BMSC-Derived Exosomes Ameliorate Osteoarthritis by Inhibiting Pyroptosis of Cartilage via Delivering miR-326 Targeting HDAC3 and STAT1//NF-κB p65 to Chondrocytes

The role of extracellular vesicles in pyroptosis-mediated infectious and non-infectious diseases

Pyroptosis, a lytic and pro-inflammatory cell death, is important in various pathophysiological processes. Host- and bacteria-derived extracellular vesicles (EVs), as natural nanocarriers messengers, are versatile mediators of intercellular communication between different types of cells. Recently, emerging research has suggested that EVs exhibit multifaceted roles in disease progression by manipulating pyroptosis. This review focuses on new findings concerning how EVs shape disease progression in infectious and non-infectious diseases by regulating pyroptosis. Understanding the characteristics and activity of EVs-mediated pyroptotic death may conducive to the discovery of novel mechanisms and more efficient therapeutic targets in infectious and non-infectious diseases.

Mesenchymal stem cell-derived extracellular vesicles in joint diseases: Therapeutic effects and underlying mechanisms

Joint diseases greatly impact the daily lives and occupational functioning of patients globally. However, conventional treatments for joint diseases have several limitations, such as unsatisfatory efficacy and side effects, necessitating the exploration of more efficacious therapeutic strategies. Mesenchymal stem cell (MSC)-derived EVs (MSC-EVs) have demonstrated high therapeutic efficacyin tissue repair and regeneration, with low immunogenicity and tumorigenicity. Recent studies have reported that EVs-based therapy has considerable therapeutic effects against joint diseases, including osteoarthritis, tendon and ligament injuries, femoral head osteonecrosis, and rheumatoid arthritis. Herein, we review the therapeutic potential of various types of MSC-EVs in the aforementioned joint diseases, summarise the mechanisms underlying specific biological effects of MSC-EVs, and discuss future prospects for basic research on MSC-EV-based therapeutic modalities and their clinical translation. In general, this review provides an in-depth understanding of the therapeutic effects of MSC-EVs in joint diseases, as well as the underlying mechanisms, which may be beneficial to the clinical translation of MSC-EV-based treatment. The translational potential of this article: MSC-EV-based cell-free therapy can effectively promote regeneration and tissue repair. When used to treat joint diseases, MSC-EVs have demonstrated desirable therapeutic effects in preclinical research. This review may supplement further research on MSC-EV-based treatment of joint diseases and its clinical translation.

Mesenchymal stem cells and their extracellular vesicles in bone and joint diseases: targeting the NLRP3 inflammasome

The nucleotide-binding oligomerization domain-like-receptor family pyrin domain-containing 3 (NLRP3) inflammasome is a cytosolic multi-subunit protein complex, and recent studies have demonstrated the vital role of the NLRP3 inflammasome in the pathological and physiological conditions, which cleaves gasdermin D to induce inflammatory cell death called pyroptosis and mediates the release of interleukin-1 beta and interleukin-18 in response to microbial infection or cellular injury. Over-activation of the NLRP3 inflammasome is associated with the pathogenesis of many disorders affecting bone and joints, including gouty arthritis, osteoarthritis, rheumatoid arthritis, osteoporosis, and periodontitis. Moreover, mesenchymal stem cells (MSCs) have been discovered to facilitate the inhibition of NLRP3 and maybe ideal for treating bone and joint diseases. In this review, we implicate the structure and activation of the NLRP3 inflammasome along with the detail on the involvement of NLRP3 inflammasome in bone and joint diseases pathology. In addition, we focused on MSCs and MSC-extracellular vesicles targeting NLRP3 inflammasomes in bone and joint diseases. Finally, the existing problems and future direction are also discussed.

The C5AR1/TNFSF13B axis alleviates osteoarthritis by activating the PI3K/Akt/GSK3β/Nrf2/HO-1 pathway to inhibit ferroptosis

Chondrocyte ferroptosis induces the occurrence of osteoarthritis (OA). As a key gene of OA, C5a receptor 1 (C5AR1) is related to ferroptosis. Here, we investigated whether C5AR1 interferes with chondrocyte ferroptosis during OA occurrence. C5AR1 was downregulated in PA-treated chondrocytes. Overexpression of C5AR1 increased the cell viability and decreased ferroptosis in chondrocytes. Moreover, Tumor necrosis factor superfamily member 13B (TNFSF13B) was downregulated in PA-treated chondrocytes, and knockdown of TNFSF13B eliminated the inhibitory effect of C5AR1 on ferroptosis in chondrocytes. More importantly, the PI3K/Akt/GSK3β/Nrf2/HO-1 pathway inhibitor LY294002 reversed the inhibition of C5AR1 or TNFSF13B on ferroptosis in chondrocytes. Finally, we found that C5AR1 alleviated joint tissue lesions and ferroptosis in rats and inhibited the progression of OA in the rat OA model constructed by anterior cruciate ligament transection (ACLT), which was reversed by interfering with TNFSF13B. This study shows that C5AR1 reduces the progression of OA by upregulating TNFSF13B to activate the PI3K/Akt/GSK3β/Nrf2/HO-1 pathway and thereby inhibiting chondrocyte sensitivity to ferroptosis, indicating that C5AR1 may be a potential therapeutic target for ferroptosis-related diseases.

Osteoarthritis rat serum-derived extracellular vesicles aggravate osteoarthritis development by inducing NLRP3-mediated pyroptotic cell death and cellular inflammation

Osteoarthritis (OA), degenerative joint disease, is the most prevalent form of arthritis worldwide. Besides its substantial burden on society, the high OA morbidity greatly diminishes patients' quality of life. According to recent research, patients-derived serum extracellular vesicles (EVs) are critically involved in sustaining the corresponding disease progression. However, limited research has fully explored the specific functions and molecular mechanisms of OA serum-derived EVs in disease progression. Consequently, we aimed to investigate the underlying mechanism of OA rats-derived serum EVs in regulating OA progression. Before constructing the exosome-cell co-culture system, EVs were extracted from OA and control rat serum and co-cultured with bone marrow mesenchymal stem cells (BM-MSCs). Western blotting (WB), RT-qPCR, and enzyme-linked immunosorbent assay (ELISA) results revealed that OA rat serum-derived EVs upregulated cell pyroptosis-related markers, including nod-Like receptor protein-3 (NLRP3), apoptosis-associated speck-like protein (ASC), gasdermin D (GSDMD), and cleaved caspase-1. The OA rat-EVs also induced the release of LDH and inflammatory cytokines, including interleukin (IL)-1β, IL-18, IL-6, and TNF-α. Additional experiments revealed that OA rat-EVs delivered miR-133a-3p to BM-MSCs and upregulated miR-133a-3p to degrade sirtuin 1 (SIRT1), and activating the downstream NF-κB signaling pathway. Furthermore, the rescuing experiments confirmed that silencing SIRT1 abrogated the miR-133a-3p-induced protective effects in OA-EVs-treated BM-MSCs. In conclusion, OA rats-derived miR-133a-3p-containing EVs modulated the downstream SIRT1/NF-κB pathway-mediated pyroptotic cell death and inflammation in OA. In other words, this study confirmed the role and underlying mechanisms by which OA-associated serum EVs regulate pyroptosis and inflammation response in OA development.

Therapeutics of the future: Navigating the pitfalls of extracellular vesicles research from an osteoarthritis perspective

Extracellular vesicles have gained wide momentum as potential therapeutics for osteoarthritis, a highly prevalent chronic disease that still lacks an approved treatment. The membrane-bound vesicles are secreted by all cells carrying different cargos that can serve as both disease biomarkers and disease modifiers. Nonetheless, despite a significant peak in research regarding EVs as OA therapeutics, clinical implementation seems distant. In addition to scalability and standardization challenges, researchers often omit to focus on and consider the proper tropism of the vesicles, the practicality and relevance of their source, their low native therapeutic efficacy, and whether they address the disease as a whole. These considerations are necessary to better understand EVs in a clinical light and have been comprehensively discussed and ultimately summarized in this review into a conceptualized framework termed the nanodiamond concept. Future perspectives are also discussed, and alternatives are presented to address some of the challenges and concerns.

Cinnamaldehyde-Treated Bone Marrow Mesenchymal-Stem-Cell-Derived Exosomes via Aqueous Two-Phase System Attenuate IL-1β-Induced Inflammation and Catabolism via Modulation of Proinflammatory Signaling Pathways

Osteoarthritis (OA) is a degenerative joint disorder that is distinguished by inflammation and chronic cartilage damage. Interleukin-1β (IL-1β) is a proinflammatory cytokine that plays an important role in the catabolic processes that underlie the pathogenesis of OA. In this study, we investigate the therapeutic efficacy of exosomes derived from untreated bone-marrow-derived mesenchymal stem cells (BMMSC-Exo) and those treated with cinnamaldehyde (BMMSC-CA-Exo) for preventing the in vitro catabolic effects of IL-1β on chondrocytes. We stimulated chondrocytes with IL-1β to mimic the inflammatory microenvironment of OA. We then treated these chondrocytes with BMMSC-Exo and BMMSC-CA-Exo isolated via an aqueous two-phase system and evaluated their effects on the key cellular processes using molecular techniques. Our findings revealed that treatment with BMMSC-Exo reduces the catabolic effects of IL-1β on chondrocytes and alleviates inflammation. However, further studies directly comparing treatments with BMMSC-Exo and BMMSC-CA-Exo are needed to determine if CA preconditioning can provide additional anti-inflammatory benefits to the exosomes beyond those of CA preconditioning or treatment with regular BMMSC-Exo. Through a comprehensive molecular analysis, we elucidated the regulatory mechanisms underlying this protective effect. We found a significant downregulation of proinflammatory signaling pathways in exosome-infected chondrocytes, suggesting the potential modulation of the NF-κB and MAPK signaling cascades. Furthermore, our study identified the molecular cargo of BMMSC-Exo and BMMSC-CA-Exo, determining the key molecules, such as anti-inflammatory cytokines and cartilage-associated factors, that may contribute to their acquisition of chondroprotective properties. In summary, BMMSC-Exo and BMMSC-CA-Exo exhibit the potential as therapeutic agents for OA by antagonizing the in vitro catabolic effects of IL-1β on chondrocytes. The regulation of the proinflammatory signaling pathways and bioactive molecules delivered by the exosomes suggests a multifaceted mechanism of action. These findings highlight the need for further investigation into exosome-based therapies for OA and joint-related diseases.

Advanced gene nanocarriers/scaffolds in nonviral-mediated delivery system for tissue regeneration and repair

Tissue regeneration technology has been rapidly developed and widely applied in tissue engineering and repair. Compared with traditional approaches like surgical treatment, the rising gene therapy is able to have a durable effect on tissue regeneration, such as impaired bone regeneration, articular cartilage repair and cancer-resected tissue repair. Gene therapy can also facilitate the production of in situ therapeutic factors, thus minimizing the diffusion or loss of gene complexes and enabling spatiotemporally controlled release of gene products for tissue regeneration. Among different gene delivery vectors and supportive gene-activated matrices, advanced gene/drug nanocarriers attract exceptional attraction due to their tunable physiochemical properties, as well as excellent adaptive performance in gene therapy for tissue regeneration, such as bone, cartilage, blood vessel, nerve and cancer-resected tissue repair. This paper reviews the recent advances on nonviral-mediated gene delivery systems with an emphasis on the important role of advanced nanocarriers in gene therapy and tissue regeneration.

LncRNA SNHG1 enhances cartilage regeneration by modulating chondrogenic differentiation and angiogenesis potentials of JBMMSCs via mitochondrial function regulation

BACKGROUND

Cartilage is a kind of avascular tissue, and it is difficult to repair itself when it is damaged. In this study, we investigated the regulation of chondrogenic differentiation and vascular formation in human jaw bone marrow mesenchymal stem cells (h-JBMMSCs) by the long-chain noncoding RNA small nucleolar RNA host gene 1 (SNHG1) during cartilage tissue regeneration.

METHODS

JBMMSCs were isolated from the jaws via the adherent method. The effects of lncRNA SNHG1 on the chondrogenic differentiation of JBMMSCs in vitro were detected by real-time fluorescence quantitative polymerase chain reaction (RT-qPCR), Pellet experiment, Alcian blue staining, Masson's trichrome staining, and modified Sirius red staining. RT-qPCR, matrix gel tube formation, and coculture experiments were used to determine the effect of lncRNA SNHG1 on the angiogenesis in JBMMSCs in vitro. A model of knee cartilage defects in New Zealand rabbits and a model of subcutaneous matrix rubber suppositories in nude mice were constructed for in vivo experiments. Changes in mitochondrial function were detected via RT-qPCR, dihydroethidium (DHE) staining, MitoSOX staining, tetramethyl rhodamine methyl ester (TMRM) staining, and adenosine triphosphate (ATP) detection. Western blotting was used to detect the phosphorylation level of signal transducer and activator of transcription 3 (STAT3).

RESULTS

Alcian blue staining, Masson's trichrome staining, and modified Sirius Red staining showed that lncRNA SNHG1 promoted chondrogenic differentiation. The lncRNA SNHG1 promoted angiogenesis in vitro and the formation of microvessels in vivo. The lncRNA SNHG1 promoted the repair and regeneration of rabbit knee cartilage tissue. Western blot and alcian blue staining showed that the JAK inhibitor reduced the increase of STAT3 phosphorylation level and staining deepening caused by SNHG1. Mitochondrial correlation analysis revealed that the lncRNA SNHG1 led to a decrease in reactive oxygen species (ROS) levels, an increase in mitochondrial membrane potential and an increase in ATP levels. Alcian blue staining showed that the ROS inhibitor significantly alleviated the decrease in blue fluorescence caused by SNHG1 knockdown.

CONCLUSIONS

The lncRNA SNHG1 promotes chondrogenic differentiation and angiogenesis of JBMMSCs. The lncRNA SNHG1 regulates the phosphorylation of STAT3, reduces the level of ROS, regulates mitochondrial energy metabolism, and ultimately promotes cartilage regeneration.

Pyroptosis: A spoiler of peaceful coexistence between cells in degenerative bone and joint diseases

BACKGROUND

As people age, degenerative bone and joint diseases (DBJDs) become more prevalent. When middle-aged and elderly people are diagnosed with one or more disorders such as osteoporosis (OP), osteoarthritis (OA), and intervertebral disc degeneration (IVDD), it often signals the onset of prolonged pain and reduced functionality. Chronic inflammation has been identified as the underlying cause of various degenerative diseases, including DBJDs. Recently, excessive activation of pyroptosis, a form of programed cell death (PCD) mediated by inflammasomes, has emerged as a primary driver of harmful chronic inflammation. Consequently, pyroptosis has become a potential target for preventing and treating DBJDs.

AIM OF REVIEW

This review explored the physiological and pathological roles of the pyroptosis pathway in bone and joint development and its relation to DBJDs. Meanwhile, it elaborated the molecular mechanisms of pyroptosis within individual cell types in the bone marrow and joints, as well as the interplay among different cell types in the context of DBJDs. Furthermore, this review presented the latest compelling evidence supporting the idea of regulating the pyroptosis pathway for DBJDs treatment, and discussed the potential, limitations, and challenges of various therapeutic strategies involving pyroptosis regulation.

KEY SCIENTIFIC CONCEPTS OF REVIEW

In summary, an interesting identity for the unregulated pyroptosis pathway in the context of DBJDs was proposed in this review, which was undertaken as a spoiler of peaceful coexistence between cells in a degenerative environment. Over the extended course of DBJDs, pyroptosis pathway perpetuated its activity through crosstalk among pyroptosis cascades in different cell types, thus exacerbating the inflammatory environment throughout the entire bone marrow and joint degeneration environment. Correspondingly, pyroptosis regulation therapy emerged as a promising option for clinical treatment of DBJDs.

Aryl Hydrocarbon Receptor Activation Limits the Fatty Acid Synthesis and Subsequent "miR-193a-3p-HDAC3-FASN" Signals to Alleviate Intestinal Fibrosis

Intestinal fibrosis is a common complication of Crohn's disease and characterized by excessive extracellular matrix (ECM) deposition. The aryl hydrocarbon receptor (AhR) detects micronutrients and microbial metabolites in diet and can attenuate intestinal fibrosis with unclear mechanisms. In this study, AhR activation was demonstrated to downregulate the transcription of collagen I and fibronectin in a Sp1- but not Sp3- or AP-1-dependent manner. A suppressed fatty acid synthesis was highlighted using untargeted metabolomics analyses, and synthetic products, palmitic acid (PA), were used as the intermediary agent. After a screening study, fatty acid synthase (FASN) was identified as the main targeted protein, and AhR activation regulated "HDAC3-acetylation" signals but not glycosylation to enhance FASN degradation. Furthermore, results of bioinformatics analysis and others showed that after being activated, AhR targeted miR-193a-3p to control HDAC3 transcription. Collectively, AhR activation inhibited ECM deposition and alleviated intestinal fibrosis by limiting fatty acid synthesis subsequent to the inhibition of "miR-193a-3p-HDAC3-FASN" signals.

Therapeutic potential of mesenchymal stem cell-derived exosomes in skeletal diseases

Skeletal diseases impose a considerable burden on society. The clinical and tissue-engineering therapies applied to alleviate such diseases frequently result in complications and are inadequately effective. Research has shifted from conventional therapies based on mesenchymal stem cells (MSCs) to exosomes derived from MSCs. Exosomes are natural nanocarriers of endogenous DNA, RNA, proteins, and lipids and have a low immune clearance rate and good barrier penetration and allow targeted delivery of therapeutics. MSC-derived exosomes (MSC-exosomes) have the characteristics of both MSCs and exosomes, and so they can have both immunosuppressive and tissue-regenerative effects. Despite advances in our knowledge of MSC-exosomes, their regulatory mechanisms and functionalities are unclear. Here we review the therapeutic potential of MSC-exosomes for skeletal diseases.

Exosomal long non-coding RNA AU020206 alleviates macrophage pyroptosis in atherosclerosis by suppressing CEBPB-mediated NLRP3 transcription

Recent studies have suggested exosomes (EXO) as potential therapeutic tools for cardiovascular diseases, including atherosclerosis (AS). This study investigates the function of bone marrow stem cell (BMSC)-derived exosomes (EXO) on macrophage pyroptosis in AS and explores the associated mechanism. BMSC-EXO were isolated from healthy mice and identified. RAW264.7 cells (mouse macrophages) were exposed to oxLDL to simulate an AS condition. BMSC-EXO treatment enhanced viability and reduced lactate dehydrogenase release of macrophages. An animal model of AS was established using ApoE-/- mice. BMSC-EXO treatment suppressed plaque formation as well as macrophage and lipid infiltration in mouse aortic tissues. Moreover, BMSC-EXO decreased concentrations of pyroptosis-related markers interleukin (IL)-1β, IL-18, cleaved-caspase-1 and gasdermin D in vitro and in vivo. Long non-coding RNA AU020206 was carried by the BMSC-EXO, and it bound to CCAAT enhancer binding protein beta (CEBPB) to block CEBPB-mediated transcriptional activation of NLR family pyrin domain containing 3 (NLRP3). Functional assays revealed that silencing of AU020206 aggravated macrophage pyroptosis and exacerbated AS symptoms in mice. These exacerbations were blocked upon CEBPB silencing but then restored after NLRP3 overexpression. In conclusion, this study demonstrates that AU020206 delivered by BMSC-EXO alleviates macrophage pyroptosis in AS by blocking CEBPB-mediated transcriptional activation of NLRP3.

Mesenchymal stem cell-derived extracellular vesicles: a regulator and carrier for targeting bone-related diseases

The escalating threat of bone-related diseases poses a significant challenge to human health. Mesenchymal stem cell (MSC)-derived extracellular vesicles (MSC-EVs), as inherent cell-secreted natural products, have emerged as promising treatments for bone-related diseases. Leveraging outstanding features such as high biocompatibility, low immunogenicity, superior biological barrier penetration, and extended circulating half-life, MSC-EVs serve as potent carriers for microRNAs (miRNAs), long no-code RNAs (lncRNAs), and other biomolecules. These cargo molecules play pivotal roles in orchestrating bone metabolism and vascularity through diverse mechanisms, thereby contributing to the amelioration of bone diseases. Additionally, engineering modifications enhance the bone-targeting ability of MSC-EVs, mitigating systemic side effects and bolstering their clinical translational potential. This review comprehensively explores the mechanisms through which MSC-EVs regulate bone-related disease progression. It delves into the therapeutic potential of MSC-EVs as adept drug carriers, augmented by engineered modification strategies tailored for osteoarthritis (OA), rheumatoid arthritis (RA), osteoporosis, and osteosarcoma. In conclusion, the exceptional promise exhibited by MSC-EVs positions them as an excellent solution with considerable translational applications in clinical orthopedics.

Control of articular degeneration by extracellular vesicles from stem/stromal cells as a potential strategy for the treatment of osteoarthritis

Osteoarthritis (OA) is a degenerative joint condition that contributes to years lived with disability. Current therapeutic approaches are limited as there are no disease-modifying interventions able to delay or inhibit the progression of disease. In recent years there has been an increasing interest in the immunomodulatory and regenerative properties of mesenchymal stem/stromal cells (MSCs) to develop new OA therapies. Extracellular vesicles (EVs) mediate many of the biological effects of these cells and may represent an alternative avoiding the limitations of cell-based therapy. There is also a growing interest in EV modifications to enhance their efficacy and applications. Recent preclinical studies have provided strong evidence supporting the potential of MSC EVs for the development of OA treatments. Thus, MSC EVs may regulate chondrocyte functions to avoid cartilage destruction, inhibit abnormal subchondral bone metabolism and synovial tissue alterations, and control pain behavior. EV actions may be mediated by the transfer of their cargo to target cells, with an important role for proteins and non-coding RNAs modulating signaling pathways relevant for OA progression. Nevertheless, additional investigations are needed concerning EV optimization, and standardization of preparation procedures. More research is also required for a better knowledge of possible effects on different OA phenotypes, pharmacokinetics, mechanism of action, long-term effects and safety profile. Furthermore, MSC EVs have a high potential as vehicles for drug delivery or as adjuvant therapy to potentiate or complement the effects of other approaches.

Exosomes Derived from Quercetin-Treated Bone Marrow Derived Mesenchymal Stem Cells Inhibit the Progression of Osteoarthritis Through Delivering miR-124-3p to Chondrocytes

Osteoarthritis (OA) is a chronic disease characterized by the progressive loss of cartilage and failure of the diarrheal joint. Quercetin has been reported to attenuate the development of OA. Bone marrow derived mesenchymal stem cell (BMSC)-derived exosomes are involved in OA progression. However, the role of BMSC-derived exosomes in quercetin-mediated progression of OA remains unclear. Western blotting and RT-qPCR were used to assess protein and mRNA levels, respectively. CCK8 assay was performed to assess cell viability, and cell apoptosis was assessed using flow cytometry. A dual-luciferase assay was performed to assess the relationship between miR-124-3p and TRAF6 expression. Furthermore, in vivo experiments were performed to test the function of exosomes derived from Quercetin-treated BMSCs in OA patients. IL-1β significantly inhibited the viability of chondrocytes, whereas the conditioned medium of Quercetin-treated BMSCs (BMSCsQUE-CM) reversed this phenomenon through exosomes. IL-1β notably upregulated MMP13 and ADAMT5 and reduced the expression of COL2A1 in chondrocytes, which were rescued by BMSCsQUE-CM. The effects of BMSCsQUE-CM on these three proteins were reversed in the absence of exosomes. Exosomes can be transferred from BMSCs to chondrocytes, and exosomes derived from Quercetin-treated BMSCs (BMSCsQue-Exo) can reverse the apoptotic effects of IL-1β on chondrocytes. The level of miR-124-3p in BMSCs was significantly upregulated by quercetin, and miR-124-3p was enriched in BMSCsQue-Exo. TRAF6 was identified as a direct target of miR-124-3p, and BMSCsQue-Exo abolished the IL-1β-induced activation of MAPK/p38 and NF-κB signaling. Furthermore, BMSCsQue-Exo significantly attenuated OA progression in vivo. Exosomes derived from Quercetin-treated BMSCs inhibited OA progression through the upregulation of miR-124-3p.

What do osteoporosis and osteoarthritis have in common? An integrated study of overlapping differentially expressed genes in bone mesenchymal stem cells of osteoporosis and osteoarthritis

OBJECTIVE

For identification of aberrantly expressed genes in mesenchymal stem cells of osteoporosis (OP) and osteoarthritis (OA), Gene Expression Omnibus (GEO) datasets were integrated to investigate the intersection point.

METHODS

GSE35958 (osteoporosis) and GSE19664 (osteoarthritis) datasets were obtained from GEO database. The abnormally expressed genes were analyzed by GEO2R. Functional enrichment was explored by Metascape database and R software. The String database and Cytoscape software were used to build the protein-protein interaction network and identify hub genes. GSE35957 and GSE116925 were used as verification datasets. Single-cell analysis and pseudotime analysis were undertaken. CTDbase, Network Analyst, HPA database, HERB database and MIRW database were used to research the information, tissue and cell distribution, regulation, interaction and ingredients targeting the hub genes. Additionally, in vitro experiments such as RT-PCR, ALP staining and immunofluorescence were undertaken as verification tests.

RESULTS

Ten hub genes were identified in this study. All these genes play an important role in bone or cartilage generation. They have diagnostic values and therapeutic potential for OA and OP. Single-cell analysis visualized the cell distribution and pseudotime distribution of these genes. Some potential therapeutic ingredients of these genes were identified, such as curcumin, wogonin and glycerin. In vitro experiments, RT-PCR results showed that COL9A3 and MMP3 were downregulated and PTH1R was upregulated during osteogenic induction of BMSC. Immunohistochemical results showed the expression trend of MMP3 and COL2A1.

CONCLUSION

Ten abnormal hub genes of osteoporosis and osteoarthritis were identified successfully by this study. They were important regulatory genes for healthy bone and cartilage. These genes could be the common connections between osteoporosis and osteoarthritis as well as treatment targets. Further study of the regulatory mechanism and treatment effects of these genes would be valuable. The results of this study could contribute to further research.

Exosomal miR-182 derived from bone marrow mesenchymal stem cells drives carfilzomib resistance of multiple myeloma cells by targeting SOX6

BACKGROUND

Multiple myeloma (MM) is a common hematological malignancy. Drug resistance remains to be a major clinical challenge in MM therapy. In this study, we aim to investigate the functional roles of bone marrow mesenchymal stem cells (BMSC)-derived exosomal miR-182 on the carfilzomib resistance of MM and its underlying mechanism.

METHODS

qRT-PCR and Western blot methods were utilized to confirm the gene or protein expressions. CCK-8 and transwell assays were performed to measure the capabilities of proliferation, migration, and invasion. The molecular interactions were validated through ChIP and Dual luciferase assay.

RESULTS

Our findings indicated that miR-182 expression was upregulated in serum, BMSCs and BMSC-derived exosomes from MM patients. Hypoxia-inducible factor-1α (HIF-1α), a key transcriptional factor in tumor microenvironment, could boost miR-182 expression by directly binding to its promoter, thus favoring exosomal secretion. Moreover, exosomal miR-182 from BMSCs could be transferred to MM cells and was able to promote malignant proliferation, metastasis, and invasion, as well as decrease the sensitivity of MM cells against carfilzomib. Additionally, SOX6 was identified as a downstream target of miR-182 in MM cells, and its expression was negatively regulated by miR-182. Rescue experiments proved that loss of SOX6 in MM cells dramatically reversed the promoting roles of BMSC-secreted exosomal miR-182 on proliferation, metastasis, and carfilzomib resistance in MM cells.

CONCLUSION

Collectively, our findings indicated that exosomal miR-182 derived from BMSCs contributed to the metastasis and carfilzomib resistance of MM cells by targeting SOX6. This study sheds light on the pathogenesis of the BMSC-derived exosome containing miR-182 in the malignant behaviors of MM cells and carfzomib resistance.

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.

Strategies for Cartilage Repair in Osteoarthritis Based on Diverse Mesenchymal Stem Cells-Derived Extracellular Vesicles

Osteoarthritis (OA) causes disability and significant economic and social burden. Cartilage injury is one of the main pathological features of OA, and is often manifested by excessive chondrocyte death, inflammatory response, abnormal bone metabolism, imbalance of extracellular matrix (ECM) metabolism, and abnormal vascular or nerve growth. Regrettably, due to the avascular nature of cartilage, its capacity to repair is notably limited. Mesenchymal stem cells-derived extracellular vesicles (MSCs-EVs) play a pivotal role in intercellular communication, presenting promising potential not only as early diagnostic biomarkers in OA but also as efficacious therapeutic strategy. MSCs-EVs were confirmed to play a therapeutic role in the pathological process of cartilage injury mentioned above. This paper comprehensively provides the functions and mechanisms of MSCs-EVs in cartilage repair.

Advances in understanding effects of miRNAs on apoptosis, autophagy, and pyroptosis in knee osteoarthritis

MicroRNAs (miRNAs) are a class of endogenous small non-coding RNAs. MicroRNAs-mediated signaling pathways play a critical regulatory role in inducing apoptosis, autophagy, and pyroptosis in developing knee osteoarthritis (KOA). Given this, we searched databases, such as PubMed, using keywords including "miRNA," "knee osteoarthritis," "apoptosis," "autophagy," "pyroptosis", and their combinations. Through an extensive literature review, we conclude that miRNAs can be modulated through various signaling pathways, such as Wnt/β-catenin, TGF-β, PI3K/AKT/mTOR, and NLRP3/Caspase-1, to regulate apoptosis, autophagy, and pyroptosis in KOA. Furthermore, we note that P2X7R and HMGB1 may be crucial regulatory molecules involved in the interconnected regulation of apoptosis, autophagy, and pyroptosis in KOA. Additionally, we describe that miR-140-5p and miR-107 can modulate the advancement of KOA chondrocytes by targeting distinct molecules involved in apoptosis, autophagy, and pyroptosis, respectively. Therefore, we conclude that miRNAs may be potential biomarkers and therapeutic targets for the early prediction, diagnosis, and effective therapeutic approaches of KOA.

Therapeutic potential in rheumatic diseases of extracellular vesicles derived from mesenchymal stromal cells

The incidence of rheumatic diseases such as rheumatoid arthritis and osteoarthritis and injuries to articular cartilage that lead to osteochondral defects is predicted to rise as a result of population ageing and the increase in high-intensity physical activities among young and middle-aged people. Current treatments focus on the management of pain and joint functionality to improve the patient's quality of life, but curative strategies are greatly desired. In the past two decades, the therapeutic value of mesenchymal stromal cells (MSCs) has been evaluated because of their regenerative potential, which is mainly attributed to the secretion of paracrine factors. Many of these factors are enclosed in extracellular vesicles (EVs) that reproduce the main functions of parental cells. MSC-derived EVs have anti-inflammatory, anti-apoptotic as well as pro-regenerative activities. Research on EVs has gained considerable attention as they are a potential cell-free therapy with lower immunogenicity and easier management than whole cells. MSC-derived EVs can rescue the pathogenetic phenotypes of chondrocytes and exert a protective effect in animal models of rheumatic disease. To facilitate the therapeutic use of EVs, appropriate cell sources for the production of EVs with the desired biological effects in each disease should be identified. Production and isolation of EVs should be optimized, and pre-isolation and post-isolation modifications should be considered to maximize the disease-modifying potential of the EVs.

Mechanistic and therapeutic insights into the function of NLRP3 inflammasome in sterile arthritis

The NLRP3 inflammasome, which belongs to the pyrin domain containing 3 family of NOD-like receptors, has a significant impact on both the innate and adaptive immune responses. Regulating host immune function and protecting against microbial invasion and cell damage, the NLRP3 inflammasome plays a crucial role. By triggering caspase-1, it facilitates the development of the inflammatory cytokines IL-1β and IL-18, and triggers cell pyroptosis, resulting in cell lysis and demise. Common sterile arthritis includes osteoarthritis (OA), rheumatoid arthritis (RA) and gouty arthritis (GA), all of which manifest as bone destruction and synovial inflammation in a complex inflammatory state, placing a significant medical burden on the families of patients and government agencies. In the past few years, there has been a growing interest in investigating the impact of cell pyroptosis on arthritis development, particularly the widespread occurrence of pyroptosis mediated by the NLRP3 inflammasome. The NLRP3 inflammasome's biological properties are briefly described in this review, along with the presentation of the fundamental processes of pyroptosis resulting from its activation. Furthermore, we provide a summary of the advancements made in studying the NLRP3 inflammasome in various forms of arthritis and enumerate the intervention approaches that target the NLRP3-mediated pyroptosis, either directly or indirectly. These discoveries lay the groundwork for future investigations on medications for arthritis, offering fresh approaches for the clinical identification and treatment of this condition.

METTL3 Regulates the m6A Modification of NEK7 to Inhibit the Formation of Osteoarthritis

OBJECTIVE

Osteoarthritis (OA) is a common degenerative joint disease. The occurrence of OA slowly destroys the soft tissue structure of the patient's joint. Severe cases could lead to disability. Current studies had shown that inhibition of chondrocytes pyroptosis could slow down the progression of OA. Our work aimed to explore the specific mechanisms and ways of regulating this process.

DESIGN

In this work, the level of N6-methyladenosine (m6A) in clinical tissues was detected by ribonucleic acid (RNA) m6A dot blot. qRT-PCR (quantitative real-time polymerase chain reaction) was used to detect the messenger RNA (mRNA) expression level of m6A modified enzyme in clinical tissues. MTT (3-(4,5)-dimethylthiahiazo(-z-y1)-3,5-di-phenytetrazoliumromid) and flow cytometry were used to detect the effect of sh-METTL3 (methyltransferase like 3) and NIMA-related kinase 7 (NEK7) transfection on chondrocytes pyroptosis in OA. Western blot was used to detect the protein expression levels of pyroptosis-related proteins. ELISA (enzyme-linked immunosorbent assay) was used to measure the protein concentration of inflammatory cytokines. The SRAMP online database was used to predict the m6A site of NEK7. HE staining was used to assess the progression of OA in mice.

RESULTS

The level of m6A in clinical samples of OA patients was higher, and METTL3 was significantly higher expressed in clinical samples of OA patients. We provided evidence that low expression of METTL3 inhibited chondrocytes pyroptosis. In addition, Rescue experiments and in vivo experiments had shown that METTL3 in combination with NEK7 inhibited the progression of OA by promoting chondrocytes pyroptosis.

CONCLUSIONS

METTL3 regulates m6A modification of NEK7 and inhibits OA progression.

Human umbilical cord mesenchymal stem cells-derived exosomes exert anti-inflammatory effects on osteoarthritis chondrocytes

Inflammation of chondrocytes plays a critical role in the occurrence and development of osteoarthritis (OA). Recent evidence indicated exosomes derived from mesenchymal stem cells (MSCs-Exos) exhibit excellent anti-inflammatory ability in many troublesome inflammatory diseases including OA. In the present study, we aimed to explore the role of human umbilical cord-derived MSCs-Exos (hUC-MSCs-Exos) in treating the inflammation of chondrocytes and its related mechanisms. Ultracentrifugation was applied to isolate hUC-MSCs-Exos from the culture supernatant of hUC-MSCs. Two OA-like in vitro inflammation models of human articular chondrocytes induced with interleukin 1β (IL-1β) and co-incubation with macrophage utilizing transwell cell culture inserts were both used to evaluate the anti-inflammatory effects of hUC-MSCs-Exos. The mRNA sequencing of chondrocytes after treatment and microRNA (miRNA) sequencing of hUC-MSCs-Exos were detected and analyzed for possible mechanism analysis. The results of the study confirmed that hUC-MSCs-Exos had a reversed effect of IL-1β on chondrocytes in the expression of collagen type II alpha 1 (COL2A1) and matrix metalloproteinase 13 (MMP13). The addition of hUC-MSCs-Exos to M1 macrophages in the upper chamber showed down-regulation of IL-1β and tumor necrosis factor α (TNF-α), up-regulation of IL-10 and arginase1 (ARG1), and reversed the gene and protein expression of COL2A1 and MMP13 of the chondrocytes seeded in the lower chamber. The results of this study confirmed the anti-inflammatory effects of hUC-MSCs-Exos in the human articular chondrocytes inflammation model. hUC-MSCs-Exos may be used as a potential cell-free treatment strategy for chondrocyte inflammation in 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.

microRNAs delivered by small extracellular vesicles in MSCs as an emerging tool for bone regeneration

Bone regeneration is a dynamic process that involves angiogenesis and the balance of osteogenesis and osteoclastogenesis. In bone tissue engineering, the transplantation of mesenchymal stem cells (MSCs) is a promising approach to restore bone homeostasis. MSCs, particularly their small extracellular vesicles (sEVs), exert therapeutic effects due to their paracrine capability. Increasing evidence indicates that microRNAs (miRNAs) delivered by sEVs from MSCs (MSCs-sEVs) can alter gene expression in recipient cells and enhance bone regeneration. As an ideal delivery vehicle of miRNAs, MSCs-sEVs combine the high bioavailability and stability of sEVs with osteogenic ability of miRNAs, which can effectively overcome the challenge of low delivery efficiency in miRNA therapy. In this review, we focus on the recent advancements in the use of miRNAs delivered by MSCs-sEVs for bone regeneration and disorders. Additionally, we summarize the changes in miRNA expression in osteogenic-related MSCs-sEVs under different microenvironments.

Therapeutic potential of Coptis chinensis for arthritis with underlying mechanisms

Arthritis is a common degenerative disease of joints, which has become a public health problem affecting human health, but its pathogenesis is complex and cannot be eradicated. Coptis chinensis (CC) has a variety of active ingredients, is a natural antibacterial and anti-inflammatory drug. In which, berberine is its main effective ingredient, and has good therapeutic effects on rheumatoid arthritis (RA), osteoarthritis (OA), gouty arthritis (GA). RA, OA and GA are the three most common types of arthritis, but the relevant pathogenesis is not clear. Therefore, molecular mechanism and prevention and treatment of arthritis are the key issues to be paid attention to in clinical practice. In general, berberine, palmatine, coptisine, jatrorrhizine, magnoflorine and jatrorrhizine hydrochloride in CC play the role in treating arthritis by regulating Wnt1/β-catenin and PI3K/AKT/mTOR signaling pathways. In this review, active ingredients, targets and mechanism of CC in the treatment of arthritis were expounded, and we have further explained the potential role of AHR, CAV1, CRP, CXCL2, IRF1, SPP1, and IL-17 signaling pathway in the treatment of arthritis, and to provide a new idea for the clinical treatment of arthritis by CC.

Epigenetic regulatory mechanism of ADAMTS12 expression in osteoarthritis

BACKGROUND

Osteoarthritis (OA) is a degenerative joint disease with lacking effective prevention targets. A disintegrin and metalloproteinase with thrombospondin motifs 12 (ADAMTS12) is a member of the ADAMTS family and is upregulated in OA pathologic tissues with no fully understood molecular mechanisms.

METHODS

The anterior cruciate ligament transection (ACL-T) method was used to establish rat OA models, and interleukin-1 beta (IL-1β) was administered to induce rat chondrocyte inflammation. Cartilage damage was analyzed via hematoxylin-eosin, Periodic Acid-Schiff, safranin O-fast green, Osteoarthritis Research Society International score, and micro-computed tomography assays. Chondrocyte apoptosis was detected by flow cytometry and TdT dUTP nick-end labeling. Signal transducer and activator of transcription 1 (STAT1), ADAMTS12, and methyltransferase-like 3 (METTL3) levels were detected by immunohistochemistry, quantitative polymerase chain reaction (qPCR), western blot, or immunofluorescence assay. The binding ability was confirmed by chromatin immunoprecipitation-qPCR, electromobility shift assay, dual-luciferase reporter, or RNA immunoprecipitation (RIP) assay. The methylation level of STAT1 was analyzed by MeRIP-qPCR assay. STAT1 stability was investigated by actinomycin D assay.

RESULTS

The STAT1 and ADAMTS12 expressions were significantly increased in the human and rat samples of cartilage injury, as well as in IL-1β-treated rat chondrocytes. STAT1 is bound to the promoter region of ADAMTS12 to activate its transcription. METTL3/ Insulin-like growth factor 2 mRNA-binding protein 2 (IGF2BP2) mediated N6-methyladenosine modification of STAT1 promoted STAT1 mRNA stability, resulting in increased expression. ADAMTS12 expression was reduced and the IL-1β-induced inflammatory chondrocyte injury was attenuated by silencing METTL3. Additionally, knocking down METTL3 in ACL-T-produced OA rats reduced ADAMTS12 expression in their cartilage tissues, thereby alleviating cartilage damage.

CONCLUSION

METTL3/IGF2BP2 axis increases STAT1 stability and expression to promote OA progression by up-regulating ADAMTS12 expression.

Bone-Targeted Exosomes: Strategies and Applications

As the global population ages, bone-related diseases have increasingly become a major social problem threatening human health. Exosomes, as natural cell products, have been used to treat bone-related diseases due to their superior biocompatibility, biological barrier penetration, and therapeutic effects. Moreover, the modified exosomes exhibit strong bone-targeting capabilities that may improve efficacy and avoid systemic side effects, demonstrating promising translational potential. However, a review of bone-targeted exosomes is still lacking. Thus, the recently developed exosomes for bone-targeting applications in this review are focused. The biogenesis and bone-targeting regulatory functions of exosomes, the constructive strategies of modified exosomes to improve bone-targeting, and their therapeutic effects for bone-related diseases are introduced. By summarizing developments and challenges in bone-targeted exosomes, It is striven to shed light on the selection of exosome constructive strategies for different bone diseases and highlight their translational potential for future clinical orthopedics.

A Bibliometric Analysis of Exosomes Therapy in the Treatment of Osteoarthritis from 2012 to 2022

Purpose

Osteoarthritis (OA) is a common clinical disease characterized by the destruction of articular cartilage, subchondral ossification, cystic degeneration and osteophyte formation. Recently, more and more scholars draw attention to exosomes in the field of OA, and exciting breakthroughs have been achieved in recent years. However, bibliometric analysis of the literature in this research field is lacking. Considering its potential in treatment of OA, this article aimed to analyze the research status and identify future hotspots of exosomes in osteoarthritis in recent 10 years by bibliometrics tools.

Methods

Relevant publications in this field from 2012 to 2022 was retrieved from the Web of Science core collection database (WOSSCC). And we used Vosviewers, CiteSpace, an online analysis platform and the R package "Bibliometrix" for bibliometric analysis.

Results

A total of 484 publications (including 319 articles and 165 reviews) from 51 countries, 720 institutions, were included in this study. IRCCS Ist Ortoped Galeazzi, Shanghai Jiao Tong University, and Sun Yat-sen University are the leading research institutions in this field. International Journal of Molecular Sciences contributed the largest number of articles, and Osteoarthritis and Cartilage is the most co-cited journal. Of the 2664 scholars who participated in the study, Ragni E, De Girolamo L, Orfei CP, and Colombini A had the largest number of articles. Zhang, SP is the most co-cited author. "Mesenchymal stem cell", "biomaterials", "Inflammation" and "regenerative medicine" are the keywords in the research.

Conclusion

This is the first bibliometric analysis of exosomes in osteoarthritis. We explored current research status in recent years and identified frontiers and hot spots in this research field. We highlight the significant roles of mesenchymal stem cell-derived exosomes (MSC-Exos) in the treatment of osteoarthritis, and identified exosomal biomaterials as frontier in this research domain, which can provide reference for the researchers who focus on this research field.

Macrophages-bone marrow mesenchymal stem cells crosstalk in bone healing

Bone healing is associated with many orthopedic conditions, including fractures and osteonecrosis, arthritis, metabolic bone disease, tumors and periprosthetic particle-associated osteolysis. How to effectively promote bone healing has become a keen topic for researchers. The role of macrophages and bone marrow mesenchymal stem cells (BMSCs) in bone healing has gradually come to light with the development of the concept of osteoimmunity. Their interaction regulates the balance between inflammation and regeneration, and when the inflammatory response is over-excited, attenuated, or disturbed, it results in the failure of bone healing. Therefore, an in-depth understanding of the function of macrophages and bone marrow mesenchymal stem cells in bone regeneration and the relationship between the two could provide new directions to promote bone healing. This paper reviews the role of macrophages and bone marrow mesenchymal stem cells in bone healing and the mechanism and significance of their interaction. Several new therapeutic ideas for regulating the inflammatory response in bone healing by targeting macrophages and bone marrow mesenchymal stem cells crosstalk are also discussed.

Small extracellular vesicles: a novel drug delivery system for neurodegenerative disorders

Neurodegenerative diseases (NDs) have a slow onset and are usually detected late during disease. NDs are often difficult to cure due to the presence of the blood-brain barrier (BBB), which makes it difficult to find effective treatments and drugs, causing great stress and financial burden to families and society. Currently, small extracellular vesicles (sEVs) are the most promising drug delivery systems (DDSs) for targeted delivery of molecules to specific sites in the brain as a therapeutic vehicle due to their low toxicity, low immunogenicity, high stability, high delivery efficiency, high biocompatibility and trans-BBB functionality. Here, we review the therapeutic application of sEVs in several NDs, including Alzheimer's disease, Parkinson's disease, and Huntington's disease, discuss the current barriers associated with sEVs and brain-targeted DDS, and suggest future research directions.

Silencing of IRF7 ameliorates osteoarthritis by inhibiting chondrocyte pyroptosis via targeting FGF21

Osteoarthritis (OA) is the most common joint disease which can lead to serious disability. Interferon regulatory factor 7 (IRF7) is a member of the interferon regulatory factor family. This study aimed to explore the function and potential mechanism of IRF7 in OA. Our results found that IRF7 was increased in LPS-stimulated C28/I2 chondrocytes and in OA mice established with medial menisco-tibial ligament (MMTL) transection. IRF7 silencing enhanced cell viability, reduced IL-18 and IL-1β levels and suppressed cell apoptosis. IRF7 knockdown decreased ROS and LDH levels, and inhibited pyroptosis in LPS-treated chondrocytes. IRF7 negatively regulated FGF21 expression. FGF21 overexpression alleviated pyroptosis in LPS-stimulated chondrocytes. Knockdown of IRF7 improved OA injury in mice. In conclusion, our study demonstrates that silencing of IRF7 alleviates OA by inhibiting chondrocyte pyroptosis via upregulation of FGF21.

Exercise induced meteorin-like protects chondrocytes against inflammation and pyroptosis in osteoarthritis by inhibiting PI3K/Akt/NF-κB and NLRP3/caspase-1/GSDMD signaling

The production of metrnl, a novel adipomyokine, is induced upon exercise in adipose tissue and skeletal muscle. In this study, we investigated the anti-inflammatory and antipyroptotic effects of exercise-induced metrnl producted in rats in vitro and in vivo. Forty Sprague-Dawley rats were divided randomly into five groups: control (CG), osteoarthritis (OA) with sedentary lifestyle (OAG), OA with low intensity exercise (OAL), OA with moderate intensity exercise (OAM), and OA with high intensity exercise (OAH). The correlation between the level of metrnl and OA degree was detected using ELISA, X-ray imaging, histology, and immunohistochemistry in vivo. Primary chondrocytes were preincubated with recombinant metrnl before interleukin-1β administration to verify the anti-inflammatory and antipyroptotic effects of metrnl. Western blotting and quantitative reverse transcription (qRT)-PCR were used to evaluate the differences in protein and mRNA expression between groups, respectively. Reactive oxygen species (ROS) assay, immunofluorescence, transmission electron microscopy (TEM), and flow cytometry were used to evaluate morphological changes and pyroptosis in chondrocytes. In the moderate-intensity treadmill exercise group, the severity of OA showed maximum relief and the metrnl levels had the most significant increase. Metrnl exerted its anti-inflammatory effect through the suppression of the PI3K/Akt/NF-κB pathway in IL-1β-induced OA chondrocytes, which was accompanied with the recovery of collagen II expression and the attenuation of MMP13 and ADAMTS5. Moreover, metrnl ameliorated chondrocyte pyroptosis by inhibiting the activation of the nod-like receptor protein-3/caspase-1/gasdermin D cascade. In conclusion, moderate-intensity exercise improves inflammation and pyroptosis by increasing metrnl release, which inhibits the PI3K/Akt/NF-κB and further NLRP3/caspase-1/GSDMD signaling pathways.

Exosomes treating osteoarthritis: hope with challenge

Osteoarthritis (OA) has been proven as the second primary cause of pain and disability in the elderly population, impact patients both physically and mentally, as well as imposing a heavy burden on the global healthcare system. Current treatment methods, whether conservative or surgical, that aim at relieving symptoms can not delay or reverse the degenerative process in the structure. Scientists and clinicians are facing a revolution in OA treatment strategies. The emergence of exosomes brings hope for OA treatment based on pathology, which is attributed to its full potential in protecting chondrocytes from excessive death, alleviating inflammation, maintaining cartilage matrix metabolism, and regulating angiogenesis and subchondral bone remodeling. Therefore, we summarized the recent studies of exosomes in OA, aiming to comprehensively understand the functions and mechanisms of exosomes in OA treatment, which may provide direction and theoretical support for formulating therapeutic strategies in the future.

Pyroptosis in bone loss

Pyroptosis could be responsible for the bone loss from bone metabolic diseases, leading to the negative impact on people's health and life. It has been shown that osteoclasts, osteoblasts, macrophages, chondrocytes, periodontal and gingival cells may be involved in bone loss linked with pyroptosis. So far, the involved mechanisms have not been fully elucidated. In this review, we introduced the related cells involved in the pyroptosis associated with bone loss and summarized the role of these cells in the bone metabolism during the process of pyroptosis. We also discuss the clinical potential of targeting mechanisms in the osteoclasts, osteoblasts, macrophages, chondrocytes, periodontal and gingival cells touched upon pyroptosis to treat bone loss from bone metabolic diseases as well as the challenges of avoiding potential side effects and producing efficient treatment methods.

Advances in the Study of Exosomes as Drug Delivery Systems for Bone-Related Diseases

Bone-related diseases are major problems and heavy burdens faced by modern society. Current clinical approaches for the treatment of these pathological conditions often lead to complications and have limited therapeutic efficacy. In this context, the development of nanotherapeutic platforms, such as extracellular vesicles, can improve the relevant therapeutic effects. In particular, exosomes are nano-sized, lipid bilayer extracellular vesicles secreted by many cells in mammals. Due to their innate capacity to transport materials-including proteins, lipids, and genes-among cells, as well as their innate attraction to target cells, they are considered to be a crucial medium for cell communication and are involved in a number of biological processes. Exosomes have been used as drug delivery vehicles in recent bone tissue engineering studies, in order to regulate bone homeostasis. However, the precise workings of the exosome regulatory network in maintaining bone homeostasis and its potential for treating bone injury remain unclear. To provide a fresh perspective for the study of exosomes in drug delivery and bone-related diseases, in this paper, we review recent studies on the roles of exosomes for drug delivery in bone homeostasis and bone-related diseases, as well as the composition and characteristics of exosomes and their regulatory roles in bone homeostasis and bone-related diseases, aiming to provide new ideas for the therapeutic application of exosomes in the treatment of bone-related diseases.

The protective activity of natural flavonoids against osteoarthritis by targeting NF-κB signaling pathway

Osteoarthritis (OA) is a typical joint disease associated with chronic inflammation. The nuclear factor-kappaB (NF-κB) pathway plays an important role in inflammatory activity and inhibiting NF-κB-mediated inflammation can be a potential strategy for treating OA. Flavonoids are a class of naturally occurring polyphenols with anti-inflammatory properties. Structurally, natural flavonoids can be divided into several sub-groups, including flavonols, flavones, flavanols/catechins, flavanones, anthocyanins, and isoflavones. Increasing evidence demonstrates that natural flavonoids exhibit protective activity against the pathological changes of OA by inhibiting the NF-κB signaling pathway. Potentially, natural flavonoids may suppress NF-κB signaling-mediated inflammatory responses, ECM degradation, and chondrocyte apoptosis. The different biological actions of natural flavonoids against the NF-κB signaling pathway in OA chondrocytes might be associated with the differentially substituted groups on the structures. In this review, the efficacy and action mechanism of natural flavonoids against the development of OA are discussed by targeting the NF-κB signaling pathway. Potentially, flavonoids could become useful inhibitors of the NF-κB signaling pathway for the therapeutic management of OA.

The regulatory role and therapeutic application of pyroptosis in musculoskeletal diseases

Pyroptosis is a controlled form of inflammatory cell death characterized by inflammasome activation, pore formation, and cell lysis. According to different caspases, pyroptosis can be divided into canonical, non-canonical, and other pathways. The role of pyroptosis in disease development has been paid more attention in recent years. The trigger factors of pyroptosis are often related to oxidative stress and proinflammatory substances, which coincide with the pathological mechanism of some diseases. Pyroptosis directly leads to cell lysis and death, and the release of cytosolic components and proinflammatory cytokines affects cell activity and amplifies the inflammatory response. All the above are involved in a series of basic pathological processes, such as matrix degradation, fibrosis, and angiogenesis. Since these pathological changes are also common in musculoskeletal diseases (MSDs), emerging studies have focused on the correlations between pyroptosis and MSDs in recent years. In this review, we first summarized the molecular mechanism of pyroptosis and extensively discussed the differences and crosstalk between pyroptosis, apoptosis, and necrosis. Next, we elaborated on the role of pyroptosis in some MSDs, including osteoarthritis, rheumatoid arthritis, osteoporosis, gout arthritis, ankylosing spondylitis, intervertebral disc degeneration, and several muscle disorders. The regulation of pyroptosis could offer potential therapeutic targets in MSDs treatment. Herein, the existing drugs and therapeutic strategies that directly or indirectly target pyroptosis pathway components have been discussed in order to shed light on the novel treatment for MSDs.

MicroRNAs and long non-coding RNAs in cartilage homeostasis and osteoarthritis

During the last decade, osteoarthritis (OA) has become one of the most prevalent musculoskeletal diseases worldwide. OA is characterized by progressive loss of articular cartilage, abnormal remodeling of subchondral bone, hyperplasia of synovial cells, and growth of osteophytes, which lead to chronic pain and disability. The pathological mechanisms underlying OA initiation and progression are still poorly understood. Non-coding RNAs (ncRNAs) constitute a large portion of the transcriptome that do not encode proteins but function in numerous biological processes. Cumulating evidence has revealed a strong association between the changes in expression levels of ncRNA and the disease progression of OA. Moreover, loss- and gain-of-function studies utilizing transgenic animal models have demonstrated that ncRNAs exert vital functions in regulating cartilage homeostasis, degeneration, and regeneration, and changes in ncRNA expression can promote or decelerate the progression of OA through distinct molecular mechanisms. Recent studies highlighted the potential of ncRNAs to serve as diagnostic biomarkers, prognostic indicators, and therapeutic targets for OA. MiRNAs and lncRNAs are two major classes of ncRNAs that have been the most widely studied in cartilage tissues. In this review, we focused on miRNAs and lncRNAs and provided a comprehensive understanding of their functional roles as well as molecular mechanisms in cartilage homeostasis and OA pathogenesis.

Nanodevices for deep cartilage penetration

Osteoarthritis (OA) is a degenerative joint disease and is the main cause of chronic pain and functional disability in adults. Articular cartilage is a hydrated soft tissue that is composed of normally quiescent chondrocytes at a low density, a dense network of collagen fibrils with a pore size of 60-200 nm, and aggrecan proteoglycans with high-density negative charge. Although certain drugs, nucleic acids, and proteins have the potential to slow the progression of OA and restore the joints, these treatments have not been clinically applied owing to the lack of an effective delivery system capable of breaking through the cartilage barrier. Recently, the development of nanotechnology for delivery systems renders new ideas and treatment methods viable in overcoming the limited penetration. In this review, we focus on current research on such applications of nanotechnology, including exosomes, protein-based cationic nanocarriers, cationic liposomes/solid lipid nanoparticles, amino acid-based nanocarriers, polyamide derivatives-based nanocarriers, manganese dioxide, and carbon nanotubes. Exosomes are the smallest known nanoscale extracellular vesicles, and they can quickly deliver nucleic acids or proteins to the required depth. Through electrostatic interactions, nanocarriers with appropriate balance in cationic property and particle size have a strong ability to penetrate cartilage. Although substantial preclinical evidence has been obtained, further optimization is necessary for clinical transformation. STATEMENT OF SIGNIFICANCE: The dense cartilage matrix with high-negative charge was associated with reduced therapeutic effect in osteoarthritis patients with deep pathological changes. However, a systematic review in nanodevices for deep cartilage penetration is still lacking. Current approaches to assure penetration of nanosystems into the depth of cartilage were reviewed, including nanoscale extracellular vesicles from different cell lines and nanocarriers with appropriate balance in cationic property and size particle. Moreover, nanodevices entering clinical trials and further optimization were also discussed, providing important guiding significance to future research.

Triptolide improves chondrocyte proliferation and secretion via down-regulation of miR-221 in synovial cell exosomes

BACKGROUND

Rheumatoid arthritis (RA), the most common type of inflammatory arthritis, can cause bone damage and disability. Triptolide, a prominent treatment for RA, has satisfactory anti-inflammatory effects. However, the mechanism of action of triptolide in RA remains unknown.

PURPOSE

This study aimed to explore the molecular mechanisms underlying triptolide-mediated improvements in RA and identify the miRNA pathway responsible for these effects.

METHODS

We identified various dysregulated miRNAs associated with RA by mining previously described microarray data and verified and screened these candidates using RT-qPCR. Hematoxylin-eosin staining was then applied to identify pathological changes in the affected joints, and cell counting kit-8 analysis and flow cytometry were employed to examine cell proliferation and apoptosis, respectively. Extracted exosomes were verified using transmission electron microscopy.

RESULTS

Our results revealed that the legs of rats with collagen-induced arthritis presented with obvious swelling and bone damage, a high degree of inflammatory cell infiltration into the synovium, and structural changes to the cartilage. Data mining identified 39 dysregulated miRNAs in these tissues, and RT-qPCR further refined these observations to highlight miR-221 as a potential RA biomarker. Subsequent evaluations revealed that fibroblast-like synovial (FLS) cells secrete Exs carrying dysregulated miR-221 in vitro. These Exs mediate miR-221 levels, inflammation, and TLR4/MyD88 signaling via their fusion with chondrocytes, leading to changes in chondrocyte growth and metabolic factor levels. Additionally, the addition of triptolide impaired miR-221 expression, cell proliferation, inflammatory factors, and the protein levels of TLR4/MyD88 in RA-FLS and promoted the apoptosis of FLS. The therapeutic effect of triptolide on miR-221 Exs was reversed by miR-221 inhibitor in both normal and RA FLS.

CONCLUSION

Our research shows that effective treatment with triptolide is mediated by its regulation of growth and secretory functions of chondrocytes via the inhibition of miR-221 secretion by FLS, providing a new target and natural medicinal candidate for future RA treatments.

Circular RNA MELK Promotes Chondrocyte Apoptosis and Inhibits Autophagy in Osteoarthritis by Regulating MYD88/NF-κB Signaling Axis through MicroRNA-497-5p

Osteoarthritis (OA) is a rheumatic disease and its pathogenesis involves the dysregulation of noncoding RNAs. Therefore, the regulatory mechanism of circular RNA MELK (circMELK) was specified in this work. OA human cartilage tissue was collected, and circMELK, miR-497-5p, and myeloid differentiation factor 88 (MYD88) expression were examined. Human chondrocytes were stimulated with interleukin- (IL-) 1β and interfered with vectors altering circMELK, miR-497-5p, and MyD88 expression to observe their effects on cell viability, cell cycle and apoptosis, autophagy, and inflammation. The binding relationship between RNAs was verified. The data presented that OA cartilage tissues presented raised circMELK and MYD88 and inhibited miR-497-5p expression. IL-1β suppressed cell viability, prevented cell cycle, and induced apoptosis, autophagy, and inflammation of chondrocytes. Functionally, IL-1β-induced changes of chondrocytes could be attenuated by suppressing circMELK or overexpressing miR-497-5p. circMELK acted as a sponge of miR-497-5p while miR-497-5p was a regulator of MYD88. MYD88 restricted the effect of overexpressing miR-497-5p on IL-1β-stimulated chondrocytes. MYD88 triggered nuclear factor-kappaB (NF-κB) pathway activation. Shortly, CircMELK promotes chondrocyte apoptosis and inhibits autophagy in OA by regulating MYD88/NF-κB signaling axis through miR-497-5p. Our study proposes a new molecular mechanism for the development of OA.

Engineering of MSC-Derived Exosomes: A Promising Cell-Free Therapy for Osteoarthritis

Osteoarthritis (OA) is characterized by progressive cartilage degeneration with increasing prevalence and unsatisfactory treatment efficacy. Exosomes derived from mesenchymal stem cells play an important role in alleviating OA by promoting cartilage regeneration, inhibiting synovial inflammation and mediating subchondral bone remodeling without the risk of immune rejection and tumorigenesis. However, low yield, weak activity, inefficient targeting ability and unpredictable side effects of natural exosomes have limited their clinical application. At present, various approaches have been applied in exosome engineering to regulate their production and function, such as pretreatment of parental cells, drug loading, genetic engineering and surface modification. Biomaterials have also been proved to facilitate efficient delivery of exosomes and enhance treatment effectiveness. Here, we summarize the current understanding of the biogenesis, isolation and characterization of natural exosomes, and focus on the large-scale production and preparation of engineered exosomes, as well as their therapeutic potential in OA, thus providing novel insights into exploring advanced MSC-derived exosome-based cell-free therapy for the treatment of OA.

Exosomes in osteoarthritis: Updated insights on pathogenesis, diagnosis, and treatment

Osteoarthritis (OA) has remained a prevalent public health problem worldwide over the past decades. OA is a global challenge because its specific pathogenesis is unclear, and no effective disease-modifying drugs are currently available. Exosomes are small and single-membrane vesicles secreted via the formation of endocytic vesicles and multivesicular bodies (MVBs), which are eventually released when MVBs fuse with the plasma membrane. Exosomes contain various integral surface proteins derived from cells, intercellular proteins, DNAs, RNAs, amino acids, and metabolites. By transferring complex constituents and promoting macrophages to generate chemokines and proinflammatory cytokines, exosomes function in pathophysiological processes in OA, including local inflammation, cartilage calcification and degradation of osteoarthritic joints. Exosomes are also detected in synovial fluid and plasma, and their levels continuously change with OA progression. Thus, exosomes, specifically exosomal miRNAs and lncRNAs, potentially represent multicomponent diagnostic biomarkers for OA. Exosomes derived from various types of mesenchymal stem cells and other cell or tissue types affect angiogenesis, inflammation, and bone remodeling. These exosomes exhibit promising capabilities to restore OA cartilage, attenuate inflammation, and balance cartilage matrix formation and degradation, thus demonstrating therapeutic potential in OA. In combination with biocompatible and highly adhesive materials, such as hydrogels and cryogels, exosomes may facilitate cartilage tissue engineering therapies for OA. Based on numerous recent studies, we summarized the latent mechanisms and clinical value of exosomes in OA in this review.

MiR-146a alleviates lung injury caused by RSV infection in young rats by targeting TRAF-6 and regulating JNK/ERKMAPK signaling pathways

Respiratory syncytial virus (RSV) is a major cause of acute lower respiratory tract infection in infants and children. The present study aimed to investigate the effects of miR-146a on RSV replication and the related mechanisms. Material and methods: We pretreated A549 and HEp-2 cells and young rats with miR-146a mimic before infection with RSV. The expressions of miR-146a and RSV-F mRNA in cells and lung tissues were detected by RT-qPCR, and production of IL-1β, IL-6, IL-18, and TNF-α in bronchial alveolar lavage fluid (BALF) were determined by ELISA. The expression level of TRAF-6 and activation of the JNK/ERK/MAPK/NF-κB signaling pathway was detected by Western blotting. Results: RSV infection significantly reduced miR-146a levels in both A549 and HEp-2 cells and rat lung tissues. RSV infection resulted in accelerated growth, increased release of inflammatory cytokines, increased expression of TRAF-6, and activation of the JNK pathway in cells, and the lung inflammatory infiltration and the pathological score increased in rats. Overexpression of miR-146a targeted down-regulation of TRAF-6 expression and JNK/ERK/MAPK/NF-κB pathway induced by RSV infection, reduced the production of inflammatory cytokines IL-1β, IL-6 and TNF-α, and alleviate lung injury in young rats. We got similar results in both A549 and HEp-2 cell experiments. Conclusion: MiR-146a alleviates lung injury caused by RSV infection in young rats by targeting TRAF-6 and regulating JNK/ERK/MAPK signaling pathways.

Chloride Channel and Inflammation-Mediated Pathogenesis of Osteoarthritis

Articular cartilage allows the human body to buffer and absorb stress during normal exercise. It is mainly composed of cartilage cells and the extracellular matrix and is surrounded by the extracellular microenvironment formed by synovial fluid and various factors in it. Studies have shown that chondrocytes are the metabolic center of articular cartilage. Under physiological conditions, the extracellular matrix is in a dynamic balance of anabolism and catabolism, and various factors and physical and chemical conditions in the extracellular microenvironment are also in a steady state. This homeostasis depends on the normal function of proteins represented by various ion channels on chondrocytes. In mammalian chondrocyte species, ion channels are mainly divided into two categories: cation channels and anion channels. Anion channels such as chloride channels have become hot research topics in recent years. These channels play an extremely important role in various physiological processes. Recently, a growing body of evidence has shown that many pathological processes, abnormal concentration of mechanical stress and chloride channel dysfunction in articular cartilage lead to microenvironment disorders, matrix and bone metabolism imbalances, which cause partial aseptic inflammation. These pathological processes initiate extracellular matrix degradation, abnormal chondrocyte death, hyperplasia of inflammatory synovium and bony. Osteoarthritis (OA) is a common clinical disease in orthopedics. Its typical manifestations are joint inflammation and pain caused by articular cartilage degeneration, but its pathogenesis has not been fully elucidated. Focusing on the physiological functions and pathological changes of chloride channels and pathophysiology of aseptic inflammation furthers the understanding of OA pathogenesis and provides possible targets for subsequent medication development.