Extracellular vesicle therapeutics for liver disease

Exosomes as therapeutic vehicles in liver diseases

The diagnosis and treatment of various liver diseases have progressed greatly over the years, but clinical outcomes are still not satisfying. New research on the mechanisms and application thereof may effectuate positive changes. Exosomes are membrane-derived nanovesicles ranging in size from 40 to 160 nm and are released by a diversity of cells. They contain a variety of cargo, including lipids, proteins, coding RNAs, and noncoding RNAs. Recent studies have recognized exosomes as intercellular communication agents, which play important roles in physiological or biological processes in acute or chronic liver disorders by horizontal transferring of genetic bioinformation from donor cells to neighboring or distal target cells. In the hope that exosomes can potentially be used as vehicles for clinical intervention, this review aims to focus on the roles of exosomes and their cargo in the field of various liver disorders, including virus-related liver diseases, alcoholic liver diseases (ALD), nonalcoholic fatty liver diseases (NAFLD), and liver cancer. In addition, many studies have indicated that mesenchymal stem cell (MSC)-derived exosomes or engineered MSC-derived exosomes can also exert hepatoprotection, antioxidation, or enhance drug sensitivity on corresponding liver diseases with the advantage of low immunogenicity and high biocompatibility. Overall, exosomes are expected to serve as an important therapeutic tool for various liver diseases. However, there are still many problems that need to be resolved by further research and a greater body of evidence before exosomes are ready for clinical application.

Mesenchymal Stem Cells-Derived Exosomes as Dexamethasone Delivery Vehicles for Autoimmune Hepatitis Therapy

Exosomes (Exos) are nanosized vesicles (around 100 nm) that recently serve as a promising drug carrier with high biocompatibility and low immunogenicity. Previous studies showed that Exos secreted from mesenchymal stem cells (MSCs) provide protection for concanavalin A (Con A)-induced liver injury. In this study, the protective effect of Exos is confirmed, and dexamethasone (DEX)-incorporated Exos named Exo@DEX are prepared. It is then investigated whether Exo@DEX can function more efficiently compared to free drugs and naive Exos in a Con A-induced autoimmune hepatitis (AIH) mouse model. The results show that Exo@DEX efficiently improves the accumulation of DEX in AIH in the liver. These data suggest that Exo@DEX is a promising drug carrier for AIH and could have applications in other diseases.

Oxysterols and mesenchymal stem cell biology

Mesenchymal stem cells have the ability to differentiate into several cell types when exposed to determined substances, including oxysterols. Oxysterols are cholesterol products derived from its auto-oxidation by reactive species or from enzymatic action. They are present in the body in low quantities under physiological conditions and exhibit several physiological and pharmacological actions according to both the types of oxysterol and tissue. Some of them are cytotoxic while others have been shown to promote cell differentiation through the action on several different receptors, such as nuclear LXR receptors and Smoothened receptor ligands. Here, we review the main pathways by which oxysterols have been associated with cell differentiation and death of mesenchymal stem cells.

The development of mesenchymal stem cell therapy in the present, and the perspective of cell-free therapy in the future

Cirrhosis is a chronic condition that can lead to liver failure. Currently, the viable option for decreasing mortality is liver transplantation. However, transplant surgery is highly invasive. Therefore, cell-based therapy has been developed as an alternative. Based on promising findings from preclinical research, some new trials have been registered. One of them was autologous bone marrow cell infusion therapy and found that ameliorating liver fibrosis activated liver regeneration. Now, majority of trials focus on low-immunogenicity mesenchymal stem cells (MSCs) appropriate for allogeneic administration. However, despite about 20 years of research, only a limited number of cell-based therapies have entered routine practice. Furthermore, potential shortcomings of cell-based therapy include a limit on the number of cells, which may be administered, as well as their failure to infiltrate target organs. On the other hand, these research show that MSCs act as "conducting cells" and regulate host cells including macrophages via extracellular vesicles (EVs) or exosome signals, leading to ameliorate liver fibrosis and promote regeneration. Therefore, the concept of cell-free therapy, which makes use of cell-derived EVs or exosomes, is attracting attention. Cell-free therapies may be safely administered in large doses and are able to infiltrate target organs. However, development of cell-free therapy exhibits its own set of challenges and such therapy may not be completely curative in the context of liver disease. This review describes the history of cell-based therapy research and recent advances in cell-free therapy, as well as discussing the need for more effective therapies.

Extracellular vesicles for treatment of solid organ ischemia-reperfusion injury

As the incidence of ischemia-reperfusion (I-R) injury has substantially increased, there is a pressing need to develop effective strategies to treat this global health issue. I-R injury can affect all organs and is associated with high morbidity and mortality rates. Pathological settings such as myocardial infarction, stroke, hemorrhagic shock, and solid organ transplant are particularly prone to cause I-R injury. Ischemia (hypoxia) and/or reperfusion (reoxygenation) induces various forms of cellular and structural damage. A major cause of damage is local inflammatory responses, which may spread to produce more advanced systemic inflammation. Management of I-R injury relies primarily on supportive measures, as specific treatment strategies are lacking. Extracellular vesicles (EVs) are cell-secreted nano-scale structures containing various biomolecules involved in cell communication and multiple physiological processes. EVs derived from certain cell types have been shown to exhibit anti-inflammatory, antioxidant, and angiogenic properties. This review provides an overview of EV-based therapeutics for I-R injury in kidneys, liver, heart, lungs, and brain. Additionally, the mechanisms by which EVs protect against I-R injury are discussed. Promising preclinical findings highlight the potential clinical use of EVs for I-R injury.

Extracellular Vesicles as Drug Delivery Systems in Cancer

Within tumors, Cancer Stem Cell (CSC) subpopulation has an important role in maintaining growth and dissemination while preserving high resistance against current treatments. It has been shown that, when CSCs are eliminated, the surrounding Differentiated Cancer Cells (DCCs) may reverse their phenotype and gain CSC-like features to preserve tumor progression and ensure tumor survival. This strongly suggests the existence of paracrine communication within tumor cells. It is evidenced that the molecular crosstalk is at least partly mediated by Extracellular Vesicles (EVs), which are cell-derived membranous nanoparticles that contain and transport complex molecules that can affect and modify the biological behavior of distal cells and their molecular background. This ability of directional transport of small molecules prospects EVs as natural Drug Delivery Systems (DDS). EVs present inherent homing abilities and are less immunogenic than synthetic nanoparticles, in general. Currently, strong efforts are focused into the development and improvement of EV-based DDS. Even though EV-DDS have already reached early phases in clinical trials, their clinical application is still far from commercialization since protocols for EVs loading, modification and isolation need to be standardized for large-scale production. Here, we summarized recent knowledge regarding the use of EVs as natural DDS against CSCs and cancer resistance.

Brain metastases-derived extracellular vesicles induce binding and aggregation of low-density lipoprotein

BACKGROUND

Cancer cell-derived extracellular vesicles (EVs) have previously been shown to contribute to pre-metastatic niche formation. Specifically, aggressive tumors secrete pro-metastatic EVs that travel in the circulation to distant organs to modulate the microenvironment for future metastatic spread. Previous studies have focused on the interface between pro-metastatic EVs and epithelial/endothelial cells in the pre-metastatic niche. However, EV interactions with circulating components such as low-density lipoprotein (LDL) have been overlooked.

RESULTS

This study demonstrates that EVs derived from brain metastases cells (Br-EVs) and corresponding regular cancer cells (Reg-EVs) display different interactions with LDL. Specifically, Br-EVs trigger LDL aggregation, and the presence of LDL accelerates Br-EV uptake by monocytes, which are key components in the brain metastatic niche.

CONCLUSIONS

Collectively, these data are the first to demonstrate that pro-metastatic EVs display distinct interactions with LDL, which impacts monocyte internalization of EVs.

Extracellular Vesicles in the Development of Cancer Therapeutics

Extracellular vesicles (EVs) are small lipid bilayer-delimited nanoparticles released from all types of cells examined thus far. Several groups of EVs, including exosomes, microvesicles, and apoptotic bodies, have been identified according to their size and biogenesis. With extensive investigations on EVs over the last decade, it is now recognized that EVs play a pleiotropic role in various physiological processes as well as pathological conditions through mediating intercellular communication. Most notably, EVs have been shown to be involved in cancer initiation and progression and EV signaling in cancer are viewed as potential therapeutic targets. Furthermore, as membrane nanoparticles, EVs are natural products with some of them, such as tumor exosomes, possessing tumor homing propensity, thus leading to strategies utilizing EVs as drug carriers to effectively deliver cancer therapeutics. In this review, we summarize recent reports on exploring EVs signaling as potential therapeutic targets in cancer as well as on developing EVs as therapeutic delivery carriers for cancer therapy. Findings from preclinical studies are primarily discussed, with early phase clinical trials reviewed. We hope to provide readers updated information on the development of EVs as cancer therapeutic targets or therapeutic carriers.

Glycan Node Analysis of Plasma-Derived Extracellular Vesicles

Blood plasma is a readily accessible source of extracellular vesicles (EVs), i.e., cell-secreted nanosized carriers that contain various biomolecules, including glycans. Previous studies have demonstrated that glycans play a major role in physiological and pathological processes, and certain plasma glycans have been associated with disease conditions. However, glycome studies have been limited by a lack of analytical techniques with the throughput capacity necessary to study hundreds of clinical samples. This study is the first to characterize the EV plasma glycome based on all major glycan classes. The results based on glycan node analysis revealed, as expected, that plasma-derived EVs have distinct glycan features from donor-matched whole plasma. Specifically, glycan nodes corresponding to those observed in chondroitin sulfate, dermatan sulfate, type I keratan sulfate, and type II keratan sulfate were enriched on EVs. The identification of specific differences in glycan features in plasma vs. plasma-derived EVs is relevant for understanding the physiological role of EVs and as a reference for future diagnostic studies. Additionally, the results indicate that EV glycan nodes do not substantially differ among a small set of healthy donors. These results lay the framework for the further evaluation of all EV glycan classes as diagnostic markers, therapeutic targets, and biologically active components in health and disease.

Cancer therapy based on extracellular vesicles as drug delivery vehicles

Extracellular vesicles (EVs) are lipid bilayer vesicles of nanometric size secreted by cells to communicate with other cells, either nearby or remotely. Their physicochemical properties make them a promising nanomedicine for drug transport and release in cancer therapy. In this review, we present the different types and biogenesis of EVs and highlight the importance of adequately selecting the cell of origin in cancer therapy. Furthermore, the main methodologies followed for the isolation of EVs and drug loading, as well as the modification and functionalization of these vesicles to generate EV-based nanocarriers are discussed. Finally, we review some of the main studies using drug-loaded exosomes in tumor therapy both in in vitro and in vivo models (even in resistant tumors). These investigations show promising results, achieving significant improvement in the antitumor effect of drugs in most cases. However, the number of clinical trials and patents based on these nanoformulations is still low, thus further research is still warranted in this area.

Lipoprotein-based drug delivery

Lipoproteins (LPs) are circulating heterogeneous nanoparticles produced by the liver and intestines. LPs play a major role in the transport of dietary and endogenous lipids to target cells through cell membrane receptors or cell surface-bound lipoprotein lipase. The stability, biocompatibility, and selective transport of LPs make them promising delivery vehicles for various therapeutic and imaging agents. This review discusses isolation, manufacturing, and drug loading techniques used for LP-based drug delivery, as well as recent applications for diagnosis and treatment of cancer, atherosclerosis, and other life-threatening diseases.

Insights Into Extracellular Vesicles as Biomarker of NAFLD Pathogenesis

Nonalcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease around the world estimated to affect up to one-third of the adult population and is expected to continue rising in the coming years. Nonalcoholic fatty liver disease is considered as the hepatic manifestation of the metabolic syndrome because it is strongly associated with obesity, insulin resistance, type 2 diabetes mellitus, and cardiovascular complications. Despite its high prevalence, factors leading to NAFLD progression from simple steatosis to nonalcoholic steatohepatitis, cirrhosis, and, ultimately hepatocellular carcinoma remain poorly understood. To date, no treatment has proven efficacy, and also no reliable method is currently available for diagnosis or staging of NAFLD beyond the highly invasive liver biopsy. Recently, extracellular vesicles (EVs) have emerged as potential candidate biomarkers for the diagnosis of NAFLD. Extracellular vesicles are circulating, cell-derived vesicles containing proteins and nucleic acids, among other components, that interact with and trigger a plethora of responses in neighbor or distant target cells. Several mechanisms implicated in NAFLD progression, such as inflammation, fibrosis, and angiogenesis, all related to metabolic syndrome–associated lipotoxicity, trigger EV production and release by liver cells. As hepatocytes represent ~80% of the liver volume, in this review we will focus on hepatocyte-derived EVs as drivers of the interactome between different liver cell types in NAFLD pathogenesis, as well as in their role as noninvasive biomarkers for NAFLD diagnosis and progression. Based on that, we will highlight the research that is currently available on EVs in this topic, the current limitations, and future directions for implementation in a clinical setting as biomarkers or targets of liver disease.

Extracellular Vesicles in NAFLD/ALD: From Pathobiology to Therapy

In recent years, knowledge on the biology and pathobiology of extracellular vesicles (EVs) has exploded. EVs are submicron membrane-bound structures secreted from different cell types containing a wide variety of bioactive molecules (e.g., proteins, lipids, and nucleic acids (coding and non-coding RNA) and mitochondrial DNA). EVs have important functions in cell-to-cell communication and are found in a wide variety of tissues and body fluids. Better delineation of EV structures and advances in the isolation and characterization of their cargo have allowed the diagnostic and therapeutic implications of these particles to be explored. In the field of liver diseases, EVs are emerging as key players in the pathogenesis of both nonalcoholic liver disease (NAFLD) and alcoholic liver disease (ALD), the most prevalent liver diseases worldwide, and their complications, including development of hepatocellular carcinoma. In these diseases, stressed/damaged hepatocytes release large quantities of EVs that contribute to the occurrence of inflammation, fibrogenesis, and angiogenesis, which are key pathobiological processes in liver disease progression. Moreover, the specific molecular signatures of released EVs in biofluids have allowed EVs to be considered as promising candidates to serve as disease biomarkers. Additionally, different experimental studies have shown that EVs may have potential for therapeutic use as a liver-specific delivery method of different agents, taking advantage of their hepatocellular uptake through interactions with specific receptors. In this review, we focused on the most recent findings concerning the role of EVs as new structures mediating autocrine and paracrine intercellular communication in both ALD and NAFLD, as well as their potential use as biomarkers of disease severity and progression. Emerging therapeutic applications of EVs in these liver diseases were also examined, along with the potential for successful transition from bench to clinic.

Adipose-Derived Biogenic Nanoparticles for Suppression of Inflammation

Extracellular vesicles secreted from adipose-derived mesenchymal stem cells (ADSCs) have therapeutic effects in inflammatory diseases. However, production of extracellular vesicles (EVs) from ADSCs is costly, inefficient, and time consuming. The anti-inflammatory properties of adipose tissue-derived EVs and other biogenic nanoparticles have not been explored. In this study, biogenic nanoparticles are obtained directly from lipoaspirate, an easily accessible and abundant source of biological material. Compared to ADSC-EVs, lipoaspirate nanoparticles (Lipo-NPs) take less time to process (hours compared to months) and cost less to produce (clinical-grade cell culture facilities are not required). The physicochemical characteristics and anti-inflammatory properties of Lipo-NPs are evaluated and compared to those of patient-matched ADSC-EVs. Moreover, guanabenz loading in Lipo-NPs is evaluated for enhanced anti-inflammatory effects. Apolipoprotein E and glycerolipids are enriched in Lipo-NPs compared to ADSC-EVs. Additionally, the uptake of Lipo-NPs in hepatocytes and macrophages is higher. Lipo-NPs and ADSC-EVs have comparable protective and anti-inflammatory effects. Specifically, Lipo-NPs reduce toll-like receptor 4-induced secretion of inflammatory cytokines in macrophages. Guanabenz-loaded Lipo-NPs further suppress inflammatory pathways, suggesting that this combination therapy can have promising applications for inflammatory diseases.

Human adipose stem cell-derived extracellular nanovesicles for treatment of chronic liver fibrosis

Liver fibrosis is an excessive wound healing process that occurs in response to liver damage depending on underlying aetiologies. Currently, there are no effective therapies and FDA-approved therapeutics for the treatment of liver fibrosis except liver transplantation. Multipotent adipose-derived stem cells (ADSCs) have received significant attention as regenerative medicine for liver fibrosis owing to their advantages over stem cells with other origins. However, intrinsic limitations of stem cell therapies, such as cellular rejection and tumor formation, have impeded clinical applications of the ADSC-based liver therapeutics. To overcome these problems, the extracellular nanovesicles (ENVs) responsible for the therapeutic effect of ADSCs (A-ENVs) have shown considerable promise as cell-free therapeutics for liver diseases. However, A-ENVs have not been used for the treatment of intractable chronic liver diseases including liver fibrosis and cirrhosis. Therefore, in this study, we investigated the in vitro and in vivo antifibrotic efficacy of A-ENVs in thioacetamide-induced liver fibrosis models. A-ENVs significantly downregulated the expression of fibrogenic markers, such as matrix metalloproteinase-2, collagen-1, and alpha-smooth muscle actin. The systemic administration of A-ENVs led to high accumulation in fibrotic liver tissue and the restoration of liver functionality in liver fibrosis models through a marked reduction in α-SMA and collagen deposition. These results demonstrate the significant potential of A-ENVs for use as extracellular nanovesicles-based therapeutics in the treatment of liver fibrosis and possibly other intractable chronic liver diseases.

Applications of extracellular vesicles in tissue regeneration

Extracellular vesicles (EVs) can be classified into several types based on their different biosyntheses or release pathways, including exosomes, microvesicles, apoptotic bodies, and large oncosomes. As they contain DNAs, RNAs, proteins, and other bioactive signals, EVs have been utilized in the diagnosis field for a long time. Considering the fact that stem cells have been widely used for tissue regeneration and EVs possess similar biological properties to their source cells, tissue regeneration abilities of EVs have recently attracted much attention in the regenerative medicine field. In this paper, recent advances and challenges of EVs applied in the repair and regeneration of damaged tissues, such as skin, heart, liver, kidney, bone, and central nervous system, have been summarized. Specifically, critical bioactive molecules, which are encapsulated within EVs and play significant roles in the tissue regeneration, have been highlighted. Finally, the prospects and future development directions of the application of EVs in the field of tissue regeneration have been discussed.

Review of the Application of Nanovesicles and the Human Interstitial Fluid in Gastrointestinal Premalignant Lesion Detection, Diagnosis, Prognosis and Therapy

Premalignant lesions arise from cells that abnormally proliferate and have a tendency to become cancerous. Developing methods to specifically target and remove these premalignant lesions is imperative to the prevention of malignant progression into gastrointestinal (GI) tumors. However, accurate detection and diagnosis of GI precancerous lesions is challenging, as these lesions show little or no structural change. Thus, this prevents early intervention and reduces the success rate of therapy. In this review, we performed a systematic analysis of the technological advancements in the combined application of nanovesicles (NVs) and the human interstitial fluid (HIF) to specifically target GI premalignant lesions. NVs, which include quantum dots (QDs), are small membranous vehicles of a nanometer diameter that are widely used as drug delivery vectors, therapeutic effectors and diagnostic sensors. HIF is the fluid that is present in human interstitial tissues (HITs) in which signaling molecules and agents travel and can be found throughout the body. HIF is exploited by tumor cells for their invasion, migration and spread. Because the HITs span the entire submucosa of the gastrointestinal tract, they have been increasingly targeted in GI tumor therapy. The challenges involved in the combined application of NVs and HIF in the detection, diagnosis, prognosis and therapy of GI premalignant lesions are also discussed.

Shedding light on fibered confocal fluorescence microscopy: Applications in biomedical imaging and therapies

Discoveries of major importance in life sciences and preclinical research are linked to the invention of microscopes that enable imaging of cells and their microstructures. Imaging technologies involving in vivo procedures using fluorescent dyes that permit labelling of cells have been developed over the last two decades. Fibered confocal fluorescence microscopy (FCFM) is an imaging technology equipped with fiber-optic probes to deliver light to organs and tissues of live animals. This enables not only in vivo detection of fluorescent signals and visualization of cells, but also the study of dynamic processes, such cell proliferation, apoptosis and angiogenesis, under physiological and pathological conditions. This will allow the diagnosis of diseased organs and tissues and the evaluation of the efficacy of new therapies in animal models of human diseases. The aim of this report is to shed light on FCFM and its potential medical applications and discusses some factors that compromise the reliability and reproducibility of monitoring biological processes by FCFM. This report also highlights the issues concerning animal experimentation and welfare, and the contributions of FCFM to the 3Rs principals, replacement, reduction and refinement.

Extracellular vesicle-based drug delivery systems for cancer treatment

Extracellular vesicles (EVs) are naturally occurring cell-secreted nanoparticles that play important roles in many physiological and pathological processes. EVs enable intercellular communication by serving as delivery vehicles for a wide range of endogenous cargo molecules, such as RNAs, proteins, carbohydrates, and lipids. EVs have also been found to display tissue tropism mediated by surface molecules, such as integrins and glycans, making them promising for drug delivery applications. Various methods can be used to load therapeutic agents into EVs, and additional modification strategies have been employed to prolong circulation and improve targeting. This review gives an overview of EV-based drug delivery strategies in cancer therapy.

Mesenchymal stem cell therapies for liver cirrhosis: MSCs as "conducting cells" for improvement of liver fibrosis and regeneration

Mesenchymal stem cells (MSCs) can be cultured relatively easily and can be obtained not only from the bone marrow, but also from medical waste such as adipose tissue and umbilical cord tissue. Because of its low antigenicity, allogeneic MSC injection is safe. MSCs have been evaluated in more than 900 clinical trials in a variety of fields, with more than 50 clinical trials related to liver diseases. Experiments have suggested that MSCs function as "conducting cells" to affect various "effective cells" such as T cells, B cells, and macrophages. Recent clinical trials have focused on allogeneic MSCs. Thus, studies are needed to determine the most effective cell source, culture conditions, cell numbers, administration frequency, administration route, cost, safety, and liver disease treatments. Recently, the functions of exosomes have gained attention, and cell-free therapy may become possible as an alternative therapy for liver disease. In this review, we introduce general information, mechanism, representative clinical study data, recently started or planned clinical trials, and possibility of cell-free therapy of MSCs.

Adipose-derived cellular and cell-derived regenerative therapies in dermatology and aesthetic rejuvenation

Cellular and cell-derived components of adipose-derived tissue for the purposes of dermatologic and aesthetic rejuvenation applications have become increasingly studied and integrated into clinical practice. These components include micro-fragmented fat (nanofat), the stromal vascular fraction (SVF), adipose-derived mesenchymal stem cells (ASC), and extracellular vesicles (EVs), which have all shown capability to repair, regenerate, and rejuvenate surrounding tissue. Various aesthetic applications including hair growth, scar reduction, skin ischemia-reperfusion recovery, and facial rejuvenation are reviewed. In particular, results from preclinical and clinical studies are discussed, with a focus on clarification of nomenclature.

Role of extracellular vesicles in diagnosis and treatment of liver fibrosis

Extracellular vesicles (EVs) mediate the intercellular communication of substances and are involved in the development of liver fibrosis. The vesicles secreted by hepatic stellate cells (HSCs) and hepatic parenchymal cells carry microRNAs to activate adjacent HSCs and up-regulate TGF-β signaling pathway. This results in increased expression of connective tissue growth factor, which eventually leads to the expression of α-smooth muscle actin and collagen, thereby mediating liver fibrosis. On the other hand, EVs secreted by healthy population and mesenchymal stem cells play a therapeutic role in liver fibrosis. This article reviews the structure, origin, and function of EVs as well as their role in the occurrence, development, diagnosis, and treatment of liver fibrosis.

Organotropic drug delivery: Synthetic nanoparticles and extracellular vesicles

Most clinically approved drugs (primarily small molecules or antibodies) are rapidly cleared from circulation and distribute throughout the body. As a consequence, only a small portion of the dose accumulates at the target site, leading to low efficacy and adverse side effects. Therefore, new delivery strategies are necessary to increase organ and tissue-specific delivery of therapeutic agents. Nanoparticles provide a promising approach for prolonging the circulation time and improving the biodistribution of drugs. However, nanoparticles display several limitations, such as clearance by the immune systems and impaired diffusion in the tissue microenvironment. To overcome common nanoparticle limitations various functionalization and targeting strategies have been proposed. This review will discuss synthetic nanoparticle and extracellular vesicle delivery strategies that exploit organ-specific features to enhance drug accumulation at the target site.

Mesenchymal stem cell therapy for the treatment of inflammatory diseases: Challenges, opportunities, and future perspectives

Mesenchymal stem cells (MSCs) are promising alternative agents for the treatment of inflammatory disorders due to their immunomodulatory functions, and several clinical trials on MSC-based products are currently being conducted. In this review, we discuss recent progress made on the use of MSCs as immunomodulatory agents, developmental challenges posed by MSC-based therapy, and the strategies being used to overcome these challenges. In this context, current understanding of the mechanisms responsible for MSC interactions with the immune system and the molecular responses of MSCs to inflammatory signals are discussed. The immunosuppressive activities of MSCs are initiated by cell-to-cell contact and the release of immuno-regulatory molecules. By doing so, MSCs can inhibit the proliferation and function of T cells, natural killer cells, B cells, and dendritic cells, and can also increase the proliferation of regulatory T cells. However, various problems, such as low transplanted cell viability, poor homing and engraftment into injured tissues, MSC heterogeneity, and lack of adequate information on optimum MSC doses impede clinical applications. On the other hand, it has been shown that the immunomodulatory activities and viabilities of MSCs might be enhanced by 3D-cultured systems, genetic modifications, preconditioning, and targeted-delivery.

Clinical Cancer Nanomedicine

Nanotechnology offers new solutions for the development of cancer therapeutics that display improved efficacy and safety. Although several nanotherapeutics have received clinical approval, the most promising nanotechnology applications for patients still lie ahead. Nanoparticles display unique transport, biological, optical, magnetic, electronic, and thermal properties that are not apparent on the molecular or macroscale, and can be utilized for therapeutic purposes. These characteristics arise because nanoparticles are in the same size range as the wavelength of light and display large surface area to volume ratios. The large size of nanoparticles compared to conventional chemotherapeutic agents or biological macromolecule drugs also enables incorporation of several supportive components in addition to active pharmaceutical ingredients. These components can facilitate solubilization, protection from degradation, sustained release, immunoevasion, tissue penetration, imaging, targeting, and triggered activation. Nanoparticles are also processed differently in the body compared to conventional drugs. Specifically, nanoparticles display unique hemodynamic properties and biodistribution profiles. Notably, the interactions that occur at the bio-nano interface can be exploited for improved drug delivery. This review discusses successful clinically approved cancer nanodrugs as well as promising candidates in the pipeline. These nanotherapeutics are categorized according to whether they predominantly exploit multifunctionality, unique electromagnetic properties, or distinct transport characteristics in the body. Moreover, future directions in nanomedicine such as companion diagnostics, strategies for modifying the microenvironment, spatiotemporal nanoparticle transitions, and the use of extracellular vesicles for drug delivery are also explored.

BM-MSC-derived exosomes alleviate radiation-induced bone loss by restoring the function of recipient BM-MSCs and activating Wnt/β-catenin signaling

Background

Radiotherapy to cancer patients is inevitably accompanied by normal tissue injury, and the bone is one of the most commonly damaged tissues. Damage to bone marrow mesenchymal stem cells (BM-MSCs) induced by radiation is thought to be a major cause of radiation-induced bone loss. Exosomes exhibit great therapeutic potential in the treatment of osteoporosis, but whether exosomes are involved in radiation-induced bone loss has not been thoroughly elucidated to date. The main purpose of this study is to investigate the role of exosomes derived from BM-MSCs in restoring recipient BM-MSC function and alleviating radiation-induced bone loss.

Methods

BM-MSC-derived exosomes were intravenously injected to rats immediately after irradiation. After 28 days, the left tibiae were harvested for micro-CT and histomorphometric analysis. The effects of exosomes on antioxidant capacity, DNA damage repair, proliferation, and cell senescence of recipient BM-MSCs were determined. Osteogenic and adipogenic differentiation assays were used to detect the effects of exosomes on the differentiation potential of recipient BM-MSCs, and related genes were measured by qRT-PCR and Western blot analysis. β-Catenin expression was detected at histological and cytological levels.

Results

BM-MSC-derived exosomes can attenuate radiation-induced bone loss in a rat model that is similar to mesenchymal stem cell transplantation. Exosome-treated BM-MSCs exhibit reduced oxidative stress, accelerated DNA damage repair, and reduced proliferation inhibition and cell senescence-associate protein expression compared with BM-MSCs that exclusively received irradiation. Following irradiation, exosomes promote β-catenin expression in BM-MSCs and restore the balance between adipogenic and osteogenic differentiation.

Conclusions

Our findings indicate that BM-MSC-derived exosomes take effects by restoring the function of recipient BM-MSCs. Therefore, exosomes may represent a promising cell-free therapeutic approach for the treatment of radiation-induced bone loss.

Electronic supplementary material

The online version of this article (10.1186/s13287-018-1121-9) contains supplementary material, which is available to authorized users.

Multipotent mesenchymal stromal cells play critical roles in hepatocellular carcinoma initiation, progression and therapy

Hepatocellular carcinoma (HCC) is the most common type of primary liver cancer, with high morbidity, relapse and mortality rates. Multipotent mesenchymal stromal cells (MSCs) can be recruited to and become integral components of the HCC microenvironment and can influence tumor progression. This review discusses MSC migration to liver fibrosis and the HCC microenvironment, MSC involvement in HCC initiation and progression and the widespread application of MSCs in HCC-targeted therapy, thus clarifying the critical roles of MSCs in HCC.

Tangential Flow Filtration for Highly Efficient Concentration of Extracellular Vesicles from Large Volumes of Fluid

Concentration of extracellular vesicles (EVs) from biological fluids in a scalable and reproducible manner represents a major challenge. This study reports the use of tangential flow filtration (TFF) for the highly efficient isolation of EVs from large volumes of samples. When compared to ultracentrifugation (UC), which is the most widely used method to concentrate EVs, TFF is a more efficient, scalable, and gentler method. Comparative assessment of TFF and UC of conditioned cell culture media revealed that the former concentrates EVs of comparable physicochemical characteristics, but with higher yield, less single macromolecules and aggregates (<15 nm in size), and improved batch-to-batch consistency in half the processing time (1 h). The TFF protocol was then successfully implemented on fluids derived from patient lipoaspirate. EVs from adipose tissue are of high clinical relevance, as they are expected to mirror the regenerative properties of the parent cells.

Exosomal microRNAs as a potential therapeutic strategy in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the fifth most common cancer and the second cause of cancer-related death worldwide. The incidence of HCC is constantly increasing in correlation with the rise in diabetes and obesity, arguing for an urgent need for new developments in the treatment of this lethal cancer. Exosomes are small double-membrane vesicles loaded with distinct cargos, particularly small non-coding RNAs called microRNAs, representative of each donor cell and secreted to affect the features of neighboring cells or recipient cells located further away, like in the case of metastasis. A better understanding of the role of exosomes with a microRNA signature in cancer pathogenesis gave rise to the concept of their use as a non-invasive diagnostic biomarker and in the treatment of cancer, including HCC. In this communication, we review recent works that demonstrate that hepatic stellate cells establish an epigenetic communication with liver cancer cells, which affects their pro-malignant features. If naturally secreted patient-derived exosomes show major limitations concerning their clinical use, bio-engineered exosome mimetics that incorporate controlled components and exhibit no protumoral properties could be promising carriers for the treatment of liver cancers, which is the organ preferentially targeted by systemic injection of exosomes.

Extracellular Vesicles Secreted by Human Adipose-derived Stem Cells (hASCs) Improve Survival Rate of Rats with Acute Liver Failure by Releasing lncRNA H19

It has previously been reported that human adipose-derived stem cells (hASCs) can promote the regeneration of damaged tissues in rats with liver failure through a ‘paracrine effect’. Here we demonstrate a therapeutic effect of hASCs derived Extracellular Vesicles (EVs) on rat models with acute liver failure, as shown by the improvement of the survival rate by >70% compared to controls. Gene sequencing of rat liver revealed an increase in human long-chain non-coding RNA (lncRNA) H19 after hASC-derived EVs transplantation. When the H19 coding sequence was silenced in hASCs and EVs were then collected for treatment of rats with liver failure, we saw a decrease in the survival rate to 40%, compared to treatment with EVs generated from non-silenced hASCs. These data indicate that lncRNA H19 may be a potential therapeutic target for the treatment of liver failure.

Chloroquine and nanoparticle drug delivery: A promising combination

Clinically approved cancer therapies include small molecules, antibodies, and nanoparticles. There has been major progress in the treatment of several cancer types over recent decades. However, many challenges remain for optimal use of conventional and nanoparticle-based therapies in oncology including poor drug delivery, rapid clearance, and drug resistance. The antimalarial agent chloroquine has been found to mitigate some of these challenges by modulating cancer cells and the tissue microenvironment. Particularly, chloroquine was recently found to reduce immunological clearance of nanoparticles by resident macrophages in the liver, leading to increased tumor accumulation of nanodrugs. Additionally, chloroquine has been shown to improve drug delivery and efficacy through normalization of tumor vasculature and suppression of several oncogenic and stress-tolerance pathways, such as autophagy, that protect cancer cells from cytotoxic agents. This review will discuss the use of chloroquine as combination therapy to improve cancer treatment.

Stem Cell-Derived Exosome in Cardiovascular Diseases: Macro Roles of Micro Particles

The stem cell-based therapy has emerged as the promising therapeutic strategies for cardiovascular diseases (CVDs). Recently, increasing evidence suggest stem cell-derived active exosomes are important communicators among cells in the heart via delivering specific substances to the adjacent/distant target cells. These exosomes and their contents such as certain proteins, miRNAs and lncRNAs exhibit huge beneficial effects on preventing heart damage and promoting cardiac repair. More importantly, stem cell-derived exosomes are more effective and safer than stem cell transplantation. Therefore, administration of stem cell-derived exosomes will expectantly be an alternative stem cell-based therapy for the treatment of CVDs. Furthermore, modification of stem cell-derived exosomes or artificial synthesis of exosomes will be the new therapeutic tools for CVDs in the future. In addition, stem cell-derived exosomes also have been implicated in the diagnosis and prognosis of CVDs. In this review, we summarize the current advances of stem cell-derived exosome-based treatment and prognosis for CVDs, including their potential benefits, underlying mechanisms and limitations, which will provide novel insights of exosomes as a new tool in clinical therapeutic translation in the future.