The exosome-like vesicles from osteoarthritic chondrocyte enhanced mature IL-1β production of macrophages and aggravated synovitis in osteoarthritis

Synovial microenvironment in temporomandibular joint osteoarthritis: crosstalk with chondrocytes and potential therapeutic targets

Temporomandibular joint osteoarthritis (TMJOA) is considered to be a low-grade inflammatory disease involving multiple joint tissues. The crosstalk between synovium and cartilage plays an important role in TMJOA. Synovial cells are a group of heterogeneous cells and synovial microenvironment is mainly composed of synovial fibroblasts (SF) and synovial macrophages. In TMJOA, SF and synovial macrophages release a large number of inflammatory cytokines and extracellular vesicles and promote cartilage destruction. Cartilage wear particles stimulate SF proliferation and macrophages activation and exacerbate synovitis. In TMJOA, chondrocytes and synovial cells exhibit increased glycolytic activity and lactate secretion, leading to impaired chondrocyte matrix synthesis. Additionally, the synovium contains mesenchymal stem cells, which are the seed cells for cartilage repair in TMJOA. Co-culture of chondrocytes and synovial mesenchymal stem cells enhances the chondrogenic differentiation of stem cells. This review discusses the pathological changes of synovium in TMJOA, the means of crosstalk between synovium and cartilage, and their influence on each other. Based on the crosstalk between synovium and cartilage in TMJOA, we illustrate the treatment strategies for improving synovial microenvironment, including reducing cell adhesion, utilizing extracellular vesicles to deliver biomolecules, regulating cellular metabolism and targeting inflammatory cytokines.

Yin-Yang: two sides of extracellular vesicles in inflammatory diseases

The concept of Yin-Yang, originating in ancient Chinese philosophy, symbolizes two opposing but complementary forces or principles found in all aspects of life. This concept can be quite fitting in the context of extracellular vehicles (EVs) and inflammatory diseases. Over the past decades, numerous studies have revealed that EVs can exhibit dual sides, acting as both pro- and anti-inflammatory agents, akin to the concept of Yin-Yang theory (i.e., two sides of a coin). This has enabled EVs to serve as potential indicators of pathogenesis or be manipulated for therapeutic purposes by influencing immune and inflammatory pathways. This review delves into the recent advances in understanding the Yin-Yang sides of EVs and their regulation in specific inflammatory diseases. We shed light on the current prospects of engineering EVs for treating inflammatory conditions. The Yin-Yang principle of EVs bestows upon them great potential as, therapeutic, and preventive agents for inflammatory diseases.

New insights into the mechanisms and therapeutic strategies of chondrocyte autophagy in osteoarthritis

Osteoarthritis (OA) is a chronic joint disease with an unclear cause characterized by secondary osteophytes and degenerative changes in the articular cartilage. More than 250 million people are expected to be affected by it by 2050, putting a tremendous socioeconomic strain on the entire world. OA cannot currently be treated with any effective medications that change the illness. Over time, chondrocytes undergo gradual metabolic, structural, and functional changes as a result of aging or abuse. The degenerative progression of osteoarthritis is significantly influenced by the imbalance of chondrocyte homeostasis. By continuously recycling and rebuilding macromolecules or organelles, autophagy functions as a crucial regulatory system to maintain homeostasis during an individual's growth and development. This review uses chondrocytes as its starting point and establishes a strong connection between autophagy and osteoarthritis in order to thoroughly examine the mechanisms behind chondrocyte autophagy in osteoarthritis. Biomarkers of chondrocyte autophagy will be identified, and prospective targeted medications and novel treatment approaches for slowing or preventing the course of OA will be developed based on chondrocyte senescence, autophagy, and apoptosis in OA. KEY MESSAGES: Currently, OA has not been treated with any drugs that can effectively cure it. We hope that by exploring specific targets in the course of osteoarthritis, we can promote the progress of treatment strategies. The degenerative progression of osteoarthritis is significantly influenced by the imbalance of chondrocyte balance. Through the continuous recovery and reconstruction of macromolecules or organelles, autophagy is an important regulatory system for maintaining homeostasis during individual growth and development. In this paper, the close relationship between autophagy and osteoarthritis was established with chondrocytes as the starting point, in order to further explore the mechanism of chondrocyte autophagy in osteoarthritis. The development process of osteoarthritis was studied from the perspective of chondrocytes, and the change of autophagy level had a significant impact on osteoarthritis. Chondrocyte autophagy is mainly determined by intracellular mitochondrial autophagy, so we are committed to finding relevant molecules. Through PI3K/AKT- and MAPK-related pathways, the biomarkers of chondrocyte autophagy were identified, and chondrocyte senescence, autophagy, and apoptosis based on osteoarthritis provided a constructive idea for the development of prospective targeted drugs and new therapies to slow down or prevent the progression of osteoarthritis.

Depression heightened the association of the systemic immune-inflammation index with all-cause mortality among osteoarthritis patient

BACKGROUND

Systemic immune-inflammatory index (SII) has been recognized as a novel inflammatory indicator in numerous diseases. It remains unknown how SII affects all-cause mortality among patients with osteoarthritis (OA). In this prospective cohort study, we intended to examine the relationship of SII with all-cause mortality among OA populations and assess the interaction between depression and SII.

METHODS

Data was collected from National Health and Nutrition Examination Survey (NHANES) in 2005-2018. The National Death Index (NDI) provided vital status records. Multivariable Cox regression analyses with cubic spines were applied to estimate the association between SII and all-cause and CVD mortality. Stratified analysis and interaction tests assessed the interaction of SII and depression on all-cause mortality.

RESULTS

In total 3174 OA adults were included. The lowest quartile Q1 (HR:1.44, 95%CI:1.02-2.04) and highest quartile Q4 (HR:1.44, 95%CI:1.02-2.04) of SII presented a higher risk of death compared with those in second quartile Q2 (Ref.) and third quartile Q3 (HR:1.23, 95%CI:0.89-1.68. Restricted cubic splines analysis revealed a U-shaped association of SII with all-cause mortality, the inflection points were 412.93 × 109/L. The interaction test observed a more significant relationship of SII with all-cause mortality in depression patients than in non-depression patients, indicating that depression can modify this association.

LIMITATIONS

First, the observational study design failed to make causal inferences. Second, the baseline SII cannot reflect the long-term level of inflammation. Finally, there may be potential bias.

CONCLUSION

SII was U-shaped associated with all-cause mortality in OA patients, and this association was significantly heightened by depression.

Skeleton-derived extracellular vesicles in bone and whole-body aging: From mechanisms to potential applications

The skeleton serves as a supportive and protective organ for the body. As individuals age, their bone tissue undergoes structural, cellular, and molecular changes, including the accumulation of senescent cells. Extracellular vesicles (EVs) play a crucial role in aging through the cellular secretome and have been found to induce or accelerate age-related dysfunction in bones and to contribute further via the circulatory system to the aging of phenotypes of other bodily systems. However, the extent of these effects and their underlying mechanisms remain unclear. Therefore, this paper attempts to give an overview of the current understanding of age-related alteration in EVs derived from bones. The role of EVs in mediating communications among bone-related cells and other body parts is discussed, and the significance of bones in the whole-body aging process is highlighted. Ultimately, it is hoped that gaining a clearer understanding of the relationship between EVs and aging mechanisms may serve as a basis for new treatment strategies for age-related degenerative diseases in the skeleton and other systems.

Roles of extracellular vesicles on macrophages in inflammatory bone diseases

Inflammatory bone disease is a general term for a series of diseases caused by chronic inflammation, which leads to the destruction of bone homeostasis, that is, the osteolytic activity of osteoclasts increases, and the osteogenic activity of osteoblasts decreases, leading to osteolysis. Macrophages are innate immune cell with plasticity, and their polarization is related to inflammatory bone diseases. The dynamic balance of macrophages between the M1 phenotype and the M2 phenotype affects the occurrence and development of diseases. In recent years, an increasing number of studies have shown that extracellular vesicles existing in the extracellular environment can act on macrophages, affecting the progress of inflammatory diseases. This process is realized by influencing the physiological activity or functional activity of macrophages, inducing macrophages to secrete cytokines, and playing an anti-inflammatory or pro-inflammatory role. In addition, by modifying and editing extracellular vesicles, the potential of targeting macrophages can be used to provide new ideas for developing new drug carriers for inflammatory bone diseases.

Role of crosstalk between synovial cells and chondrocytes in osteoarthritis (Review)

Osteoarthritis (OA) is a low-grade, nonspecific inflammatory disease that affects the entire joint. This condition is characterized by synovitis, cartilage erosion, subchondral bone defects, and subpatellar fat pad damage. There is mounting evidence demonstrating the significance of crosstalk between synovitis and cartilage destruction in the development of OA. To comprehensively explore the phenotypic alterations of synovitis and cartilage destruction, it is important to elucidate the crosstalk mechanisms between chondrocytes and synovial cells. Furthermore, the updated iteration of single-cell sequencing technology reveals the interaction between chondrocyte and synovial cells. In the present review, the histological and pathological alterations between cartilage and synovium during OA progression are described, and the mode of interaction and molecular mechanisms between synovial cells and chondrocytes in OA, both of which affect the OA process mainly by altering the inflammatory environment and cellular state, are elucidated. Finally, the current OA therapeutic approaches are summarized and emerging therapeutic targets are reviewed in an attempt to provide potential insights into OA treatment.

β1-Integrin-Mediated Uptake of Chondrocyte Extracellular Vesicles Regulates Chondrocyte Homeostasis

Osteoarthritis (OA) is the most prevalent age-related degenerative disorder, which severely reduces the quality of life of those affected. Whilst management strategies exist, no cures are currently available. Virtually all joint resident cells generate extracellular vesicles (EVs), and alterations in chondrocyte EVs during OA have previously been reported. Herein, we investigated factors influencing chondrocyte EV release and the functional role that these EVs exhibit. Both 2D and 3D models of culturing C28I/2 chondrocytes were used for generating chondrocyte EVs. We assessed the effect of these EVs on chondrogenic gene expression as well as their uptake by chondrocytes. Collectively, the data demonstrated that chondrocyte EVs are sequestered within the cartilage ECM and that a bi-directional relationship exists between chondrocyte EV release and changes in chondrogenic differentiation. Finally, we demonstrated that the uptake of chondrocyte EVs is at least partially dependent on β1-integrin. These results indicate that chondrocyte EVs have an autocrine homeostatic role that maintains chondrocyte phenotype. How this role is perturbed under OA conditions remains the subject of future work.

Interplay between lipid dysregulation and ferroptosis in chondrocytes and the targeted therapy effect of metformin on osteoarthritis

INTRODUCTION

Osteoarthritis (OA) is a devastating whole-joint disease affecting a large population worldwide; the role of lipid dysregulation in OA and mechanisms underlying targeted therapy effect of lipid-lowering metformin on OA remains poorly defined.

OBJECTIVES

To investigate the effects of lipid dysregulation on OA progression and to explore lipid dysregulation-targeting OA treatment of metformin.

METHODS

RNA-Seq data, biochemical, and histochemical assays in human and murine OA cartilage as well as primary chondrocytes were utilized to determine lipid dysregulation. Effects of metformin, a potent lipid-lowering medication, on ACSL4 expression and chondrocyte metabolism were determined. Further molecular experiments, including RT-qPCR, western blotting, flow cytometry, and immunofluorescence staining, were performed to investigate underlying mechanisms. Mice with intra-articular injection of metformin were utilized to determine the effects on ACLT-induced OA progression.

RESULTS

ACSL4 and 4-HNE expressions were elevated in human and ACLT-induced mouse OA cartilage and IL-1β-treated chondrocytes (P < 0.05). Ferrostatin-1 largely rescued IL-1β-induced MDA, lipid peroxidation, and ferroptotic mitochondrial morphology (P < 0.05). Metformin decreased the levels of OA-related genes (P < 0.05) and increased the levels of p-AMPK and p-ACC in IL-1β-treated chondrocytes. Intra-articular injection of metformin alleviated ACLT-induced OA lesions in mice, and reverted the percentage of chondrocytes positive for MMP13, Col2a1, ACSL4 and 4-HNE in ACLT mice (P < 0.05). Ferroptotic chondrocytes promoted the recruitment and chemotaxis of RAW264.7 cells via CCL2, which was blocked by metformin in vitro (P < 0.05).

CONCLUSION

We establish a critical role of polyunsaturated fatty acids metabolic process in OA cartilage degradation and define metformin as a potential OA treatment. Metformin reshapes lipid availability and ameliorates chondrocyte ferroptosis sensitivity via the AMPK/ACC pathway. In the future, gene-edited animals and extensive omics technologies will be utilized to reveal detailed lipids' involvement in cartilage lesions.

Inflammatory Fibroblast-Like Synoviocyte-Derived Exosomes Aggravate Osteoarthritis via Enhancing Macrophage Glycolysis

The severity of osteoarthritis (OA) and cartilage degeneration is highly associated with synovial inflammation. Although recent investigations have revealed a dysregulated crosstalk between fibroblast-like synoviocytes (FLSs) and macrophages in the pathogenesis of synovitis, limited knowledge is available regarding the involvement of exosomes. Here, increased exosome secretion is observed in FLSs from OA patients. Notably, internalization of inflammatory FLS-derived exosomes (inf-exo) can enhance the M1 polarization of macrophages, which further induces an OA-like phenotype in co-cultured chondrocytes. Intra-articular injection of inf-exo induces synovitis and exacerbates OA progression in murine models. In addition, it is demonstrated that inf-exo stimulation triggers the activation of glycolysis. Inhibition of glycolysis using 2-DG successfully attenuates excessive M1 polarization triggered by inf-exo. Mechanistically, HIF1A is identified as the determinant transcription factor, inhibition of which, both pharmacologically or genetically, relieves macrophage inflammation triggered by inf-exo-induced hyperglycolysis. Furthermore, in vivo administration of an HIF1A inhibitor alleviates experimental OA. The results provide novel insights into the involvement of FLS-derived exosomes in OA pathogenesis, suggesting that inf-exo-induced macrophage dysfunction represents an attractive target for OA therapy.

Sympathetic innervation induces exosomal miR-125 transfer from osteoarthritic chondrocytes, disrupting subchondral bone homeostasis and aggravating cartilage damage in aging mice

INTRODUCTION

Osteoarthritis (OA) is a progressive disease that poses a significant threat to human health, particularly in aging individuals: Although sympathetic activation has been implicated in bone metabolism, its role in the development of OA related to aging remains poorly understood. Therefore, this study aimed to investigate how sympathetic regulation impacts aging-related OA through experiments conducted both in vivo and in vitro.

METHODS

To analyze the effect of sympathetic regulation on aging-related OA, we conducted experiments using various mouse models. These models included a natural aging model, a medial meniscus instability model, and a load-induced model, which were used to examine the involvement of sympathetic nerves. In order to evaluate the expression levels of β1-adrenergic receptor (Adrβ1) and sirtuin-6 (Sirt6) in chondrocytes of naturally aging OA mouse models, we performed assessments. Additionally, we investigated the influence of β1-adrenergic receptor knockout or treatment with a β1-adrenergic receptor blocker on the progression of OA in aging mice and detected exosome release and detected downstream signaling expression by inhibiting exosome release. Furthermore, we explored the impact of sympathetic depletion through tyrosine hydroxylase (TH) on OA progression in aging mice. Moreover, we studied the effects of norepinephrine(NE)-induced activation of the β1-adrenergic receptor signaling pathway on the release of exosomes and miR-125 from chondrocytes, subsequently affecting osteoblast differentiation in subchondral bone.

RESULTS

Our findings demonstrated a significant increase in sympathetic activity, such as NE levels, in various mouse models of OA including natural aging, medial meniscus instability, and load-induced models. Notably, we observed alterations in the expression levels of β1-adrenergic receptor and Sirt6 in chondrocytes in OA mouse models associated with natural aging, leading to an improvement in the progression of OA. Critically, we found that the knockout of β1-adrenergic receptor or treatment with a β1-adrenergic receptor blocker attenuated OA progression in aging mice and the degraded cartilage explants produced more exosome than the nondegraded ones, Moreover, sympathetic depletion through TH was shown to ameliorate OA progression in aging mice. Additionally, we discovered that NE-induced activation of the β1-adrenergic receptor signaling pathway facilitated the release of exosomes and miR-125 from chondrocytes, promoting osteoblast differentiation in subchondral bone.

CONCLUSION

In conclusion, our study highlights the role of sympathetic innervation in facilitating the transfer of exosomal miR-125 from osteoarthritic chondrocytes, ultimately disrupting subchondral bone homeostasis and exacerbating cartilage damage in aging mice. These findings provide valuable insights into the potential contribution of sympathetic regulation to the pathogenesis of aging-related OA.

The dysregulated autophagy in osteoarthritis: Revisiting molecular profile

The risk factors of osteoarthritis (OA) are different and obesity, lifestyle, inflammation, cell death mechanisms and diabetes mellitus are among them. The changes in the biological mechanisms are considered as main regulators of OA pathogenesis. The dysregulation of autophagy is observed in different human diseases. During the pathogenesis of OA, the autophagy levels (induction or inhibition) change. The supportive and pro-survival function of autophagy can retard the progression of OA. The protective autophagy prevents the cartilage degeneration. Moreover, autophagy demonstrates interactions with cell death mechanisms and through inhibition of apoptosis and necroptosis, it improves OA. The non-coding RNA molecules can regulate autophagy and through direct and indirect control of autophagy, they dually delay/increase OA pathogenesis. The mitochondrial integrity can be regulated by autophagy to alleviate OA. Furthermore, therapeutic compounds, especially phytochemicals, stimulate protective autophagy in chondrocytes to prevent cell death. The protective autophagy has ability of reducing inflammation and oxidative damage, as two key players in the pathogenesis of OA.

Exosomes derived from MSC as drug system in osteoarthritis therapy

Osteoarthritis (OA) is the most common degenerative disease of the joint with irreversible cartilage damage as the main pathological feature. With the development of regenerative medicine, mesenchymal stem cells (MSCs) have been found to have strong therapeutic potential. However, intraarticular MSCs injection therapy is limited by economic costs and ethics. Exosomes derived from MSC (MSC-Exos), as the important intercellular communication mode of MSCs, contain nucleic acid, proteins, lipids, microRNAs, and other biologically active substances. With excellent editability and specificity, MSC-Exos function as a targeted delivery system for OA treatment, modulating immunity, inhibiting apoptosis, and promoting regeneration. This article reviews the mechanism of action of MSC-Exos in the treatment of osteoarthritis, the current research status of the preparation of MSC-Exos and its application of drug delivery in OA therapy.

Micro Trojan horses: Engineering extracellular vesicles crossing biological barriers for drug delivery

The biological barriers of the body, such as the blood-brain, placental, intestinal, skin, and air-blood, protect against invading viruses and bacteria while providing necessary physical support. However, these barriers also hinder the delivery of drugs to target tissues, reducing their therapeutic efficacy. Extracellular vesicles (EVs), nanostructures with a diameter ranging from 30 nm to 10 μm secreted by cells, offer a potential solution to this challenge. These natural vesicles can effectively pass through various biological barriers, facilitating intercellular communication. As a result, artificially engineered EVs that mimic or are superior to the natural ones have emerged as a promising drug delivery vehicle, capable of delivering drugs to almost any body part to treat various diseases. This review first provides an overview of the formation and cross-species uptake of natural EVs from different organisms, including animals, plants, and bacteria. Later, it explores the current clinical applications, perspectives, and challenges associated with using engineered EVs as a drug delivery platform. Finally, it aims to inspire further research to help bioengineered EVs effectively cross biological barriers to treat diseases.

Plant-Derived Exosome-Like Nanoparticles: Emerging Nanosystems for Enhanced Tissue Engineering

Tissue engineering holds great potential for tissue repair and rejuvenation. Plant-derived exosome-like nanoparticles (ELNs) have recently emerged as a promising avenue in tissue engineering. However, there is an urgent need to understand how plant ELNs can be therapeutically applied in clinical disease management, especially for tissue regeneration. In this review, we comprehensively examine the properties, characteristics, and isolation techniques of plant ELNs. We also discuss their impact on the immune system, compatibility with the human body, and their role in tissue regeneration. To ensure the suitability of plant ELNs for tissue engineering, we explore various engineering and modification strategies. Additionally, we provide insights into the progress of commercialization and industrial perspectives on plant ELNs. This review aims to highlight the potential of plant ELNs in regenerative medicine by exploring the current research landscape and key findings.

Understanding exosomes: Part 2-Emerging leaders in regenerative medicine

Exosomes are the smallest subset of extracellular signaling vesicles secreted by most cells with the ability to communicate with other tissues and cell types over long distances. Their use in regenerative medicine has gained tremendous momentum recently due to their ability to be utilized as therapeutic options for a wide array of diseases/conditions. Over 5000 publications are currently being published yearly on this topic, and this number is only expected to dramatically increase as novel therapeutic strategies continue to be developed. Today exosomes have been applied in numerous contexts including neurodegenerative disorders (Alzheimer's disease, central nervous system, depression, multiple sclerosis, Parkinson's disease, post-traumatic stress disorders, traumatic brain injury, peripheral nerve injury), damaged organs (heart, kidney, liver, stroke, myocardial infarctions, myocardial infarctions, ovaries), degenerative processes (atherosclerosis, diabetes, hematology disorders, musculoskeletal degeneration, osteoradionecrosis, respiratory disease), infectious diseases (COVID-19, hepatitis), regenerative procedures (antiaging, bone regeneration, cartilage/joint regeneration, osteoarthritis, cutaneous wounds, dental regeneration, dermatology/skin regeneration, erectile dysfunction, hair regrowth, intervertebral disc repair, spinal cord injury, vascular regeneration), and cancer therapy (breast, colorectal, gastric cancer and osteosarcomas), immune function (allergy, autoimmune disorders, immune regulation, inflammatory diseases, lupus, rheumatoid arthritis). This scoping review is a first of its kind aimed at summarizing the extensive regenerative potential of exosomes over a broad range of diseases and disorders.

A Novel Cargo Delivery System-AnCar-ExoLaIMTS Ameliorates Arthritis via Specifically Targeting Pro-Inflammatory Macrophages

Macrophages are heterogenic phagocytic cells that play distinct roles in physiological and pathological processes. Targeting different types of macrophages has shown potent therapeutic effects in many diseases. Although many approaches are developed to target anti-inflammatory macrophages, there are few researches on targeting pro-inflammatory macrophages, which is partially attributed to their non-s pecificity phagocytosis of extracellular substances. In this study, a novel recombinant protein is constructed that can be anchored on an exosome membrane with the purpose of targeting pro-inflammatory macrophages via antigen recognition, which is named AnCar-ExoLaIMTS . The data indicate that the phagocytosis efficiencies of pro-inflammatory macrophages for different AnCar-ExoLaIMTS show obvious differences. The AnCar-ExoLaIMTS3 has the best targeting ability for pro-inflammatory macrophages in vitro and in vivo. Mechanically, AnCar-ExoLaIMTS3 can specifically recognize the leucine-rich repeat domain of the TLR4 receptor, and then enter into pro-inflammatory macrophages via the TLR4-mediated receptor endocytosis pathway. Moreover, AnCar-ExoLaIMTS3 can efficiently deliver therapeutic cargo to pro-inflammatory macrophages and inhibit the synovial inflammatory response via downregulation of HIF-1α level, thus ameliorating the severity of arthritis in vivo. Collectively, the work established a novel gene/drug delivery system that can specifically target pro-inflammatory macrophages, which may be beneficial for the treatments of arthritis and other inflammatory diseases.

Epigenetic Regulation of Autophagy in Bone Metabolism

The skeletal system is crucial for supporting bodily functions, protecting vital organs, facilitating hematopoiesis, and storing essential minerals. Skeletal homeostasis, which includes aspects such as bone density, structural integrity, and regenerative processes, is essential for normal skeletal function. Autophagy, an intricate intracellular mechanism for degrading and recycling cellular components, plays a multifaceted role in bone metabolism. It involves sequestering cellular waste, damaged proteins, and organelles within autophagosomes, which are then degraded and recycled. Autophagy's impact on bone health varies depending on factors such as regulation, cell type, environmental cues, and physiological context. Despite being traditionally considered a cytoplasmic process, autophagy is subject to transcriptional and epigenetic regulation within the nucleus. However, the precise influence of epigenetic regulation, including DNA methylation, histone modifications, and non-coding RNA expression, on cellular fate remains incompletely understood. The interplay between autophagy and epigenetic modifications adds complexity to bone cell regulation. This article provides an in-depth exploration of the intricate interplay between these two regulatory paradigms, with a focus on the epigenetic control of autophagy in bone metabolism. Such an understanding enhances our knowledge of bone metabolism-related disorders and offers insights for the development of targeted therapeutic strategies.

Extracellular Vesicles and Immunity: At the Crossroads of Cell Communication

Extracellular vesicles (EVs), comprising exosomes and microvesicles, are small membranous structures secreted by nearly all cell types. They have emerged as crucial mediators in intercellular communication, playing pivotal roles in diverse physiological and pathological processes, notably within the realm of immunity. These roles go beyond mere cellular interactions, as extracellular vesicles stand as versatile and dynamic components of immune regulation, impacting both innate and adaptive immunity. Their multifaceted involvement includes immune cell activation, antigen presentation, and immunomodulation, emphasising their significance in maintaining immune homeostasis and contributing to the pathogenesis of immune-related disorders. Extracellular vesicles participate in immunomodulation by delivering a wide array of bioactive molecules, including proteins, lipids, and nucleic acids, thereby influencing gene expression in target cells. This manuscript presents a comprehensive review that encompasses in vitro and in vivo studies aimed at elucidating the mechanisms through which EVs modulate human immunity. Understanding the intricate interplay between extracellular vesicles and immunity is imperative for unveiling novel therapeutic targets and diagnostic tools applicable to various immunological disorders, including autoimmune diseases, infectious diseases, and cancer. Furthermore, recognising the potential of EVs as versatile drug delivery vehicles holds significant promise for the future of immunotherapies.

Newly discovered functions of miRNAs in neuropathic pain: Transitioning from recent discoveries to innovative underlying mechanisms

Neuropathic pain is a widespread clinical issue caused by somatosensory nervous system damage, affecting numerous individuals. It poses considerable economic and public health challenges, and managing it can be challenging due to unclear underlying mechanisms. Nevertheless, emerging evidence suggests that neurogenic inflammation and neuroinflammation play a role in developing pain patterns. Emerging evidence suggests that neurogenic inflammation and neuroinflammation play significant roles in developing neuropathic pain within the nervous system. Increased/decreased miRNA expression patterns could affect the progression of neuropathic and inflammatory pain by controlling nerve regeneration, neuroinflammation, and the expression of abnormal ion channels. However, our limited knowledge of miRNA targets hinders a complete grasp of miRNA's functions. Meanwhile, exploring exosomal miRNA, a recently uncovered role, has significantly advanced our comprehension of neuropathic pain's pathophysiology in recent times. In this review, we present a comprehensive overview of the latest miRNA studies and explore the possible ways miRNAs might play a role in the development of neuropathic pain.

Effect of Solanum lycopersicum and Citrus limon-Derived Exosome-Like Vesicles on Chondrogenic Differentiation of Adipose-Derived Stem Cells

Articular cartilage defect treatment is a very important problem because its therapeutic options are not successful enough. Due to the weak self-repairing capacity of the avascular cartilage, even minor damage can progress and cause joint damage leading to osteoarthritis. Although various treatment strategies have been developed to repair damaged cartilage, cell- and exosome-based therapies are promising. Plant extracts have been used for decades, and their effects on cartilage regeneration have been studied. Exosome-like vesicles, which are secreted by all living cells, are involved in cell-to-cell communication and cell homeostasis. The differentiation potential of exosome-like vesicles isolated from S. lycopersicum and C. limon, which are known to have anti-inflammatory and antioxidant properties, was investigated in the differentiation of human adipose-derived mesenchymal stem cells (hASCs) into chondrocytes. In order to obtain tomato-derived exosome-like vesicles (TELVs) and lemon-derived exosome-like vesicles (LELVs) Aquous Two- Phase system was performed. Characterisation of isolated vesicles based on size, shape were achived via Zetasizer, NTA FAME analysis, and SEM techniques. These results showed that TELVs and LELVs increased cell viability and did not show any toxic effects on stem cells. Although TELVs triggered chondrocyte formation, LELVs downregulated. The expression of ACAN, SOX9, and COMP, known as chondrocyte markers, was increased by TELV treatment. In addition, protein expression of the two most important proteins, COL2 and COLXI, found in the extracellular matrix of cartilage, increased. These findings suggest that TELVs can be used for cartilage regeneration, and may be a novel and promising treatment for osteoarthritis.

Epigenetic modification and exosome effects on autophagy in osteoarthritis

Osteoarthritis (OA) is a degenerative disease that leads to joint pain and stiffness and is one of the leading causes of disability and pain worldwide. Autophagy is a highly conserved self-degradation process, and its abnormal function is closely related to human diseases, including OA. Abnormal autophagy regulates cell aging, matrix metalloproteinase metabolism, and reactive oxygen metabolism, which are key in the occurrence and development of OA. There is evidence that drugs directly or indirectly targeting autophagy significantly hinder the progress of OA. In addition, the occurrence and development of autophagy in OA are regulated by many factors, including epigenetic modification, exosomes, crucial autophagy molecules, and signaling pathway regulation. Autophagy, as a new therapeutic target for OA, has widely influenced the pathological mechanism of OA. However, determining how autophagy affects OA pathology and its use in the treatment and diagnosis of targets still need further research.

Synovial fluid exosome-derived miR-182-5p alleviates osteoarthritis by downregulating TNFAIP8 and promoting autophagy through LC3 signaling

OBJECTIVE

To investigate the role of exosomal miRNAs from synovial fluid (SF) in osteoarthritis (OA) patients and investigate the underlying molecular mechanism.

METHODS

Degenerated knee tissues were collected from male and female OA patients. Enzyme-linked immunosorbent assay (ELISA) was used to detect the differences in the expression of inflammatory indicators, including TNF-α, IL-6, and IL-10, between the degenerative and injury groups. Exosomes were isolated from SF using the Exoquick kit, and a microarray was used to identify differentially expressed miRNAs (DEmiRNAs), which were analyzed using bioinformatics. The predicted relationship between DEmiRNAs and target genes was verified using a luciferase reporter gene assay. CCK-8 and transwell assays were used to assess cell viability and migration. Immunofluorescence and TUNEL assay were used to detect cell autophagy and apoptosis. The interaction between proteins was detected by immunoprecipitation and verified by Mab rescue assay.

RESULTS

The relative expression of TNF-α/IL6 was significantly higher in the degeneration group than in the injury group. The OA degeneration group released significantly more and smaller exosomes than the injury group. The expression of miR-182-5p was markedly reduced in OA patients and had a higher correlation with inflammatory indicators. Tumor necrosis factor α-induced protein 8 (TNFAIP8) was a target of miR-182-5p, and its overexpression promoted chondrocyte proliferation, migration, and invasion and enhanced the wound healing efficiency. We also found a direct interaction of TNFAIP8 with autophagy-related gene 3 (ATG3). TNFAIP8 triggered ATG3 LC3-mediated autophagy.

CONCLUSION

The downregulation of exosomal miR-182-5p inhibits OA degeneration by targeting TNFAIP8 via the ATG/LC3 pathway.

Extracellular Vesicles: Therapeutic Potential in Central Nervous System Trauma by Regulating Cell Death

CNS (central nervous system) trauma, which is classified as SCI (spinal cord injury) and TBI (traumatic brain injury), is gradually becoming a major cause of accidental death and disability worldwide. Many previous studies have verified that the pathophysiological mechanism underlying cell death and the subsequent neuroinflammation caused by cell death are pivotal factors in the progression of CNS trauma. Simultaneously, EVs (extracellular vesicles), membrane-enclosed particles produced by almost all cell types, have been proven to mediate cell-to-cell communication, and cell death involves complex interactions among molecules. EVs have also been proven to be effective carriers of loaded bioactive components to areas of CNS trauma. Therefore, EVs are promising therapeutic targets to cure CNS trauma. However, the link between EVs and various types of cell death in the context of CNS trauma remains unknown. Therefore, in this review, we summarize the mechanism underlying EV effects, the relationship between EVs and cell death and the pathophysiology underlying EV effects on the CNS trauma based on information in published papers. In addition, we discuss the prospects of applying EVs to the CNS as feasible therapeutic strategies for CNS trauma in the future.

The Role of Extracellular Vesicles in the Pathogenesis and Treatment of Rheumatoid Arthritis and Osteoarthritis

Cells can communicate with each other through extracellular vesicles (EVs), which are membrane-bound structures that transport proteins, lipids and nucleic acids. These structures have been found to mediate cellular differentiation and proliferation apoptosis, as well as inflammatory responses and senescence, among others. The cargo of these vesicles may include immunomodulatory molecules, which can then contribute to the pathogenesis of various diseases. By contrast, EVs secreted by mesenchymal stem cells (MSCs) have shown important immunosuppressive and regenerative properties. Moreover, EVs can be modified and used as drug carriers to precisely deliver therapeutic agents. In this review, we aim to summarize the current evidence on the roles of EVs in the progression and treatment of rheumatoid arthritis (RA) and osteoarthritis (OA), which are important and prevalent joint diseases with a significant global burden.

The Dual Role of Small Extracellular Vesicles in Joint Osteoarthritis: Their Global and Non-Coding Regulatory RNA Molecule-Based Pathogenic and Therapeutic Effects

OA is the most common joint disease that affects approximately 7% of the global population. Current treatment methods mainly relieve its symptoms with limited repairing effect on joint destructions, which ultimately contributes to the high morbidity rate of OA. Stem cell treatment is a potential regenerative medical therapy for joint repair in OA, but the uncertainty in differentiation direction and immunogenicity limits its clinical usage. Small extracellular vesicles (sEVs), the by-products secreted by stem cells, show similar efficacy levels but have safer regenerative repair effect without potential adverse outcomes, and have recently drawn attention from the broader research community. A series of research works and reviews have been performed in the last decade, providing references for the application of various exogenous therapeutic sEVs for treating OA. However, the clinical potential of target intervention involving endogenous pathogenic sEVs in the treatment of OA is still under-explored and under-discussed. In this review, and for the first time, we emphasize the dual role of sEVs in OA and explain the effects of sEVs on various joint tissues from both the pathogenic and therapeutic aspects. Our aim is to provide a reference for future research in the field.

The role of exosomes and their enhancement strategies in the treatment of osteoarthritis

With the increasingly prominent problem of population aging, osteoarthritis (OA), which is closely related to aging, has become a serious illness affecting the lives and health of elderly individuals. However, effective treatments are still lacking. OA is typically considered a low-grade inflammatory state. The inflammatory infiltration of macrophages, neutrophils, T cells, and other cells is common in diseased joints. These cells create the inflammatory environment of OA and are involved in the onset and progression of the disease. Exosomes, a type of complex vesicle containing abundant RNA molecules and proteins, play a crucial role in the physiological and pathological processes of an organism. In comparison to other therapeutic methods such as stem cells, exosomes have distinct advantages of precise targeting and low immunogenicity. Moreover, research and techniques related to exosomes are more mature, indicating a promising future in disease treatment. Many studies have shown that the impact of exosomes on the inflammatory microenvironment directly or indirectly leads to the occurrence of various diseases. Furthermore, exosomes can be helpful in the management of illnesses. This article provides a comprehensive review and update on the research of exosomes, a type of extracellular vesicle, in the treatment of OA by modulating the inflammatory microenvironment. It also combines innovative studies on the modification of exosomes. In general, the application of exosomes in the treatment of OA has been validated, and the introduction of modified exosome technology holds potential for enhancing its therapeutic efficacy.

Multi-Omic Temporal Landscape of Plasma and Synovial Fluid-Derived Extracellular Vesicles Using an Experimental Model of Equine Osteoarthritis

Extracellular vesicles (EVs) contribute to osteoarthritis pathogenesis through their release into joint tissues and synovial fluid. Synovial fluid-derived EVs have the potential to be direct biomarkers in the causal pathway of disease but also enable understanding of their role in disease progression. Utilizing a temporal model of osteoarthritis, we defined the changes in matched synovial fluid and plasma-derived EV small non-coding RNA and protein cargo using sequencing and mass spectrometry. Data exploration included time series clustering, factor analysis and gene enrichment interrogation. Chondrocyte signalling was analysed using luciferase-based transcription factor activity assays. EV protein cargo appears to be more important during osteoarthritis progression than small non-coding RNAs. Cluster analysis revealed plasma-EVs represented a time-dependent response to osteoarthritis induction associated with supramolecular complexes. Clusters for synovial fluid-derived EVs were associated with initial osteoarthritis response and represented immune/inflammatory pathways. Factor analysis for plasma-derived EVs correlated with day post-induction and were primarily composed of proteins modulating lipid metabolism. Synovial fluid-derived EVs factors represented intermediate filament and supramolecular complexes reflecting tissue repair. There was a significant interaction between time and osteoarthritis for CRE, NFkB, SRE, SRF with a trend for osteoarthritis synovial fluid-derived EVs at later time points to have a more pronounced effect.

The potential role of synovial cells in the progression and treatment of osteoarthritis

Osteoarthritis (OA), the commonest arthritis, is characterized by the progressive destruction of cartilage, leading to disability. The Current early clinical treatment strategy for OA often centers on anti-inflammatory or analgesia medication, weight loss, improved muscular function and articular cartilage repair. Although these treatments can relieve symptoms, OA tends to be progressive, and most patients require arthroplasty at the terminal stages of OA. Recent studies have shown a close correlation between joint pain, inflammation, cartilage destruction and synovial cells. Consequently, understanding the potential mechanisms associated with the action of synovial cells in OA could be beneficial for the clinical management of OA. Therefore, this review comprehensively describes the biological functions of synovial cells, the synovium, together with the pathological changes of synovial cells in OA, and the interaction between the cartilage and synovium, which is lacking in the present literature. Additionally, therapeutic approaches based on synovial cells for OA treatment are further discussed from a clinical perspective, highlighting a new direction in the treatment of OA.

Harnessing exosomes as cutting-edge drug delivery systems for revolutionary osteoarthritis therapy

Exosomes, remarkable extracellular vesicles, have emerged as an advanced frontier in intercellular communication. This remarkable capacity positions them as promising contenders in drug delivery systems (DDSs) for osteoarthritis (OA) therapy, capitalizing on their inherent biocompatibility, stability, and minimal immunogenicity. In this comprehensive review, we summarize the emerging developments surrounding exosome-based DDSs for OA therapy. Focusing on exosome origins, we meticulously explore the diverse sources contributing to their production, including invaluable stem cells, immune cells, and an array of other cell types. In addition, we unravel the underlying mechanisms of action that govern these exosome-borne therapeutics, illuminating the intricate interplay between exosomes and recipient cells. In summary, this review highlights the present challenges that permeate exosome-based DDSs for OA therapy. Through an in-depth exploration of the intricacies within this emerging field, this review aims to shed light on the future direction of exosome-based DDSs in OA. It serves as a bridge for fostering collaboration and collective efforts in reshaping the treatment landscape of OA.

BMP-7 modified exosomes derived from synovial mesenchymal stem cells attenuate osteoarthritis by M2 polarization of macrophages

Background

Although the exosomes derived from mesenchymal stem cells (MSCs) display a therapeutic effect on inflammatory diseases, its application on OA has great limitations due to lack of specificity and targeting. The current study aimed to elucidate the potential therapeutic role of bone morphogenetic proteins-7(BMP-7) modified synovial mesenchymal stem cells-derived exosomes (SMSCs-exo) on OA and mechanism.

Methods

For in vitro experiments, LPS-treated macrophages RAW264.7 were treated with SMSCs-exo (exo) or BMP-7 modified SMSCs-exos (BMP-7-exo). The levels of inflammatory factors were assessed by ELISA. Also, the proportion of iNOS and CD206 positive cells were quantified by flow cytometry. Chondrocytes and RAW264.7 were co-culture to evaluate the effects of macrophage polarization on chondrocytes cellular behaviors. This effect on KOA was verified by an experiment in vivo. HE staining and Safranin fast green staining were used to observe the damage of articular cartilage. Immunohistochemistry was used to determine the expression of collagen II and aggrecan in articular cartilage, as well as the expression of iNOS and CD206 in synovial tissues.

Results

Our in vitro results showed that BMP-7-exo treatment promoted LPS-induced proliferation of macrophages and chondrocytes, and showed a better ability to reduce inflammation by promoting macrophages M2 polarization. After co-culture with LPS treated macrophages, the proliferation rate and migration of chondrocytes were significantly decreased, while the apoptosis was significantly increased. The macrophages treated with BMP-7-exo and exo partially reversed these changes. The chondrocytes in BMP-7-exo group had higher proliferation rate and migration, as well as lower apoptosis compared with the exo group. Also, the in vivo results showed BMP-7-exo treatment improved the pathological changes of KOA and promoted synovial macrophages M2 polarization.

Conclusions

Our results demonstrated that BMP-7-exo attenuated KOA inflammation and cartilage injury by synovial macrophages M2 polarization, suggesting that BMP-7-exo carry much therapeutic potential for OA.

Construction of an immune-related lncRNA-miRNA-mRNA regulatory network in radiation-induced esophageal injury in rats

Radiation-induced esophageal injury (RIEI) is an adverse reaction of radiation therapy in patients with esophageal cancer, lung cancer and other malignant tumors. Competitive endogenous RNA (ceRNA) network is known to play a significant role in the onset and progression of many diseases, but the exact mechanism of ceRNA in RIEI has not been fully elucidated. In this study, rat esophaguses were obtained after conducting irradiation under different doses (0 Gy, 25 Gy, 35 Gy). Total RNA was extracted and mRNA, lncRNA, circRNA, and miRNA sequencing was performed. Multiple dose-dependent differentially expressed RNAs (dd-DERs), including 870 lncRNAs, 82 miRNAs, 2478 mRNAs, were obtained through the integration of differential expression analysis and dose-dependent screening (35 Gy ≥ 25 Gy > 0 Gy, or 35 Gy ≤ 25 Gy < 0 Gy). Co-expression analysis and prediction of the binding site in dd-DER were conducted and 27 lncRNAs, 20 miRNAs, and 168 mRNAs were selected to construct a ceRNA network. As the immune microenvironment is crucial for RIEI progression, we constructed an immune-related ceRNA network consisting of 11 lncRNAs, 9 miRNAs, and 9 mRNAs. The expression levels of these immune-related RNAs were verified by RT-qPCR. Immune infiltration analysis showed that the RNAs in the immune-related ceRNA network were mainly associated with the proportion of monocytes, M2 macrophages, activated NK cells, and activated CD4+ memory T cells. Drug sensitivity analysis was conducted based on the expression levels of mRNAs in the immune-related ceRNA network, and small molecule drugs with preventive and therapeutic effects on RIEI were identified. In summary, an immune-related ceRNA network associated with RIEI progression was constructed in this study. The findings provide useful information on new potential targets for the prevention and treatment of RIEI.

Arthritic Microenvironment-Dictated Fate Decisions for Stem Cells in Cartilage Repair

The microenvironment and stem cell fate guidance of post-traumatic articular cartilage regeneration is primarily the focus of cartilage tissue engineering. In articular cartilage, stem cells are characterized by overlapping lineages and uneven effectiveness. Within the first 12 weeks after trauma, the articular inflammatory microenvironment (AIME) plays a decisive role in determining the fate of stem cells and cartilage. The development of fibrocartilage and osteophyte hyperplasia is an adverse outcome of chronic inflammation, which results from an imbalance in the AIME during the cartilage tissue repair process. In this review, the sources for the different types of stem cells and their fate are summarized. The main pathophysiological events that occur within the AIME as well as their protagonists are also discussed. Additionally, regulatory strategies that may guide the fate of stem cells within the AIME are proposed. Finally, strategies that provide insight into AIME pathophysiology are discussed and the design of new materials that match the post-traumatic progress of AIME pathophysiology in a spatial and temporal manner is guided. Thus, by regulating an appropriately modified inflammatory microenvironment, efficient stem cell-mediated tissue repair may be achieved.

Exosomes from osteoarthritic fibroblast-like synoviocytes promote cartilage ferroptosis and damage via delivering microRNA-19b-3p to target SLC7A11 in osteoarthritis

Objective

Our previous studies revealed that normal synovial exosomes promoted chondrogenesis, and microRNA (miR)-19b-3p independently related to osteoarthritis (OA) risk. Subsequently, this study intended to further explore the effect of OA fibroblast-like synoviocyte (OA-FLS) exosomal miR-19b-3p on OA ferroptosis and its potential mechanisms.

Methods

Interleukin (IL)-1β-stimulated chondrocytes and medial meniscus surgery were used to construct the OA cellular model and the OA rat model, respectively. OA-FLS exosomes with/without miR-19b-3p modification were added to the IL-1β-stimulated chondrocytes and OA rat models, followed by direct miR-19b-3p mimic/inhibitor transfection with/without SLC7A11 overexpression plasmids. miR-19b-3p, ferroptosis-related markers (malondialdehyde (MDA), glutathione (GSH)/oxidized glutathione (GSSG), ferrous ion (Fe2+), glutathione peroxidase 4 (GPX4), solute carrier family 7 member 11 (SLC7A11), and acyl-CoA synthetase long-chain family member 4 (ACSL4)), mitochondrial membrane potential (MMP), and reactive oxygen species (ROS) levels were detected.

Results

Enhanced ferroptosis reflected by dysregulated ferroptosis-related markers, a reduced MMP, and an increased ROS was observed in cartilage tissues from OA patients vs. controls, IL-1β-stimulated chondrocytes vs. normal ones, and OA rat models vs. sham, so did miR-19b-3p. OA-FLS exosomes promoted MDA, Fe2+, ACSL4, and ROS but reduced cell viability, GSH/GSSG, GPX4, SLC7A11, and MMP in IL-1β-stimulated chondrocytes, whose effect was enhanced by miR-19b-3p mimics and attenuated by miR-19b-3p inhibitors. miR-19b-3p negatively regulated SLC7A11 and directly bound to SLC7A11 via luciferase reporter gene assay. Furthermore, SLC7A11 overexpression weakened miR-19b-3p mimics' effect on ferroptosis-related markers, MMP, or ROS in IL-1β-stimulated chondrocytes. OA-FLS exosomes also induced cartilage damage and ferroptosis in OA rats whose influence was tempered by miR-19b-3p inhibitors.

Conclusion

OA-FLS exosomal miR-19b-3p enhances cartilage ferroptosis and damage by sponging SLC7A11 in OA, indicating a potential linkage among synovium, cartilage, and ferroptosis during the OA process.

Current Knowledge and Future Perspectives of Exosomes as Nanocarriers in Diagnosis and Treatment of Diseases

Exosomes, as natural nanocarriers, characterized with low immunogenicity, non-cytotoxicity and targeted delivery capability, which have advantages over synthetic nanocarriers. Recently, exosomes have shown great potential as diagnostic markers for diseases and are also considered as a promising cell-free therapy. Engineered exosomes have significantly enhanced the efficacy and precision of delivering therapeutic agents, and are currently being extensively employed in targeted therapeutic investigations for various ailments, including oncology, inflammatory disorders, and degenerative conditions. Particularly, engineered exosomes enable therapeutic agent loading, targeted modification, evasion of MPS phagocytosis, intelligent control, and bioimaging, and have been developed as multifunctional nano-delivery platforms in recent years. The utilization of bioactive scaffolds that are loaded with exosome delivery has been shown to substantially augment retention, extend exosome release, and enhance efficacy. This approach has advanced from conventional hydrogels to nanocomposite hydrogels, nanofiber hydrogels, and 3D printing, resulting in superior physical and biological properties that effectively address the limitations of natural scaffolds. Additionally, plant-derived exosomes, which can participate in gut flora remodeling via oral administration, are considered as an ideal delivery platform for the treatment of intestinal diseases. Consequently, there is great interest in exosomes and exosomes as nanocarriers for therapeutic and diagnostic applications. This comprehensive review provides an overview of the biogenesis, composition, and isolation methods of exosomes. Additionally, it examines the pathological and diagnostic mechanisms of exosomes in various diseases, including tumors, degenerative disorders, and inflammatory conditions. Furthermore, this review highlights the significance of gut microbial-derived exosomes. Strategies and specific applications of engineered exosomes and bioactive scaffold-loaded exosome delivery are further summarized, especially some new techniques such as large-scale loading technique, macromolecular loading technique, development of multifunctional nano-delivery platforms and nano-scaffold-loaded exosome delivery. The potential benefits of using plant-derived exosomes for the treatment of gut-related diseases are also discussed. Additionally, the challenges, opportunities, and prospects of exosome-based nanocarriers for disease diagnosis and treatment are summarized from both preclinical and clinical viewpoints.

Immunomodulatory potential of mesenchymal stromal cell-derived extracellular vesicles in chondrocyte inflammation

Introduction

Osteoarthritis (OA) affects a large percentage of the population worldwide. Current surgical and nonsurgical concepts for treating OA only result in symptom-modifying effects. However, there is no disease-modifying therapy available. Extracellular vesicles released by mesenchymal stem/stromal cells (MSC-EV) are promising agents to positively influence joint homeostasis in the osteoarthritic surroundings. This pilot study aimed to investigate the effect of characterized MSC-EVs on chondrogenesis in a 3D chondrocyte inflammation model with the pro-inflammatory cytokine TNFα.

Methods

Bovine articular chondrocytes were expanded and transferred into pellet culture at passage 3. TNFα, human MSC-EV preparations (MSC-EV batches 41.5-EVi1 and 84-EVi), EVs from human platelet lysate (hPL4-EV), or the combination of TNFα and EVs were supplemented. To assess the effect of MSC-EVs in the chondrocyte inflammation model after 14 days, DNA, glycosaminoglycan (GAG), total collagen, IL-6, and NO release were quantified, and gene expression of anabolic (COL-II, aggrecan, COMP, and PRG-4), catabolic (MMP-3, MMP-13, ADAMTS-4 and ADAMTS-5), dedifferentiation (COL-I), hypertrophy (COL-X, VEGF), and inflammatory (IL-8) markers were analyzed; histological evaluation was performed using safranin O/Fast Green staining and immunohistochemistry of COL I and II. For statistical evaluation, nonparametric tests were chosen with a significance level of p < 0.05.

Results

TNFα supplementation resulted in catabolic stimulation with increased levels of NO and IL-6, upregulation of catabolic gene expression, and downregulation of anabolic markers. These findings were supported by a decrease in matrix differentiation (COL-II). Supplementation of EVs resulted in an upregulation of the chondrogenic marker PRG-4. All MSC-EV preparations significantly increased GAG retention per pellet. In contrast, catabolic markers and IL-8 expression were upregulated by 41.5-EVi1. Regarding protein levels, IL-6 and NO release were increased by 41.5-EVi1. Histologic and immunohistochemical evaluations indicated a higher differentiation potential of chondrocytes treated with 84-EVi.

Discussion

MSC-EVs can positively influence chondrocyte matrix production in pro-inflammatory surroundings, but can also stimulate inflammation. In this study MSC-EV 41.5-EVi1 supplementation increased chondrocyte inflammation, whereas MSC-84-EVi supplementation resulted a higher chondrogenic potential of chondrocytes in 3D pellet culture. In summary, the selected MSC-EVs exhibited promising chondrogenic effects indicating their significant potential for the treatment of OA; however, the functional heterogeneity in MSC-EV preparations has to be solved.

Extracellular vesicles in the treatment and prevention of osteoarthritis: can horses help us translate this therapy to humans?

Osteoarthritis (OA) is a common joint disease affecting humans and horses, resulting in significant morbidity, financial expense, and loss of athletic use. While the pathogenesis is incompletely understood, inflammation is considered crucial in the development and progression of the disease. Mesenchymal stromal cells (MSCs) have received increasing scientific attention for their anti-inflammatory, immunomodulatory, and pro-regenerative effects. However, there are concerns about their ability to become a commercially available therapeutic. Extracellular vesicles (EVs) are now recognized to play a crucial role in the therapeutic efficacy observed with MSCs and offer a potentially novel cell-free therapeutic that may negate many of the concerns with MSCs. There is evidence that EVs have profound anti-inflammatory, immunomodulatory, and pro-regenerative effects equal to or greater than the MSCs they are derived from in the treatment of OA. Most of these studies are in small animal models, limiting the translation of these results to humans. However, highly translational animal models are crucial for further understanding the efficacy of potential therapeutics and for close comparisons with humans. For this reason, the horse, which experiences the same gravitational impacts on joints similar to people, is a highly relevant large animal species for testing. The equine species has well-designed and validated OA models, and additionally, therapies can be further tested in naturally occurring OA to validate preclinical model testing. Therefore, the horse is a highly suitable model to increase our knowledge of the therapeutic potential of EVs.

Exosomes from chondrocytes overexpressing miR-214-3p facilitate M2 macrophage polarization and angiogenesis to relieve Legg Calvé-Perthes disease

OBJECTIVE

Legg-Calvé-Perthes disease (LCPD) is a partial or total necrosis of femoral head bone caused by blood supply disorder and its etiology is not clear. Studies have revealed that microRNA-214-3p (miR-214-3p) plays a vital role in LCPD, however, its exact mechanism is still unclear. In this study, we investigated the potential role of chondrocytes-derived exosomes carrying miR-214-3p (exos-miR-214-3p) in the pathogenesis of LCPD.

METHODS

RT-qPCR was performed to evaluate miR-214-3p expression level in femoral head cartilage, serum and chondrocytes of patients with LCPD, as well as dexamethasone (DEX)-exposed TC28 cells. Effects of exos-miR-214-3p on the proliferation and apoptosis were verified via MTT assay, TUNEL staining and caspase3 activity assay. The M2 macrophage markers were assessed by flow cytometry, RT-qPCR and Western blot. Moreover, angiogenic effects of human umbilical vein endothelial cells (HUVECs) were tested using CCK-8 and tube formation assays. Bioinformatics prediction, luciferase assay and ChIP were applied to verify the association between ATF7, RUNX1 and miR-214-3p.

RESULTS

miR-214-3p was found to be decreased in patients with LCPD and DEX-treated TC28 cells, of which overexpression promoted cell proliferation and suppressed apoptosis. Mechanistically, exos-miR-214-3p facilitated M2 polarization by ATF7/TLR4 axis and HUVECs angiogenesis via RUNX1/VEGFA axis.

CONCLUSION

miR-214-3p alleviates LCPD by promoting M2 polarization of macrophages and angiogenesis.

Ergothioneine inhibits the progression of osteoarthritis via the Sirt6/NF-κB axis both in vitro and in vivo

Osteoarthritis (OA), which is a major cause of serious arthralgia and disability among the elderly, has long plagued numerous populations. However, the specific molecular mechanisms involved in the etiology of OA are unclear. SIRT6 plays a critical function in the development of several inflammatory and aging-associated diseases. A study by D'Onofrio demonstrates that ergothioneine (EGT) is an effective activator of SIRT6. As revealed by previous reports, EGT exerts beneficial effects on the mouse body, including resistance to oxidation, tumor, and inflammation. Therefore, this work attempted to identify the inflammatory resistance of EGT and explore its effects on the incidence and development of OA. Mouse chondrocyte stimulation using varying levels of EGT and 10 ng/mL IL-1β. According to in vitro experiments, EGT significantly reduced the decomposition of collagen II and aggrecan in OA chondrocytes, as well as inhibited the overexpression of PGE2, NO, IL-6, TNF-α, iNOs, COX-2, MMP-13, and ADAMTS5. In the present work, EGT hindered the NF-κB activity by activating the SIRT6 pathway in OA chondrocytes, which in turn, significantly attenuated the inflammatory response resulting from IL to 1β. The inhibitory effect of EGT on the progression of OA was demonstrated by the mouse DMM model experiment. Thus, this study revealed that EGT was effective in anti-OA treatment.

Differential Expression of Non-Coding RNAs in Stem Cell Development and Therapeutics of Bone Disorders

Stem cells' self-renewal and multi-lineage differentiation are regulated by a complex network consisting of signaling factors, chromatin regulators, transcription factors, and non-coding RNAs (ncRNAs). Diverse role of ncRNAs in stem cell development and maintenance of bone homeostasis have been discovered recently. The ncRNAs, such as long non-coding RNAs, micro RNAs, circular RNAs, small interfering RNA, Piwi-interacting RNAs, etc., are not translated into proteins but act as essential epigenetic regulators in stem cells' self-renewal and differentiation. Different signaling pathways are monitored efficiently by the differential expression of ncRNAs, which function as regulatory elements in determining the fate of stem cells. In addition, several species of ncRNAs could serve as potential molecular biomarkers in early diagnosis of bone diseases, including osteoporosis, osteoarthritis, and bone cancers, ultimately leading to the development of new therapeutic strategies. This review aims to explore the specific roles of ncRNAs and their effective molecular mechanisms in the growth and development of stem cells, and in the regulation of osteoblast and osteoclast activities. Furthermore, we focus on and explore the association of altered ncRNA expression with stem cells and bone turnover.

Inflammaging and Osteoarthritis

Osteoarthritis is a highly prevalent disease particularly in subjects over 65 years of age worldwide. While in the past it was considered a mere consequence of cartilage degradation leading to anatomical and functional joint impairment, in recent decades, there has been a more dynamic view with the synovium, the cartilage, and the subchondral bone producing inflammatory mediators which ultimately lead to cartilage damage. Inflammaging is defined as a chronic, sterile, low-grade inflammation state driven by endogenous signals in the absence of infections, occurring with aging. This chronic status is linked to the production of reactive oxygen species and molecules involved in the development of age-related disease such as cancer, diabetes, and cardiovascular and neurodegenerative diseases. Inflammaging contributes to osteoarthritis development where both the innate and the adaptive immune response are involved. Elevated systemic and local inflammatory cytokines and senescent molecules promote cartilage degradation, and antigens derived from damaged joints further trigger inflammation through inflammasome activation. B and T lymphocyte populations also change with inflammaging and OA, with reduced regulatory functions, thus implicating self-reactivity as an additional mechanism of joint damage. The discovery of the underlying pathogenic pathways may help to identify potential therapeutic targets for the management or the prevention of osteoarthritis. We will provide a comprehensive evaluation of the current literature on the role of inflammaging in osteoarthritis and discuss the emerging therapeutic strategies.

Autophagy in the pathogenesis and therapeutic potential of post-traumatic osteoarthritis

Autophagy, as a fundamental mechanism for cellular homeostasis, is generally involved in the occurrence and progression of various diseases. Osteoarthritis (OA) is the most common musculoskeletal disease that often leads to pain, disability and economic loss in patients. Post-traumatic OA (PTOA) is a subtype of OA, accounting for >12% of the overall burden of OA. PTOA is often caused by joint injuries including anterior cruciate ligament rupture, meniscus tear and intra-articular fracture. Although a variety of methods have been developed to treat acute joint injury, the current measures have limited success in effectively reducing the incidence and delaying the progression of PTOA. Therefore, the pathogenesis and intervention strategy of PTOA need further study. In the past decade, the roles and mechanisms of autophagy in PTOA have aroused great interest in the field. It was revealed that autophagy could maintain the homeostasis of chondrocytes, reduce joint inflammatory level, prevent chondrocyte death and matrix degradation, which accordingly improved joint symptoms and delayed the progression of PTOA. Moreover, many strategies that target PTOA have been revealed to promote autophagy. In this review,  we summarize the roles and mechanisms of autophagy in PTOA and the current strategies for PTOA treatment that depend on autophagy regulation, which may be beneficial for PTOA patients in the future.

Soluble and EV-Associated Diagnostic and Prognostic Biomarkers in Knee Osteoarthritis Pathology and Detection

Osteoarthritis (OA) is the most common degenerative disease of the connective tissue of the human musculoskeletal system. Despite its widespread prevalence, there are many limitations in its diagnosis and treatment. OA diagnosis currently relies on the presence of clinical symptoms, sometimes accompanied by changes in joint X-rays or MRIs. Biomarkers help not only to diagnose early disease progression but also to understand the process of OA in many ways. In this article, we briefly summarize information on articular joints and joint tissues, the pathogenesis of OA and review the literature about biomarkers in the field of OA, specifically inflammatory cytokines/chemokines, proteins, miRNA, and metabolic biomarkers found in the blood, synovial fluid and in extracellular vesicles.

Synovial fibroblast-miR-214-3p-derived exosomes inhibit inflammation and degeneration of cartilage tissues of osteoarthritis rats

MicroRNAs (miRs) are regulators of number of cellular process. miRs enclosed within exosomes can be crucial regulators of intercellular signalling and could be an important biomarker of various age-associated disorders. Role of exosomal enclosed miRs in osteoarthritis (OA) chondrocytes and synovial fibroblasts (SFBs) remains poorly studied. Here, we profiled and studied the effect of synovial fluid-derived exosomal miRs on inflammation, survival, proliferation of chondrocyte in correlation with cartilage degeneration. Exosomes were isolated from synovial fluid collected from OA subjects and were analysed by transmission electron microscopy. miRs were isolated and were submitted to microarray profiling. Web-based PCR analysis was done. Chondrocyte proliferation and colony formation assay were performed. Apoptosis study was done by flow cytometer. Gene expression was done by qRT-PCR analysis and protein expression by western blot assay. Rat model of OA was created by operating the knee by anterior cruciate ligament and resection of medial menisci (ACLT + MMx) method. Micro-CT analysis, histological analysis, immunohistochemical staining, and TUNEL assay were also performed. About 17 miRs were found to be expressed differentially in the synovial fluid collected from the control and OA subjects. Microarray analysis confirmed, expression of miR-214-3p was significantly downregulated in the synovial fluid exosome of OA subjects. miR-214-3p mimic promoted proliferation of chondrocyte and suppressed apoptosis. Treatment also inhibited the levels of TNF-α, IL-1β and IL-6. SFB-miR-214-3p exosomes suppressed apoptosis and also inflammation in chondrocytes. In vivo study suggested that SFB-exosomal miR-214-3p from rats suppressed the formation of osteophytes, prevented degeneration of cartilage and exerted anti-inflammatory and anti-apoptotic effect in articular cartilage tissue. The findings suggested that SFB-miR-214-3p exosomes can ameliorate chondrocyte inflammation and degeneration of cartilage tissues. The study confirms therapeutic potential of SFB-miR-214-3p exosomes in treating OA.

Osteoarthritis models: From animals to tissue engineering

Osteoarthritis (OA) is a chronic degenerative osteoarthropathy. Although it has been revealed that a variety of factors can cause or aggravate the symptoms of OA, the pathogenic mechanisms of OA remain unknown. Reliable OA models that accurately reflect human OA disease are crucial for studies on the pathogenic mechanism of OA and therapeutic drug evaluation. This review first demonstrated the importance of OA models by briefly introducing the OA pathological features and the current limitations in the pathogenesis and treatment of OA. Then, it mainly discusses the development of different OA models, including animal and engineered models, highlighting their advantages and disadvantages from the perspective of pathogenesis and pathology analysis. In particular, the state-of-the-art engineered models and their potential were emphasized, as they may represent the future direction in the development of OA models. Finally, the challenges in obtaining reliable OA models are also discussed, and possible future directions are outlined to shed some light on this area.

Purified exosome product enhances chondrocyte survival and regeneration by modulating inflammation and promoting chondrogenesis

Aim: This study was to detect the effects of purified exosome product (PEP) on C28/I2 cells and chondrocytes derived from osteoarthritis patients. Materials & methods: Cell viability and apoptosis assays were used to detect the effect of PEP on cells. qRT-PCR and cell fluorescence assays were used to investigate the potential mechanism of PEP on cell chondrogenesis. Results: PEP was internalized by cells at a fast rate and enhanced cellular proliferation and migration while attenuating apoptosis. These findings reflect the fact that PEP can increase the expression of PCNA and reduce the expression of CASP3/7/9 and BAX. Conclusion: This study suggests an innovative strategy for chondrogenesis that could be applied to osteoarthritis repair in the future.

Extracellular vesicles in osteoarthritis of peripheral joint and temporomandibular joint

Osteoarthritis (OA) is a disabling disease with significant morbidity worldwide. OA attacks the large synovial joint, including the peripheral joints and temporomandibular joint (TMJ). As a representative of peripheral joint OA, knee OA shares similar symptoms with TMJ OA. However, these two joints also display differences based on their distinct development, anatomy, and physiology. Extracellular vesicles (EVs) are phospholipid bilayer nanoparticles, including exosomes, microvesicles, and apoptotic bodies. EVs contain proteins, lipids, DNA, micro-RNA, and mRNA that regulate tissue homeostasis and cell-to-cell communication, which play an essential role in the progression and treatment of OA. They are likely to partake in mechanical response, extracellular matrix degradation, and inflammatory regulation during OA. More evidence has shown that synovial fluid and synovium-derived EVs may serve as OA biomarkers. More importantly, mesenchymal stem cell-derived EV shows a therapeutic effect on OA. However, the different function of EVs in these two joints is largely unknown based on their distinct biological characteristic. Here, we reviewed the effects of EVs in OA progression and compared the difference between the knee joint and TMJ, and summarized their potential therapeutic role in the treatment of OA.

Emerging roles of miRNAs in neuropathic pain: From new findings to novel mechanisms

Neuropathic pain, which results from damage to the somatosensory nervous system, is a global clinical condition that affects many people. Neuropathic pain imposes significant economic and public health burdens and is often difficult to manage because the underlying mechanisms remain unclear. However, mounting evidence indicates a role for neurogenic inflammation and neuroinflammation in pain pattern development. There is increasing evidence that the activation of neurogenic inflammation and neuroinflammation in the nervous system contribute to neuropathic pain. Altered miRNA expression profiles might be involved in the pathogenesis of both inflammatory and neuropathic pain by regulating neuroinflammation, nerve regeneration, and abnormal ion channel expression. However, the lack of knowledge about miRNA target genes prevents a full understanding of the biological functions of miRNAs. At the same time, an extensive study on exosomal miRNA, a newly discovered role, has advanced our understanding of the pathophysiology of neuropathic pain in recent years. This section provides a comprehensive overview of the current understanding of miRNA research and discusses the potential mechanisms of miRNAs in neuropathic pain.

Effect of condylar chondrocyte exosomes on condylar cartilage osteogenesis in rats under tensile stress

Background: Functional orthoses are commonly used to treat skeletal Class II malocclusion, but the specific mechanism through which they do this has been a challenging topic in orthodontics. In the present study, we aimed to explore the effect of tensile stress on the osteogenic differentiation of condylar chondrocytes from an exosomal perspective. Methods: We cultured rat condylar chondrocytes under resting and tensile stress conditions and subsequently extracted cellular exosomes from them. We then screened miRNAs that were differentially expressed between the two exosome extracts by high-throughput sequencing and performed bioinformatics analysis and osteogenesis-related target gene prediction using the TargetScan and miRanda softwares. Exosomes cultured under resting and tensile stress conditions were co-cultured with condylar chondrocytes for 24 h to form the Control-Exo and Force-Exo exosome groups, respectively. Quantitative real time PCR(RT-qPCR) and western blotting were then used to determine the mRNA and protein expression levels of Runx2 and Sox9 in condylar chondrocytes. Results: The mRNA and protein expression levels of Runx2 and Sox9 in the Force-Exo group were significantly higher than those in the Control-Exo group (p < 0.05). The differential miRNA expression results were consistent with our sequencing results. Bioinformatics analysis and target gene prediction results showed that the main biological processes and molecular functions involved in differential miRNA expression in exosomes under tensile stress were biological processes and protein binding, respectively. Kyoto Gene and Genome Data Bank (KEGG) pathway enrichment analysis showed significant enrichment of differentially expressed miRNAs in the mTOR signaling pathway. The differentially expressed miRNAs were found to target osteogenesis-related genes. Conclusion: These results suggest that stimulation of rat condylar chondrocytes with tensile stress can alter the expression levels of certain miRNAs in their exosomes and promote their osteogenic differentiation. Exosomes under tensile stress culture conditions thus have potential applications in the treatment of Osteoarthritis (OA).