Roles of extracellular vesicles in rheumatoid arthritis: A bibliometric analysis

Abstract

Purpose:

Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by synovial inflammation and joint destruction, imposing a significant burden on society. Recent research highlights the critical role of extracellular vesicles (EVs) in RA, but no bibliometric analysis has comprehensively examined this field. This study aims to fill that gap.

Methods:

Relevant publications from the past 2 decades were retrieved from the Web of Science Core Collection database. Bibliometric analyses were conducted using VOSviewer and the R package “Bibliometrix” to evaluate annual output, collaboration networks, research hotspots, current status, and developmental trends in this field.

Results:

A total of 512 publications (311 articles and 201 reviews) from 922 institutions across 59 countries were analyzed. China led in publication volume and citations. Southwest Medical University was the top institution. Frontiers in Immunology published the highest number of publications (35) and received the most citations (1042). The most productive author was LIU Y (13 papers), and the most cited was GAY S (141 citations). Keyword and paper bibliometric analyses revealed revealed 2 major focuses: the role of EVs in RA pathogenesis and therapeutic strategies. High-frequency keywords such as “dendritic cells,” “T-cells,” and “microRNAs” highlight the involvement of immune cell-derived EVs in RA pathogenesis. While terms like “stem cells” and “mesenchymal stem cells” suggest growing interest in their immunomodulatory potential.

Conclusion:

This study represents the first bibliometric analysis of the relationship between RA and EVs. By objectively summarizing the current literature, this work provides insights into the roles of EVs in RA and serves as a valuable reference for researchers interested in this field.

1. Introduction

Rheumatoid arthritis (RA) is a chronic, systemic autoimmune disease characterized by synovial inflammation, cartilage and bone destruction, and potential systemic complications, imposing a significant societal burden.^[1]

The etiology of RA is multifactorial, involving a complex interplay of genetic and environmental factors.^[2] The strongest genetic predisposition is conferred by certain HLA-DRB1 alleles, notably those containing the “shared epitope” motif. In particular, HLA-DRB1*04 variants significantly increase RA susceptibility.^[3] Environmental risk factors, such as smoking and infections, enhance the immunogenicity of self-antigens through mechanisms like protein citrullination. Smoking not only doubles the risk of developing RA but also synergizes with HLA-DRB1 risk alleles, greatly amplifying the likelihood of seropositive RA (e.g., anti-citrullinated protein antibody positive disease).^[4–6] Microbial exposures have also been implicated in RA pathogenesis. For example, Porphyromonas gingivalis – a periodontal bacterium – and other infectious agents can induce protein citrullination and break immune tolerance, and antibodies to P gingivalis are often detected in RA patients.^[7] Although the underlying immunopathology (involving autoantibodies, T-cell and B-cell dysregulation, and cytokine networks) is complex,^[8] the above factors are thought to initiate and drive the autoimmune process in RA in a logical sequence from risk exposure to disease onset.

RA is a global disease, but there are notable regional differences in its epidemiology and research focus. For instance, the prevalence of RA in China (around 0.2–0.4% in adults) has historically been reported to be lower than that in Western countries (~0.5 to 1%).^[9] Nevertheless, due to China’s large population, the absolute number of RA patients is high, and RA remains a significant health burden in Asia. In recent decades, international research efforts on RA have intensified across all continents, with growing contributions from Asia (particularly China) complementing the extensive literature from Europe and North America. Regional variations in research priorities have also emerged; for example, Chinese researchers have explored integrated treatment approaches and unique environmental risk factors, alongside the immunological and therapeutic investigations more typical of Western research. Such a global perspective is essential, as insights from different populations and settings can collectively advance understanding of RA.

Current treatment strategies for RA include nonsteroidal anti-inflammatory drugs, conventional and biological disease-modifying antirheumatic drugs, and small-molecule targeted therapies such as Janus kinase (JAK) inhibitors.^[10] While these therapies provide some relief from clinical symptoms in RA patients, their limitations remain significant. First, a sizeable proportion of patients fails to achieve adequate clinical improvement. Second, most therapies primarily alleviate symptoms by suppressing immune responses but fail to effectively address or reverse the underlying pathophysiological processes of RA. Consequently, they cannot halt disease progression or achieve a definitive cure. Moreover, prolonged use of these drugs poses substantial risks of severe side effects. Therefore, it is crucial to explore novel pathological mechanisms and therapeutic targets at the molecular and cellular levels to enable the development of more effective strategies for precision treatment of RA.

In parallel with these developments, extracellular vehicles (EVs) have gained prominence in rheumatology research, including RA. EVs are membrane-bound particles released by cells into bodily fluids, ranging from nano-sized exosomes to larger microvesicles, and carrying diverse cargo (proteins, lipids, mRNA, microRNA, etc) that mediates intercellular communication.^[11] In the context of RA, EVs have been identified as important mediators and potential novel biomarkers and therapeutics.^[11] First, EVs contribute to RA pathogenesis: they can modulate innate and adaptive immune responses in the synovium, transferring pro-inflammatory factors and genetic material between cells and thereby exacerbating synovial inflammation and joint damage. Second, EVs have shown promise in diagnosis: RA patients demonstrate distinct EV profiles (for example, specific microRNAs, long noncoding RNAs and protein markers carried by EVs) that differ from healthy individuals, suggesting that EV-associated molecules could serve as sensitive biomarkers for early detection or disease activity monitoring.^[12] Third, EVs are being explored for therapeutic applications in RA.^[13] Research has indicated that EVs can be engineered or harnessed for treatment – for instance, mesenchymal stem cell-derived exosomes can exert anti-inflammatory effects and aid in tissue repair.^[14] Therapeutic agents (such as anti-inflammatory drugs or even nucleic acids) can be loaded into EVs for targeted delivery to inflamed joints.^[15] Thus, EVs represent a threefold opportunity in RA research: understanding disease mechanisms, improving diagnosis, and developing innovative treatments.

Given the burgeoning interest in EVs, the scientific literature on EVs in RA has expanded rapidly in recent years. An increasing number of studies have investigated EV biology in RA, reflecting a recognition of their important role in disease and their potential clinical utility. However, despite this rapid growth, there is a lack of systematic analysis of the knowledge landscape in this niche. In contrast to other subfields of RA research, no comprehensive bibliometric study has yet examined the evolution, hotspots, and collaborations in the literature on EVs and RA.^[16] To address this gap, the present study aims to conduct a bibliometric analysis of global research on EVs in RA. By quantitatively evaluating publication trends over time, geographic distribution of research output, core journals and authors, and frequently cited topics, we seek to characterize the development of this research area. The findings of this study will not only delineate the current state of EV-related RA research but also highlight emerging themes and inform future directions for researchers and clinicians in the field.

2. Materials and methods

2.1. Search strategy

We conducted a comprehensive literature search in the Web of Science Core Collection (WOSCC) database (https://www.webofscience.com/wos/WOSCC/basic-search). Preliminary exploration revealed that research in this field prior to 2004 was minimal (n < 10). To better analyze the current research landscape and identify trends, we restricted the publication period for this study to January 1, 2004, through October 1, 2024. The search query was constructed as follows: Topic = “RA” AND Topic= (“exosome*” OR “exosomes” OR “exosomal” OR “extracellular vesicle” OR “EVs” OR “extracellular particle” OR “extracellular particles” OR “microvesicle” OR “microvesicles” OR “Shedding Microvesicle” OR “Shedding Microvesicles” OR “Secretory Vesicle” OR “Secretory Vesicles” OR “Cell-Derived Microparticle” OR “Cell-Derived Microparticles”). We limited the document types to articles and reviews and restricted the language to English. This search yielded a total of 512 results. The flowchart of the screening process is shown in Figure 1.

Figure 1.

Flowchart of literature identification and analysis process. TS = Topic, WOS = Web of Science.

2.2. Data analysis

To systematically analyze the bibliometric characteristics of the research field, this study employed 2 tools, Bibliometrix and VOSviewer, to conduct a comprehensive analysis ranging from data statistics to network visualization. Bibliometrix, an R-based bibliometric analysis package, offers robust capabilities for data extraction, statistical analysis, and visualization.^[17] Using this tool, we generated various analytical charts, including trends in annual publication output (Fig. 2), the geographic distribution of countries (Fig. 3A), publication output of the top 14 institutions (Fig. 4B), publication output of the top 17 journals (Fig. 5B), annual publication output of the top 10 authors (Fig. 6B), and thematic trend analysis (Fig. 7B).

Figure 2.

Annual outputs of publications regarding EVs in RA field. EVs = extracellular vesicles, RA = rheumatoid arthritis.

Figure 3.

(A) The geographical network map. (B) The overlay visualization map of country co-authorship analysis conducted by VOSviewer.

Figure 4.

(A) The visualization of institutions cooperation networks based on VOSviewer. (B) Top 14 institutions’ production over time.

Figure 5.

(A) The visualization of journals cooperation networks. (B) Network visualization of co-cited journals based on VOSviewer. (C) Top 16 journals’ production over time.

Figure 6.

The visualization of authors cooperation networks based on VOSviewer (A) and Top 10 authors’ production over time (B).

Figure 7.

(A) Keywords co-occurrence network based on VOSviewer and (B) Trend topic analysis based on R package “Bibliometrix”.

VOSviewer is another widely used open-source tool designed for constructing and visualizing bibliometric networks, excelling particularly in collaboration networks and co-occurrence analysis.^[18] Using VOSviewer, we constructed several visualizations, including the international collaboration network (Fig. 3B), institutional collaboration network (Fig. 4A), journal collaboration and co-citation networks (Fig. 5A, B), author collaboration network (Fig. 6A), and keyword co-occurrence network (Fig. 7A). These network maps provide intuitive insights into collaboration patterns, knowledge dissemination pathways, and associations among research hotspots, complementing the structural information that statistical analyses alone cannot fully capture.

Since the analytical goal was descriptive and explorative rather than inferential, no statistical hypothesis tests were conducted.

3. Results

3.1. Annual publication trends

Given the steady increase in publication volume over the years, the study period can be divided into 3 phases: Phase I (2005–2014), Phase II (2015–2019), and Phase III (2020–2024). As shown in Figure 2, the number of publications during Phase I was relatively low, with an average of ~5.3 publications per year, representing the initial stage of research on RA and EVs. In Phase II, the number of publications began to increase, with an annual average of 23, showing a slight rise compared to Phase I. By Phase III, the publication volume surged significantly, with an annual average of 68.8 publications. This trend highlights the growing recognition among researchers of the critical role of EVs in RA.

3.2. Country and institutional analysis

A total of 922 institutions across 59 countries have contributed to this research field. As shown in the geographic network map (Fig. 3A), the top 10 contributors are distributed across Asia, Europe, and North America. According to Table 1, China (204 publications) and the United States (87 publications) are the leading contributors, accounting for 56.8% of the total global output. They are followed by the United Kingdom (32 publications, 6.25%), Italy (26 publications, 5.07%), and Iran (24 publications, 4.68%).

Table 1.

Top 10 countries and institutions on research of EVs in RA field.

Rank	Country	Articles	Citation	Rank	Institution	Counts
1	China	204	4722	1	Semmelweis University	34
2	USA	87	4118	2	Sichuan University	27
3	England	32	684	3	Southwest Medical University	26
4	Italy	26	749	4	Anhui Medical University	21
5	Iran	24	1065	5	Laval University	21
6	Spain	22	550	6	Yangzhou University	20
7	South Korea	22	1125	7	Shandong Second Medical University	19
8	Netherlands	21	559	8	Universite Paris Cite	19
9	France	19	1157	9	University of Eastern Finland	19
10	Canada	15	799	10	Utrecht University	19

EVs = extracellular vesicles, RA = rheumatoid arthritis.

China also recorded the highest cumulative citation frequency (4722), followed by the United States (4118), France (1157), and South Korea (1125). However, China’s average citation per publication (23.14) is relatively low, indicating a broad research scope but a need for a higher proportion of high-impact studies.

In Figure 3B, the international academic collaboration network is visualized using nodes and lines, where the size of the nodes represents the number of publications from each country, and the lines indicate the frequency of collaboration. The visualization reveals that China and the United States serve as central hubs for international collaboration, with particularly strong ties observed between the United Kingdom and the United States. Overall, the field demonstrates a thriving pattern of international cooperation, though there is still significant potential for further strengthening cross-regional collaborations.

We further utilized VOSviewer to visualize academic collaborations among the 922 institutions. As shown in Figure 4A, close collaborations are observed between Southwest Medical University and Sichuan University, as well as between Southern Medical University and Guangzhou Medical University. However, these collaborations are predominantly limited to domestic institutions, with relatively few instances of cross-border partnerships. This suggests that there is substantial room for growth in international institutional collaborations.

In terms of institutional rankings (Fig. 4B, Table 1), Semmelweis University leads with 34 publications, followed closely by Sichuan University and Southwest Medical University, with 27 and 26 publications, respectively, showing only slight differences among the top 3. Figure 4B also illustrates the publication growth trends among the top 14 institutions over recent years. University Paris Cité was one of the earliest entrants into this field, while Semmelweis University has demonstrated steady growth since 2007. Notably, Southwest Medical University has experienced a rapid surge in publication output since 2021, highlighting its potential for a swift rise in prominence within the field.

3.3. Journals and co-cited journals

We employed VOSviewer to visualize journals and their co-citation networks within this research field. The dataset comprised 258 journals, from which we selected 42 journals that had published at least 3 articles (Fig. 5A). In Figure 5A, the node size represents the publication volume of each journal, with larger nodes indicating higher numbers of published articles. Figure 5B illustrates the co-citation network, including 336 journals that had been cited at least 25 times.

Local citation refers to citations derived from the reference lists of articles within the dataset, reflecting a journal’s influence within a specific research domain. Total Link Strength (TLS), on the other hand, is a key metric in co-citation networks that quantifies the cumulative strength of co-citation relationships between a journal and others, highlighting its integration and significance within the knowledge network. Table 2 presents the top 10 journals with the highest local citation counts and their corresponding TLS values. Frontiers in Immunology ranks first with 1042 citations, followed by The Journal of Immunology (989 citations) and Arthritis & Rheumatism (839 citations), indicating that these journals have significantly contributed to the study of EVs in RA through high-quality publications.

Table 2.

Top 10 journals and co-cited journals for EVs in RA.

Ranks	Journals	Count	IF	Q	Co-cited journals	Citation	Total link strength
1	Frontiers in Immunology	35	5.7	Q1	Frontiers in Immunology	1042	1,21,223
2	International Journal of Molecular Sciences	21	4.8	Q1	Journal of Immunology	989	89,493
3	Arthritis Research & Therapy	15	4.4	Q1	Arthritis & Rheumatology (US)	839	75,372
4	International Immunopharmacology	15	4.9	Q1	Arthritis Research & Therapy	785	72,098
5	Cells	11	7.6	Q1	Annals of the Rheumatic Diseases	733	69,754
6	Arthritis and Rheumatism	7	11.4	Q1	PLOS ONE	706	88,413
7	Journal of Nanobiotechnology	7	10.6	Q1	International Journal of Molecular Sciences	652	93,034
8	Arthritis & Rheumatology	5	11.4	Q1	Stem Cell Research & Therapy	616	1,15,883
9	Autoimmunity Reviews	5	9.2	Q1	Scientific Reports (UK)	588	73,632
10	Heliyon	8	3.2	Q2	Blood	584	54,547

EVs = extracellular vesicles, RA = rheumatoid arthritis.

In the TLS rankings, the top 5 journals are Frontiers in Immunology (TLS = 1,21,223), Stem Cell Research & Therapy (TLS = 1,15,883), International Journal of Molecular Sciences (TLS = 93,034), The Journal of Immunology (TLS = 89,493), and PLOS ONE (TLS = 88,413). These high-TLS journals demonstrate significant academic influence within the citation network, serving as key connectors across multiple research areas and disciplines.

Figure 5C illustrates the annual publication trends of the top 17 journals from 2004 to 2024. Notably, the publication volume of Frontiers in Immunology has increased significantly since 2019, highlighting its sustained influence in this field. According to Table 2, the journals with the highest number of published articles include Frontiers in Immunology (35 articles, IF = 5.7), International Journal of Molecular Sciences (21 articles, IF = 5.6), Arthritis Research & Therapy (15 articles, IF = 4.4), and International Immunopharmacology (15 articles, IF = 4.8). It is noteworthy that 9 out of the top 10 journals belong to the journal citation reports Q1 category, reflecting their high academic quality and widespread recognition in the scientific community.

3.4. Authors and co-cited authors

In the field of research on RA and EVs, a total of 3294 researchers have contributed, with the top 10 contributors accounting for 90 publications, representing 17.5% of the total output (Table 3). Among them, LIU Y is the most prolific author, with 13 publications. The h-index, a widely recognized metric for assessing scholarly impact, considers both the quantity of publications and their citation impact, providing a balanced evaluation of research influence.^[16] As shown in Table 3, Liu Y and Nagy G have the highest h-indices, followed by other contributors such as Zhang Y.

Table 3.

Top10 authors and co-cited authors on research of RA-EVs field.

Rank	Authors	Counts	H-index	Co-cited authors	Citations	Total link strength
1	Liu Y	13	9	Gay S	147	2755
2	Zhang Y	12	8	Nagy G	118	3028
3	Nagy G	10	9	Jorgensen C	112	1655
4	Wang Y	10	7	Maumus M	110	2206
5	Li J	9	6	Noël D	105	2519
6	Li CH	8	7	Chen Z	98	1556
7	Buzás EI	7	7	Xia Y	93	1536
8	Gay S	7	7	Lu Y	86	1349
9	Kittel A	7	7	Wang HQ	79	1891
10	Norling LV	7	5	Yan FH	74	1562

EVs = extracellular vesicles, RA = rheumatoid arthritis.

Using VOSviewer, we visualized academic collaboration networks among authors (Fig. 6A). Close collaborations were observed between Liu Y, Li Chunhong, and Wang Yao, as well as between Gay S and Buzas EI Figure 6B presents the annual research output of the top 10 authors in the RA-EVs field, with lines indicating active years, circle sizes representing the number of publications, and color gradients reflecting annual citation counts. The analysis reveals that Gay S and Kittel A were highly active between 2007 and 2013, laying the foundation for this field, while impactful publications by Liu Y and Zhang Y have increased significantly since 2017.

A highly cited review by Liu Y provides an in-depth analysis of the role of EVs in the pathogenesis of RA and osteoarthritis, emphasizing their potential as therapeutic targets and diagnostic biomarkers. EVs contribute to various pathological processes by transferring proteins, microRNAs (miRNAs), and mRNAs, facilitating inflammation, apoptosis resistance, antigen presentation, extracellular matrix degradation, and angiogenesis. In the synovial fluid of RA patients, EVs carry pro-inflammatory factors (e.g., tumor necrosis factor-α [TNF-α] and IL-6) and matrix-degrading enzymes (e.g., MMP-13), exacerbating inflammatory interactions between synovial and cartilage cells. Additionally, EVs exhibit specific protein and miRNA expression profiles, suggesting their potential as diagnostic biomarkers.

The review further highlights the dual regulatory roles of miRNA cargo in EVs in modulating inflammation. It underscores the significant therapeutic potential of EV-based approaches, such as loading anti-inflammatory miRNAs or delivering targeted drugs. This review offers novel perspectives on cell-free precision therapies and early diagnostic strategies for RA.^[19]

Co-cited authors are researchers frequently referenced together in academic literature, reflecting their foundational contributions to a specific field. As shown in Table 3, Gay S is the most co-cited author (141 co-citations), followed by Nagy G (104) and Jorgensen C (94). Among the 23,885 co-cited authors, 5 have been co-cited over 100 times.

One of the most frequently cited reviews coauthored by Gay S and Nagy G, titled Emerging Role of EVs in Inflammatory Diseases, comprehensively examines the biological properties and immunoregulatory functions of EVs, as well as their role in inflammatory diseases, including RA. For RA, the review discusses the contributions of EVs to synovitis, immune cell dysregulation, and bone destruction, with a focus on their role as miRNA carriers and their association with disease progression. The study systematically elucidates the central role of EVs in RA immunoregulation and tissue destruction, highlighting their dual functions as both drivers of inflammation and key modulators of disease progression. Their involvement in inflammation propagation, immune imbalance, and bone destruction is presented with clarity and depth.^[13]

3.5. Hotspots investigation

3.5.1. Highly valuable papers

To evaluate the impact of publications within this research field, we first analyzed citation patterns. Table 4 highlights the top 10 most locally cited documents in RA-EVs research (Most Local Cited Documents), while Table 5 lists the top 10 most widely cited references. These statistics enable the identification of highly influential studies that have significantly shaped this field.

Table 4.

The top 10 documents with the most local citations.

Rank	Title	TC	Journals	IF	PY	Author
1	Therapeutic potential of mesenchymal cell-derived miRNA-150-5p–expressing exosomes in rheumatoid arthritis mediated by the modulation of MMP14 and VEGF	85	The Journal of Immunology	3.6	2018	Zhe Chen
2	Mesenchymal stem cells-derived exosomes are more immunosuppressive than microparticles in inflammatory arthritis	64	Theranostics	12.4	2018	Stella Cosenza
3	Extracellular vesicles in the pathogenesis of rheumatoid arthritis and osteoarthritis	55	Arthritis Research & Therapy	4.4	2016	Joseph Withrow
4	The exposure of autoantigens by microparticles underlies the formation of potent inflammatory components: the microparticle‐associated immune complexes	49	EMBO Molecular Medicine	9.0	2013	Nathalie Cloutier
5	Association of citrullinated proteins with synovial exosomes	47	Arthritis & Rheumatism	11.4	2006	K Skriner
6	Increased levels of circulating microparticles in primary Sjögren’s syndrome, systemic lupus erythematosus and rheumatoid arthritis and relation with disease activity	47	Arthritis Research & Therapy	4.4	2009	Jérémie Sellam
7	Neutrophil-derived microvesicles enter cartilage and protect the joint in inflammatory arthritis	45	Science Translational Medicine	15.8	2015	Sarah E. Headland
8	A membrane form of TNF-α presented by exosomes delays T-cell activation-induced cell death	41	The Journal of Immunology	3.6	2006	Huang-Ge Zhang
9	PBMC and exosome-derived hotair is a critical regulator and potent marker for rheumatoid arthritis	40	Clinical and Experimental Medicine	3.2	2015	Jinsoo Song
10	Exosomal MicroRNA-320a derived from mesenchymal stem cells regulates rheumatoid arthritis fibroblast-like synoviocyte activation by suppressing CXCL9 expression	34	Frontiers in Physiology	3.2	2020	Qing Meng

Table 5.

The top 10 most co-cited references in the field of RA-EVs.

Rank	Title	LC	Journals	IF	PY	Author
1	Therapeutic potential of mesenchymal cell-derived miRNA-150-5p–expressing exosomes in rheumatoid arthritis mediated by the modulation of MMP14 and VEGF	85	The Journal of Immunology	3.6	2018	Zhe Chen
2	Mesenchymal stem cells-derived exosomes are more immunosuppressive than microparticles in inflammatory arthritis	64	Theranostics	12.4	2018	Stella Cosenza
3	Platelets amplify inflammation in arthritis via collagen-dependent microparticle production	62	Science	44.7	2010	Eric Boilard
4	Exosome-mediated transfer of mRNAs and microRNAs is a novel mechanism of genetic exchange between cells	59	Nature Cell Biology	17.3	2007	Hadi Valadi
5	Minimal information for studies of extracellular vesicles 2018 (MISEV2018): a position statement of the International Society for Extracellular Vesicles and update of the MISEV2014 guidelines	56	Journal of Extracellular Vesicles	15.5	2018	Clotilde Théry
6	Extracellular vesicles in the pathogenesis of rheumatoid arthritis and osteoarthritis	55	Arthritis Research & Therapy	4.4	2016	Joseph Withrow
7	The exposure of autoantigens by microparticles underlies the formation of potent inflammatory components: the microparticle‐associated immune complexes	49	EMBO Molecular Medicine	9.0	2013	Nathalie Cloutier
8	Elevated levels of platelet microparticles are associated with disease activity in rheumatoid arthritis	49	Arthritis & Rheumatism	11.4	2002	EAJ Knijff‐Dutmer
9	The biology,function,and biomedical applications of exosomes	47	Science	44.7	2020	Raghu Kallur
10	Increased levels of circulating microparticles in primary Sjögren’s syndrome, systemic lupus erythematosus and rheumatoid arthritis and relation with disease activity	47	Arthritis Research & Therapy	4.4	2009	Jérémie Sellam

EVs = extracellular vesicles, RA = rheumatoid arthritis.

Among the most cited studies, Therapeutic Potential of Mesenchymal Cell-Derived miRNA-150-5p–Expressing Exosomes in RA Mediated by the Modulation of MMP14 and VEGF has received 85 citations.^[20] This study demonstrated that miR-150-5p expression is significantly downregulated in RA patients, while MMP14 and VEGF are upregulated. These changes exacerbate RA pathology by increasing the invasiveness of fibroblast-like synoviocytes (FLS) and promoting angiogenesis.

To address this imbalance, the researchers transfected mesenchymal stem cells (MSCs) with miR-150-5p expression plasmids to generate miR-150-5p-enriched exosomes (Exo-150). Exo-150 directly targeted the 3′ untranslated regions (3′UTRs) of MMP14 and VEGF, significantly reducing their expression levels. In vitro, Exo-150 effectively suppressed the migration, invasion, and pro-angiogenic activities of rheumatoid arthritis fibroblast-like synoviocytes (RA-FLS). In vivo, in a collagen-induced arthritis (CIA) mouse model, Exo-150 significantly reduced arthritis scores, alleviated joint swelling, and decreased synovial angiogenesis, leading to marked improvements in inflammation and tissue damage. This study provides compelling evidence for the therapeutic potential of exosomes as miRNA delivery systems in RA treatment.

The second most-cited paper, authored by Stella et al, is titled MSCs-derived exosomes are more immunosuppressive than microparticles in inflammatory arthritis.^[21] This study investigates the immunoregulatory effects of exosomes (Exos) and microparticles (MPs) secreted by MSCs in inflammatory arthritis. The findings demonstrate that both MSC-derived exosomes and microparticles exhibit anti-inflammatory properties by inhibiting T and B -cell proliferation and promoting the differentiation of regulatory T-cells and IL-10-expressing regulatory B cells (Bregs).

In a CIA mouse model, exosomes significantly alleviated arthritis symptoms, reduced clinical scores, and minimized bone damage, whereas microparticles showed relatively weaker effects. Notably, exosomes appeared to provide superior immunomodulatory effects by targeting the inflammatory microenvironment and modulating the differentiation and function of T and B-cells. The anti-inflammatory effects of exosomes were strongly associated with reduced differentiation of plasmablasts and an increased proportion of Bregs.

These highly cited studies have significantly advanced our understanding of the critical role of EVs in the pathogenesis of RA, particularly in enhancing antigen delivery and immune cell activation. Additionally, they have explored the therapeutic potential of MSC-derived exosomes in alleviating RA. As research on EVs continues to evolve, these findings offer promising new directions for RA treatment. A more detailed analysis of these therapeutic implications will be provided in the discussion section of this paper.

3.5.2. Analysis of keywords

Keywords reflect the core research topics within the literature, making keyword analysis an effective tool in bibliometrics for identifying hotspots and trends in RA research. Table 6 lists the top 20 most frequently occurring terms in this field. The top 3 keywords are “rheumatoid arthritis” (180 occurrences), “extracellular vesicles” (96 occurrences), and “exosomes” (76 occurrences), which align closely with the central themes of this study.

Table 6.

Top 20 keywords on research of RA-EVs.

Rank	Keywords	Occurrences	Rank	Keywords	Occurrences
1	Rheumatoid-arthritis	180	11	Cells	38
2	Extracellular vesicles	96	12	Microvesicles	38
3	Exosomes	76	13	Microparticles	36
4	Expression	72	14	Activation	34
5	Inflammation	61	15	In-vitro	30
6	Mesenchymal stem-cells	47	16	Therapy	30
7	Dendritic cells	45	17	Fibroblast-like synoviocytes	29
8	T-cells	45	18	Cancer	28
9	Stromal cells	41	19	Cell-derived microparticles	28
10	Systemic lupus erythematosus	40	20	Circulating microparticles	28

EVs = extracellular vesicles, RA = rheumatoid arthritis.

Beyond these core terms, keywords such as “inflammation” (61 occurrences), “T-cells” (45 occurrences), and “dendritic cells” (45 occurrences) indicate significant research focus on immune cell regulation and inflammatory mechanisms in RA. Terms like “mesenchymal stem cells” (47 occurrences) and “stromal cells” (41 occurrences) highlight the growing interest in EVs derived from stem and stromal cells for their potential therapeutic applications in RA.

Keyword co-occurrence analysis helps identify research priorities within a given field. Using a minimum co-occurrence threshold of 5, 230 keywords were included in the clustering analysis performed with VOSviewer. These keywords were grouped into several clusters, each representing distinct research themes.

As shown in Figure 7A, the red cluster centers around the core keyword “RA” and includes terms such as “inflammation,” “disease,” “biomarkers,” “synovial fluid,” “platelet microparticles,” and “neutrophils.” This cluster reflects the pathological features of RA, particularly research on inflammation and its role in disease progression. Keywords like “inflammation” and “synovial fluid” suggest a strong focus on synovial inflammation and its critical role in RA pathology.

The blue cluster includes keywords such as “dendritic cells,” “regulatory T-cells,” “autoimmunity,” “cytokines,” and “microRNAs.” This cluster represents a major research direction exploring how exosomes regulate immune cell function, including dendritic cells and regulatory T-cells, by delivering miRNAs or cytokines. These studies focus on the mechanisms of inflammation and immune dysregulation in RA.

The yellow cluster features terms like “mesenchymal stem cells,” “stromal cells,” “stem cells,” and “immunomodulation.” This cluster highlights the therapeutic potential of EVs, particularly those derived from stem and stromal cells. It represents a shift from basic research toward clinical translation, focusing on how these vesicles regulate angiogenesis and promote tissue repair, offering novel strategies for RA treatment.

The green cluster includes keywords such as “therapy,” “drug delivery,” and “mechanisms.” This cluster focuses on the secretion regulation, biological characteristics, and potential applications of exosomes in drug delivery. Researchers are actively developing novel exosome-based therapeutic strategies, emphasizing their application in targeted therapy and disease modulation.

3.5.3. Trend topic analysis

Using the trend topic analysis feature of the R package “Bibliometrix” (Fig. 7B), we identified key research areas over specific periods and observed the latest trends in the field.

During the early period (2010–2015), keywords predominantly focused on basic research topics such as “membrane microparticles,” “endothelial microparticles,” and “complement activation.” These terms reflect an emphasis on the fundamental properties of EVs and their roles in the complement system.

In the mid-period (2016–2020), keywords shifted toward immunology and disease mechanisms, including “dendritic cells,” “inflammation,” “synovial fluid,” and “NF-kappa-B.” This trend indicates a growing focus on exploring the role of EVs in inflammatory and immune responses.

The recent period (2021–2024) highlights therapeutic applications and translational research, with keywords such as “mesenchymal stem cells,” “stem cells,” and “exosomes.” These terms underscore the increasing attention on the immunomodulatory and therapeutic potential of mesenchymal stem cell-derived EVs in RA treatment, marking a shift from mechanistic studies toward clinical applications.

Overall, Figure 7B clearly illustrates the evolution of research hotspots in the RA-EVs field. The progression spans from fundamental studies on EV secretion and properties, to their roles in inflammation and immune regulation, and finally to clinical translation, including mesenchymal stem cell-derived extracellular vesicles (MSC-EVs)-based therapies and drug delivery. This trajectory reflects a deepening understanding of EVs and their growing potential for real-world applications.

4. Discussion

Using the WOSCC database, this study identified literature on EVs, and RA published between 2014 and 2024. Two bibliometric analysis tools were employed to visualize and analyze the data, offering a comprehensive understanding of the research landscape of EVs in RA over the past decade. The aim was to explore key research hotspots and emerging trends in this field.

Our analysis of highly cited papers and high-frequency keywords revealed that the most impactful studies primarily focus on the role of EVs in RA pathogenesis. A particular emphasis was placed on immune cell-derived EVs and their cargo, which appear to represent a major research hotspot (Fig. 8). Furthermore, the therapeutic potential of mesenchymal stem cell-derived EVs in alleviating RA is emerging as a promising frontier in this area (Fig. 9).

Figure 8.

Roles of EVs in pathophysiology of RA. RA = rheumatoid arthritis.

Figure 9.

The potential of MSC-EVs in rheumatoid arthritis therapy. MSC-EVs = mesenchymal stem cell-derived extracellular vesicles.

4.1. Role of immune cell-derived EVs in RA pathogenesis

4.1.1. Stage of autoimmune activation

In the early stages of RA, the breakdown of self-antigen tolerance and aberrant immune activation are critical pathological events. EVs, as key mediators of intercellular communication, play pivotal roles in these processes by modulating antigen delivery, immune cell activation, and polarization.

One of the hallmark events in early RA is the abnormal recognition of modified self-antigens by the immune system, particularly citrullinated antigens, which are closely associated with RA disease activity. EVs are instrumental in this process.^[22] Studies have shown that FLS and neutrophils, under the stimulation of pro-inflammatory factors (e.g., TNF-α) and oxidative stress, release EVs enriched with citrullinated proteins.^[23] Research by Ucci et al demonstrated that EVs present citrullinated antigens on their surface, with significantly higher expression in EVs from RA patients compared to healthy donors.^[24] These EVs are taken up by antigen-presenting cells, delivered to MHC II molecules, and presented to CD4⁺ T-cells, initiating T-cell activation. This antigen delivery accelerates the recognition of modified antigens and promotes the production of ACPAs (ACPA). These ACPAs form immune complexes with the modified antigens, driving aberrant immune responses.^[25]

Furthermore, studies have confirmed that FLS-derived EVs contain citrullinated peptides and IgG, while platelet-derived EVs carry citrullinated epitopes on their surface, contributing to immune complex formation and perpetuating RA pathogenesis.^[26]

Beyond antigen delivery, EVs are closely associated with the formation of RA-specific autoantibodies. Plasma-derived EVs in RA patients carry rheumatoid factor (RF), which may serve as a novel biomarker for disease severity. Aarnts et al found that patients with IgM-RF-positive plasma EVs exhibited significantly higher DAS28, ESR, and VAS scores, along with elevated C-reactive protein (CRP) levels, compared to patients with RF-negative EVs.^[27]

Building on their role in antigen delivery, EVs play a crucial regulatory role in immune cell activation and polarization. Zhang et al demonstrated that exosomes derived from FLS (RA-FLS-exos) in RA patients carry TNF-α, which may inhibit activation-induced cell death in T-cells, rendering these activated T-cells resistant to apoptosis.^[28]

Moreover, under hypoxic conditions, exosomes secreted by FLSs are enriched with miR-424. These exosomes promote the differentiation of Th17 cells while suppressing Treg cell function, leading to an imbalance in the Treg/Th17 ratio and exacerbating the inflammatory response in RA.^[29] An increased Th17 cell population and their cytokines, particularly IL-17, are strongly associated with RA disease activity.^[30] Importantly, Th17 cells further amplify joint inflammation and tissue destruction by activating FLSs and macrophages, which subsequently release large quantities of pro-inflammatory cytokines, intensifying RA pathology.^[31]

Furthermore, EVs carrying modified antigens and specific miRNAs can activate B-cells, driving the production of significant quantities of ACPAs and other autoantibodies. These autoantibodies, in turn, amplify immune cell activation, establishing a pathological positive feedback loop that exacerbates RA progression.^[32]

4.1.2. Stage of inflammation expansion

As RA progresses, synovial inflammation and hyperplasia become hallmark features of the disease. The synovial tissue exhibits pronounced inflammatory responses and pathological proliferation, with EVs playing a critical regulatory role in these processes. Key cell types within the RA synovium, including FLS, macrophages, neutrophils, and T-cells, contribute to the spread of inflammatory signals and the remodeling of the microenvironment through the release of EVs.

The pathological features of RA synovitis are characterized by excessive secretion of pro-inflammatory factors and the amplification of intercellular signaling. EVs released from local synovial tissue carry substantial amounts of pro-inflammatory cytokines (e.g., IL-6) and miRNAs (e.g., miR-21), which enhance pro-inflammatory responses within the synovial microenvironment through intercellular communication. These locally released EVs can also enter systemic circulation, activating immune cells in distant tissues and promoting systemic inflammation. This EV-mediated signal dissemination mechanism provides an explanation for the subclinical systemic inflammation observed during the early stages of RA.

FLS, macrophages, and neutrophils release EVs enriched with pro-inflammatory and highly reactive molecules in response to inflammatory stimuli such as TNF-α and IL-1β. These vesicles carry cytokines (e.g., IL-6 and TNF-α) and microRNAs (e.g., miR-155 and miR-146a), amplifying inflammatory signaling within the synovial microenvironment. Studies have demonstrated that platelet-derived microparticles (MPs) release IL-1β, which promotes joint inflammation by increasing IL-6 and IL-8 levels in fibroblasts from RA patients.^[33] Additionally, exosomes derived from FLS can stimulate CD4⁺ T-cells through several mechanisms, including inhibiting cytokine activation-induced cell death and caspase-3 cleavage, upregulating interferon and interleukin secretion, and enhancing the activation of the NF-κB and AKT signaling pathways.^[34]

As RA progresses, FLS acquire an invasive phenotype closely associated with synovial hyperplasia and periarticular soft tissue destruction. EVs play a crucial role in driving this transformation.^[19] EVs containing miR-203 and IL-6 induce FLS to adopt an invasive phenotype, enhancing their ability to penetrate the extracellular matrix.^[35] Additionally, FLS-derived EVs are enriched with matrix metalloproteinases, particularly MMP-1 and MMP-9, which degrade the extracellular matrix, facilitating FLS migration and invasion.^[19]

Pathological hyperplasia of the synovial tissue is another hallmark of RA, with the proliferation and antiapoptotic properties of FLS being significantly influenced by EVs. Studies have shown that synovial-derived EVs from RA patients are enriched with miR-21 and VEGF, which enhance FLS proliferation and inhibit apoptosis through activation of the PI3K-Akt signaling pathway. miR-21 further promotes Akt activation by targeting PTEN, creating a positive feedback loop that sustains the hyperproliferative state of FLS.^[36] Additionally, VEGF carried by EVs stimulates synovial angiogenesis, providing the essential blood supply and nutrients necessary to support synovial hyperplasia.

Inflammation and angiogenesis within the synovium are tightly interconnected processes, with EVs playing a pivotal role. Synovial-derived EVs carry high levels of VEGF and miR-126, which enhance pathological angiogenesis by promoting endothelial cell proliferation and migration. Additionally, macrophage-derived exosomal miR-103a activates the JAK/STAT3 signaling pathway, upregulating MMP14, VEGF, and CD31 expression, thereby driving both inflammation and angiogenesis in RA patients.^[37] These newly formed blood vessels not only provide increased blood flow to support synovial hyperplasia but also create pathways for sustained immune cell infiltration. Furthermore, pro-inflammatory factors within EVs increase vascular permeability, facilitating the diffusion of inflammatory molecules from the synovium to distant tissues and exacerbating systemic inflammation.

In the progression of synovial inflammation and hyperplasia in RA, EVs serve not only as critical initiators but also as sustainers of the pathological synovial microenvironment through intercellular communication. The secretion and cargo of EVs are regulated by pro-inflammatory factors within the synovium. In turn, EVs amplify pro-inflammatory signaling by activating FLS and immune cells, establishing a pathological positive feedback loop. This vesicle-mediated signal amplification underpins the persistent and irreversible nature of synovial inflammation and hyperplasia in RA.

4.1.3. Stage of joint destruction

Cartilage and bone destruction represent critical end-stage manifestations of RA, leading directly to irreversible joint damage and functional loss. EVs play a pivotal role during this phase, mediating cartilage matrix degradation, chondrocyte apoptosis and dysfunction, heightened bone resorption, and suppressed osteogenesis through complex molecular mechanisms and pathological intercellular communication.

In cartilage destruction, EVs act as carriers for matrix-degrading enzymes, particularly matrix metalloproteinases, which degrade type II collagen and proteoglycans in the cartilage matrix, compromising its structural integrity. FLS within the RA microenvironment secrete EVs enriched with MMP-1, MMP-3, and MMP-9. These enzymes, either through direct interaction with chondrocytes or by diffusing into the joint cavity, significantly amplify matrix degradation and contribute to cartilage damage.^[38,39] Studies have shown that the activity of matrix metalloproteinases carried by EVs in the synovial fluid of RA patients is markedly higher than in healthy individuals, and this activity correlates positively with the severity of cartilage destruction.^[40] Additionally, RA-FLS-exos inhibit chondrocyte proliferation and migration while promoting their apoptosis, further exacerbating cartilage damage.^[41]

In the pathological stage of bone and cartilage destruction in RA, EVs not only contribute to cartilage degradation but also profoundly influence bone metabolic balance. Synovial-derived EVs from RA patients exhibit a higher affinity for receptor activator of nuclear factor κB ligand (RANKL) and demonstrate greater potential to induce osteoclast formation compared to EVs from patients with osteoarthritis or ankylosing spondylitis.^[42] These EVs carry high levels of RANKL, which significantly promotes the differentiation and activation of osteoclasts. Additionally, RA synovial EVs are enriched with pro-inflammatory miRNAs, such as miR-146a and miR-155, which further enhance bone resorption activity by activating the NF-κB signaling pathway in osteoclasts. Supporting evidence indicates that RANKL-enriched EVs in the synovial fluid of RA patients are strongly associated with increased osteoclast activity. Elevated levels of these EVs correlate positively with the severity of bone destruction, highlighting their critical role in RA-related bone damage.^[43]

Meanwhile, EVs, primarily synovial-derived EVs from RA patients, exacerbate bone loss and impair bone repair by inhibiting osteoblast activity. In vitro studies have shown that RA-FLS-derived exosomes (RA-FLS-exos) reduce osteoblast proliferation, mineralization, and differentiation.^[44] Furthermore, TNF-α has been shown to stimulate FLS-derived exosomes to secrete miR-221-3p. This exosomal miR-221-3p enters osteoblasts, where it inhibits osteoblast differentiation and maturation by modulating the Wnt signaling pathway and downregulating bone metabolism-related genes, including TCF4, Dkk2, Runx2, and ESR1.^[34] This imbalance between enhanced osteoclast activity and suppressed osteoblast function ultimately accelerates bone loss and joint erosion in RA patients.

Notably, EVs also contribute to the pathological interaction between osteoclasts and chondrocytes, further exacerbating joint destruction in late-stage RA. Synovial EVs promote damage not only through direct effects on cartilage and bone cells but also by activating the DAMPs (damage-associated molecular patterns) pathway, which induces synovial tissue to secrete additional EVs. This feedback loop sustains elevated EV concentrations in the local microenvironment, amplifying destructive inflammatory responses and accelerating disease progression.

In summary, EVs play a pivotal role across various pathological stages of RA. They act as catalysts for immune activation and inflammation expansion, as well as key drivers of joint destruction. By delivering modified antigens, activating immune cells, modulating immune responses, and influencing cellular metabolism, EVs amplify pathological signaling and contribute to the progressive nature of RA, ultimately resulting in irreversible joint damage and functional loss. The multifunctionality and central role of EVs in RA pathogenesis highlight their potential as promising therapeutic targets for novel treatment strategies.

4.2. The potential of mesenchymal stem cell-derived extracellular vesicles in RA therapy

MSCs are multipotent stromal cells endowed with self-renewal and multilineage differentiation capabilities. Owing to their robust immunomodulatory properties, MSCs have been extensively employed in the treatment of autoimmune diseases. They exert their effects predominantly through the secretion of a diverse array of bioactive factors, which in turn modulate the functions of key immune cell populations – including monocytes/macrophages, T-cells, and B cells – thereby orchestrating the overall immune response. In the context of RA, MSCs alleviate clinical symptoms and slow disease progression via immune regulation; however, their direct clinical application is hindered by challenges such as immunogenicity, potential tumorigenicity, and limitations related to in vivo survival and homing.^[45]

To address these limitations, EVs derived from MSCs (MSC-EVs) have emerged as a promising cell-free therapeutic alternative. MSC-EVs preserve the inherent immunomodulatory and tissue-reparative functions of their parent cells while circumventing the safety concerns associated with live cell therapies. As natural nanocarriers, MSC-EVs are characterized by low immunogenicity, minimal toxicity, and excellent biocompatibility. They exhibit enhanced stability in systemic circulation and superior tissue penetration compared to MSCs. Moreover, through targeted engineering modifications, MSC-EVs can be endowed with improved targeting capabilities, facilitating their accumulation at inflammatory sites and thereby augmenting therapeutic efficacy.^[46,47] A comprehensive understanding of the mechanisms underlying MSC-EV action and the development of optimized application strategies is essential for advancing safe and effective treatments for RA.

4.2.1. Targeting RA-FLSs

FLSs in RA are characterized by their high invasiveness and hyperproliferative behavior. These cells secrete various proteases and pro-inflammatory cytokines, which accelerate the degradation of articular cartilage and bone. A substantial body of research indicates that MSC-EVs can deliver a wide range of bioactive molecules – particularly noncoding RNAs – to target RA-FLSs, thereby mitigating inflammation and promoting tissue repair.

Firstly, MSC-EVs effectively inhibit the invasion and proliferation of RA-FLSs through the targeted delivery of specific noncoding RNAs. For example, gingiva-derived MSCs and their exosomes have been shown to induce programmed cell death in FLSs from RA patients and reduce MMP14-mediated cartilage degradation.^[48] Similarly, exosomes derived from human umbilical cord MSCs carrying miR-451a or miR-140-3p can respectively suppress FLS invasion and migration by downregulating ATF2 or SGK1.^[49,50] Additionally, the long noncoding RNA HAND2-AS1, which is downregulated in RA synovial tissue, can be delivered via MSC-EVs to attenuate FLS invasion and inflammation through the inhibition of NF-κB activity.^[51]

Moreover, certain miRNAs contained within MSC-EVs have the capacity to promote apoptosis in RA-FLSs. Molecules such as miR-124a, miR-320a, miR-34a, and miR-140-3p can, via MSC-EV delivery, induce cell cycle arrest in FLSs, activate the Bax/Bid/Bim signaling cascade, or inhibit the ERK1/2 and ATM/ATR/p53 pathways. These actions collectively restrain abnormal cell proliferation and enhance apoptotic processes.^[52–55]

Simultaneously, MSC-EVs can modulate the secretion of inflammatory cytokines by RA-FLSs, thus alleviating RA-associated inflammation. For instance, MSC-EVs enriched with miR-205-5p downregulate the MAPK and NF-κB pathways, reducing the expression of MMP-1 and MMP-13, which in turn ameliorates joint inflammation.^[56] Additionally, MSC-EVs carrying miR-21 have demonstrated potential in reducing inflammatory markers in a CIA model; however, their efficacy in autoimmune conditions remains a subject of debate, possibly due to differences in disease stage or the cellular microenvironment.^[50,57] Similarly, miR-150-5p exhibits a context-dependent dual regulatory effect: on 1 hand, it is thought to promote FLS proliferation by lowering SOCS1 levels,^[58] while on the other, high levels of Exo-150 can suppress angiogenesis and tissue hyperplasia by inhibiting MMP14 and VEGF.^[20]

4.2.2. Targeting RA-T-cells

The imbalance between pro-inflammatory Th17 cells and anti-inflammatory Treg cells is a critical pathological mechanism underlying RA. Treg cells maintain immune tolerance and suppress inflammation through the secretion of IL-10 and TGF-β, whereas hyperactivated Th17 cells secrete IL-17, which in turn stimulates FLSs to produce IL-6 and TNF-α, further exacerbating inflammatory responses and bone destruction.

Mesenchymal stem cell-derived EVs (MSC-EVs) have emerged as effective modulators of T-cell function, capable of alleviating this immune imbalance and ameliorating RA pathology. For instance, studies have demonstrated that high doses of small EVs derived from human umbilical cord MSCs (hUCMSC-sEV) can restore the Th17/Treg balance and suppress the expression of inflammatory cytokines with efficacy comparable to, or even surpassing, that of methotrexate (MTX).^[59] The underlying mechanisms include the inhibition of T-cell proliferation, the induction of apoptosis, a reduction in IL-17 levels, and an increase in IL-10 and TGF-β. Additionally, hUCMSC-sEV have been shown to downregulate the Th17 master transcription factor RORγt while upregulating the Treg-specific transcription factor FOXP3, thereby reestablishing the Th17/Treg equilibrium.^[59]

Other sources of MSC-EVs have similarly demonstrated potent immunomodulatory effects on T-cells. Exosomes derived from bone marrow MSCs (bone marrow mesenchymal stem cell-Exo) can transport the long noncoding RNA TUG1 to CD4⁺ T-cells, thereby promoting BLIMP1-mediated Treg generation while simultaneously inhibiting Th17 cell differentiation. This dual action results in reduced secretion of IL-17 and TNF-α and increased production of IL-10, which further corrects RA-associated immune imbalances and inflammation.^[60]

Gingival mesenchymal stem cells (GMSC) also produce EVs that preferentially accumulate in inflamed synovial tissues. These EVs deliver miR-148a-3p to target cells, thereby negatively regulating the IKKβ/NF-κB signaling pathway, modulating the Treg/Th17 balance, and ultimately reducing synovial inflammation.^[61]

Moreover, exosomes derived from genetically engineered MSCs that carry miR-146a have been shown to inhibit the NF-κB pathway, leading to the downregulation of T-bet and interferon-γ. This mechanism suppresses Th1 cell differentiation and alleviates RA-associated inflammation.^[62]

Adipose-derived mesenchymal stem cell (AMSCs) further contribute to this therapeutic landscape; their exosomes (AMSC-Exo) can deliver miR-29b, which inhibits RORγt and IL-17, thereby reducing the proportion of Th17 cells. Concurrently, miR-29b upregulates FoxP3 and TGF-β to promote Treg differentiation, effectively restoring the Th17/Treg balance. In addition, miR-29b suppresses the differentiation of Th1 and Th2 cells, further enhancing the overall immunomodulatory effects.^[63]

4.2.3. Targeting RA-macrophage

The polarization state of synovial macrophages is intimately linked to both the activity and severity of RA. Hyperactivated M1 macrophages secrete high levels of pro-inflammatory cytokines – such as TNF-α, IL-1β, and IL-6 – thereby exacerbating synovial inflammation and accelerating bone destruction. In contrast, M2 macrophages release anti-inflammatory mediators like IL-10 that help to alleviate inflammation and promote tissue repair.^[64] Consequently, strategies aimed at reprogramming macrophages from an M1 to an M2 phenotype have emerged as key approaches for mitigating the inflammatory microenvironment and reducing joint damage in RA.

Mesenchymal stem cell-derived EVs (MSC-EVs) have demonstrated significant immunomodulatory potential in this context. Notably, MSC-EVs can both suppress the pro-inflammatory activity of M1 macrophages and enhance the anti-inflammatory and regenerative functions of M2 macrophages. For example, MSC-EVs preconditioned with RA patient serum (Exo-RA) have been shown to downregulate inflammatory mediators such as IL-17 and IL-1β while upregulating TGF-β1 expression. This modulation promotes the cooperative effects of Th2 cells and M2 macrophages, resulting in a marked reduction in joint inflammation.^[65]

In addition, exosomes derived from gingiva-derived MSCs (GMSC) can induce macrophage polarization toward the M2 phenotype by downregulating M1-associated factors – including TNF-α, IL-12, and IL-1β – and concurrently upregulating anti-inflammatory cytokines such as IL-10.^[66] In high-lipid environments, these exosomes are also capable of partially restoring PPAR-γ expression in macrophages, thereby reducing lipid accumulation and further suppressing inflammatory responses.^[67]

Adipose-derived MSC exosomes (AdMSC-Exo) further contribute to macrophage reprogramming by engaging signaling pathways such as Stat6 and MafB, which promote M2 polarization and enhance the secretion of IL-10 and TSG-6.^[68] When pretreated with interferon-γ and TNF-α, these exosomes become enriched with immunomodulatory molecules – including miR-34a-5p, miR-146a-5p, and miR-21-5p – that further downregulate pro-inflammatory cytokines like TNF-α and IL-1β while upregulating IL-10, thereby bolstering their anti-inflammatory efficacy.^[69] In RA mouse models, AMSC-EVs delivering interleukin-1 receptor antagonist (IL-1ra) have effectively suppressed the secretion of IL-1β and TNF-α, resulting in a significant attenuation of joint inflammation.^[70]

Moreover, exosomes derived from human Wharton’s jelly MSCs (hWJ-MSC) have been shown, in osteochondral defect models, not only to reduce intra-articular inflammation but also to markedly stimulate chondrocyte proliferation and induce the polarization of macrophages toward the M2 phenotype.^[71] Similarly, bone marrow MSC-derived exosomes carrying miR-223 can directly inhibit key components of the NLRP3 inflammasome within macrophages, thereby reducing the release of IL-1β and IL-18.^[72] Exosomes enriched with miR-146a further attenuate the activation of the NF-κB pathway by downregulating TRAF6 and IRAK1, leading to a decrease in the production of pro-inflammatory cytokines such as TNF-α and IL-6.^[73]

It is noteworthy that the synergistic action of various noncoding RNAs and proteins within MSC-EVs further amplifies the anti-inflammatory and regenerative capacity of M2 macrophages. For instance, miR-24-3p and let-7b-5p can activate the JAK/STAT signaling pathway and upregulate anti-inflammatory cytokines such as IL-10 and IL-4, while the inhibition of NF-κB signaling by let-7b-5p reduces the production of pro-inflammatory mediators. Additionally, proteins such as CD73 present in MSC-EVs can increase adenosine levels and activate the AKT phosphorylation pathway, thereby enhancing M2 polarization and facilitating the repair of damaged tissues.^[74]

5. Outlook

In the study of RA and EVs, while EVs have been widely recognized as critical mediators of intercellular communication, numerous challenges and limitations remain. EVs have been demonstrated to play significant roles in regulating inflammation, disrupting immune balance, and driving joint destruction in RA. However, RA is a dynamic disease, and factors such as hypoxia, pH fluctuations, and mechanical stress within the inflammatory microenvironment may significantly influence the secretion and functionality of EVs. Current research largely focuses on EV functionality under idealized and static conditions, failing to replicate the complexities of the actual RA microenvironment. Consequently, there is a lack of detailed insights into the spatiotemporal dynamics of EVs during RA progression.

The heterogeneity of EVs poses another major challenge. This heterogeneity significantly limits the depth of functional analyses, as current studies predominantly focus on average effects without precise investigation of EV subtypes and their specific functions. Unfortunately, existing technologies are insufficient for efficiently isolating and characterizing functionally distinct EV subtypes.^[75] Current EV isolation techniques, such as ultracentrifugation and column chromatography, struggle to achieve both high purity and efficiency, especially when working with highly viscous synovial fluid from RA patients. Tools for EV characterization, such as nanoparticle tracking analysis and electron microscopy, excel in size and concentration analysis but fail to directly link EVs to their functional properties. Distinguishing between pro-inflammatory and anti-inflammatory EVs derived from various cellular sources will require the development of advanced high-resolution technologies in the future.

In addition, the cargo of EVs, including miRNAs, lncRNAs, and proteins, serves as the core mediators of their function. However, current research primarily focuses on the role of individual molecules, overlooking the synergistic interactions among different cargo components. For a complex disease like RA, the mechanisms by which EVs functionally coordinate their cargo to systematically regulate specific signaling pathways, such as NF-κB and JAK-STAT, remain underexplored.

In clinical applications, while MSC-derived EVs hold potential, large-scale studies in RA patients are lacking, and current research focuses on small sample sizes. Challenges in EV standardization, quality control, and safety evaluation hinder their translational use. Furthermore, the secretion profiles and functional properties of EVs may vary significantly among different RA subtypes, such as seropositive and seronegative RA, yet current studies have largely neglected incorporating patient stratification into their research designs. These issues significantly hinder the translational progress of EVs in RA diagnosis and therapy.

Future research should emphasize comprehensive, systemic analyses using advanced models like multicellular co-cultures and spatial transcriptomics to explore the interactions and impact of EVs in the RA microenvironment. Enhanced EV isolation technologies, such as microfluidic chips, will improve research accuracy, and multi-omics approaches can provide a holistic understanding of EV cargo and its role in immune regulation and tissue damage. Clinically, liquid biopsy technologies for detecting EV biomarkers and large-scale trials are essential for advancing EV-based diagnostics and therapies in RA, with a focus on safety, efficacy, and long-term outcomes.

6. Strength and limitation

This study employed systematic bibliometric analysis using VOSviewer software and the R package “Bibliometrix,” ensuring objectivity in data analysis. By providing a comprehensive overview of research hotspots and emerging trends, it offers valuable insights for researchers in the field. However, the study has some limitations. It solely includes English-language publications from the WOSCC database. Future research should consider integrating additional databases, such as the China National Knowledge Infrastructure and Scopus, to offer a more comprehensive perspective.

7. Conclusion

Based on a bibliometric analysis of reviews and original research articles from the WOSCC, we have gained a comprehensive understanding of the research landscape on EVs in RA. This field has demonstrated robust growth, attracting increasing attention from scholars worldwide. In recent years, the investigation of EVs in RA, particularly their involvement in pathogenesis and therapeutic potential, has emerged as a prominent research focus.

In this study, we have conducted an in-depth discussion of current findings, highlighted existing gaps, and provided insights into future directions. Overall, the prospects for EV research in RA are highly promising. Through advancements in basic research, innovative technologies, and clinical translation, EVs are poised to play an increasingly pivotal role in RA diagnosis, prognostic evaluation, and treatment. Continued efforts are essential to elevate this field to new heights, ultimately benefiting the wider RA patient community.

Author contributions

Conceptualization: Tao Wang.

Data curation: Xiaoxia Tang.

Investigation: Wen Luo.

Methodology: Chen Yin Lu.

Project administration: Ze Hua Chen.

Resources: Yang Shu.

Software: Xiaohan Zhou.

Validation: Yubo Xia.

Visualization: Wenjie Su.

Writing – original draft: Biao Zhou, Zhiqiang Luo.

Writing – review & editing: Qigang Chen, Zhen Shen.