Astrocyte-Derived Exosomes in an iPSC Model of Bipolar Disorder

The role of exosomes in adult neurogenesis: implications for neurodegenerative diseases

Exosomes are cup-shaped extracellular vesicles with a lipid bilayer that is approximately 30 to 200 nm in thickness. Exosomes are widely distributed in a range of body fluids, including urine, blood, milk, and saliva. Exosomes exert biological function by transporting factors between different cells and by regulating biological pathways in recipient cells. As an important form of intercellular communication, exosomes are increasingly being investigated due to their ability to transfer bioactive molecules such as lipids, proteins, mRNAs, and microRNAs between cells, and because they can regulate physiological and pathological processes in the central nervous system. Adult neurogenesis is a multistage process by which new neurons are generated and migrate to be integrated into existing neuronal circuits. In the adult brain, neurogenesis is mainly localized in two specialized niches: the subventricular zone adjacent to the lateral ventricles and the subgranular zone of the dentate gyrus. An increasing body of evidence indicates that adult neurogenesis is tightly controlled by environmental conditions with the niches. In recent studies, exosomes released from different sources of cells were shown to play an active role in regulating neurogenesis both in vitro and in vivo, thereby participating in the progression of neurodegenerative disorders in patients and in various disease models. Here, we provide a state-of-the-art synopsis of existing research that aimed to identify the diverse components of exosome cargoes and elucidate the therapeutic potential of exosomal contents in the regulation of neurogenesis in several neurodegenerative diseases. We emphasize that exosomal cargoes could serve as a potential biomarker to monitor functional neurogenesis in adults. In addition, exosomes can also be considered as a novel therapeutic approach to treat various neurodegenerative disorders by improving endogenous neurogenesis to mitigate neuronal loss in the central nervous system.

Bipolar Disorder

This review focuses on recent advances made towards understanding the neurobiology of bipolar disorder (BD), a chronic neuropsychiatric illness characterized by altered mood and energy states. The past few years have seen the completion of the largest genetic studies by far, which have emphasized the polygenic nature of BD as well as it's connection to other psychiatric illnesses. Furthermore, the use of inducible pluripotent stem cells has rapidly expanded. These studies support previous work that implicates dysregulation of neurodevelopment, mitochondria, and calcium homeostasis, while also allowing for investigation into the underlying mechanisms of individual responsivity to lithium. Sleep and circadian rhythms have also been heavily implicated in BD, from disruptions in activity patterns to molecular abnormalities.

Extracellular vesicle approach to major psychiatric disorders

Over the last few years, extracellular vesicles (EVs) have received increasing attention as potential non-invasive diagnostic and therapeutic biomarkers for various diseases. The interest in EVs is related to their structure and content, as well as to their changing cargo in response to different stimuli. One of the potential areas of use of EVs as biomarkers is the central nervous system (CNS), in particular the brain, because EVs can cross the blood-brain barrier, exist also in peripheral tissues and have a diverse cargo. Thus, they may represent "liquid biopsies" of the CNS that can reflect brain pathophysiology without the need for invasive surgical procedures. Overall, few studies to date have examined EVs in neuropsychiatric disorders, and the present evidence appears to lack reproducibility. This situation might be due to a variety of technical obstacles related to working with EVs, such as the use of different isolation strategies, which results in non-uniform vesicular and molecular outputs. Multi-omics approaches and improvements in the standardization of isolation procedures will allow highly pure EV fractions to be obtained in which the molecular cargo, particularly microRNAs and proteins, can be identified and accurately quantified. Eventually, these advances will enable researchers to decipher disease-relevant molecular signatures of the brain-derived EVs involved in synaptic plasticity, neuronal development, neuro-immune communication, and other related pathways. This narrative review summarizes the findings of studies on EVs in major psychiatric disorders, particularly in the field of biomarkers, and discusses the respective therapeutic potential of EVs.

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.

Chronic knockdown of the tetraspanin gene CD81 in the mouse nucleus accumbens modulates anxiety and ethanol-related behaviors

CD81, a member of the tetraspanin family, plays important roles in many physiological processes, such as cell motility, attachment, and entry. Yet, CD81 functions in the brain remain unclear. In this study, we investigated the effects of CD81 knockdown, using lentiviral vectors (LV), on anxiety- and ethanol-related behaviors. For this purpose, mice were stereotaxically injected with CD81 shRNA-expressing LV into the nucleus accumbens (Nacc) and were assessed for anxiety-like behavior using the elevated plus maze (EPM) and open field (OF) tests. Alcohol's sedative effects were studied using loss-of-righting-reflex (LORR) and voluntary ethanol intake was assessed using a two-bottle choice (TBC) procedure. Results showed that mice depleted of CD81 exhibited an anxiolytic-like response in the EPM and OF tests with no effect on locomotor activity. In addition, genetic reduction of CD81 in the Nacc increased mice' sensitivity to alcohol's sedative effects in the LORR test, although plasma alcohol concentrations were unaffected. Interestingly, CD81 loss-of-function-induced anxiolysis was accompanied by a significant decrease in ethanol, but not saccharin nor quinine, intake in the TBC procedure. Finally, and following CD81 mRNA quantification, Pearson's correlations showed a significant positive relationship between accumbal CD81 mRNA with anxiety and ethanol-related behaviors. Our data indicate that CD81 is implicated in the pathogenesis of anxiety and alcoholism. Indeed the targeted disruption of CD81, with the resultant decrease in CD81 mRNA in the Nacc, converted ethanol-"preferring" mice into ethanol "non-preferring" mice. Collectively, these findings demonstrate that future CD81-targeted pharmacotherapies may be beneficial for the treatment of anxiety and alcoholism.

Ouabain inhibitor rostafuroxin attenuates dextromethorphan-induced manic potential

Dextromethorphan (DM) abuse produces mania-like symptoms in humans. ERK/Akt signaling activation involved in manic potential can be attenuated by the inhibition of ouabain-like cardiac steroids. In this study, increased phosphorylations of ERK/Akt and hyperlocomotion induced by DM (30 mg/kg, i.p./day × 7) were significantly protected by the ouabain inhibitor rostafuroxin (ROSTA), suggesting that DM induces the manic potential. ROSTA significantly attenuated DM-induced protein kinase C δ (PKCδ) phosphorylation, GluN2B (i.e., MDA receptor subunit) expression, and phospho-PKCδ/GluN2B interaction. DM instantly upregulated the nuclear factor erythroid-2-related factor 2 (Nrf2)-dependent system. However, DM reduced Nrf2 nuclear translocation, Nrf2 DNA binding activity, γ-glutamylcysteine mRNA expression, and subsequent GSH/GSSG level and enhanced oxidative parameters following 1-h of administration. ROSTA, PKCδ inhibitor rottlerin, and GluN2B inhibitor traxoprodil significantly attenuated DM-induced alterations in Nrf2-related redox parameters and locomotor activity induced by DM in wild-type mice. Importantly, in PKCδ knockout mice, DM failed to alter the above parameters. Further, ROSTA and traxoprodil also failed to enhance PKCδ depletion effect, suggesting that PKCδ is a critical target for the anti-manic potential of ROSTA or GluN2B antagonism. Our results suggest that ROSTA inhibits DM-induced manic potential by attenuating ERK/Akt activation, GluN2B/PKCδ signalings, and Nrf2-dependent system.

Human Induced Pluripotent Stem Cell-Derived Exosomes as a New Therapeutic Strategy for Various Diseases

Recently, an increasing number of studies have demonstrated that induced pluripotent stem cells (iPSCs) and iPSC-derived cells display therapeutic effects, mainly via the paracrine mechanism in addition to their transdifferentiation ability. Exosomes have emerged as an important paracrine factor for iPSCs to repair injured cells through the delivery of bioactive components. Animal reports of iPSC-derived exosomes on various disease models are increasing, such as in heart, limb, liver, skin, bone, eye and neurological disease and so forth. This review aims to summarize the therapeutic effects of iPSC-derived exosomes on various disease models and their properties, such as angiogenesis, cell proliferation and anti-apoptosis, with the hopes of improving their potential role in clinical applications and functional restoration.