Identification of State-Specific Proteomic and Transcriptomic Signatures of Microglia-Derived Extracellular Vesicles

Research progress on the mechanisms of microglial extracellular vesicles affecting the prognosis of ischemic stroke

Ischemic stroke is the major type of stroke and one of the main causes of morbidity, mortality, and long-term disability worldwide. Microglia play a complex and crucial role in stroke. They are the primary immune cells in the brain and can rapidly respond to the pathological changes caused by stroke. They promote neuroprotection and repair after ischemic stroke through various mechanisms, such as activation and polarization, dynamic interactions with other cells (neurons, astrocytes, oligodendrocytes, vascular endothelial cells, etc.), and phagocytosis to clear dead cell debris. Among the multiple pathways through which microglia exert their neuroprotective effects, the secretion of extracellular vesicles is one of the most important. The focus of this review is to analyze the latest progress in research on ischemic stroke related to microglia-derived extracellular vesicles, discuss their mechanisms of action, and provide new strategies for improving stroke prognosis. To obtain relevant articles, we conducted a comprehensive search in Pubmed and Web of Science, with keywords related to ischemic stroke and microglia-derived extracellular vesicles or exosomes. A total of 59 articles were included in the review. Existing studies have shown that after a stroke occurs, microglia release extracellular vesicles containing proteins, nucleic acids, metabolites, etc. These vesicles target corresponding receptor cells and can slow down the development of stroke and improve stroke outcomes through various means, such as reducing neuronal apoptosis, inhibiting neuronal autophagy, suppressing neuronal ferroptosis, preventing neuronal pyroptosis, alleviating inflammatory responses, reducing glial scar formation, promoting myelin regeneration and repair, and facilitating blood-brain barrier repair.

Exosomes from polarized Microglia: Proteomic insights into potential mechanisms affecting intracerebral hemorrhage

Intracerebral hemorrhage (ICH) is a devastating form of stroke associated with significant morbidity and mortality. Microglia are intracranial innate immune cell that play critical roles in Intracerebral hemorrhage through direct or indirect means. Vesicle transport is a fundamental mechanism of intercellular communication. Recent studies have identified microglia in specific polarized states correlate with pathogenesis, material and signal transmission in ICH through derived extracellular vesicles. Diverse polarization states trigger distinct functions, however, the exosome proteomes across these states remain poorly characterized. Here, we hypothesized that microglia exosomal profiles vary with polarization states, impacting their functional repertoire and influencing outcomes in cerebral hemorrhage. In vitro model of cerebral hemorrhage, administration of 20 μg/ml LPS-induced M1 microglia derived exosomes (M1-Exo) with HT22 enhanced hemin-induced neuronal death, while IL-4-induced M2 microglia derived exosomes (M2-Exo) significantly reduced hemin-induced cell apoptosis and inflammation. Then we identified novel state-specific proteomic profiles of microglia-derived exosomes under these polarization conditions through label-free quantitative mass spectrometry (LFQ-MS). Analysis of protein content identified several exosomal signature proteins and hundreds of differentially expressed proteins across polarization states. Specifically, proteins including UMOD, NLRP3, ACOD1, IL1RN, heme oxygenase 1 (HMOX1), CCL4, and TNFRSF1B in M1-Exo were enriched in inflammatory pathways, while those in M2-Exo exhibited enrichment in autophagy, ubiquitination, and mitochondrial respiration. The analysis of those diverse exosomal proteins suggested unique proteomic profiles and possible intracellular signal transmission and regulation mechanisms. Together, these findings offer new insights and resources for studying microglia-derived exosome and pave the way for the development of novel therapeutic strategies targeting microglial exosome-mediated pathways.

The Yin and Yang of Microglia-Derived Extracellular Vesicles in CNS Injury and Diseases

Microglia, the resident immune cells of the central nervous system (CNS), play a crucial role in maintaining neural homeostasis but can also contribute to disease and injury when this state is disrupted or conversely play a pivotal role in neurorepair. One way that microglia exert their effects is through the secretion of small vesicles, microglia-derived exosomes (MGEVs). Exosomes facilitate intercellular communication through transported cargoes of proteins, lipids, RNA, and other bioactive molecules that can alter the behavior of the cells that internalize them. Under normal physiological conditions, MGEVs are essential to homeostasis, whereas the dysregulation of their production and/or alterations in their cargoes have been implicated in the pathogenesis of numerous neurodegenerative diseases, including Alzheimer's disease (AD), Parkinson's disease (PD), multiple sclerosis (MS), spinal cord injury (SCI), and traumatic brain injury (TBI). In contrast, MGEVs may also offer therapeutic potential by reversing inflammation or being amenable to engineering for the delivery of beneficial biologics or drugs. The effects of MGEVs are determined by the phenotypic state of the parent microglia. Exosomes from anti-inflammatory or pro-regenerative microglia support neurorepair and cell survival by delivering neurotrophic factors, anti-inflammatory mediators, and molecular chaperones. Further, MGEVs can also deliver components like mitochondrial DNA (mtDNA) and proteins to damaged neurons to enhance cellular metabolism and resilience. MGEVs derived from pro-inflammatory microglia can have detrimental effects on neural health. Their cargo often contains pro-inflammatory cytokines, molecules involved in oxidative stress, and neurotoxic proteins, which can exacerbate neuroinflammation, contribute to neuronal damage, and impair synaptic function, hindering neurorepair processes. The role of MGEVs in neurodegeneration and injury-whether beneficial or harmful-largely depends on how they modulate inflammation through the pro- and anti-inflammatory factors in their cargo, including cytokines and microRNAs. In addition, through the propagation of pathological proteins, such as amyloid-beta and alpha-synuclein, MGEVs can also contribute to disease progression in disorders such as AD and PD, or by the transfer of apoptotic or necrotic factors, they can induce neuron toxicity or trigger glial scarring during neurological injury. In this review, we have provided a comprehensive and up-to-date understanding of the molecular mechanisms underlying the multifaceted role of MGEVs in neurological injury and disease. In particular, the role that specific exosome cargoes play in various pathological conditions, either in disease progression or recovery, will be discussed. The therapeutic potential of MGEVs has been highlighted including potential engineering methodologies that have been employed to alter their cargoes or cell-selective targeting. Understanding the factors that influence the balance between beneficial and detrimental exosome signaling in the CNS is crucial for developing new therapeutic strategies for neurodegenerative diseases and neurotrauma.

Transcriptomic analysis and fusion gene identifications of midbody remnants released from colorectal cancer cells reveals they are molecularly distinct from exosomes and microparticles

Previously, we reported that human primary (SW480) and metastatic (SW620) colorectal (CRC) cells release three classes of membrane-encapsulated extracellular vesicles (EVs); midbody remnants (MBRs), exosomes (Exos), and microparticles (MPs). We reported that MBRs were molecularly distinct at the protein level. To gain further biochemical insights into MBRs, Exos, and MPs and their emerging role in CRC, we performed, and report here, for the first time, a comprehensive transcriptome and long noncoding RNA sequencing analysis and fusion gene identification of these three EV classes using the next-generation RNA sequencing technique. Differential transcript expression analysis revealed that MBRs have a distinct transcriptomic profile compared to Exos and MPs with a high enrichment of mitochondrial transcripts lncRNA/pseudogene transcripts that are predicted to bind to ribonucleoprotein complexes, spliceosome, and RNA/stress granule proteins. A salient finding from this study is a high enrichment of several fusion genes in MBRs compared to Exos, MPs, and cell lysates from their parental cells such as MSH2 (gene encoded DNA mismatch repair protein MSH2). This suggests potential EV-liquid biopsy targets for cancer detection. Importantly, the expression of cancer progression-related transcripts found in EV classes derived from SW480 (EGFR) and SW620 (MET and MACCA1) cell lines reflects their parental cell types. Our study is the report of RNA and fusion gene compositions within MBRs (including Exos and MPs) that could have an impact on EV functionality in cancer progression and detection using EV-based RNA/ fusion gene candidates for cancer biomarkers.

Pinctada martensii Hydrolysate Modulates the Brain Neuropeptidome and Proteome in Diabetic (db/db) Mice via the Gut-Brain Axis

Pinctada martensii hydrolysate (PMH) has been proved to have the effect of ameliorating disorders of glucose and lipid metabolism in db/db mice, but the mechanism of its hyperglycemia effect is still unclear. Bacterial communities in fecal samples from a normal control group, a diabetic control group, and a PMH-treated diabetes mellitus type 2 (T2DM) group were analyzed by 16S gene sequencing. Nano LC-MS/MS was used to analyze mice neuropeptides and proteomes. The 16S rDNA sequencing results showed that PMH modulated the structure and composition of the gut microbiota and improved the structure and composition of Firmicutes and Bacteroidetes at the phylum level and Desulfovibrionaceae and Erysipelatoclostridiaceae at the family level. Furthermore, the expressions of functional proteins of the central nervous system, immune response-related protein, and proteins related to fatty acid oxidation in the brain disrupted by an abnormal diet were recovered by PMH. PMH regulates the brain neuropeptidome and proteome and further regulates blood glucose in diabetic mice through the gut-brain axis. PMH may be used as a prebiotic agent to attenuate T2DM, and target-specific microbial species may have unique therapeutic promise for metabolic diseases.

Primary microglia cell cultures in translational research: Strengths and limitations

Microglia are the resident macrophages in the central nervous system, accounting for 10-15% of the cell mass in the brain. Next to their physiological role in development, monitoring neuronal function and the maintenance of homeostasis, microglia are crucial in the brain's immune defense. Brain injury and chronic neurological disorders are associated with neuroinflammation, in which microglia activation is a central element. Microglia acquire a wide spectrum of activation states in the diseased or injured brain, some of which are neurotoxic. The investigation of microglia (patho)physiology and therapeutic interventions targeting neuroinflammation is a substantial challenge. In addition to in vivo approaches, the application of in vitro model systems has gained significant ground and is essential to complement in vivo work. Primary microglia cultures have proved to be a useful tool. Microglia cultures have offered the opportunity to explore the mechanistic, molecular elements of microglia activation, the microglia secretome, and the efficacy of therapeutic treatments against neuroinflammation. As all model systems, primary microglia cultures have distinct strengths and limitations to be weighed when experiments are designed and when data are interpreted. Here, we set out to provide a succinct overview of the advantages and pitfalls of the use of microglia cultures, which instructs the refinement and further development of this technique to remain useful in the toolbox of microglia researchers. Since there is no conclusive therapy to combat neurotoxicity linked to neuroinflammation in acute brain injury or neurodegenerative disorders, these research tools remain essential to explore therapeutic opportunities.