Deconstruction of rheumatoid arthritis synovium defines inflammatory subtypes

Rheumatoid arthritis is a prototypical autoimmune disease that causes joint inflammation and destruction1. There is currently no cure for rheumatoid arthritis, and the effectiveness of treatments varies across patients, suggesting an undefined pathogenic diversity1,2. Here, to deconstruct the cell states and pathways that characterize this pathogenic heterogeneity, we profiled the full spectrum of cells in inflamed synovium from patients with rheumatoid arthritis. We used multi-modal single-cell RNA-sequencing and surface protein data coupled with histology of synovial tissue from 79 donors to build single-cell atlas of rheumatoid arthritis synovial tissue that includes more than 314,000 cells. We stratified tissues into six groups, referred to as cell-type abundance phenotypes (CTAPs), each characterized by selectively enriched cell states. These CTAPs demonstrate the diversity of synovial inflammation in rheumatoid arthritis, ranging from samples enriched for T and B cells to those largely lacking lymphocytes. Disease-relevant cell states, cytokines, risk genes, histology and serology metrics are associated with particular CTAPs. CTAPs are dynamic and can predict treatment response, highlighting the clinical utility of classifying rheumatoid arthritis synovial phenotypes. This comprehensive atlas and molecular, tissue-based stratification of rheumatoid arthritis synovial tissue reveal new insights into rheumatoid arthritis pathology and heterogeneity that could inform novel targeted treatments.

Differential DNA Methylation of Networked Signaling, Transcriptional, Innate and Adaptive Immunity, and Osteoclastogenesis Genes and Pathways in Gout

OBJECTIVE

In gout, autoinflammatory responses to urate crystals promote acute arthritis flares, but the pathogeneses of tophi, chronic synovitis, and erosion are less well understood. Defining the pathways of epigenomic immunity training can reveal novel pathogenetic factors and biomarkers. The present study was undertaken to seminally probe differential DNA methylation patterns utilizing epigenome-wide analyses in patients with gout.

METHODS

Peripheral blood mononuclear cells (PBMCs) were obtained from a San Diego cohort of patients with gout (n = 16) and individually matched healthy controls (n = 14). PBMC methylome data were processed with ChAMP package in R. ENCODE data and Taiji data analysis software were used to analyze transcription factor (TF)-gene networks. As an independent validation cohort, whole blood DNA samples from New Zealand Māori subjects (n = 13 patients with gout, n = 16 control subjects without gout) were analyzed.

RESULTS

Differentially methylated loci clearly separated gout patients from controls, as determined by hierarchical clustering and principal components analyses. IL23R, which mediates granuloma formation and cell invasion, was identified as one of the multiple differentially methylated gout risk genes. Epigenome-wide analyses revealed differential methylome pathway enrichment for B and T cell receptor signaling, Th17 cell differentiation and interleukin-17 signaling, convergent longevity regulation, circadian entrainment, and AMP-activated protein kinase signaling, which are pathways that impact inflammation via insulin-like growth factor 1 receptor, phosphatidylinositol 3-kinase/Akt, NF-κB, mechanistic target of rapamycin signaling, and autophagy. The gout cohorts overlapped for 37 (52.9%) of the 70 TFs with hypomethylated sequence enrichment and for 30 (78.9%) of the 38 enriched KEGG pathways identified via TFs. Evidence of shared differentially methylated gout TF-gene networks, including the NF-κB activation-limiting TFs MEF2C and NFATC2, pointed to osteoclast differentiation as the most strongly weighted differentially methylated pathway that overlapped in both gout cohorts.

CONCLUSION

These findings of differential DNA methylation of networked signaling, transcriptional, innate and adaptive immunity, and osteoclastogenesis genes and pathways suggest that they could serve as novel therapeutic targets in the management of flares, tophi, chronic synovitis, and bone erosion in patients with gout.

Salivary Gland Ultrasonography as a Diagnostic Tool for Secondary Sjögren Syndrome in Rheumatoid Arthritis

Objective.

To assess salivary gland ultrasonography (US) as a diagnostic tool for secondary Sjögren syndrome (sSS) in patients with rheumatoid arthritis (RA).

Methods.

Salivary gland US images from 30 patients with RA were graded using a validated semiquantitative scoring system. Sicca symptoms, oral health, and RA disease activity were assessed.

Results.

US changes consistent with SS were found in 40% of patients. Patients with higher US scores had more sicca symptoms as well as higher RA activity and poorer oral health.

Conclusion.

Salivary gland US may aid the diagnosis of sSS in patients with RA.

Point-of-care musculoskeletal ultrasound is critical for the diagnosis of hemarthroses, inflammation and soft tissue abnormalities in adult patients with painful haemophilic arthropathy

We previously demonstrated in adult patients with haemophilia (PWH) that hemarthrosis is present in only ~1/3rd of acutely painful joints by using point-of-care-musculoskeletal ultrasound (MSKUS). Therefore, other unrecognized tissue abnormalities must contribute to pain. Using high resolution MSKUS, employing grey scale and power Doppler, we sought to retrospectively (i) investigate soft tissue abnormalities in painful haemophilic joints and (ii) to determine to what extent MSKUS findings, functional or radiographic joint scores correlate with biomarkers of inflammation in PWH. Findings were correlated with Hemophilia Joint Health Scores (HJHS), Pettersson scores, high sensitivity C-reactive protein and von Willebrand factor activity and antigen levels. A total of 65 MSKUS examinations for acute and chronic joint pains were performed for 34 adult haemophilia patients, mostly for chronic joint pains (72.3%). The most prominent findings (66.5%) pertained to inflammatory soft tissue changes including synovitis, tendinitis, enthesitis, bursitis and fat pad inflammation. Effusions were present in 55.5% and 46.8% of MSKUS performed for acute and chronic pain, respectively. Of those, 90.0% were bloody during acute and 47.6% during persistent pains. While inflammatory biomarkers correlated well with overall HJHS and total Pettersson scores (P < 0.05), they did not differ between those patients with synovitis and those without. MSKUS is emerging as an important modality to diagnose treatable musculoskeletal abnormalities contributing to pain in haemophilic arthropathy, and therefore seems critical for a personalized approach to haemophilia care. The role of biomarkers in this setting remains less clear and requires further investigation.

Rapid musculoskeletal ultrasound for painful episodes in adult haemophilia patients

Little objective information exists about musculoskeletal bleeding patterns in haemophilic arthropathy. Bleeding is assumed to be the cause of painful joints or muscles. Clotting factor treatment is provided empirically, but often does not alleviate pain. We hypothesized that perception of pain aetiology is unreliable, and introduced point-of-care high-resolution musculoskeletal ultrasound (MSKUS) to differentiate intra-articular bleeds vs. joint inflammation, and intra-muscle bleeds vs. other regional pain syndromes. To assess painful musculoskeletal episodes in adult haemophiliacs, we used rapid MSKUS, employing grey scale and power Doppler examination. Forty episodes in 30 adult haemophiliacs were evaluated. Thirty three of the 40 episodes were patient-reported as 'bleeding', five as 'arthritis-type' pain and two as 'undecided'. Of the 33 bleeding reports, only 12 were confirmed by MSKUS; the other episodes revealed other pathology. In contrast, three of five perceived arthritis flares were reclassified as bleeds. Similarly, physician assessment was incorrect in 18 of 40 instances. Swelling and warmth were present in approximately half of confirmed bleeding and non-bleeding episodes, and therefore not useful clinically. Few of the painful episodes were symptom controlled at the time of MSKUS. Management changed based on objective imaging findings in >70% of episodes, which resulted in symptom improvement >60% of the time. Significant discrepancies exist between MSKUS findings and patient/physician-perceived pain classification as bleeding or other musculoskeletal symptoms. Current practice of prescribing clotting factor or conservative measures based on pain perception seems inadequate and suggests that point-of-care imaging should be included into modern haemophilia care.

Use of methotrexate in patients with psoriatic arthritis

Despite a paucity of high quality clinical data, methotrexate (MTX) remains one of the most commonly used medications in the treatment of patients with psoriatic arthritis (PsA). This report addresses mechanistic rationale, available clinical evidence, safety considerations, and a potential research agenda regarding the use of MTX in the management of PsA.

Cartilage oligomeric matrix protein (COMP) is modified by intra-articular liposomal clodronate in an experimental model of arthritis

OBJECTIVE

High-dose liposomal bisphosphonates exert apoptotic effects. This work studies the chondroprotective and anti-inflammatory properties of intra-articularly administered low-dose, non-cytotoxic liposomal clodronate.

METHODS

Antigen induced arthritis in rabbits was treated with intra-articular injections of liposomal clodronate. Drug effects on cartilage oligomeric matrix protein COMP was assessed using immunohistochemistry and morphometry of synovial membrane and hyaline articular cartilage.

RESULTS

COMP remained close to normal in liposomal clodronate treated superficial articular cartilage compared to a significant loss of COMP in arthritis controls treated with empty liposomes. The middle and deep layers of the hyaline articular cartilage were characterized by highly increased COMP expression in liposomal clodronate treated AIA joints compared to controls. In contrast to cartilage, synovial COMP expression was slightly decreased as a result of liposomal clodronate treatment.

CONCLUSION

Low-dose, non-cytotoxic liposomal clodronate exerts a dichotomous effect on synovial membrane and articular cartilage COMP in the AIA model. COMP is a useful inflammation marker in the synovial tissue, but it also contributes to the structural integrity of the hyaline articular cartilage forming bridges between type II and IX collagens. Enhancement of COMP in clodronate treated AIA cartilage suggests a chondroprotective and anti-inflammatory effect in the inflammatorily damaged and mechanically strained cartilage.

Vascular damage and lack of angiogenesis in systemic sclerosis skin

The aim of this study was to analyse microvascular damage and compensatory angiogenesis in skin from patients with systemic sclerosis (SSc) compared with systemic lupus erythematosus (SLE), Raynaud's phenomenon (RP) and healthy controls. Immunohistochemistry was used for skin biopsies (9 SSc, 10 SLE, 9 RP and 12 healthy controls) using von Willebrand factor and beta3 integrin subunit specific antibodies, TechMate immunostaining robot and biotin-streptavidin protocol. In the early stages of SSc, vWF was found in the perivascular space and interstitial matrix in papillary but not in the reticular dermis, in particular around small oedematous blood vessels infiltrated by mononuclear cells. The extravascular release of vWF in SSc specimens was associated with weak or even a total lack of immunoreactivity within the associated endothelial cells. Late stages of SSc were characterised by loss of the dermal papillae, subepidermal fibrosis, hypovascularity and strong endothelial vWF expression without extravascular leakage. In all SSc patients studied only a few vascular profiles were weakly immunostained for beta3 integrin subunit. This work demonstrates that vWF is not only released into the systemic circulation, but is also leaked to the perivascular space/matrix. This local release and deposition of vWF is probably a sensitive and early marker of microvascular involvement in SSc pathogenesis. Local vWF release may play a role in platelet adhesion, aggregation, thrombogenesis and dermal connective tissue remodelling. In spite of some attempts towards compensatory angiogenesis in SSc, as evidenced by beta3 integrin subunit expression, it was evident that the angiogenic response was not able to prevent the development of hypovascularity during the advanced stages of the disease.

Regulation of macrophage activation

IFN-gamma rapidly primes the macrophage via JAK1/2-STAT1 pathway so that it can subsequently undergo a slower classical type 1 activation upon exposure to T helper (Th)1 cytokines such as IFNgamma or other activators, including tumor necrosis factor and lipopolysaccharide, e.g. in intracellular killing of phagocytosed Mycobacterium tuberculosis. If instead it is driven by Th2 cytokines interleukin (IL)-4 and IL-13, it undergoes alternate type 2 activation, which enhances endocytotic antigen uptake and presentation, mast cell and eosinophil involvement and type 2 granuloma formation, e.g. in response to parasitic and extracellular pathogens. Particle-induced macrophage activation was shown to differ from classical and alternate activation, showing in DNA microarray experiments (complete linkage/ Euclidean distance metric analysis) upregulation of nonsecreted structural/signaling molecules and lack of secreted proinflammatory cyto- and chemokines. The switch-off (deactivation) of already activated macrophages is an active, controlled process in which IL-10 and corticosteroids play important roles and to which 15dPGJ2, PGA1/2 and vasoactive intestinal peptide often contribute.

Increased but imbalanced expression of VEGF and its receptors has no positive effect on angiogenesis in systemic sclerosis skin

OBJECTIVE

To investigate the expression of vascular endothelial growth factor (VEGF) and its vascular and lymphatic receptors in skin in systemic sclerosis (SSc) compared to systemic lupus erythematosus (SLE), Raynaud's phenomenon (RP) and normal healthy control skin.

METHODS

Staining was performed using rabbit anti-human antibodies in DAKO TechMate Horizon staining robot programmed for the biotin-streptavidin protocol.

RESULTS

VEGF was sporadically and weakly expressed in normal skin, but in spite of vascular damage in diseased skin, VEGF expression was only slightly upregulated. In contrast, its vascular receptors VEGFR-1 (Flt-1) and VEGFR-2 (Flk-1), were clearly upregulated. Finally, the lymphatic VEGFR-3 (Flt-4) receptor was also upregulated in diseased skin and ectopically expressed also in blood vessels. Negative staining and positive sample controls confirmed the specificity of the staining.

CONCLUSION

The imbalanced expression of VEGF and its vascular receptors suggest that the compensatory efforts to angiogenesis fail in SSc, in part due to insufficient local production of VEGF, which was low compared to VEGFR expression. This is compatible with the recent observations on the lack of alpha V beta 3+ newly formed blood vessels in SSc skin. Since microvascular angiogenic stimuli normally induce first VEGF and then VEGFR, these findings also suggest that the angiogenic cascade is turned on, but there is a defect in the finalization of its effects. Normalization of angiogenic cascade in SSc could provide a future therapeutic target.

Effects of low-dose, noncytotoxic, intraarticular liposomal clodronate on development of erosions and proteoglycan loss in established antigen-induced arthritis in rabbits

OBJECTIVE

To assess the clinical and histologic effects of an intraarticular application of low-dose (non-cytotoxic) liposomal clodronate in established antigen-induced monarthritis (AIA) in rabbits.

METHODS

AIA was monitored by assessments of joint swelling, C-reactive protein levels, and radiographic changes in 17 NZW rabbits for 8 weeks during the course of weekly intraarticular injections of liposomal clodronate (0.145 mg/injection, low dose) or "empty" liposomes. The contralateral knee was injected with liposome buffer alone as the control. End-point analyses included macroscopic joint examination, immuno- and TUNEL staining, Safranin O staining/microspectrophotometry, and tumor necrosis factor alpha (TNFalpha) convertase enzyme (TACE) inhibition assay.

RESULTS

Liposomal clodronate-treated rabbits showed a reduction and delay in joint swelling during the first 3 injections. Expression of matrix-bound (solubilized) TNFalpha, lining cell hyperplasia, and levels of RAM-11+ macrophages were low in the synovium of the liposomal clodronate treatment group, but the proportion of apoptotic lining cells was not affected. The radiologic score was low at the end of weeks 2 and 4, but at 8 weeks, no difference, compared with controls, was found in pannus formation or in the extent of joint erosion; also, joint swelling was higher than before initiation of treatment. Injections of liposomal clodronate prevented cartilage proteoglycan loss, which was significant in the superficial zone only. TACE activity was not inhibited by clodronate.

CONCLUSION

Liposomal clodronate had temporary antiinflammatory and antierosive effects on established AIA in rabbits. Over the long-term, the loss of cartilage proteoglycans was halted. This observed treatment effect may be related to the inhibition of TNFalpha production and processing in the synovium.

The in vivo expression of the collagenolytic matrix metalloproteinases (MMP-2, -8, -13, and -14) and matrilysin (MMP-7) in adult and localized juvenile periodontitis

Periodontal inflammation is characterized by irreversible degradation of periodontal ligament collagen fibers leading to loss of tooth attachment. Cultured gingival keratinocytes and fibroblasts express, in vitro, various matrix metalloproteinases (MMPs) which can degrade fibrillar collagens. We hypothesized that several MMPs are also synthesized in vivo by sulcular epithelium, and analyzed the collagenolytic MMPs (MMP-2, -8, -13, and -14) and matrilysin (MMP-7) in gingival tissue specimens and gingival crevicular fluid from adult and localized juvenile periodontitis patients by in situ hybridization, immunohistochemistry, and Western immunoblotting. MMP-2, -7, -8, and -13 were expressed in gingival sulcular epithelium. MMP-7 and -13 were also located in fibroblasts and macrophages, and MMP-8 in neutrophils. MMP-8- and -13-positive cells/mm2 were higher in periodontitis gingiva when compared with healthy control tissue (p < 0.01). In periodontal diseases, gingival sulcular epithelium expresses several, rather than a single, collagenolytic MMPs, and this proteolytic cascade is evidently responsible for the tissue destruction characteristic of adult and juvenile periodontitis.

Collagenase-3 (MMP-13) and its activators in rheumatoid arthritis: localization in the pannus-hard tissue junction and inhibition by alendronate

The hypothesis of the present work was that the pannus tissue overlying the articular hard tissues has an aggressive phenotype and contains the newly discovered collagenase-3 and its endogenous inducers and activators. We therefore analyzed the eventual presence of collagenase-3 and its regulation at the pannus-cartilage junction. Collagenase-3 mRNA (in situ hybridization) and enzyme protein (ABC and immunofluorescence staining) were found in the pannocytes in the pannus-hard tissue junction. Inflammatory round cells associated with the critical interface contained TNF-alpha and IL-1beta. These cytokines induced collagenase-3 secretion in cultured rheumatoid synovial fibroblasts. Procollagenase-3 activators, stromelysin-1, 72 kDa type IV collagenase/gelatinase and membrane-type 1-MMP, were also found in the pannus-hard tissue junction. Active collagenase-3 was inhibited with alendronate (IC50 = 500-750 microM). Collagenase-3, due to its substrate profile and local synthesis in a milieu favoring its activation, might play a major role in the degradation of cartilage type II and bone type I collagens. Alendronate, at concentrations attainable in vivo, is able to inhibit collagenase-3. This might offer an option to control collagenase-3-mediated tissue destruction in rheumatoid arthritis.

A comparative quantitative morphometric study of cell apoptosis in synovial membranes in psoriatic, reactive and rheumatoid arthritis

OBJECTIVES

Inflammatory arthritides/synovitides such as psoriatic (PsA), reactive (ReA) and rheumatoid (RA) arthritis share numerous immunopathological features, but develop different patterns of joint involvement. To investigate whether distinctive cell apoptosis may play a role in this context, we have assessed synovial cell apoptosis in situ in PsA and ReA, and compared it with RA and 'non-inflammatory' controls.

METHODS

TdT-mediated dUTP nick end-labelling (TUNEL) of DNA breaks complemented immunoperoxidase staining for CD68 or LCA as the specific cell markers.

RESULTS

The proportion of apoptotic synovial lining cells was high in PsA, ReA and RA compared to values in controls (P < 0.05). No differences existed between these inflammatory arthritides in numbers or type of apoptotic lining cells. In RA, however, in contrast to PsA and ReA, apoptotic lining cells were clustered or, in a small subset of samples, were very low in number. Prominent apoptosis of inflammatory cells in the sublining in ReA has accounted for higher overall apoptotic cell numbers in synovial stroma (sublining + perivascular inflammatory cell infiltrates) in this condition than in RA or PsA (P < 0.05).

CONCLUSIONS

No disease-specific pattern in the phenotype of apoptotic synovial lining cells could be suggested in any of the inflammatory arthritides studied. However, topological differences in the lining and quantitative differences in the inflammatory cell apoptosis in synovial stroma may in part explain the occurrence of the prominent synovial lining cell hyperplasia distinguishing RA from ReA and PsA. On the other hand, relatively frequent inflammatory cell apoptosis may contribute both to the downregulation of synovial inflammation and to the control of synovial lining hyperplasia in ReA.

Expression of stem cell factor (SCF) and SCF receptor (c-kit) in synovial membrane in arthritis: correlation with synovial mast cell hyperplasia and inflammation

OBJECTIVE

Stem cell factor (SCF), the ligand for the SCF receptor (c-kit) expressed on precursors and mature mast cells (MC), is a major agonist for human MC (e.g., SCF induces MC development, chemotaxis, activation, proliferation of MC precursors, mediates MC adhesion, and changes MC releasability). We investigated expression of SCF and c-kit in synovial membrane with particular reference to the mechanism of local MC hyperplasia and inflammation in arthritis.

METHODS

We conducted single and double labeling immunohistochemistry (ABC, APAAP, indirect immunofluorescence techniques) with antibodies to SCF, c-kit, MC tryptase, Ki-67 antigen (marker for proliferating cells), and CD68 (monocyte/macrophage marker). Synovial specimens analyzed were from 31 patients: traumatic arthritis (TrA, n=9), osteoarthritis (OA, n=12), and rheumatoid arthritis (RA, n=10). Control experiments were performed on human lung, skin, and buccal mucosa tissues, on the HMC-1 mast cell line, and isolated lung MC. Morphometry was performed by computerized image analysis.

RESULTS

Synovial c-kit expression was found to be restricted to MC, whereas SCF is detected in synovial lining cells, stromal fibroblasts, monocyte/macrophages, endothelial cells, and in vascular basement membranes. SCF staining was localized to MC as well, but it was not possible to specify whether this represents SCF produced by or bound (via c-kit) to MC. In inflamed synovial membranes/areas, SCF was found to be redistributed into the extracellular matrix. Redistribution of SCF was accompanied by degranulation and/or accumulation of c-kit+ MC, the hyperplasia of which correlated positively with histologic inflammation/inflammatory cell densities, but did not appear to involve MC proliferation in situ. These findings appeared to be common for all the conditions (TrA, OA, RA) studied.

CONCLUSION

In addition to the demonstration/characterization of SCF and c-kit protein expression in human synovium, results of this study suggest the hypothesis that, in arthritis, local mobilization of SCF may play a role in the development of synovial MC hyperplasia without inducing in situ proliferation of MC, and that the synovial SCF/MC c-kit system may contribute to the local nonspecific inflammatory response/arthritic flares in TrA, OA, and RA.

New collagenolytic enzymes/cascade identified at the pannus-hard tissue junction in rheumatoid arthritis: destruction from above

Our aim was to investigate the collagenolytic potential and localization of matrix metalloproteinase-2 (MMP-2) in relation to its regulatory proteins membrane type MT1-MMP and tissue inhibitor of metalloproteinases-2 (TIMP-2) in rheumatoid arthritis (RA). For this purpose, we have used purification of MMP-2, MMP-8, MMP-9 and interstitial type I, II and III collagens; SDS-PAGE/densitometric collagenase activity assay; zymography; Western blotting; reverse transcriptase polymerase chain reaction; in situ hybridization; and immunofluorescence, ABC, ABC-APAAP double immunostainings. MMP-2 degraded human type II collagen almost as effectively as MMP-8, whereas MMP-9 did not cleave type II collagen. In synovial tissue, MT1-MMP, TIMP-2 and MMP-2 were found in synovial lining in fibroblast- and macrophage-like cells, in stromal cells and in vascular endothelium. MT1-MMP, TIMP-2 and MMP-2 were strongly expressed in the pannocytes of the invasive pannus at the interface, but staining was weak and/or there were few positive cells both "above" and "below" the soft-to-hard tissue (cartilage and/or bone) interface. Rheumatoid synovial tissue extract contained proteolytically active 62/59 kDa MMP-2 and 43 kDa MT1-MMP, but no free TIMP-2. These results indicate that components of the ternary MT1-MMP/TIMP-2/MMP-2 complex are coexpressed in the normal synovial lining and in its pathological extension on the hyaline articular cartilage. MMP-2 may participate in the remodeling of the normal lining and also seems to be localized/focalized to pannocytes at a site critical for tissue destruction in arthritis.

Interleukin-11 (IL-11) in aseptic loosening of total hip replacement (THR)

The chronic inflammatory response to abrasion particles from total hip replacement (THR) is believed to cause osteolysis and to contribute to prosthetic loosening. The expression of interleukin-11(IL-11) and its major cellular sources in the interface and pseudocapsular tissues obtained from total hip revisions performed for aseptic loosening were investigated. The avidin-biotin-peroxidase complex (ABC) and alkaline phosphatase-anti-alkaline phosphatase (APAAP) methods were used for staining and VIDAS image analysis for quantification. IL-11 was found in the interface and pseudocapsular tissues in the aseptic loosening of THR. IL-11 containing cells were more numerous in the interface (760 +/- 171 cells) and pseudocapsular tissues (684 +/- 171 cells) than in the control synovial tissue (235 +/- 68 cells). Because IL-11 is an important component of cytokine network mediating osteoblast-osteoclast communication in normal and pathological bone remodeling, the current findings suggest that IL-11 may contribute to periprosthetic osteolysis and to the loosening of THR.

Matrix metalloproteinase (MMP)-9 type IV collagenase/gelatinase implicated in the pathogenesis of Sjögren's syndrome

Type IV collagenases/gelatinases (matrix metalloproteinases MMP-2 and MMP-9) in labial salivary glands (LSG) and saliva in Sjögren's syndrome (SS) and healthy controls were studied. Zymograms and Western blots disclosed that SS saliva contained 92/82 kD MMP-9/type IV collagenase duplex. Specific activity measurement disclosed 53.1+/-9.8 U/mg protein MMP-9 in SS compared to 16.5+/-2.6 U/mg in healthy controls (p=0.01). MMP-2 did not differ between SS and controls. In SS salivary glands, MMP-2 and MMP-9 were also expressed, in addition to stromal fibroblasts and occasional infiltrating neutrophils, respectively, in acinar end piece cells. In addition, an effective proMMP-9 activator, human trypsin-2 (also known as tumor-associated trypsin-2 or TAT-2), was found in acinar end piece cells and in saliva. Interestingly, proteolytically processed MMP-9 was found in saliva (vide supra), and in vivo activated MMP-9 was significantly higher in SS than in controls (p=0.002). LSGs, particularly in SS, were characterized ultrastructurally by areas containing small cytoplasmic vesicles in the basal parts of the epithelial cells associated with areas of disordered and thickened basal lamina. Based on our results, we conclude here that SS saliva contains increased concentrations of MMP-9, which is of glandular origin in part. Pro MMP-9 is to a large extent proteolytically activated. This is probably mediated by the most potent pro MMP-9 activator found in vivo thus far, namely trypsin-2. Therefore, the MMP 9/trypsin-2 cascade may be responsible for the increased remodelling and/or structural destruction of the basement membrane scaffolding in salivary glands in SS. Due to the role of basal lamina as an important molecular sieve and extracellular matrix-cell signal, these pathological changes may contribute to the pathogenesis of the syndrome.

High levels of expression of collagenase-3 (MMP-13) in pathological conditions associated with a foreign-body reaction

A foreign-body-type host response can contribute to the induction and release of collagenolytic tissue-destructive enzymes of pathogenetic significance. Our aim was to analyse collagenase-3 in two conditions with putative involvement of foreign-body reactions. Synovial membrane-like tissue samples were obtained from cases of aseptic loosening of a total hip replacement (THR) and osteoarthritis (OA). The reverse transcription polymerase chain reaction (RT-PCR) disclosed that all the samples from patients contained collagenase-3 mRNA compared with only three out of ten control samples. The identity of the RT-PCR amplification product was confirmed by nucleotide sequencing. Immunohistochemical staining showed that collagenase-3 was present in endothelial cells, macrophages and fibroblasts, including those found in the synovial lining. This finding was confirmed by avidin-biotin-peroxidase complex-alkaline phosphatase-anti-alkaline phosphatase double staining and the specificity of the staining by antigen preabsorption using recombinant human collagenase-3. Collagenase-3 was released into the extracellular space and thus found in the synovial fluid in all patient samples as shown by Western blotting. The similar extent of collagenase-3 expression in aseptic loosening and OA compared with the low expression in control synovial membrane suggests involvement of a similar, foreign-body-based pathogenetic component in both. Comparative analysis of collagenase-3 and of foreign particles indicates that paracrine factors rather than phagocytosis per se are responsible for the induction of collagenase-3. We suggest that due to its localisation and substrate specificity, collagenase-3 may play a significant pathogenetic role in accelerating tissue destruction in OA and in aseptic loosening of a THR.

Activation of periprosthetic connective tissue in aseptic loosening of total hip replacements

In aseptic loosening of initially well inserted total hip prostheses, implant wear debris and cyclic mechanical loading lead to a foreign body type of chronic inflammatory reaction, then to osteolysis, and finally to loosening of the implant. In the present work the reactive and adaptive changes of the periprosthetic tissues and pseudojoint were characterized by analysis of the local cell proliferation. Immunohistochemical demonstration of proliferating cells was performed by application of affinity purified rabbit antihuman Ki-67 antibodies to periprosthetic tissues obtained from revision operations for loose total hip prostheses. The fibrous areas and, in particular, the cell rich, vascular areas of the interface tissue (between implant and bone) and the pseudocapsule around aseptically loosened implants contained higher numbers of proliferating cells than the tissues around well fixed implants. In addition, the pseudosynovial lining occasionally contained some Ki-67 positive proliferating cells. Somewhat surprisingly, proliferating vascular endothelial cells were relatively rare. These findings suggest that reactive (interface tissues) and adaptive (pseudojoint and capsule formed around the artificial joint) tissue changes in loosening total hip prostheses comprise proliferation of local fibroblastlike cells. It is concluded that periprosthetic tissues of the loosened total hip prosthesis represent activated mesenchymal tissue.

Synovial lining, endothelial and inflammatory mononuclear cell proliferation in synovial membranes in psoriatic and reactive arthritis: a comparative quantitative morphometric study

The extent of synovial cell proliferation in situ and its relationship to the destructive potential of rheumatoid arthritis (RA) is a matter of continuing debate. Notably, the situation has not been elucidated in other inflammatory arthritides [i.e. reactive (ReA) and psoriatic (PsA)], which, although they share some histopathological similarities with RA, develop different patterns of joint involvement. In order to estimate the proliferation of synovial cells in situ in PsA and ReA, and to compare this with RA and with 'non-inflammatory' joint lesions, we have utilized immunostaining of the Ki-67 antigen complemented with Ki-67/CD68 or Ki-67/leucocyte common antigen (LCA, clones 2B11 and PD7/26) double stainings to assess the extent of mononuclear inflammatory cell proliferation. Synovial samples analysed were from 33 patients: RA (n = 8), PsA (n = 13), ReA (n = 6) and six 'non-inflammatory controls' (degenerative or traumatic joint lesions). Thickening of the synovial lining (in particular in RA) and perivascular accumulations of mononuclear inflammatory cells, predominantly lymphocytes, were characteristic features in all synovitides. In contrast to the thickened avascular synovial lining in RA, in 5/13 cases with PsA, blood vessels were observed in the lining. The percentage of lining cells expressing Ki-67 antigen was higher in RA (median = 4.7, interquartile range [Q3-Q1] = 3.9, mean [95% CI] = 3.5 [1.7-5.2], P = 0.0063), PsA (median = 1.2, [Q3-Q1] = 1.9, mean [95% CI] = 1.6 [0.7-2.5], P = 0.007) and ReA (median = 1.4, [Q3-Q1] = 2.3, mean [95% CI] = 1.6 [0.1-3.1], P = 0.0235) than in controls (median = 0.1, [Q3-Q1] = 0.45, mean [95% CI] = 0.2 [0.07-0.5]). In this respect, the differences between different forms of the inflammatory arthritides were not statistically significant (P > 0.05). In RA, PsA and ReA, the percentage of labelled cells in the inflammatory mononuclear cell-rich areas was higher than in controls. The percentage of proliferating endothelial cells was also significantly higher in RA, PsA and ReA than in controls. However, in RA, endothelial expression of Ki-67 antigen was often seen in small blood vessels, whereas in PsA, Ki-67 antigen was preferably expressed in the medium to large blood vessels. Synovial lining cells of the monocyte/macrophage lineage (type A synoviocytes), but not stromal monocytes, demonstrated modest proliferation in situ. These results indicate that although proliferation of synovial lining fibroblasts is a prominent feature in RA, the extents to which this, or in situ proliferation of lymphocytes, contribute to the histopathology of PsA, ReA and RA are comparable. Vascular involvement is suggested by the proliferation of endothelial cells in RA, PsA and ReA in an overlapping manner, but, based on topological differences, such a response may represent diverse pathological features, such as angiogenesis, vascular enlargement and reparative responses to injury.

Matrix metalloproteinase 13 (collagenase 3) in human rheumatoid synovium

OBJECTIVE

To show the eventual presence and extent of production of matrix metalloproteinase 13 (MMP-13, or collagenase 3) in rheumatoid synovial tissue samples and extracts, and to assess the inhibition characteristics of recombinant MMP-13.

METHODS

Immunohistochemical avidin-biotin-peroxidase complex staining/morphometry was used to analyze MMP-13-positive cells in situ. Neutral salt extraction of synovial tissue, electrophoresis of the extract in different buffer systems, and Western blotting were also used. The inhibitory properties of doxycycline, clodronate, pamidronate, and D-penicillamine for recombinant enzyme were determined with a soluble type II collagen assay.

RESULTS

MMP-13 was detected in fibroblast- and macrophage-like mononuclear cells in the synovial lining and stroma and in vascular endothelial cells. The overall expression of MMP-13 in these cells in the synovial stroma was high in rheumatoid arthritis (86 +/- 12%) compared with osteoarthritis (17 +/- 5%) patient samples (P = 0.0027). In a high-pH native electrophoresis gel, immunoreactivity to anti-MMP-1 and anti-MMP-13 were clearly separated, with anti-MMP-13-immunoreactive material migrating faster than anti-MMP-1-immunoreactive material. Finally, in contrast to MMP-1 and MMP-8, MMP-13 was found to be relatively resistant to the inhibitory effects of doxycycline and clodronate in vitro.

CONCLUSION

Due to its localization in synovial tissue, its substrate profile, increased expression, and relative resistance to known MMP inhibitors, MMP-13 is suggested to play a major role in the pathogenesis of tissue destruction in rheumatoid arthritis.

Complement in acute and chronic arthritides: assessment of C3c, C9, and protectin (CD59) in synovial membrane

OBJECTIVES

To investigate the role of complement cascade induced damage and protection against it in acute arthritides compared to rheumatoid arthritis and other chronic joint derangements.

METHODS

C3c, C9, and protectin (CD59) were examined by avidin-biotin-peroxidase complex staining.

RESULTS

Marked deposits of C3c and C9 were found in synovial vasculature and intercellular matrix of the lining in rheumatoid arthritis and in acute arthritides (including bacterial, reactive, and osteoarthritis flare up). Furthermore, protectin was not visible in synovial lining cells and was relatively weakly expressed in stromal and endothelial cells in rheumatoid arthritis; also in acute arthritides protectin expression was weak. In contrast, C3c and C9 deposits were not found in chronic conditions associated with degenerative diseases (osteoarthritis and osteochondritis dissecans) or mechanical causes (patellar luxation and a ruptured meniscus), in which also the protectin expression was prominent in synovial lining, endothelial and some stromal cells.

CONCLUSIONS

Activation of the complement in rheumatoid arthritis and in acute arthritides seems to be associated with a decreased protection of synovial cells against cellular effects and lysis mediated by membrane attack complex.

Aberrant vascularity and von Willebrand factor distribution in inflamed synovial membrane

OBJECTIVE

Von Willebrand factor (vWF) is an adhesive glycoprotein produced and secreted constitutively by endothelial cells. vWF is released upon endothelial stimulation and/or vascular injury, and mediates adhesion and aggregation of platelets. Our aim was to quantify synovial vasculature and to evaluate vWF distribution in situ in synovial membranes in various arthritides.

METHODS

Immunohistochemical staining of vWF in synovial membranes from patients with rheumatoid arthritis (RA) (N = 9), psoriatic (PsA) (N = 3), and reactive (ReA) (N = 4) arthritis, and from 6 noninflammatory controls: osteoarthritis (N = 1), chondromatosis (N = 1), meniscus lesion (N = 4). Morphometric assessments were performed with an image analyzer.

RESULTS

In RA, mean number of blood vessels/mm2 in the thickened synovium was relatively low (131 +/- 57 vs control 257 +/- 115, p = 0.0137, ReA 346 +/- 83, p = 0.0002, PsA 434 +/- 157, p = 0.0127). In particular, the superficial layer, corresponding to the thickness of normal synovial membrane (i.e., 56 +/- 5 microns), was sparsely vascularized (70 +/- 37 in the superficial vs 219 +/- 104 in the deeper layer, p = 0.0047). Synovial thickening was not seen in ReA and PsA. In accordance with its constitutive metabolism, vWF was found in the endothelial cells, inside the blood vessels, and in the subendothelium. In addition, RA was characterized by weak endothelial immunoreactivity and perivascular vWF. In ReA, perivascular vWF staining was visible in areas of inflammatory cell infiltrates.

CONCLUSION

Morphometric findings indicate decreased vascularization of the superficial synovial membrane in RA. Second, vWF may play a role in the inflammatory/reparative responses in synovium in RA and ReA, which were characterized by vascular stimulation/injury and abnormal vWF distribution.

Tumor necrosis factor-alpha (TNF-alpha) in loosening of total hip replacement (THR)

OBJECTIVE

The initially well-fixed implants of total hip replacement (THR) are in the long-term subject to aseptic loosening. Many cytokines can contribute to osteolysis due to osteoclast recruitment and/or activation. However, in this respect tumor necrosis factor-alpha (TNF-alpha) plays a pivotal role, because it upregulates interleukin-1 and 6 and granulocyte-macrophage colony stimulating factor. The aim of this study was to assess the eventual presence, cellular localization and extent of expression of TNF-alpha in the synovial-like membrane at the implant or at the cement to bone interface compared to control synovial membrane.

METHODS

Twenty samples from the synovial-like membrane of the periprosthetic tissues were compared to control samples. TNF-alpha containing cells were visualized using an avidin-biotin-peroxidase complex (ABC) method and analyzed by light microscopy, double labelling and image analysis.

RESULTS

TNF-alpha was found in the periprosthetic tissues in fibroblasts and vascular endothelial cells, but mainly in the macrophages was it found to coincide with areas containing implant-derived debris. TNF-alpha containing cells were more numerous in the synovial-like membrane in the interface tissue from the proximal stem area (2816 +/- 318 cells) than in the control synovial membrane (565 +/- 93 cells, p < 0.01). Interestingly, similarly high TNF-alpha expression (3452 +/- 582 cells) was also seen in the synovial-like membrane of the pseudocapsule.

CONCLUSION

These findings suggest that the foreign body-type host reaction caused by THR is characterized by the high expression of TNF-alpha. Because such expression occurred in the interface tissue between the implant and surrounding bone, TNF-alpha, due to its pivotal direct and indirect role in the activation and recruitment of osteoclasts, may contribute to periprosthetic osteolysis and to the loosening of THR.

Periprosthetic microvasculature in loosening of total hip replacement

This study was performed to quantitate vascularity in periprosthetic tissues of loose total hip replacements (THRs), because most likely revascularization and endothelial cells are important for implant osseointegration and loosening. Interface and pseudocapsular tissue samples obtained from loose THRs were stained with an immunohistochemical labelling (ABC technique) for von Willebrand factor. Non-inflammatory synovial samples served as controls. The results were quantitated by morphometry using the Kontron image analysis system. Evaluation of the mean endothelial index (EI; positively stained area micron/mm2 of tissue) revealed that in the control samples synovium was better vascularized than was the case in the cellular areas of the periprosthetic pseudocapsule (P = 0.0008) and interface (P = 0.0004) of loose THRs. There was no significant difference between mean EI of cellular areas in the interface and that of the pseudocapsule (P = 0.24). In the interface the vascularity was irregular. Vascular injury and decreased blood supply seem to occur at the implant-host interface, which may be one of the reasons for insufficient implant osseointegration and loosening.

Mast cells in loosening of totally replaced hips

This study evaluated mast cells in tissue around loose total hip implants. Interface and pseudocapsular tissues were obtained from 6 patients with a loose hip prosthesis. Mast cells were labeled with monoclonal mouse antihuman antibodies against tryptase and chymase in avidin-biotin-peroxidase complex staining and were quantitated morphometrically by means of a semiautomatic Kontron image analyzer. Almost all mast cells in situ were chymase-positive and tryptase-positive connective tissue cells. The mean number of such cells per mm2 of tissue increased in this rank order: interface (9.98 +/- 5.03 cells) < pseudocapsule (15.85 +/- 4.99 cells) < control knee synovium (25.08 +/- 8.64 cells). Mast cells in periprosthetic tissue, in contrast to normal knee synovial tissue, exhibited granule release. Mast cells around loose hip prostheses appeared to be activated by connective tissue mast cells. These were found in diminished numbers and in a degranulated state in the interface tissue between implant and bone. Mast cell activation in loco may thus lead to significant local production and/or release of proinflammatory mast cell mediators. Prevention of mast cell activation (degranulation) could prove useful in the postponement of loosening of the totally replaced hip.