Exosomes derived from miR-181-5p-modified adipose-derived mesenchymal stem cells prevent liver fibrosis via autophagy activation

Exosomes from miRNA-126-modified ADSCs promotes functional recovery after stroke in rats by improving neurogenesis and suppressing microglia activation

Although adipose derived stem cells (ADSCs) exert their therapeutic potential in ischemic stroke, the migration of ADSCs in injured area is not apparently observed after intravenous administration. ADSCs are an important source of exosomes which hold great promise as an endogenous drug delivery system for the treatment of cerebral ischemia given their ability to cross the blood-brain barrier. Here we investigated whether ADSCs-derived exosomes mediated miRNAs transfer and thus promoted neurological recovery after stroke. We first proved that miR-126 levels were reduced in patients' plasma with acute ischemic stroke and in rat plasma and brain tissue after ischemia. To test the effect of exosomal miR-126, we employed overexpression and knock-down technologies to up-regulate or inhibit miR-126 level in ADSCs and thus acquired miR-126⁺ exosomes and miR-126^- exosomes, respectively. Compared with control, systemic administration of ADSCs-derived exosomes significantly increased the expression of von Willebrand factor (an endothelia cell marker) and doublecortin (a neuroblasts marker) and improved functional recovery in stroke rats. ADSCs-derived exosomes also resulted in a decrease of neuron cell death and an increase of cell proliferation compared with control. Importantly, these outcomes were further enhanced with miR-126⁺ exosomes treatment and were significantly decreased with miR-126^- exosomes treatment, compared to naïve exosomes treatment. MiR-126⁺ exosomes also inhibited microglial activation and the expression of inflammatory factors in vivo and in vitro. Our results suggest that intravenous administration of miR-126⁺ exosomes post stroke improves functional recovery, enhances neurogenesis, inhibits neuroinflammation, and represents a novel treatment for stroke.

Extracellular Vesicles as Transmitters of Hypoxia Tolerance in Solid Cancers

Tumour hypoxia is a common feature of solid tumours that contributes to poor prognosis after treatment. This is mainly due to increased resistance of hypoxic cells to radio- and chemotherapy and the association of hypoxic cells with increased metastasis development. It is therefore not surprising that an increased hypoxic tumour fraction is associated with poor patient survival. The extent of hypoxia within a tumour is influenced by the tolerance of individual tumor cells to hypoxia, a feature that differs considerably between tumors. High numbers of hypoxic cells may, therefore, be a direct consequence of enhanced cellular capability inactivation of hypoxia tolerance mechanisms. These include HIF-1α signaling, the unfolded protein response (UPR) and autophagy to prevent hypoxia-induced cell death. Recent evidence shows hypoxia tolerance can be modulated by distant cells that have experienced episodes of hypoxia and is mediated by the systemic release of factors, such as extracellular vesicles (EV). In this review, the evidence for transfer of a hypoxia tolerance phenotype between tumour cells via EV is discussed. In particular, proteins, mRNA and microRNA enriched in EV, derived from hypoxic cells, that impact HIF-1α-, UPR-, angiogenesis- and autophagy signalling cascades are listed.

Extracellular Vesicle-Mediated Cell⁻Cell Communication in the Nervous System: Focus on Neurological Diseases

Extracellular vesicles (EVs), including exosomes, are membranous particles released by cells into the extracellular space. They are involved in cell differentiation, tissue homeostasis, and organ remodelling in virtually all tissues, including the central nervous system (CNS). They are secreted by a range of cell types and via blood reaching other cells whose functioning they can modify because they transport and deliver active molecules, such as proteins of various types and functions, lipids, DNA, and miRNAs. Since they are relatively easy to isolate, exosomes can be characterized, and their composition elucidated and manipulated by bioengineering techniques. Consequently, exosomes appear as promising theranostics elements, applicable to accurately diagnosing pathological conditions, and assessing prognosis and response to treatment in a variety of disorders. Likewise, the characteristics and manageability of exosomes make them potential candidates for delivering selected molecules, e.g., therapeutic drugs, to specific target tissues. All these possible applications are pertinent to research in neurophysiology, as well as to the study of neurological disorders, including CNS tumors, and autoimmune and neurodegenerative diseases. In this brief review, we discuss what is known about the role and potential future applications of exosomes in the nervous system and its diseases, focusing on cell–cell communication in physiology and pathology.

Long noncoding RNA HOTTIP mediates SRF expression through sponging miR-150 in hepatic stellate cells

HOXA transcript at the distal tip (HOTTIP) has been shown to be up‐regulated in a variety of cancers and is identified as an oncogenic long noncoding RNA. However, the biological role of HOTTIP in liver fibrosis is unclear. Here, we reported that HOTTIP was specifically overexpressed in activated hepatic stellate cells (HSCs). HOTTIP knockdown suppressed the activation and proliferation of HSCs. Luciferase reporter assay showed that HOTTIP and serum response factor (SRF) were targets of miR‐150. RNA binding protein immunoprecipitation assay indicated the interaction between miR‐150 and HOTTIP. Further study revealed that HOTTIP increased SRF expression as a competing endogenous RNA for miR‐150, thus prompting HSC activation. Taken together, we provide a novel HOTTIP‐miR‐150‐SRF signalling cascade in liver fibrosis.

Autophagy induces G0/G1 arrest and apoptosis in menstrual blood-derived endometrial stem cells via GSK3-β/β-catenin pathway

BACKGROUND/AIMS

Menstrual blood-derived endometrial stem cells (MenSCs) emerge as an ideal source for cell-based treatment in regenerative medicine and immunotherapy. However, the major obstacle is the low survival rate in tissues and the limited expansion number. Autophagy is an intracellular metabolic self-degradative process which plays important roles in normal cellular division and survival, and the present study aimed to explore the related mechanisms between autophagy and survival of MenSCs in vitro and in vivo.

METHODS

The MenSCs were obtained from menstrual blood procured from healthy female donors. In vitro, MenSCs were exposed to rapamycin and Earle's balanced salts solution (EBSS). We evaluated the MenSCs immunophenotypic cell cycle distribution by propidium iodide (PI) staining and cell apoptosis by Annexin V/PI staining as well as their proliferative potential by the MTT assay. We also assessed the expression of genes associated with the cell cycle and Gsk3β signaling pathway by western blot analysis. We depressed Atg5 and Gsk3β expression by short hairpin RNA (shRNA) and undertook the experiments. Moreover, the labeled MenSCs were observed and counted with DiI after transplantation into the mice via the tail vein by microscopy in vivo.

RESULTS

In vitro, rapamycin and starvation induced autophagy of MenSCs. Hyperactive autophagy significantly induced G0/G1 arrest and slightly promoted apoptosis of MenSCs. Meanwhile, autophagy could stimulate p-GSK3β expression in MenSCs. Further, knockdown GSK3β can accelerate the proliferation of MenSCs by shRNA and CHIR99021. Moreover, the shGSK3β MenSCs showed strong proliferative activity in vitro and in vivo.

CONCLUSIONS

Our results indicate that autophagy induced G0/G1 arrest and apoptosis of MenSCs via GSK3β/β-catenin pathway. Inhibiting autophagy or reduced GSK3β levels may improve survival rate in vivo, thus playing roles in MenSCs therapy.

Liver-Derived Exosomes and Their Implications in Liver Pathobiology

The liver has a wide range of physiological functions in the body, and its health is maintained by complex cross-talk among hepatic cells, including parenchymal hepatocytes and nonparenchymal cells. Exosomes, which are one method of cellular communication, are endosomal-derived small vesicles that are released by donor cells and delivered to the target cells at both short and long distances. Because exosomes carry a variety of cargoes, including proteins, mRNAs, microRNAs and other noncoding RNAs originating from donor cells, exosomes convey cellular information that enables them to potentially serve as biomarkers and therapeutics in liver diseases. Hepatocytes release exosomes to neighboring hepatocytes or nonparenchymal cells to regulate liver regeneration and repair. Nonparenchymal cells, including hepatic stellate cells, liver sinusoidal endothelial cells, and cholangiocytes, also secrete exosomes to regulate liver remodeling upon liver injury. Exosomes that are released from liver cancer cells create a favorable microenvironment for cancer growth and progression. In this review, we summarize and discuss the current findings and understanding of exosome-mediated intercellular communication in the liver, with a particular focus on the function of exosomes in both health and disease. Based on the current findings, we suggest the potential applications of exosomes as biomarkers and therapeutics for liver diseases.

Mesenchymal stem cell-derived extracellular vesicles affect disease outcomes via transfer of microRNAs

Mesenchymal stem cells (MSCs) are adult stromal cells with the capacity to differentiate into multiple types of cells. MSCs represent an attractive option in regenerative medicine due to their multifaceted abilities for tissue repair, immunosuppression, and anti-inflammation. Recent studies demonstrate that MSCs exert their effects via paracrine activity, which is at least partially mediated by extracellular vesicles (EVs). MSC-derived EVs (MSC-EVs) could mimic the function of parental MSCs by transferring their components such as DNA, proteins/peptides, mRNA, microRNA (miRNA), lipids, and organelles to recipient cells. In this review, we aim to summarize the mechanism and role of miRNA transfer in mediating the effects of MSC-EVs in the models of human diseases. The first three sections of the review discuss the sorting of miRNAs into EVs, uptake of EVs by target cells, and functional transfer of miRNAs via EVs. Then, we describe the composition of miRNAs in MSC-EVs. Next, we provide the existing evidence that MSC-EVs affect the outcomes of renal, liver, heart, and brain diseases by transferring their miRNA contents. In conclusion, EV-mediated miRNA transfer plays an important role in disease-modulating capacity of MSCs.

Kir6.2 Deficiency Promotes Mesencephalic Neural Precursor Cell Differentiation via Regulating miR-133b/GDNF in a Parkinson's Disease Mouse Model

The loss of dopaminergic (DA) neurons in the substantia nigra (SN) is a major feature in the pathology of Parkinson's disease (PD). Using neural stem or progenitor cells (NSC/NPCs), the prospect of replacing the missing or damaged DA neurons is very attractive for PD therapy. However, little is known about the endogenous mechanisms and molecular pathways regulating the NSC/NPC proliferation and differentiation in the development of PD. Herein, using Kir6.2 knockout (Kir6.2-/-) mice, we observed that genetic deficiency of Kir6.2 exacerbated the loss of SN DA neurons relatively early in a chronic MPTP/probenecid (MPTP/p) injection course, but rescued the damage of neurons 7 days after the last MPTP/p injection. Meanwhile, we found that Kir6.2 knockout predominantly increased the differentiation of nuclear receptor-related 1 (Nurr1+) precursors to DA neurons, indicating that Kir6.2 deficiency could activate an endogenous self-repair process. Furthermore, we demonstrated in vivo and in vitro that lack of Kir6.2 promoted neuronal differentiation via inhibiting the downregulation of glia cell line-derived neurotrophic factor (GDNF), which negatively related to the level of microRNA-133b. Notably, we revealed that Gdnf is a target gene of miR-133b and transfection of miR-133b could attenuate the enhancement of neural precursor differentiation induced by Kir6.2 deficiency. Collectively, we clarify for the first time that Kir6.2/K-ATP channel functions as a novel endogenous negative regulator of NPC differentiation, and provide a promising neuroprotective target for PD therapeutics.

Possibility of Exosome-Based Therapeutics and Challenges in Production of Exosomes Eligible for Therapeutic Application

Exosomes are cell-derived vesicles with a diameter 30-120 nm. Exosomes contain endogenous proteins and nucleic acids; delivery of these molecules to exosome-recipient cells causes biological effects. Exosomes derived from some types of cells such as mesenchymal stem cells and dendritic cells have therapeutic potential and may be biocompatible and efficient agents against various disorders such as organ injury. However, there are many challenges for the development of exosome-based therapeutics. In particular, producing exosomal formulations is the major barrier for therapeutic application because of their heterogeneity and low productivity. Development and optimization of producing methods, including methods for isolation and storage of exosome formulations, are required for realizing exosome-based therapeutics. In addition, improvement of therapeutic potential and delivery efficiency of exosomes are important for their therapeutic application. In this review, we summarize current knowledge about therapeutic application of exosomes and discuss some challenges in their successful use.

Curcumol induces RIPK1/RIPK3 complex-dependent necroptosis via JNK1/2-ROS signaling in hepatic stellate cells

It is generally recognized that hepatic fibrogenesis is an end result of increased extracellular matrix (ECM) production from the activation and proliferation of hepatic stellate cells (HSCs). An in-depth understanding of the mechanisms of HSC necroptosis might provide a new therapeutic strategy for prevention and treatment of hepatic fibrosis. In this study, we attempted to investigate the effect of curcumol on necroptosis in HSCs, and further to explore the molecular mechanisms. We found that curcumol ameliorated the carbon tetrachloride (CCl₄)-induced mice liver fibrosis and suppressed HSC proliferation and activation, which was associated with regulating HSC necroptosis through increasing the phosphorylation of receptor-interacting protein kinase 1 (RIPK1), receptor-interacting protein kinase 3 (RIPK3). Moreover, curcumol promoted the migration of RIPK1 and RIPK3 into necrosome in HSCs. RIPK3 depletion impaired the anti-fibrotic effect of curcumol. Importantly, we showed that curcumol-induced RIPK3 up-regulation significantly increased mitochondrial reactive oxygen species (ROS) production and mitochondrial depolarization. ROS scavenger, N-acetyl-L-cysteine (NAC) impaired RIPK3-mediated necroptosis. In addition, our study also identified that the activation of c-Jun N-terminal kinase1/2 (JNK1/2) was regulated by RIPK3, which mediated curcumol-induced ROS production. Down-regulation of RIPK3 expression, using siRIPK3, markedly abrogated JNK1/2 expression. The use of specific JNK1/2 inhibitor (SP600125) resulted in the suppression of curcumol-induced ROS production and mitochondrial depolarization, which in turn, contributed to the inhibition of curcumol-triggered necroptosis. In summary, our study results reveal the molecular mechanism of curcumol-induced HSC necroptosis, and suggest a potential clinical use of curcumol-targeted RIPK1/RIPK3 complex-dependent necroptosis via JNK1/2-ROS signaling for the treatment of hepatic fibrosis.

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Curcumol exerted anti-hepatic fibrogenesis effects in CCl₄-treated mice.

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Curcumol inhibited the activation of hepatic stellate cell in vitro.

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Curcumol promoted the generation of RIPK1/RIPK3-complex to induce hepatic stellate cell necroptosis.

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Curcumol modulated RIPK3/JNK/ROS signaling axis.

Mechanism of autophagy in liver fibrosis

Autophagy is an evolutionarily conserved lysosome-dependent catabolic process which degrades cell components, including proteins and lipids, in order to recycle substrates to exert optimally and adapt to tough circumstances. It is an important mechanism for the body to maintain the homeostasis of the internal environment. Liver fibrosis refers to the excessive proliferation and abnormal deposition of extracellular matrix components in the liver tissue, resulting in pathological changes in liver structure and function abnormalities, which is seen in chronic liver diseases of many different causes. In this article, we summarizes the role of autophagy in hepatic fibrosis as well as the relevant signaling pathways to reveal the mechanism of autophagy in hepatic fibrosis.

MSC exosome works through a protein-based mechanism of action

Mesenchymal stem cell (MSC) exosome specifically defines the 50–200 nm vesicles that are secreted into the extracellular space when multivesicular bodies in the MSC fuse with the plasma membrane. However, the exosome is just one of several 50–200 nm extracellular vesicles (EVs) known to be secreted by cells. Nevertheless, the term ‘MSC exosome’ is often used to describe populations of 50–200 nm EVs that are prepared from culture medium conditioned by MSCs on the basis that these populations collectively exhibited typical exosome-associated proteins such as endosomal proteins, TSG101 and Alix, and tetraspanin proteins, CD9, CD63 and CD81. They also carry a rich diverse RNA cargo. MSC exosomes are increasingly implicated as the mediator of many of the MSC-associated therapeutic potencies. They elicit therapeutic activity by delivering their cargo of potentially therapeutic proteins and RNAs to the recipient cells. The therapeutic potency of MSC exosomes is usually rationalized on the presence of a biologically relevant protein or RNA in the MSC exosome. In the present paper, we expanded this rationale beyond a physical presence to include biologically relevant concentration, biochemical functionality and the potential to elicit an appropriate timely biochemical response. Based on these, we propose that MSC exosomes most probably work through the protein rather than the RNA.

Taking advantage of the potential of mesenchymal stromal cells in liver regeneration: Cells and extracellular vesicles as therapeutic strategies

Cell-based therapies for acute and chronic liver diseases are under continuous progress. Mesenchymal stem/stromal cells (MSCs) are multipotent cells able to migrate selectively to damaged tissue and contribute to its healing and regeneration. The MSC pro-regenerative effect occurs due to their immunomodulatory capacity and their ability to produce factors that promote cell protection and survival. Likewise, it has been observed that part of their paracrine effect is mediated by MSC-derived extracellular vesicles (EVs). EVs contain proteins, lipids and nucleic acids (DNA, mRNA, miRNA, lncRNA) from the cell of origin, allowing for intercellular communication. Recently, different studies have demonstrated that MSC-derived EVs could reproduce, at least in part, the biological effects obtained by MSC-based therapies. Moreover, due to EVs' stability for long periods of time and easy isolation methods they have become a therapeutic option to MSCs treatments. This review summarizes the latest results achieved in clinical trials using MSCs as cell therapy for liver regeneration, the role of EVs in liver physiopathology and the potential of MSCderived EVs as intercellular mediators and therapeutic tools in liver diseases.

miR-93-5p-Containing Exosomes Treatment Attenuates Acute Myocardial Infarction-Induced Myocardial Damage

Adipose-derived stromal cells (ADSCs) have been considered as an attractive therapeutic tool. Accumulating evidence indicates that the healing effects of ADSCs are mainly related to paracrine action rather than transdifferentiation. Data show that the expression of miR-93-5p has a cardio-protective effect after acute myocardial infarction (AMI). To identify whether miR-93-5p-encapsulating exosomes that form ADSCs have a better cardio-protective effect, we investigated the inflammatory factors and miR-30d-5p expression in clinical levels. A rat model of AMI and an in vitro model of hypoxic H9c2 cells were established to study the protective mechanism of miR-93-5p in ischemia-induced cardiac injury. The results show that the expression of inflammatory cytokines and miR-93-5p were increased following AMI in both patients and animal models. Moreover, treatment with ADSC-derived miR-93-5p-containing exosomes has a greater protective effect on infarction-induced myocardial damage than simple exosome processing. Furthermore, in vitro experiments confirmed that the expression of miR-93-5p can significantly suppress hypoxia-induced autophagy and inflammatory cytokine expression by targeting Atg7 and Toll-like receptor 4 (TLR4), respectively, and was confirmed with Atg7 or TLR4 overexpression. The results also show that autophagy activation can promote inflammatory cytokine expression indirectly. Taken together, these results suggest that the miR-93-5p-enhanced ADSC-derived exosomes prevent cardiac injury by inhibiting autophagy and the inflammatory response.

Therapeutic effects of serum extracellular vesicles in liver fibrosis

The lack of approved therapies for hepatic fibrosis seriously limits medical management of patients with chronic liver disease. Since extracellular vesicles (EVs) function as conduits for intercellular molecular transfer, we investigated if EVs from healthy individuals have anti-fibrotic properties. Hepatic fibrogenesis or fibrosis in carbon tetrachloride (CCl₄)- or thioacetic acid-induced liver injury models in male or female mice were suppressed by serum EVs from normal mice (EVN) but not from fibrotic mice (EVF). CCl₄-treated mice undergoing EVN therapy also exhibited reduced levels of hepatocyte death, inflammatory infiltration, circulating AST/ALT levels and hepatic or circulating pro-inflammatory cytokines. Hepatic histology, liver function tests or circulating proinflammatory cytokine levels were unaltered in control mice receiving EVN. As determined using PKH26-labelled EVN, principal target cells included hepatic stellate cells (HSC; a normally quiescent fibroblastic cell that undergoes injury-induced activation and produces fibrosis during chronic injury) or hepatocytes which showed increased EVN binding after, respectively, activation or exposure to CCl₄. In vitro, EVN decreased proliferation and fibrosis-associated molecule expression in activated HSC, while reversing the inhibitory effects of CCl₄ or ethanol on hepatocyte proliferation. In mice, microRNA-34c, -151-3p, -483-5p, -532-5p and -687 were more highly expressed in EVN than EVF and mimics of these microRNAs (miRs) individually suppressed fibrogenic gene expression in activated HSC. A role for these miRs in contributing to EVN actions was shown by the ability of their corresponding antagomirs to individually and/or collectively block the therapeutic effects of EVN on activated HSC or injured hepatocytes. Similarly, the activated phenotype of human LX-2 HSC was attenuated by serum EVs from healthy human subjects and contained higher miR-34c, -151-3p, -483-5p or -532-5p than EVs from hepatic fibrosis patients. In conclusion, serum EVs from normal healthy individuals are inherently anti-fibrogenic and anti-fibrotic, and contain microRNAs that have therapeutic actions in activated HSC or injured hepatocytes.

Abbreviations: ALT: alanine aminotransferase; AST: aspartate aminotransferase; CCl₄: carbon tetrachloride; CCN2: connective tissue growth factor; E: eosin; EGFP: enhanced green fluorescent protein; EVs: extracellular vesicles; EVF: serum EVs from mice with experimental hepatic fibrosis; EVN: serum EVs from normal mice; H: hematoxylin; HSC: hepatic stellate cell; IHC: immunohistochemistry; IL: interleukin; MCP-1: monocyte chemotactic protein-1; miR: microRNA; mRNA: messenger RNA; NTA: nanoparticle tracking analysis; PCNA: proliferating cell nuclear antigen; qRT-PCR: quantitative real-time polymerase chain reaction; SDS-PAGE: sodium dodecyl sulphate – polyacrylamide gel electrophoresis; αSMA: alpha smooth muscle actin; TAA: thioacetic acid; TG: transgenic; TGF-β: transforming growth factor beta; TEM: transmission electron microscopy; TNFα: tumour necrosis factor alpha.

Extracellular vesicles as potential biomarkers for alcohol- and drug-induced liver injury and their therapeutic applications

Extracellular vesicles (EVs) are small membranous vesicles originating from various cells and tissues, including the liver parenchymal hepatocytes and nonparenchymal cells such as Kupffer and stellate cells. Recently, the pathophysiological role of EVs, such as exosomes and microvesicles, has been increasingly recognized based on their properties of intercellular communications. These EVs travel through the circulating blood and interact with specific cells and then deliver their cargos such as nucleic acids and proteins into recipient cells. In addition, based on their stabilities, circulating EVs from body fluids such as blood, cerebrospinal fluid, urine, saliva, semen, breast milk and amniotic fluids are being studied as a valuable source of potential biomarkers for providing information about the physiological status of original cells or tissues. In addition, EVs are considered potential therapeutic agents due to their ability for intercellular communications between different cell types within the liver and between various organs through transfer of their cargos. In this review, we have briefly described recent advances in the characteristics and pathophysiological roles of EVs in alcoholic liver disease (ALD) or drug-induced liver injury (DILI) and discuss their advantages in the discovery of potential biomarkers and therapeutic agents.

Insights into the key roles of epigenetics in matrix macromolecules-associated wound healing

Extracellular matrix (ECM) is a dynamic network of macromolecules, playing a regulatory role in cell functions, tissue regeneration and remodeling. Wound healing is a tissue repair process necessary for the maintenance of the functionality of tissues and organs. This highly orchestrated process is divided into four temporally overlapping phases, including hemostasis, inflammation, proliferation and tissue remodeling. The dynamic interplay between ECM and resident cells exerts its critical role in many aspects of wound healing, including cell proliferation, migration, differentiation, survival, matrix degradation and biosynthesis. Several epigenetic regulatory factors, such as the endogenous non-coding microRNAs (miRNAs), are the drivers of the wound healing response. microRNAs have pivotal roles in regulating ECM composition during wound healing and dermal regeneration. Their expression is associated with the distinct phases of wound healing and they serve as target biomarkers and targets for systematic regulation of wound repair. In this article we critically present the importance of epigenetics with particular emphasis on miRNAs regulating ECM components (i.e. glycoproteins, proteoglycans and matrix proteases) that are key players in wound healing. The clinical relevance of miRNA targeting as well as the delivery strategies designed for clinical applications are also presented and discussed.

MiR-181b regulates autophagy in a model of Parkinson's disease by targeting the PTEN/Akt/mTOR signaling pathway

OBJECTIVE

Parkinson's disease (PD) is the second most common neurodegenerative disease. Recent studies have shown that dysregulation of microRNA plays an important role in PD, and defects in autophagy are also critically associated with mechanisms underlying PD. We aim to investigate the effect of miR-181b on autophagy, particularly the involvement of miR-181b in the regulation of the phosphatase and tensin homolog (PTEN)/protein kinase B (Akt)/mammalian target of rapamycin (mTOR) pathway and neuronal autophagy in a 1-methyl-4- phenylpyridinium iodide(MPP⁺)-induced cellular model of Parkinson's disease.

MATERIALS AND METHODS

We used MPP⁺ as a tool to construct the PD cell model, using miR-181b mimics or inhibitors to regulate the expression of miR-181b. PC12 cell viability was detected by MTT. The expression of miR-181b was determined by quantitative real-time PCR analysis. The expression of autophagy protein markers (LC3II) and PTEN/Akt/mTOR signaling proteins (PTEN, p-AKT,p-mTOR and p-p70S6K) were determined by Western blotting analysis.

RESULTS

The expression of miR-181b and autophagy-related proteins was gradually decreased with increasing MPP⁺ content. Overexpression of miR-181b significantly decreased the LC3II/GAPDH ratio and increased cell viability compared to the MPP⁺ treated group, whereas inhibition of miR-181b attenuated these effects. In addition, we observed that PTEN expression was reduced by miR-181b mimics and induced by its inhibitors in MPP⁺-treated PC12 cells. Additionally, the indicators of AKT/mTOR signaling, phosphorylated (active) AKT, mTOR and p70S6K were both increased by miR-181b mimics and decreased by its inhibitors.

CONCLUSIONS

Our results suggest that miR-181b regulates autophagy by targeting the PTEN/Akt/mTOR signaling pathway, thereby affecting cell viability in PD.

Activation of autophagy is required for Oroxylin A to alleviate carbon tetrachloride-induced liver fibrosis and hepatic stellate cell activation

Liver fibrosis is a reversible pathophysiological process correlated with intense repair and cicatrization mechanisms, and its end-stage cirrhosis is responsible for high morbidity and mortality worldwide. Interestingly, the use of natural products as a realistic option for the treatment of liver fibrosis has broadly been accepted. Oroxylin A, a safe and natural product, shows a wide range of pharmacological activities such as anti-inflammatory, anti-oxidant, and anti-tumor properties. However, the effects of Oroxylin A on liver fibrosis remain poorly understood. In the present study, we sought to determine the effect of Oroxylin A on carbon tetrachloride (CCl₄)-induced liver fibrosis, and to further examine the molecular mechanisms. We found that treatment with Oroxylin A markedly decreased the level of liver injury markers, alkaline phosphatase (ALP), aspartate aminotransferase (AST), and alanine aminotransferase (ALT), in a dose dependent manner. Moreover, Oroxylin A treatment remarkably inhibited extracellular matrix (ECM) deposition, and significantly down-regulated the mRNA and protein expression of liver fibrosis markers including α1(I)collagen, fibronectin, alpha-smooth muscle actin (α-SMA), PDGF-βR, and TGF-βR1 in CCl₄-induced murine model of liver fibrosis. Furthermore, experimental results in vitro showed that Oroxylin A treatment reduced the mRNA and protein expression of HSC activation markers, α-SMA, desmin, α1 (I) collagen, fibronectin, TGF-β, and TNF-α, in a dose dependent manner. Attractively, Oroxylin A treatment also markedly up-regulated the expression of autophagy makers, LC3-B, Atg3, Atg4, Atg5, Beclin1/Atg6, Atg7, Atg9, ATG12, and Atg14, and apparently reduced the expression of autophagy substrate p62 in both CCl₄-induced murine model of liver fibrosis and PDGF-BB-treated HSCs. Importantly, inhibition of autophagy by specific inhibitor 3-methyladenine (3-MA) completely abolished Oroxylin A-induced anti-fibrosis effect, indicating that activation of autophagy was required for Oroxylin A to alleviate liver fibrosis. Overall, these results provide novel implications to reveal the molecular mechanism of Oroxylin A-induced anti-fibrosis properties, by which points to the possibility of using Oroxylin A for the treatment of liver fibrosis.

Exosomal biomarkers in Down syndrome and Alzheimer's disease

Every person with Down syndrome (DS) has the characteristic features of Alzheimer's disease (AD) neuropathology in their brain by the age of forty, and most go on to develop AD dementia. Since people with DS show highly variable levels of baseline function, it is often difficult to identify early signs of dementia in this population. The discovery of blood biomarkers predictive of dementia onset and/or progression in DS is critical for developing effective clinical diagnostics. Our recent studies show that neuron-derived exosomes, which are small extracellular vesicles secreted by most cells in the body, contain elevated levels of amyloid-beta peptides and phosphorylated-Tau that could indicate a preclinical AD phase in people with DS starting in childhood. We also found that the relative levels of these biomarkers were altered following dementia onset. Exosome release and signaling are dependent on cellular redox homeostasis as well as on inflammatory processes, and exosomes may be involved in the immune response, suggesting a dual role as both triggers of inflammation in the brain and propagators of inflammatory signals between brain regions. Based on recently reported connections between inflammatory processes and exosome release, the elevated neuroinflammatory state observed in people with DS may affect exosomal AD biomarkers. Herein, we discuss findings from studies of people with DS, people with DS and AD (DS-AD), and mouse models of DS showing new connections between neuroinflammatory pathways, oxidative stress, exosomes, and exosome-mediated signaling, which may inform future AD diagnostics, preventions, and treatments in the DS population as well as in the general population.

Non-coding RNAs in Mesenchymal Stem Cell-Derived Extracellular Vesicles: Deciphering Regulatory Roles in Stem Cell Potency, Inflammatory Resolve, and Tissue Regeneration

Extracellular vesicles (EVs) are heterogeneous populations of nano- and micro-sized vesicles secreted by various cell types. There is mounting evidence that EVs have widespread roles in transporting proteins, lipids, and nucleic acids between cells and serve as mediators of intercellular communication. EVs secreted from stem cells could function as paracrine factors, and appear to mimic and recapitulate several features of their secreting cells. EV-mediated transport of regulatory RNAs provides a novel source of trans-regulation between cells. As such, stem cells have evolved unique forms of paracrine mechanisms for recapitulating their potencies with specialized functions by transporting non-coding RNAs (ncRNAs) via EVs. This includes the dissemination of stem cell-derived EV-ncRNAs and their regulatory effects elicited in differentiation, self-renewal, pluripotency, and the induction of reparative programs. Here, we summarize and discuss the therapeutic effects of mesenchymal stem cell-derived EV-ncRNAs in the induction of intrinsic regenerative programs elicited through regulating several mechanisms. Among them, most noticeable are the EV-mediated enrichment of ncRNAs at the injury sites contributing the regulation of matrix remodeling, epithelial mesenchymal transitions, and attraction of fibroblasts. Additionally, we emphasize EV-mediated transmission of anti-inflammatory RNAs from stem cells to injury site that potentially orchestrate the resolution of the inflammatory responses and immune alleviation to better facilitate healing processes. Collectively, this knowledge indicates a high value and potential of EV-mediated RNA-based therapeutic approaches in regenerative medicine.

Mesenchymal Stem Cell Secretome: Toward Cell-Free Therapeutic Strategies in Regenerative Medicine

Earlier research primarily attributed the effects of mesenchymal stem cell (MSC) therapies to their capacity for local engrafting and differentiating into multiple tissue types. However, recent studies have revealed that implanted cells do not survive for long, and that the benefits of MSC therapy could be due to the vast array of bioactive factors they produce, which play an important role in the regulation of key biologic processes. Secretome derivatives, such as conditioned media or exosomes, may present considerable advantages over cells for manufacturing, storage, handling, product shelf life and their potential as a ready-to-go biologic product. Nevertheless, regulatory requirements for manufacturing and quality control will be necessary to establish the safety and efficacy profile of these products. Among MSCs, human uterine cervical stem cells (hUCESCs) may be a good candidate for obtaining secretome-derived products. hUCESCs are obtained by Pap cervical smear, which is a less invasive and painful method than those used for obtaining other MSCs (for example, from bone marrow or adipose tissue). Moreover, due to easy isolation and a high proliferative rate, it is possible to obtain large amounts of hUCESCs or secretome-derived products for research and clinical use.

Exosomal HSP60: a potentially useful biomarker for diagnosis, assessing prognosis, and monitoring response to treatment

INTRODUCTION

Cell-to-cell communication is imperative for life and it is mediated by sending and receiving information via the secretion and subsequent receptor-mediated detection of biological molecules. Exosomes (EXs) secreted from cells to the extracellular environment play an important role in intercellular communication in normal and pathological conditions. Areas covered: New evidence indicates that tumor cells-derived EXs contribute to cancer progression through the modulation of tumor microenvironment. The exosomal heat shock protein 60 (HSP60) is very likely a key player in intercellular cross-talk, particularly during the progress of diseases, such as cancer. Many studies have focused on the extracellular roles played by HSP60 that pertain to cancer development and immune system stimulation. Our experimental data in vitro and in vivo demonstrated that HSP60 occurs on the surface of EXs secreted by tumour cells. Expert commentary: Exosomal HSP60 has great potential for clinical applications, as a 'liquid biopsy', including its use as biomarker for diagnostics, assessing prognosis, and monitoring disease progression and response to treatment, particularly in cancer.