Protective Effect of Bovine Milk Extracellular Vesicles on Alveolar Bone Loss

SCOPE

Bovine milk extracellular vesicles (MEVs) have demonstrated therapeutic potential in regulating bone cell activity. However, the outcome of their use on alveolar bone loss has not yet been demonstrated.

METHODS AND RESULTS

This study evaluates the effect of oral administration of MEVs on ovariectomized (OVX) mice. There is a reduced height of the alveolar bone crest in OVX mice by MEVs treatment, but the alveolar bone parameters are not altered. OVX mice are then submitted to a force-induced bone remodeling model by orthodontic tooth movement (OTM). MEVs-treated mice have markedly less bone remodeling movement, unlike the untreated OVX mice. Also, OVX mice treated with MEVs show an increased number of osteoblasts and osteocytes associated with higher sclerostin expression and reduce osteoclasts in the alveolar bone. Although the treatment with MEVs in OVX mice does not show differences in root structure in OTM, few odontoclasts are observed in the dental roots of OVX-treated mice. Compared to untreated mice, maxillary and systemic RANKL/OPG ratios are reduced in OVX mice treated with MEVs.

CONCLUSION

Treatment with MEVs results in positive bone cell balance in the alveolar bone and dental roots, indicating its beneficial potential in treating alveolar bone loss in the nutritional context.

Profiling of plasma extracellular vesicles identifies proteins that strongly associate with patient's global assessment of disease activity in rheumatoid arthritis

Background

Rheumatoid arthritis (RA) is an autoimmune disease characterized by chronic synovial inflammation and cartilage/bone damage. Intercellular messengers such as IL-1 and TNF play a crucial role in the pathophysiology of RA but have limited diagnostic and prognostic values. Therefore, we assessed whether the protein content of the recently discovered extracellular vesicles (EVs), which have gained attention in the pathogenesis of RA, correlates with disease activity parameters in RA patients.

Methods

We identified and quantified proteins in plasma-derived EVs (pEVs), isolated by size exclusion chromatography from 17 RA patients by mass spectrophotometry (MS). Quantified protein levels were correlated with laboratory and clinical parameters and the patient's own global assessment of their disease activity (PGA-VAS). In a second MS run, the pEV proteins of nine other RA patients were quantified and compared to those from nine healthy controls (HC).

Results

No differences were observed in the concentration, size, and protein content of pEVs from RA patients. Proteomics revealed >95% overlapping proteins in RA-pEVs, compared to HC-pEVs (data are available via ProteomeXchange with identifier PXD046058). Remarkably, in both runs, the level of far more RA-pEV proteins correlated positively to PGA-VAS than to either clinical or laboratory parameters. Interestingly, all observed PGA-VAS positively correlated RA-pEV proteins were associated with the actin-cytoskeleton linker proteins, ezrin, and moesin.

Conclusion

Our observation suggests that PGA-VAS (loss of vitality) may have a different underlying pathological mechanism in RA, possibly related to enhanced muscle actin-cytoskeleton activity. Furthermore, our study contributes to the growing awareness and evidence that pEVs contain valuable biomarkers for diseases, with added value for RA patients.

Polyethylene glycol precipitation is an efficient method to obtain extracellular vesicle-depleted fetal bovine serum

Mesenchymal stromal/stem cell derived-extracellular vesicles (MSC-EVs) have gained interest as drug delivery nanoparticles, having immunoregulatory and potentiating tissue repair property. To maintain growth of MSCs and obtain pure MSC-derived EVs, the culture media should contain fetal bovine serum (FBS) devoid of EVs, as the presence of FBS EVs confounds the properties of MSC-EVs. Therefore, we tested three methods: 18h ultracentrifugation (UC) and ultrafiltration (UF), which are common FBS EV depletion methods in current MSC-EV research, and polyethylene glycol (PEG) precipitation to obtain three EV depleted FBS (EVdFBS) batches, and compared them to FBS and commercial (Com) EVdFBS on human adipose stem cell (hADSC) growth, differentiation, enrichment of EVs in hADSC supernatant and their biological function on collagen metabolism. Our comparative study showed UC and UF vary in terms of depletion efficiency and do not completely deplete EVs and affects the growth-promoting quality of FBS. Specifically, FBS EV depletion was comparable between PEG (95.6%) and UF (96.6%) but less by UC (82%), as compared to FBS. FBS protein loss was markedly different among PEG (47%), UF (87%), and UC (51%), implying the ratio of EV depletion over protein loss was PEG (2.03), UF (1.11), and UC (1.61). A significant decrease of TGFβ/Smad signaling, involving in MSC growth and physiology, was observed by UF. After 96 hours of exposure to 5% FBS or 5% four different EVdFBS cell growth media, the osteogenesis ability of hADSCs was not impaired but slightly lower mRNA expression level of Col2a observed in EVdFBS media during chondrogenesis. In consistent with low confluency of hADSCs observed by optical microscope, cell proliferation in response to 5% UF EVdFBS media was inhibited significantly. Importantly, more and purer ADSCs EVs were obtained from ADSCs cultured in 5% PEG EVdFBS media, and they retained bioactive as they upregulated the expression of Col1a1, TIMP1 of human knee synovial fibroblast. Taken together, this study showed that PEG precipitation is the most efficient method to obtain EV depleted FBS for growth of MSCs, and to obtain MSC EVs with minimal FBS EV contamination.

Innate Immunity and Sex: Distinct Inflammatory Profiles Associated with Murine Pain in Acute Synovitis

Joint pain severity in arthritic diseases differs between sexes and is often more pronounced in women. This disparity is thought to stem from biological mechanisms, particularly innate immunity, yet the understanding of sex-specific differences in arthritic pain remains incomplete. This study aims to investigate these disparities using an innate immunity-driven inflammation model induced by intra-articular injections of Streptococcus Cell Wall fragments to mimic both acute and pre-sensitized joint conditions. Nociceptive behavior was evaluated via gait analysis and static weight-bearing, and inflammation was evaluated via joint histology and the synovial gene expression involved in immune response. Although acute inflammation and pain severity were comparable between sexes, distinct associations between synovial inflammatory gene expression and static nociceptive behavior emerged. These associations delineated sex-specific relationships with pain, highlighting differential gene interactions (Il6 versus Cybb on day 1 and Cyba/Gas6 versus Nos2 on day 8) between sexes. In conclusion, our study found that, despite similar pain severity between sexes, the association of inflammatory synovial genes revealed sex-specific differences in the molecular inflammatory mechanisms underlying pain. These findings suggest a path towards more personalized treatment strategies for pain management in arthritis and other inflammatory joint diseases.

Flood Control: How Milk-Derived Extracellular Vesicles Can Help to Improve the Intestinal Barrier Function and Break the Gut-Joint Axis in Rheumatoid Arthritis

Many studies provided compelling evidence that extracellular vesicles (EVs) are involved in the regulation of the immune response, acting as both enhancers and dampeners of the immune system, depending on the source and type of vesicle. Research, including ours, has shown anti-inflammatory effects of milk-derived EVs, using human breast milk as well as bovine colostrum and store-bought pasteurized cow milk, in in vitro systems as well as therapeutically in animal models. Although it is not completely elucidated which proteins and miRNAs within the milk-derived EVs contribute to these immunosuppressive capacities, one proposed mechanism of action of the EVs is via the modulation of the crosstalk between the (intestinal) microbiome and their host health. There is increasing awareness that the gut plays an important role in many inflammatory diseases. Enhanced intestinal leakiness, dysbiosis of the gut microbiome, and bowel inflammation are not only associated with intestinal diseases like colitis and Crohn's disease, but also characteristic for systemic inflammatory diseases such as lupus, multiple sclerosis, and rheumatoid arthritis (RA). Strategies to target the gut, and especially its microbiome, are under investigation and hold a promise as a therapeutic intervention for these diseases. The use of milk-derived EVs, either as stand-alone drug or as a drug carrier, is often suggested in recent years. Several research groups have studied the tolerance and safety of using milk-derived EVs in animal models. Due to its composition, milk-derived EVs are highly biocompatible and have limited immunogenicity even cross species. Furthermore, it has been demonstrated that milk-derived EVs, when taken up in the gastro-intestinal tract, stay intact after absorption, indicating excellent stability. These characteristics make milk-derived EVs very suitable as drug carriers, but also by themselves, these EVs already have a substantial immunoregulatory function, and even without loading, these vesicles can act as therapeutics. In this review, we will address the immunomodulating capacity of milk-derived EVs and discuss their potential as therapy for RA patients.

Review criteria

The search terms "extracellular vesicles", "exosomes", "microvesicles", "rheumatoid arthritis", "gut-joint axis", "milk", and "experimental arthritis" were used. English-language full text papers (published between 1980 and 2021) were identified from PubMed and Google Scholar databases. The reference list for each paper was further searched to identify additional relevant articles.

Extracellular vesicles regulate purinergic signaling and epithelial sodium channel expression in renal collecting duct cells

Purinergic signaling regulates several renal physiological and pathophysiological processes. Extracellular vesicles (EVs) are nanoparticles released by most cell types, which, in non-renal tissues, modulate purinergic signaling. The aim of this study was to investigate the effect of EVs from renal proximal tubule (HK2) and collecting duct cells (HCD) on intra- and intersegment modulation of extracellular ATP levels, the underlying molecular mechanisms, and the impact on the expression of the alpha subunit of the epithelial sodium channel (αENaC). HK2 cells were exposed to HK2 EVs, while HCD cells were exposed to HK2 and HCD EVs. Extracellular ATP levels and αENaC expression were measured by chemiluminescence and qRT-PCR, respectively. ATPases in EV populations were identified by mass spectrometry. The effect of aldosterone was assessed using EVs from aldosterone-treated cells and urinary EVs (uEVs) from primary aldosteronism (PA) patients. HK2 EVs downregulated ectonucleoside-triphosphate-diphosphohydrolase-1 (ENTPD1) expression, increased extracellular ATP and downregulated αENaC expression in HCD cells. ENTPD1 downregulation could be attributed to increased miR-205-3p and miR-505 levels. Conversely, HCD EVs decreased extracellular ATP levels and upregulated αENaC expression in HCD cells, probably due to enrichment of 14-3-3 isoforms with ATPase activity. Pretreatment of donor cells with aldosterone or exposure to uEVs from PA patients enhanced the effects on extracellular ATP and αENaC expression. We demonstrated inter- and intrasegment modulation of renal purinergic signaling by EVs. Our findings postulate EVs as carriers of information along the renal tubules, whereby processes affecting EV release and/or cargo may impact on purinergically regulated processes.

Comparing Approaches to Normalize, Quantify, and Characterize Urinary Extracellular Vesicles

BACKGROUND

Urinary extracellular vesicles (uEVs) are a promising source for biomarker discovery, but optimal approaches for normalization, quantification, and characterization in spot urines are unclear.

METHODS

Urine samples were analyzed in a water-loading study, from healthy subjects and patients with kidney disease. Urine particles were quantified in whole urine using nanoparticle tracking analysis (NTA), time-resolved fluorescence immunoassay (TR-FIA), and EVQuant, a novel method quantifying particles via gel immobilization.

RESULTS

Urine particle and creatinine concentrations were highly correlated in the water-loading study (R² 0.96) and in random spot urines from healthy subjects (R² 0.47-0.95) and patients (R² 0.41-0.81). Water loading reduced aquaporin-2 but increased Tamm-Horsfall protein (THP) and particle detection by NTA. This finding was attributed to hypotonicity increasing uEV size (more EVs reach the NTA size detection limit) and reducing THP polymerization. Adding THP to urine also significantly increased particle count by NTA. In both fluorescence NTA and EVQuant, adding 0.01% SDS maintained uEV integrity and increased aquaporin-2 detection. Comparison of intracellular- and extracellular-epitope antibodies suggested the presence of reverse topology uEVs. The exosome markers CD9 and CD63 colocalized and immunoprecipitated selectively with distal nephron markers. Conclusions uEV concentration is highly correlated with urine creatinine, potentially replacing the need for uEV quantification to normalize spot urines. Additional findings relevant for future uEV studies in whole urine include the interference of THP with NTA, excretion of larger uEVs in dilute urine, the ability to use detergent to increase intracellular-epitope recognition in uEVs, and CD9 or CD63 capture of nephron segment-specific EVs.

Therapeutic Potential for Regulation of the Nuclear Factor Kappa-B Transcription Factor p65 to Prevent Cellular Senescence and Activation of Pro-Inflammatory in Mesenchymal Stem Cells

Mesenchymal stem cells have an important potential in the treatment of age-related diseases. In the last years, small extracellular vesicles derived from these stem cells have been proposed as cell-free therapies. Cellular senescence and proinflammatory activation are involved in the loss of therapeutic capacity and in the phenomenon called inflamm-aging. The regulators of these two biological processes in mesenchymal stem cells are not well-known. In this study, we found that p65 is activated during cellular senescence and inflammatory activation in human umbilical cord-derived mesenchymal stem cell. To demonstrate the central role of p65 in these two processes, we used small-molecular inhibitors of p65, such as JSH-23, MG-132 and curcumin. We found that the inhibition of p65 prevents the cellular senescence phenotype in human umbilical cord-derived mesenchymal stem cells. Besides, p65 inhibition produced the inactivation of proinflammatory molecules as components of a senescence-associated secretory phenotype (SASP) (interleukin-6 and interleukin-8 (IL-6 and IL-8)). Additionally, we found that the inhibition of p65 prevents the transmission of paracrine senescence between mesenchymal stem cells and the proinflammatory message through small extracellular vesicles. Our work highlights the important role of p65 and its inhibition to restore the loss of functionality of small extracellular vesicles from senescent mesenchymal stem cells and their inflamm-aging signature.

An optimized method for plasma extracellular vesicles isolation to exclude the copresence of biological drugs and plasma proteins which impairs their biological characterization

Extracellular vesicles (EVs) are cell membrane-derived phospholipid bilayer nanostructures that contain bioactive proteins, enzymes, lipids and polymers of nucleotides. They play a role in intercellular communication and are present in body fluids. EVs can be isolated by methods like ultracentrifugation (UC), polyethylene-glycol-precipitation (PEG) or size exclusion chromatography (SEC). The co-presence of immunoglobulins (Ig) in EV samples isolated from plasma (pEVs) is often reported and this may influence the assessment of the biological function and phenotype of EVs in bio- and immunoassay. Here, we studied the presence of an Ig-based therapeutic (etanercept) in pEV samples isolated from rheumatoid arthritis (RA) patients and improved the isolation method to obtain purer pEVs. From plasma of etanercept (Tumor-necrosis-factor (TNF)-α antibodies)-treated RA patients pEVs were isolated by either UC, PEG or SEC. SEC isolated pEVs showed the highest particle-to-protein ratio. Strong TNF-α inhibition determined in a TNF-α sensitive reporter assay was observed by pEVs isolated by UC and PEG, and to a lesser extent by SEC, suggesting the presence of functional etanercept. SEC isolation of etanercept or labelled immunoglobulin G (IgG) showed co-isolation of these antibodies in the pEV fraction in the presence of plasma or a high protein (albumin) concentration. To minimize the presence of etanercept or immunoglobulins, we extended SEC (eSEC) column length from 56mm to 222mm (total stacking volume unchanged). No effect on the amount of isolated pEVs was observed while protein and IgG content were markedly reduced (90%). Next, from six etanercept- treated RA patients, pEVs were isolated on a eSEC or standard SEC column, in parallel. TNF-α inhibition was again observed in pEVs isolated by conventional SEC but not by eSEC. To confirm the purer pEVs isolated by eSEC the basal IL-8 promoter activation in human monocytes was determined and in 4 out of 5 SEC isolated pEVs activation was observed while eSEC isolated pEVs did not. This study shows that extended SEC columns yielded pEVs without detectable biologicals and with low protein and IgG levels. This isolation method will improve the characterization of pEVs as potential biomarkers and mediators of disease.

Influence of mesenchymal stem cell-derived extracellular vesicles in vitro and their role in ageing

INTRODUCTION

This study assessed whether mesenchymal stem cell (MSC)-derived extracellular vesicles influenced ageing and pluripotency markers in cell cultures where they are added.

METHODS

MSC-derived extracellular vesicles from old and young rat bone marrows were isolated by ultracentrifugation and were characterised by western blotting, nanoparticle tracking analysis (NTA) and transmission electron microscopy (TEM). They were added to young and old MSC cultures. Real-time quantitative reverse transcription polymerase chain reactions and western blot analysis were performed to check the markers of ageing (vinculin and lamin A), pluripotency markers (Nanog and Oct4) and components of the mTOR signalling pathway (Rictor, Raptor, AKT and mTOR) in these cell populations. Subsequently, microRNA (miR)-188-3p expression was transiently inhibited in young MSCs to demonstrate the influence of mTOR2 on MSC ageing.

RESULTS

Incubation with young MSC-derived extracellular vesicles decreased the levels of ageing markers and components of the mTOR pathway and increased the pluripotency markers from old MSC populations. By contrast, incubation of young MSCs with old MSC-derived extracellular vesicles generated the reverse effects. Inhibition of miR-188-3p expression in young MSCs produced extracellular vesicles that when incubated with old MSCs produced an increase in the levels of Rictor, as well as a decrease of phosphor-AKT, as indicated by a significant decrease in beta-galactosidase staining.

CONCLUSIONS

MSC-derived extracellular vesicles affected the behaviour of MSC cultures, based on their composition, which could be modified in vitro. These experiments represented the basis for the development of new therapies against ageing-associated diseases using MSC-derived extracellular vesicles.

Rheumatoid Arthritis Patients With Circulating Extracellular Vesicles Positive for IgM Rheumatoid Factor Have Higher Disease Activity

Rheumatoid arthritis (RA) is an autoimmune inflammatory disease that mainly affects synovial joints. Validated laboratory parameters for RA diagnosis are higher blood levels of rheumatoid factor IgM (IgM-RF), anti-citrullinated protein autoantibodies (ACPA), C-reactive protein (CRP) levels and erythrocyte sedimentation rate (ESR). Clinical parameters used are the number of tender (TJC) and swollen joints (SJC) and the global patient visual analog score (VAS). To determine disease remission in patients a disease activity score (DAS28) can be calculated based on SJC, TJC, VAS, and ESR (or alternatively CRP). However, subtle and better predictive changes to follow treatment responses in individual patients cannot be measured by the above mentioned parameters nor by measuring cytokine levels in blood. As extracellular vesicles (EVs) play a role in intercellular communication and carry a multitude of signals we set out to determine their value as a biomarker for disease activity. EVs were isolated from platelet-free plasma of 41 RA patients and 24 healthy controls (HC) by size exclusion chromatography (SEC). We quantified the particle and protein concentration, using NanoSight particle tracking analysis and micro-BCA, respectively, and observed no differences between RA patients and HC. In plasma of 28 out of 41 RA patients IgM-RF was detectable by ELISA, and in 13 out of these 28 seropositive RA patients (RF⁺RA) IgM-RF was also detected on their isolated pEVs (IgM-RF⁺). In seronegative RA patients (RF^-RA) we did not find any RF present on pEVs. When comparing disease parameters we found no differences between RF⁺RA and RF^-RA patients, except for increased ESR levels in RF⁺RA patients. However, RF⁺RA patients with IgM-RF⁺ pEVs showed significantly higher levels of CRP and ESR and also VAS and DAS28 were significantly increased compared to RA⁺ patients without IgM-RF⁺ pEVs. This study shows for the first time the presence of IgM-RF on pEVs in a proportion of RF⁺RA patients with a higher disease activity.

Corrigendum: Effect of age on pro-inflammatory miRNAs contained in mesenchymal stem cell-derived extracellular vesicles

This corrects the article DOI: 10.1038/srep43923.

Suppression of the inflammatory response by disease-inducible interleukin-10 gene therapy in a three-dimensional micromass model of the human synovial membrane

Background

Gene therapy has the potential to provide long-term production of therapeutic proteins in the joints of osteoarthritis (OA) patients. The objective of this study was to analyse the therapeutic potential of disease-inducible expression of anti-inflammatory interleukin-10 (IL-10) in the three-dimensional micromass model of the human synovial membrane.

Methods

Synovial tissue samples from OA patients were digested and the cells were mixed with Matrigel to obtain 3D micromasses. The CXCL10 promoter combined with the firefly luciferase reporter in a lentiviral vector was used to determine the response of the CXCL10 promoter to tumour necrosis factor alpha (TNF-α), interleukin-1β (IL-1β) and lipopolysaccharide (LPS). The effects of recombinant IL-10 on gene expression were determined by quantitative PCR. The production of IL-10 from the CXCL10p-IL10 vector and the effects on pro-inflammatory cytokine production were assessed by multiplex ELISA.

Results

Micromasses made from whole synovial membrane cell suspensions form a distinct surface composition containing macrophage and fibroblast-like synoviocytes thus mimicking the synovial lining. This lining can be transduced by lentiviruses and allow CXCL-10 promoter-regulated transgene expression. Adequate amounts of IL-10 transgene were produced after stimulation with pro-inflammatory factors able to reduce the production of synovial IL-1β and IL-6.

Conclusions

Synovial micromasses are a suitable model to test disease-regulated gene therapy approaches and the CXCL10p-IL10 vector might be a good candidate to decrease the inflammatory response implicated in the pathogenesis of OA.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-016-1083-1) contains supplementary material, which is available to authorized users.

Milk-Derived Nanoparticle Fraction Promotes the Formation of Small Osteoclasts But Reduces Bone Resorption

The general consensus is that milk promotes bone growth and density because is a source of calcium and contains components that enhance intestinal calcium uptake or directly affect bone metabolism. In this study, we investigated the effect of bovine-derived milk 100,000 g pellet (P100), which contains nanoparticles (<220 nm) including extracellular vesicles, on osteoclast differentiation and bone resorption. Bone marrow-derived osteoclast precursor cells were differentiated into osteoclasts by M-CSF and RANKL (control) and in the presence of milk P100. Milk P100 treatment until day 4 increased the number of TRAP-positive mononuclear cells and small (≤5 nuclei) osteoclasts. The number of large (≥6 nuclei) osteoclasts remained the same. These alterations were associated with increased expression of TRAP, NFATc1, and c-Fos. Cells seeded in a calcium-phosphate coated plate or bone slices showed reduced resorption area when exposed to milk P100 during the differentiation phase and even after osteoclast formation. Interestingly, milk P100 treatment enhanced Cathepsin K expression but reduced Carbonic Anhydrase 2 gene expression. Moreover, intracellular acid production was also decreased by milk P100 treatment. Oral delivery of milk P100 to female DBA1/J mice for 7 weeks did not alter bone area; however, increased osteoclast number and area in tibia without changes in serum RANKL and CTX-I levels. We showed for the first time the effect of milk P100 on osteoclast differentiation both in vitro and in vivo and found that milk P100 increased the formation of small osteoclasts but this does not lead to more bone resorption probably due to reduced acid secretion. J. Cell. Physiol. 232: 225-233, 2017. © 2016 Wiley Periodicals, Inc.

Disease-Regulated Gene Therapy with Anti-Inflammatory Interleukin-10 Under the Control of the CXCL10 Promoter for the Treatment of Rheumatoid Arthritis

Disease-inducible promoters for the treatment of rheumatoid arthritis (RA) have the potential to provide regulated expression of therapeutic proteins in arthritic joints. In this study, we set out to identify promoters of human genes that are upregulated during RA and are suitable to drive the expression of relevant amounts of anti-inflammatory interleukin (IL)-10. Microarray analysis of RA synovial biopsies compared with healthy controls yielded a list of 22 genes upregulated during RA. Of these genes, CXCL10 showed the highest induction in lipopolysaccharide-stimulated synovial cells. The CXCL10 promoter was obtained from human cDNA and cloned into a lentiviral vector carrying firefly luciferase to determine the promoter inducibility in primary synovial cells and in THP-1 cells. The promoter activation was strongest 8-12 hr after stimulation with the proinflammatory cytokine tumor necrosis factor (TNF)-α and was reinducible after 96 hr. In addition, the CXCL10 promoter showed a significant response to RA patient serum, compared with sera from healthy individuals. The luciferase gene was replaced with IL-10 to determine the therapeutic properties of the CXCL10p-IL10 lentiviral vector. Primary synovial cells transduced with CXCL10p-IL10 showed a great increase in IL-10 production after stimulation, which reduced the release of proinflammatory cytokines TNF-α and IL-1β. We conclude that the selected proximal promoter of the CXCL10 gene responds to inflammatory mediators present in the serum of patients with RA and that transduction with the lentiviral CXCL10p-IL10 vector reduces inflammatory cytokine production by primary synovial cells from patients with RA. CXCL10 promoter-regulated IL-10 overexpression can thus provide disease-inducible local gene therapy suitable for RA.

Milk extracellular vesicles accelerate osteoblastogenesis but impair bone matrix formation

The claimed beneficial effect of milk on bone is still a matter for debate. Recently extracellular vesicles (EVs) that contain proteins and RNA were discovered in milk, but their effect on bone formation has not yet been determined. We demonstrated previously that bovine milk-derived EVs (BMEVs) have immunoregulatory properties. Our aim was to evaluate the effect of BMEVs on osteogenesis by mice and human mesenchymal stem cells (hMSCs). Oral delivery of two concentrations of BMEVs to female DBA/1J mice during 7weeks did not alter the tibia trabecular bone area; however, the osteocytes number increased. In addition, the highest dose of BMEVs markedly increased the woven bone tissue, which is more brittle. The exposure of hMSCs to BMEVs during 21days resulted in less mineralization but higher cell proliferation. Interestingly BMEVs reduced the collagen production, but enhanced the expression of genes characteristic for immature osteoblasts. A kinetic study showed that BMEVs up-regulated many osteogenic genes within the first 4days. However, the production of type I collagen and expression of its genes (COL1A1 and COL1A2) were markedly reduced at days 21 and 28. At day 28, BMEVs again lead to higher proliferation, but mineralization was significantly increased. This was associated with increased expression of sclerostin, a marker for osteocytes, and reduced osteonectin, which is associated to bone matrix formation. Our study adds BMEVs to the list of milk components that can affect bone formation and may shed new light on the contradictory claims of milk on bone formation.

Oral administration of bovine milk derived extracellular vesicles attenuates arthritis in two mouse models

SCOPE

This study shows the effect of bovine milk derived extracellular vesicles (BMEVs) on spontaneous polyarthritis in IL-1Ra-deficient mice and collagen-induced arthritis.

METHODS AND RESULTS

BMEVs were isolated from semi-skimmed milk by ultracentrifugation and the particle size was around 100 nm by dynamic light scattering and electron microscopy. BMEVs expressed exosome marker CD63, immunoregulatory microRNA's (miR-30a, -223, -92a), and milk-specific beta-casein and beta-lactoglobulin mRNA. In vitro, PKH-67-labeled BMEVs were taken up by RAW264.7, splenocytes, and intestinal cells as determined by flow cytometry and confocal microscopy. IL-1Ra(-/-) mice received BMEVs by daily oral gavage starting at wk 5 till 15 after birth and collagen-induced arthritis mice via their drinking water starting 1 wk before immunization till day 40. Macroscopically, BMEV treatment delayed the onset of arthritis and histology showed diminished cartilage pathology and bone marrow inflammation in both models. BMEV treatment also reduced the serum levels of MCP-1 and IL-6 and their production by splenic cells. BMEV treatment diminished the anticollagen IgG2a levels, which was accompanied by reduced splenic Th1 (Tbet) and Th17 (RORγT) mRNA.

CONCLUSION

This is the first report that oral delivery of BMEVs ameliorates experimental arthritis and this warrants further research to determine whether this beneficial effect can be seen in rheumatoid arthritis patients.

Disease-regulated local IL-10 gene therapy diminishes synovitis and cartilage proteoglycan depletion in experimental arthritis

OBJECTIVES

Rheumatoid arthritis is a chronic destructive autoimmune disease, but the course is unpredictable in individual patients. An attractive treatment would provide a disease-regulated therapy that offers personalised drug delivery. Therefore, we expressed the anti-inflammatory interleukin-10 (IL-10) gene under the control of inflammation-dependent promoters in a mouse model of arthritis.

METHODS

Proximal promoters of S100a8, Cxcl1, Mmp13, Saa3, IL-1b and Tsg6 were selected by whole-genome expression analysis of inflamed synovial tissues from arthritic mice. Mice were injected intraarticularly in knee joints with lentiviral vectors expressing a luciferase reporter or the therapeutic protein IL-10 under control of the Saa3 or Mmp13 promoter. After 4 days, arthritis was induced by intraarticular injection of streptococcal cell walls (SCW). At different time points after arthritis induction, in vivo bioluminescent imaging was performed and knee joints were dissected for histological and RNA analysis.

RESULTS

The disease-regulated promoter-luciferase reporter constructs showed different activation profiles during the course of the disease. The Saa3 and Mmp13 promoters were significantly induced at day 1 or day 4 after arthritis induction respectively and selected for further research. Overexpression of IL-10 using these two disease-inducible promoters resulted in less synovitis and markedly diminished cartilage proteoglycan depletion and in upregulation of IL-1Ra and SOCS3 gene expression.

CONCLUSIONS

Our study shows that promoters of genes that are expressed locally during arthritis can be candidates for disease-regulated overexpression of biologics into arthritic joints, as shown for IL-10 in SCW arthritis. The disease-inducible approach might be promising for future tailor-made local gene therapy in arthritis.

In vivo molecular imaging of cathepsin and matrix metalloproteinase activity discriminates between arthritic and osteoarthritic processes in mice

Rheumatoid arthritis (RA) and osteoarthritis (OA) are serologically and clinically distinctive, but at the local level, both diseases have many molecular pathways in common. In vivo molecular imaging can unravel the local pathologic processes involved in both diseases. In this study, we investigated matrix metalloproteinase (MMP) and cathepsin activity during cartilage destruction, in an RA and an OA mouse model, using biophotonic imaging of substrate-based probes. Mice with collagen-induced arthritis (CIA) or destabilization of the medial meniscus (DMM) were imaged using near-infrared fluorescent probes, activated by several cathepsins or MMPs. Fluorescence signal intensity was compared to synovial gene expression, histology, and cartilage staining of a neoepitope of aggrecan cleaved by MMPs with the amino acids DIPEN. Increased cathepsin and MMP activity was seen during CIA, whereas the DMM model only showed increased MMP activity. DIPEN expression was seen only during CIA. A possible explanation can be differences in gene expressions; MMP3 and -13, known to produce DIPEN neoepitopes, were upregulated in the CIA model, whereas MMP12, known to be involved in elastin degradation and chemokine inhibition, was upregulated in the DMM model. Thus, molecular imaging showed no cathepsin activity at the time of cartilage damage in the DMM model, whereas both cathepsins and MMPs are active in the CIA model during disease progression.

Therapeutic efficacy of Tyro3, Axl, and Mer tyrosine kinase agonists in collagen-induced arthritis

OBJECTIVE

Hyperactivation of innate immunity by Toll-like receptors (TLRs) can contribute to the development of autoinflammatory or autoimmune diseases. This study evaluated the activation of Tyro3, Axl, Mer (TAM) receptors, physiologic negative regulators of TLRs, by their agonists, growth arrest-specific protein 6 (GAS-6) and protein S, in the prevention of collagen-induced arthritis (CIA).

METHODS

Adenoviruses overexpressing GAS-6 and protein S were injected intravenously or intraarticularly into mice during CIA. Splenic T helper cell subsets from intravenously injected mice were studied by flow cytometry, and the knee joints of mice injected intravenously and intraarticularly were assessed histologically. Synovium from mice injected intraarticularly was evaluated for cytokine and suppressor of cytokine signaling (SOCS) expression.

RESULTS

Protein S significantly reduced ankle joint swelling when overexpressed systemically. Further analysis of knee joints revealed a moderate reduction in pathologic changes in the joint and a significant reduction in the number of splenic Th1 cells when protein S was overexpressed systemically. Local overexpression of GAS-6 decreased joint inflammation and joint pathology. Protein S treatment showed a similar trend of protection. Consistently, GAS-6 and protein S reduced cytokine production in the synovium. Moreover, levels of messenger RNA for interleukin-12 (IL-12) and IL-23 were reduced by GAS-6 and protein S treatment, with a corresponding decrease in the production of interferon-γ and IL-17. TAM ligand overexpression was associated with an increase in SOCS-3 levels, which likely contributed to the amelioration of arthritis.

CONCLUSION

This study provides the first evidence that TAM receptor stimulation by GAS-6 and protein S can be used to ameliorate arthritis when applied systemically or locally. TAM receptor stimulation limits proinflammatory signaling and adaptive immunity. This pathway provides a novel strategy by which to combat rheumatoid arthritis.

Intravenous delivery of HIV-based lentiviral vectors preferentially transduces F4/80+ and Ly-6C+ cells in spleen, important target cells in autoimmune arthritis

Antigen presenting cells (APCs) play an important role in arthritis and APC specific gene therapeutic targeting will enable intracellular modulation of cell activity. Viral mediated overexpression is a potent approach to achieve adequate transgene expression levels and lentivirus (LV) is useful for sustained expression in target cells. Therefore, we studied the feasibility of lentiviral mediated targeting of APCs in experimental arthritis. Third generation VSV-G pseudotyped self-inactivating (SIN)-LV were injected intravenously and spleen cells were analyzed with flow cytometry for green fluorescent protein (GFP) transgene expression and cell surface markers. Collagen-induced arthritis (CIA) was induced by immunization with bovine collagen type II in complete Freund's adjuvant. Effect on inflammation was monitored macroscopically and T-cell subsets in spleen were analyzed by flow cytometry. Synovium from arthritic knee joints were analyzed for proinflammatory cytokine expression. Lentiviruses injected via the tail vein preferentially infected the spleen and transduction peaks at day 10. A dose escalating study showed that 8% of all spleen cells were targeted and further analysis showed that predominantly Ly6C+ and F4/80+ cells in spleen were targeted by the LV. To study the feasibility of blocking TAK1-dependent pathways by this approach, a catalytically inactive mutant of TAK1 (TAK1-K63W) was overexpressed during CIA. LV-TAK1-K63W significantly reduced incidence and arthritis severity macroscopically. Further histological analysis showed a significant decrease in bone erosion in LV-TAK1-K63W treated animals. Moreover, systemic Th17 levels were decreased by LV-TAK1-K63W treatment in addition to diminished IL-6 and KC production in inflamed synovium. In conclusion, systemically delivered LV efficiently targets monocytes and macrophages in spleen that are involved in autoimmune arthritis. Moreover, this study confirms efficacy of TAK1 targeting in arthritis. This approach may provide a valuable tool in targeting splenic APCs, to unravel their role in autoimmune arthritis and to identify and validate APC specific therapeutic targets.

Enhanced suppressor of cytokine signaling 3 in arthritic cartilage dysregulates human chondrocyte function

OBJECTIVE

To determine the expression of suppressor of cytokine signaling 3 (SOCS-3) in human articular chondrocytes and its functional consequences.

METHODS

Chondrocytes were isolated from the cartilage of patients with osteoarthritis (OA), patients with rheumatoid arthritis (RA), and trauma patients and from the healthy cartilage of patients with a femoral neck fracture. The human chondrocyte cell line G6 and primary bovine chondrocytes were used in validation experiments. SOCS-3 messenger RNA (mRNA) expression was measured by quantitative polymerase chain reaction, and SOCS-3 protein levels were determined by Western blotting and immunohistochemical analysis. To ascertain the role of SOCS-3 in the chondrocyte response to interleukin-1β (IL-1β) or lipopolysaccharide (LPS), the expression of SOCS3 was either reduced by small interfering RNA or enhanced by viral transduction.

RESULTS

The expression of SOCS-3 mRNA (but not that of SOCS-1 mRNA) was significantly enhanced in chondrocytes obtained from OA cartilage (mean ± SD ΔC(t) 3.4 ± 1.0) and RA cartilage (ΔC(t) 3.4 ± 1.4) compared with cartilage obtained from patients with femoral neck fracture (ΔC(t) 5.3 ± 1.2). The expression of SOCS3 correlated significantly with that of other genes known to be expressed in arthritic chondrocytes, such as MMP13 (r = 0.743), ADAMTS4 (r = 0.779), and ADAMTS5 (r = 0.647), and an inverse relationship was observed with COL2A1 (r = -0.561). Up-regulation of SOCS-3 by IL-1 in G6 chondrocytes and its spontaneous expression in OA chondrocytes were reduced by mithramycin, a specific inhibitor of transcription factor Sp-1. Overexpression of SOCS-3 in bovine chondrocytes reduced IL-1- and LPS-induced nitric oxide production and insulin-like growth factor 1-induced proteoglycan synthesis. Interestingly, a similar impairment of function was observed in OA chondrocytes, which was partially restored by SOCS-3 gene knockdown.

CONCLUSION

This study demonstrated that both SOCS-3 mRNA and SOCS-3 protein are expressed in human arthritic chondrocytes and affect cellular responses involved in cartilage pathology.

Toll-like receptor 4 in bone marrow-derived cells as well as tissue-resident cells participate in aggravating autoimmune destructive arthritis

OBJECTIVE

A prominent role of Toll-like receptor 4 (TLR4) in arthritis is emerging. TLR4 is functional in immune cells and stromal cells. The aim was to investigate the involvement of TLR4 in bone marrow (BM)-derived and resident cells in arthritis.

METHODS

Reciprocal sex-mismatched BM transplantation was performed between IL-1Ra(-/-)TLR4(+/+) and IL-1Ra(-/-)TLR4(-/-) double knockout animals in Balb/c background. Arthritis was assessed macroscopically and by histopathology. Immunity was evaluated by splenic cytokine production and flow cytometry in draining lymph node (DLN) cells.

RESULTS

Arthritis progression was reduced to a similar extent in animals lacking TLR4 on BM-derived, resident cells or both. Histology revealed that joint inflammation was partially TLR4-dependent in either BM-derived or resident cells. TLR4 plays an additive role in BM-derived and resident cells in promoting cartilage erosion. By contrast, TLR4 was equally important in BM-derived and resident cells in mediating bone erosion. Systemically, TLR4 in both BM-derived and resident cells contributed to IL-17 production by splenic T-cells, whereas in the DLNs of arthritic joints this was not the case. Interestingly, in DLN, the dominant cells producing IL-17 were CD4 negative, and cell numbers were determined by TLR4 in the BM-derived cells.

CONCLUSIONS

TLR4 is necessary in both BM-derived and resident cells for full-blown joint swelling, inflammation and bone erosion. Furthermore, TLR4 on BM-derived and tissue-resident cells show an additive effect in cartilage destruction. Interestingly, TLR4 on BM-derived and tissue-resident cells are both required for IL-17 production in spleen, but only in BM-derived cells in DLN.

Destructive role of myeloid differentiation factor 88 and protective role of TRIF in interleukin-17-dependent arthritis in mice

OBJECTIVE

Increasing evidence indicates the involvement of Toll-like receptors (TLRs) in the progression of arthritis; however, the contribution of the two signaling pathways used by TLRs, which are mediated by myeloid differentiation factor 88 (MyD88) and TRIF, remains unclear. The objective of this study was to investigate the specific roles of MyD88 and TRIF in chronic experimental arthritis and the accompanying adaptive immune responses.

METHODS

Chronic arthritis was induced in wild-type, MyD88(-/-) , and Trif(lps2) (TRIF(-/-) ) mice by repetitive intraarticular injections of streptococcal cell wall (SCW) fragments. SCW-specific T cell and B cell responses, joint swelling, and histopathologic changes were analyzed during chronic arthritis.

RESULTS

Both MyD88 and TRIF pathways contributed to antigen-specific T cell proliferation and antibody production, with the MyD88 pathway playing the dominant role. The severity of joint swelling and synovial inflammation, as well as the histopathologic damage to cartilage and bone, was strongly dependent on MyD88 signaling, whereas TRIF was redundant. MyD88 signaling was critical for the development of pathogenic T cell response (i.e., interleukin-17 [IL-17] production) in response to SCW antigen. Interestingly, when the T cell-dependent phase was prolonged, TRIF signaling appeared to down-regulate bone erosion, an effect accompanied by an inhibitory effect on IL-17 production.

CONCLUSION

This study reveals a central role of MyD88 and a counterregulatory function of TRIF in T cell-driven arthritis. The findings provide a rationale for a pathway-specific interference in order to block the pathogenic features and to preserve or stimulate the beneficial aspects of TLR signaling.

A novel Saa3-promoter reporter distinguishes inflammatory subtypes in experimental arthritis and human synovial fibroblasts

OBJECTIVE

To evaluate the applicability of a lentiviral (LV) serum amyloid A3 (Saa3)-promoter luciferase (Luc) reporter for assessing inflammation in experimental arthritis, synovial fibroblasts (SF) from osteoarthritis (OA) and rheumatoid arthritis (RA) patients.

METHODS

In mice, synovium was transduced in vivo by cholesterol optimised LV, and two flares of acute joint inflammation were induced by injection of streptococcal cell wall (SCW) material into the knee-joint cavity. The time course of synovial inflammation was assessed using ex vivo luciferase assays, and histology. Uptake of (99m)technetium (Tc) was used to assess oedema. SF (n=12) of RA and OA patients were stratified by hierarchical clustering of whole genome expression profiles. Relative Saa3-promoter responses were determined in cytokine- or toll-like receptor (TLR)-stimulated SF subgroups.

RESULTS

In vivo, the Saa3-promoter reporter activity was strongly upregulated at 1 and 2 days after the first and second SCW challenge. The Saa3-promoter activities during acute inflammation correlated with Tc uptake measurements but were more sensitive and able to respond to the ongoing synovitis in the chronic phase of SCW arthritis. Molecular stratification defined two inflammatory SF subtypes, unrelated to disease classification. Relative Saa3-promoter responses to interleukin 1β, tumour necrosis factor α and TLR4 agonist were significantly increased in OA/RA SF with a high compared to a low inflammatory profile subtype. Serum stimulation of the Saa3-promoter reporter cell-line could distinguish between healthy and RA patients.

CONCLUSION

The Saa3-promoter reporter demonstrates a robust and feasible tool for assessing the course and severity of experimental arthritis and for distinguishing molecularly distinct inflammatory SF subtypes from a heterogeneous patient population.

Toll-like receptor 4 signalling is specifically TGF-beta-activated kinase 1 independent in synovial fibroblasts

OBJECTIVE

Activated synovial fibroblasts are key players in the pathogenesis of RA by driving inflammation and joint destruction. Numerous molecules including cytokines and Toll-like receptor (TLR) ligands induce pro-inflammatory signalling and gene expression through a hierarchical network of kinases. Upstream mitogen-activated protein kinase kinase kinases (MAP3Ks) represent an attractive target for RA treatment. In this study, we sought to determine the role of the MAP3K TGF-β-activated kinase 1 (TAK1) in cytokine and TLR-mediated signalling.

METHODS

TAK1 activity was inhibited using either a small molecule inhibitor or lentivirally overexpressed kinase-inactive TAK1-K63W mutant in murine embryonic and human dermal and synovial fibroblasts. Fibroblasts were stimulated with IL-1, TNF, TLR2 or TLR4 agonists and responses were evaluated using transcriptional reporters, western blotting and analysis of gene expression of collagenases (MMP3 and MMP13), cytokines (IL-1β and IL-6) and chemokines (IL-8 and MCP-1).

RESULTS

TAK1 inhibition abrogated cytokine- and TLR-induced nuclear factor-κB (NF-κB) and Saa3-promoter reporter activation in murine and human dermal fibroblasts. In synovial fibroblasts, TAK1 regulated IL-1 and TNF-mediated NF-κB, but not Saa3-promoter reporter activation. Inducible mRNA expression of cytokines, collagenases and chemokines, except MCP-1, was TAK1 dependent for IL-1, TNF and TLR2 signalling. Unexpectedly, TLR4-mediated NF-κB reporter activation and inducible mRNA expression was fully TAK1 independent. Accordingly, NF-κB p65 and p38 MAPK phosphorylation was unaffected by TAK1 inhibition.

CONCLUSION

In general, TAK1 crucially regulates IL-1 and TNF signalling in fibroblasts. Interestingly, TLR4 signalling is specifically TAK1 independent in synovial fibroblasts. Consequently, therapeutic TAK1 inhibition in arthropathies may not dampen the damage-associated molecular pattern-mediated TLR4 activation of synovial fibroblasts.

A crucial role for tumor necrosis factor receptor 1 in synovial lining cells and the reticuloendothelial system in mediating experimental arthritis

INTRODUCTION

Rheumatoid arthritis (RA) is an autoimmune inflammatory disease that mainly affects synovial joints. Biologics directed against tumor-necrosis-factor (TNF)-alpha are efficacious in the treatment of RA. However, the role of TNF receptor-1 (TNFR1) in mediating the TNFalpha effects in RA has not been elucidated and conflicting data exist in experimental arthritis models. The objective is to investigate the role of TNFR1 in the synovial lining cells (SLC) and the reticuloendothelial system (RES) during experimental arthritis.

METHODS

Third generation of adenovirus serotype 5 were either injected locally in the knee joint cavity or systemically by intravenous injection into the retro-orbital venous sinus to specifically target SLC and RES, respectively. Transduction of organs was detected by immunohistochemistry of the eGFP transgene. An adenoviral vector containing a short hairpin (sh) RNA directed against TNFR1 (HpTNFR1) was constructed and functionally evaluated in vitro using a nuclear factor-kappaB (NF-kappaB) reporter assay and in vivo in streptococcal cell wall-induced arthritis (SCW) and collagen-induced arthritis (CIA). Adenoviruses were administered before onset of CIA, and the effect of TNFR1 targeting on the clinical development of arthritis, histology, quantitative polymerase chain reaction (qPCR), cytokine analyses and T-cell assays was evaluated.

RESULTS

Systemic delivery of Ad5.CMV-eGFP predominantly transduced the RES in liver and spleen. Local delivery transduced the synovium and not the RES in liver, spleen and draining lymph nodes. In vitro, HpTNFR1 reduced the TNFR1 mRNA expression by three-fold resulting in a 70% reduction of TNFalpha-induced NF-kappaB activation. Local treatment with HpTNFR1 markedly reduced mRNA and protein levels of interleukin (IL)-1beta and IL-6 in SLC during SCW arthritis and ameliorated CIA. Systemic targeting of TNFR1 in RES of liver and spleen by systemic delivery of Ad5 virus encoding for a small hairpin RNA against TNFR1 markedly ameliorated CIA and simultaneously reduced the mRNA expression of IL-1beta, IL-6 and Saa1 (75%), in the liver and that of Th1/2/17-specific transcription factors T-bet, GATA-3 and RORgammaT in the spleen. Flow cytometry confirmed that HpTNFR1 reduced the numbers of interferon (IFN)gamma (Th1)-, IL-4 (Th2)- and IL-17 (Th17)-producing cells in spleen.

CONCLUSIONS

TNFR1-mediated signaling in both synovial lining cells and the reticuloendothelial system independently played a major pro-inflammatory and immunoregulatory role in the development of experimental arthritis.

The natural soluble form of IL-18 receptor beta exacerbates collagen-induced arthritis via modulation of T-cell immune responses

OBJECTIVE

IL-18 is a pluripotent cytokine that has been implicated in the development of rheumatoid arthritis. A soluble form of the IL-18 receptor accessory protein (sIL-18Rbeta) with unknown function has recently been identified. This study examined the ability of sIL-18Rbeta to inhibit IL-18 biological activities and to modulate immune responses during collagen-induced arthritis (CIA).

METHODS

Adenoviruses encoding sIL-18Rbeta were administered intravenously in type II collagen-immunised DBA/1 mice. Humoral responses were analysed by determining anti-bovine collagen type II (BCII) antibody levels by ELISA. Cytokine production by splenic T cells and cytokine levels in serum were measured by Luminex multi-analyte technology. CD4(+)CD25(+)Foxp3(+) regulatory T cells (Treg) were measured by flow cytometry.

RESULTS

Intravenous delivery of Ad5.sIL-18Rbeta in collagen-immunised mice led to enhanced transgene expression in splenic antigen-presenting cells (APC). A co-culture of these sIL-18Rbeta-transduced APC with purified splenic CD3(+) T cells led to a marked inhibition of IL-18-induced IFNgamma, IL-4 and IL-17 production by CD3(+) T cells. Remarkably, systemic treatment with Ad5.sIL-18Rbeta caused an exacerbation of arthritis, and histological evaluation of knee joints showed increased cartilage and bone erosion. No significant differences were observed in anti-BCII antibodies, but the aggravation was accompanied by decreased IFNgamma (-30%) and IL-4 (-44%) and increased IL-17 (+84%) production by splenic CD3(+) T cells. In addition, reduced circulating levels of CD4(+)CD25(+)Foxp3(+) Treg and anti-inflammatory IL-10 were shown.

CONCLUSION

This study identifies sIL-18Rbeta as a novel IL-18 inhibitor, which promotes CIA after intravenous overexpression by affecting Treg levels and supporting a T helper type 17 response.

Computational design and application of endogenous promoters for transcriptionally targeted gene therapy for rheumatoid arthritis

The promoter regions of genes that are differentially regulated in the synovial membrane during the course of rheumatoid arthritis (RA) represent attractive candidates for application in transcriptionally targeted gene therapy. In this study, we applied an unbiased computational approach to define proximal-promoters from a gene expression profiling study of murine experimental arthritis. Synovium expression profiles from progressing stages of collagen-induced arthritis (CIA) were classified into six distinct groups using k-means clustering. Using an algorithm based on local over-representation and comparative genomics, we identified putatively functional transcription factor-binding sites (TFBS) in TATA-dependent proximal-promoters. Applying a filter based on spacing between TATA box and transcription start site (TSS) combined with the presence of over-represented nuclear factor kappaB (NFkappaB), AP-1, or CCAAT/enhancer-binding protein beta (C/EBPbeta) sites, 382 candidate murine and human promoters were reduced to 66, corresponding to 45 genes. In vitro, 9 out of 10 computationally defined promoter regions conferred cytokine-inducible expression in murine cells and human synovial fibroblasts. Under these conditions, the serum amyloid A3 (Saa3) promoter showed the strongest transcriptional induction and strength. We applied this promoter for driving therapeutically efficacious levels of the interleukin-1 receptor antagonist (Il1rn) in a disease-regulated fashion. These results demonstrate the value of bioinformatics for guiding the selection of endogenous promoters for transcriptionally targeted gene therapy.

Stimulation of chondrocyte-mediated cartilage destruction by S100A8 in experimental murine arthritis

OBJECTIVE

To investigate whether S100A8 is actively involved in matrix metalloproteinase (MMP)-mediated chondrocyte activation.

METHODS

S100A8 and S100A9 proteins were detected in inflamed knee joints from mice with various forms of murine arthritis, using immunolocalization. Murine chondrocyte cell line H4 was stimulated with proinflammatory cytokines or recombinant S100A8. Messenger RNA (mRNA) and protein levels were measured using reverse transcriptase-polymerase chain reaction and intracellular fluorescence-activated cell sorting (FACS). Breakdown of aggrecan on the pericellular surface of the chondrocytes was measured using VDIPEN and NITEGE antibodies and FACS, and breakdown in patellar cartilage was measured by immunolocalization.

RESULTS

S100A8 and S100A9 proteins were abundantly expressed in and around chondrocytes in inflamed knee joints after induction of antigen-induced arthritis or onset of spontaneous arthritis in interleukin-1 (IL-1) receptor antagonist-knockout mice. Stimulation of chondrocytes by the proinflammatory cytokines tumor necrosis factor alpha, IL-1beta, IL-17, and interferon-gamma caused strong up-regulation of S100A8 mRNA and protein levels and up-regulation to a lesser extent of S100A9 levels. Stimulation of chondrocytes with S100A8 induced significant up-regulation of MMP-2, MMP-3, MMP-9, MMP-13, ADAMTS-4, and ADAMTS-5 mRNA levels (up-regulated 4, 4, 3, 16, 8, and 4 times, respectively). VDIPEN and NITEGE neoepitopes were significantly elevated in a concentration-dependent manner in chondrocytes treated with 0.2, 1, or 5 microg/ml of S100A8. (VDIPEN levels were elevated 17%, 67%, and 108%, respectively, and NITEGE levels were elevated 8%, 33%, and 67%, respectively.) S100A8 significantly increased the effect of IL-1beta on MMP-3, MMP-13, and ADAMTS-5. Mouse patellae incubated with both IL-1beta and S100A8 had elevated levels of NITEGE within the cartilage matrix when compared with patellae incubated with IL-1beta or S100A8 alone.

CONCLUSION

These findings indicate that S100A8 and S100A9 are found in and around chondrocytes in experimental arthritis. S100A8 up-regulates and activates MMPs and aggrecanase-mediated pericellular matrix degradation.

Application of a disease-regulated promoter is a safer mode of local IL-4 gene therapy for arthritis

The application of disease-regulated promoters in local gene therapy for rheumatoid arthritis potentiates the development of a sophisticated treatment that relies on a restricted and fine-tuned supply of biologicals. Although several studies have investigated regulated promoters for achieving effective transgene expression during arthritis, none have explored their potential for minimizing deleterious effects arising from constitutive overexpression of transgenes under naive conditions. Using naive and collagen-induced arthritic mice, we examined the applicability of a hybrid interleukin-1 enhancer/interleukin-6 proximal promoter for achieving efficacious murine interleukin-4 gene therapy under arthritic conditions, while minimizing interleukin-4-induced inflammation under naive conditions. We found strong upregulation of transgene expression in virally transduced knee joints under arthritic conditions compared to levels in naive animals. Besides its responsiveness, the promoter strength proved sufficient for generating therapeutically efficacious levels interleukin-4, as demonstrated by the successful protection against cartilage erosion in collagen-induced arthritis. Most importantly, promoter-mediated restriction of the potent chemotactic interleukin-4 in naive animals strongly reduced the amounts of inflammatory cell influx. This study suggests the suitability of the interleukin-1 enhancer/interleukin-6 proximal promoter for the development of a local gene therapy strategy for rheumatoid arthritis that requires fine-tuned and restricted expression of transgenes with a pleiotrophic nature.

A novel role for suppressor of cytokine signaling 3 in cartilage destruction via induction of chondrocyte desensitization toward insulin-like growth factor

OBJECTIVE

An important mechanism contributing to cartilage destruction in arthritis is chondrocyte desensitization toward its main anabolic factor, insulin-like growth factor 1 (IGF-1). In this study, we sought to determine the role of suppressor of cytokine signaling 3 (SOCS-3) in the induction of IGF-1 desensitization of murine chondrocytes.

METHODS

Chondrocyte responsiveness to IGF-1 was assessed by 35S-sulfate incorporation into proteoglycans (PGs), via aggrecan messenger RNA expression, using quantitative real-time polymerase chain reaction or insulin receptor substrate 1 (IRS-1) tyrosine phosphorylation (Western blot analysis). IGF-1 desensitization of patellar chondrocytes was studied in zymosan-induced arthritis. IGF-1 desensitization was induced in patellar cartilage explants or the H4 chondrocyte cell line, exposed to interleukin-1alpha (IL-1alpha). SOCS-3 protein expression was assessed by immunohistochemistry or by Western blot analysis of protein extracts. The role of SOCS-3 in IGF-1 signaling was elucidated by adenoviral overexpression.

RESULTS

Exposure of murine articular cartilage to IL-1 caused a significant decrease in IGF-1-induced PG synthesis. This effect also occurred in inducible nitric oxide synthase-knockout mice, revealing the involvement of a secondary IL-1-induced factor other than nitric oxide. We showed that IL-1 significantly up-regulated SOCS-3 transcription and protein synthesis in H4 chondrocytes. In contrast, IL-18 was unable to induce SOCS-3 expression and failed to induce chondrocyte IGF-1 desensitization. Histologic analysis of samples from arthritic knee joints revealed high expression of SOCS-3 in chondrocytes. Through adenoviral overexpression of SOCS-3, we obtained direct evidence that SOCS-3 inhibits IGF-1-mediated cell signaling, since IRS-1 phosphorylation was reduced.

CONCLUSION

This study demonstrates that IL-1-induced SOCS-3 expression is a novel mechanism of IGF-1 desensitization in chondrocytes; in conjunction with nitric oxide it can contribute to cartilage damage during arthritis.

Male IL-6 gene knock out mice developed more advanced osteoarthritis upon aging

OBJECTIVE

Interleukin-6 (IL-6) is expressed in osteoarthritic joints but its function in osteoarthritis (OA) is unknown. To study this, spontaneous and experimental OA were evaluated in IL-6 deficient (IL-6(-/-)) mice.

DESIGN

Histology of knees of 18-23-month-old wild type (wt) and IL-6(-/-) mice was compared for signs of OA. Cartilage proteoglycan (PG) density was measured by image analysis on safranin-O stained whole knee sections. Chondrocyte PG synthesis was measured ex vivo by (35)S-sulfate incorporation. Knee bone mineral density (BMD) was measured by dual energy x-ray absorptiometry. In young mice (3 months), OA was induced by intra-articular injection of collagenase.

RESULTS

The incidence of extensive cartilage loss at both lateral and medial sides was markedly higher in old IL-6(-/-) males, but not in females, as compared to their wt controls. Compared to age-matched wt mice, reduced ex vivo PG synthesis was found during aging in IL-6(-/-) males, without affecting their cartilage PG density. IL-6(-/-) males showed more extensive extracellular matrix deposition in the collateral ligaments and subchondral bone sclerosis, predominantly at the medial side. Total knee BMD decreased more in IL-6(-/-) (-23%) than in wt (-10%) males during aging. Collagenase-induced OA showed a similar degree of joint pathology in both strains, implying that OA susceptibility was not different at younger age.

CONCLUSIONS

Upon aging, IL-6(-/-) male mice developed more severe spontaneous OA. Reduced PG synthesis and BMD values might be indicative for an impaired repair response in IL-6(-/-) mice. This suggests a protective role for IL-6 in age-related OA in male mice.

Soluble interleukin-1 receptor accessory protein ameliorates collagen-induced arthritis by a different mode of action from that of interleukin-1 receptor antagonist

OBJECTIVE

To discern the mode of interleukin-1 (IL-1) inhibition of soluble IL-1 receptor accessory protein (sIL-1RAcP) by comparison with IL-1 receptor antagonist (IL-1Ra) in arthritis.

METHODS

Adenoviral vectors encoding either sIL-1RAcP or IL-1Ra were administered systemically before onset of collagen-induced arthritis in DBA/1 mice. Anti-bovine type II collagen IgG and IL-6 were quantified in serum. Proliferative response of splenic T cells was determined in the presence of sIL-1RAcP or IL-1Ra. The effect on IL-1 inhibition of recombinant sIL-1RAcP and IL-1Ra was further examined in vitro, using NF-kappaB luciferase reporter cell lines. Quantitative polymerase chain reaction was used to determine the relative messenger RNA expression of the IL-1 receptors.

RESULTS

Adenoviral overexpression of both sIL-1RAcP and IL-1Ra resulted in amelioration of the collagen-induced arthritis. Both IL-1 antagonists reduced the circulating levels of antigen-specific IgG2a antibodies, but only IL-1Ra was able to inhibit lymphocyte proliferation. By using purified lymphocyte populations derived from NF-kappaB reporter mice, we showed that sIL-1RAcP inhibits IL-1-induced NF-kappaB activity in B cells but not T cells, whereas IL-1Ra inhibited IL-1 on both cell types. A study in a panel of NF-kappaB luciferase reporter cells showed that the sIL-1RAcP inhibits IL-1 signaling on cells expressing either low levels of membrane IL-1RAcP or high levels of IL-1RII.

CONCLUSION

We show that the sIL-1RAcP ameliorated experimental arthritis without affecting T cell immunity, in contrast to IL-1Ra. Our results provide data in support of receptor competition by sIL-1RAcP as an explanation for the different mode of IL-1 antagonism in comparison with IL-1Ra.

Local activation of STAT-1 and STAT-3 in the inflamed synovium during zymosan-induced arthritis: exacerbation of joint inflammation in STAT-1 gene-knockout mice

OBJECTIVE

STAT proteins play an important role in cytokine signaling. Some investigators have reported preferential activation of STAT-1, and others have reported preferential activation of STAT-3, in response to endogenous interleukin-6 (IL-6), in patients with rheumatoid arthritis. The present study was undertaken to investigate synovial STAT-1 and STAT-3 activation in an experimental animal model of arthritis.

METHODS

Zymosan was injected intraarticularly into naive wild-type (WT), IL-6(-/-), and STAT-1(-/-) mice to induce arthritis. Western blots of synovial lysates were probed with phosphospecific antibodies to detect STAT-1/STAT-3 activation. Inflammation was assessed histologically. Synovial gene expression of the STAT-induced feedback inhibitors suppressor of cytokine signaling 1 (SOCS-1) and SOCS-3 in WT and STAT-1(-/-) mice was investigated by reverse transcriptase-polymerase chain reaction.

RESULTS

STAT-3 was activated in inflamed synovium of WT mice throughout the course of disease, whereas activated STAT-1 was observed only during the chronic phase. In IL-6(-/-) mice, STAT activation was limited to STAT-3 on day 1. Although macrophage influx was not inhibited, disease went into remission after day 7 in IL-6(-/-) mice. STAT-1 deficiency resulted in exacerbation of chronic joint inflammation and granuloma formation. In STAT-1(-/-) mice, STAT-3 activation in the inflamed joints was unaltered as compared with WT mice. However, synovial SOCS-1, but not SOCS-3, gene expression was markedly reduced in STAT-1(-/-) mice.

CONCLUSION

The results in the IL-6(-/-) mice suggest that STAT-3 is involved in the chronicity of ZIA. Exacerbation of arthritis in STAT-1(-/-) mice suggests an opposing effect of STAT-1, i.e., suppression of joint inflammation. The expression of SOCS-1 could be the underlying mechanism by which STAT-1 controls joint inflammation.

An inflammation-inducible adenoviral expression system for local treatment of the arthritic joint

To achieve a disease-regulated transgene expression for physiologically responsive gene therapy of arthritis, a hybrid promoter was constructed. The human IL-1 beta enhancer region (-3690 to -2720) upstream of the human IL-6 promoter region (-163 to +12) was essential in mounting a robust response in HIG-82 synovial fibroblasts and in RAW 264,7 macrophages. A replication-deficient adenovirus was engineered with luciferase (Luc) controlled by the IL-1/IL-6 promoter (Ad5.IL-1/IL-6-Luc). LPS caused a 23- and 4.6-fold induction of Luc. activity in RAW cells infected with Ad5.IL-1/IL-6-Luc or the conventional Ad5.CMV-Luc construct, respectively. Next, adenoviruses (10(6) ffu) were injected into the knees of C57Bl/6 mice. An intra-articular injection of zymosan, 3 days after Ad5.IL-1/IL-6-Luc, increased Luc. activity by 39-fold but had no effect in the Ad5.CMV-Luc joints. The constitutive CMV promoter was rapidly silenced and could not be reactivated in vivo. In contrast, the IL-1/IL-6 promoter could be reactivated by Streptococcal cell wall (SCW)-induced arthritis up to 21 days after infection. Next the IL-1/IL-6 promoter was compared to the C3-Tat/HIV-LTR two-component system in wild-type, IL-6(-/-) and IL-1(-/-) gene knockout mice. Both systems responded well to LPS-, zymosan- and SCW-induced arthritis. However, the basal activity of the IL-1/IL-6 promoter was lower and IL-6 independent. This study showed that the IL-1/IL-6 promoter is feasible to achieve disease-regulated transgene expression for treatment of arthritis.

Effectiveness of the soluble form of the interleukin-1 receptor accessory protein as an inhibitor of interleukin-1 in collagen-induced arthritis

OBJECTIVE

To investigate whether the soluble form of interleukin-1 (IL-1) receptor accessory protein (sIL-1RAcP), whose physiologic function remains to be established, can serve as a specific inhibitor of IL-1 signaling in vitro, and to evaluate its applicability in collagen-induced arthritis (CIA).

METHODS

Soluble IL-1RAcP was cloned from murine liver complementary DNA and expressed by the use of either an adenoviral vector (AdRGD) for sIL-1RAcP or a stable-transfected NIH3T3 fibroblast cell line. The ability of affinity-purified sIL-1RAcP to inhibit IL-1 signaling was tested on NF-kappaB luciferase reporter fibroblasts and quantified by luminometer. To investigate therapeutic efficacy, sIL-1RAcP was both locally (knee joint) and systemically overexpressed in collagen-immunized male DBA/1 mice. Severity of arthritis was monitored visually, and the pathologic process in the joint was examined histologically. Serum was obtained from mice to quantify IL-6 and anti-bovine type II collagen (BCII) antibody levels.

RESULTS

Incubation of the NF-kappaB reporter fibroblast with purified sIL-1RAcP protein showed a marked reduction of IL-1-induced, but not tumor necrosis factor-induced, NF-kappaB activation. This showed a novel role for sIL-1RAcP as a specific inhibitor of IL-1 signaling. Local transplantation of sIL-1RAcP-producing NIH3T3 fibroblasts into the knee before onset of CIA had little or no effect on general disease severity in these mice. Histologic evaluation of the knee joints receiving sIL-1RAcP cell transplantation showed a marked reduction in both joint inflammation and bone and cartilage erosion. Local treatment with sIL-1RAcP had no profound effect on serum levels of IL-6 and anti-BCII antibodies, which is indicative of the ongoing presence of arthritis in distal joints. In contrast to local treatment, systemic treatment with the AdRGD for sIL-1RAcP markedly ameliorated CIA in all joints.

CONCLUSION

In this study we demonstrated that sIL-1RAcP is a biologically active and innovative inhibitor of IL-1, and treatment of mice with sIL-1RAcP had a profound prophylactic effect on collagen-induced arthritis.

Deficiency of NADPH oxidase components p47phox and gp91phox caused granulomatous synovitis and increased connective tissue destruction in experimental arthritis models

Recent studies indicated that the nicotinamide dinucleotide phosphate oxidase (NADPH) oxidase-derived oxygen radicals plays a deleterious role in arthritis. To study this in more detail, gonarthritis was induced in NADPH oxidase-deficient mice. Mice received an intraarticular injection of either zymosan, to elicit an irritant-induced inflammation, or poly-L-lysine coupled lysozyme, to evoke an immune-complex mediated inflammation in passively immunized mice. In contrast to wild-type mice, arthritis elicited in both p47phox(-/-) and gp91(-/-) mice showed more severe joint inflammation, which developed into a granulomatous synovitis. Treatment with either Zileuton or cobra venom factor showed that the chemokines LTB4 and complement C3 were not the driving force behind the aggravated inflammation in these mice. Arthritic NADPH oxidase-deficient mice showed irreversible cartilage damage as judged by the enhanced aggrecan VDIPEN expression, and chondrocyte death. Furthermore, only in the absence of NADPH oxidase-derived oxygen radicals, the arthritic joints showed osteoclast-like cells, tartrate-resistant acid phosphatase (TRAP)-positive/multinucleated cells, extensive bone erosion, and osteolysis. The enhanced synovial gene expression of tumor necrosis factor-alpha, interleukin-1alpha, matrix metalloproteinase (MMP)-3, MMP-9 and receptor activator of NF-kappaB ligand (RANKL) might contribute to the aggravated arthritis in the NADPH oxidase-deficient mice. This showed that the involvement of NADPH oxidase in arthritis is probably far more complex and that oxygen radicals might also be important in controlling disease severity, and reducing joint inflammation and connective tissue damage.

Adenoviral delivery of IL-18 binding protein C ameliorates collagen-induced arthritis in mice

Elevated concentrations of interleukin-18 (IL-18) are found in both serum and synovial fluid of patients suffering from rheumatoid arthritis (RA) and this cytokine has recently been implicated in the development of experimental arthritis. In this present study, we developed an IL-18 neutralizing intervention and examined its efficacy for local intra-articular treatment of experimental arthritis. To this end we constructed an adenoviral vector containing the murine IL-18 binding protein isoform c gene (AdCMVIL-18BPc). The constructed adenoviral vector was validated on replication deficiency, transfection efficacy and ability to express biological functional IL-18BPc. Intra-articular overexpression of IL-18BPc significantly reduced incidence of collagen-induced arthritis (CIA) in treated kneejoints. Affected kneejoints of IL-18BPc-treated mice showed less severe arthritis, characterized by reduction of inflammation and destruction of bone and cartilage. Local intra-articular IL-1BPc treatment in both knees provided additional protection against CIA incidence and severity in distal paws. Measurement of serum levels of specific collagen type (CII) Abs revealed a moderate reduction of circulating IgG2a anti-CII Abs, while IgG1 anti-CII Abs remained at similar level. The present study underlines the involvement of IL-18 as an important proinflammatory cytokine in onset of experimental arthritis. Furthermore, it shows that endogenous IL-18 can be blocked efficiently through local adenoviral overexpression of IL-18BPc, indicating that treatment with IL-18BPc might contribute to joint protection in RA.