Interactions between rheumatoid arthritis synovial fibroblast migration and endothelial cells

The role of vascular and lymphatic networks in bone and joint homeostasis and pathology

The vascular and lymphatic systems are integral to maintaining skeletal homeostasis and responding to pathological conditions in bone and joint tissues. This review explores the interplay between blood vessels and lymphatic vessels in bones and joints, focusing on their roles in homeostasis, regeneration, and disease progression. Type H blood vessels, characterized by high expression of CD31 and endomucin, are crucial for coupling angiogenesis with osteogenesis, thus supporting bone homeostasis and repair. These vessels facilitate nutrient delivery and waste removal, and their dysfunction can lead to conditions such as ischemia and arthritis. Recent discoveries have highlighted the presence and significance of lymphatic vessels within bone tissue, challenging the traditional view that bones are devoid of lymphatics. Lymphatic vessels contribute to interstitial fluid regulation, immune cell trafficking, and tissue repair through lymphangiocrine signaling. The pathological alterations in these networks are closely linked to inflammatory joint diseases, emphasizing the need for further research into their co-regulatory mechanisms. This comprehensive review summarizes the current understanding of the structural and functional aspects of vascular and lymphatic networks in bone and joint tissues, their roles in homeostasis, and the implications of their dysfunction in disease. By elucidating the dynamic interactions between these systems, we aim to enhance the understanding of their contributions to skeletal health and disease, potentially informing the development of targeted therapeutic strategies.

Redefinition of Synovial Fibroblasts in Rheumatoid Arthritis

The breakdown of immune tolerance and the rise in autoimmunity contribute to the onset of rheumatoid arthritis (RA), driven by significant changes in immune components. Recent advances in single-cell and spatial transcriptome profiling have revealed shifts in cell distribution and composition, expanding our understanding beyond molecular-level changes in inflammatory cytokines, autoantibodies, and autoantigens in RA. Surprisingly, synovial fibroblasts (SFs) play an active immunopathogenic role rather than remaining passive bystanders in RA, with notable alterations in their subpopulation distribution and composition. This study examines these changes in SF heterogeneity, assesses their impact on RA progression, and elucidates the immune characteristics and functions of SF subsets in the RA autoimmunity, encompassing both intrinsic and adaptive immunity. Additionally, this review discusses therapeutic strategies targeting immune SF subsets, highlighting the potential of future interventions in SF phenotypic reprogramming. Overall, this review redefines the role of SFs in RA and suggests targeting SF phenotypic reprogramming and its upstream molecules as a promising therapeutic approach to restore immune balance and modulate immune tolerance in RA.

Post-prostatic-massage urine exosomes of men with chronic prostatitis/chronic pelvic pain syndrome carry prostate-cancer-typical microRNAs and activate proto-oncogenes

Chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS) has a high prevalence of up to 15% and accounts for 90-95% of prostatitis diagnoses, and yet its etiopathogenesis and link to prostate cancer (PCa) are still unclear. Here, we investigated microRNAs in exosomes isolated from blood and post-prostatic-massage urine of CP/CPPS type IIIb patients and healthy men. THP-1 monocytes (human leukemia monocytic cell line) were treated with exosomes and subjected to mRNA arrays "Cancer Inflammation and Immunity Crosstalk" and "Transcription Factors." Using The Cancer Genome Atlas, the expression of CP/CPPS-associated microRNAs was analyzed in PCa and normal prostate tissue. In silico functional studies were carried out to explore the disease ontology of CP/CPPS. In CP/CPPS, urine exosomes exhibited significant upregulation of eight PCa-specific microRNAs (e.g., hsa-miR-501, hsa-miR-20a, and hsa-miR-106), whose target genes were significantly enriched for GO terms, hallmark gene sets, and pathways specific for carcinogenesis. In THP-1 monocytes, CP/CPPS-derived urine exosomes induced upregulation of PCa-associated proinflammatory genes (e.g., CCR2 and TLR2) and proto-oncogene transcription factors (e.g., MYB and JUNB). In contrast, CP/CPPS-derived blood exosomes exhibited molecular properties similar to those of healthy men. Thus, CP/CPPS exhibits molecular changes that constitute a risk for PCa and should be considered in the development of PCa biomarkers and cancer screening programs.

Synovial fibroblasts as potential drug targets in rheumatoid arthritis, where do we stand and where shall we go?

Fibroblast-like synoviocytes or synovial fibroblasts (FLS) are important cellular components of the inner layer of the joint capsule, referred to as the synovial membrane. They can be found in both layers of this synovial membrane and contribute to normal joint function by producing extracellular matrix components and lubricants. However, under inflammatory conditions like in rheumatoid arthritis (RA), they may start to proliferate, undergo phenotypical changes and become central elements in the perpetuation of inflammation through their direct and indirect destructive functions. Their importance in autoimmune joint disorders makes them attractive cellular targets, and as mesenchymal-derived cells, their inhibition may be carried out without immunosuppressive consequences. Here, we aim to give an overview of our current understanding of the target potential of these cells in RA.

Diversity of Vascular Niches in Bones and Joints During Homeostasis, Ageing, and Diseases

The bones and joints in the skeletal system are composed of diverse cell types, including vascular niches, bone cells, connective tissue cells and mineral deposits and regulate whole-body homeostasis. The capacity of maintaining strength and generation of blood lineages lies within the skeletal system. Bone harbours blood and immune cells and their progenitors, and vascular cells provide several immune cell type niches. Blood vessels in bone are phenotypically and functionally diverse, with distinct capillary subtypes exhibiting striking changes with age. The bone vasculature has a special impact on osteogenesis and haematopoiesis, and dysregulation of the vasculature is associated with diverse blood and bone diseases. Ageing is associated with perturbed haematopoiesis, loss of osteogenesis, increased adipogenesis and diminished immune response and immune cell production. Endothelial and perivascular cells impact immune cell production and play a crucial role during inflammation. Here, we discuss normal and maladapted vascular niches in bone during development, homeostasis, ageing and bone diseases such as rheumatoid arthritis and osteoarthritis. Further, we discuss the role of vascular niches during bone malignancy.

Individual functions of the histone acetyl transferases CBP and p300 in regulating the inflammatory response of synovial fibroblasts

Chromatin remodeling, and a persistent histone 3 lysine 27 acetylation (H3K27ac) in particular, are associated with a sustained inflammatory response of synovial fibroblasts (SF) in rheumatoid arthritis (RA). Here we investigated individual functions of the writers of H3K27ac marks, the homologues histone acetyl transferases (HAT) CBP and p300, in controlling the constitutive and inflammatory gene expression in RA SF. We applied a silencing strategy, followed by RNA-sequencing and pathway analysis, complemented with the treatment of SF with inhibitors targeting the HAT (C646) or bromo domains (I-CBP) of CBP and p300. We showed that CBP and p300 undertook overlapping and, in particular at gene levels, distinct regulatory functions in SF. p300 is the major HAT for H3K27ac in SF and regulated more diverse pathways than CBP. Whereas both factors regulated genes associated with extracellular matrix remodeling, adhesion and proliferation, p300 specifically controlled developmental genes associated with limb development. Silencing of CBP specifically down regulated the TNF-induced expression of interferon-signature genes. In contrast, silencing of p300 resulted in anti- and pro-inflammatory effects. Integration of data sets derived from RNA-sequencing and chromatin immunoprecipitation sequencing for H3K27ac revealed that changes in gene expression after CBP or p300 silencing could be only partially explained by changes in levels of H3K27ac. Inhibition of CBP/p300 using HAT and bromo domain inhibitors strongly mirrored effects obtained by silencing of p300, including anti- and pro-inflammatory effects, indicating that such inhibitors are not sufficient to be used as anti-inflammatory drugs.

Sparstolonin B Exerts Therapeutic Effects on Collagen-Induced Arthritis by Inhibiting the NLRP3 Inflammasome and Reducing the Activity of α1,3-Fucosyltransferase

Objective. To explore the role of α1,3-fucosyltransferase in the mediation of rheumatoid arthritic inflammation, the protective effect of Sparstolonin B on rheumatoid arthritis (RA), and the mechanisms that regulate the NLRP3 inflammasome. Methods. Forty, weighing from 260-300 g, male Sprague-Dawley rats were randomly divided into the following groups: a sham operation group (Sham group), a rheumatoid arthritis model group (RA group), an RA+Sparstolonin B treatment group (RAS group), an RA+Iguratimod group (RAI group), and an RA+SsnB+NLRP3 inflammasome activator (Nigericin) group (RASN group); ten animals were allocated to each group. We determined the arthritis index for each group of rats, and pathological changes were evaluated by hematoxylin-eosin staining. We also used ELISAs to determine the serum levels of IL-17, IL-6, TNF-α, TGF-β, IL-18, and IL-1β. TUNEL staining was used to investigate apoptosis in synovial cells. IF was used to detect the release of ROS, ASC formation, and the expression levels of FucT-V and NLRP3. Western blotting was used to detect the protein expression levels of Bc1-2, Bax, TLR4, MYD88, NF-κB, pro-caspase-1, NLRP3, FucT-V, E-Selectin, and P-Selectin. We also performed in vitro experiments with Sparstolonin B and detected changes in 1,3-fucosyltransferase activity by ELISA. The pyroptosis-related phenotype, including ASC, was identified by immunofluorescence, while levels of NLRP-3, pro-IL-1, and pro-caspase-1 were detected by western blotting. Results. Sparstolonin B was showed to alleviate joint swelling in RA rats, inhibited inflammatory cell infiltration and the release of ROS, reduced damage caused by oxidative stress, and suppressed the rate of apoptosis in synovial cells. The administration of Sparstolonin B inhibited the secretion of IL-17 from Th17 cells and triggered the secretion of TGF-β from Treg cells, thus leading to the reduced expression of TLR4, MyD88, and NF-κB, and the suppression of TNF-α secretion. Moreover, Sparstolonin B downregulated the expression of NLRP3, inhibited ASC formation in vivo and in vitro, and reduced the levels of IL-18 and IL-1β. The expression levels of FucT-V, E-Selectin, and P-Selectin were also inhibited. Interestingly, these protective effects of Sparstolonin B could be blocked in RA rats by inhibiting the activation of the NLRP3 inflammasome. Conclusion. Sparstolonin B improved inflammatory responses and oxidative stress by inhibiting the NLRP3 inflammasome, inhibiting the expression of FucT-V and downregulating the TLR4/MYD88/NF-𝜅B signaling pathway in order to rescue RA.

Functional disability is related to serum chemerin levels in rheumatoid arthritis

Adipokines, especially chemerin, can interact with cytokines and other molecules in inflammation. To date, there is insufficient information regarding a possible correlation between functional disability and chemerin and other pro-inflammatory molecules in rheumatoid arthritis (RA). To identify the association of functional disability with serum chemerin and other pro-inflammatory molecules, including other adipokines, cytokines and E-selectin, in patients with RA. Cross-sectional study. Assessment: disease activity (DAS28-ESR) and functional disability (HAQ-DI). We compared the adipokines (chemerin, leptin, adiponectin, resistin, and visfatin), cytokines (TNF-α, IL-6, IL-1β, and IL-18) and E-selectin levels between RA with functional disability and RA non-disabled patients. Of 82 patients with RA, 43 (52%) had functional disability. The RA with functional disability group had higher chemerin (140 vs. 112 ng/mL, p = 0.007) than the non-disabled RA group. Chemerin correlated with the HAQ-DI (rho = 0.27, p = 0.02) and DAS28-ESR (rho = 0.21, p = 0.05). Severe activity correlated with IL-6 (rho = 0.33, p = 0.003) and E-selectin (rho = 0.23, p = 0.03) but not with disability. No other pro-inflammatory molecules correlated with HAQ-DI. High chemerin levels were associated with functional disability in RA, whereas no other molecules correlated with loss of function. These results encourage further studies assessing new roles of chemerin as a marker of impairment in RA.

Bone Vasculature and Bone Marrow Vascular Niches in Health and Disease

Bone vasculature and bone marrow vascular niches supply oxygen, nutrients, and secrete angiocrine factors required for the survival, maintenance, and self-renewal of stem and progenitor cells. In the skeletal system, vasculature creates nurturing niches for bone and blood-forming stem cells. Blood vessels regulate hematopoiesis and drive bone formation during development, repair, and regeneration. Dysfunctional vascular niches induce skeletal aging, bone diseases, and hematological disorders. Recent cellular and molecular characterization of the bone marrow microenvironment has provided unprecedented insights into the complexity, heterogeneity, and functions of the bone vasculature and vascular niches. The bone vasculature is composed of distinct vessel subtypes that differentially regulate osteogenesis, hematopoiesis, and disease conditions in bones. Further, bone marrow vascular niches supporting stem cells are often complex microenvironments involving multiple different cell populations and vessel subtypes. This review provides an overview of the emerging vascular cell heterogeneity in bone and the new roles of the bone vasculature and associated vascular niches in health and disease. © 2020 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Adipokines and Inflammation Alter the Interaction Between Rheumatoid Arthritis Synovial Fibroblasts and Endothelial Cells

Objective: The long-distance migration of rheumatoid arthritis synovial fibroblasts (RASFs) in the severe combined immunodeficiency (SCID) mouse model of rheumatoid arthritis (RA) suggests that an interaction between RASFs and endothelial cells (EC) is critical in this process. Our objective was to assess whether immunomodulatory factors such as adipokines and antirheumatic drugs affect the adhesion of RASFs to ECs or the expression of surface molecules.

Methods: Primary ECs or human umbilical vein endothelial cell (HUVEC) and primary RASFs were stimulated with adiponectin (10 μg/mL), visfatin (100 ng/mL), and resistin (20 ng/mL) or treated with methotrexate (1.5 and 1,000 μM) and the glucocorticoids prednisolone (1 μM) and dexamethasone (1 μM), respectively. The expression of adhesion molecules was analyzed by real-time polymerase chain reaction. The interaction of both cell types was analyzed under static (cell-to-cell binding assay) and dynamic conditions (flow-adhesion assay).

Results: Under static conditions, adipokines increased mostly binding of RASFs to EC (adiponectin: 40%, visfatin: 28%, tumor necrosis factor α: 49%). Under flow conditions, visfatin increased RASF adhesion to HUVEC (e.g., 0.5 dyn/cm²: 75.2%). Reduced adhesion of RASFs to E-selectin was observed after treatment with dexamethasone (e.g., 0.9 dyn/cm²: −40%). In ECs, tumor necrosis factor α (TNF-α) increased expression of intercellular adhesion molecule 1 (20-fold) and vascular cell adhesion molecule 1 (77-fold), whereas P-selectin was downregulated after stimulation with TNF-α (−6-fold).

Conclusion: The adhesion of RASFs to EC was increased by visfatin under static and flow conditions, whereas glucocorticoids were able to decrease adhesion to E-selectin. The process of migration and adhesion of RASFs to ECs could be enhanced by adipokines via adhesion molecules and seems to be targeted by therapeutic intervention with glucocorticoids.

Effects of ticagrelor, empagliflozin and tamoxifen against experimentally-induced vascular reactivity defects in rats in vivo and in vitro

BACKGROUND

In the current investigation, the effects of the P2Y12 blocker ticagrelor, the sodium/glucose transporter-2-inhibitor empagliflozin, and the selective estrogen receptor modulator tamoxifen were examined against rheumatoid arthritis (RA)/diabetes mellitus (DM)-co-morbidity-induced defects in vascular reactivity.

METHODS

After model setting, rats were allocated into a normal control, an RA/DM-co-morbidity, and three treatment groups receiving ticagrelor, empagliflozin and tamoxifen. Aorta tissue was isolated for enzyme-linked immunosorbent assay (ELISA) and western blot estimation of the pro-inflammatory molecules angiotensin-II (Ang-II) and endothelin-1 (ET-1), the adhesion molecules P-selectin and vascular cell adhesion molecule-1 (VCAM-1), the energy preserving molecule adenosine-5'-monophosphate-activated protein kinase (AMPK), and the anti-inflammatory molecule vasoactive intestinal peptide (VIP). Estimations of endothelial nitric oxide synthase (eNOS) and matrix metalloproteinase (MMP)-2 were performed immunohistochemically, together with histopathological examination using hematoxylin and eosin and Masson trichrome staining. An in vitro study on rat aortic strips was conducted to assess aorta vasorelaxation.

RESULTS

Ticagrelor, empagliflozin and tamoxifen significantly increased aorta tissue AMPK and eNOS and decreased Ang-II, ET-1, P-selectin, VCAM-1 and VIP levels compared with RA/DM-co-morbidity, coupled with improved acetylcholine vasorelaxation in vitro.

CONCLUSION

Ticagrelor, empagliflozin and tamoxifen may correct vascular reactivity defects, where modulation of vascular AMPK, eNOS, Ang-II, ET-1, P-selectin, VCAM-1 and MMP-2 underline their protective effects.

Role of angiocrine signals in bone development, homeostasis and disease

Skeletal vasculature plays a central role in the maintenance of microenvironments for osteogenesis and haematopoiesis. In addition to supplying oxygen and nutrients, vasculature provides a number of inductive factors termed as angiocrine signals. Blood vessels drive recruitment of osteoblast precursors and bone formation during development. Angiogenesis is indispensable for bone repair and regeneration. Dysregulation of the angiocrine crosstalk is a hallmark of ageing and pathobiological conditions in the skeletal system. The skeletal vascular bed is complex, heterogeneous and characterized by distinct capillary subtypes (type H and type L), which exhibit differential expression of angiocrine factors. Furthermore, distinct blood vessel subtypes with differential angiocrine profiles differentially regulate osteogenesis and haematopoiesis, and drive disease states in the skeletal system. This review provides an overview of the role of angiocrine signals in bone during homeostasis and disease.

Nomenclature clarification: synovial fibroblasts and synovial mesenchymal stem cells

Synovial-derived cells, found in the synovial membrane of human joints, were obtained by digestion of the synovial membrane and were subsequently expanded in vitro. The identity of synovial-derived cells has long been a topic of debate. The terms "type B synoviocytes," "fibroblast-like synoviocytes (FLS)," "synovium-derived mesenchymal stem cells (MSCs)," and "synovial fibroblasts (SF)" appeared in different articles related to human synovial-derived cells in various disease models, yet they seemed to be describing the same cell type. However, to date, there is no clear standard to distinguish these terms; thus, the hypothesis that they represent the same cell type is currently inconclusive. Therefore, this review aims to clarify the similarities and differences between these terms and to diffuse the chaotic nomenclature of synovial-derived cells.

The Microbial Metabolite Trimethylamine N-Oxide Links Vascular Dysfunctions and the Autoimmune Disease Rheumatoid Arthritis

Diet and microbiota each have a direct impact on many chronic, inflammatory, and metabolic diseases. As the field develops, a new perspective is emerging. The effects of diet may depend on the microbiota composition of the intestine. A diet that is rich in choline, red meat, dairy, or egg may promote the growth, or change the composition, of microbial species. The microbiota, in turn, may produce metabolites that increase the risk of cardiovascular disease. This article reviews our current understanding of the effects of the molecule trimethylamine-N-oxide (TMAO) obtained from food or produced by the microbiota. We review the mechanisms of actions of TMAO, and studies that associate it with cardiovascular and chronic kidney diseases. We introduce a novel concept: TMAO is one among a group of selective uremic toxins that may rise to high levels in the circulation or accumulate in various organs. Based on this information, we evaluate how TMAO may harm, by exacerbating inflammation, or may protect, by attenuating amyloid formation, in autoimmune diseases such as rheumatoid arthritis.