Exosome microRNA signatures in patients with complex regional pain syndrome undergoing plasma exchange

miRNA packaging into small extracellular vesicles and implications in pain

Extracellular vesicles (EVs) are a heterogenous group of lipid bilayer bound particles naturally released by cells. These vesicles are classified based on their biogenesis pathway and diameter. The overlap in size of exosomes generated from the exosomal pathway and macrovesicles that are pinched off from the surface of the plasma membrane makes it challenging to isolate pure populations. Hence, isolated vesicles that are less than 200 nm are called small extracellular vesicles (sEVs). Extracellular vesicles transport a variety of cargo molecules, and multiple mechanisms govern the packaging of cargo into sEVs. Here, we discuss the current understanding of how miRNAs are targeted into sEVs, including the role of RNA binding proteins and EXOmotif sequences present in miRNAs in sEV loading. Several studies in human pain disorders and rodent models of pain have reported alterations in sEV cargo, including miRNAs. The sorting mechanisms and target regulation of miR-939, a miRNA altered in individuals with complex regional pain syndrome, is discussed in the context of inflammation. We also provide a broad overview of the therapeutic strategies being pursued to utilize sEVs in the clinic and the work needed to further our understanding of EVs to successfully deploy sEVs as a pain therapeutic.

Morphine-induced hyperalgesia impacts small extracellular vesicle miRNA composition and function

Morphine and other synthetic opioids are widely prescribed to treat pain. Prolonged morphine exposure can paradoxically enhance pain sensitivity in humans and nociceptive behavior in rodents. To better understand the molecular mechanisms underlying opioid-induced hyperalgesia, we investigated changes in miRNA composition of small extracellular vesicles (sEVs) from the serum of mice after a morphine treatment paradigm that induces hyperalgesia. We observed significant differential expression of 18 miRNAs in sEVs from morphine-treated mice of both sexes compared to controls. Several of these miRNAs were bioinformatically predicted to regulate cyclic AMP response element binding protein (CREB), a well-characterized transcription factor implicated in pain and drug addiction. We confirmed the binding and repression of Creb mRNA by miR-155 and miR-10a. We tested if serum-derived sEVs from morphine-treated mice could elicit nociceptive behavior in naïve recipient mice. Intrathecal injection of 1 μg sEVs did not significantly impact basal mechanical and thermal threshold in naïve recipient mice. However, prophylactic 1 μg sEV administration in recipient mice resulted in faster resolution of complete Freund's adjuvant-induced mechanical and thermal inflammatory hypersensitivity. Other behaviors assayed following administration of these sEVs were not impacted including sEV conditioned place preference and locomotor sensitization. These results indicate that morphine regulation of serum sEV composition can contribute to analgesia and suggest a potential for sEVs to be a non-opioid therapeutic intervention strategy to treat pain.

Mesenchymal Stem Cell-Derived Exosomes as Drug Delivery Vehicles in Disease Therapy

Exosomes are small vesicles containing proteins, nucleic acids, and biological lipids, which are responsible for intercellular communication. Studies have shown that exosomes can be utilized as effective drug delivery vehicles to accurately deliver therapeutic substances to target tissues, enhancing therapeutic effects and reducing side effects. Mesenchymal stem cells (MSCs) are a class of stem cells widely used for tissue engineering, regenerative medicine, and immunotherapy. Exosomes derived from MSCs have special immunomodulatory functions, low immunogenicity, the ability to penetrate tumor tissues, and high yield, which are expected to be engineered into efficient drug delivery systems. Despite the promising promise of MSC-derived exosomes, exploring their optimal preparation methods, drug-loading modalities, and therapeutic potential remains challenging. Therefore, this article reviews the related characteristics, preparation methods, application, and potential risks of MSC-derived exosomes as drug delivery systems in order to find potential therapeutic breakthroughs.

Pharmacotherapy for osteoarthritis-related pain: current and emerging therapies

INTRODUCTION

Osteoarthritis (OA) related pain has affected millions of people worldwide. However, the current pharmacological options for managing OA-related pain have not achieved a satisfactory effect.

AREAS COVERED

This narrative review provides an overview of the current and emerging drugs for OA-related pain. It covers the drugs' mechanism of action, safety, efficacy, and limitations. The National Library of Medicine (PubMed) database was primarily searched from 2000 to 2024.

EXPERT OPINION

Current treatment options are limited and suboptimal for OA pain management. Topical nonsteroidal anti-inflammatory drugs (NSAIDs) are the recognized and first-line treatment in the management of OA-related pain, and other drugs are inconsistent recommendations by guidelines. Emerging treatment options are promising for OA-related pain, including nerve growth factor (NGF) inhibitors, ion channel inhibitors, and calcitonin gene-related peptide (CGRP) antagonists. Besides, drugs repurposing from antidepressants and antiepileptic analgesics are shedding light on the management of OA-related pain. The management of OA-related pain is challenging as pain is heterogeneous and subjective. A more comprehensive strategy combined with non-pharmacological therapy needs to be considered, and tailored management options to individualized patients.

Markers of Tissue Deterioration and Pain on Earth and in Space

Purpose

Pain is an understudied physiological effect of spaceflight. Changes in inflammatory and tissue degradation markers are often associated with painful conditions. Our aim was to evaluate the changes in markers associated with tissue deterioration after a short-term spaceflight.

Patients and Methods

Plasma levels of markers for systemic inflammation and tissue degeneration markers were assessed in two astronauts before and within 24 h after the 17-day Axiom Space AX-1 mission.

Results

After the spaceflight, C-reactive protein (CRP) was reduced in both astronauts, while INFγ, GM-CSF, TNFα, BDNF, and all measured interleukins were consistently increased. Chemokines demonstrated variable changes, with consistent positive changes in CCL3, 4, 8, 22 and CXCL8, 9, 10, and consistent negative change in CCL8. Markers associated with tissue degradation and bone turnover demonstrated consistent increases in MMP1, MMP13, NTX and OPG, and consistent decreases in MMP3 and MMP9.

Conclusion

Spaceflight induced changes in the markers of systemic inflammation, tissue deterioration, and bone resorption in two astronauts after a short, 17-day, which were often consistent with those observed in painful conditions on Earth. However, some differences, such as a consistent decrease in CRP, were noted. All records for the effect of space travel on human health are critical for improving our understanding of the effect of this unique environment on humans.

DNA Methylation Changes in Blood Cells of Fibromyalgia and Chronic Fatigue Syndrome Patients

Purpose

Fibromyalgia (FM) and Chronic Fatigue Syndrome (CFS) affect 0.4% and 1% of society, respectively, and the prevalence of these pain syndromes is increasing. To date, no strong association between these syndromes and the genetic background of affected individuals has been shown. Therefore, it is plausible that epigenetic changes might play a role in the development of these syndromes.

Patients and Methods

Three previous studies have attempted to elaborate the involvement of genome-wide methylation changes in blood cells in the development of fibromyalgia and chronic fatigue syndrome. These studies included 22 patients with fibromyalgia and 127 patients with CFS, and the results of the studies were largely discrepant. Contradicting results of those studies may be attributed to differences in the omics data analysis approaches used in each study. We reanalyzed the data collected in these studies using an updated and coherent data-analysis framework.

Results

Overall, the methylation changes that we observed overlapped with previous results only to some extent. However, the gene set enrichment analyses based on genes annotated to methylation changes identified in each of the analyzed datasets were surprisingly coherent and uniformly associated with the physiological processes that, when affected, may result in symptoms characteristic of fibromyalgia and chronic fatigue syndrome.

Conclusion

Methylomes of the blood cells of patients with FM and CFS in three independent studies have shown methylation changes that appear to be implicated in the pathogenesis of these syndromes.

Complex Regional Pain Syndrome: Evidence-Based Advances in Concepts and Treatments

PURPOSE OF REVIEW

This review presents the most current information about the epidemiology of complex regional pain syndrome (CRPS), classification and diagnostic criteria, childhood CRPS, subtypes, pathophysiology, conventional and less conventional treatments, and preventive strategies.

RECENT FINDINGS

CRPS is a painful disorder with multifactorial pathophysiology. The data describe sensitization of the central and peripheral nervous systems, inflammation, possible genetic factors, sympatho-afferent coupling, autoimmunity, and mental health factors as contributors to the syndrome. In addition to conventional subtypes (type I and type II), cluster analyses have uncovered other proposed subtypes. Prevalence of CRPS is approximately 1.2%, female gender is consistently associated with a higher risk of development, and substantial physical, emotional, and financial costs can result from the syndrome. Children with CRPS seem to benefit from multifaceted physical therapy leading to a high percentage of symptom-free patients. The best available evidence along with standard clinical practice supports pharmacological agents, physical and occupational therapy, sympathetic blocks for engaging physical restoration, steroids for acute CRPS, neuromodulation, ketamine, and intrathecal baclofen as therapeutic approaches. There are many emerging treatments that can be considered as a part of individualized, patient-centered care. Vitamin C may be preventive. CRPS can lead to progressively painful sensory and vascular changes, edema, limb weakness, and trophic disturbances, all of which substantially erode healthy living. Despite some progress in research, more comprehensive basic science investigation is needed to clarify the molecular mechanisms of the disease so that targeted treatments can be developed for better outcomes. Incorporating a variety of standard therapies with different modes of action may offer the most effective analgesia. Introducing less conventional approaches may also be helpful when traditional treatments fail to provide sufficient improvement.

Current aspects of small extracellular vesicles in pain process and relief

Small extracellular vesicles (sEVs) have been identified as a noteworthy paracrine mechanism of intercellular communication in diagnosing and managing neurological disorders. Current research suggests that sEVs play a pivotal role in the pathological progression of pain, emphasizing their critical function in the pathological progression of pain in acute and chronic pain models. By facilitating the transfer of diverse molecules, such as proteins, nucleic acids, and metabolites, sEVs can modulate pain signaling transmission in both the central and peripheral nervous systems. Furthermore, the unique molecules conveyed by sEVs in pain disorders indicate their potential as diagnostic biomarkers. The application of sEVs derived from mesenchymal stem cells (MSCs) in regenerative pain medicine has emerged as a promising strategy for pain management. Moreover, modified sEVs have garnered considerable attention in the investigation of pathological processes and therapeutic interventions. This review presents a comprehensive overview of the current knowledge regarding the involvement of sEVs in pain pathogenesis and treatment. Nevertheless, additional research is imperative to facilitate their clinical implementation. Schematic diagram of sEVs in the biogenesis, signal transmission, diagnosis, and treatment of pain disorders. Small extracellular vesicles (sEVs) are secreted by multiple cells, loading with various biomolecules, such as miRNAs, transmembrane proteins, and amino acids. They selectively target other cells and regulating pain signal transmission. The composition of sEVs can serve as valuable biomarkers for pain diagnosis. In particular, mesenchymal stem cell-derived sEVs have shown promise as regenerative medicine for managing multiple pain disorders. Furthermore, by modifying the structure or contents of sEVs, they could potentially be used as a potent analgesic method.

Integrative miRNA-mRNA profiling of human epidermis: unique signature of SCN9A painful neuropathy

Personalized management of neuropathic pain is an unmet clinical need due to heterogeneity of the underlying aetiologies, incompletely understood pathophysiological mechanisms and limited efficacy of existing treatments. Recent studies on microRNA in pain preclinical models have begun to yield insights into pain-related mechanisms, identifying nociception-related species differences and pinpointing potential drug candidates. With the aim of bridging the translational gap towards the clinic, we generated a human pain-related integrative miRNA and mRNA molecular profile of the epidermis, the tissue hosting small nerve fibres, in a deeply phenotyped cohort of patients with sodium channel-related painful neuropathy not responding to currently available therapies. We identified four miRNAs strongly discriminating patients from healthy individuals, confirming their effect on differentially expressed gene targets driving peripheral sensory transduction, transmission, modulation and post-transcriptional modifications, with strong effects on gene targets including NEDD4. We identified a complex epidermal miRNA-mRNA network based on tissue-specific experimental data suggesting a cross-talk between epidermal cells and axons in neuropathy pain. Using immunofluorescence assay and confocal microscopy, we observed that Nav1.7 signal intensity in keratinocytes strongly inversely correlated with NEDD4 expression that was downregulated by miR-30 family, suggesting post-transcriptional fine tuning of pain-related protein expression. Our targeted molecular profiling advances the understanding of specific neuropathic pain fine signatures and may accelerate process towards personalized medicine in patients with neuropathic pain.

Regulation by noncoding RNAs of local translation, injury responses, and pain in the peripheral nervous system

Neuropathic pain is a chronic condition arising from damage to somatosensory pathways that results in pathological hypersensitivity. Persistent pain can be viewed as a consequence of maladaptive plasticity which, like most enduring forms of cellular plasticity, requires altered expression of specific gene programs. Control of gene expression at the level of protein synthesis is broadly utilized to directly modulate changes in activity and responsiveness in nociceptive pathways and provides an effective mechanism for compartmentalized regulation of the proteome in peripheral nerves through local translation. Levels of noncoding RNAs (ncRNAs) are commonly impacted by peripheral nerve injury leading to persistent pain. NcRNAs exert spatiotemporal regulation of local proteomes and affect signaling cascades supporting altered sensory responses that contribute to hyperalgesia. This review discusses ncRNAs found in the peripheral nervous system (PNS) that are dysregulated following nerve injury and the current understanding of their roles in pathophysiological pain-related responses including neuroimmune interactions, neuronal survival and axon regeneration, Schwann cell dedifferentiation and proliferation, intercellular communication, and the generation of ectopic action potentials in primary afferents. We review progress in the field beyond cataloging, with a focus on the relevant target transcripts and mechanisms underlying pain modulation by ncRNAs.

The emerging power and promise of non-coding RNAs in chronic pain

Chronic pain (CP) is an unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage lasting longer than 3 months. CP is the main reason why people seek medical care and exerts an enormous economic burden. Genome-wide expression analysis has revealed that diverse essential genetic elements are altered in CP patients. Although many possible mechanisms of CP have been revealed, we are still unable to meet all the analgesic needs of patients. In recent years, non-coding RNAs (ncRNAs) have been shown to play essential roles in peripheral neuropathy and axon regeneration, which is associated with CP occurrence and development. Multiple key ncRNAs have been identified in animal models of CP, such as microRNA-30c-5p, ciRS-7, and lncRNA MRAK009713. This review highlights different kinds of ncRNAs in the regulation of CP, which provides a more comprehensive understanding of the pathogenesis of the disease. It mainly focuses on the contributions of miRNAs, circRNAs, and lncRNAs to CP, specifically peripheral neuropathic pain (NP), diabetic NP, central NP associated with spinal cord injury, complex regional pain syndrome, inflammatory pain, and cancer-induced pain. In addition, we summarize some potential ncRNAs as novel biomarkers for CP and its complications. With an in-depth understanding of the mechanism of CP, ncRNAs may provide novel insight into CP and could become new therapeutic targets in the future.

Current understanding of MSC-derived exosomes in the management of knee osteoarthritis

Mesenchymal stem cell-derived exosomes (MSC-Exos) have been utilized as medicinal agents or as delivery vehicles in cartilage injuries and cartilage-based diseases. Given the ongoing emergence of evidence on the effector mechanisms and methods of the utility of the MSC-Exos in knee osteoarthritis, a comprehensive review of the current evidence is the need of the hour. Hence, in this article, we review the current understanding of the role of MSC-Exos in the management of knee osteoarthritis in view of their classification, characterization, biogenesis, mechanism of action, pathways involved in their therapeutic action, in-vitro evidence on cartilage regeneration, in-vivo evidence in OA knee models and recent advances in using MSC-Exos to better streamline future research from bench to bedside for OA knee.

Interplay between exosomes and autophagy machinery in pain management: State of the art

Despite recent progress regarding inexpensive medical approaches, many individuals suffer from moderate to severe pain globally. The discovery and advent of exosomes, as biological nano-sized vesicles, has revolutionized current knowledge about underlying mechanisms associated with several pathological conditions. Indeed, these particles are touted as biological bio-shuttles with the potential to carry specific signaling biomolecules to cells in proximity and remote sites, maintaining cell-to-cell communication in a paracrine manner. A piece of evidence points to an intricate relationship between exosome biogenesis and autophagy signaling pathways at different molecular levels. A close collaboration of autophagic response with exosome release can affect the body's hemostasis and physiology of different cell types. This review is a preliminary attempt to highlight the possible interface of autophagy flux and exosome biogenesis on pain management with a special focus on neuropathic pain. It is thought that this review article will help us to understand the interplay of autophagic response and exosome biogenesis in the management of pain under pathological conditions. The application of therapies targeting autophagy pathway and exosome abscission can be an alternative strategy in the regulation of pain.

Expression and Biological Functions of miRNAs in Chronic Pain: A Review on Human Studies

Chronic pain is a major public health problem and an economic burden worldwide. However, its underlying pathological mechanisms remain unclear. MicroRNAs (miRNAs) are a class of small noncoding RNAs that post-transcriptionally regulate gene expression and serve key roles in physiological and pathological processes. This review aims to synthesize the human studies examining miRNA expression in the pathogenesis of chronic primary pain and chronic secondary pain. Additionally, to understand the potential pathophysiological impact of miRNAs in these conditions, an in silico analysis was performed to reveal the target genes and pathways involved in primary and secondary pain and their differential regulation in the different types of chronic pain. The findings, methodological issues and challenges of miRNA research in the pathophysiology of chronic pain are discussed. The available evidence suggests the potential role of miRNA in disease pathogenesis and possibly the pain process, eventually enabling this role to be exploited for pain monitoring and management.

Research Progress in the Application of Exosomes in Immunotherapy

Exosomes are nanoscale extracellular vesicles (EVs), which are present in all body fluids tested. They are secreted by a variety of cells including macrophages, dendritic cells, mast cells, granulocytes, lymphocytes, and tumor cells. Exosomes secreted by different cells have different biological components and functional characteristics and play an important role in many pathophysiological activities. Recent studies have revealed that exosomes can regulate the occurrence and development of inflammatory immune diseases and tumors by transmitting their unique proteins, lipids, and nucleic acids as signaling molecules to other cells. Exosomes serve as a novel class of diagnostic biomarkers and drug delivery systems with promising applications in immunotherapy, particularly because breakthroughs in nanotechnology have led to the development and exploration of engineered exosomes for immunotargeted therapies. Therefore, here we review the progress being made on the application of exosomes in immunotherapy and its multiple regulatory mechanisms and explore the potential application of exosomes in immunotherapy in the future.

miR-338-5p Levels and Cigarette Smoking are Associated With Neuropathic Pain Severity in Individuals With Spinal Cord Injury: Preliminary Findings From a Genome-Wide microRNA Expression Profiling Screen

OBJECTIVE

To identify microRNA biomarkers and clinical factors associated with neuropathic pain after spinal cord injury.

DESIGN

Cross-sectional, secondary analysis of baseline data collected from ongoing clinical studies. Using a genome-wide microRNA screening approach, we studied differential microRNA expression in serum from 43 adults with spinal cord injury enrolled in ongoing clinical studies. Least squares regression was used to identify associations between microRNA expression, clinical factors, and neuropathic pain severity.

SETTING

Community-dwelling individuals with spinal cord injury.

PARTICIPANTS

Participants (N=43) were at least 18 years old with spinal cord injury, with 28 reporting neuropathic pain and 15 reporting no neuropathic pain.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Pain presence, type, and intensity were assessed with the International Spinal Cord Injury Pain Basic Data Set. Serum microRNA normalized deep sequencing counts were quantified from blood samples. Participant demographic factors, injury characteristics, medication use, and health habits were collected via questionnaire.

RESULTS

miR-338-5p expression and history of cigarette smoking were associated with and explained 37% of the variance in neuropathic pain severity (R2=0.37, F2,18=5.31, P=.02) independent of other clinical factors. No association was identified between miR-338-5p levels and nociceptive pain severity.

CONCLUSIONS

Our findings suggest that miR-338-5p and cigarette smoking may both play a role in the development or maintenance of neuropathic pain after spinal cord injury. While additional work is needed to confirm these findings, validated target analysis suggests a neuroprotective role of miR-338-5p in modulating neuroinflammation and neuronal apoptosis and that its downregulation may result in maladaptive neuroplastic mechanisms contributing to neuropathic pain after spinal cord injury.

Extracellular Vesicles: A New Paradigm for Cellular Communication in Perioperative Medicine, Critical Care, and Pain Management

Extracellular vesicles (EVs) play critical roles in many health and disease states, including ischemia, inflammation, and pain, which are major concerns in the perioperative period and in critically ill patients. EVs are functionally active, nanometer-sized, membrane-bound vesicles actively secreted by all cells. Cell signaling is essential to physiological and pathological processes, and EVs have recently emerged as key players in intercellular communication. Recent studies in EV biology have improved our mechanistic knowledge of the pathophysiological processes in perioperative and critical care patients. Studies also show promise in using EVs in novel diagnostic and therapeutic clinical applications. This review considers the current advances and gaps in knowledge of EVs in the areas of ischemia, inflammation, pain, and in organ systems that are most relevant to anesthesiology, perioperative medicine, critical care, and pain management. We expect the reader will better understand the relationship between EVs and perioperative and critical care pathophysiological states and their potential use as novel diagnostic and therapeutic modalities.

Mesenchymal Stem Cell-Derived Extracellular Vesicles for Osteoarthritis Treatment: Extracellular Matrix Protection, Chondrocyte and Osteocyte Physiology, Pain and Inflammation Management

Osteoarthritis (OA) is a common degenerative disease that can lead to persistent pain and motion restriction. In the last decade, stem cells, particularly mesenchymal stem cells (MSCs), have been explored as a potential alternative OA therapy due to their regenerative capacity. Furthermore, it has been shown that trophic factors enveloped in extracellular vesicles (EVs), including exosomes, are a crucial aspect of MSC-based treatment for OA. Evidently, EVs derived from different MSC sources might rescue the OA phenotype by targeting many biological processes associated with cartilage extracellular matrix (ECM) degradation and exerting protective effects on different joint cell types. Despite this advancement, different studies employing EV treatment for OA have revealed reverse outcomes depending on the EV cargo, cell source, and pathological condition. Hence, in this review, we aim to summarize and discuss the possible effects of MSC-derived EVs based on recent findings at different stages of OA development, including effects on cartilage ECM, chondrocyte biology, osteocytes and bone homeostasis, inflammation, and pain management. Additionally, we discuss further strategies and technical advances for manipulating EVs to specifically target OA to bring the therapy closer to clinical use.

A Review of the Clinical and Therapeutic Implications of Neuropathic Pain

Understanding neuropathic pain presents several challenges, given the various mechanisms underlying its pathophysiological classification and the lack of suitable tools to assess its diagnosis. Furthermore, the response of this pathology to available drugs is still often unpredictable, leaving the treatment of neuropathic pain still questionable. In addition, the rise of personalized treatments further extends the ramified classification of neuropathic pain. While a few authors have focused on neuropathic pain clustering, by analyzing, for example, the presence of specific TRP channels, others have evaluated the presence of alterations in microRNAs to find tailored therapies. Thus, this review aims to synthesize the available evidence on the topic from a clinical perspective and provide a list of current demonstrations on the treatment of this disease.

Circulating microRNAs from the mouse tibia fracture model reflect the signature from patients with complex regional pain syndrome

INTRODUCTION

Complex regional pain syndrome (CRPS) often results from an initial trauma that later produces a disproportionate amount of pain. The mechanisms underlying CRPS have been studied using a tibia fracture model (TFM) in rodents because this model closely mimics symptoms and has several molecular correlates observed in patients with CRPS.

OBJECTIVE

Here, we determined whether the TFM has alterations in circulating microRNAs (miRNAs) and cytokines transported by small extracellular vesicles (sEVs) that faithfully model previously reported miRNA alterations from patients with CRPS.

METHODS

We isolated and characterized serum-derived sEVs from mice 3 weeks after fracture when symptoms such as pain hypersensitivity develop. Whole-transcriptome profiling was used to determine sEV miRNAs, and Bio-Plex Pro Mouse Cytokine 23-plex assay was used to measure cytokines. Differentially expressed miRNAs from TFM were compared with previously reported circulating miRNA alterations from patients with CRPS.

RESULTS

Although sEV cytokine levels were unchanged, there were significant changes in sEV miRNA profiles. Differentially expressed miRNAs from TFM sEVs significantly overlapped with those previously reported in patients with CRPS. Of the 57 sEV miRNAs dysregulated in the TFM, 30 were previously reported in patients with CRPS compared with healthy control donors both in sEVs and 23 in whole blood.

CONCLUSIONS

These findings enhance the validity of TFM as a model for CRPS and suggest that specific miRNA dysregulation may be a shared feature of CRPS and the TFM. These dysregulated miRNAs could help identify mechanistic targets or serve as biomarker candidates for both diagnosis and treatment responses in clinical trials.

Nociception and Pain: New Roles for Exosomes

The interchange of information from one cell to another relies on the release of hundreds of different molecules including small peptides, amino acids, nucleotides, RNA, steroids, retinoids, or fatty acid metabolites. Many of them are released to the extracellular matrix as free molecules and others can be part of the cargo of cellular vesicles. Small extracellular vesicles (30-150 nm), also known as exosomes, are a known mechanism of cell-to-cell communication in the nervous system. Exosomes participate in the pathogenesis of several neurological conditions including Alzheimer's and Parkinson's disease. However, exciting emerging evidence demonstrates that exosomes also regulate mechanisms of the sensory process including nociception. The goal of this review is to summarize the literature on exosome biogenesis, methods of small vesicle isolation and purification, and their role in nociception. We also provide insights on the potential applications of exosomes as pain biomarkers or as novel therapeutics.

Of mice, microglia, and (wo)men: a case series and mechanistic investigation of hydroxychloroquine for complex regional pain syndrome

Introduction

Complex regional pain syndrome (CRPS) is a condition that occurs after minor trauma characterized by sensory, trophic, and motor changes. Although preclinical studies have demonstrated that CRPS may be driven in part by autoinflammation, clinical use of immune-modulating drugs in CRPS is limited. Hydroxychloroquine (HCQ) is a disease-modifying antirheumatic drug used to treat malaria and autoimmune disorders that may provide benefit in CRPS.

Objectives

To describe the use of HCQ in patients with refractory CRPS and investigate possible mechanisms of benefit in a mouse model of CRPS.

Methods

We initiated HCQ therapy in 7 female patients with refractory CRPS undergoing treatment at the Stanford Pain Management Center. We subsequently undertook studies in the mouse tibial fracture-casting model of CRPS to identify mechanisms underlying symptom reduction. We evaluated behavior using mechanical allodynia and spinal cord autoinflammation by immunohistochemistry and enzyme-linked immunosorbent assay.

Results

We treated 7 female patients with chronic, refractory CRPS with HCQ 200 mg twice daily for 2 months, followed by 200 mg daily thereafter. Two patients stopped HCQ secondary to lack of response or side effects. Overall, HCQ significantly improved average numerical rating scale pain from 6.8 ± 1.1 before HCQ to 3.8 ± 1.9 after HCQ treatment. In the tibial fracture-casting mouse model of CRPS, we observed reductions in allodynia, paw edema, and warmth following daily HCQ treatment starting at 3 weeks after injury. Spinal cord dorsal horn microglial activation and cytokine levels were also reduced by HCQ treatment.

Conclusion

Together, these preclinical and clinical results suggest that HCQ may benefit patients with CRPS at least in part by modulating autoinflammation and support further investigation into the use of HCQ for CRPS.

MicroRNA-338-5p alleviates cerebral ischemia/reperfusion injury by targeting connective tissue growth factor through the adenosine 5'-monophosphate-activated protein kinase/mammalian target of rapamycin signaling pathway

Cerebral ischemia/reperfusion (CIR) injury could lead to the function of brain cell disorder and cerebral infarction. MicroRNAs (miRNAs) have been reported to participate in the progression and protection of CIR injury. Thus, our study aimed to investigate the functional effects of microRNA-338-5p (miR-338-5p) on proliferation, apoptosis, and inflammatory response of CIR injury. According to the results, miR-338-5p was downregulated in the brain of the mice caused by CIR injury, and overexpression of miR-338-5p reduced the neurological deficit and infarct volume of the brain in the mice caused by CIR injury. Meanwhile, miR-338-5p overexpression promoted the proliferation, while suppressed the apoptosis and the inflammatory response of Neuro-2a cells exposed to hypoxia/reoxygenation (H/R). Interestingly, miR-338-5p directly targeted connective tissue growth factor (CTGF) and overexpression of CTGF reversed the functional effects of miR-338-5p on proliferation, apoptosis, and inflammatory response in Neuro-2a cells caused by H/R. More importantly, miR-338-5p affected the adenosine 5¢-monophosphate (AMP)-activated protein kinase (AMPK)/mammalian target of rapamycin (mTOR) signaling pathway by regulating CTGF expression in Neuro-2a cells exposed to H/R. Taken together, we concluded that MiR-338-5p promoted the proliferation, while suppressed the apoptosis and the inflammatory response of cells exposed to H/R by targeting CTGF through the AMPK/mTOR signaling pathway.

Exosomes in Sepsis

Sepsis is a severe state of infection with high mortality. Pathogen-associated molecular patterns and damage-associated molecular patterns (DAMPs) initiate dysregulated systemic inflammation upon binding to pattern recognition receptors. Exosomes are endosome-derived vesicles, which carry proteins, lipids and nucleic acids, and facilitate intercellular communications. Studies have shown altered contents and function of exosomes during sepsis. In sepsis, exosomes carry increased levels of cytokines and DAMPs to induce inflammation. Exosomal DAMPs include, but are not limited to, high mobility group box 1, heat shock proteins, histones, adenosine triphosphate, and extracellular RNA. Exosomes released during sepsis have impact on multiple organs, including the lungs, kidneys, liver, cardiovascular system, and central nervous system. Here, we review the mechanisms of inflammation caused by exosomes, and their contribution to multiple organ dysfunction in sepsis.

Optimizing Perioperative Use of Opioids: A Multimodal Approach

Purpose of Review

The main purpose of this article is to review recent literature regarding multimodal analgesia medications, citing their recommended doses, efficacy, and side effects. The second part of this report will provide a description of drugs in different stages of development which have novel mechanisms with less side effects such as tolerance and addiction.

Recent Findings

Multimodal analgesia is a technique that facilitates perioperative pain management by employing two or more systemic analgesics along with regional anesthesia, when possible. Even though opioids and non-opioid analgesics remain the most common medication used for acute pain management after surgery, they have many undesirable side effects including the potential for misuse. Newer analgesics including peripheral acting opioids, nitric oxide inhibitors, calcitonin gene-related peptide receptor antagonists, interleukin-6 receptor antagonists and gene therapy are under intensive investigation.

Summary

A patient's first exposure to opioids is often in the perioperative setting, a vulnerable time when multimodal therapy can play a large role in decreasing opioid exposure. Additionally, the current shift towards faster recovery times, fewer post-operative complications and improved cost-effectiveness during the perioperative period has made multimodal analgesia a central pillar of Enhanced Recovery After Surgery (ERAS) protocols.

Extracellular Matrix-Mediated Breast Cancer Cells Morphological Alterations, Invasiveness, and Microvesicles/Exosomes Release

Breast cancer is a leading disease in women. Several studies are focused to evaluate the critical role of extracellular matrix (ECM) in various biochemical and molecular aspects but also in terms of its effect on cancer cell morphology and therefore on cancer cell invasion and metastatic potential. ECM fibrillar components, such as collagen and fibronectin, affect cell behavior and properties of mammary cancer cells. The aim of this study was to investigate using the scanning electron microscopy (SEM) how the highly invasive MDA-MB-231 breast cancer cells, interplaying with ECM substrates during cell migration/invasion, modify their morphological characteristics and cytoplasmic processes in relation to their invasive potential. In particular we reproduced and analyzed how natural structural barriers to cancer cell invasion, such as the basement membrane (Matrigel) and fibrillar components of dermis (fibronectin as well as the different concentrations/array of type I collagen), could induce morphological changes in 3D cultures. Interestingly, we demonstrate that, even with different effects, all collagen concentrations/arrays lead to morphological alterations of breast cancer cells. Intriguingly, the elongated mesenchymal shaped cells were more prominent in 3D cultures with a dense and thick substrate (thick Matrigel, high concentrated collagen network, and densely packed collagen fibers), even though cells with different shape produced and released microvesicles and exosomes as well. It is therefore evident that the peri-tumoral collagen network may act not only as a barrier but also as a dynamic scaffold which stimulates the morphological changes of cancer cells, and modulates tumor development and metastatic potential in breast cancer.

Non-coding RNAs in neuropathic pain

Neuro-immune alterations in the peripheral and central nervous system play a role in the pathophysiology of chronic pain in general, and members of the non-coding RNA (ncRNA) family, specifically the short, 22 nucleotide microRNAs (miRNAs) and the long non-coding RNAs (lncRNAs) act as master switches orchestrating both immune as well as neuronal processes. Several chronic disorders reveal unique ncRNA expression signatures, which recently generated big hopes for new perspectives for the development of diagnostic applications. lncRNAs may offer perspectives as candidates indicative of neuropathic pain in liquid biopsies. Numerous studies have provided novel mechanistic insight into the role of miRNAs in the molecular sequelae involved in the pathogenesis of neuropathic pain along the entire pain pathway. Specific processes within neurons, immune cells, and glia as the cellular components of the neuropathic pain triad and the communication paths between them are controlled by specific miRNAs. Therefore, nucleotide sequences mimicking or antagonizing miRNA actions can provide novel therapeutic strategies for pain treatment, provided their human homologues serve the same or similar functions. Increasing evidence also sheds light on the function of lncRNAs, which converge so far mainly on purinergic signalling pathways both in neurons and glia, and possibly even other ncRNA species that have not been explored so far.

Exosomes as a new pain biomarker opportunity

Exosomes are extracellular microvesicles implicated in intercellular communication with ability to transfer cargo molecules, including protein, lipids, and nucleic acids, at both close and distant target sites. It has been shown that exosomes are implicated in physiological and pathological processes. In recent years, the interest on exosomes' role in many pain states has increased. Their involvements in pain processes have been demonstrated by studies on different chronic pain diseases, both inflammatory and neuropathic, such as osteoarthritis, rheumatoid arthritis, inflammatory bowel diseases, neurodegenerative pathologies, complex regional pain syndrome, and peripheral nerve injury. Animal and clinical studies investigated exosomes-based treatments, showing their ability to improve painful symptoms with fewer side effects, with potential immunoprotective and anti-inflammatory effect. Specific molecular patterns characterize exosomes' cargo according to the cellular origin, epigenetic modifications, environmental state, and stressor factors. Therefore, the identification of specific cargo's profile associated to pain states may lead to recognize specific pathological states and to consider the use of exosomes as biomarkers of diseases. Furthermore, exosomes' ability to transfer information and their presence in many accessible biological fluids suggest a potential use as novel non-invasive therapeutic tools in pain field.

The role of collagen in cancer: from bench to bedside

Collagen is the major component of the tumor microenvironment and participates in cancer fibrosis. Collagen biosynthesis can be regulated by cancer cells through mutated genes, transcription factors, signaling pathways and receptors; furthermore, collagen can influence tumor cell behavior through integrins, discoidin domain receptors, tyrosine kinase receptors, and some signaling pathways. Exosomes and microRNAs are closely associated with collagen in cancer. Hypoxia, which is common in collagen-rich conditions, intensifies cancer progression, and other substances in the extracellular matrix, such as fibronectin, hyaluronic acid, laminin, and matrix metalloproteinases, interact with collagen to influence cancer cell activity. Macrophages, lymphocytes, and fibroblasts play a role with collagen in cancer immunity and progression. Microscopic changes in collagen content within cancer cells and matrix cells and in other molecules ultimately contribute to the mutual feedback loop that influences prognosis, recurrence, and resistance in cancer. Nanoparticles, nanoplatforms, and nanoenzymes exhibit the expected gratifying properties. The pathophysiological functions of collagen in diverse cancers illustrate the dual roles of collagen and provide promising therapeutic options that can be readily translated from bench to bedside. The emerging understanding of the structural properties and functions of collagen in cancer will guide the development of new strategies for anticancer therapy.