Analysis of vascular gene expression in arthritic synovium by laser-mediated microdissection

Synovial Tissue Heterogeneity in Rheumatoid Arthritis and Changes With Biologic and Targeted Synthetic Therapies to Inform Stratified Therapy

The treatment of rheumatoid arthritis (RA) has been transformed with the introduction of biologic disease modifying anti-rheumatic drugs (bDMARD) and more recently, targeted synthetic DMARD (tsDMARD) therapies in the form of janus-kinase inhibitors. Nevertheless, response to these agents varies such that a trial and error approach is adopted; leading to poor patient quality of life, and long-term outcomes. There is thus an urgent need to identify effective biomarkers to guide treatment selection. A wealth of research has been invested in this field but with minimal progress. Increasingly recognized is the importance of evaluating synovial tissue, the primary site of RA, as opposed to peripheral blood-based investigation. In this mini-review, we summarize the literature supporting synovial tissue heterogeneity, the conceptual basis for stratified therapy. This includes recognition of distinct synovial pathobiological subtypes and associated molecular pathways. We also review synovial tissue studies that have been conducted to evaluate the effect of individual bDMARD and tsDMARD on the cellular and molecular characteristics, with a view to identifying tissue predictors of response. Initial observations are being brought into the clinical trial landscape with stratified biopsy trials to validate toward implementation. Furthermore, development of tissue based omics technology holds still more promise in advancing our understanding of disease processes and guiding future drug selection.

Tetraspanin CD82 affects migration, attachment and invasion of rheumatoid arthritis synovial fibroblasts

Tetraspanins function as membrane adaptors altering cell-cell fusion, antigen presentation, receptor-mediated signal transduction and cell motility via interaction with membrane proteins including other tetraspanins and adhesion molecules such as integrins. CD82 is expressed in several malignant cells and well described as tumour metastasis suppressor. Rheumatoid arthritis (RA) is based on persistent synovial inflammation and joint destruction driven to a large extent by transformed-appearing activated synovial fibroblasts (SF) with an increased migratory potential.

OBJECTIVE

CD82 is upregulated in RA synovial fibroblasts (RASF) compared with osteoarthritis (OA) SF as well as within RA compared with OA synovial lining layer (LL) and the role of CD82 in RASF was evaluated.

METHODS

CD82 and integrin immunofluorescence was performed. Lentiviral CD82 overexpression and siRNA-mediated knockdown was confirmed (realtime-PCR, Western blot, immunocytochemistry). RASF migration (Boyden chamber, scrape assay), attachment towards plastic/Matrigel, RASF-binding to endothelial cells (EC) and CD82 expression during long-term invasion in the SCID-mouse-model were evaluated.

RESULTS

CD82 was induced by proinflammatory stimuli in SF. In RA-synovium, CD82 was expressed in RASF close to blood vessels, LL, sites of cartilage invasion and colocalised with distinct integrins involved in tumour metastasis suppression but also in RA-synovium by RASF. CD82 overexpression led to reduced RASF migration, cell-matrix and RASF-EC adhesion. Reduced CD82 expression (observed in the sublining) increased RASF migration and matrix adhesion whereas RASF-EC-interaction was reduced. In SCID mice, the presence of CD82 on cartilage-invading RASF was confirmed.

CONCLUSION

CD82 could contribute to RASF migration to sites of inflammation and tissue damage, where CD82 keeps aggressive RASF on site.

Myeloid dendritic cells stimulated by thymic stromal lymphopoietin promote Th2 immune responses and the pathogenesis of oral lichen planus

Oral lichen planus (OLP) is a chronic inflammatory disease characterized by subepithelial T-cell infiltration. Recent studies reported that specific T helper (Th) subsets, especially Th2 cells, are involved in the pathogenesis of OLP. Thymic stromal lymphopoietin (TSLP) is mainly secreted by epithelial cells and potently activates myeloid dendritic cells (mDCs) to induce Th2-mediated inflammation. Here, we investigated the expression of TSLP and related molecules in OLP. Buccal mucosa specimens from patients with OLP, hyperkeratosis, and ulcer were analyzed by immunohistochemistry for expression of TSLP, its receptor (TSLPR), and inflammatory cells. TSLP was detected in/around the epithelium of patients with OLP and hyperkeratosis, whereas TSLPR, CD11c (mDC), and GATA3 (Th2) were strongly expressed in the subepithelial layer only in OLP patients. Double immunofluorescence staining showed that TSLPR expression mainly co-localized with CD11c. Moreover, the number of CD11c- and GATA-3 positive cells was correlated in OLP patients. In lesions selectively extracted by laser microdissection, the mRNA expression of Th2 (IL-4, MDC, TARC, GATA3)- and Th17 (IL-17, RORγt)-related molecules in OLP patients was significantly higher than in other groups. These results suggest that CD11c⁺ mDCs expressing TSLPR contribute to aberrant Th2 immune responses and the pathogenesis of OLP via TSLP stimulation.

Angiopoietin-like 4 is over-expressed in rheumatoid arthritis patients: association with pathological bone resorption

INTRODUCTION

Osteoclasts are responsible for the bone loss associated with rheumatoid arthritis (RA). The secreted adipokine angiopoietin-like 4 (ANGPTL4) specifically increases osteoclast-mediated bone resorption. We have investigated expression of ANGPTL4 and its regulatory transcription factor, hypoxia-inducible factor-1 alpha (HIF-1α), in osteoclasts and other cells within rheumatoid synovium. We have also examined whether circulating levels of ANGPTL4 differ in RA patients compared with that in normal controls or patients with osteoarthritis (OA).

RESULTS

Immunohistochemical analysis revealed that bone-apposing osteoclasts within the rheumatoid synovium express both ANGPTL4 and HIF-1α. ANGPTL4 was also strongly expressed in synovial lining cells, endothelial cells, stromal cells, CD68+ macrophages and plasma cells within RA synovium. Little ANGPTL4 was evident in normal synovial tissue. This reflected the over-expression of HIF-1α in rheumatoid versus normal synovial tissue. The concentration of ANGPTL4 was higher in both the serum and the synovial fluid of RA patients than in patients with OA or normal controls. High serum ANGPTL4 associated with elevated levels of the serum marker of bone resorption, receptor activator for nuclear factor κB ligand (RANKL).

CONCLUSIONS

Over-expression of ANGPTL4 in multiple cell types within the rheumatoid synovium potentially provides a local pool of ANGPTL4 to stimulate osteoclast-mediated bone resorption in RA. Additionally, correlation of high serum ANGPTL4 with circulating RANKL suggests that ANGPTL4 may represent a novel marker for bone destruction in RA.

CD82 restrains pathological angiogenesis by altering lipid raft clustering and CD44 trafficking in endothelial cells

BACKGROUND

Angiogenesis is crucial for many pathological processes and becomes a therapeutic strategy against diseases ranging from inflammation to cancer. The regulatory mechanism of angiogenesis remains unclear. Although tetraspanin CD82 is widely expressed in various endothelial cells (ECs), its vascular function is unknown.

METHODS AND RESULTS

Angiogenesis was examined in Cd82-null mice with in vivo and ex vivo morphogenesis assays. Cellular functions, molecular interactions, and signaling were analyzed in Cd82-null ECs. Angiogenic responses to various stimuli became markedly increased upon Cd82 ablation. Major changes in Cd82-null ECs were enhanced migration and invasion, likely resulting from the upregulated expression of cell adhesion molecules such as CD44 and integrins at the cell surface and subsequently elevated outside-in signaling. Gangliosides, lipid raft clustering, and CD44-membrane microdomain interactions were increased in the plasma membrane of Cd82-null ECs, leading to less clathrin-independent endocytosis and then more surface presence of CD44.

CONCLUSIONS

Our study reveals that CD82 restrains pathological angiogenesis by inhibiting EC movement, that lipid raft clustering and cell adhesion molecule trafficking modulate angiogenic potential, that transmembrane protein modulates lipid rafts, and that the perturbation of CD82-ganglioside-CD44 signaling attenuates pathological angiogenesis.

The potential role of angiogenic factors in rheumatoid arthritis

Angiogenesis is an important phenomenon in the pathogenesis of some diseases, such as numerous types of tumors and autoimmunity, and also a number of soluble and cell-bound factors may stimulate neovascularization in inflammatory reaction processes. Here, by highlighting the significance of angiogenesis reaction in rheumatoid arthritis (RA), we will mainly focus on the role of various growth factors, cytokines, enzymes, cells, hypoxic conditions and transcription factors in the angiogenic process and we will then explain some therapeutic strategies based on blockage of angiogenesis and modification of the vascular pathology in RA.

Decreased semaphorin3A expression correlates with disease activity and histological features of rheumatoid arthritis

Background

Rheumatoid arthritis (RA) is an autoimmune disease of which the pathogenetic mechanisms are not fully understood. Semaphorin3A (Sema3A) has an immune regulatory role. Neuropilin1 (NRP1), the primary receptor for Sema3A, is also a receptor for vascular endothelial growth factor 165 (VEGF₁₆₅). It has been shown that Sema3A competitively antagonizes VEGF165 signaling. This study investigated whether Sema3A is expressed in synovial tissues, and is associated with disease activity and the histological features of synovial tissues from RA patients.

Methods

Human synovial tissues samples were obtained from RA and osteoarthritis (OA) patients. Disease activity of RA patients was calculated using the 28-joint Disease Activity Score based on C-reactive protein (DAS28-CRP). The histological features of RA synovial tissues were evaluated using Rooney’s inflammation scoring system. The localization of Sema3A, VEGF₁₆₅ and NRP1 positive cells was immunohistochemically determined in synovial tissues. Expression levels of Sema3A, VEGF-A and NRP1 mRNA were determined using quantitative real-time polymerase chain reaction (qPCR).

Results

In OA specimens, Sema3A, VEGF₁₆₅ and NRP1 proteins were expressed in the synovial lining and inflammatory cells beneath the lining. Immunohistochemistry revealed the protein expression of Sema3A in synovial lining cells was decreased in RA tissues compared with OA samples. qPCR analysis demonstrated a significant reduction of Sema3A mRNA levels in RA synovial tissue samples than in OA and a significant correlation of the ratio of Sema3A/VEGF-A mRNA expression levels with DAS28-CRP (R = −0.449, p = 0.013). Sema3A mRNA levels also correlated with Rooney’s inflammation score, especially in perivascular infiltrates of lymphocytes (R = −0.506, p = 0.004), focal aggregates of lymphocytes (R = −0.501, p = 0.005) and diffuse infiltrates of lymphocytes (R = −0.536, p = 0.002).

Conclusions

Reduction of Sema3A expression in RA synovial tissues may contribute to pathogenesis of RA.

Dkk-1 promotes angiogenic responses and cartilage matrix proteinase secretion in synovial fibroblasts from osteoarthritic joints

OBJECTIVE

Synovial hypervascularity is a prominent pathologic feature in osteoarthritic (OA) joints. Wnt inhibitor Dkk-1 contributes to joint remodeling. We undertook this study to investigate whether Dkk-1 regulates cartilage destruction activities in OA synovial fibroblasts.

METHODS

Synovial tissues were harvested from knees of patients with OA and from injured knees of non-OA patients who underwent arthroscopy. Expression of Dkk-1, angiogenic factors (stromal cell-derived factor 1 and colony-stimulating factor 1), and cartilage proteinases (ADAMTS-5 and matrix metalloproteinase 3 [MMP-3]) as well as vascularity in synovium and synovial fluid were quantified using enzyme-linked immunosorbent assay, reverse transcription-polymerase chain reaction, and histomorphometry. Synovial fibroblasts were treated with interleukin-1β (IL-1β), anti-Dkk-1 antibody, and RNA interference to characterize their angiogenic activity. Rats with OA knees were administered Dkk-1 antisense oligonucleotide to verify synovial angiogenesis and cartilage integrity.

RESULTS

OA synovium exhibited increased vascularity and expression of angiogenic factors and proteinases in association with up-regulated Dkk-1 levels. Neutralizing Dkk-1 reduced the inhibitory effects of OA synovial fluid on aggrecan expression in chondrocyte cultures. IL-1β induction of Dkk-1 increased expression of hypoxia-inducible factor 1α (HIF-1α), angiogenic factors, ADAMTS-5, and MMP-3 in synovial fibroblasts and promoted angiogenesis in vascular endothelial cells. Knockdown of HIF-1α decreased Dkk-1 enhancement of angiogenic factor expression. Stabilization of glycogen synthase kinase 3β phosphorylated at Ser(9) , β-catenin, T cell factor 4, and ERK signaling attenuated Dkk-1 up-regulation of angiogenic factor and proteinase expression in synovial fibroblasts. In vivo, Dkk-1 interference reduced the expression of angiogenic factors and proteinases and ameliorated synovial vascularity and cartilage deterioration in knees of rats with OA.

CONCLUSION

Dkk-1 promoted angiogenic and cartilage degradation activities in synovial fibroblasts, which accelerated synovial angiogenesis and cartilage destruction. Dkk-1 blockade has therapeutic potential for reducing OA-induced synovitis and joint deterioration.

Selective localization of T helper subsets in labial salivary glands from primary Sjögren's syndrome patients

The aim of this study was to investigate the initiation and progression of autoimmune damage in the lesions of labial salivary glands (LSGs) from primary Sjögren's syndrome (SS) patients by examining the selective localization of T helper (Th) subsets such as Th1, Th2, Th17 regulatory T cells (T_regs) and follicular T helper cells (Tfh). The expression of cytokines and transcription factors associated with these Th subsets in the LSGs from 54 SS patients and 16 healthy controls was examined using real-time polymerase chain reaction (PCR) and immunostaining. Additionally, infiltrating lymphocytes without germinal centre (GC^-) and with GC (GC⁺) in the LSGs specimens from eight SS patients were extracted selectively by laser capture microdissection (LCM). The mRNA expression of these molecules was compared between the two sample groups of GC^- and GC⁺ by real-time PCR. The mRNA expression of cytokines and transcription factors of all T helper (Th) subsets in the LSGs from the SS patients was increased significantly in comparison with controls. In LSGs from the SS patients, Th2 and Tfh was associated closely with strong lymphocytic infiltration; however, Th1, Th17 and T_regs was not. In the selectively extracted lesions of LSGs, Th1 and Th17-related molecules were detected strongly in the GC^-, while Th2 and Tfh-related molecules were detected in the GC⁺. In contrast, no significant association with strong lymphocytic infiltration was observed in T_reg-related molecules. These results indicate that SS has selective localization of Th subsets such as Th1, Th2, Th17 and Tfh in the LSGs, which is associated closely with disease severity and/or status. SS might be initiated by Th1 and Th17 cells, and then progressed by Th2 and Tfh cells via GC formation.

Action mechanisms of du-huo-ji-sheng-tang on cartilage degradation in a rabbit model of osteoarthritis

Du-Huo-Ji-Sheng-Tang (DHJST) is a traditional Chinese herbal medicine used to treat osteoarthritis. In the present study, the therapeutic effect of DHJST on cartilage degradation in a rabbit model of osteoarthritis was investigated. In the knee joints of rabbits, anterior cruciate ligament transection (ACLT) was performed to induce experimental osteoarthritis. At the end of the sixth week, 30 rabbits with ACLT were divided into six groups, control group, DHJST group and Osaminethacine (OSA) group, which were followed for another 4 weeks. The other three groups of rabbits with ACLT were untreated with DHJST or OSA, which were sacrificed after 6 weeks, and served as 6-week time point controls. Results indicated that at the end of the sixth week after surgery, there was a significantly histological degeneration in the control group compared with the normal group. In the control group, the mean score for histological degeneration were further increases at 10th week, and there was a significantly lower mean score for histological degeneration in the DHJST group compared with the control group. To research the potential mechanism, the expression level of VEGF and HIF-1α were detected. The expression of VEGF mRNA and HIF-1α mRNA are low in normal group, while the activities increase gradually in the control group. However, compared to that of the same time point model group, activity of VEGF and HIF-1α decreased significantly in DHJST group. In conclusion, DHJST exerts significant therapeutic effect on osteoarthritis rabbits, and mechanisms are associated with inhibition of VEGF and HIF-1α expression.

Blood-induced joint disease: the pathophysiology of hemophilic arthropathy

Arthropathy is a frequent and serious complication of repeated joint bleeding in patients with hemophilia, resulting in pain, deformity, and disability. Although the pathogenesis of hemophilic arthropathy has not been fully elucidated, it appears to have similarities with the degenerative joint damage that occurs in osteoarthritis and the inflammatory processes associated with rheumatoid arthritis. This article reviews the potential actions of various blood constituents on joint components that culminate in the development of hemophilic arthropathy.

Inhibitor of DNA binding/differentiation 2 induced by hypoxia promotes synovial fibroblast-dependent osteoclastogenesis

OBJECTIVE

To map hypoxic areas in arthritic synovium and to establish the relevance of low oxygen levels to the phenotype of synovial fibroblasts, with special focus on bone degradation.

METHODS

To analyze the distribution of hypoxia in arthritic joints, the hypoxia marker EF5 was administered to mice with collagen-induced arthritis (CIA). To evaluate the effect of hypoxia on rheumatoid arthritis synovial fibroblasts (RASFs), reverse suppression subtractive hybridization and complementary DNA array were used. Real-time polymerase chain reaction, Western blotting, and immunohistochemistry were used to evaluate the expression of inhibitor of DNA binding/differentiation 2 (ID-2). To investigate the function of ID-2 in RASFs, cells were transfected either with ID-2 vector or with ID-2-specific small interfering RNA.

RESULTS

EF5 staining showed the presence of hypoxia in arthritic joints, particularly at sites of synovial invasion into bone. Differential expression analysis revealed that ID-2 was strongly induced by hypoxia in RASFs. Immunohistochemical analysis of CIA mouse synovium and human RA synovium showed a strong expression of ID-2 by RASFs at sites of synovial invasion into bone. Overexpression of ID-2 in RASFs significantly induced the expression of several factors promoting osteoclastogenesis. The biologic relevance of the potent osteoclastogenesis-promoting effects was shown by coculture assays of ID-2-overexpressing RASFs with bone marrow cells, leading to an increased differentiation of osteoclasts from bone marrow precursors.

CONCLUSION

The data show that hypoxic conditions are present at sites of inflammation and synovial invasion into bone in arthritic synovium. Hypoxia-induced ID-2 may contribute to joint destruction in RA patients by promoting synovial fibroblast-dependent osteoclastogenesis.

Laser microdissection-based analysis of cytokine balance in the kidneys of patients with lupus nephritis

To determine the cytokine balance in patients with lupus nephritis (LN), we analysed kidney-infiltrating T cells. Renal biopsy samples from 15 systemic lupus erythematosus (SLE) patients were used. In accordance with the classification of International Society of Nephrology/Renal Pathology Society, they were categorized into Class III, Class III+V (Class III-predominant group, n = 4), Class IV, Class IV+V (Class IV-predominant group, n = 7) and Class V (n = 4) groups. The single-cell samples of both the glomelular and interstitial infiltrating cells were captured by laser-microdissection. The glomerular and interstitial infiltrating T cells produced interleukin (IL)-2, IL-4, IL-10, IL-13 and IL-17 cytokines in the Class III-predominant, Class IV-predominant and Class V groups. Interferon-gamma was detected only in the glomeruli of the Class III-predominant and Class V group samples. The expression level of IL-17 was correlated closely with clinical parameters such as haematuria, blood urea nitrogen level, SLE Disease Activity Index scores in both glomeruli and interstitium, urine protein level in glomeruli and serum creatinine and creatinine clearance levels in interstitium. This suggests that the glomerular infiltrating T cells might act as T helper type 1 (Th1), Th2 and Th17 cells while the interstitial infiltrating T cells, act as Th2 and Th17 cells in the Class III-predominant and Class V groups. In contrast, both the glomerular and interstitial infiltrating T cells might act as Th2 and Th17 cells in the Class IV-predominant group. The cytokine balances may be dependent upon the classification of renal pathology, and IL-17 might play a critical role in SLE development.

Identification of pro-angiogenic markers in blood vessels from stroked-affected brain tissue using laser-capture microdissection

Background

Angiogenesis correlates with patient survival following acute ischaemic stroke, and survival of neurons is greatest in tissue undergoing angiogenesis. Angiogenesis is critical for the development of new microvessels and leads to re-formation of collateral circulation, reperfusion, enhanced neuronal survival and improved recovery.

Results

Here, we have isolated active (CD105/Flt-1 positive) and inactive (CD105/Flt-1 minus (n=5) micro-vessel rich-regions from stroke-affected and contralateral tissue of patients using laser-capture micro-dissection. Areas were compared for pro- and anti-angiogenic gene expression using targeted TaqMan microfluidity cards containing 46 genes and real-time PCR. Further analysis of key gene de-regulation was performed by immunohistochemistry to define localization and expression patterns of identified markers and de novo synthesis by human brain microvessel endothelial cells (HBMEC) was examined following oxygen-glucose deprivation (OGD). Our data revealed that seven pro-angiogenic genes were notably up-regulated in CD105 positive microvessel rich regions. These were, beta-catenin, neural cell adhesion molecule (NRCAM), matrix metalloproteinase-2 (MMP-2), tissue inhibitor of matrix metalloproteinase-1 (TIMP-1), hepatocyte growth factor-alpha (HGF-alpha), monocyte chemottractant protein-1 (MCP-1) and and Tie-2 as well as c-kit. Immunohistochemistry demonstrated strong staining of MMP-2, HGF-alpha, MCP-1 and Tie-2 in stroke-associated regions of active remodeling in association with CD105 positive staining. In vitro, OGD stimulated production of Tie-2, MCP-1 and MMP-2 in HBMEC, demonstrated a de novo response to hypoxia.

Conclusion

In this work we have identified concurrent activation of key angiogenic molecules associated with endothelial cell migration, differentiation and tube-formation, vessel stabilization and stem cell homing mechanisms in areas of revascularization. Therapeutic stimulation of these processes in all areas of damaged tissue might improve morbidity and mortality from stroke.

Hypoxia-inducible factor mediates hypoxic and tumor necrosis factor alpha-induced increases in tumor necrosis factor-alpha converting enzyme/ADAM17 expression by synovial cells

Chronic hypoxia and inflammatory cytokines are hallmarks of inflammatory joint diseases like rheumatoid arthritis (RA), suggesting a link between this microenvironment and central pathological events. Because TACE/ADAM17 is the predominant protease catalyzing the release of tumor necrosis factor alpha (TNFalpha), a cytokine that triggers a cascade of events leading to RA, we examined the regulation of this metalloprotease in response to hypoxia and TNFalpha itself. We report that low oxygen concentrations and TNFalpha enhance TACE mRNA levels in synovial cells through direct binding of hypoxia-inducible factor-1 (HIF-1) to the 5' promoter region. This is associated with elevated TACE activity as shown by the increase in TNFalpha shedding rate. By the use of HIF-1-deficient cells and by obliterating NF-kappaB activation, it was determined that the hypoxic TACE response is mediated by HIF-1 signaling, whereas the regulation by TNFalpha also requires NF-kappaB activation. As a support for the in vivo relevance of the HIF-1 axis for TACE regulation, immunohistological analysis of TACE and HIF-1 expression in RA synovium indicates that TACE is up-regulated in both fibroblast- and macrophage-like synovial cells where it localizes with elevated expression of both HIF-1 and TNFalpha. These findings suggest a mechanism by which TACE is increased in RA-affected joints. They also provide novel mechanistic clues on the influence of the hypoxic and inflammatory microenvironment on joint diseases.

Laser-mediated microdissection for analysis of gene expression in synovial tissue

In experimental rheumatology, transcriptomics is one of the most important methods for investigating the pathogenesis of diseases. The biological material of most studies on rheumatoid arthritis has been bulk rheumatoid synovial tissues, but they are not suitable because they consist of several kinds of cells or structures. Laser-mediated microdissection (LMM) is a useful tool for isolating particular cells from tissue specimen to assess the functions of each cell. The LMM system employs a combination of a microscope and a laser-beam generator to cut out target areas on cryosections. Tissue compartments or even a single viable cell can be isolated using a non-focused laser beam without direct contact to avoid contamination, and this process is called laser pressure catapulting. An ultraviolet-A laser enables target cells to be procured without any influence on the surrounding. This technique has already been used in several studies in rheumatology, and its validity has been confirmed. Combined with other new techniques such as real-time quantitative polymerase chain reaction or microarray analysis, LMM is becoming more important in the analysis of gene expression in rheumatology.