Extracellular vesicle approach to major psychiatric disorders

Peripheral and central inflammation in depression: How large is the gap and can we bridge it with PET neuroimaging and neural-derived extracellular vesicles?

Major depressive disorder (MDD) presents as a multifaceted syndrome with complex pathophysiology and variable treatment responses, posing significant challenges in clinical management. Neuroinflammation is known to play pivotal mechanism in depression, linking immune responses with central nervous system (CNS) dysfunction. This review explores the interplay between peripheral and central inflammatory processes in MDD, emphasizing discrepancies in biomarker validity and specificity. While peripheral markers like cytokines have historically been investigated as proxies for neuroinflammation, their reliability remains contentious due to inconsistent findings, lack of correlation with neuroinflammatory markers, the influence of confounding variables, and the role of regulatory mechanism within the CNS. Additionally, the human brain shows a pattern of regionalized inflammation. Current methodologies for investigating neuroinflammation in humans in vivo, including neural-derived extracellular vesicles (EVs) and positron emission tomography (PET) neuroimaging using translocator protein, offer promising avenues while facing substantial limitations. We propose that future research in MDD may benefit from combined microglia-derived EV-TSPO PET neuroimaging analyses to leverage the strengths and mitigate the limitations of both individual methods.

Extracellular vesicles in mood disorders: A systematic review of human studies

Extracellular vesicles (EVs) are small, membrane-bound particles that are naturally released by nearly all cell types in the body. They serve as molecular biosignatures, reflecting the state of their cells of origin and providing a non-invasive peripheral marker of central nervous system (CNS) activity under physiological and pathological conditions. We conducted a systematic review (ID: CRD42024528824) of studies investigating the use of EVs in mood disorders within clinical populations. We screened articles indexed in PubMed, EMBASE, Scopus, ISI Web of Science, and APA PsycInfo from January 2010 to October 2024. Available research has focused on four key areas: (1) EV cargo as mechanistic and diagnostic biomarkers; (2) EV cargo as predictive or tracking biomarkers for antidepressant response; (3) EV cargo and neuroimaging correlates; and (4) EV physical properties. Most studies examined major depressive disorder (MDD), with others addressing bipolar disorder (BD), adolescent depression, postpartum depression, and late-life depression. Notably, only 35,55 % of the studies utilized brain-derived EVs. Through analyses of EV-derived miRNA, proteins, mtDNA, and metabolites, these studies have explored neural mitochondrial function, brain insulin resistance, neurogenesis, neuroinflammation, and blood-brain barrier permeability in the context of mood disorders. Some EV-derived markers demonstrated diagnostic and predictive potential. This review discusses key findings, limitations of current research, and future directions for leveraging EVs in the study of mood disorders.

L1CAM+ extracellular vesicles derived from the serum of adolescents with major depressive disorder induce depression-like phenotypes in adolescent mice

BACKGROUND

It has been reported that L1 cell adhesion molecule (L1CAM) antibody can capture neuron-derived extracellular vesicles (NDEVs) derived from peripheral blood. This antibody is significantly associated with occurrence of adult psychiatric disorders. However, the role and mechanism of L1CAM+ EVs (L1+ EVs) in adolescent with major depressive disorder (AMDD) is not well understood. This research aimed to explore the function and potential mechanism of L1+ EVs and miRNAs genes in AMDD.

METHODS

L1+ EVs derived from the serum of AMDD and healthy controls (HC) were transplanted into adolescent mice via tail vein. Their effects were explored using behavioral tests, hippocampal Nissl staining, and whole genome mRNA sequencing. MiRNAs expression in L1+ EVs was evaluated by whole-genome sequencing and qRT-PCR. Bioinformatics analysis was employed to explore the possible pathogenic molecular mechanisms of these miRNAs in AMDD.

RESULTS

Transplantation of L1+ EVs from AMDD induced depression-like behavior and hippocampal neuronal damage in adolescent mice and aberrant expression of 298 mRNA genes. The molecular signals related to MDD were enriched in the top pathways of the differentially expressed genes. Compared with HC, miR-375-3p and miR-200a-3p were upregulated in L1+ EVs from AMDD, miR-375-3p was also increased in the hippocampus of AMDD serum L1+ EVs-recipient mice. Bioinformatics analysis revealed that miR-375-3p might modulate the network of molecules associated with the MAPK pathway via protein interaction involving hippocampal differential genes Cadm2, Cacna2d1, and Casz1.

CONCLUSION

MiR-375-3p might contribute to L1+ EVs-induced AMDD. L1+ EVs miR-375-3p and miR-200a-3p could potentially serve as potential biomarkers for AMDD.

The microRNA profile of brain-derived extracellular vesicles: A promising step forward in developing pharmacodynamic biomarkers for psychiatric disorders

MicroRNAs (miRNAs) have the potential to affect drug metabolism, and some drugs affect cellular miRNA expression. miRNAs are found inside extracellular vesicles (EVs), and the profile of these EV-miRNAs can change across different diseases and disease states. Consequently, in recent years EV-miRNAs have attracted increasing attention as possible non-invasive biomarkers. For example, analyzing the miRNA expression profile of brain-derived EVs in blood may allow us to non-invasively assess miRNA dysregulation and thus to gain knowledge about the pathophysiology of psychiatric disorders and identify potential new predictive targets. We searched PubMed for all studies related to the effects of psychiatric medications on EV-miRNAs and identified 14 relevant articles. Taken together, findings indicate that certain EV-miRNAs may be targets for psychiatric medications and that antipsychotics such as olanzapine and antidepressants such as fluoxetine may alter the expression levels of particular EV-miRNAs. If confirmed and replicated, these findings may lead to the suggested miRNA profiles being used as pharmacodynamic biomarkers. However, heterogeneities and uncertainties remain regarding the role of EV-miRNAs in psychiatric disorders and their interaction with neuronal gene expression and drugs. This minireview summarizes some of the findings on the effects of psychiatric medications on EV-miRNAs and describes the potential role of EV-miRNAs as pharmacodynamic biomarkers for psychiatric disorders.

The researcher's guide to selecting biomarkers in mental health studies

Clinical mental health researchers may understandably struggle with how to incorporate biological assessments in clinical research. The options are numerous and are described in a vast and complex body of literature. Here we provide guidelines to assist mental health researchers seeking to include biological measures in their studies. Apart from a focus on behavioral outcomes as measured via interviews or questionnaires, we advocate for a focus on biological pathways in clinical trials and epidemiological studies that may help clarify pathophysiology and mechanisms of action, delineate biological subgroups of participants, mediate treatment effects, and inform personalized treatment strategies. With this paper we aim to bridge the gap between clinical and biological mental health research by (1) discussing the clinical relevance, measurement reliability, and feasibility of relevant peripheral biomarkers; (2) addressing five types of biological tissues, namely blood, saliva, urine, stool and hair; and (3) providing information on how to control sources of measurement variability.

Considering Context-Specific microRNAs in Ischemic Stroke with Three "W": Where, When, and What

MicroRNAs are short non-coding RNA molecules that function as critical regulators of various biological processes through negative regulation of gene expression post-transcriptionally. Recent studies have indicated that microRNAs are potential biomarkers for ischemic stroke. In this review, we first illustrate the pathogenesis of ischemic stroke and demonstrate the biogenesis and transportation of microRNAs from cells. We then discuss several promising microRNA biomarkers in ischemic stroke in a context-specific manner from three dimensions: biofluids selection for microRNA extraction (Where), the timing of sample collection after ischemic stroke onset (When), and the clinical application of the differential-expressed microRNAs during stroke pathophysiology (What). We show that microRNAs have the utilities in ischemic stroke diagnosis, risk stratification, subtype classification, prognosis prediction, and treatment response monitoring. However, there are also obstacles in microRNA biomarker research, and this review will discuss the possible ways to improve microRNA biomarkers. Overall, microRNAs have the potential to assist clinical treatment, and developing microRNA panels for clinical application is worthwhile.

Investigating Neuroplasticity Changes Reflected by BDNF Levels in Astrocyte-Derived Extracellular Vesicles in Patients with Depression

Purpose

To investigate the neuroplasticity hypothesis of depression by measuring brain-derived neurotrophic factor (BDNF) levels in plasma astrocyte-derived extracellular vesicles (ADEVs) and to evaluate their potential as biomarkers for depression compared with plasma BDNF levels.

Patients and Methods

Thirty-five patients with major depressive disorder (MDD) and 35 matched healthy controls (HCs) were enrolled. Plasma ADEVs were isolated using a combination of ultracentrifugation and immunoaffinity capture. Isolated ADEVs were validated using transmission electron microscopy, nanoparticle tracking analysis, and Western blotting. BDNF levels were quantified in both ADEVs and plasma. ALG-2-interacting protein X (Alix) and cluster of differentiation 81 (CD81) levels, two established extracellular vesicle markers, were measured in ADEVs.

Results

After false discovery rate correction, patients with MDD exhibited higher CD81 levels (P FDR = 0.040) and lower BDNF levels (P FDR = 0.043) in ADEVs than HCs at baseline. BDNF levels in ADEVs normalized to CD81 (P FDR = 0.002) and Alix (P FDR = 0.040) remained consistent with this finding. Following four weeks of selective serotonin reuptake inhibitor treatment (n=10), CD81 levels in ADEVs decreased (P FDR = 0.046), while BDNF levels normalized to CD81 increased (P FDR = 0.022). BDNF levels in ADEVs were more stable than in plasma. Exploratory analysis revealed no correlation between BDNF levels in ADEVs and plasma (ρ=0.117, P = 0.334).

Conclusion

This study provides human in vivo evidence supporting the neuroplasticity hypothesis of depression by demonstrating altered BDNF levels in ADEVs. ADEVs may be more suitable for developing biomarkers of depression than plasma-derived biomarkers.

Serum Extracellular Vesicle-Derived hsa-miR-2277-3p and hsa-miR-6813-3p Are Potential Biomarkers for Major Depression: A Preliminary Study

The aim of the present study was to examine the association between miRNA levels in extracellular vesicles (EVs) from serum and the severity of Major Depression (MD). Patient sera from 16 MD cases were collected at our university hospital. The miRNAs contained in EVs were extracted using a nanofiltration method, and their expression levels were analyzed using miRNA microarrays. Intergroup comparisons were performed to validate the diagnostic performance of miRNAs in EVs. Furthermore, candidate miRNAs in EVs were added to neural progenitor cells, astrocytes, and microglial cells in vitro, and the predicted target genes of the candidate miRNAs were extracted. The predicted target genes underwent enrichment analysis. The expression levels of hsa-miR-6813-3p and hsa-miR-2277-3p were significantly downregulated with increasing depression severity of MD. The pathway enrichment analysis suggests that hsa-miR-6813-3p may be involved in glucocorticoid receptor and gamma-aminobutyric acid receptor signaling. Additionally, hsa-miR-2277-3p was found to be involved in the dopaminergic neural pathway. The analysis of serum miRNAs in EVs suggests that hsa-miR-6813-3p and hsa-miR-2277-3p could serve as novel biomarkers for MD, reflecting its severity. Moreover, these miRNAs in EVs could help understand MD pathophysiology.

The role of Extracellular Genomic Materials (EGMs) in psychiatric disorders

Extracellular Genomic Materials (EGMs) are the nucleic acids secreted or released from all types of cells by endogenous or exogenous stimuli through varying mechanisms into the extracellular region and inevitably to all biological fluids. EGMs could be found as free, protein-bound, and/ or with vesicles. EGMs can potentially have immunophenotypic and/or genotypic characteristics of a cell of origin, travel to distant organs, and interact with the new microenvironment. To achieve all, EGMs might bi-directionally transit through varying membranes, including the blood-brain barrier. Such ability provides the transfer of any information related to the pathophysiological changes in psychiatric disorders in the brain to the other distant organ systems or vice versa. In this article, many aspects of EGMs have been elegantly reviewed, including their potential in diagnosis as biomarkers, application in treatment modalities, and functional effects in the pathophysiology of psychiatric disorders. The psychiatric disorders were studied under subgroups of Schizophrenia spectrum disorders, bipolar disorder, depressive disorders, and an autism spectrum disorders. EGMs provide a robust and promising tool in clinics for prognosis and diagnosis. The successful application of EGMs into treatment modalities might further provide encouraging outcomes for researchers and clinicians in psychiatric disorders.

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).