research as key players in disease pathogenic mechanisms, but also in translational and clinical research due to their value in biomarker discovery, either for diagnostics and/or therapeutics. In the first research scenario, the study of EVs isolated from neuronal models mimicking neurodegenerative diseases can open new avenues to better understand the pathological mechanisms underlying these conditions or to identify novel molecular targets for diagnosis and/or therapeutics. In the second research scenario, the easy availability of EVs in body fluids and the specificity of their cargo, which can reflect the cell of origin or disease profiles, turn these into attractive diagnostic tools. EVs with exosome-like characteristics, circulating in the bloodstream and other peripheral biofluids, constitute a non-invasive and rapid alternative to study several conditions, including brain-related disorders. In both cases, several EVs isolation methods are already available, but each neuronal model or biofluid presents its own challenges. Herein, a literature overview on EVs isolation methodologies from distinct neuronal models (cellular culture and brain tissue) and body fluids (serum, plasma, cerebrospinal fluid, urine and saliva) was carried out. Focus was given to approaches employed in the context of Alzheimer's and Parkinson's diseases, and the main research findings discussed. The topics here revised will facilitate the choice of EVs isolation methodologies and potentially prompt new discoveries in EVs research and in the neurodegenerative diseases field.

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

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

The Role of Glia Clocks in the Regulation of Sleep in Drosophila melanogaster

In Drosophila melanogaster, the pacemaker located in the brain plays the main role in maintaining circadian rhythms; however, peripheral oscillators including glial cells, are also crucial components of the circadian network. In the present study, we investigated an impact of oscillators located in astrocyte-like glia, the chiasm giant glia of the optic lobe, epithelial and subperineurial glia on sleep of Drosophila males. We described that oscillators located in astrocyte-like glia and chiasm giant glia are necessary to maintain daily changes in clock neurons arborizations, while those located in epithelial glia regulate amplitude of these changes. Finally, we showed that communication between glia and neurons through tripartite synapses formed by epithelial glia and, in effect, neurotransmission regulation plays important role in wake-promoting during the day.SIGNIFICANCE STATEMENT Circadian clock or pacemaker regulates many aspects of animals' physiology and behavior. The pacemaker is located in the brain and is composed of neurons. However, there are also additional oscillators, called peripheral clocks, which synchronize the main clock. Despite the critical role of glia in the clock machinery, little is known which type of glia houses peripheral oscillators and how they affect neuronal clocks. This study using Drosophila shows that oscillators in specific glia types maintain awakeness during the day by regulating the daily plasticity of clock neurons.

Prediction of Synaptically Localized RNAs in Human Neurons Using Developmental Brain Gene Expression Data

In the nervous system, synapses are special and pervasive structures between axonal and dendritic terminals, which facilitate electrical and chemical communications among neurons. Extensive studies have been conducted in mice and rats to explore the RNA pool at synapses and investigate RNA transport, local protein synthesis, and synaptic plasticity. However, owing to the experimental difficulties of studying human synaptic transcriptomes, the full pool of human synaptic RNAs remains largely unclear. We developed a new machine learning method, called PredSynRNA, to predict the synaptic localization of human RNAs. Training instances of dendritically localized RNAs were compiled from previous rodent studies, overcoming the shortage of empirical instances of human synaptic RNAs. Using RNA sequence and gene expression data as features, various models with different learning algorithms were constructed and evaluated. Strikingly, the models using the developmental brain gene expression features achieved superior performance for predicting synaptically localized RNAs. We examined the relevant expression features learned by PredSynRNA and used an independent test dataset to further validate the model performance. PredSynRNA models were then applied to the prediction and prioritization of candidate RNAs localized to human synapses, providing valuable targets for experimental investigations into neuronal mechanisms and brain disorders.

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

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

Intercellular Communication in the Central Nervous System as Deduced by Chemical Neuroanatomy and Quantitative Analysis of Images: Impact on Neuropharmacology

In the last decades, new evidence on brain structure and function has been acquired by morphological investigations based on synergic interactions between biochemical anatomy approaches, new techniques in microscopy and brain imaging, and quantitative analysis of the obtained images. This effort produced an expanded view on brain architecture, illustrating the central nervous system as a huge network of cells and regions in which intercellular communication processes, involving not only neurons but also other cell populations, virtually determine all aspects of the integrative function performed by the system. The main features of these processes are described. They include the two basic modes of intercellular communication identified (i.e., wiring and volume transmission) and mechanisms modulating the intercellular signaling, such as cotransmission and allosteric receptor-receptor interactions. These features may also open new possibilities for the development of novel pharmacological approaches to address central nervous system diseases. This aspect, with a potential major impact on molecular medicine, will be also briefly discussed.

Understanding the physical basis of memory: Molecular mechanisms of the engram

Memory, defined as the storage and use of learned information in the brain, is necessary to modulate behavior and critical for animals to adapt to their environments and survive. Despite being a cornerstone of brain function, questions surrounding the molecular and cellular mechanisms of how information is encoded, stored, and recalled remain largely unanswered. One widely held theory is that an engram is formed by a group of neurons that are active during learning, which undergoes biochemical and physical changes to store information in a stable state, and that are later reactivated during recall of the memory. In the past decade, the development of engram labeling methodologies has proven useful to investigate the biology of memory at the molecular and cellular levels. Engram technology allows the study of individual memories associated with particular experiences and their evolution over time, with enough experimental resolution to discriminate between different memory processes: learning (encoding), consolidation (the passage from short-term to long-term memories), and storage (the maintenance of memory in the brain). Here, we review the current understanding of memory formation at a molecular and cellular level by focusing on insights provided using engram technology.

Exosomal miRNA Profiling is a Potential Screening Route for Non-Functional Pituitary Adenoma

Non-functional pituitary adenomas (NFPAs) are one of the most prevalent pituitary adenoma subtypes. The lack of reliable screening approach for NFPAs for the insidious clinical course usually leads to delays in medical therapy and consequently worse prognosis. Hence, we employed a sequence cohort (patient: control, 6:2) and a validation cohort (patient: control, 22:8) to develop a serum exosomal miRNA profile-based method for NFPA screening and prognosis prediction. We found that a total of 1,395 kinds of human miRNA were detected. Compared with healthy donors, 18 up-regulated and 36 down-regulated miRNAs showed significant expression alterations in NFPA patients. Target genes of differentially expressed miRNAs are mainly enriched in axonogenesis and cancer-associated terms. After validation, hsa-miR-486-5p, hsa-miR-151a-5p, hsa-miR-652-3p_R+1, and hsa-miR-1180-3p were promising biomarkers for NFPA, in which miR-486-5p was the most competent one. After a median of 33 months of prospective follow-up, exosomal hsa-miR-486-5p also was an efficient predictive biomarker for progression or relapse of NFPAs. By protein-protein interaction network construction of hsa-miR-486-5p targeted genes, the core modules revealed a high possibility that exosomal hsa-miR-486-5p regulated tumor progression by epigenetic regulation of MAPK signaling pathways. In conclusion, exosomal hsa-miR-486-5p, hsa-miR-151a-5p, hsa-miR-652-3p_R+1, and hsa-miR-1180-3p are candidate biomarkers for diagnosis and screening of NFPAs. More importantly, prospective follow-up reveals that hsa-miR-486-5p can be regarded as a significant predictor for prognosis of NFPAs.

The Exosomal MicroRNA Profile Is Responsible for the Mesenchymal Stromal Cell Transplantation-Induced Improvement of Functional Recovery after Stroke in Rats

INTRODUCTION

The mechanism through which mesenchymal stromal cells (MSCs) enhance functional recovery in experimental models of stroke remains to be elucidated. This study was carried out to determine the microRNA (miRNA) profile elicited in response to MSC transplantation after stroke.

METHODS

This was an in vivo study on the effect of MSC transplantation on the exosomal miRNA profile in a rat model of middle cerebral artery occlusion (MCAO)-induced stroke. Eighteen male Sprague-Dawley rats were subjected to MCAO surgery (model group), and half received a transplantation of MSCs (model + MSC group) isolated from rat bone marrow. A sham-operated group (Sham) was included as a control. After 7 days, the volume of the brain lesion and severity of the functional impairments were measured. Exosomes were isolated from blood plasma samples for miRNA transcriptome analysis by Illumina sequencing.

RESULTS

The MCAO surgery successfully induced infarcts and neurological deficits in the rats, whereas the MSC transplantation significantly repaired these impairments. Illumina sequencing identified 764 known miRNAs, including 135 that were differentially expressed in common between the model + MSC and model, model and Sham, and model + MSC and Sham groups, respectively. Gene Ontology enrichment analysis revealed that the target genes of these miRNAs were associated with biological processes relevant to learning or memory and the development of the central and peripheral nervous systems. Pathway enrichment analysis identified a cluster of miRNAs (e.g., rno-miR-19b-3p, rno-miR-204-3p, rno-miR-125a-5p, rno-miR-672-3p, and rno-miR-667-3p) to be significantly related to the Janus kinase-signal transducer and activator of transcription, mechanistic target of rapamycin, phosphoinositide 3-kinases-Akt, and insulin signaling pathways via their control of their gene targets.

CONCLUSION

We confirmed that MSC transplantation repaired stroke-induced functional impairments in rats by regulating various pathways associated with nervous system protection and MSC differentiation through the deregulation of exosomal miRNAs.

MicroRNA-124 ameliorates autophagic dysregulation in glaucoma via regulation of P2X7-mediated Akt/mTOR signaling

Glaucoma is a neurodegenerative disease that leads to irrevocable blindness. In glaucoma, even though axonal damage and function deficit culminates in retinal ganglion cell (RGC) degeneration, our knowledge on the autophagic mechanisms and the role of specific microRNAs is still limited. In this study, we investigated the role of microRNA-124 (MiR-124) in surgically induced glaucomatous neurodegeneration using a mouse model. Animals were segregated into four cohorts of 10 each: (i) sham-operated (n = 10); (ii) surgically induced glaucoma (SIG; n = 10); (iii) SIG + miR-124 mimic; (iv) SIG + miR-NC. Chronic elevation of intraocular pressure (IOP) is a critical risk factor for glaucoma. In our study, chronically elevated IOP caused anterograde axonal transport (AAT) defect, increased the autophagic activity (manifested by significantly (p < 0.05) increased LC3-II/LC3-I ratio, beclin-1 and Atg7 protein expressions) and also downmodulated the protein expression of p-Akt and p-mTOR, mediated by the purinergic P2 receptor subtype 7 (P2X7) upmodulation-leading to retinal degeneration. However, administration of miR-124 mimic improved the retinal integrity and function, as indicated by the improved AAT function, normalized the autophagic dysfunction, modulated the protein expression of P2X7-mediated p-Akt and p-mTOR. Hence, we propose that development of miR-124-based advanced therapies might be a potential avenue in the treatment of glaucomatous neurodegeneration.

Mesenchymal Stem Cell-Derived Exosomes and MicroRNAs in Cartilage Regeneration: Biogenesis, Efficacy, miRNA Enrichment and Delivery

Exosomes are the small extracellular vesicles secreted by cells for intercellular communication. Exosomes are rich in therapeutic cargos such as microRNA (miRNA), long non-coding RNA (lncRNA), small interfering RNA (siRNA), DNA, protein, and lipids. Recently, many studies have focused on miRNAs as a promising therapeutic factor to support cartilage regeneration. Exosomes are known to contain a substantial amount of a variety of miRNAs. miRNAs regulate the post-transcriptional gene expression by base-pairing with the target messenger RNA (mRNA), leading to gene silencing. Several exosomal miRNAs have been found to play a role in cartilage regeneration by promoting chondrocyte proliferation and matrix secretion, reducing scar tissue formation, and subsiding inflammation. The exosomal miRNA cargo can be modulated using techniques such as cell transfection and priming as well as post-secretion modifications to upregulate specific miRNAs to enhance the therapeutic effect. Exosomes are delivered to the joints through direct injection or via encapsulation within a scaffold for sustained release. To date, exosome therapy for cartilage injuries has yet to be optimized as the ideal cell source for exosomes, and the dose and method of delivery have yet to be identified. More importantly, a deeper understanding of the role of exosomal miRNAs in cartilage repair is paramount for the development of more effective exosome therapy.

Mesenchymal Stem Cell-Derived Exosomes: Applications in Regenerative Medicine

Exosomes are a type of extracellular vesicles, produced within multivesicular bodies, that are then released into the extracellular space through a merging of the multivesicular body with the plasma membrane. These vesicles are secreted by almost all cell types to aid in a vast array of cellular functions, including intercellular communication, cell differentiation and proliferation, angiogenesis, stress response, and immune signaling. This ability to contribute to several distinct processes is due to the complexity of exosomes, as they carry a multitude of signaling moieties, including proteins, lipids, cell surface receptors, enzymes, cytokines, transcription factors, and nucleic acids. The favorable biological properties of exosomes including biocompatibility, stability, low toxicity, and proficient exchange of molecular cargos make exosomes prime candidates for tissue engineering and regenerative medicine. Exploring the functions and molecular payloads of exosomes can facilitate tissue regeneration therapies and provide mechanistic insight into paracrine modulation of cellular activities. In this review, we summarize the current knowledge of exosome biogenesis, composition, and isolation methods. We also discuss emerging healing properties of exosomes and exosomal cargos, such as microRNAs, in brain injuries, cardiovascular disease, and COVID-19 amongst others. Overall, this review highlights the burgeoning roles and potential applications of exosomes in regenerative medicine.

The role of Extracellular Vesicles during CNS development

With a diverse set of neuronal and glial cell populations, Central Nervous System (CNS) has one of the most complex structures in the body. Intercellular communication is therefore highly important to coordinate cell-to-cell interactions. Besides electrical and chemical messengers, CNS cells also benefit from another communication route, what is known as extracellular vesicles, to harmonize their interactions. Extracellular Vesicles (EVs) and their subtype exosomes are membranous particles secreted by cells and contain information packaged in the form of biomolecules such as small fragments of DNA, lipids, miRNAs, mRNAs, and proteins. They are able to efficiently drive changes upon their arrival to recipient cells. EVs actively participate in all stages of CNS development by stimulating neural cell proliferation, differentiation, synaptic formation, and mediating reciprocal interactions between neurons and oligodendrocyte for myelination process. The aim of the present review is to enlighten the presence and contribution of EVs at each CNS developmental milestone.

The Depolarization-Evoked, Ca2+-Dependent Release of Exosomes From Mouse Cortical Nerve Endings: New Insights Into Synaptic Transmission

Whether exosomes can be actively released from presynaptic nerve terminals is a matter of debate. To address the point, mouse cortical synaptosomes were incubated under basal and depolarizing (25 mM KCl-enriched medium) conditions, and extracellular vesicles were isolated from the synaptosomal supernatants to be characterized by dynamic light scattering, transmission electron microscopy, Western blot, and flow cytometry analyses. The structural and biochemical analysis unveiled that supernatants contain vesicles that have the size and the shape of exosomes, which were immunopositive for the exosomal markers TSG101, flotillin-1, CD63, and CD9. The marker content increased upon the exposure of nerve terminals to the high-KCl stimulus, consistent with an active release of the exosomes from the depolarized synaptosomes. High KCl-induced depolarization elicits the Ca2+-dependent exocytosis of glutamate. Interestingly, the depolarization-evoked release of exosomes from cortical synaptosomes also occurred in a Ca2+-dependent fashion, since the TSG101, CD63, and CD9 contents in the exosomal fraction isolated from supernatants of depolarized synaptosomes were significantly reduced when omitting external Ca2+ ions. Differently, (±)-baclofen (10 µM), which significantly reduced the glutamate exocytosis, did not affect the amount of exosomal markers, suggesting that the GABAB-mediated mechanism does not control the exosome release. Our findings suggest that the exposure of synaptosomes to a depolarizing stimulus elicits a presynaptic release of exosomes that occurs in a Ca2+-dependent fashion. The insensitivity to the presynaptic GABAB receptors, however, leaves open the question on whether the release of exosomes could be a druggable target for new therapeutic intervention for the cure of synaptopathies.

Living Proof of Activity of Extracellular Vesicles in the Central Nervous System

The central nervous system (CNS) consists of a heterogeneous population of cells with highly specialized functions. For optimal functioning of the CNS, in disease and in health, intricate communication between these cells is vital. One important mechanism of cellular communication is the release and uptake of extracellular vesicles (EVs). EVs are membrane enclosed particles actively released by cells, containing a wide array of proteins, lipids, RNA, and DNA. These EVs can be taken up by neighboring or distant cells, and influence a wide range of processes. Due to the complexity and relative inaccessibility of the CNS, our current understanding of the role of EVs is mainly derived in vitro work. However, recently new methods and techniques have opened the ability to study the role of EVs in the CNS in vivo. In this review, we discuss the current developments in our understanding of the role of EVs in the CNS in vivo.

The emerging role of exosomes in Alzheimer's disease

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

Exosomal miR-409-3p secreted from activated mast cells promotes microglial migration, activation and neuroinflammation by targeting Nr4a2 to activate the NF-κB pathway

Objective

Neuroinflammation plays a critical role in central nervous system diseases. Exosomal miRNAs released from various cells are implicated in cell-to-cell communication. Prior studies have placed substantial emphasis on the role of cytokines in mast cell-microglia interactions during neuroinflammation. However, it has never been clearly determined whether exosomal miRNAs participate in the interaction between mast cells and microglia and thus mediate neuroinflammation.

Methods

The characteristics of exosomes isolated from cell culture supernatants were confirmed by transmission electron microscopy (TEM), nanoparticle-tracking analysis (NTA) and Western blot. The transfer of PKH67-labelled exosomes and Cy3-labelled miR-409-3p was observed by fluorescence microscopy. Migration and activation of murine BV-2 microglial cells were evaluated through Transwell assays and immunofluorescence staining for Iba1 and CD68. CD86, IL-1β, IL-6 and TNF-α were assessed via qRT-PCR and ELISA. MiR-409-3p was detected by qRT-PCR. Nr4a2 and NF-κB levels were measured by western blot. Regulatory effects were identified by luciferase reporter assays.

Results

Lipopolysaccharide (LPS)-stimulated murine P815 mast cells secreted exosomes that were efficiently taken up by murine BV-2 cells, which promoted murine BV-2 cell migration and activation. LPS-P815 exosomes increased the CD86, IL-1β, IL-6 and TNF-α levels in murine BV-2 microglia. Furthermore, activated mast cells delivered exosomal miR-409-3p to murine BV-2 microglia. Upregulated miR-409-3p promoted murine BV-2 microglial migration, activation and neuroinflammation by targeting Nr4a2 to activate the NF-κB pathway.

Conclusion

Exosomal miR-409-3p secreted from activated mast cells promotes microglial migration, activation and neuroinflammation by targeting Nr4a2 to activate the NF-κB pathway, which provides evidence that not only cytokines but also exosomal miRNAs participate in neuroinflammation. In the future, targeting exosomal miRNAs may provide new insights into neuroinflammation.

Extracellular vesicles derived from mesenchymal stem cells: A platform that can be engineered

Mesenchymal stem cells play an important role in tissue damage and repair. This role is mainly due to a paracrine mechanism, and extracellular vesicles (EVs) are an important part of the paracrine function. EVs play a vital role in many aspects of cell homeostasis, physiology, and pathology, and EVs can be used as clinical biomarkers, vaccines, or drug delivery vehicles. A large number of studies have shown that EVs derived from mesenchymal stem cells (MSC-EVs) play an important role in the treatment of various diseases. However, the problems of low production, low retention rate, and poor targeting of MSC-EVs are obstacles to current clinical applications. The engineering transformation of MSC-EVs can make up for those shortcomings, thereby improving treatment efficiency. This review summarizes the latest research progress of MSC-EV direct and indirect engineering transformation from the aspects of improving MSC-EV retention rate, yield, targeting, and MSC-EV visualization research, and proposes some feasible MSC-EV engineering methods of transformation.

Extracellular Vesicles as Innovative Tool for Diagnosis, Regeneration and Protection against Neurological Damage

Extracellular vesicles (EVs) have recently attracted a great deal of interest as they may represent a new biosignaling paradigm. According to the mode of biogenesis, size and composition, two broad categories of EVs have been described, exosomes and microvesicles. EVs have been shown to carry cargoes of signaling proteins, RNA species, DNA and lipids. Once released, their content is selectively taken up by near or distant target cells, influencing their behavior. Exosomes are involved in cell–cell communication in a wide range of embryonic developmental processes and in fetal–maternal communication. In the present review, an outline of the role of EVs in neural development, regeneration and diseases is presented. EVs can act as regulators of normal homeostasis, but they can also promote either neuroinflammation/degeneration or tissue repair in pathological conditions, depending on their content. Since EV molecular cargo constitutes a representation of the origin cell status, EVs can be exploited in the diagnosis of several diseases. Due to their capability to cross the blood–brain barrier (BBB), EVs not only have been suggested for the diagnosis of central nervous system disorders by means of minimally invasive procedures, i.e., “liquid biopsies”, but they are also considered attractive tools for targeted drug delivery across the BBB. From the therapeutic perspective, mesenchymal stem cells (MSCs) represent one of the most promising sources of EVs. In particular, the neuroprotective properties of MSCs derived from the dental pulp are here discussed.

Circulating plasma microRNA signature for the diagnosis of cervical cancer

OBJECTIVE

To determine the utility of plasma microRNAs (miRNAs) as biomarkers in cervical cancer (CC).

METHODS

Some studies were conducted about the specific expression of plasma miRNAs in the diagnosis of CC. Plasma samples of 97 CC patients and 87 normal controls (NCs) were used to identify dysregulation of miRNAs in the training, testing, and external validation phases. Receiver operating characteristic (ROC) curves and area under the ROC curve (AUC) were used to evaluate the sensitivity and specificity of identified individual miRNAs and miRNA panels for the diagnosis of CC. Expression levels of specific miRNAs were also examined in plasma exosomes and tissue samples of CC patients.

RESULTS

Four plasma miRNAs (miR-146a-5p, miR-151a-3p, miR-2110 and miR-21-5p) which showed up-regulation were identified and validated in CC patients. A panel of the four miRNAs were constructed as potential diagnostic markers for CC. The AUCs of the panel of these four-miRNAs for the training, testing, and external validation phases were 0.911, 0.774, and 0.786, respectively. miR-146a-5p and miR-21-5p levels were all up-regulated in CC tissue specimens, whereas miR-146a-5p, miR-151a-3p, and miR-2110 levels were up-regulated in plasma exosomes.

CONCLUSION

The signature of the four-miRNAs identified in peripheral plasma is a promising novel biomarker for the diagnosis of CC.

Proteomic analysis reveals a biosignature of decreased synaptic protein in cerebrospinal fluid of major depressive disorder

Major depressive disorder (MDD) is a leading cause of morbidity with a lifetime prevalence of 10%. There is increasing evidence suggesting synaptic dysfunction and impaired integrity of certain brain circuits in MDD. Here we investigate the cerebrospinal fluid proteome of psychiatric patients focusing on MDD by deep proteomic profiling approach combined with a further validation step using targeted mass spectrometry. We demonstrate profound CSF proteomic changes during on-going depression episodes in MDD patients (n = 40) in comparison to controls (n = 27), schizophrenia spectrum disorder (n = 13), and bipolar disorder patients (n = 11). The discovery analysis with isobaric tags for relative and absolute quantitation (iTRAQ) reveals changes in proteins associated with synaptic transmission, myelination, and Wnt signaling in CSF of MDD. The multiple reaction monitoring (MRM) validation analysis confirms significantly decreased levels of eight proteins including the membrane synaptic proteins neurexin 3 (NRXN3), contactin-associated protein-like 4 (CNTNAP4), and glutamate ionotropic receptor AMPA type subunit 4 (GRIA4) in the CSF of MDD patients in comparison to the controls. Overall, the study demonstrates proteins that constitute an MDD biosignature for further validation studies and provides insight into the pathophysiology of MDD and other psychiatric disorders.

Reprogramming extracellular vesicles with engineered proteins

Extracellular vesicles (EVs) have been emerging as a new class of cell-free therapy for the treatment of a variety of diseases, including cancer, tissue injuries, and inflammatory diseases. Reprograming native EVs by genetic engineering and other approaches offers an attractive prospect of extending therapeutic capabilities of EVs beyond their natural functions and properties. In this review article, we survey the state-of-the-art methods of EVs engineering and summarize major therapeutic applications of the reprogrammed EVs.

Analysis of Adult Neural Retina Extracellular Vesicle Release, RNA Transport and Proteomic Cargo

Purpose

Extracellular vesicles (EVs) contain RNA and protein cargo reflective of the genotype and phenotype of the releasing cell of origin. Adult neural retina EV release, RNA transfer, and proteomic cargo are the focus of this study.

Methods

Adult wild-type mouse retinae were cultured and released EV diameters and concentrations quantified using Nanosight. Immunogold transmission electron microscopy (TEM) was used to image EV ultrastructure and marker protein localization. Quantitative real-time polymerase chain reaction (qRT-PCR) was used to analyze retinal cell transcripts present in EVs. Super-resolution microscopy was used to image fluorescent (green) RNA and (red) lipid membrane labeled EVs, released by adult retina, and internalized by isolated retinal cells. Mass spectrometry was used to characterize the proteomes of adult retina and EVs.

Results

Adult neural retina released EVs at a rate of 1.42 +/- 0.08 × 108/mL over 5 days, with diameters ranging from 30 to 910 nm. The canonical EV markers CD63 and Tsg101 localized to retinal EVs. Adult retinal and neuronal mRNA species present in both retina and EVs included rhodopsin and the neuronal nuclei marker NeuN. Fluorescently labeled RNA in retinal cells was enclosed in EVs, transported to, and uptaken by co-cultured adult retinal cells. Proteomic analysis revealed 1696 protein species detected only in retinal cells, 957 species shared between retina and EVs, and 82 detected only in EVs.

Conclusions

The adult neural retina constitutively releases EVs with molecular cargo capable of intercellular transport and predicted involvement in biological processes including retinal physiology, mRNA processing, and transcription regulation within the retinal microenvironment.

Proteome characterization of small extracellular vesicles from spared nerve injury model of neuropathic pain

Exosomes are 30-150 nm extracellular vesicles mediating intercellular communication. Disease states can alter exosome composition affecting the message carried and thereby, its functional impact. The objective of this study was to identify proteins present in these vesicles in a mouse model of neuropathic pain induced by spared nerve injury (SNI). Small extracellular vesicles (sEVs) were purified from serum four weeks after SNI surgery and the protein composition was determined using tandem mass spectrometry and cytokine array. Proteomic analysis detected 274 gene products within sEVs. Of these, 24 were unique to SNI model, 100 to sham surgery control and five to naïve control samples. In addition to commonly expressed sEVs proteins, multiple members of serpin and complement family were detected in sEVs. Cytokine profiling using a membrane-based antibody array showed significant upregulation of complement component 5a (C5a) and Intercellular Adhesion Molecule 1 (ICAM-1) in sEVs from SNI model compared to sham control. We observed a differential distribution of C5a and ICAM-1 within sEVs and serum between sham and SNI, indicating changes from local or paracrine to long distance signaling under neuropathic pain. Our studies suggest critical roles for cargo sorting of vesicular proteins in mediating signaling mechanisms underlying neuropathic pain. SIGNIFICANCE: Approximately 100 million U.S. adults are burdened by chronic pain. Neuropathic pain resulting from injury or dysfunction of the nervous system is challenging to treat. Unlike acute pain that resolves over time, chronic pain persists resulting in changes in the peripheral and central nervous system. The transport of biomolecular cargo comprised of proteins and RNAs by small extracellular vesicles (sEVs) including exosomes has been proposed to be a fundamental mode of intercellular communication. To obtain insights on the role of exosome-mediated information transfer in the context of neuropathic pain, we investigated alterations in protein composition of sEVs in a mouse model of neuropathic pain induced by spared nerve injury (SNI). Our studies using mass spectrometry and cytokine array show that sEVs from SNI model harbor unique proteins. We observed an upregulation of C5a and ICAM-1 in exosomes from SNI model compared to control. There was a differential distribution of C5a and ICAM-1 within exosomes and serum, between control and SNI suggesting a switch from local to long distance signaling. Our studies suggest critical roles for cargo sorting of vesicular proteins in mediating signaling under neuropathic pain.

Exosome Production Is Key to Neuronal Endosomal Pathway Integrity in Neurodegenerative Diseases

Dysfunction of the endosomal–lysosomal system is a prominent pathogenic factor in Alzheimer’s disease (AD) and other neurodevelopmental and neurodegenerative disorders. We and others have extensively characterized the neuronal endosomal pathway pathology that results from either triplication of the amyloid-β precursor protein (APP) gene in Down syndrome (DS) or from expression of the apolipoprotein E ε4 allele (APOE4), the greatest genetic risk factor for late-onset AD. More recently brain exosomes, extracellular vesicles that are generated within and released from endosomal compartments, have been shown to be altered in DS and by APOE4 expression. In this review, we discuss the emerging data arguing for an interdependence between exosome production and endosomal pathway integrity in the brain. In vitro and in vivo studies indicate that altered trafficking through the endosomal pathway or compromised cargo turnover within lysosomes can affect the production, secretion, and content of exosomes. Conversely, exosome biogenesis can affect the endosomal–lysosomal system. Indeed, we propose that efficient exosome release helps to modulate flux through the neuronal endosomal pathway by decompressing potential “traffic jams.” Exosome secretion may have the added benefit of unburdening the neuron’s lysosomal system by delivering endosomal–lysosomal material into the extracellular space, where other cell types may contribute to the degradation of neuronal debris. Thus, maintaining robust neuronal exosome production may prevent or mitigate endosomal and lysosomal abnormalities linked to aging and neurodegenerative diseases. While the current evidence suggests that the exosomal system in the brain can be modulated both by membrane lipid composition and the expression of key proteins that contribute to the formation and secretion of exosomes, how exosomal pathway-regulatory elements sense and respond to perturbations in the endosomal pathway is not well understood. Based upon findings from the extensively studied DS and APOE4 models, we propose that enhanced neuronal exosome secretion can be a protective response, reducing pathological disruption of the endosomal–lysosomal system in disease-vulnerable neurons. Developing therapeutic approaches that help to maintain or enhance neuronal exosome biogenesis and release may be beneficial in a range of disorders of the central nervous system.

Adenosine A2A-dopamine D2 receptor-receptor interaction in neurons and astrocytes: Evidence and perspectives

The discovery of receptor-receptor interactions in the early 1980s, together with a more accurate focusing of allosteric mechanisms in proteins, expanded the knowledge on the G protein-coupled receptor (GPCR)-mediated signaling processes. GPCRs were seen to operate not only as monomers, but also as quaternary structures shaped by allosteric interactions. These integrative mechanisms can change the function of the GPCRs involved, leading to a sophisticated dynamic of the receptor assembly in terms of modulation of recognition and signaling. In this context, the heterodimeric complex formed by the adenosine A_2A and the dopamine D₂ receptors likely represents a prototypical example. The pharmacological evidence obtained, together with the tissue distribution of the A_2A-D₂ heteromeric complexes, suggested they could represent a target for new therapeutic strategies addressing significant disorders of the central nervous system. The research findings and the perspectives they offer from the therapeutic standpoint are the focus of the here presented discussion.

Circulating miRNAs as Biomarker in Cancer

Deregulation of microRNA expression has been shown to play an important role in human malignancies. The identification of circulating-free miRNAs in biofluids a decade ago led to great enthusiasm and motivation to develop non-invasive tests based on the expression of these small non-coding RNAs. Herein, we review the progress within the field of research for identifying circulating miRNA cancer biomarkers and discuss the advantages and challenges associated with this. We also discuss the methodological and analytical variables, which may influence the final miRNA quantification and the importance of standardizing pre-analytical, analytical, and post-analytical processes in order to enable a successful translation of the results from basic research into the clinics.

Muscle-Derived Extracellular Vesicles Influence Motor Neuron Regeneration Accuracy

Extracellular vesicles are lipid bilayer-enclosed extracellular structures. Although the term extracellular vesicles is quite inclusive, it generally refers to exosomes (<200 nm), and microvesicles (~100-1000 nm). Such vesicles are resistant to degradation and can contain proteins, lipids, and nucleic acids. Although it was previously thought that the primary purpose of such vesicles was to rid cells of unwanted components, it is now becoming increasingly clear that they can function as intercellular messengers, sometimes operating over long distances. As such, there is now intense interest in extracellular vesicles in fields as diverse as immunology, cell biology, cancer, and more recently, neuroscience. The influence that such extracellular vesicles might exert on peripheral nerve regeneration is just beginning to be investigated. In the current studies we show that muscle-derived extracellular vesicles significantly influence the anatomical accuracy of motor neuron regeneration in the rat femoral nerve. These findings suggest a basic cellular mechanism by which target end-organs could guide their own reinnervation following nerve injury.

The Small RNA Repertoire of Small Extracellular Vesicles Isolated From Donor Kidney Preservation Fluid Provides a Source for Biomarker Discovery for Organ Quality and Posttransplantation Graft Function

Supplemental Digital Content is available in the text.

Delayed graft function (DGF) after kidney transplantation is negatively associated with long-term graft function and survival. Kidney function after transplantation depends on multiple factors, both donor- and recipient-associated. Prediction of posttransplantation graft function would allow timely intervention to optimize patient care and survival. Currently, graft-based predictions can be made based on histological and molecular analyses of 0-hour biopsy samples. However, such analyses are currently not implemented, as biopsy samples represent only a very small portion of the entire graft and are not routinely analyzed in all transplantation centers. Alternatives are thus required.

Exosomal microRNA and stroke: A review

Blood vessels rupture or occlusion in brain results in stroke. Stroke is the major reason for mortality and dysfunction worldwide. Despite several attempts, there are no any approved therapeutic approaches for stroke subjects. The most neuroprotective agents showed the positive effects in preclinical reports, while there are no significant therapeutic impacts in the clinical trials. MicroRNAs (miRNAs) are small noncoding RNAs which involved in the modulation of a variety of cellular and molecular pathways. Given that deregulation of these molecules is related to initiation and progression of stroke. Exosomes are nano-carriers which are able to transfer different cargos such as miRNAs to recipient cells. Increasing evidence revealed that exosomal miRNAs are one of very important factors which are involved in the pathogenesis of stroke. Hence, more understanding about the role of exosomal miRNAs in stroke pathogenesis could contribute in discovering and developing new therapeutic approaches. Moreover, it has been proved the exosomal miRNAs could be used as noninvasive biomarkers in diagnosis and monitoring response to therapy in subjects with stroke. Herein for first time, we summarized different exosomal miRNAs involved in pathogenesis of stroke.

Exosomes Treatment Mitigates Ischemic Brain Damage but Does Not Improve Post-Stroke Neurological Outcome

Background/Aims:

Recent studies demonstrated that the treatment with mesenchymal stem cells (MSCs) obtained from the human umbilical cord blood improved survival, reduced brain damage, prevented apoptosis, suppressed inflammatory responses, downregulated the DNA damage-inducing genes, upregulated the DNA repair genes, and facilitated neurological recovery in stroke-induced animals. Emerging stroke literature supports the concept that the exosomes released from MSCs are the primary biological principles underlying the post-stroke neuroprotection offered by MSCs treatment.

Methods:

Because the treatment with exosomes has a great potential to overcome the limitations associated with cell-based therapies, we tested the efficacy of exosomes secreted from HUCB-MSCs under standard culture conditions on post-stroke brain damage and neurological outcome in a rat model of ischemic stroke by performing TTC staining as well as the modified neurological severity scores, modified adhesive removal, beam-walking, and accelerating Rotarod performance tests before ischemia and at regular intervals until seven days reperfusion.

Results:

Exosomes treatment attenuated the infarct size. Treatment with exosomes did not affect the post-stroke survival rate and body weight changes, but exacerbated the somatosensory and motor dysfunction and adversely affected the natural recovery that occurs without any treatment.

Conclusion:

Treatment with exosomes secreted from HUCB-MSCs under standard culture conditions attenuates the ischemic brain damage but does not improve the post-stroke neurological outcome.

Exosomes Secreted by the Cocultures of Normal and Oxygen-Glucose-Deprived Stem Cells Improve Post-stroke Outcome

Emerging stroke literature suggests that treatment of experimentally induced stroke with stem cells offered post-stroke neuroprotection via exosomes produced by these cells. Treatment with exosomes has great potential to overcome the limitations associated with cell-based therapies. However, in our preliminary studies, we noticed that the exosomes released from human umbilical cord blood-derived mesenchymal stem cells (MSCs) under standard culture conditions did not improve the post-stroke neurological outcome. Because of this apparent discrepancy, we hypothesized that exosome characteristics vary with the conditions of their production. Specifically, we suggest that the exosomes produced from the cocultures of regular and oxygen-glucose-deprived (OGD) MSCs in vitro would represent the exosomes produced from MSCs that are exposed to ischemic brain cells in vivo, and offer similar therapeutic benefits that the cell treatment would provide. We tested the efficacy of therapy with exosomes secreted from human umbilical cord blood (HUCB)-derived MSCs under in vitro hypoxic conditions on post-stroke brain damage and neurological outcome in a rat model of transient focal cerebral ischemia. We performed the TTC staining procedure as well as the neurological tests including the modified neurological severity scores (mNSS), the modified adhesive removal (sticky-tape), and the beam walking tests before ischemia and at regular intervals until 7 days reperfusion. Treatment with exosomes obtained from the cocultures of normal and OGD-induced MSCs reduced the infarct size and ipsilateral hemisphere swelling, preserved the neurological function, and facilitated the recovery of stroke-induced rats. Based on the results, we conclude that the treatment with exosomes secreted from MSCs at appropriate experimental conditions attenuates the post-stroke brain damage and improves the neurological outcome.

Microvesicles from cerebrospinal fluid of patients with Alzheimer's disease display reduced concentrations of tau and APP protein

Microvesicles are small membranous particles generated during cellular activation or stress. The analysis of the content and the surface of microvesicles allow conclusions about the cells they are originating from and the underlying pathology. Therefore, CSF microvesicles have been suggested to be promising targets to monitor the (etio)pathology of neurodegenerative diseases. Microvesicles in the CSF of 15 patients with Alzheimer’s disease and 15 controls were analyzed by flow cytometry regarding the levels of CD3, CD4, CD45, CD64, BACE1, Aβ, APP and tau. The results were replicated in a second cohort comprising 14 patients with Alzheimer’s disease and 9 controls. The levels of tau and APP were reduced in microvesicles of Alzheimer’s disease patients. A significant change was neither observed in the number of microvesicles nor in the expression of the other antigens. Tau and APP in microvesicles separated patients with Alzheimer’s disease from controls with an AUC of 0.84 and 0.89 respectively. We conclude that tau and APP in CSF microvesicles are promising biomarkers which could directly provide information about the Alzheimer pathology on a cellular level.

Hypoxia preconditioning promotes bone marrow mesenchymal stem cells survival by inducing HIF-1α in injured neuronal cells derived exosomes culture system

Bone marrow derived stem cells (BMSCs) transplantation are viewed as a promising therapeutic candidate for spinal cord injury (SCI). However, the inflammatory microenvironment in the spinal cord following SCI limits the survival and efficacy of transplanted BMSCs. In this study, we investigate whether injured neuronal cells derived exosomes would influence the survival of transplanted BMSCs after SCI. In order to mimic the microenvironment in SCI that the neuronal cells or transplanted BMSCs suffer in vivo, PC12 cells conditioned medium and PC12 cell’s exosomes collected from H₂O₂-treated PC12 cell’s culture medium were cultured with BMSCs under oxidative stress in vitro. PC12 cells conditioned medium and PC12 cell’s exosomes significantly accelerated the apoptosis of BMSCs induced by H₂O₂. Moreover, the cleaved caspase-3, cytochrome (Cyt) C, lactate dehydrogenase (LDH) releases, and apoptotic percentage were increased, and the ratio of Bcl-2/Bax and cell viability were decreased. Inhibition of exosome secretion via Rab27a small interfering RNA prevented BMSCs apoptosis in vitro. In addition, hypoxia-preconditioned promoted the survival of BMSCs under oxidative stress both in vivo after SCI and in vitro. Our results also indicate that HIF-1α plays a central role in the survival of BMSCs in hypoxia pretreatment under oxidative stress conditions. siRNA-HIF-1α increased apoptosis of BMSCs; in contrast, HIF-1α inducer FG-4592 attenuated apoptosis of BMSCs. Taken together, we found that the injured PC12 cells derived exosomes accelerate BMSCs apoptosis after SCI and in vitro, hypoxia pretreatment or activating expression of HIF-1α to be important in the survival of BMSCs after transplantation, which provides a foundation for application of BMSCs in therapeutic potential for SCI.

Mast cell-neural interactions contribute to pain and itch

Mast cells are best recognized for their role in allergy and anaphylaxis, but increasing evidence supports their role in neurogenic inflammation leading to pain and itch. Mast cells act as a "power house" by releasing algogenic and pruritogenic mediators, which initiate a reciprocal communication with specific nociceptors on sensory nerve fibers. Consequently, nerve fibers release inflammatory and vasoactive neuropeptides, which in turn activate mast cells in a feedback mechanism, thus promoting a vicious cycle of mast cell and nociceptor activation leading to neurogenic inflammation and pain/pruritus. Mechanisms underlying mast cell differentiation, activation, and intercellular interactions with inflammatory, vascular, and neural systems are deeply influenced by their microenvironment, imparting enormous heterogeneity and complexity in understanding their contribution to pain and pruritus. Neurogenic inflammation is central to both pain and pruritus, but specific mediators released by mast cells to promote this process may vary depending upon their location, stimuli, underlying pathology, gender, and species. Therefore, in this review, we present the contribution of mast cells in pathological conditions, including distressing pruritus exacerbated by psychologic stress and experienced by the majority of patients with psoriasis and atopic dermatitis and in different pain syndromes due to mastocytosis, sickle cell disease, and cancer.