Serum miR-29a Is Upregulated in Acute Graft-versus-Host Disease and Activates Dendritic Cells through TLR Binding

The roles of epigenetic regulation in graft-versus-host disease

Allogeneic hematopoietic stem cell transplantation (aHSCT) is utilized as a potential curative treatment for various hematologic malignancies. However, graft-versus-host disease (GVHD) post-aHSCT is a severe complication that significantly impacts patients' quality of life and overall survival, becoming a major cause of non-relapse mortality. In recent years, the association between epigenetics and GVHD has garnered increasing attention. Epigenetics focuses on studying mechanisms that affect gene expression without altering DNA sequences, primarily including DNA methylation, histone modifications, non-coding RNAs (ncRNAs) regulation, and RNA modifications. This review summarizes the role of epigenetic regulation in the pathogenesis of GVHD, with a focus on DNA methylation, histone modifications, ncRNA, RNA modifications and their involvement and applications in the occurrence and development of GVHD. It also highlights advancements in relevant diagnostic markers and drugs, aiming to provide new insights for the clinical diagnosis and treatment of GVHD.

MiR-574-5p activates human TLR8 to promote autoimmune signaling and lupus

Endosomal single-stranded RNA-sensing Toll-like receptor-7/8 (TLR7/8) plays a pivotal role in inflammation and immune responses and autoimmune diseases. However, the mechanisms underlying the initiation of the TLR7/8-mediated autoimmune signaling remain to be fully elucidated. Here, we demonstrate that miR-574-5p is aberrantly upregulated in tissues of lupus prone mice and in the plasma of lupus patients, with its expression levels correlating with the disease activity. miR-574-5p binds to and activates human hTLR8 or its murine ortholog mTlr7 to elicit a series of MyD88-dependent immune and inflammatory responses. These responses include the overproduction of cytokines and interferons, the activation of STAT1 signaling and B lymphocytes, and the production of autoantigens. In a transgenic mouse model, the induction of miR-574-5p overexpression is associated with increased secretion of antinuclear and anti-dsDNA antibodies, increased IgG and C3 deposit in the kidney, elevated expression of inflammatory genes in the spleen. In lupus-prone mice, lentivirus-mediated silencing of miR-574-5p significantly ameliorates major symptoms associated with lupus and lupus nephritis. Collectively, these results suggest that the miR-574-5p-hTLR8/mTlr7 signaling is an important axis of immune and inflammatory responses, contributing significantly to the development of lupus and lupus nephritis.

Forodesine Enhances Immune Responses through Guanosine-Mediated TLR7 Activation while Preventing Graft-versus-Host Disease

Recent evidence indicates that specific types of nuclear acids, including guanosine and its derivatives, act as natural ligands for TLR7. This led us to hypothesize that purine nucleoside phosphorylase inhibitors not only can induce apoptosis of T cells but also can lead to TLR7 activation by accumulation of guanine nucleosides, in particular under systemic inflammation, where damaged tissues release a large amount of nucleotides. We demonstrate in the present study that a purine nucleoside phosphorylase inhibitor, forodesine, can reduce the disease severity and prolong the survival in a xenogeneic mouse model of graft-versus-host disease (GVHD). Guanine nucleosides were undetectable in mice during GVHD but increased significantly following forodesine treatment. Our in vitro experiments showed that forodesine enhanced guanosine-mediated cytokine production from APCs, including alveolar macrophages and plasmacytoid dendritic cells, through TLR7 signaling. Forodesine also enhanced Ag-presenting capacity, as demonstrated by increased CD8+ T cell proliferation and higher secretion of IFN-γ and IL-12p40 in an MLR with plasmacytoid dendritic cells. Furthermore, forodesine stimulated IFN-γ production from activated T cells in the presence of a low concentration of guanosine while inhibiting their proliferation and inducing apoptotic cell death. Although forodesine ameliorated GVHD severity, mice treated with forodesine showed significantly higher levels of multiple proinflammatory cytokines and chemokines in plasma, suggesting in vivo upregulation of TLR7 signaling. Our study suggests that forodesine may activate a wide range of immune cells, including T cells, through TLR7 stimulation while inhibiting GVHD by inducing apoptosis of T cells, after allogeneic hematopoietic stem cell transplant.

The Role of MicroRNA in Graft-Versus-Host-Disease: A Review

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a clinically challenging modality for the treatment of many hematologic diseases such as leukemia, lymphoma, and myeloma. Graft-versus-host disease (GVHD) is a common complication after allo-HSCT and remains a major cause of morbidity and mortality, limiting the success of a potentially curative transplant. Several microRNAs (miRNAs) have recently been shown to impact the biology of GVHD. They are molecular regulators involved in numerous processes during T-cell development, homeostasis, and activation, and contribute to the pathological function of T-cells during GvHD. Here, we review the key role of miRNAs contributing to the GvHD; their detection might be an interesting possibility in the early diagnosis and monitoring of disease.

Clinical Significance of microRNAs in Hematologic Malignancies and Hematopoietic Stem Cell Transplantation

Hematologic malignancies are a group of neoplastic conditions that can develop from any stage of the hematopoiesis cascade. Small non-coding microRNAs (miRNAs) play a crucial role in the post-transcriptional regulation of gene expression. Mounting evidence highlights the role of miRNAs in malignant hematopoiesis via the regulation of oncogenes and tumor suppressors involved in proliferation, differentiation, and cell death. In this review, we provide current knowledge about dysregulated miRNA expression in the pathogenesis of hematological malignancies. We summarize data about the clinical utility of aberrant miRNA expression profiles in hematologic cancer patients and their associations with diagnosis, prognosis, and the monitoring of treatment response. Moreover, we will discuss the emerging role of miRNAs in hematopoietic stem cell transplantation (HSCT), and severe post-HSCT complications, such as graft-versus-host disease (GvHD). The therapeutical potential of the miRNA-based approach in hemato-oncology will be outlined, including studies with specific antagomiRs, mimetics, and circular RNAs (circRNAs). Since hematologic malignancies represent a full spectrum of disorders with different treatment paradigms and prognoses, the potential use of miRNAs as novel diagnostic and prognostic biomarkers might lead to improvements, resulting in a more accurate diagnosis and better patient outcomes.

Dynamic interplay of microRNA in diseases and therapeutic

MicroRNAs are the major class of small non-coding RNAs, evolutionary conserved post-transcriptional regulators of gene expression. Since their discovery in 1993, they have been implicated as master regulators in numerous cellular processes. MicroRNA (miRNA)s regulate gene expression by attenuation and/or mRNA degradation and are commonly associated with cell development, differentiation, and homeostasis. Extensive research in past two decades has provided new insights into the potential implications of miRNA in the onset, progression, and therapeutic nature of miRNAs in disease manifestation. Owing to the novel discoveries, "miRNAs" would probably pave a new direction in therapeutic research. However, "micro" in length miRNAs have attracted considerable attention in numerous other fields. Understanding the functionality of miRNAs, in this review article, we discussed the mechanistic role of miRNAs in human diseases and have outlined most of the recent published work in clinical therapeutics. We have constructed different network models for miRNA and its targets which made us understand their interrelationship and association with diseases. Future research would surely overcome challenges and would introduce new strategies for the utility of miRNAs in a broader setting.

Multiplexed Detection of Molecular Interactions with DNA Origami Engineered Cells in 3D Collagen Matrices

The interactions of cells with signaling molecules present in their local microenvironment maintain cell proliferation, differentiation, and spatial organization and mediate progression of diseases such as metabolic disorders and cancer. Real-time monitoring of the interactions between cells and their extracellular ligands in a three-dimensional (3D) microenvironment can inform detection and understanding of cell processes and the development of effective therapeutic agents. DNA origami technology allows for the design and fabrication of biocompatible and 3D functional nanodevices via molecular self-assembly for various applications including molecular sensing. Here, we report a robust method to monitor live cell interactions with molecules in their surrounding environment in a 3D tissue model using a microfluidic device. We used a DNA origami cell sensing platform (CSP) to detect two specific nucleic acid sequences on the membrane of B cells and dendritic cells. We further demonstrated real-time detection of biomolecules with the DNA sensing platform on the surface of dendritic cells in a 3D microfluidic tissue model. Our results establish the integration of live cells with membranes engineered with DNA nanodevices into microfluidic chips as a highly capable biosensor approach to investigate subcellular interactions in physiologically relevant 3D environments under controlled biomolecular transport.

Noncoding RNAs in diagnosis and prognosis of graft-versus-host disease (GVHD)

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a functional therapy for a plethora of hematologic malignancies and immune disorders. Graft-versus-host disease (GVHD), on the other hand, is one of the major complications ahead of a successful HSCT, contributing to transplant-associated morbidity and mortality. Notably, little is known about the underlying mechanism of this event; therefore, exploring precise biomarkers and uncovering the molecular pathogenesis of GVHD is valuable for early diagnosis and treatment optimization. Thanks to the advances in sequencing techniques, the noncoding sequences of the human genome-formerly considered "junk"-are now identified as functional molecules. Noncoding RNAs (ncRNA) control cellular responses by regulating gene expression, and previous studies have shown that these tiny molecules, especially microRNAs (miRNAs), can affect allogeneic T cell responses in both animal models and clinical experiments. The present study gives an overview of the functions of various miRNAs in regulating T cell responses in GVHD. We also provide an outlook on miRNAs and long noncoding RNAs (lncRNAs) potential role in GVHD with the hope of providing a future research direction for expanding their application as the sensitive and noninvasive diagnostic or prognostic biomarkers and also the promising therapeutic targets for improving outcomes after allogeneic HSCT.

MicroRNA-31 regulates T-cell metabolism via HIF1α and promotes chronic GVHD pathogenesis in mice

Chronic graft-versus-host disease (cGVHD) remains a major obstacle impeding successful allogeneic hematopoietic cell transplantation (HCT). MicroRNAs (miRs) play key roles in immune regulation during acute GVHD development. Preclinical studies to identify miRs that affect cGVHD pathogenesis are required to develop these as potential lifesaving interventions. Using oligonucleotide array, we identified miR-31, which was significantly elevated in allogeneic T cells after HCT in mice. Using genetic and pharmacologic approaches, we demonstrated a key role for miR-31 in mediating donor T-cell pathogenicity in cGVHD. Recipients of miR-31-deficient T cells displayed improved cutaneous and pulmonary cGVHD. Deficiency of miR-31 reduced T-cell expansion and T helper 17 (Th17) cell differentiation but increased generation and function of regulatory T cells (Tregs). MiR-31 facilitated neuropilin-1 downregulation, Foxp3 loss, and interferon-γ production in alloantigen-induced Tregs. Mechanistically, miR-31 was required for hypoxia-inducible factor 1α (HIF1α) upregulation in allogeneic T cells. Therefore, miR-31-deficient CD4 T cells displayed impaired activation, survival, Th17 cell differentiation, and glycolytic metabolism under hypoxia. Upregulation of factor-inhibiting HIF1, a direct target of miR-31, in miR-31-deficient T cells was essential for attenuating T-cell pathogenicity. However, miR-31-deficient CD8 T cells maintained intact glucose metabolism, cytolytic activity, and graft-versus-leukemia response. Importantly, systemic administration of a specific inhibitor of miR-31 effectively reduced donor T-cell expansion, improved Treg generation, and attenuated cGVHD. Taken together, miR-31 is a key driver for T-cell pathogenicity in cGVHD but not for antileukemia activity. MiR-31 is essential in driving cGVHD pathogenesis and represents a novel potential therapeutic target for controlling cGVHD.

A comprehensive study to delineate the role of an extracellular vesicle-associated microRNA-29a in chronic methamphetamine use disorder

Extracellular vesicles (EVs), which express a repertoire of cargo molecules (cf. proteins, microRNA, lipids, etc.), have been garnering a prominent role in the modulation of several cellular processes. Here, using both non-human primate and rodent model systems, we provide evidence that brain-derived EV (BDE) miRNA, miR-29a-3p (mir-29a), is significantly increased during chronic methamphetamine (MA) exposure. Further, miR-29a levels show significant increase both with drug-seeking and reinstatement in a rat MA self-administration model. We also show that EV-associated miR-29a is enriched in EV pool comprising of small EVs and exomeres and further plays a critical role in MA-induced inflammation and synaptodendritic damage. Furthermore, treatment with the anti-inflammatory drug ibudilast (AV411), which is known to reduce MA relapse, decreased the expression of miR-29a and subsequently attenuated inflammation and rescued synaptodendritic injury. Finally, using plasma from MUD subjects, we provide translational evidence that EV-miR29a could potentially serve as a biomarker to detect neuronal damage in humans diagnosed with MA use disorder (MUD). In summary, our work suggests that EV-associated miR-29a-3p plays a crucial role in MUD and might be used as a potential blood-based biomarker for detecting chronic inflammation and synaptic damage.

Serum small extracellular vesicles promote M1 activation of microglia after cerebral ischemia/reperfusion injury

Microglial M1 activation is detrimental to stroke outcomes. Recent studies have shown that circulating small extracellular vesicles (sEVs) can deliver miRNAs to target cells and regulate recipient cell functions. Herein, we tested the hypothesis that miRNA delivery by serum sEVs after cerebral ischemia/reperfusion (I/R) injury promote microglial M1 activation, demonstrating that serum sEVs from middle cerebral artery occlusion (MCAO) mice promoted proliferation and M1 activation of BV2 microglia. To explore the underlying mechanism of serum sEVs-mediated microglial activation in the early phase of cerebral I/R injury, we examined the effects of ischemic brain injury on the serum sEVs miRNAs profile in a mouse MCAO model using small RNAseq. Of the 1257 detected miRNA replications, the levels of 72 were significantly modulated. Bioinformatics analysis revealed that a panel of miRNAs was closely associated with inflammation, and in vitro experiments demonstrated that serum sEVs from MCAO mice could effectively transfer inflammatory miRNAs to BV2 microglia. Collectively, our data suggested that miRNAs delivered by serum sEVs after cerebral I/R injury promoted microglial M1 activation. The identification of microglial activation regulators in future studies will give rise to more effective treatments for stroke.

Classical and noncanonical functions of miRNAs in cancers

Alterations in microRNAs (miRNAs) expression are causative in the initiation and progression of human cancers. The molecular events responsible for the widespread differential expression of miRNAs in malignancy are exemplified by their location in cancer-associated genomic regions, epigenetic mechanisms, transcriptional dysregulation, chemical modifications and editing, and alterations in miRNA biogenesis proteins. The classical miRNA function is synonymous with post-transcriptional repression of target protein genes. However, several studies have reported miRNAs functioning outside this paradigm and some of these novel modes of regulation of gene expression have been implicated in cancers. Here, we summarize key aspects of miRNA involvement in cancer, with a special focus on these lesser-studied mechanisms of action.

Immunomodulatory Role and Therapeutic Potential of Non-Coding RNAs Mediated by Dendritic Cells in Autoimmune and Immune Tolerance-Related Diseases

Dendritic cells (DCs) are professional antigen-presenting cells that act as a bridge between innate immunity and adaptive immunity. After activation, DCs differentiate into subtypes with different functions, at which point they upregulate co-stimulatory molecules and produce various cytokines and chemokines. Activated DCs also process antigens for presentation to T cells and regulate the differentiation and function of T cells to modulate the immune state of the body. Non-coding RNAs, RNA transcripts that are unable to encode proteins, not only participate in the pathological mechanisms of autoimmune-related diseases but also regulate the function of immune cells in these diseases. Accumulating evidence suggests that dysregulation of non-coding RNAs contributes to DC differentiation, functions, and so on, consequently producing effects in various autoimmune diseases. In this review, we summarize the main non-coding RNAs (miRNAs, lncRNAs, circRNAs) that regulate DCs in pathological mechanisms and have tremendous potential to give rise to novel therapeutic targets and strategies for multiple autoimmune diseases and immune tolerance-related diseases.

Circulating miR-455-3p, miR-5787, and miR-548a-3p as potential noninvasive biomarkers in the diagnosis of acute graft-versus-host disease: a validation study

Currently, acute graft-versus-host disease (aGVHD) diagnosis is based on clinical features and pathological findings. Until now, there is no non-invasive diagnostic test for aGVHD. MicroRNAs may act as promising predictive, diagnostic, or prognostic biomarkers for aGVHD. The purpose of the current study was to validate circulating microRNAs as diagnostic biomarkers to assist clinicians in promptly diagnosing aGVHD, so that treatment can be initiated earlier. In the present study, we evaluated six microRNAs (miR-455-3p, miR-5787, miR-6729-5p, miR-6776-5p, miR-548a-3p, and miR-6732-5p) selected from miRNA array data in 40 aGVHD patients compared to 40 non-GVHD patients with RT-qPCR. Target genes of differentially expressed microRNAs (DEMs) were predicted using Targetscan, miRanda, miRDB, miRWalk, PICTAR5, miRmap, DIANA, and miRTarBase algorithms, and their functions were analyzed using EnrichNet, Metascape, and DIANA-miRPath databases. The expressions of plasma miR-455-3p and miR-5787 were significantly downregulated, whereas miR-548a-3p was significantly upregulated in aGVHD patients compared to non-GVHD patients. Moreover, DEMs showed potentially high diagnostic accuracy for aGVHD. In silico analysis of DEMs provided valuable information on the role of DEMs in GVHD, immune regulation, and inflammatory response. Our study suggested that miR-455-3p, miR-5787, and miR-548a-3p could be used as potential noninvasive biomarkers in the diagnosis of aGVHD in addition to possible therapeutic targets in aGVHD.

Interaction between non-coding RNAs and Toll-like receptors

Toll-like receptors (TLRs) are a large group of pattern recognition receptors which are involved in the regulation of innate immune responses. Based on the interplay between TLRs and adapter molecules, two distinctive signaling cascades, namely the MyD88-dependent and TRIF-dependent pathways have been recognized. TLRs are involved in the development of a wide variety of diseases including cancer and autoimmune disorders. A large body of evidence has shown interaction between two classes of non-coding RNAs, namely microRNAs (miRNAs) and long noncoding RNAs (lncRNAs). These interactions have prominent roles in the pathogenesis of several disorders including infectious disorders, autoimmune conditions and neoplastic disorders. This review aims at description of the interaction between these non-coding RNAs and TLRs.

Inflammation-related microRNAs are involved in stressful life events exposure and in trauma-focused psychotherapy in treatment-resistant depressed patients

BACKGROUND

About 30% of major depressive disorder (MDD) patients are classified as resistant to treatment (treatment-resistant depression, TRD). Among the factors associated with unfavourable treatment outcomes, stressful life events play a relevant role, and trauma-focused psychotherapy has been successfully proposed for the treatment of patients with a history of such events. Stressful experiences are related to enhanced inflammation and, recently, microRNAs (miRNAs) have emerged as potential mediators of the association between these experiences and psychiatric disorders. To date, no study has explored the effects of stressful life events on miRNAs in MDD patients.

OBJECTIVE

The objective of the present study was to assess possible miRNA blood expression alterations in TRD patients induced by the exposure to stressful life events and to investigate the effects of trauma-focused psychotherapy on the expression profiles of the same miRNAs, as well as their possible predictivity in relation to therapy outcome.

METHOD

The basal levels (T0) of seven candidate miRNAs (miR-15a/miR-29a/miR-125b/miR-126/miR-146a/miR-195/let-7f) were measured in the whole blood of 41 TRD patients. A subgroup of patients (n = 21) underwent trauma-focused psychotherapy; for all of them, miRNA levels were also longitudinally assessed (T4: after 4 weeks of treatment; T8: end of treatment; T12: follow-up visit), contextually to clinical evaluations.

RESULTS

miR-146a levels negatively correlated with recent stressful life event scores (p = .001), whereas the levels of miR-15a, miR-29a, miR-126, miR-195, and let-7f changed during the psychotherapy (best p = 1.98*10^-9). miR-29a was also identified as a response predictor, with lower baseline levels predicting non-response (p = .019) or worse improvement in mood symptoms (p = .032).

CONCLUSIONS

The study results could contribute to clarify the underlying molecular mechanisms and to identify novel biomarkers of stressful experiences and response to targeted treatments.

Potential Novel Biomarkers in Chronic Graft-Versus-Host Disease

Prognostic, diagnostic or predictive biomarkers are urgently needed for assessment of chronic graft-versus-host disease (cGvHD), a major risk for patients undergoing allogeneic hematopoietic stem cell transplantation. The main goal of this review generated within the COST Action EUROGRAFT "Integrated European Network on Chronic Graft Versus Host Disease" was to identify potential novel biomarkers for cGvHD besides the widely accepted molecular and cellular biomarkers. Thus, the focus was on cellular biomarkers, alloantibodies, glycomics, endothelial derived particles, extracellular vesicles, microbiome, epigenetic and neurologic changes in cGvHD patients. Both host-reactive antibodies in general, and particularly alloantibodies have been associated with cGvHD and require further consideration. Glycans attached to IgG modulate its activity and represent a promising predictive and/or stratification biomarker for cGVHD. Furthermore, epigenetic changes such as microRNAs and DNA methylation represent potential biomarkers for monitoring cGvHD patients and novel targets for developing new treatment approaches. Finally, the microbiome likely affects the pathophysiology of cGvHD; bacterial strains as well as microbial metabolites could display potential biomarkers for dysbiosis and risk for the development of cGvHD. In summary, although there are no validated biomarkers currently available for clinical use to better inform on the diagnosis, prognosis or prediction of outcome for cGvHD, many novel sources of potential markers have shown promise and warrant further investigation using well characterized, multi-center patient cohorts.

Infection-induced 5'-half molecules of tRNAHisGUG activate Toll-like receptor 7

Toll-like receptors (TLRs) play a crucial role in the innate immune response. Although endosomal TLR7 recognizes single-stranded RNAs, their endogenous RNA ligands have not been fully explored. Here, we report 5'-tRNA half molecules as abundant activators of TLR7. Mycobacterial infection and accompanying surface TLR activation up-regulate the expression of 5'-tRNA half molecules in human monocyte-derived macrophages (HMDMs). The abundant accumulation of 5'-tRNA halves also occur in HMDM-secreted extracellular vehicles (EVs); the abundance of EV-5'-tRNAHisGUG half molecules is >200-fold higher than that of the most abundant EV-microRNA (miRNA). Sequence identification of the 5'-tRNA halves using cP-RNA-seq revealed abundant and selective packaging of specific 5'-tRNA half species into EVs. The EV-5'-tRNAHisGUG half was experimentally demonstrated to be delivered into endosomes in recipient cells and to activate endosomal TLR7. Up-regulation of the 5'-tRNA half molecules was also observed in the plasma of patients infected with Mycobacterium tuberculosis. These results unveil a novel tRNA-engaged pathway in the innate immune response and assign the role of "immune activators" to 5'-tRNA half molecules.

Distinct microRNA expression profiles in saliva and salivary gland tissue differentiate patients with primary Sjögren's syndrome from non-Sjögren's sicca patients

OBJECTIVES

Increasing evidence suggests that aberrant expression of microRNAs (miRNAs) is involved in the pathogenesis of primary Sjögren's syndrome (pSS). The aim was thus to characterize the miRNA profile in saliva, salivary gland tissue, and plasma from patients with pSS and compare findings with those of patients having Sjögren-like disease (non-pSS). In addition, to correlate miRNA levels and clinicopathological features of pSS.

METHODS

miRNA real-time quantitative polymerase chain reaction was performed on saliva, plasma, and salivary gland tissue samples from 24 patients with pSS and 16 non-pSS in 384-well plates. T test was used for comparison of miRNA profiles, followed by Benjamini-Hochberg correction. The discriminatory power of miRNAs was evaluated by receiver-operating characteristic curves, and Pearson/Spearman correlation was used for correlation analyses.

RESULTS

In saliva, 14 miRNAs were significantly differentially expressed between pSS and non-pSS, including downregulation of the miR-17 family in pSS. In salivary gland tissue of patients with pSS, miR-29a-3p was significantly upregulated. Plasma miRNAs did not differ between the two groups, although the miR-17 family tended to be downregulated. The combination of miR-17-5p and let-7i-5p in saliva yielded an area under curve of 97% (CI 92%-100%). Several miRNAs correlated significantly with one another and with salivary flow rates and histopathology.

CONCLUSION

Our findings indicate that the miRNA expression profile in saliva may enable to discriminate between pSS and non-pSS patients. However, further validation in larger cohorts is needed as well as functional analyses of the miRNAs of interest.

Serum MicroRNA on inflammation: a literature review of mouse model studies

MicroRNAs (miRNAs) are small non-coding RNA molecules that regulate target gene expression by binding to sequences in messenger RNA processing. Inflammation is a protective reaction from harmful stimuli. MiRNAs can be biomarkers of diseases related to inflammation and are widely expressed in serum. However, overall changes in serum miRNA levels during inflammation have yet to be observed. Here, we selected studies published until 20 January 2020 that examined miRNAs in mouse models of inflammation. Serum microRNA, inflammation, inflammatory and mouse were used as search terms to select articles from PubMed and MEDLINE. Among the articles, sepsis and 18 related miRNAs were mainly examined. Eleven miRNAs were related to brain disease and 10 with fibrosis. Seventeen injury-induced inflammatory disease studies were included, as well as other inflammatory diseases, such as metabolic disease, vascular disease, arthritis, asthma, autoimmune disease, inflammatory bowel disease, and thyroiditis. The data described miRNA-associated downstream pathways associated with inflammation as well as mitochondrial responses, oxidative responses, apoptosis, cell signalling, and cell differentiation. We expect that the data will inform future animal inflammation-related miRNA studies.

Novel Biomarkers for Outcome After Allogeneic Hematopoietic Stem Cell Transplantation

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a well-established curative treatment for various malignant hematological diseases. However, its clinical success is substantially limited by major complications including graft-vs.-host disease (GVHD) and relapse of the underlying disease. Although these complications are known to lead to significant morbidity and mortality, standardized pathways for risk stratification of patients undergoing allo-HSCT are lacking. Recent advances in the development of diagnostic and prognostic tools have allowed the identification of biomarkers in order to predict outcome after allo-HSCT. This review will provide a summary of clinically relevant biomarkers that have been studied to predict the development of acute GVHD, the responsiveness of affected patients to immunosuppressive treatment and the risk of non-relapse mortality. Furthermore, biomarkers associated with increased risk of relapse and subsequent mortality will be discussed.

Toll-like receptor signaling in hematopoietic stem and progenitor cells

PURPOSE OF REVIEW

The innate immune system is essential in the protection against microbial infection and facilitating tissue repair mechanisms. During these stresses, the maintenance of innate immune cell numbers through stress-induced or emergency hematopoiesis is key for our survival. One major mechanism to recognize danger signals is through the activation of Toll-like receptors (TLRs) on the surface of hematopoietic cells, including hematopoietic stem cell (HSC) and hematopoietic progenitor cell (HPC), and nonhematopoietic cells, which recognize pathogen-derived or damaged-induced compounds and can influence the emergency hematopoietic response. This review explores how direct pathogen-sensing by HSC/HPC regulates hematopoiesis, and the positive and negative consequences of these signals.

RECENT FINDINGS

Recent studies have highlighted new roles for TLRs in regulating HSC and HPC differentiation to innate immune cells of both myeloid and lymphoid origin and augmenting HSC and HPC migration capabilities. Most interestingly, new insights as to how acute versus chronic stimulation of TLR signaling regulates HSC and HPC function has been explored.

SUMMARY

Recent evidence suggests that TLRs may play an important role in many inflammation-associated diseases. This suggests a possible use for TLR agonists or antagonists as potential therapeutics. Understanding the direct effects of TLR signaling by HSC and HPC may help regulate inflammatory/danger signal-driven emergency hematopoiesis.

MicroRNAs as Potential Diagnostic, Prognostic, and Predictive Biomarkers for Acute Graft-versus-Host Disease

Successful treatment of various hematologic diseases with allogeneic hematopoietic stem cell transplantation is often limited due to the occurrence of acute graft-versus-host disease (aGVHD). So far, there are no approved molecular biomarkers for the diagnosis and prediction of aGVHD at the clinical level due to our incomplete understanding of the molecular biology of the disease. Various studies have been conducted on animal models and humans to investigate the role of microRNAs in aGVHD pathogenesis to implicate them as biomarkers and therapeutic targets. Because of their high stability, tissue specificity, ease of measurement, low cost, and simplicity, they are excellent targets for biomarkers. In this review, we focused on microRNA expression profiling studies that were performed recently in both animal models and human cases of aGVHD to identify diagnostic and predictive biomarkers for this disease. The expression pattern of microRNAs can be specific to cells and tissues. Because aGVHD affects several organs, microRNA signatures in target tissues may help to understand the molecular pathology of the disease. Identification of organ-specific microRNAs in aGVHD can be promising to categorize patients for organ-specific therapies. Thus, microRNAs can be used as noninvasive diagnostic tests in clinic to improve prophylaxis, predict incidence and severity, and reduce morbidity.

Extracellular miRNAs as activators of innate immune receptors

Since the discovery of the existence of microRNAs (miRNAs) in body fluids, the fascinating hypothesis that extracellular miRNAs may play a role in cell-to-cell signalling started to make its own way. In this review, we summarize the current knowledge that supports the role of miRNAs in the regulation of the immune response by an unconventional mechanism based on the activation of intracellular innate immune sensors of nucleic acids, namely the Toll-like receptors (TLRs). Such a mechanism of action has been now described to amplify and influence the pathogenesis of several inflammation-dependent pathological conditions, including cancer growth and metastasis, neurodegeneration, autoimmunity and cardiovascular diseases. The available data suggest that we have only begun to touch upon a complex system that is likely to involve many receptors and molecules. These findings may help to understand the pathogenesis of immune-mediated diseases and provide the basis for the identification of new potential therapeutic targets.

Cancer Exosomes as Conveyors of Stress-Induced Molecules: New Players in the Modulation of NK Cell Response

Natural killer (NK) cells are innate lymphoid cells that play a pivotal role in tumor surveillance. Exosomes are nanovesicles released into the extracellular environment via the endosomal vesicle pathway and represent an important mode of intercellular communication. The ability of anticancer chemotherapy to enhance the immunogenic potential of malignant cells mainly relies on the establishment of the immunogenic cell death (ICD) and the release of damage-associated molecular patterns (DAMPs). Moreover, the activation of the DNA damage response (DDR) and the induction of senescence represent two crucial modalities aimed at promoting the clearance of drug-treated tumor cells by NK cells. Emerging evidence has shown that stress stimuli provoke an increased release of exosome secretion. Remarkably, tumor-derived exosomes (Tex) produced in response to stress carry distinct type of DAMPs that activate innate immune cell populations. Moreover, stress-induced ligands for the activating receptor NKG2D are transported by this class of nanovesicles. Here, we will discuss how Tex interact with NK cells and provide insight into their potential role in response to chemotherapy-induced stress stimuli. The capability of some "danger signals" carried by exosomes that indirectly affect the NK cell activity in the tumor microenvironment will be also addressed.

Toll-Like Receptor Stimulation by MicroRNAs in Acute Graft-vs.-Host Disease

Acute graft-vs.-host disease (aGVHD) is a frequent complication of allogeneic hematopoietic stem cell transplantation (allo-HSCT), accounting for substantial morbidity and mortality associated with this treatment modality. The pathogenesis of aGVHD involves a complex cascade of humoral and cellular interactions in which donor T cells target HLA mismatched host tissues, causing tissue injury through secretion of pro-inflammatory cytokines and induction of direct cytotoxicity. Toll-like receptors (TLRs) are key components of the innate immune system that recognize endogenous danger-associated molecular patterns (DAMPs) and exogenous pathogen-associated molecular patterns (PAMPs). Patients receiving conditioning chemotherapy and/or whole-body irradiation prior to all-HSCT are prone to gastrointestinal damage and translocation of microbiota across compromised intestinal epithelium, resulting in release of PAMPs and DAMPs. These “danger signals” play critical roles in disease pathogenesis by both initiating and propagating aGVHD through dendritic cell maturation and alloreactive T cell responses. There are 10–15 TLRs identified in mammalian species, a subset of which recognize single-stranded RNA (ssRNA) and serve as a key component of viral immunity. Recently, ssRNAs other than those of viral origin have been investigated as potential ligands of TLRs. MicroRNAs (miRs) are short (19–24 nt) non-coding RNAs that play critical roles in a variety of diseases. While traditionally miRs post-translationally modulate gene expression, non-canonical functions such as regulating TLR stimulation by acting as TLR ligands have been described. Here, we review the role of TLRs in aGVHD pathogenesis, the function of miRs in TLR stimulation, and the recent literature describing miRs as TLR ligands in aGVHD.

Exosome-delivered microRNAs promote IFN-α secretion by human plasmacytoid DCs via TLR7

The excessive production of type I IFNs is a hallmark and a main pathogenic mechanism of many autoimmune diseases, including systemic lupus erythematosus (SLE). In these pathologies, the sustained secretion of type I IFNs is dependent on the improper activation of plasmacytoid DCs (pDCs) by self-nucleic acids. However, the nature and origin of pDC-activating self-nucleic acids is still incompletely characterized. Here, we report that exosomes isolated from the plasma of SLE patients can activate the secretion of IFN-α by human blood pDCs in vitro. This activation requires endosomal acidification and is recapitulated by microRNAs isolated from exosomes, suggesting that exosome-delivered microRNAs act as self-ligands of innate single-stranded endosomal RNA sensors. By using synthetic microRNAs, we identified an IFN induction motif that is responsible for the TLR7-dependent activation, maturation, and survival of human pDCs. These findings identify exosome-delivered microRNAs as potentially novel TLR7 endogenous ligands able to induce pDC activation in SLE patients. Therefore, microRNAs may represent novel pathogenic mediators in the onset of autoimmune reactions and potential therapeutic targets in the treatment of type I IFN-mediated diseases.

Detection of miR‑29a in plasma of patients with lumbar spinal stenosis and the clinical significance

The present study aimed to detect miR-29a expression in the plasma of patients with lumbar spinal stenosis (LSS) and to investigate the clinical significance. A total of 30 patients with LSS, 27 patients with lumbar intervertebral disc herniation (LDH), 27 healthy people and 7 patients that had succumbed to mortality were involved in the present study for specimen collection. Expression levels of miR-29a in plasma and intervertebral disc tissue were detected by reverse transcription-quantitative polymerase chain reaction analysis. Plasma expression levels of matrix metalloproteinase 9 (MMP9) and a disintegrin and metalloproteinase with thrombospondin motifs 5 (ADAMTS5) were detected ELISA. The expression levels of MMP9 and ADAMTS5 protein were detected by western blotting. Pearson correlation analysis was used to analyze the correlations between the expression levels of microRNA (miR)-29a, MMP9 and ADAMTS5. Receiver operating characteristic curve analysis was used to analyze the possibility of the use of miR-29a as a biomarker of LSS. The expression levels of miR-29a in plasma and intervertebral disc tissue of patients with LSS were significantly lower in patients with LSS compared with in patients with LDH, as well as healthy controls. Conversely, the protein expression levels of MMP9 and ADAMTS5 were significantly higher in patients with LSS compared with patients with LDH, as well as healthy controls. The expression levels of miR-29a was negatively correlated with the expression levels of MMP9 and ADAMTS5. In addition, miR-29a demonstrated low temperature sensitivity and high freeze-thaw stability, and may be used to accurately diagnose LSS. Therefore, miR-29a may be considered to be a potential biomarker of LSS.

MicroRNA-155 Modulates Acute Graft-versus-Host Disease by Impacting T Cell Expansion, Migration, and Effector Function

MicroRNA-155 (miR-155) is a small noncoding RNA critical for the regulation of inflammation as well as innate and adaptive immune responses. MiR-155 has been shown to be dysregulated in both donor and recipient immune cells during acute graft-versus-host disease (aGVHD). We previously reported that miR-155 is upregulated in donor T cells of mice and humans with aGVHD and that mice receiving miR-155-deficient (miR155^-/-) splenocytes had markedly reduced aGVHD. However, molecular mechanisms by which miR-155 modulates T cell function in aGVHD have not been fully investigated. We identify that miR-155 expression in both donor CD8⁺ T cells and conventional CD4⁺ CD25^- T cells is pivotal for aGVHD pathogenesis. Using murine aGVHD transplant experiments, we show that miR-155 strongly impacts alloreactive T cell expansion through multiple distinct mechanisms, modulating proliferation in CD8⁺ donor T cells and promoting exhaustion in donor CD4⁺ T cells in both the spleen and colon. Additionally, miR-155 drives a proinflammatory Th1 phenotype in donor T cells in these two sites, and miR-155^-/- donor T cells are polarized toward an IL-4-producing Th2 phenotype. We further demonstrate that miR-155 expression in donor T cells regulates CCR5 and CXCR4 chemokine-dependent migration. Notably, we show that miR-155 expression is crucial for donor T cell infiltration into multiple target organs. These findings provide further understanding of the role of miR-155 in modulating aGVHD through T cell expansion, effector cytokine production, and migration.

The search for drug-targetable diagnostic, prognostic and predictive biomarkers in chronic graft-versus-host disease

INTRODUCTION

Chronic graft-versus-host disease (cGVHD) continues to be the leading cause of late morbidity and mortality after allogeneic hematopoietic stem cell transplantation (allo-HSCT), which is an increasingly applied curative method for both benign and malignant hematologic disorders. Biomarker identification is crucial for the development of noninvasive and cost-effective cGVHD diagnostic, prognostic, and predictive test for use in clinic. Furthermore, biomarkers may help to gain a better insight on ongoing pathophysiological processes. The recent widespread application of omics technologies including genomics, transcriptomics, proteomics and cytomics provided opportunities to discover novel biomarkers. Areas covered: This review focuses on biomarkers identified through omics that play a critical role in target identification for drug development, and that were verified in at least two independent cohorts. It also summarizes the current status on omics tools used to identify these useful cGVHD targets. We briefly list the biomarkers identified and verified so far. We further address challenges associated to their exploitation and application in the management of cGVHD patients. Finally, insights on biomarkers that are drug targetable and represent potential therapeutic targets are discussed. Expert commentary: We focus on biomarkers that play an essential role in target identification.

MicroRNA-17-92 is required for T-cell and B-cell pathogenicity in chronic graft-versus-host disease in mice

Chronic graft-versus-host disease (cGVHD) is characterized as autoimmune-like fibrosis and antibody production mediated by pathogenic T cells and B cells. MicroRNA-17-92 (miR-17-92) influences the survival, differentiation, and function of lymphocytes in cancer, infections, and autoimmunity. To determine whether miR-17-92 regulates T- and B-cell responses in cGVHD, we generated mice conditionally deficient for miR-17-92 in T cells, B cells, or both. Using murine models of allogeneic bone marrow transplantation, we demonstrate that expression of miR-17-92 in donor T and B cells is essential for the induction of both scleroderma and bronchiolitis obliterans in cGVHD. Mechanistically, miR-17-92 expressed in T cells not only enhances the differentiation of pathogenic T helper 1 (Th1) and Th17 cells, but also promotes the generation of follicular Th cells, germinal center (GC) B cells, and plasma cells. In B cells, miR-17-92 expression is required for autoantibody production and immunoglobulin G deposition in the skin. Furthermore, we evaluated a translational approach using antagomirs specific for either miR-17 or miR-19, key members in miR-17-92 cluster. In a lupus-like cGVHD model, systemic administration of anti-miR-17, but not anti-miR-19, alleviates clinical manifestations and proteinuria incidence in recipients through inhibiting donor lymphocyte expansion, B-cell activation, and GC responses. Blockade of miR-17 also ameliorates skin damage by reducing Th17 differentiation in a scleroderma-cGVHD model. Taken together, our work reveals that miR-17-92 is required for T-cell and B-cell differentiation and function, and thus for the development of cGVHD. Furthermore, pharmacological inhibition of miR-17 represents a potential therapeutic strategy for the prevention of cGVHD.

The Role of MicroRNAs in Myeloid Cells during Graft-versus-Host Disease

The successful treatment of various hematologic diseases with allogeneic hematopoietic cell transplantation is often limited by the occurrence of graft-versus-host disease (GvHD). Several microRNAs (miRs) have recently been shown to impact the biology of GvHD by regulating pro- as well as anti-inflammatory target genes. There is increasing evidence that a single miR can have different effects by preferentially targeting certain genes depending on the cell type that the miR is analyzed in. This review will focus on the role of miRs in myeloid cells during the development of acute and chronic GvHD and autoimmune diseases. Because miRs act on the expression of multiple target genes and may thereby influence the immune system at different functional levels, they are potentially attractive targets for the modification of allogeneic immune responses using miR mimics and inhibitors.

MicroRNAs and miRceptors: a new mechanism of action for intercellular communication

MicroRNAs (miRs) are small non-coding RNAs (ncRNAs) that control the expression of target genes by modulating (usually inhibiting) their translation into proteins. This 'traditional' mechanism of action of miRs has been recently challenged by new discoveries pointing towards a role of miRs as 'hormones', capable of binding to proteic receptors (miRceptors) and triggering their downstream signalling pathways. These findings harbour particular significance within the tumour microenvironment (TME), defined as the variety of non-cancerous cells surrounding cancer cells, but are relevant also for other diseases. In recent years it has become clearer that the TME does not passively assist the growth of cancer cells but contributes to its biology. Some of the mediators of the intercellular communication between cancer cells and TME are miRs shuttled within exosomes, a subtype of cellular released extracellular vesicles. This article will highlight the most recent findings on the biological implications of miR-miRceptor interactions for the biology of the TME and other diseases, and will provide some perspectives on the future development of this fascinating research.This article is part of the discussion meeting issue 'Extracellular vesicles and the tumour microenvironment'.

Liquid Biopsy: From Basic Research to Clinical Practice

Liquid biopsy refers to the molecular analysis in biological fluids of nucleic acids, subcellular structures, especially exosomes, and, in the context of cancer, circulating tumor cells. In the last 10 years, there has been an intensive research in liquid biopsy to achieve a less invasive and more precise personalized medicine. Molecular assessment of these circulating biomarkers can complement or even surrogate tissue biopsy. Because of this research, liquid biopsy has been introduced in clinical practice, especially in oncology, prenatal screening, and transplantation. Here we review the biology, methodological approaches, and clinical applications of the main biomarkers involved in liquid biopsy.

Inhibition of retroviral Gag assembly by non-silencing miRNAs promotes autophagic viral degradation

We recently reported an unconventional mechanism by which miRNAs inhibit HIV-1 viral production. This occurs when miRNAs bind nonspecifically to the viral structural protein Gag, interfering with viral RNA-mediated Gag assembly at the plasma membrane. Consequently, misassembled viral complexes are redirected into the endocytic pathway where they are delivered to lysosomes for degradation. In this study, we demonstrate that autophagy is a critical mediator of the viral degradation pathway and that this pathway is not HIV-1 specific. Misassembled viral complexes were found to colocalize extensively with LC3 and p62 in late endosomes/lysosomes, demonstrating a convergence of autophagy with functional degradative compartments. Knocking down autophagosome formation machineries reduced this convergence, while treatment with autophagy-inducer rapamycin enhanced the convergence. Furthermore, similar autophagy-dependent nonspecific miRNA inhibition of murine leukemia virus (MLV) assembly was shown. Overall, these results reveal autophagy as a crucial regulator of the retroviral degradation pathway in host cells initiated by nonspecific miRNA-Gag interactions. These findings could have significant implications for understanding how cells may regulate retroviral complex assembly by miRNA expression and autophagy, and raise the possibility that similar regulations can occur in other biological contexts.