Exosomal regulation of lymphocyte homing to the gut

Implication of the Annexin 1/FPR axis in leishmanial exosome-mediated Leishmania major skin hyperpathogenesis

Introduction

Exosomes produced by the protozoan parasite Leishmania (LeishEXO) are well-established drivers of virulence, though mechanisms underlying their exacerbation of experimental leishmaniasis remain elusive. Expression of Annexin A1 (ANXA1), a protein implicated in exosome-mediated pathologies and viral internalization, has been shown to correlate with cutaneous leishmaniasis severity. Given ANXA1's regulation of myeloid cells - the canonical hosts for Leishmania - we studied the potential role of ANXA1 and its receptors FPR1/2 in exerting LeishEXO's effects.

Methods

Murine and in vitro ANXA1-/- models were used to study the generation of protective TH1 responses during experimental L. major infection with and without LeishEXO. Recruitment of inflammatory cells was assessed using a peritoneal cell recruitment assay and immunophenotyping, and production of inflammatory mediators was measured using a cytokine and chemokine array. Treatment of experimental models with FPR2 antagonist WRW4 and FPR1/2 agonist WKYMVm was used to delineate the role of the FPR/ANXA1 axis in LeishEXO-mediated hyperpathogenesis.

Results

We established that ANXA1 deficiency prohibits LeishEXO-mediated pathogenesis and myeloid cell infection, with minimal alterations to adaptive and innate immune phenotypes. FPR2 blockade with WRW4 similarly inhibited leishmanial hyperpathogenesis, while direct activation of FPRs with WKYMVm enhanced infection and recapitulated the LeishEXO-mediated phenotype. This research describes LeishEXO's utilization of the ANXA1/FPR axis to facilitate parasitic internalization and pathogenesis, which may be leveraged in the development of therapeutics for leishmaniasis.

miR-200c-3p regulates α4 integrin-mediated T cell adhesion and migration

A microRNA miR-200c-3p is a regulator of epithelial-mesenchymal transition to control adhesion and migration of epithelial and mesenchymal cells. However, little is known about whether miR-200c-3p affects lymphocyte adhesion and migration mediated by integrins. Using TK-1 (a T lymphoblast cell) as a model of T cell, here we show that repressed expression of miR-200c-3p upregulated α4 integrin-mediated adhesion to and migration across mucosal addressin cell adhesion molecule-1 (MAdCAM-1). Conversely, overexpression of miR-200c-3p downregulated α4 integrin-mediated adhesion and migration. Unlike in epithelial cells, miR-200c-3p did not target talin, a conformation activator of integrin, but, targeted E26-transformation-specific sequence 1 (ETS1), a transcriptional activator of α4 integrin, in T cells. Treatment of the miR-200c-3p-low-expressing TK-1 cells that possessed elevated α4 integrin with ETS1 small interfering RNA (siRNA) resulted in the reversion of the α4 integrin expression, supporting that ETS1 is a target of miR-200c-3p. A potential proinflammatory immune-modulator retinoic acid (RA) treatment of TK-1 cells elicited a significant reduction of miR-200c-3p and simultaneously a marked increase in ETS1 and α4 integrin expression. An anti-inflammatory cytokine TGF-β1 treatment elevated miR-200c-3p, thereby downregulating ETS1 and α4 integrin expression. These results suggest that miR-200c-3p is an important regulator of α4 integrin expression and functions and may be controlled by RA and TGF-β1 in an opposite way. Overexpression of miR-200c-3p could be a novel therapeutic option for treatment of gut inflammation through suppressing α4 integrin-mediated T cell migration.

Optimization of ultracentrifugation-based method to enhance the purity and proteomic profiling depth of plasma-derived extracellular vesicles and particles

Circulating extracellular vesicles and particles (EVPs) are being investigated as potential biomarkers for early cancer detection, prognosis, and disease monitoring. However, the suboptimal purity of EVPs isolated from peripheral blood plasma has posed a challenge of in-depth analysis of the EVP proteome. Here, we compared the effectiveness of different methods for isolating EVPs from healthy donor plasma, including ultracentrifugation (UC)-based protocols, phosphatidylserine-Tim4 interaction-based affinity capture (referred to as "PS"), and several commercial kits. Modified UC methods with an additional UC washing or size exclusion chromatography step substantially improved EVP purity and enabled the detection of additional proteins via proteomic mass spectrometry, including many plasma membrane and cytoplasmic proteins involved in vesicular regulation pathways. This improved performance was reproduced in cancer patient plasma specimens, resulting in the identification of a greater number of differentially expressed EVP proteins, thus expanding the range of potential biomarker candidates. However, PS and other commercial kits did not outperform UC-based methods in improving plasma EVP purity. PS yielded abundant contaminating proteins and a biased enrichment for specific EVP subsets, thus unsuitable for proteomic profiling of plasma EVPs. Therefore, we have optimized UC-based protocols for circulating EVP isolation, which enable further in-depth proteomic analysis for biomarker discovery.

Macrophages treated with interferons induce different responses in lymphocytes via extracellular vesicles

Limited information exists regarding the impact of interferons (IFNs) on the information carried by extracellular vesicles (EVs). This study aimed at investigating whether IFN-α2b, IFN-β, IFN-γ, and IFN-λ1/2 modulate the content of EVs released by primary monocyte-derived macrophages (MDM). Small-EVs (sEVs) were purified by size exclusion chromatography from supernatants of MDM treated with IFNs. To characterize the concentration and dimensions of vesicles, nanoparticle tracking analysis was used. SEVs surface markers were examined by flow cytometry. IFN treatments induced a significant down-regulation of the exosomal markers CD9, CD63, and CD81 on sEVs, and a significant modulation of some adhesion molecules, major histocompatibility complexes and pro-coagulant proteins, suggesting IFNs influence biogenesis and shape the immunological asset of sEVs. SEVs released by IFN-stimulated MDM also impact lymphocyte function, showing significant modulation of lymphocyte activation and IL-17 release. Altogether, our results show that sEVs composition and activity are affected by IFN treatment of MDM.

Formation and Investigation of Cell-Derived Nanovesicles as Potential Therapeutics against Chronic Liver Disease

A new therapeutic approach using cell-derived nanovesicles (cdNVs) is offered here to overcome the lack of effective treatments for liver fibrosis, a reversible chronic liver disease. To achieve this goal the formation and purification of cdNVs from untreated, quiescent-like, or activated LX-2 cells, an immortalized human hepatic stellate cell (HSC) line with key features of transdifferentiated HSCs are established. Analysis of the genotype and phenotype of naïve and transdifferentiated LX-2 cells activated through transforming growth factor beta 1, following treatment with cdNVs, reveals a concentration-dependent fibrosis regression. The beneficial fibrosis-resolving effects of cdNVs are linked to their biomolecular corona. Liposomes generated using lipids extracted from cdNVs exhibit a reduced antifibrotic response in perpetuated LX-2 cells and show a reduced cellular uptake. However, incubation with soluble factors collected during purification results in a new corona, thereby restoring fibrosis regression activity. Overall, cdNVs display encouraging therapeutic properties, making them a promising candidate for the development of liver fibrosis resolving therapeutics.

Engineered exosomes for tissue regeneration: from biouptake, functionalization and biosafety to applications

Exosomes are increasingly recognized as important effector molecules that regulate intercellular signaling pathways. Notably, certain types of exosomes can induce therapeutic responses, including cell proliferation, angiogenesis, and tissue repair. The use of exosomes in therapy is a hot spot in current research, especially in regenerative medicine. Despite the therapeutic potential, problems have hindered their success in clinical applications. These shortcomings include low concentration, poor targeting and limited loading capability. To fully realize their therapeutic potential, certain modifications are needed in native exosomes. In the present review, we summarize the exosome modification and functionalization strategies. In addition, we provide an overview of potential clinical applications and highlight the issues associated with the biosafety and biocompatibility of engineered exosomes in applications.

Bioinspired Lipid Nanocarriers for RNA Delivery

RNA therapy is a disruptive technology comprising a rapidly expanding category of drugs. Further translation of RNA therapies to the clinic will improve the treatment of many diseases and help enable personalized medicine. However, in vivo delivery of RNA remains challenging due to the lack of appropriate delivery tools. Current state-of-the-art carriers such as ionizable lipid nanoparticles still face significant challenges, including frequent localization to clearance-associated organs and limited (1-2%) endosomal escape. Thus, delivery vehicles must be improved to further unlock the full potential of RNA therapeutics. An emerging strategy is to modify existing or new lipid nanocarriers by incorporating bioinspired design principles. This method generally aims to improve tissue targeting, cellular uptake, and endosomal escape, addressing some of the critical issues facing the field. In this review, we introduce the different strategies for creating bioinspired lipid-based RNA carriers and discuss the potential implications of each strategy based on reported findings. These strategies include incorporating naturally derived lipids into existing nanocarriers and mimicking bioderived molecules, viruses, and exosomes. We evaluate each strategy based on the critical factors required for delivery vehicles to succeed. Finally, we point to areas of research that should be furthered to enable the more successful rational design of lipid nanocarriers for RNA delivery.

From Exosome Biogenesis to Absorption: Key Takeaways for Cancer Research

Exosomes are mediators of intercellular communication in normal physiology and diseases. While many studies have emerged on the function of exosomal cargoes, questions remain regarding the origin of these exosomes. The packaging and secretion of exosomes in different contexts modify exosomal composition, which may in turn impact delivery, uptake and cargo function in recipient cells. A mechanistic understanding of exosome biology is therefore crucial to investigating exosomal function in complex biological systems and to the development of novel therapeutic approaches. Here, we outline the steps in exosome biogenesis, including endosome formation, MVB formation, cargo sorting and extracellular release, as well as exosome absorption, including targeting, interaction with recipient cells and the fate of internalized exosomes. In addition to providing a framework of exosome dynamics, we summarize current evidence on major pathways and regulatory mechanisms. We also highlight the various mechanisms observed in cancer and point out directions to improve study design in exosome biology. Further research is needed to illuminate the relationship between exosome biogenesis and function, which will aid the development of translational applications.

The emerging role of exosomes in innate immunity, diagnosis and therapy

Exosomes, which are nano-sized transport bio-vehicles, play a pivotal role in maintaining homeostasis by exchanging genetic or metabolic information between different cells. Exosomes can also play a vital role in transferring virulent factors between the host and parasite, thereby regulating host gene expression and the immune interphase. The association of inflammation with disease development and the potential of exosomes to enhance or mitigate inflammatory pathways support the notion that exosomes have the potential to alter the course of a disease. Clinical trials exploring the role of exosomes in cancer, osteoporosis, and renal, neurological, and pulmonary disorders are currently underway. Notably, the information available on the signatory efficacy of exosomes in immune-related disorders remains elusive and sporadic. In this review, we discuss immune cell-derived exosomes and their application in immunotherapy, including those against autoimmune connective tissue diseases. Further, we have elucidated our views on the major issues in immune-related pathophysiological processes. Therefore, the information presented in this review highlights the role of exosomes as promising strategies and clinical tools for immune regulation.

Integrin-Mediated Exosomal Homing to Organs

Exosomes, the small extracellular vesicles of 40-150 nm in size, are secreted by nearly all types of cells and play a dynamic role in intercellular and interorgan communications. These vesicles secreted by source cells contain a variety of biologically active materials such as microRNAs (miRNAs) or proteins, thereby utilizing these cargoes in modifying molecular functionalities of the target cells in the remote tissues. Consequently, several key functions of microenvironmental niches in the tissues are regulated in an exosome-dependent manner. The precise mechanisms by which the exosomes bind and home to different organs remained largely unknown. In recent years, integrins, a large family of cell adhesion molecules, have been revealed to play a crucial role in guiding homing of exosomes to target tissues, as integrins regulate tissue-specific homing of cells. In this regard, it is imperative to experimentally determine the roles played by integrins on the exosomes in their tissue-specific homing. This chapter presents a protocol to investigate exosomal homing regulated by integrins in in vitro and in vivo settings. We focus on β7 integrin, as its role in mediating the gut-specific homing of lymphocytes has been well established.

A kaleidoscopic view of extracellular vesicles in lysosomal storage disorders

Extracellular vesicles (EVs) are a heterogeneous population of stable lipid membrane particles that play a critical role in the regulation of numerous physiological and pathological processes. EV cargo, which includes lipids, proteins, and RNAs including miRNAs, is affected by the metabolic status of the parental cell. Concordantly, abnormalities in the autophagic-endolysosomal pathway, as seen in lysosomal storage disorders (LSDs), can affect EV release as well as EV cargo. LSDs are a group of over 70 inheritable diseases, characterized by lysosomal dysfunction and gradual accumulation of undigested molecules. LSDs are caused by single gene mutations that lead to a deficiency of a lysosomal protein or lipid. Lysosomal dysfunction sets off a cascade of alterations in the endolysosomal pathway that can affect autophagy and alter calcium homeostasis, leading to energy imbalance, oxidative stress, and apoptosis. The pathophysiology of these diseases is very heterogenous, complex, and currently incompletely understood. LSDs lead to progressive multisystemic symptoms that often include neurological deficits. In this review, a kaleidoscopic overview will be given on the roles of EVs in LSDs, from their contribution to pathology and diagnostics to their role as drug delivery vehicles. Furthermore, EV cargo and surface engineering strategies will be discussed to show the potential of EVs in future LSD treatment, both in the context of enzyme replacement therapy, as well as future gene editing strategies like CRISPR/Cas. The use of engineered EVs as drug delivery vehicles may mask therapeutic cargo from the immune system and protect it from degradation, improving circulation time and targeted delivery.

Endometrial small extracellular vesicles regulate human trophectodermal cell invasion by reprogramming the phosphoproteome landscape

A series of cyclical events within the uterus are crucial for pregnancy establishment. These include endometrial regeneration following menses, under the influence of estrogen (proliferative phase), then endometrial differentiation driven by estrogen/progesterone (secretory phase), to provide a microenvironment enabling attachment of embryo (as a hatched blastocyst) to the endometrial epithelium. This is followed by invasion of trophectodermal cells (the outer layer of the blastocyst) into the endometrium tissue to facilitate intrauterine development. Small extracellular vesicles (sEVs) released by endometrial epithelial cells during the secretory phase have been shown to facilitate trophoblast invasion; however, the molecular mechanisms that underline this process remain poorly understood. Here, we show that density gradient purified sEVs (1.06-1.11 g/ml, Alix⁺ and TSG101⁺, ∼180 nm) from human endometrial epithelial cells (hormonally primed with estrogen and progesterone vs. estrogen alone) are readily internalized by a human trophectodermal stem cell line and promote their invasion into Matrigel matrix. Mass spectrometry-based proteome analysis revealed that sEVs reprogrammed trophectoderm cell proteome and their cell surface proteome (surfaceome) to support this invasive phenotype through upregulation of pro-invasive regulators associated with focal adhesions (NRP1, PTPRK, ROCK2, TEK), embryo implantation (FBLN1, NIBAN2, BSG), and kinase receptors (EPHB4/B2, ERBB2, STRAP). Kinase substrate prediction highlighted a central role of MAPK3 as an upstream kinase regulating target cell proteome reprogramming. Phosphoproteome analysis pinpointed upregulation of MAPK3 T204/T202 phosphosites in hTSCs following sEV delivery, and that their pharmacological inhibition significantly abrogated invasion. This study provides novel molecular insights into endometrial sEVs orchestrating trophoblast invasion, highlighting the microenvironmental regulation of hTSCs during embryo implantation.

Liver-originated small extracellular vesicles with TM4SF5 target brown adipose tissue for homeostatic glucose clearance

Transmembrane 4 L six family member 5 (TM4SF5) is involved in chronic liver disease, although its role in glucose homeostasis remains unknown. TM4SF5 deficiency caused age-dependent glucose (in)tolerance with no link to insulin sensitivity. Further, hepatic TM4SF5 binding to GLUT1 promoted glucose uptake and glycolysis. Excessive glucose repletion caused hepatocytes to secrete small extracellular vesicles (sEVs) loaded with TM4SF5 (hep-sEVTm4sf5 ), suggesting a role for sEVTm4sf5 in glucose metabolism and homeostasis. Hep-sEVTm4sf5 were smaller than sEVControl and recruit proteins for efficient organ tropism. Liver-derived sEVs, via a liver-closed vein circuit (LCVC) using hepatic TM4SF5-overexpressing (Alb-Tm4sf5 TG) mice (liv-sEVTm4sf5 ), improved glucose tolerance in Tm4sf5-/- KO mice and targeted brown adipose tissues (BATs), possibly allowing the clearance of blood glucose as heat independent of UCP1. Taken together, hep-sEVTm4sf5 might clear high extracellular glucose levels more efficiently by targeting BAT compared with hep-sEVControl , suggesting an insulin-like role for sEV™4SF5 in affecting age-related metabolic status and thus body weight (BW).

Role and correlation of exosomes and integrins in bone metastasis of prostate cancer

Prostate cancer (PCa) is one of the most prevalent tumours of the male genitourinary system in the world. In recent years, the morbidity of PCa is steadily rising annually in China. Prostate cancer is prone to distant metastasis, and the most significant complication among patients with advanced PCa is bone metastases. Most patients with prostate cancer do not die of the primary tumour, but more due to the factors of distant metastasis of organs, especially bone metastasis. Due to the lack of effective prevention and monitoring of bone metastasis of PCa in clinical settings, and the lack of effective treatment for patients with bone metastasis, the prognosis of patients is often poor. Therefore, early prevention, early detection, and inhibition of bone metastasis are particularly important. At present, many studies have found that exosomes and integrins are closely related to bone metastasis of prostate cancer, but they have not been summarized together. This review summarizes the literature on the effects of exosomes and integrins on bone metastasis of prostate cancer in recent years. It aims to find more effective ways to prevent, monitor, and treat prostate cancer from the relationship between them.

αvβ1 integrin is enriched in extracellular vesicles of metastatic breast cancer cells: A mechanism mediated by galectin-3

Breast cancer cells release a large quantity of biocargo-bearing extracellular vesicles (EVs), which mediate intercellular communication within the tumour microenvironment and promote metastasis. To identify EV-bound proteins related to metastasis, we used mass spectrometry to profile EVs from highly and poorly metastatic breast cancer lines of human and mouse origins. Comparative mass spectrometry indicated that integrins, including αv and β1 subunits, are preferentially enriched in EVs of highly metastatic origin over those of poorly metastatic origin. These results are consistent with our histopathological findings, which show that integrin αv is associated with disease progression in breast cancer patients. Integrin αv colocalizes with the multivesicular-body marker CD63 at a higher frequency in the tumour and is enriched in circulating EVs of breast cancer patients at late stages when compared with circulating EVs from early-stage patients. With a magnetic bead-based flow cytometry assay, we confirmed that integrins αv and β1 are enriched in the CD63⁺ subsets of EVs from both human and mouse highly metastatic cells. By analysing the level of integrin αv on circulating EVs, this assay could predict the metastatic potential of a xenografted mouse model. To explore the export mechanism of integrins into EVs, we performed immunoprecipitation mass spectrometry and identified members of the galectin family as potential shuttlers of integrin αvβ1 into EVs. In particular, knockdown of galectin-3, but not galectin-1, causes a reduction in the levels of cell surface integrins β1 and αv, and decreases the colocalization of these integrins with CD63. Importantly, knockdown of galectin-3 leads to a decrease of integrin αvβ1 export into the EVs concomitant with a decrease in the metastatic potential of breast cancer cells. Moreover, inhibition of the integrin αvβ1 complex leads to a reduction in the binding of EVs to fibronectin, suggesting that integrin αvβ1 is important for EV retention in the extracellular matrix. EVs retained in the extracellular matrix are taken up by fibroblasts, which differentiate into cancer associated fibroblasts. In summary, our data indicate an important link between EV-bound integrin αvβ1 with breast cancer metastasis and provide additional insights into the export of integrin αvβ1 into EVs in the context of metastasis.

No small matter: emerging roles for exosomal miRNAs in the immune system

Extracellular communication is critical to the function of an organism. Exosomes, small lipid extracellular vesicles, have been recently appreciated to participate in this vital function. Within these vesicles lie critical bioactive molecules including mRNAs, proteins, and a plethora of noncoding RNAs, including microRNAs (miRNAs). Exosomal miRNAs have been shown to be produced by, trafficked between, and function in many distinct donor and recipient cell types, including cells of the immune system. For instance, loss of these critical communicators can alter the cellular response to endotoxin, and when tumor cells lose the ability to secrete these vesicles, the immune system is able to effectively suppress tumor growth. This review will highlight key findings on the known communication to and from the immune system, highlighting exosomal miRNA research in macrophages, dendritic cells, B lymphocytes, and T cells. Additionally, we will focus on three major areas of exosomal studies that involve immune responses including mucosal barriers, adipose tissue, and the tumor microenvironment. These environments are heterogeneous and dynamic, and rapidly respond to the microbiota, metabolic shifts, and immunotherapies, respectively. It is clear that exosomal miRNAs play pivotal roles in regulating cross-talk between cells in these tissues, and this represents a novel layer of cellular communication proving critical in human health and disease.

Characterization of protein complexes in extracellular vesicles by intact extracellular vesicle crosslinking mass spectrometry (iEVXL)

Extracellular vesicles (EVs) are blood‐borne messengers that coordinate signalling between different tissues and organs in the body. The specificity of such crosstalk is determined by preferential EV docking to target sites, as mediated through protein‐protein interactions. As such, the need to structurally characterize the EV surface precedes further understanding of docking selectivity and recipient‐cell uptake mechanisms. Here, we describe an intact extracellular vesicle crosslinking mass spectrometry (iEVXL) method that can be applied for structural characterization of protein complexes in EVs. By using a partially membrane‐permeable disuccinimidyl suberate crosslinker, proteins on the EV outer‐surface and inside EVs can be immobilized together with their interacting partners. This not only provides covalent stabilization of protein complexes before extraction from the membrane‐enclosed environment, but also generates a set of crosslinking distance restraints that can be used for structural modelling and comparative screening of changes in EV protein assemblies. Here we demonstrate iEVXL as a powerful approach to reveal high‐resolution information, about protein determinants that govern EV docking and signalling, and as a crucial aid in modelling docking interactions.

Current understanding of extracellular vesicle homing/tropism

Extracellular vesicles (EVs) are membrane-enclosed packets released from cells that can transfer bioactive molecules from cell to cell without direct contact with the target cells. This transfer of molecules can activate consequential processes in the recipient cells, including cell differentiation and migration that maintain tissue homeostasis or promote tissue pathology. One controversial aspect of the EV's biology that holds therapeutic promise is their capacity to engage defined cells at specific sites. On the one hand, persuasive studies have shown that EVs express surface molecules that ensure their tissue localization and enable cell-specific interactions, as demonstrated using in vitro and in vivo analyses. Therefore, this feature of EV biology is under investigation in translational studies to control malignancies and deliver chemicals and bioactive molecules to combat several diseases. On the other hand, some studies have shown that EVs fail to traffic in hosts in a targeted manner, which questions the potential role of EVs as vehicles for drug delivery and their capacity to serve as cell-free biomodulators. In this review, the biology of EV homing/tropism in mammalian hosts is discussed, and the biological characteristics that may result in their controversial characteristics are brought to the fore.

Functional Flexibility of Exosomes and MicroRNAs of Intestinal Epithelial Cells in Affecting Inflammation

Intestinal epithelial cells (IECs) are a mucosal immune barrier essential to coordinate host-microbe crosstalk. Sepsis is a systemic inflammatory syndrome with dysfunction in multiple organs including the intestine whose epithelial barrier is deregulated. Thus, IECs are a main contributor to intestinal permeability and inflammation in sepsis. Exosomes emerge as a mediator of intercellular and inter-organic communications. Recently, IEC-derived exosomes and their cargoes, such as microRNAs (miRNAs), in sepsis were shown to regulate the expression of proinflammatory mediators in the inflamed gut tissues. It is a compelling hypothesis that these IEC exosomes exhibit their dynamic activity to deliver their functional miRNA cargoes to immune cells in local and distant organs to regulate proinflammatory responses and alleviate tissue injury. Also, epithelial tight junction (TJ) proteins are downregulated on gut inflammation. Some of the IEC miRNAs were reported to deteriorate the epithelial integrity by diminishing TJ expressions in intestines during sepsis and aging. Thus, it is worth revisiting and discussing the diverse functions of IEC exosomes and miRNAs in reshaping inflammations. This review includes both iterative and hypothetical statements based on current knowledge in this field.

Stem Cell Homing in Intrathecal Applications and Inspirations for Improvement Paths

A transplanted stem cell homing is a directed migration from the application site to the targeted tissue. Intrathecal application of stem cells is their direct delivery to cerebrospinal fluid, which defines the homing path from the point of injection to the brain. In the case of neurodegenerative diseases, this application method has the advantage of no blood–brain barrier restriction. However, the homing efficiency still needs improvement and homing mechanisms elucidation. Analysis of current research results on homing mechanisms in the light of intrathecal administration revealed a discrepancy between in vivo and in vitro results and a gap between preclinical and clinical research. Combining the existing research with novel insights from cutting-edge biochips, nano, and other technologies and computational models may bridge this gap faster.

Apoptotic cells derived micro/nano-sized extracellular vesicles in tissue regeneration

Extracellular vesicles (EVs), products released by cells in multiple biological activities, are currently widely accepted as functional particles and intercellular communicators. From the orthodox perspective, EVs derived from apoptotic cells (apoEVs) are responsible for cell debris clearance, while recent studies have demonstrated that apoEVs participate in tissue regeneration. However, the underlying mechanisms and particular functions in tissue regeneration promotion of apoEVs remain ambiguous. Some molecules, such as caspases, active during apoptosis also function in tissue regeneration triggered by apoptosis,. ApoEVs are generated in the process of apoptosis, carrying cell contents to manifest biological effects, and possessing biomarkers to target phagocytes. The regenerative effect of apoEVs might be due to their abilities to facilitate cell proliferation and regulate inflammation. Such regenerative effect has been observed in various tissues, including skin, bone, cardiovascular system, and kidney. Engineered apoEVs are produced to amplify the biological benefits of apoEVs, rendering them optional for drug delivery. Meanwhile, challenges exist in thorough mechanistic exploration and standardization of production. In this review, we discussed the link between apoptosis and regeneration, current comprehension of the origination and investigation strategies of apoEVs, and mechanisms in tissue regeneration by apoEVs and their applications. Challenges and prospects are also discussed here.

Liposomes and Extracellular Vesicles as Drug Delivery Systems: A Comparison of Composition, Pharmacokinetics, and Functionalization

Over the past decades, lipid-based nanoparticle drug delivery systems (DDS) have caught the attention of researchers worldwide, encouraging the field to rapidly develop improved ways for effective drug delivery. One of the most prominent examples is liposomes, which are spherical shaped artificial vesicles composed of lipid bilayers and able to encapsulate both hydrophilic and hydrophobic materials. At the same time, biological nanoparticles naturally secreted by cells, called extracellular vesicles (EVs), have emerged as promising more complex biocompatible DDS. In this review paper, the differences and similarities in the composition of both vesicles are evaluated, and critical mediators that affect their pharmacokinetics are elucidate. Different strategies that have been assessed to tweak the pharmacokinetics of both liposomes and EVs are explored, detailing the effects on circulation time, targeting capacity, and cytoplasmic delivery of therapeutic cargo. Finally, whether a hybrid system, consisting of a combination of only the critical constituents of both vesicles, could offer the best of both worlds is discussed. Through these topics, novel leads for further research are provided and, more importantly, gain insight in what the liposome field and the EV field can learn from each other.

Apoptotic cell-derived micro/nanosized extracellular vesicles in tissue regeneration

Extracellular vesicles (EVs), products released by cells in multiple biological activities, are currently widely accepted as functional particles and intercellular communicators. From the orthodox perspective, EVs derived from apoptotic cells (apoEVs) are responsible for cell debris clearance, while recent studies have demonstrated that apoEVs participate in tissue regeneration. However, the underlying mechanisms and particular functions in tissue regeneration promotion of apoEVs remain ambiguous. Some molecules active during apoptosis also function in tissue regeneration triggered by apoptosis, such as caspases. ApoEVs are generated in the process of apoptosis, carrying cell contents to manifest biological effects and possess biomarkers to target phagocytes. The regenerative effect of apoEVs might be due to their abilities to facilitate cell proliferation and regulate inflammation. Such regenerative effect has been observed in various tissues, including skin, bone, cardiovascular system, and kidneys. Engineered apoEVs are produced to amplify the biological benefits of apoEVs, rendering them optional for drug delivery. Meanwhile, challenges exist in thorough mechanistic exploration and standardization of production. In this review, we discussed the link between apoptosis and regeneration, current comprehension of the origination and investigation strategies of apoEVs, and mechanisms in tissue regeneration of apoEVs and their applications. Challenges and prospects are also addressed here.

Role of microRNAs in the Pathophysiology of Ulcerative Colitis

Ulcerative colitis (UC) is an intractable disorder characterized by a chronic inflammation of the colon. Studies have identified UC as a multifactorial disorder affected by both genetic and environmental factors; however, the precise mechanism remains unclear. Recent advances in the field of microRNA (miRNA) research have identified an association between this small non-coding RNA in the pathophysiology of UC and altered miRNA expression profiles in patients with UC. Nevertheless, the roles of individual miRNAs are uncertain due to heterogeneity in both research samples and clinical backgrounds. In this review, we focus on miRNA expression in colonic mucosa where inflammation occurs in UC and discuss the potential roles of individual miRNAs in disease development, outlining the pathophysiology of UC.

miRNA-200c-3p targets talin-1 to regulate integrin-mediated cell adhesion

The ability of integrins on the cell surface to mediate cell adhesion to the extracellular matrix ligands is regulated by intracellular signaling cascades. During this signaling process, the talin (TLN) recruited to integrin cytoplasmic tails plays the critical role of the major adaptor protein to trigger integrin activation. Thus, intracellular levels of TLN are thought to determine integrin-mediated cellular functions. However, the epigenetic regulation of TLN expression and consequent modulation of integrin activation remain to be elucidated. Bioinformatics analysis led us to consider miR-200c-3p as a TLN1-targeting miRNA. To test this, we have generated miR-200c-3p-overexpressing and miR-200c-3p-underexpressing  cell lines, including HEK293T, HCT116, and LNCaP cells. Overexpression of miR-200c-3p resulted in a remarkable decrease in the expression of TLN1, which was associated with the suppression of integrin-mediated cell adhesion to fibronectin. In contrast, the reduction in endogenous miR-200c-3p levels led to increased expression of TLN1 and enhanced cell adhesion to fibronectin and focal adhesion plaques formation. Moreover, miR-200c-3p was found to target TLN1 by binding to its 3′-untranslated region (UTR). Taken together, our data indicate that miR-200c-3p contributes to the regulation of integrin activation and cell adhesion via the targeting of TLN1.

Optimizing extracellular vesicles' isolation from chronic lymphocytic leukemia patient plasma and cell line supernatant

In chronic lymphocytic leukemia (CLL) and very likely all cancer types, extracellular vesicles (EVs) are a common mechanism by which intercellular messages are communicated between normal, diseased, and transformed cells. Studies of EVs in CLL and other cancers have great variability and often lack reproducibility. For CLL patient plasma and cell lines, we sought to characterize current approaches used in isolating EV products and understand whether cell culture-conditioned media or complex biological fluids confound results. Utilizing nanoparticle tracking analysis, protein quantification, and electron microscopy, we show that ultracentrifugation with an OptiPrep cushion can effectively minimize contaminants from starting materials including plasma and conditioned media of CLL cell lines grown in EV-depleted complete RPMI media but not grown in the serum-free media AIM V commonly used in CLL experimental work. Moreover, we confirm the benefit of including 25 mM trehalose in PBS during EV isolation steps to reduce EV aggregation, to preserve function for downstream applications and characterization. Furthermore, we report the highest particles/μg EVs were obtained from our CLL cell lines utilizing the CELLine bioreactor flask. Finally, we optimized a proliferation assay that offers a functional evaluation of our EVs with minimal sample requirements.

Extracellular vesicles for tissue repair and regeneration: Evidence, challenges and opportunities

Extracellular vesicles (EVs) are biological nanoparticles naturally secreted by cells, acting as delivery vehicles for molecular messages. During the last decade, EVs have been assigned multiple functions that have established their potential as therapeutic mediators for a variety of diseases and conditions. In this review paper, we report on the potential of EVs in tissue repair and regeneration. The regenerative properties that have been associated with EVs are explored, detailing the molecular cargo they carry that is capable of mediating such effects, the signaling cascades triggered in target cells and the functional outcome achieved. EV interactions and biodistribution in vivo that influence their regenerative effects are also described, particularly upon administration in combination with biomaterials. Finally, we review the progress that has been made for the successful implementation of EV regenerative therapies in a clinical setting.

Exploring interactions between extracellular vesicles and cells for innovative drug delivery system design

Extracellular vesicles (EVs) are submicron cell-secreted structures containing proteins, nucleic acids and lipids. EVs can functionally transfer these cargoes from one cell to another to modulate physiological and pathological processes. Due to their presumed biocompatibility and capacity to circumvent canonical delivery barriers encountered by synthetic drug delivery systems, EVs have attracted considerable interest as drug delivery vehicles. However, it is unclear which mechanisms and molecules orchestrate EV-mediated cargo delivery to recipient cells. Here, we review how EV properties have been exploited to improve the efficacy of small molecule drugs. Furthermore, we explore which EV surface molecules could be directly or indirectly involved in EV-mediated cargo transfer to recipient cells and discuss the cellular reporter systems with which such transfer can be studied. Finally, we elaborate on currently identified cellular processes involved in EV cargo delivery. Through these topics, we provide insights in critical effectors in the EV-cell interface which may be exploited in nature-inspired drug delivery strategies.

Therapeutic Exosomes in Prognosis and Developments of Coronary Artery Disease

Exosomes, with an diameter of 30~150 nm, could be released from almost all types of cells, which contain diverse effective constituent, such as RNAs, proteins, lipids, and so on. In recent years, exosomes have been verified to play an important role in mechanism, diagnosis, treatment, and prognosis of cardiovascular disease, especially coronary artery disease (CAD). Moreover, it has also been shown that exosomes derived from different cell types have various biological functions based on the cell stimulation and microenvironment. However, therapeutic exosomes are currently far away from clinical translation, despite it is full of hope. In this review, we summarize an update of the recent studies and systematic knowledge of therapeutic exosomes in atherosclerosis, myocardial infarction, and in-stent restenosis, which might provide a novel insight into the treatment of CAD and promote the potential clinical application of therapeutic exosomes.

Integrin Regulation in Immunological and Cancerous Cells and Exosomes

Integrins represent the biologically and medically significant family of cell adhesion molecules that govern a wide range of normal physiology. The activities of integrins in cells are dynamically controlled via activation-dependent conformational changes regulated by the balance of intracellular activators, such as talin and kindlin, and inactivators, such as Shank-associated RH domain interactor (SHARPIN) and integrin cytoplasmic domain-associated protein 1 (ICAP-1). The activities of integrins are alternatively controlled by homotypic lateral association with themselves to induce integrin clustering and/or by heterotypic lateral engagement with tetraspanin and syndecan in the same cells to modulate integrin adhesiveness. It has recently emerged that integrins are expressed not only in cells but also in exosomes, important entities of extracellular vesicles secreted from cells. Exosomal integrins have received considerable attention in recent years, and they are clearly involved in determining the tissue distribution of exosomes, forming premetastatic niches, supporting internalization of exosomes by target cells and mediating exosome-mediated transfer of the membrane proteins and associated kinases to target cells. A growing body of evidence shows that tumor and immune cell exosomes have the ability to alter endothelial characteristics (proliferation, migration) and gene expression, some of these effects being facilitated by vesicle-bound integrins. As endothelial metabolism is now thought to play a key role in tumor angiogenesis, we also discuss how tumor cells and their exosomes pleiotropically modulate endothelial functions in the tumor microenvironment.

Ligand-competent fractalkine receptor is expressed on exosomes

Expression of chemokine receptor CX3CR1 is reportedly restricted to several cell types including natural killer cells, cytotoxic T cells, monocytes, and macrophages. However, its expression and function on exosomes, which are nanosized extracellular vesicles known to act as mediators of intercellular communications, remain unclear. Here, we investigated CX3CR1 expression on exosomes isolated from various cell types. Although we found that all the exosomes tested in our study highly expressed CX3CR1, this chemokine receptor was expressed only inside, but barely on, their source cells. Moreover, exosomal CX3CR1 was capable of binding soluble CX3CL1. Therefore, our study suggests that CX3CR1 is a novel and ligand-competent exosome receptor.

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CX3CR1 is highly expressed by exosomes.

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Expression of CX3CR1 is restricted within, but not on, the cells.

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Exosomal CX3CR1 is capable of binding soluble CX3CL1.

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CX3CL1 binding of exosomes may deprive their source cells of the chance to bind this chemokine.

Potential Roles of Muscle-Derived Extracellular Vesicles in Remodeling Cellular Microenvironment: Proposed Implications of the Exercise-Induced Myokine, Irisin

Extracellular vesicles (EVs) have emerged as key players of intercellular communication and mediate crosstalk between tissues. Metastatic tumors release tumorigenic EVs, capable of pre-conditioning distal sites for organotropic metastasis. Growing evidence identifies muscle cell-derived EVs and myokines as potent mediators of cellular differentiation, proliferation, and metabolism. Muscle-derived EVs cargo myokines and other biological modulators like microRNAs, cytokines, chemokines, and prostaglandins hence, are likely to modulate the remodeling of niches in vital sites, such as liver and adipose tissues. Despite the scarcity of evidence to support a direct relationship between muscle-EVs and cancer metastasis, their indirect attribution to the regulation of niche remodeling and the establishment of pre-metastatic homing niches can be put forward. This hypothesis is supported by the role of muscle-derived EVs in findings gathered from other pathologies like inflammation and metabolic disorders. In this review, we present and discuss studies that evidently support the potential roles of muscle-derived EVs in the events of niche pre-conditioning and remodeling of metastatic tumor microenvironment. We highlight the potential contributions of the integrin-mediated interactions with an emerging myokine, irisin, to the regulation of EV-driven microenvironment remodeling in tumor metastasis. Further research into muscle-derived EVs and myokines in cancer progression is imperative and may hold promising contributions to advance our knowledge in the pathophysiology, progression and therapeutic management of metastatic cancers.

Integrin, Exosome and Kidney Disease

Integrins are transmembrane receptors that function as noncovalent heterodimers that mediate cellular adhesion and migration, cell to cell communication, and intracellular signaling activation. In kidney, latency associated peptide-transforming growth factor β (TGF-β) and soluble urokinase plasminogen activator receptor (suPAR) were found as the novel ligands of integrins that contribute to renal interstitial fibrosis and focal segmental glomerular sclerosis glomerulosclerosis (FSGS). Interestingly, recent studies revealed that integrins are the compositional cargo of exosomes. Increasing evidence suggested that exosomal integrin played critical roles in diverse pathophysiologic conditions such as tumor metastasis, neurological disorders, immunology regulation, and other processes. This review will focus on the biology and function of exosomal integrin, emphasizing its potential role in kidney disease as well as its implications in developing novel therapeutic and diagnosis approaches for kidney disease.

Methods to Study Integrin Functions on Exosomes

Exosomes represent an important group of extracellular vesicles. They are formed in endosomal compartments and are actively secreted to extracellular spaces. Several membrane proteins, including integrins, are present on the surface of exosomes. As exosomal integrins are competent for binding to ligand, they can play important roles in directing the tissue distribution of exosomes. Integrin-directed exosomal trafficking in vivo is involved in regulating the remodeling of cell homing niches for metastatic cancers and migrating lymphocytes. This chapter describes the methods used to study integrin functions on exosomes including: isolation and biophysical characterization of exosomes, exosomal integrin-ligand binding assays, and in vivo competitive exosome homing assays.

Circulating exosomes express α4β7 integrin and compete with CD4+ T cells for the binding to Vedolizumab

Vedolizumab (VDZ) is a therapeutic monoclonal antibody approved for the treatment of inflammatory bowel diseases (IBD). VDZ selectively binds to the α4β7 integrin and blocks trafficking of a specific subset of gastrointestinal-homing T-lymphocytes to inflamed tissue. Although VDZ has shown promising results in numerous clinical studies a subgroup of patients do not respond adequately. Mechanistic insights and prognostic biomarkers able to predict which patients might benefit from VDZ therapy are currently lacking. Circulating exosomes were isolated from serum of blood donors and VDZ-treated patients by polymer-based precipitation. The surface expression of α4β7 integrin was evaluated by flow cytometry and the levels of exosome-bound VDZ were investigated by Promonitor-VDZ ELISA kit. The capacity of exosomes to interfere with the adhesion of VDZ-treated CD4+ T cells was assessed by adhesion assay. In this study, we showed that serum exosomes isolated from both blood donor and ulcerative colitis patients express on their surface the VDZ target α4β7 integrin. We observed an increased exosomal sequestration of VDZ in anti-TNF exposed patients compared to anti- TNFα naïve patients, according to a greater expression of α4β7 integrin on vesicles surface. Circulating exosomes could compete for VDZ binding with CD4+ T cells since we found that the amount of VDZ bound to T cells was impaired in the presence of exosomes. In addition, we demonstrated that exosomes bind VDZ, which consequently becomes unable to block MadCAM-1-mediated adhesion of lymphocytes. Circulating exosomes might contribute to drug sequestration, possibly affecting the therapeutic efficacy of VDZ in IBD patients. Our data suggest that previous biologic therapy may have altered the sequestration capacity of circulating exosomes, thus reducing the efficacy of VDZ in patients who failed anti-TNF agents.

Recent Advancements in the Loading and Modification of Therapeutic Exosomes

Exosomes have a rapid development of bio-nanoparticles for drug delivery and confluent advances in next-generation diagnostics, monitoring the progression of several diseases, and accurate guidance for therapy. Based on their prominent stability, cargo-carriage properties, stable circulating capability, and favorable safety profile, exosomes have great potential to regulate cellular communication by carrying variable cargoes into specific site. However, the specific loading strategies and modification methods for engineered exosomes to enhance the targeting ability are unclear. The clinical application of exosomes is still limited. In this review, we discuss both original and modified exosomes for loading specific therapeutic molecules (proteins, nucleic acids, and small molecules) and the design strategies used to target specific cells. This review can be used as a reference for further loading and modification strategies as well as for the therapeutic applications of exosomes.

Intestinal Epithelium-Derived Luminally Released Extracellular Vesicles in Sepsis Exhibit the Ability to Suppress TNF-a and IL-17A Expression in Mucosal Inflammation

Sepsis is a systemic inflammatory disorder induced by a dysregulated immune response to infection resulting in dysfunction of multiple critical organs, including the intestines. Previous studies have reported contrasting results regarding the abilities of exosomes circulating in the blood of sepsis mice and patients to either promote or suppress inflammation. Little is known about how the gut epithelial cell-derived exosomes released in the intestinal luminal space during sepsis affect mucosal inflammation. To study this question, we isolated extracellular vesicles (EVs) from intestinal lavage of septic mice. The EVs expressed typical exosomal (CD63 and CD9) and epithelial (EpCAM) markers, which were further increased by sepsis. Moreover, septic-EV injection into inflamed gut induced a significant reduction in the messaging of pro-inflammatory cytokines TNF-α and IL-17A. MicroRNA (miRNA) profiling and reverse transcription and quantitative polymerase chain reaction (RT-qPCR) revealed a sepsis-induced exosomal increase in multiple miRNAs, which putatively target TNF-α and IL-17A. These results imply that intestinal epithelial cell (IEC)-derived luminal EVs carry miRNAs that mitigate pro-inflammatory responses. Taken together, our study proposes a novel mechanism by which IEC EVs released during sepsis transfer regulatory miRNAs to cells, possibly contributing to the amelioration of gut inflammation.

Do tumor exosome integrins alone determine organotropic metastasis?

Metastasis is the most life-threatening event in cancer patients, so the key strategy to treat cancer should be preventing tumor spread. Predicting the site of probable hematogenous metastasis is important for determining the therapeutic algorithm that could prevent the spread of tumor cells. Certain hopes for solving this problem appeared owing to study showing the association between specific integrins on tumor exosomes surface and the site of future metastasis. Numerous experimental data indicate the ability of exosomes to transfer various phlogogenic factors to the target organ, which can lead to the formation of inflammatory foci. Studies of T-lymphocytes homing show that expression of various adhesion molecules including ligands for integrins highly increases on the endothelium during inflammation. Such a mechanism underlies not only in leukocyte transvasation, but, apparently, in the accumulation of bone marrow precursor cells and the formation of a premetastatic niche. This review summarizes the most significant data on the role exosomes to induce inflammation, which leads to the recruiting of bone marrow precursors and the establishment of premetastatic niches.

Imaging intercellular interaction and extracellular vesicle exchange in a co-culture model of chronic lymphocytic leukemia and stromal cells by lattice light-sheet fluorescence microscopy

Recent advances in live cell imaging allow investigating processes that take place over the entire cell volume with unprecedented time and spatial resolution. Here we describe a protocol to study intercellular communication, including extracellular vesicle exchange, between cancer cells and their microenvironment, using lattice light sheet fluorescence microscopy. While the described protocol is intended to study the interactions between chronic lymphocytic leukemia cells and bone marrow stromal cells, many components of it can be applied to study other cancers of hematopoietic or solid tumor origin, as well as to characterize other modalities of intercellular communication.

Exosomes in Sepsis and Inflammatory Tissue Injury

Sepsis is the leading cause of death in medical intensive care units, and thus represents a serious healthcare problem worldwide. Sepsis is often caused by the aberrant host responses to infection, which induce dysregulated inflammation that leads to life-threatening multiple organ failures. Mediators such as proinflammatory cytokines that drive the sepsis pathogenesis have been extensively studied. Exosomes, biological lipid bilayer nanoparticles secreted via the endosomal pathway of cells, have recently emerged as important cargos that carry multiple mediators critical for the pathogenesis of sepsis-associated organ dysfunctions. Here we will review current knowledge on the exosomes in sepsis and relevant inflammatory tissue injuries.

Clinical applications of extracellular vesicle long RNAs

Extracellular vesicles (EVs), primarily exosomes and microvesicles, are critical intercellular mediators of communication. Over the past decade, improved knowledge and methodologies have enabled the detection and quantification of RNA species in EVs, despite their extremely low levels. Recently, EV-associated long RNAs (exLRs) have been drawing much attention. Delivered by EVs, they have higher stability, greater difference in temporal and spatial expression, and the capacity to remodel both proximal and distal recipient cells. These properties guarantee their roles as biomarkers, therapeutic targets, vaccines, and gene therapy agents in a wide range of human diseases. Despite the progress in this area of research, limitations in both knowledge and methodologies have hindered its further development. Herein, we comprehensively reviewed studies related to exLRs, including protein-coding messenger RNAs (mRNAs) and noncoding RNAs (long noncoding RNAs and circular RNAs) in EVs to indicate their value in the diagnosis and treatment of human diseases; we also present a series of yet unsettled issues in this novel area, hence providing insights for future studies.

Exosomes and Nanoengineering: A Match Made for Precision Therapeutics

Targeted exosomal delivery systems for precision nanomedicine attract wide interest across areas of molecular cell biology, pharmaceutical sciences, and nanoengineering. Exosomes are naturally derived 50-150 nm nanovesicles that play important roles in cell-to-cell and/or cell-to-tissue communications and cross-species communication. Exosomes are also a promising class of novel drug delivery vehicles owing to their ability to shield their payload from chemical and enzymatic degradations as well as to evade recognition by and subsequent removal by the immune system. Combined with a new class of affinity ligands known as aptamers or chemical antibodies, molecularly targeted exosomes are poised to become the next generation of smartly engineered nanovesicles for precision medicine. Here, recent advances in targeted exosomal delivery systems engineered by aptamer for future strategies to promote human health using this class of human-derived nanovesicles are summarized.

Targeted remodeling of breast cancer and immune cell homing niches by exosomal integrins

Exosomes represent an important subset of extracellular vesicles involved in inter-cellular communications in health and diseases. Exosomes secreted from cancer and immune cells travel to the specific tissues containing homing niches. The exosomes reaching the niches dynamically modify the gene expression and molecular architectures of the homing niche micro-environments. Cell adhesion molecule integrins regulate the tissue-specific homing patterns of not only cancer and immune cells, but also of the exosomes secreted from those cells. The exosome-mediated remodeling of the homing niches would affect immune lymphocyte migration and host defense, as well as cancer metastasis, thereby representing a potential therapeutic target.

Retinoic acid and microRNA

Retinoic acid (RA), the biologically active metabolite of vitamin A, regulates a vast spectrum of biological processes, such as cell differentiation, proliferation, apoptosis, and morphogenesis. microRNAs (miRNAs) play a crucial role in regulating gene expression by binding to messenger RNA (mRNA) which leads to mRNA degradation and/or translational repression. Like RA, miRNAs regulate multiple biological processes, including proliferation, differentiation, apoptosis, neurogenesis, tumorigenesis, and immunity. In fact, RA regulates the expression of many miRNAs to exert its biological functions. miRNA and RA regulatory networks have been studied in recent years. In this manuscript, we summarize literature that highlights the impact of miRNAs in RA-regulated molecular networks included in the PubMed.

Anti-trafficking agents in the treatment of inflammatory bowel disease

PURPOSE OF REVIEW

To describe the latest developments in the field of anti-trafficking agents (ATAs), a class of therapeutics with growing importance in the field of inflammatory bowel diseases (IBDs) that specifically inhibit steps of immune cell trafficking.

RECENT FINDINGS

Several translational and clinical studies have further shaped the knowledge about the mechanisms and effects of the anti-α4β7 integrin antibody vedolizumab. In parallel, new ATAs like the anti-β7 integrin antibody etrolizumab and the anti-MAdCAM-1 antibody ontamalimab are investigated in phase III clinical trials and might soon increase the therapeutic armamentarium in IBD.

SUMMARY

ATAs have unique mechanisms of action and can meanwhile be considered an indispensable column of IBD therapy. Further efforts are necessary to elucidate complex mechanistic aspects, to exactly define their role in relation to other therapeutic approaches and to identify novel treatment targets as well as biomarkers for personalized medicine.

Integrin-Mediated TGFβ Activation Modulates the Tumour Microenvironment

TGFβ (transforming growth factor-beta) is a pleotropic cytokine with contrasting effects in cancer. In normal tissue and early tumours, TGFβ acts as a tumour suppressor, limiting proliferation and inducing apoptosis. However, these effects are eventually abrogated by the loss or inactivation of downstream signalling within the TGFβ pathway, and in established tumours, TGFβ then acts as a tumour promotor through multiple mechanisms including inducing epithelial-to-mesenchymal transition (EMT), promoting formation of cancer-associated fibroblasts (CAFs) and increasing angiogenesis. TGFβ is secrereted as a large latent complex and is embedded in the extracellular matrix or held on the surface of cells and must be activated before mediating its multiple functions. Thus, whilst TGFβ is abundant in the tumour microenvironment (TME), its functionality is regulated by local activation. The αv-integrins are major activators of latent-TGFβ. The potential benefits of manipulating the immune TME have been highlighted by the clinical success of immune-checkpoint inhibitors in a number of solid tumour types. TGFβ is a potent suppressor of T-cell-mediated immune surveillance and a key cause of resistance to checkpoint inhibitors. Therefore, as certain integrins locally activate TGFβ, they are likely to have a role in the immunosuppressive TME, although this remains to be confirmed. In this review, we discussed the role of TGFβ in cancer, the role of integrins in activating TGFβ in the TME, and the potential benefits of targeting integrins to augment immunotherapies.

Functions of Exosomes in the Triangular Relationship between the Tumor, Inflammation, and Immunity in the Tumor Microenvironment

Exosomes are extracellular vesicles that contain diverse components such as genetic materials, proteins, and lipids. Owing to their distinct derivation and tissue specificity, exosomes act as double-edged swords during the development of neoplasms. On the one hand, tumor-derived exosomes can modulate the immune system during tumorigenesis by regulating inflammatory cell infiltration and oxidative stress and by promoting epithelial-to-mesenchymal transition and immune-induced tumor dormancy. On the other hand, components of specific immune cell-derived exosomes may contribute to the efficacy of antitumor immunotherapy. In this review, we demonstrate the pivotal role of exosomes in the triangular relationship in the tumor microenvironment between the tumor, inflammation, and immunity, which may provide potential strategies for tumor immunotherapy at genetic and cellular levels.

Talin-2 regulates integrin functions in exosomes

Integrins on exosomes have been shown to mediate binding to recipient cells, potentially playing important roles in controlling exosomal internalization and organ distributions. Although the ability of cellular integrins to mediate cell adhesion is known to be regulated by the cytoplasmic adaptor protein talin, whether the activity of exosomal integrins is similarly regulated by talin remains to be elucidated. Here we have studied this question in T-cell exosomes that surface express the integrins αLβ2 and α4β7. T-cells and T-cell exosomes engineered to lack talin-2 showed reduced binding to the integrin ligand ICAM-1 and MAdCAM-1 compared with control T-cells and exosomes, despite the fact that those T cells and exosomes express intact levels of the other isoform talin-1. In addition, talin-2-deficient T-cell exosomes were less efficiently internalized by endothelial cells, compared with control exosomes. These results suggest that the mechanisms of talin-mediated integrin regulation operate similarly in cells and exosomes.

Connexins and Integrins in Exosomes

Connexins and integrins, the two structurally and functionally distinct families of transmembrane proteins, have been shown to be inter-connected by various modes of cross-talk in cells, such as direct physical coupling via lateral contact, indirect physical coupling via actin and actin-binding proteins, and functional coupling via signaling cascades. This connexin-integrin cross-talk exemplifies a biologically important collaboration between channels and adhesion receptors in cells. Exosomes are biological lipid-bilayer nanoparticles secreted from virtually all cells via endosomal pathways into the extracellular space, thereby mediating intercellular communications across a broad range of health and diseases, including cancer progression and metastasis, infection and inflammation, and metabolic deregulation. Connexins and integrins are embedded in the exosomal membranes and have emerged as critical regulators of intercellular communication. This concise review article will explain and discuss recent progress in better understanding the roles of connexins, integrins, and their cross-talk in cells and exosomes.