Human bone marrow- and adipose-mesenchymal stem cells secrete exosomes enriched in distinctive miRNA and tRNA species

Therapeutic potential of mesenchymal stem cells for diabetes

Mesenchymal stem cells (MSCs) are self-renewing multipotent cells that have the capacity to secrete multiple biologic factors that can restore and repair injured tissues. Preclinical and clinical evidence have substantiated the therapeutic benefit of MSCs in various medical conditions. Currently, MSCs are the most commonly used cell-based therapy in clinical trials because of their regenerative effects, ease of isolation and low immunogenicity. Experimental and clinical studies have provided promising results using MSCs to treat diabetes. This review will summarize the role of MSCs on tissue repair, provide emerging strategies to improve MSC function and describe how these processes translate to clinical treatments for diabetes.

Exosomes secreted from mutant-HIF-1α-modified bone-marrow-derived mesenchymal stem cells attenuate early steroid-induced avascular necrosis of femoral head in rabbit

Mesenchymal stem cells (MSCs)-derived exosomes exhibit protective effects on damaged or diseased tissues. Hypoxia-inducible factor 1α (HIF-1α) plays a critical role in bone development. However, HIF-1α is easily biodegradable under normoxic conditions. The bone-marrow-derived mesenchymal stem cells (BMSCs) were transfected with adenovirus carrying triple point-mutations (amino acids 402, 564, and 803) in the HIF-1α coding sequence (CDS). The mutant HIF-1α can efficiently express functional proteins under normoxic conditions. To date, no study has reported the role of exosomes secreted by mutant HIF-1α modified BMSCs in the recovery of the early steroid-induced avascular necrosis of femoral head (SANFH). In this study, we firstly analyzed exosomes derived from BMSCs modified by mutant (BMSC-Exos^MU ) or wild-type HIF-1α (BMSC-Exos^WT ). In vitro, we investigated the osteogenic differentiation capacity of BMSCs modified by BMSC-Exos^MU or BMSC-Exos^WT , and the angiogenesis effects of BMSC-Exos^MU and BMSC-Exos^WT on human umbilical vein endothelial cells (HUVECs). Besides, the healing of the femoral head was also assessed in vivo. We found that the potential of osteogenic differentiation of BMSCs treated with BMSC-Exos^MU was higher than the wild-type group in vitro. In addition, BMSC-Exos^MU stimulated the proliferation, migration, and tube formation of HUVECs in a dose-dependent manner. Compared with the BMSC-Exos^WT or PBS control group, the injection of BMSC-Exos^MU into the necrosis region markedly accelerated the bone regeneration and angiogenesis, which were indicated by the increased trabecular reconstruction and microvascular density. Taken together, our data suggest that BMSC-Exos^MU facilitates the repair of SANFH by enhancing osteogenesis and angiogenesis.

Engineering of extracellular vesicles as drug delivery vehicles

Extracellular vesicles (EVs) are secreted membrane-enclosed nano-sized particles (40-1,000 nm) that deliver biological information between cells. The molecular composition of these subcellular particles includes growth factor receptors, ligands adhesion proteins, mRNA, miRNAs, lncRNA and lipids that are derived from donor cells. A number of studies demonstrated that stem cell-derived EVs are the key mediator of tissue repair and regeneration in multiple animal disease models. In addition, the composition of these particles is known to be altered in cancer and disease pathology suggesting them for useful in diagnostic and therapeutic purposes. Their endogenous origin and biological properties offer benefits over conventional drug delivery systems (DDS), such as liposome, synthetic nanoparticles and prompted the further application of EVs as drug delivery vehicles for chemical drugs, genetic materials and proteins. The contents of EVs can be efficiently modified by chemical, biological or physical means. Thus, EVs can be an innovative DDS as it can overcome physical and biological barriers and safely deliver therapeutic drugs to target tissues. In this minireview, we summarized current progress on the strategies of drug loading onto EVs; ex vivo and in vivo loading.

Extracellular Vesicles in Angiogenesis

During the past decade, extracellular vesicles (EVs), which include apoptotic bodies, microvesicles, and exosomes, have emerged as important players in cell-to-cell communication in normal physiology and pathological conditions. EVs encapsulate and convey various bioactive molecules that are further transmitted to neighboring or more distant cells, where they induce various signaling cascades. The message delivered to the target cells is dependent on EV composition, which, in turn, is determined by the cell of origin and the surrounding microenvironment during EV biogenesis. Among their multifaceted role in the modulation of biological responses, the involvement of EVs in vascular development, growth, and maturation has been widely documented and their potential therapeutic application in regenerative medicine or angiogenesis-related diseases is drawing increasing interest. EVs derived from various cell types have the potential to deliver complex information to endothelial cells and to induce either pro- or antiangiogenic signaling. As dynamic systems, in response to changes in the microenvironment, EVs adapt their cargo composition to fine-tune the process of blood vessel formation. This article reviews the current knowledge on the role of microvesicles and exosomes from various cellular origins in angiogenesis, with a particular emphasis on the underlying mechanisms, and discusses the main challenges and prerequisites for their therapeutic applications.

Stem cell-derived exosomes: A promising strategy for fracture healing

OBJECTIVES

To describe the biological characteristics of exosomes and to summarize the current status of stem cell-derived exosomes on fracture healing. Meanwhile, future challenges, limitations and perspectives are also discussed.

METHODS

Search and analyze the related articles in pubmed database through the multi-combination of keywords like "stem cells","exosomes","bone regeneration" and "fracture healing".

CONCLUSION

Stem cell-derived exosome therapy for fracture healing has been enjoying popularity and is drawing increasing attention. This strategy helps to promote proliferation and migration of cells, as well as osteogenesis and angiogenesis, in the process of bone formation. Although the exact mechanisms remain elusive, exosomal miRNAs seem to play vital roles. Future studies are required to solve multiple problems before clinical application, including comprehensive and thorough understanding of exosomes, the exact roles of exosomes in regulating bone formation, and the optimal source, dose and frequency of treatment, as well as technical and safety issues. Moreover, studies based on fracture models of large animals are could offer guidance and are in demand.

MicroRNA-100 shuttled by mesenchymal stem cell-derived exosomes suppresses in vitro angiogenesis through modulating the mTOR/HIF-1α/VEGF signaling axis in breast cancer cells

BACKGROUND

Human mesenchymal stem cells (MSCs) have been shown to be involved in the formation and modulation of tumor stroma and in interacting with tumor cells, partly through their secretome. Exosomes are nano-sized intraluminal multi-vesicular bodies secreted by most types of cells and have been found to mediate intercellular communication through the transfer of genetic information via coding and non-coding RNAs to recipient cells. Since exosomes are considered as protective and enriched sources of shuttle microRNAs (miRNAs), we hypothesized that exosomal transfer of miRNAs from MSCs may affect tumor cell behavior, particularly angiogenesis.

METHODS

Exosomes derived from MSCs were isolated and characterized by scanning electron microscopy analyses, dynamic light scattering measurements, and Western blotting. Fold changes in miR-100 expression levels were calculated in exosomes and their corresponding donor cells by qRT-PCR. The effects of exosomal transfer of miR-100 from MSCs were assessed by qRT-PCR and Western blotting of the mTOR/HIF-1α/VEGF signaling axis in breast cancer cells. The quantification of secreted VEGF protein was determined by enzyme-linked immunosorbent assay. The putative paracrine effects of MSC-derived exosomes on tumor angiogenesis were explored by in vitro angiogenesis assays including endothelial cell proliferation, migration and tube formation assays.

RESULTS

We found that MSC-derived exosomes induce a significant and dose-dependent decrease in the expression and secretion of vascular endothelial growth factor (VEGF) through modulating the mTOR/HIF-1α signaling axis in breast cancer-derived cells. We also found that miR-100 is enriched in MSC-derived exosomes and that its transfer to breast cancer-derived cells is associated with the down-regulation of VEGF in a time-dependent manner. The putative role of exosomal miR-100 transfer in regulating VEGF expression was substantiated by the ability of anti-miR-100 to rescue the inhibitory effects of MSC-derived exosomes on the expression of VEGF in breast cancer-derived cells. In addition, we found that down-regulation of VEGF mediated by MSC-derived exosomes can affect the vascular behavior of endothelial cells in vitro.

CONCLUSIONS

Overall, our findings suggest that exosomal transfer of miR-100 may be a novel mechanism underlying the paracrine effects of MSC-derived exosomes and may provide a means by which these vesicles can modulate vascular responses within the microenvironment of breast cancer cells.

Blocking Tumor-Educated MSC Paracrine Activity Halts Osteosarcoma Progression

Purpose: Human osteosarcoma is a genetically heterogeneous bone malignancy with poor prognosis despite the employment of aggressive chemotherapy regimens. Because druggable driver mutations have not been established, dissecting the interactions between osteosarcoma cells and supporting stroma may provide insights into novel therapeutic targets.Experimental Design: By using a bioluminescent orthotopic xenograft mouse model of osteosarcoma, we evaluated the effect of tumor extracellular vesicle (EV)-educated mesenchymal stem cells (TEMSC) on osteosarcoma progression. Characterization and functional studies were designed to assess the mechanisms underlying MSC education. Independent series of tissue specimens were analyzed to corroborate the preclinical findings, and the composition of patient serum EVs was analyzed after isolation with size-exclusion chromatography.Results: We show that EVs secreted by highly malignant osteosarcoma cells selectively incorporate a membrane-associated form of TGFβ, which induces proinflammatory IL6 production by MSCs. TEMSCs promote tumor growth, accompanied with intratumor STAT3 activation and lung metastasis formation, which was not observed with control MSCs. Importantly, intravenous administration of the anti-IL6 receptor antibody tocilizumab abrogated the tumor-promoting effects of TEMSCs. RNA-seq analysis of human osteosarcoma tissues revealed a distinct TGFβ-induced prometastatic gene signature. Tissue microarray immunostaining indicated active STAT3 signaling in human osteosarcoma, consistent with the observations in TEMSC-treated mice. Finally, we isolated pure populations of EVs from serum and demonstrated that circulating levels of EV-associated TGFβ are increased in osteosarcoma patients.Conclusions: Collectively, our findings suggest that TEMSCs promote osteosarcoma progression and provide the basis for testing IL6- and TGFβ-blocking agents as new therapeutic options for osteosarcoma patients. Clin Cancer Res; 23(14); 3721-33. ©2017 AACR.

Trophic Activity and Phenotype of Adipose Tissue-Derived Mesenchymal Stem Cells as a Background of Their Regenerative Potential

There has been an increased interest in mesenchymal stem cells from adipose tissue, due to their abundance and accessibility with no ethical concerns. Their multipotent properties make them appropriate for regenerative clinical applications. It has been shown that adipose-derived stem cells (ASCs) may differ between the origin sites. Moreover, a variety of internal and external factors may affect their biological characteristics, as what we aimed to highlight in this review. It has been demonstrated that ASCs secrete multiple trophic factors that are capable of stimulating cell proliferation and differentiation and migration of various cell types. Particular attention should be given to exosomes, since it is known that they contribute to the paracrine effects of MSCs. Secretion of trophic agents by ASCs is thought to be in a greater importance for regenerative medicine applications, rather than cells engraftment to the site of injury and their differentiation ability. The surface marker profile of ASCs seems to be similar to that of the mesenchymal stem cells from bone marrow, although some molecular differences are observed. Thus, in this review, we have attempted to define trophic activity, as well as phenotypic characterization of ASCs, as crucial factors for therapeutic usage.

The metabolic syndrome alters the miRNA signature of porcine adipose tissue-derived mesenchymal stem cells

Autologous transplantation of mesenchymal stem cells (MSCs) is a viable option for the treatment of several diseases. Evidence indicates that MSCs release extracellular vesicles (EVs) and that EVs shuttle miRNAs to damaged parenchymal cells to activate an endogenous repair program. We hypothesize that comorbidities may interfere with the packaging of cargo in MSC-derived EVs. Therefore, we examined whether metabolic syndrome (MetS) modulates the miRNA content packed within MSC-derived EVs. MSCs were collected from swine abdominal adipose tissue after 16 weeks of lean or obese diet (n = 7 each). Next-generation RNA sequencing of miRNAs (miRNA-seq) was performed to identify miRNAs enriched in MSC-derived EVs and their predicted target genes. Functional pathway analysis of the top 50 target genes of the top 4 miRNAs enriched in each group was performed using gene ontology analysis. Lean- and MetS-EVs were enriched in, respectively, 14 and 8 distinct miRNAs. Target genes of miRNAs enriched in MetS-EVs were implicated in the development of MetS and its complications, including diabetes-related pathways, validated transcriptional targets of AP1 family members Fra1 and Fra2, Class A/1 (Rhodopsin-like receptors), and Peptide ligand-binding receptors. In contrast, miRNAs enriched in Lean EVs target primarily EphrinA-EPHA and the Rho family of GTPases. MetS alters the miRNA content of EVs derived from porcine adipose tissue MSCs. These alterations could impair the efficacy and limit the therapeutic use of autologous MSCs in subjects with MetS. Our findings may assist in developing adequate regenerative strategies to preserve the reparative potency of MSCs in individuals with MetS. © 2017 International Society for Advancement of Cytometry.

Extracellular vesicles of stromal origin target and support hematopoietic stem and progenitor cells

Extracellular vesicles (EVs) are emerging as crucial mediators in cell-to-cell communication. Stik et al. provide evidence that EVs released by supportive stromal cells target hematopoietic stem and progenitor cells in vivo and in vitro and influence their gene expression and potential.

Extracellular vesicles (EVs) have been recently reported as crucial mediators in cell-to-cell communication in development and disease. In this study, we investigate whether mesenchymal stromal cells that constitute a supportive microenvironment for hematopoietic stem and progenitor cells (HSPCs) released EVs that could affect the gene expression and function of HSPCs. By taking advantage of two fetal liver–derived stromal lines with widely differing abilities to maintain HSPCs ex vivo, we demonstrate that stromal EVs play a critical role in the regulation of HSPCs. Both supportive and nonsupportive stromal lines secreted EVs, but only those delivered by the supportive line were taken up by HSPCs ex vivo and in vivo. These EVs harbored a specific molecular signature, modulated the gene expression in HSPCs after uptake, and maintained the survival and clonogenic potential of HSPCs, presumably by preventing apoptosis. In conclusion, our study reveals that EVs are an important component of the HSPC niche, which may have major applications in regenerative medicine.

Mesenchymal stem cells and their therapeutic applications in inflammatory bowel disease

Mesenchymal stem or stromal cells (MSCs) are non-hematopoietic stem cells that facilitate tissue regeneration through mechanisms involving self-renewal and differentiation, supporting angiogenesis and tissue cell survival, and limiting inflammation. MSCs were originally identified and expanded in long-term cultures of cells from bone marrow and other organs; and their native identity was recently confined into pericytes and adventitial cells in vascularized tissue. The multipotency, as well as the trophic and immunosuppressive effects, of MSCs have prompted the rapid development of clinical applications for many diseases involving tissue inflammation and immune disorders, including inflammatory bowel disease. Although standard criteria have been established to define MSCs, their therapeutic efficacy has varied significantly among studies due to their natural heterogenicity. Thus, understanding the biological and immunological features of MSCs is critical to standardize and optimize MSCs-based therapy. In this review, we highlight the cellular and molecular mechanisms involved in MSCs-mediated tissue repair and immunosuppression. We also provide an update on the current development of MSCs-based clinical trials, with a detailed discussion of MSC-based cell therapy in inflammatory bowel disease.

MicroRNA Transfer Between Bone Marrow Adipose and Multiple Myeloma Cells

PURPOSE OF REVIEW

Multiple myeloma remains an incurable disease, largely due to the tumor-supportive role of the bone marrow microenvironment. Bone marrow adipose tissue (BMAT) is one component of the fertile microenvironment which is believed to contribute to myeloma progression and drug resistance, as well as participate in a vicious cycle of osteolysis and tumor growth.

RECENT FINDINGS

MicroRNAs (miRNAs) have recently emerged as instrumental regulators of cellular processes that enable the development and dissemination of cancer. This review highlights the intersection between two emerging research fields and pursues the scientific and clinical implications of miRNA transfer between BMAT and myeloma cells. This review provides a concise and provocative summary of the evidence to support exosome-mediated transfer of tumor-supportive miRNAs. The work may prompt researchers to better elucidate the mechanisms by which this novel means of genetic communication between tumor cells and their environment could someday yield targeted therapeutics.

Gender-specific differential expression of exosomal miRNA in synovial fluid of patients with osteoarthritis

The pathogenesis of osteoarthritis (OA) is poorly understood, and therapeutic approaches are limited to preventing progression of the disease. Recent studies have shown that exosomes play a vital role in cell-to-cell communication, and pathogenesis of many age-related diseases. Molecular profiling of synovial fluid derived exosomal miRNAs may increase our understanding of OA progression and may lead to the discovery of novel biomarkers and therapeutic targets. In this article we report the first characterization of exosomes miRNAs from human synovial fluid. The synovial fluid exosomes share similar characteristics (size, surface marker, miRNA content) with previously described exosomes in other body fluids. MiRNA microarray analysis showed OA specific exosomal miRNA of male and female OA. Gene Ontology (GO) analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis identified gender-specific target genes/signaling pathways. These pathway analyses showed that female OA specific miRNAs are estrogen responsive and target TLR (toll-like receptor) signaling pathways. Furthermore, articular chondrocytes treated with OA derived extracellular vesicles had decreased expression of anabolic genes and elevated expression of catabolic and inflammatory genes. In conclusion, synovial fluid exosomal miRNA content is altered in patients with OA and these changes are gender specific.

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

Proliferating hepatic stellate cells (HSCs) respond to liver damage by secreting collagens that form fibrous scar tissue, which can lead to cirrhosis if in appropriately regulated. Advancement of microRNA (miRNA) hepatic therapies has been hampered by difficulties in delivering miRNA to damaged tissue. However, exosomes secreted by adipose‐derived mesenchymal stem cells (ADSCs) can be exploited to deliver miRNAs to HSCs. ADSCs were engineered to overexpress miRNA‐181‐5p (miR‐181‐5p‐ADSCs) to selectively home exosomes to mouse hepatic stellate (HST‐T6) cells or a CCl4‐induced liver fibrosis murine model and compared with non‐targeting control Caenorhabditis elegans miR‐67 (cel‐miR‐67)‐ADSCs. In vitro analysis confirmed that the transfer of miR‐181‐5p from miR‐181‐5p‐ADSCs occurred via secreted exosomal uptake. Exosomes were visualized in HST‐T6 cells using cyc3‐labelled pre‐miRNA‐transfected ADSCs with/without the exosomal inhibitor, GW4869. The effects of miRNA‐181‐5p overexpression on the fibrosis associated STAT3/Bcl‐2/Beclin 1 pathway and components of the extracellular matrix were assessed. Exosomes from miR181‐5p‐ADSCs down‐regulated Stat3 and Bcl‐2 and activated autophagy in the HST‐T6 cells. Furthermore, the up‐regulated expression of fibrotic genes in HST‐T6 cells induced by TGF‐β1 was repressed following the addition of isolated miR181‐5p‐ADSC exosomes compared with miR‐67‐ADSCexosomes. Exosome therapy attenuated liver injury and significantly down‐regulated collagen I, vimentin, α‐SMA and fibronectin in liver, compared with controls. Taken together, the effective anti‐fibrotic function of engineered ADSCs is able to selectively transfer miR‐181‐5p to damaged liver cells and will pave the way for the use of exosome‐ADSCs for therapeutic delivery of miRNA targeting liver disease.

Mesenchymal stem cell transplantation in tight-skin mice identifies miR-151-5p as a therapeutic target for systemic sclerosis

Systemic sclerosis (SSc), an autoimmune disease, may cause significant osteopenia due to activation of the IL4Rα/mTOR pathway. Mesenchymal stem cell transplantation (MSCT) can ameliorate immune disorders in SSc via inducing immune tolerance. However, it is unknown whether MSCT rescues osteopenia phenotype in SSc. Here we show that MSCT can effectively ameliorate osteopenia in SSc mice by rescuing impaired lineage differentiation of the recipient bone marrow MSCs. Mechanistically, we show that donor MSCs transfer miR-151-5p to the recipient bone marrow MSCs in SSc mice to inhibit IL4Rα expression, thus downregulating mTOR pathway activation to enhance osteogenic differentiation and reduce adipogenic differentiation. Moreover, systemic delivery of miR-151-5p is capable of rescuing osteopenia, impaired bone marrow MSCs, tight skin, and immune disorders in SSc mice, suggesting that miR-151-5p may be a specific target for SSc treatment. Our finding identifies a previously unrecognized role of MSCT in transferring miRNAs to recipient stem cells to ameliorate osteopenia via rescuing a non-coding RNA pathway.

Extracellular Vesicles as Therapeutic Agents in Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a heterogeneous autoimmune disease that affects multiple organs. Currently, therapeutic molecules present adverse side effects and are only effective in some SLE patient subgroups. Extracellular vesicles (EV), including exosomes, microvesicles and apoptotic bodies, are released by most cell types, carry nucleic acids, proteins and lipids and play a crucial role in cell-to-cell communication. EVs can stimulate or suppress the immune responses depending on the context. In SLE, EVs can work as autoadjuvants, enhance immune complex formation and maintaining inflammation state. Over the last years, EVs derived from mesenchymal stem cells and antigen presenting cells have emerged as cell-free therapeutic agents to treat autoimmune and inflammatory diseases. In this review, we summarize the current therapeutic applications of extracellular vesicles to regulate immune responses and to ameliorate disease activity in SLE and other autoimmune disorders.

Effect of the Microenvironment on Mesenchymal Stem Cell Paracrine Signaling: Opportunities to Engineer the Therapeutic Effect

Cues from the extracellular environment, including physical stimuli, are well known to affect mesenchymal stem cell (MSC) properties in terms of proliferation and differentiation. Many therapeutic strategies are now targeting this knowledge to increase the efficacy of cell therapies, typically employed to repair tissue functions in the event of injury, either by direct engraftment into the target tissue or differentiation into mature tissues. However, it is now envisioned that harnessing the repertoire of factors secreted by MSCs (termed the secretome) may provide an alternate to these cell therapies. Of current interest are both direct protein secretions and two major subpopulations of bioactive extracellular vesicles (EVs), namely exosomes and microvesicles. EVs released by MSCs are reflective of their cells of origin, able to impact upon the activities of other cells in the local microenvironment, making the rational design of MSC paracrine activities an encouraging strategy to reproducibly modulate cell therapies. The precise mechanisms by which the secretome is modulated by the microenvironment, however, remain elusive. Controlling MSC growth conditions with oxygen tension, growth factor composition, and mechanical properties may serve to directly influence paracrine activity. Our growing understanding implicates components of the mechanotransduction machinery in translating both mechanical and chemical cues from the environment into alterations in gene regulation and varied paracrine activity. As technologies are developed to manufacture MSCs, advances in bioengineering and novel insight of how the extracellular environment affects MSC paracrine activity will play a pivotal role in the generation of widespread, successful, clinical MSC therapies.

Integrated transcriptomic and proteomic analysis of the molecular cargo of extracellular vesicles derived from porcine adipose tissue-derived mesenchymal stem cells

Background

Mesenchymal stromal/stem cell (MSC) transplantation is a promising therapy for tissue regeneration. Extracellular vesicles (EVs) released by MSCs act as their paracrine effectors by delivering proteins and genetic material to recipient cells. To assess how their cargo mediates biological processes that drive their therapeutic effects, we integrated miRNA, mRNA, and protein expression data of EVs from porcine adipose tissue-derived MSCs.

Methods

Simultaneous expression profiles of miRNAs, mRNAs, and proteins were obtained by high-throughput sequencing and LC-MS/MS proteomic analysis in porcine MSCs and their daughter EVs (n = 3 each). TargetScan and ComiR were used to predict miRNA target genes. Functional annotation analysis was performed using DAVID 6.7 database to rank primary gene ontology categories for the enriched mRNAs, miRNA target genes, and proteins. STRING was used to predict associations between mRNA and miRNA target genes.

Results

Differential expression analysis revealed 4 miRNAs, 255 mRNAs, and 277 proteins enriched in EVs versus MSCs (fold change >2, p<0.05). EV-enriched miRNAs target transcription factors (TFs) and EV-enriched mRNAs encode TFs, but TF proteins are not enriched in EVs. Rather, EVs are enriched for proteins that support extracellular matrix remodeling, blood coagulation, inflammation, and angiogenesis.

Conclusions

Porcine MSC-derived EVs contain a genetic cargo of miRNAs and mRNAs that collectively control TF activity in EVs and recipient cells, as well as proteins capable of modulating cellular pathways linked to tissue repair. These properties provide the fundamental basis for considering therapeutic use of EVs in tissue regeneration.

Combining stable insect cell lines with baculovirus-mediated expression for multi-HA influenza VLP production

Safer and broadly protective vaccines are needed to cope with the continuous evolution of circulating influenza virus strains and promising approaches based on the expression of multiple hemagglutinins (HA) in a virus-like particle (VLP) have been proposed. However, expression of multiple genes in the same vector can lead to its instability due to tandem repetition of similar sequences. By combining stable with transient expression systems we can rationally distribute the number of genes to be expressed per platform and thus mitigate this risk. In this work, we developed a modular system comprising stable and baculovirus-mediated expression in insect cells for production of multi-HA influenza enveloped VLPs. First, a stable insect High Five cell population expressing two different HA proteins from subtype H3 was established. Infection of this cell population with a baculovirus vector encoding three other HA proteins from H3 subtype proved to be as competitive as traditional co-infection approaches in producing a pentavalent H3 VLP. Aiming at increasing HA expression, the stable insect cell population was infected at increasingly higher cell concentrations (CCI). However, cultures infected at CCI of 3×10⁶cells/mL showed lower HA titers per cell in comparison to standard CCI of 2×10⁶cells/mL, a phenomenon named "cell density effect". To lessen the negative impact of this phenomenon, a tailor-made refeed strategy was designed based on the exhaustion of key nutrients during cell growth. Noteworthy, cultures supplemented and infected at a CCI of 4×10⁶cells/mL showed comparable HA titers per cell to those of CCI of 2×10⁶cells/mL, thus leading to an increase of up to 4-fold in HA titers per mL. Scalability of the modular strategy herein proposed was successfully demonstrated in 2L stirred tank bioreactors with comparable HA protein levels observed between bioreactor and shake flasks cultures. Overall, this work demonstrates the suitability of combining stable with baculovirus-mediated expression in insect cells as an efficient platform for production of multi-HA influenza VLPs, surpassing the drawbacks of traditional co-infection strategies and/or the use of larger, unstable vectors.

Mesenchymal Stem Cell-Derived Extracellular Vesicles: Roles in Tumor Growth, Progression, and Drug Resistance

Mesenchymal stem cells (MSCs) are ubiquitously present in many tissues. Due to their unique advantages, MSCs have been widely employed in clinical studies. Emerging evidences indicate that MSCs can also migrate to the tumor surrounding stroma and exert complex effects on tumor growth and progression. However, the effect of MSCs on tumor growth is still a matter of debate. Several studies have shown that MSCs could favor tumor growth. On the contrary, other groups have demonstrated that MSCs suppressed tumor progression. Extracellular vesicles have emerged as a new mechanism of cell-to-cell communication in the development of tumor diseases. MSCs-derived extracellular vesicles (MSC-EVs) could mimic the effects of the mesenchymal stem cells from which they originate. Different studies have reported that MSC-EVs may exert various effects on the growth, metastasis, and drug response of different tumor cells by transferring proteins, messenger RNA, and microRNA to recipient cells. In the present review, we summarize the components of MSC-EVs and discuss the roles of MSC-EVs in different malignant diseases, including the related mechanisms that may account for their therapeutic potential. MSC-EVs open up a promising opportunity in the treatment of cancer with increased efficacy.

Mesenchymal Stem Cell-Derived Extracellular Vesicles as Mediators of Anti-Inflammatory Effects: Endorsement of Macrophage Polarization

Mesenchymal Stem Cells (MSCs) are effective therapeutic agents enhancing the repair of injured tissues mostly through their paracrine activity. Increasing evidences show that besides the secretion of soluble molecules, the release of extracellular vesicles (EVs) represents an alternative mechanism adopted by MSCs. Since macrophages are essential contributors toward the resolution of inflammation, which has emerged as a finely orchestrated process, the aim of the present study was to carry out a detailed characterization of EVs released by human adipose derived-MSCs to investigate their involvement as modulators of MSC anti-inflammatory effects inducing macrophage polarization. The EV-isolation method was based on repeated ultracentrifugations of the medium conditioned by MSC exposed to normoxic or hypoxic conditions (EVNormo and EVHypo ). Both types of EVs were efficiently internalized by responding bone marrow-derived macrophages, eliciting their switch from a M1 to a M2 phenotype. In vivo, following cardiotoxin-induced skeletal muscle damage, EVNormo and EVHypo interacted with macrophages recruited during the initial inflammatory response. In injured and EV-treated muscles, a downregulation of IL6 and the early marker of innate and classical activation Nos2 were concurrent to a significant upregulation of Arg1 and Ym1, late markers of alternative activation, as well as an increased percentage of infiltrating CD206pos cells. These effects, accompanied by an accelerated expression of the myogenic markers Pax7, MyoD, and eMyhc, were even greater following EVHypo administration. Collectively, these data indicate that MSC-EVs possess effective anti-inflammatory properties, making them potential therapeutic agents more handy and safe than MSCs. Stem Cells Translational Medicine 2017 Stem Cells Translational Medicine 2017;6:1018-1028.

Exosomes: Origins and Therapeutic Potential for Neurodegenerative Disease

Exosomes, small lipid bilayer vesicles, are part of the transportable cell secretome that can be taken up by nearby recipient cells or can travel through the bloodstream to cells in distant organs. Selected cellular cytoplasm containing proteins, RNAs, and other macromolecules is packaged into secreted exosomes. This cargo has the potential to affect cellular function in either healthy or pathological ways. Exosomal content has been increasingly shown to assist in promoting pathways of neurodegeneration such as β-amyloid peptide (Aβ) accumulation forming amyloid plaques in the brains of patients with Alzheimer's disease, and pathological aggregates of proteins containing α-synuclein in Parkinson's disease transferred to the central nervous system via exosomes. In attempting to address such debilitating neuropathologies, one promising utility of exosomes lies in the development of methodology to use exosomes as natural delivery vehicles for therapeutics. Because exosomes are capable of penetrating the blood-brain barrier, they can be strategically engineered to carry drugs or other treatments, and possess a suitable half-life and stability for this purpose. Overall, analyses of the roles that exosomes play between diverse cellular sites will refine our understanding of how cells communicate. This mini-review introduces the origin and biogenesis of exosomes, their roles in neurodegenerative processes in the central nervous system, and their potential utility to deliver therapeutic drugs to cellular sites.

Bone Marrow-Derived Mesenchymal Stem Cells-Derived Exosomes Promote Survival of Retinal Ganglion Cells Through miRNA-Dependent Mechanisms

The loss of retinal ganglion cells (RGC) and their axons is one of the leading causes of blindness and includes traumatic (optic neuropathy) and degenerative (glaucoma) eye diseases. Although no clinical therapies are in use, mesenchymal stem cells (MSC) have demonstrated significant neuroprotective and axogenic effects on RGC in both of the aforementioned models. Recent evidence has shown that MSC secrete exosomes, membrane enclosed vesicles (30–100 nm) containing proteins, mRNA and miRNA which can be delivered to nearby cells. The present study aimed to isolate exosomes from bone marrow‐derived MSC (BMSC) and test them in a rat optic nerve crush (ONC) model. Treatment of primary retinal cultures with BMSC‐exosomes demonstrated significant neuroprotective and neuritogenic effects. Twenty‐one days after ONC and weekly intravitreal exosome injections; optical coherence tomography, electroretinography, and immunohistochemistry was performed. BMSC‐derived exosomes promoted statistically significant survival of RGC and regeneration of their axons while partially preventing RGC axonal loss and RGC dysfunction. Exosomes successfully delivered their cargo into inner retinal layers and the effects were reliant on miRNA, demonstrated by the diminished therapeutic effects of exosomes derived from BMSC after knockdown of Argonaute‐2, a key miRNA effector molecule. This study supports the use of BMSC‐derived exosomes as a cell‐free therapy for traumatic and degenerative ocular disease. Stem Cells Translational Medicine2017;6:1273–1285

MiRNA-Sequence Indicates That Mesenchymal Stem Cells and Exosomes Have Similar Mechanism to Enhance Cardiac Repair

Mesenchymal stem cells (MSCs) repair infarcted heart through paracrine mechanism. We sought to compare the effectiveness of MSCs and MSC-derived exosomes (MSC-Exo) in repairing infarcted hearts and to identify how MSC-Exo mediated cardiac repair is regulated. In a rat myocardial infarction model, we found that MSC-Exo inhibited cardiac fibrosis, inflammation, and improved cardiac function. The beneficial effects of MSC-Exo were significantly superior compared to that of MSCs. To explore the potential mechanisms underlying MSC-Exo's effects, we performed several in vitro experiments and miRNA-sequence analysis. MSC-Exo stimulated cardiomyocyte H9C2 cell proliferation, inhibited apoptosis induced by H₂O₂, and inhibited TGF-β induced transformation of fibroblast cell into myofibroblast. Importantly, novel miRNA sequencing results indicated that MSC-Exo and MSCs have similar miRNA expression profile, which could be one of the reasons that MSC-Exo can replace MSCs for cardiac repair. In addition, the expression of several miRNAs from MSC-Exo was significantly different from that of MSCs, which may explain why MSC-Exo has better therapeutic effect than MSCs. In conclusion, this study demonstrates that MSC-Exo could be used alone to promote cardiac repair and are superior to MSCs in repairing injured myocardium.

Ribonucleic artefacts: are some extracellular RNA discoveries driven by cell culture medium components?

In a recently published study, Anna Krichevsky and colleagues raise the important question of whether results of in vitro extracellular RNA (exRNA) studies, including extracellular vesicle (EV) investigations, are confounded by the presence of RNA in cell culture medium components such as foetal bovine serum (FBS). The answer, according to their data, is a resounding “yes”. Even after lengthy ultracentrifugation to remove bovine EVs from FBS, the majority of exRNA in FBS remained. Although technical factors may affect the degree of depletion, residual EVs and exRNA in FBS could influence the conclusions of in vitro studies: certainly, for secreted RNA, and possibly also for cell-associated RNA. In this commentary, we critically examine some of the literature in this field, including a recent study from some of the authors of this piece, in light of the Wei et al. study and explore how cell culture-derived RNAs may affect what we think we know about EV RNAs. These findings hold particular consequence as the field moves towards a deeper understanding of EV–RNA associations and potential functions.

Extracellular Vesicles from Adipose Tissue-A Potential Role in Obesity and Type 2 Diabetes?

Adipose tissue plays a key role in the development of insulin resistance and its pathological sequelae, such as type 2 diabetes and non-alcoholic fatty liver disease. Dysfunction in the adipose tissue response to storing excess fatty acids as triglyceride can lead to adipose tissue inflammation and spillover of fatty acids from this tissue and accumulation of fatty acids as lipid droplets in ectopic sites, such as liver and muscle. Extracellular vesicles (EVs) are released from adipocytes and have been proposed to be involved in adipocyte/macrophage cross talk and to affect insulin signaling and transforming growth factor β expression in liver cells leading to metabolic disease. Furthermore EV produced by adipose tissue-derived mesenchymal stem cells (ADSC) can promote angiogenesis and cancer cell migration and have neuroprotective and neuroregenerative properties. ADSC EVs have therapeutic potential in vascular and neurodegenerative disease and may also be used to target specific functional miRNAs to cells. Obesity is associated with an increase in adipose-derived EV which may be related to the metabolic complications of obesity. In this review, we discuss our current knowledge of EV produced by adipose tissue and the potential impact of adipose tissue-derived EV on metabolic diseases associated with obesity.

Integration of Genomics Into Treatment: Are We There Yet?

Using advances in genetic analysis to segment and direct treatment of multiple myeloma (MM) represents a way of maintaining therapeutic progress. Recent genetic analyses have opened the possibility of enhancing risk stratification approaches and of using different risk and biologic strata as part of clinical trials. The Myeloma Genome Project is a collaborative project that has compiled the largest set of cases with sequencing and have outcome data that are available for stratification purposes. Mutation-targeted treatment of the Ras pathway has been shown to be active in MM, but is compromised by the presence of the subclonal genetic variation typical of myeloma. Going forward, risk and biologically stratified therapy for MM looks to be a promising way of maintaining therapeutic progress, as does precision immunotherapy directed by the cellular context of the bone marrow.

Mesenchymal Stem Cell-derived Extracellular Vesicles for Renal Repair

INTRODUCTION

Transplantation of autologous mesenchymal stem cells (MSCs) has been shown to attenuate renal injury and dysfunction in several animal models, and its efficacy is currently being tested in clinical trials for patients with renal disease. Accumulating evidence indicates that MSCs release extracellular vesicles (EVs) that deliver genes, microRNAs and proteins to recipient cells, acting as mediators of MSC paracrine actions. In this context, it is critical to characterize the MSC-derived EV cargo to elucidate their potential contribution to renal repair. In recent years, researchers have performed high-throughput sequencing and proteomic analysis to detect and identify genes, microRNAs, and proteins enriched in MSC-derived EVs.

CONCLUSION

The present review summarizes the current knowledge of the MSC-derived EV secretome to shed light into the mechanisms mediating MSC renal repair, and discusses preclinical and clinical studies testing the efficacy of MSC-derived EVs for treating renal disease.

MSC exosome as a cell-free MSC therapy for cartilage regeneration: Implications for osteoarthritis treatment

Mesenchymal stem cell (MSC) therapies have demonstrated efficacy in cartilage repair in animal and clinical studies. The efficacy of MSC-based therapies which was previously predicated on the chondrogenic potential of MSC is increasingly attributed to the paracrine secretion, particularly exosomes. Exosomes are thought to function primarily as intercellular communication vehicles to transfer bioactive lipids, nucleic acids (mRNAs and microRNAs) and proteins between cells to elicit biological responses in recipient cells. For MSC exosomes, many of these biological responses translated to a therapeutic outcome in injured or diseased cells. Here, we review the current understanding of MSC exosomes, discuss the possible mechanisms of action in cartilage repair within the context of the widely reported immunomodulatory and regenerative potency of MSC exosomes, and provide new perspectives for development of an off-the-shelf and cell-free MSC therapy for treatment of cartilage injuries and osteoarthritis.

Recent Developments in Cellular Immunotherapy for HSCT-Associated Complications

Allogeneic hematopoietic stem cell transplantation is associated with serious complications, and improvement of the overall clinical outcome of patients with hematological malignancies is necessary. During the last decades, posttransplant donor-derived adoptive cellular immunotherapeutic strategies have been progressively developed for the treatment of graft-versus-host disease (GvHD), infectious complications, and tumor relapses. To date, the common challenge of all these cell-based approaches is their implementation for clinical application. Establishing an appropriate manufacturing process, to guarantee safe and effective therapeutics with simultaneous consideration of economic requirements is one of the most critical hurdles. In this review, we will discuss the recent scientific findings, clinical experiences, and technological advances for cell processing toward the application of mesenchymal stromal cells as a therapy for treatment of severe GvHD, virus-specific T cells for targeting life-threating infections, and of chimeric antigen receptors-engineered T cells to treat relapsed leukemia.

Stem Cell Extracellular Vesicles: Extended Messages of Regeneration

Stem cells are critical to maintaining steady-state organ homeostasis and regenerating injured tissues. Recent intriguing reports implicate extracellular vesicles (EVs) as carriers for the distribution of morphogens and growth and differentiation factors from tissue parenchymal cells to stem cells, and conversely, stem cell-derived EVs carrying certain proteins and nucleic acids can support healing of injured tissues. We describe approaches to make use of engineered EVs as technology platforms in therapeutics and diagnostics in the context of stem cells. For some regenerative therapies, natural and engineered EVs from stem cells may be superior to single-molecule drugs, biologics, whole cells, and synthetic liposome or nanoparticle formulations because of the ease of bioengineering with multiple factors while retaining superior biocompatibility and biostability and posing fewer risks for abnormal differentiation or neoplastic transformation. Finally, we provide an overview of current challenges and future directions of EVs as potential therapeutic alternatives to cells for clinical applications.

Mesenchymal Stromal Cells Derived Extracellular Vesicles Ameliorate Acute Renal Ischemia Reperfusion Injury by Inhibition of Mitochondrial Fission through miR-30

Background. The immoderation of mitochondrial fission is one of the main contributors in ischemia reperfusion injury (IRI) and mesenchymal stromal cells (MSCs) derived extracellular vesicles have been regarded as a potential therapy method. Here, we hypothesized that extracellular vesicles (EVs) derived from human Wharton Jelly mesenchymal stromal cells (hWJMSCs) ameliorate acute renal IRI by inhibiting mitochondrial fission through miR-30b/c/d. Methods. EVs isolated from the condition medium of MCS were injected intravenously in rats immediately after monolateral nephrectomy and renal pedicle occlusion for 45 minutes. Animals were sacrificed at 24 h after reperfusion and samples were collected. MitoTracker Red staining was used to see the morphology of the mitochondria. The expression of DRP1 was measured by western blot. miR-30 in EVs and rat tubular epithelial cells was assessed by qRT-PCR. Apoptosis pathway was identified by immunostaining. Results. We found that the expression of miR-30 in injured kidney tissues was declined and mitochondrial dynamics turned to fission. But they were both restored in EVs group in parallel with reduced cell apoptosis. What is more, when the miR-30 antagomirs were used to reduce the miRNA levels, all the related effects of EVs reduced remarkably. Conclusion. A single administration of hWJMSC-EVs could protect the kidney from IRI by inhibition of mitochondrial fission via miR-30.

Respiratory Syncytial Virus-Infected Mesenchymal Stem Cells Regulate Immunity via Interferon Beta and Indoleamine-2,3-Dioxygenase

Respiratory syncytial virus (RSV) has been reported to infect human mesenchymal stem cells (MSCs) but the consequences are poorly understood. MSCs are present in nearly every organ including the nasal mucosa and the lung and play a role in regulating immune responses and mediating tissue repair. We sought to determine whether RSV infection of MSCs enhances their immune regulatory functions and contributes to RSV-associated lung disease. RSV was shown to replicate in human MSCs by fluorescence microscopy, plaque assay, and expression of RSV transcripts. RSV-infected MSCs showed differentially altered expression of cytokines and chemokines such as IL-1β, IL6, IL-8 and SDF-1 compared to epithelial cells. Notably, RSV-infected MSCs exhibited significantly increased expression of IFN-β (~100-fold) and indoleamine-2,3-dioxygenase (IDO) (~70-fold) than in mock-infected MSCs. IDO was identified in cytosolic protein of infected cells by Western blots and enzymatic activity was detected by tryptophan catabolism assay. Treatment of PBMCs with culture supernatants from RSV-infected MSCs reduced their proliferation in a dose dependent manner. This effect on PBMC activation was reversed by treatment of MSCs with the IDO inhibitors 1-methyltryptophan and vitamin K3 during RSV infection, a result we confirmed by CRISPR/Cas9-mediated knockout of IDO in MSCs. Neutralizing IFN-β prevented IDO expression and activity. Treatment of MSCs with an endosomal TLR inhibitor, as well as a specific inhibitor of the TLR3/dsRNA complex, prevented IFN-β and IDO expression. Together, these results suggest that RSV infection of MSCs alters their immune regulatory function by upregulating IFN-β and IDO, affecting immune cell proliferation, which may account for the lack of protective RSV immunity and for chronicity of RSV-associated lung diseases such as asthma and COPD.

Mesenchymal Stem Cell-Derived Exosomes: New Opportunity in Cell-Free Therapy

Mesenchymal stromal/stem cells (MSCs) are involved in tissue homeostasis through direct cell-to-cell interaction, as well as secretion of soluble factors. Exosomes are the sort of soluble biological mediators that obtained from MSCs cultured media in vitro. MSC-derived exosomes (MSC-DEs) which produced under physiological or pathological conditions are central mediators of intercellular communications by conveying proteins, lipids, mRNAs, siRNA, ribosomal RNAs and miRNAs to the neighbor or distant cells. MSC-DEs have been tested in various disease models, and the results have revealed that their functions are similar to those of MSCs. They have the supportive functions in organisms such as repairing tissue damages, suppressing inflammatory responses, and modulating the immune system. MSC-DEs are of great interest in the scope of regenerative medicine because of their unique capacity to the regeneration of the damaged tissues, and the present paper aims to introduce MSC-DEs as a novel hope in cell-free therapy.

Secreted trophic factors of mesenchymal stem cells support neurovascular and musculoskeletal therapies

Adult mesenchymal stem cells (MSCs) represent a subject of intense experimental and biomedical interest. Recently, trophic activities of MSCs have become the topic of a number of revealing studies that span both basic and clinical fields. In this review, we focus on recent investigations that have elucidated trophic mechanisms and shed light on MSC clinical efficacy relevant to musculoskeletal applications. Innate differences due to MSC sourcing may play a role in the clinical utility of isolated MSCs. Pain management, osteochondral, nerve, or blood vessel support by MSCs derived from both autologous and allogeneic sources have been examined. Recent mechanistic insights into the trophic activities of these cells point to ultimate regulation by nitric oxide, nuclear factor-kB, and indoleamine, among other signaling pathways. Classic growth factors and cytokines-such as VEGF, CNTF, GDNF, TGF-β, interleukins (IL-1β, IL-6, and IL-8), and C-C ligands (CCL-2, CCL-5, and CCL-23)-serve as paracrine control molecules secreted or packaged into extracellular vesicles, or exosomes, by MSCs. Recent studies have also implicated signaling by microRNAs contained in MSC-derived exosomes. The response of target cells is further regulated by their microenvironment, involving the extracellular matrix, which may be modified by MSC-produced matrix metalloproteinases (MMPs) and tissue inhibitor of MMPs. Trophic activities of MSCs, either resident or introduced exogenously, are thus intricately controlled, and may be further fine-tuned via implant material modifications. MSCs are actively being investigated for the repair and regeneration of both osteochondral and other musculoskeletal tissues, such as tendon/ligament and meniscus. Future rational and effective MSC-based musculoskeletal therapies will benefit from better mechanistic understanding of MSC trophic activities, for example using analytical "-omics" profiling approaches.

Non-coding RNA as mediators in microenvironment–breast cancer cell communication

The tumor microenvironment has a critical role in the survival and decision of the cancer cells. These include support by enhanced angiogenesis, and metastasis or adaptation of dormancy. This article discusses methods by which the microenvironment sustains the tumor. This process is important as it will identify avenues of drug targets. Non-coding RNAs (ncRNAs) are evolving as key mediators in the interaction between the cancer cells and the microenvironment. Thus, the question is how to develop methods to effectively block the effects of the ncRNA and/or to introduce them to prevent metastasis, dormancy or to reverse dormancy. We focused on the advantages of using mesenchymal stem cells (MSCs) for RNA delivery. MSCs can be available as "off-the-shelf" cells. Thus far, MSCs are shown to be safe when transplanted across allogeneic barriers. We discussed the various methods by which MSCs can interact with cancer cells to deliver ncRNA or antagomirs. We also include the advances and possible confounds of using these methods. Overall, this review article provides a potential method by which MSCs can be used for effective delivery of nucleic acid to treat cancer.

Anti-Inflammatory Mechanism of Neural Stem Cell Transplantation in Spinal Cord Injury

Neural stem cell (NSC) transplantation has been proposed to promote functional recovery after spinal cord injury. However, a detailed understanding of the mechanisms of how NSCs exert their therapeutic plasticity is lacking. We transplanted mouse NSCs into the injured spinal cord seven days after SCI, and the Basso Mouse Scale (BMS) score was performed to assess locomotor function. The anti-inflammatory effects of NSC transplantation was analyzed by immunofluorescence staining of neutrophil and macrophages and the detection of mRNA levels of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), interleukin-6 (IL-6) and interleukin-12 (IL-12). Furthermore, bone marrow-derived macrophages (BMDMs) were co-cultured with NSCs and followed by analyzing the mRNA levels of inducible nitric oxide synthase (iNOS), TNF-α, IL-1β, IL-6 and IL-10 with quantitative real-time PCR. The production of TNF-α and IL-1β by BMDMs was examined using the enzyme-linked immunosorbent assay (ELISA). Transplanted NSCs had significantly increased BMS scores (p < 0.05). Histological results showed that the grafted NSCs migrated from the injection site toward the injured area. NSCs transplantation significantly reduced the number of neutrophils and iNOS+/Mac-2+ cells at the epicenter of the injured area (p < 0.05). Meanwhile, mRNA levels of TNF-α, IL-1β, IL-6 and IL-12 in the NSCs transplantation group were significantly decreased compared to the control group. Furthermore, NSCs inhibited the iNOS expression of BMDMs and the release of inflammatory factors by macrophages in vitro (p < 0.05). These results suggest that NSC transplantation could modulate SCI-induced inflammatory responses and enhance neurological function after SCI via reducing M1 macrophage activation and infiltrating neutrophils. Thus, this study provides a new insight into the mechanisms responsible for the anti-inflammatory effect of NSC transplantation after SCI.

MSCs-Derived Exosomes: Cell-Secreted Nanovesicles with Regenerative Potential

Exosomes are membrane-enclosed nanovesicles (30–150 nm) that shuttle active cargoes between different cells. These tiny extracellular vesicles have been recently isolated from mesenchymal stem cells (MSCs) conditioned medium, a population of multipotent cells identified in several adult tissues. MSCs paracrine activity has been already shown to be the key mediator of their elicited regenerative effects. On the other hand, the individual contribution of MSCs-derived exosomes for these effects is only now being unraveled. The administration of MSCs-derived exosomes has been demonstrated to restore tissue function in multiple diseases/injury models and to induce beneficial in vitro effects, mainly mediated by exosomal-enclosed miRNAs. Additionally, the source and the culture conditions of MSCs have been shown to influence the regenerative responses induced by exosomes. Therefore, these studies reveal that MSCs-derived exosomes hold a great potential for cell-free therapies that are safer and easier to manipulate than cell-based products. Nevertheless, this is an emerging research field and hence, further studies are required to understand the full dimension of this complex intercellular communication system and how it can be optimized to take full advantage of its therapeutic effects. In this mini-review, we summarize the most significant new advances in the regenerative properties of MSCs-derived exosomes and discuss the molecular mechanisms underlying these effects.

Mesenchymal Stem Cell-Derived Exosomes Promote Fracture Healing in a Mouse Model

: Paracrine signaling by bone-marrow-derived mesenchymal stem cells (MSCs) plays a major role in tissue repair. Although the production of regulatory cytokines by MSC transplantation is a critical modulator of tissue regeneration, we focused on exosomes, which are extracellular vesicles that contain proteins and nucleic acids, as a novel additional modulator of cell-to-cell communication and tissue regeneration. To address this, we used radiologic imaging, histological examination, and immunohistochemical analysis to evaluate the role of exosomes isolated from MSC-conditioned medium (CM) in the healing process in a femur fracture model of CD9^-/- mice, a strain that is known to produce reduced levels of exosomes. We found that the bone union rate in CD9^-/- mice was significantly lower than wild-type mice because of the retardation of callus formation. The retardation of fracture healing in CD9^-/- mice was rescued by the injection of exosomes, but this was not the case after the injection of exosomes-free conditioned medium (CM-Exo). The levels of the bone repair-related cytokines, monocyte chemotactic protein-1 (MCP-1), MCP-3, and stromal cell-derived factor-1 in exosomes were low compared with levels in CM and CM-Exo, suggesting that bone repair may be in part mediated by other exosome components, such as microRNAs. These results suggest that exosomes in CM facilitate the acceleration of fracture healing, and we conclude that exosomes are a novel factor of MSC paracrine signaling with an important role in the tissue repair process.

SIGNIFICANCE

This work focuses on exosomes, which are extracellular vesicles, as a novel additional modulator of cell-to-cell communication. This study evaluated the role of exosomes isolated from mesenchymal stem cell (MSC)-conditioned medium (MSC-CM) in the fracture-healing process of CD9^-/- mice, a strain that is known to produce reduced levels of exosomes. Retardation of fracture healing in CD9^-/- mice was rescued by the injection of MSC exosomes, but this was not the case after the injection of exosome-free CM. This study finds that MSC exosomes are a novel factor of MSC paracrine signaling, with an important role in the tissue repair process.

In Vivo therapeutic potential of mesenchymal stem cell-derived extracellular vesicles with optical imaging reporter in tumor mice model

Mesenchymal stem cells (MSCs) can be used as a therapeutic armor for cancer. Extracellular vesicles (EVs) from MSCs have been evaluated for anticancer effects. In vivo targeting of EVs to the tumor is an essential requirement for successful therapy. Therefore, non-invasive methods of monitoring EVs in animal models are crucial for developing EV-based cancer therapies. The present study to develop bioluminescent EVs using Renilla luciferase (Rluc)-expressing MSCs. The EVs from MSC/Rluc cells (EV-MSC/Rluc) were visualized in a murine lung cancer model. The anticancer effects of EVs on Lewis lung carcinoma (LLC) and other cancer cells were assessed. EV-MSC/Rluc were visualized in vivo in the LLC-efffuc tumor model using optical imaging. The induction of apoptosis was confirmed with Annexin-V and propidium iodide staining. EV-MSC/Rluc and EV-MSCs showed a significant cytotoxic effect against LLC-effluc cells and 4T1; however, no significant effect on CT26, B16F10, TC1 cells. Moreover, EV-MSC/Rluc inhibited LLC tumor growth in vivo. EV-MSC/Rluc-mediated LLC tumor inhibitory mechanism revealed the decreased pERK and increased cleaved caspase 3 and cleaved PARP. We successfully developed luminescent EV-MSC/Rluc that have a therapeutic effect on LLC cells in both in vitro and in vivo. This bioluminescent EV system can be used to optimize EV-based therapy.

Luminal Extracellular Vesicles (EVs) in Inflammatory Bowel Disease (IBD) Exhibit Proinflammatory Effects on Epithelial Cells and Macrophages

BACKGROUND

Extracellular vesicles (EVs) are membrane-enclosed particles released by cells as a means of intercellular communication. They are potential novel biomarkers, as they are readily isolated from body fluids, and their composition reflects disease pathways. Whether these particles are released from sites of intestinal inflammation in inflammatory bowel disease (IBD) has not previously been determined.

METHODS

EVs were isolated by ultracentrifugation of colonic luminal fluid aspirates and characterized according to surface proteins, and constituent mRNA and proteins. The effects of EVs on colonic epithelial cells and macrophages in culture were assessed at the transcriptional, translational, and functional levels.

RESULTS

Intestinal luminal aspirates contained abundant EVs, at a mean concentration of 4.3 × 10 particles/mL and with a mean diameter of 146 nm. EVs from patients with IBD with a high endoscopic score (≥1) contained significantly higher mRNA and protein levels of interleukin 6 (IL-6), IL-8, IL-10, and tumor necrosis factor α than EVs from healthy controls. EVs were absorbed by cultured colonic epithelial cells, leading to an increased translation of IL-8 protein by recipient cells when treated with EVs from patients with IBD. EVs and EV-treated epithelial cells induced migration of a significantly greater number of macrophages than epithelial cells alone.

CONCLUSIONS

EVs shed from sites of intestinal inflammation in patients with IBD have a distinct mRNA and protein profile from those of healthy individuals. These EVs have proinflammatory effects on the colonic epithelium, in vitro. Their stability in luminal samples and their mRNA and protein content identify them as a potential fecal biomarker that reflects mucosal inflammatory pathways.