Tumour necrosis factor-alpha (TNF-alpha) enhances lymphocyte migration into rheumatoid synovial tissue transplanted into severe combined immunodeficient (SCID) mice

The CXCR4-CXCL12 axis promotes T cell reconstitution via efficient hematopoietic immigration

T cells play a critical role in immunity to protect against pathogens and malignant cells. T cell immunodeficiency is detrimental, especially when T cell perturbation occurs during severe infection, irradiation, chemotherapy, and age-related thymic atrophy. Therefore, strategies that enhance T cell reconstitution provide considerable benefit and warrant intensive investigation. Here, we report the construction of a T cell ablation model in Tg(coro1a:DenNTR) zebrafish via metronidazole administration. The nascent T cells are mainly derived from the hematopoietic cells migrated from the kidney, the functional homolog of bone marrow and the complete recovery time is 6.5 days post-treatment. The cxcr4b gene is upregulated in the responsive hematopoietic cells. Functional interference of CXCR4 via both genetic and chemical manipulations does not greatly affect T lymphopoiesis, but delays T cell regeneration by disrupting hematopoietic migration. In contrast, cxcr4b accelerates the replenishment of hematopoietic cells in the thymus. Consistently, Cxcl12b, a ligand of Cxcr4, is increased in the thymic epithelial cells of the injured animals. Decreased or increased expression of Cxcl12b results in compromised or accelerated T cell recovery, respectively, similar to those observed with Cxcr4b. Taken together, our study reveals a role of CXCR4-CXCL12 signaling in promoting T cell recovery and provides a promising target for the treatment of immunodeficiency due to T cell injury.

Novel Bispecific Antibody for Synovial-Specific Target Delivery of Anti-TNF Therapy in Rheumatoid Arthritis

Biologic drugs, especially anti-TNF, are considered as the gold standard therapy in rheumatoid arthritis. However, non-uniform efficacy, incidence of infections, and high costs are major concerns. Novel tissue-specific agents may overcome the current limitations of systemic administration, providing improved potency, and safety. We developed a bispecific antibody (BsAb), combining human arthritic joint targeting, via the synovial-specific single-chain variable fragment (scFv)-A7 antibody, and TNFα neutralization, via the scFv-anti-TNFα of adalimumab, with the binding/blocking capacity comparable to adalimumab -immunoglobulin G (IgG). Tissue-targeting capacity of the BsAb was confirmed on the human arthritic synovium in vitro and in a synovium xenograft Severe combined immune deficient (SCID) mouse model. Peak graft accumulation occurred at 48 h after injection with sustained levels over adalimumab-IgG for 7 days and increased therapeutic effect, efficiently decreasing tissue cellularity, and markers of inflammation with higher potency compared to the standard treatment. This study provides the first description of a BsAb capable of drug delivery, specifically to the disease tissue, and a strong evidence of improved therapeutic effect on the human arthritic synovium, with applications to other existing biologics.

Humanized Mouse Models of Rheumatoid Arthritis for Studies on Immunopathogenesis and Preclinical Testing of Cell-Based Therapies

Rodent models of rheumatoid arthritis (RA) have been used over decades to study the immunopathogenesis of the disease and to explore intervention strategies. Nevertheless, mouse models of RA reach their limit when it comes to testing of new therapeutic approaches such as cell-based therapies. Differences between the human and the murine immune system make it difficult to draw reliable conclusions about the success of immunotherapies. To overcome this issue, humanized mouse models have been established that mimic components of the human immune system in mice. Two main strategies have been pursued for humanization: the introduction of human transgenes such as human leukocyte antigen molecules or specific T cell receptors, and the generation of mouse/human chimera by transferring human cells or tissues into immunodeficient mice. Recently, both approaches have been combined to achieve more sophisticated humanized models of autoimmune diseases. This review discusses limitations of conventional mouse models of RA-like disease and provides a closer look into studies in humanized mice exploring their usefulness and necessity as preclinical models for testing of cell-based therapies in autoimmune diseases such as RA.

In vivo multiplex molecular imaging of vascular inflammation using surface-enhanced Raman spectroscopy

Vascular immune-inflammatory responses play a crucial role in the progression and outcome of atherosclerosis. The ability to assess localized inflammation through detection of specific vascular inflammatory biomarkers would significantly improve cardiovascular risk assessment and management; however, no multi-parameter molecular imaging technologies have been established to date. Here, we report the targeted in vivo imaging of multiple vascular biomarkers using antibody-functionalized nanoparticles and surface-enhanced Raman scattering (SERS).

Methods: A series of antibody-functionalized gold nanoprobes (BFNP) were designed containing unique Raman signals in order to detect intercellular adhesion molecule 1 (ICAM-1), vascular cell adhesion molecule 1 (VCAM-1) and P-selectin using SERS.

Results: SERS and BFNP were utilized to detect, discriminate and quantify ICAM-1, VCAM-1 and P-selectin in vitro on human endothelial cells and ex vivo in human coronary arteries. Ultimately, non-invasive multiplex imaging of adhesion molecules in a humanized mouse model was demonstrated in vivo following intravenous injection of the nanoprobes.

Conclusion: This study demonstrates that multiplexed SERS-based molecular imaging can indicate the status of vascular inflammation in vivo and gives promise for SERS as a clinical imaging technique for cardiovascular disease in the future.

Tumor necrosis factor receptor type I expression of CD4+ T cells in rheumatoid arthritis enables them to follow tumor necrosis factor gradients into the rheumatoid synovium

OBJECTIVE

The cytokine tumor necrosis factor (TNF) plays a central role in the pathogenesis of rheumatoid arthritis (RA), but its disease-specific effector mechanisms have not been fully elucidated. This study was undertaken to investigate the role of TNF in T cell accumulation and migration in the synovitic joints of RA patients.

METHODS

Vital tissue sections from rheumatoid synovium were generated using a horizontally oscillating microtome and were coincubated with fluorescence-labeled CD4+ T cells. Migration was detected by fluorescence and confocal microscopy. Migrating T cells were recovered from the tissue and analyzed for phenotype. Chemotaxis of CD4+ T cells from RA patients in response to increasing concentrations of TNF was analyzed in Transwell experiments.

RESULTS

CD4+ T cells from RA patients migrated into the tissue sections in significantly higher numbers than T cells from healthy controls. Migrating CD4+ T cells differed from nonmigrating ones in their increased expression of TNF receptor type I (TNFRI), which was expressed on a fraction of circulating CD4+ T cells from RA patients, but not from controls. CD4+ T cells from the peripheral blood of RA patients were also found to migrate along TNF concentration gradients ex vivo. Accordingly, blockade of either TNF or TNFRI nearly abrogated in vitro T cell migration in synovial tissue.

CONCLUSION

Our findings indicate that the interaction of TNF with TNFRI is pivotal for T cell migration in synovial tissue in vitro, and thereby suggest a relevant role of the cytokine for in vivo T cell trafficking to synovitic joints.

H-2g, a glucose analog of blood group H antigen, mediates monocyte recruitment in vitro and in vivo via IL-8/CXCL8

Objective

Monocyte (MN) recruitment is an essential inflammatory component of many autoimmune diseases, including rheumatoid arthritis (RA). In this study we investigated the ability of 2-fucosyllactose (H-2g), a glucose analog of blood group H antigen to induce MN migration in vivo and determined if H-2g-induced interleukin-8 (IL-8/CXCL8) plays a role in MN ingress in RA.

Methods

Sponge granuloma and intravital microscopy assays were performed to examine H-2g-induced in vivo MN migration and rolling, respectively. MNs were stimulated with H-2g, and the production of IL-8/CXCL8 was assessed by enzyme-linked immunosorbent assay and quantitative polymerase chain reaction. Lastly, in vitro MN migration assays and an in vivo RA synovial tissue severe combined immunodeficiency mouse model were used to determine the role of IL-8/CXCL8 in H-2g-induced MN migration.

Results

In vivo, H-2g induced significantly greater MN migration compared to phosphate buffered saline. Intravital microscopy revealed that H-2g mediates MN migration in vivo by inducing MN rolling. In addition, H-2g induced MN production of IL-8/CXCL8, a process that was dependent on Src kinase. Moreover, we found that H-2g mediated MN migration in vitro, and in vivo migration was inhibited by a neutralizing anti-IL-8/CXCL8 antibody.

Conclusion

These findings suggest that H-2g mediates MN recruitment in vitro and in vivo (in part) via IL-8/CXCL8.

Targeted delivery of cytokine therapy to rheumatoid tissue by a synovial targeting peptide

Objectives

The synovial endothelium targeting peptide (SyETP) CKSTHDRLC has been identified previously and was shown to preferentially localise to synovial xenografts in the human/severe combined immunodeficient (SCID) mouse chimera model of rheumatoid arthritis (RA). The objective of the current work was to generate SyETP-anti-inflammatory-cytokine fusion proteins that would deliver bioactive cytokines specifically to human synovial tissue.

Methods

Fusion proteins consisting of human interleukin (IL)-4 linked via a matrix metalloproteinase (MMP)-cleavable sequence to multiple copies of either SyETP or scrambled control peptide were expressed in insect cells, purified by Ni-chelate chromatography and bioactivity tested in vitro. The ability of SyETP to retain bioactive cytokine in synovial but not control skin xenografts in SCID mice was determined by in vivo imaging using nano-single-photon emission computed tomography-computed tomography (nano-SPECT-CT) and measuring signal transducer and activator of transcription 6 (STAT6) phosphorylation in synovial grafts following intravenous administration of the fusion protein.

Results

In vitro assays confirmed that IL-4 and the MMP-cleavable sequence were functional. IL-4-SyETP augmented production of IL-1 receptor antagonist (IL-1ra) by fibroblast-like synoviocytes (FLS) stimulated with IL-1β  in a dose-dependent manner. In vivo imaging showed that IL-4-SyETP was retained in synovial but not in skin tissue grafts and the period of retention was significantly enhanced through increasing the number of SyETP copies from one to three. Finally, retention correlated with increased bioactivity of the cytokine as quantified by STAT6 phosphorylation in synovial grafts.

Conclusions

The present work demonstrates that SyETP specifically delivers fused IL-4 to human rheumatoid synovium transplanted into SCID mice, thus providing a proof of concept for peptide-targeted tissue-specific immunotherapy in RA. This technology is potentially applicable to other biological treatments providing enhanced potency to inflammatory sites and reducing systemic toxicity.

Mapping pathogenesis of arthritis through small animal models

Animal models have been used for a number of decades to study arthritis and have contributed greatly to unravelling mechanisms of pathogenesis and validating new targets for treatment. All animal models have sets of limitations and over the years there has been natural refinement of existing models as well as creation of new ones. The success of genetic modification in mice has fuelled an exponential increase in the use of murine models for arthritis research and has significantly increased our understanding of disease processes. This review focuses on those rodent models of RA and OA that have current utility and are widely used by the research community. We highlight the subtle but important differences in existing models by positioning them on a pathogenesis map whereby model selection is determined by the specific aspect of disease to be studied. We discuss the evolving challenges in in vivo arthritis studies and our perceived gaps for future new model development. The document includes technical and cost implications of performing the described models, and the ethical considerations of such approaches.

Development of a novel recombinant biotherapeutic with applications in targeted therapy of human arthritis

OBJECTIVE

To isolate recombinant antibodies with specificity for human arthritic synovium and to develop targeting reagents with joint-specific delivery capacity for therapeutic and/or diagnostic applications.

METHODS

In vivo single-chain Fv (scFv) antibody phage display screening using a human synovial xenograft model was used to isolate antibodies specific to the microvasculature of human arthritic synovium. Single-chain Fv antibody tissue-specific reactivity was assessed by immunostaining of synovial tissues from normal controls and from patients with rheumatoid arthritis and osteoarthritis, normal human tissue arrays, and tissues from other patients with inflammatory diseases displaying neovasculogenesis. In vivo scFv antibody tissue-specific targeting capacity was examined in the human synovial xenograft model using both (125)I-labeled and biotinylated antibody.

RESULTS

We isolated a novel recombinant human antibody, scFv A7, with specificity for the microvasculature of human arthritic synovium. We showed that in vivo, this antibody could efficiently target human synovial microvasculature in SCID mice transplanted with human arthritic synovial xenografts. Our results demonstrated that scFv A7 antibody had no reactivity with the microvasculature or with other cellular components found in a comprehensive range of normal human tissues including normal human synovium. Further, we showed that the reactivity of the scFv A7 antibody was not a common feature of neovasculogenesis associated with chronic inflammatory conditions.

CONCLUSION

Here we report for the first time the identification of an scFv antibody, A7, that specifically recognizes an epitope expressed in the microvasculature of human arthritic synovium and that has the potential to be developed as a joint-specific pharmaceutical.

T cell lessons from the rheumatoid arthritis synovium SCID mouse model: CD3-rich synovium lacks response to CTLA-4Ig but is successfully treated by interleukin-17 neutralization

OBJECTIVE

To provide an intermediate step between classic arthritis models and clinical trials, the rheumatoid arthritis (RA) synovium SCID mouse model is a valuable tool for use during preclinical research. We undertook this study to investigate the validity of this humanized mouse model using anti-tumor necrosis factor (anti-TNF) and anti-interleukin-1 (anti-IL-1) treatment and to investigate the direct effect of T cells- and B cell-related therapies on the transplanted RA synovial tissue.

METHODS

CB17/SCID mice were engrafted with human RA synovial tissue and systemically treated with anti-TNF, anti-IL-1, anti-IL-17, CTLA-4Ig, anti-CD20, or isotype control antibodies.

RESULTS

Validation of the model with anti-TNF treatment significantly reduced serum cytokine levels and decreased histologic inflammation, whereas anti-IL-1 therapy did not show any effect on the RA synovial grafts. In mice engrafted with B cell-rich synovial tissue, anti-CD20 treatment showed clear therapeutic effects. Surprisingly, CTLA-4Ig treatment did not show any effects in this transplantation model, despite prescreening of the synovial tissue for the presence of CD3+ T cells and the costimulatory molecules CD80 and CD86. In contrast, great therapeutic potential was observed for anti-IL-17 treatment, but only when CD3+ T cells were abundantly present in the RA synovial tissue.

CONCLUSION

This human RA synovium SCID mouse model enabled us to show that CTLA-4Ig lacks direct effects on T cell activation processes in the synovial tissue. Further evidence was obtained that IL-17 might indeed be an interesting therapeutic target in RA patients with CD3-rich synovial tissue. Further characterization of the RA patients' individual synovial profiles is of great importance for achieving tailored therapy.

Macrophages in synovial inflammation

Synovial macrophages are one of the resident cell types in synovial tissue and while they remain relatively quiescent in the healthy joint, they become activated in the inflamed joint and, along with infiltrating monocytes/macrophages, regulate secretion of pro-inflammatory cytokines and enzymes involved in driving the inflammatory response and joint destruction. Synovial macrophages are positioned throughout the sub-lining layer and lining layer at the cartilage–pannus junction and mediate articular destruction. Sub-lining macrophages are now also considered as the most reliable biomarker for disease severity and response to therapy in rheumatoid arthritis (RA). There is a growing understanding of the molecular drivers of inflammation and an appreciation that the resolution of inflammation is an active process rather than a passive return to homeostasis, and this has implications for our understanding of the role of macrophages in inflammation. Macrophage phenotype determines the cytokine secretion profile and tissue destruction capabilities of these cells. Whereas inflammatory synovial macrophages have not yet been classified into one phenotype or another it is widely known that TNFα and IL-l, characteristically released by M1 macrophages, are abundant in RA while IL-10 activity, characteristic of M2 macrophages, is somewhat diminished. Here we will briefly review our current understanding of macrophages and macrophage polarization in RA as well as the elements implicated in controlling polarization, such as cytokines and transcription factors like NFκB, IRFs and NR4A, and pro-resolving factors, such as LXA4 and other lipid mediators which may promote a non-inflammatory, pro-resolving phenotype, and may represent a novel therapeutic paradigm.

Acute serum amyloid A induces migration, angiogenesis, and inflammation in synovial cells in vitro and in a human rheumatoid arthritis/SCID mouse chimera model

Serum amyloid A (A-SAA), an acute-phase protein with cytokine-like properties, is expressed at sites of inflammation. This study investigated the effects of A-SAA on chemokine-regulated migration and angiogenesis using rheumatoid arthritis (RA) cells and whole-tissue explants in vitro, ex vivo, and in vivo. A-SAA levels were measured by real-time PCR and ELISA. IL-8 and MCP-1 expression was examined in RA synovial fibroblasts, human microvascular endothelial cells, and RA synovial explants by ELISA. Neutrophil transendothelial cell migration, cell adhesion, invasion, and migration were examined using transwell leukocyte/monocyte migration assays, invasion assays, and adhesion assays with or without anti-MCP-1/anti-IL-8. NF-kappaB was examined using a specific inhibitor and Western blotting. An RA synovial/SCID mouse chimera model was used to examine the effects of A-SAA on cell migration, proliferation, and angiogenesis in vivo. High expression of A-SAA was demonstrated in RA patients (p < 0.05). A-SAA induced chemokine expression in a time- and dose-dependent manner (p < 0.05). Blockade with anti-scavenger receptor class B member 1 and lipoxin A4 (A-SAA receptors) significantly reduced chemokine expression in RA synovial tissue explants (p < 0.05). A-SAA induced cell invasion, neutrophil-transendothelial cell migration, monocyte migration, and adhesion (all p < 0.05), effects that were blocked by anti-IL-8 or anti-MCP-1. A-SAA-induced chemokine expression was mediated through NF-kappaB in RA explants (p < 0.05). Finally, in the RA synovial/SCID mouse chimera model, we demonstrated for the first time in vivo that A-SAA directly induces monocyte migration from the murine circulation into RA synovial grafts, synovial cell proliferation, and angiogenesis (p < 0.05). A-SAA promotes cell migrational mechanisms and angiogenesis critical to RA pathogenesis.

Ectopic lymphoid structures support ongoing production of class-switched autoantibodies in rheumatoid synovium

BACKGROUND

Follicular structures resembling germinal centres (GCs) that are characterized by follicular dendritic cell (FDC) networks have long been recognized in chronically inflamed tissues in autoimmune diseases, including the synovium of rheumatoid arthritis (RA). However, it is debated whether these ectopic structures promote autoimmunity and chronic inflammation driving the production of pathogenic autoantibodies. Anti-citrullinated protein/peptide antibodies (ACPA) are highly specific markers of RA, predict a poor prognosis, and have been suggested to be pathogenic. Therefore, the main study objectives were to determine whether ectopic lymphoid structures in RA synovium: (i) express activation-induced cytidine deaminase (AID), the enzyme required for somatic hypermutation and class-switch recombination (CSR) of Ig genes; (ii) support ongoing CSR and ACPA production; and (iii) remain functional in a RA/severe combined immunodeficiency (SCID) chimera model devoid of new immune cell influx into the synovium.

METHODS AND FINDINGS

Using immunohistochemistry (IHC) and quantitative Taqman real-time PCR (QT-PCR) in synovial tissue from 55 patients with RA, we demonstrated that FDC+ structures invariably expressed AID with a distribution resembling secondary lymphoid organs. Further, AID+/CD21+ follicular structures were surrounded by ACPA+/CD138+ plasma cells, as demonstrated by immune reactivity to citrullinated fibrinogen. Moreover, we identified a novel subset of synovial AID+/CD20+ B cells outside GCs resembling interfollicular large B cells. In order to gain direct functional evidence that AID+ structures support CSR and in situ manufacturing of class-switched ACPA, 34 SCID mice were transplanted with RA synovium and humanely killed at 4 wk for harvesting of transplants and sera. Persistent expression of AID and Igamma-Cmu circular transcripts (identifying ongoing IgM-IgG class-switching) was observed in synovial grafts expressing FDCs/CD21L. Furthermore, synovial mRNA levels of AID were closely associated with circulating human IgG ACPA in mouse sera. Finally, the survival and proliferation of functional B cell niches was associated with persistent overexpression of genes regulating ectopic lymphoneogenesis.

CONCLUSIONS

Our demonstration that FDC+ follicular units invariably express AID and are surrounded by ACPA-producing plasma cells provides strong evidence that ectopic lymphoid structures in the RA synovium are functional and support autoantibody production. This concept is further confirmed by evidence of sustained AID expression, B cell proliferation, ongoing CSR, and production of human IgG ACPA from GC+ synovial tissue transplanted into SCID mice, independently of new B cell influx from the systemic circulation. These data identify AID as a potential therapeutic target in RA and suggest that survival of functional synovial B cell niches may profoundly influence chronic inflammation, autoimmunity, and response to B cell-depleting therapies.

Ectopic lymphoid structures support ongoing production of class-switched autoantibodies in rheumatoid synovium

BACKGROUND

Follicular structures resembling germinal centres (GCs) that are characterized by follicular dendritic cell (FDC) networks have long been recognized in chronically inflamed tissues in autoimmune diseases, including the synovium of rheumatoid arthritis (RA). However, it is debated whether these ectopic structures promote autoimmunity and chronic inflammation driving the production of pathogenic autoantibodies. Anti-citrullinated protein/peptide antibodies (ACPA) are highly specific markers of RA, predict a poor prognosis, and have been suggested to be pathogenic. Therefore, the main study objectives were to determine whether ectopic lymphoid structures in RA synovium: (i) express activation-induced cytidine deaminase (AID), the enzyme required for somatic hypermutation and class-switch recombination (CSR) of Ig genes; (ii) support ongoing CSR and ACPA production; and (iii) remain functional in a RA/severe combined immunodeficiency (SCID) chimera model devoid of new immune cell influx into the synovium.

METHODS AND FINDINGS

Using immunohistochemistry (IHC) and quantitative Taqman real-time PCR (QT-PCR) in synovial tissue from 55 patients with RA, we demonstrated that FDC+ structures invariably expressed AID with a distribution resembling secondary lymphoid organs. Further, AID+/CD21+ follicular structures were surrounded by ACPA+/CD138+ plasma cells, as demonstrated by immune reactivity to citrullinated fibrinogen. Moreover, we identified a novel subset of synovial AID+/CD20+ B cells outside GCs resembling interfollicular large B cells. In order to gain direct functional evidence that AID+ structures support CSR and in situ manufacturing of class-switched ACPA, 34 SCID mice were transplanted with RA synovium and humanely killed at 4 wk for harvesting of transplants and sera. Persistent expression of AID and Igamma-Cmu circular transcripts (identifying ongoing IgM-IgG class-switching) was observed in synovial grafts expressing FDCs/CD21L. Furthermore, synovial mRNA levels of AID were closely associated with circulating human IgG ACPA in mouse sera. Finally, the survival and proliferation of functional B cell niches was associated with persistent overexpression of genes regulating ectopic lymphoneogenesis.

CONCLUSIONS

Our demonstration that FDC+ follicular units invariably express AID and are surrounded by ACPA-producing plasma cells provides strong evidence that ectopic lymphoid structures in the RA synovium are functional and support autoantibody production. This concept is further confirmed by evidence of sustained AID expression, B cell proliferation, ongoing CSR, and production of human IgG ACPA from GC+ synovial tissue transplanted into SCID mice, independently of new B cell influx from the systemic circulation. These data identify AID as a potential therapeutic target in RA and suggest that survival of functional synovial B cell niches may profoundly influence chronic inflammation, autoimmunity, and response to B cell-depleting therapies.

H-2g, a glucose analog of blood group H antigen, mediates mononuclear cell recruitment via Src and phosphatidylinositol 3-kinase pathways

OBJECTIVE

Monocyte recruitment by proinflammatory cytokines is a hallmark of rheumatoid arthritis (RA). Lewis(y-6) and H (Le(y)/H) are blood group antigens up-regulated on RA synovial endothelium. We have previously shown that both soluble Le(y)/H and a glucose analog of H, H-2g, are angiogenic and mediateleukocyte-endothelial adhesion via induction of intercellular adhesion molecule 1. We hypothesized that soluble Le(y)/H plays an important role in monocyte recruitment in RA.

METHODS

We examined the role of H-2g in monocyte chemotaxis in vitro. We used an RA synovial tissue (ST)-SCID mouse chimera model to evaluate the role of H-2g in monocyte recruitment in vivo. We used Western blots to examine signaling molecules activated by H-2g in monocytes.

RESULTS

H-2g induced human monocyte migration in vitro, which was mediated by Src and phosphatidylinositol 3-kinase (PI 3-kinase), since inhibitors and antisense oligodeoxynucleotides (ODNs) of Src and PI 3-kinase significantly decreased H-2g-induced monocyte migration (P < 0.05). H-2g significantly increased mononuclear cell (MNC) homing in vivo into an RA ST-SCID mouse chimera (P < 0.05). Transfection of MNCs with Src antisense ODNs blocked H-2g-induced MNC recruitment into the RA ST-SCID mouse chimera. Additionally, H-2g induced marked phosphorylation of protein kinase CalphaI/betaII (PKCalphaI/betaII), Src, IkappaBalpha, and Akt in monocytes. Src, Akt, and NF-kappaB were shown to be downstream targets of PKCalphaI/betaII, since an inhibitor of PKCalphaI/betaII reduced H-2g-mediated phosphorylation of Src, Akt, and NF-kappaB in monocytes.

CONCLUSION

These data suggest that H-2g may be a novel mediator of monocyte recruitment in chronic inflammatory diseases like RA.

Co-expression of IL-18 binding protein and IL-4 regulates Th1/Th2 cytokine response in murine collagen-induced arthritis

We constructed a recombinant adenoviral vector containing a murine interleukin (IL)-18 binding protein (mIL-18BP) and murine IL-4 (mIL-4) fusion gene (AdmIL-18BP/mIL-4) and used a gene therapy approach to investigate the role of IL-18BP and IL-4 in modulating the T-helper1 and T-helper2 (Th1/Th2) balance in mice with collagen-induced arthritis (CIA). Mice with CIA were intra-articularly injected with 107 pfu/6 microl of either AdmIL-18BP/mIL-4, or a control adenovirus, or with the control vehicle (phosphate-buffered saline). After intra-articular gene therapy with AdmIL-18BP/mIL-4, the serum levels of tumor necrosis factor-alpha (TNF-alpha), gamma-interferon (IFN-gamma), IL-4, IL-10, and IL-18 in mice with CIA were assessed by ELISA. IFN-gamma-expressing and IL-4-expressing CD4+ T cells from mice splenocytes were monitored by flow cytometry. Mice with CIA at weeks 1, 2, and 4 after intra-articular injection of AdmIL-18BP/mIL-4 showed significantly increased serum concentrations of IL-4 and IL-10 (P<0.01 at all time points) but greatly decreased serum concentrations of IFN-gamma, TNF-alpha, and IL-18 (P<0.01 at all time points) compared to both the control adenovirus and phosphate-buffered saline control groups. The percentage of IFN-gamma-producing CD4+ T cells was significantly decreased in response to local AdmIL-18BP/mIL-4 treatment. The percentage of IL-4-producing CD4+ T cells increased significantly at 1 week after local injection of AdmIL-18BP/mIL-4 then returned to normal by week 4. These data indicated the significant modifying effects on the Th1/Th2 imbalance in murine CIA produced by local overexpression of IL-18BP and IL-4. Combination treatment with IL-18BP and IL-4 is a promising potential therapy for rheumatoid arthritis.

Humanized SCID mouse models for biomedical research

There is a growing need for effective animal models to carry out experimental studies on human hematopoietic and immune systems without putting individuals at risk. Progress in development of small animal models for the in vivo investigation of human hematopoiesis and immunity has seen three major breakthroughs over the last three decades. First, CB 17-Prkdc(scid) (abbreviated CB 17-scid) mice were discovered in 1983, and engraftment of these mice with human fetal tissues (SCID-Hu model) and peripheral blood mononuclear cells (Hu-PBL-SCID model) was reported in 1988. Second, NOD-scid mice were developed and their enhanced ability to engraft with human hematolymphoid tissues as compared with CB17-scid mice was reported in 1995. NOD-scid mice have been the "gold standard" for studies of human hematolymphoid engraftment in small animal models over the last 10 years. Third, immunodeficient mice bearing a targeted mutation in the IL-2 receptor common gamma chain (IL2rgamma(null)) were developed independently by four groups between 2002 and 2005, and a major increase in the engraftment and function of human hematolymphoid cells as compared with NOD-scid mice has been reported. These new strains of immunodeficient IL2rgamma(null) mice are now being used for studies in human hematopoiesis, innate and adaptive immunity, autoimmunity, infectious diseases, cancer biology, and regenerative medicine. In this chapter, we discuss the current state of development of these strains of mice, the remaining deficiencies, and how approaches used to increase the engraftment and function of human hematolymphoid cells in CB 17-scid mice and in previous models based on NOD-scid mice may enhance human hematolymphoid engraftment and function in NOD-scid IL2rgamma(null) mice.

Differentiating the new rheumatoid arthritis biologic therapies

Current understanding of the mechanisms behind the pathogenesis of rheumatoid arthritis (RA) has led to the development of therapies involving biologic agents that target specific mediators of the disease process. Although the biologic agents used to treat RA share the ability to alter the cytokine cascade, they differ in ways that are clinically important. For example, they vary with regard to how they block cytokine activity (ie, as receptors, as receptor blockers, or as anticytokine antibodies) and the particular cytokine they target (eg, tumor necrosis factor [TNF] versus interleukin-1). Biologic therapies for RA also differ in mode of administration. Several are administered subcutaneously, whereas others are given intravenously. They also have molecular dissimilarities that result in differences in pharmacokinetics (ie, long versus medium half-life) and that may influence their safety profiles.Some biologic agents, such as the TNF inhibitors etanercept and infliximab, have been rigorously examined for long-term safety and efficacy, whereas other agents, like the TNF inhibitor adalimumab, have not. Differences between the various biologic agents may relate to the usefulness of each individual drug as a long-term treatment in RA. For example, the need for physician visits may impact the practicality of drugs that are administered intravenously. Also, physicians should be aware that use of cytokine inhibitors increases the risk of infection. The prevalence of tuberculosis during therapy with infliximab exceeds the background rate in patients with RA. Accordingly, physicians should be familiar with the updated warnings in the package inserts that accompany these drugs.

Interleukin-21 induces T-cell activation and proinflammatory cytokine secretion in rheumatoid arthritis

Interleukin (IL)-21 is a CD4+ T-cell-derived cytokine, which is involved in innate and adaptive immune response. In this study, we analysed IL-21 receptor (IL-21R) expression in peripheral blood and synovial fluid mononuclear cells, and investigated the role of IL-21 in the induction of proinflammatory cytokine production by peripheral blood T cells (PB-T) and synovial fluid T cells (SF-T) from patients with rheumatoid arthritis (RA). Immunohistochemical staining demonstrated that IL-21R-positive cells were significantly increased in inflamed synovial tissues of RA patients compared with osteoarthritis (OA) and healthy controls. Flow cytometric analysis confirmed that IL-21R was mainly expressed in freshly isolated CD4, CD8, B and NK cells from peripheral blood and synovial fluid, but decreased gradually in T cells 24 h after anti-CD3 stimulation. PB- and SF-T cells from RA patients were more responsive to IL-21 when compared with controls. Importantly, isolated PB- or SF-T cells from RA patients, when stimulated with IL-21 and anti-CD3 MoAb, secreted markedly higher levels of TNF-alpha and IFN-gamma than controls. These data indicate that IL-21R is overexpressed in the inflamed synovial membrane and in peripheral blood or synovial fluid leukocytes of RA patients, and that IL-21 enhances local T-cell activation, proliferation and proinflammatory cytokine secretion. Thus, blockade of IL-21R signalling pathway may have a therapeutic potential in acute RA patients.

Gene therapy as a therapeutic approach for the treatment of rheumatoid arthritis: innovative vectors and therapeutic genes

In recent years, significant progress has been made in the treatment of rheumatoid arthritis (RA). In addition to conventional therapy, novel biologicals targeting tumour necrosis factor-alpha have successfully entered the clinic. However, the majority of the patients still has some actively inflamed joints and some patients suffer from side-effects associated with the high systemic dosages needed to achieve therapeutic levels in the joints. In addition, due to of the short half-life of these proteins there is a need for continuous, multiple injections of the recombinant protein. An alternative approach might be the use of gene transfer to deliver therapeutic genes locally at the site of inflammation. Several viral and non-viral vectors are being used in animal models of RA. The first gene therapy trials for RA have already entered the clinic. New vectors inducing long-term and regulated gene expression in specific tissue are under development, resulting in more efficient gene transfer, for example by using distinct serotypes of viral vectors such as adeno-associated virus. This review gives an overview of some promising vectors used in RA research. Furthermore, several therapeutic genes are discussed that could be used for gene therapy in RA patients.

Upregulation of transforming growth factor-beta1 and vascular endothelial growth factor in cultured keloid fibroblasts: relevance to angiogenic activity

Keloids are tumor-like lesions that result from excessive scar formation during healing of wounds. Histologically, keloids show an increased blood vessel density compared with normal dermis or normal scars. However, the angiogenic activity of keloid fibroblasts remains unknown. In this study, we investigated angiogenic activity of keloid fibroblasts. Transforming growth factor-beta1 (TGF-beta1) and vascular endothelial growth factor (VEGF) were investigated as elements of the angiogenic factors. Expressions of TGF-beta1 and VEGF in conditioned medium were measured with enzyme-linked immunosorbent assay (EIA) and Northern blot analysis. Participation of TGF-beta1 in the production of VEGF was also investigated with addition of TGF-beta1 and a neutralizing anti-TGF-beta1 antibody. A modified Boyden chamber assay was performed to assess the chemotactic activity of vascular endothelial cells. Angiogenic activity in vivo was evaluated by neovascularization of nodules formed by implantation of fibroblasts into severe combined immunodeficiency (SCID) mice. EIA showed that the concentrations of TGF-beta1 and VEGF in conditioned medium were increased 2.5- and 6-fold, respectively, after the culture of keloid fibroblasts compared with normal fibroblasts. Northern blot analysis revealed that the expression of TGF-beta1 and VEGF mRNA was upregulated 3.6- and 6-fold, respectively, in keloid fibroblasts compared with normal fibroblasts. Addition of TGF-beta1 to keloid fibroblast cultures increased VEGF production by 3.5-fold, while there was a 6-fold in culture of normal fibroblasts. A neutralizing anti-TGF-beta1 antibody reduced VEGF secretion to control levels, suggesting that TGF-beta1 mediated the upregulation of VEGF expression. A modified Boyden chamber assay demonstrated that the chemotactic activity of vascular endothelial cells was more strongly (sevenfold) induced by keloid fibroblast-conditioned medium than by normal fibroblast-conditioned medium. Anti-VEGF antibody inhibited chemotaxis to basal levels. When SCID mice underwent implantation of fibroblasts into the back, the nodules formed by keloid fibroblasts were three times larger than those formed by normal fibroblasts. Although abundant neovascularization was observed in keloid fibroblast nodules, neovascularization was scarce in normal fibroblast nodules. Both in vitro and in vivo studies confirmed the significantly higher angiogenic activity of keloid fibroblasts compared with normal fibroblasts, and TGF-beta1 and VEGF were clearly shown to be involved. These results suggest that angiogenesis in keloids is promoted by endogenous TGF-beta1 and VEGF.

Isolating ligands specific for human vasculature using in vivo phage selection

The endothelium lining blood vessels expresses molecules that are restricted in their expression to a particular tissue or organ. These molecules are attractive targets for therapy and diagnosis because they allow agents to be delivered specifically to the blood vessels supplying the desired tissue. However, it is difficult to identify these tissue-specific molecules because endothelium loses much of its tissue-specific nature when it is removed from the organ. This can be overcome by using in vivo phage selection - injecting libraries of phage bearing antibodies or peptides into an animal and isolating phage that bind to the relevant tissue. A variation on this approach, in which in vivo phage selection is performed in animals bearing human tissue xenografts, allows the isolation of peptides (and presumably other molecules) specific for human vasculature.

NF-kappaB-dependent lymphocyte hyperadhesiveness to synovial fibroblasts by hypoxia and reoxygenation: potential role in rheumatoid arthritis

Hypoxia/reoxygenation has been incriminated as a major factor in the pathogenesis of ischemia/reperfusion injury in various ischemic diseases such as rheumatoid arthritis (RA). In this study, we have investigated the effect of hypoxia/reoxygenation on the expression of intercellular adhesion molecule-1 (ICAM-1) in synovial fibroblasts and adherence of lymphocytes to synovial fibroblasts. Hypoxia/reoxygenation strongly activated nuclear factor-kappaB (NF-kappaB) in synovial fibroblasts to the levels produced by phorbol 12-myristate 13-acetate and caused lymphocyte hyperadhesiveness to synovial fibroblasts as well as up-regulation of ICAM-1, both of which were completely blocked by a NF-kappaB antagonist (pyrrolidine dithiocarbamate). These results indicate that hypoxia/reoxygenation has a major role in sequestration of inflammatory cells to synovium mediated by the activation of NF-kappaB. Our data suggest that hypoxia/reoxygenation could be an important target for the development of new, therapeutic strategies in RA.

Annexin 1 modulates monocyte-endothelial cell interaction in vitro and cell migration in vivo in the human SCID mouse transplantation model

The effect of the glucocorticoid inducible protein annexin 1 (ANXA1) on the process of monocytic cell migration was studied using transfected U937 cells expressing variable protein levels. An antisense (AS) (36.4AS; approximately 50% less ANXA1) and a sense (S) clone (15S; overexpressing the bioactive 24-kDa fragment) together with the empty plasmid CMV clone were obtained and compared with wild-type U937 cells in various models of cell migration in vitro and in vivo. 15S-transfected U937 cells displayed a reduced (50%) degree of trans-endothelial migration in response to stromal cell-derived factor-1alpha (CXC chemokine ligand 12 (CXCL12)). In addition, the inhibitory role of endogenous ANXA1 on U937 cell migration in vitro was confirmed by the potentiating effect of a neutralizing anti-ANXA1 serum. Importantly, overexpression of ANXA1 in clone 15S inhibited the extent of cell migration into rheumatoid synovial grafts transplanted into SCID mice. ANXA1 inhibitory effects were not due to modifications in adhesion molecule or CXCL12 receptor (CXCR4) expression as shown by the similar amounts of surface molecules found in transfected and wild-type U937 cells. Likewise, an equal chemotactic response to CXCL12 in vitro excluded an intrinsic defect in cell motility in clones 15S and 36.4AS. These data strongly support the notion that ANXA1 critically interferes with a leukocyte endothelial step essential for U937 cell, and possibly monocyte, transmigration both in vitro and in vivo.

Identification of synovium-specific homing peptides by in vivo phage display selection

OBJECTIVE

To identify homing peptides specific for human synovium that could be used as targeting devices for delivering therapeutic/diagnostic agents to human joints.

METHODS

Human synovium and skin were transplanted into SCID mice. A disulfide-constrained 7-amino acid peptide phage display library was injected intravenously into the animals and synovial homing phage recovered from synovial grafts. Following 3-4 cycles of enrichment, DNA sequencing of homing phage clones allowed the identification of specific peptides that were synthesized by a-fluorenylmethyloxycarbonyl chemistry and used in competitive in vivo assays and immunohistochemistry analyses.

RESULTS

We isolated synovial homing phages displaying specific peptides that distinctively bound to synovial but not skin or mouse microvascular endothelium (MVE). They retained their tissue homing specificity in vivo, independently from the phage component, the original pathology of the transplanted tissue, and the degree of human/murine graft vascularization. One such peptide (CKSTHDRLC) maintained synovial homing specificity both when presented by the phage and as a free synthetic peptide. The synthetic peptide also competed with and inhibited in vivo the binding of the parent phage to the cognate synovial MVE ligand.

CONCLUSION

This is the first report describing peptides with homing properties specific for human synovial MVE. This was demonstrated using a novel approach targeting human tissues, transplanted into SCID mice, directly by in vivo phage display selection. The identification of such peptides opens the possibility of using these sequences to construct joint-specific drug delivery systems that may have considerable impact in the treatment of arthritic conditions.

Stromal cell-derived factor 1 (CXCL12) induces human cell migration into human lymph nodes transplanted into SCID mice

Stromal cell-derived factor 1 (SDF-1; CXCL12), a CXC chemokine, has a primary role in signaling the recruitment of hemopoietic stem cell precursors to the bone marrow during embryonic development. In postnatal life, SDF-1 is widely expressed and is induced in chronically inflamed tissues such as psoriatic skin and the rheumatoid synovium, but has also been implicated in the migration of lymphocytes to lymphoid organs. To investigate the role of SDF-1 in recirculation and homing in vivo, we have developed a model in which human peripheral lymph nodes (huPLN) are transplanted into SCID mice. We have shown that huPLN transplants are viable, vascularized by the murine circulation that forms functional anastomoses with transplant vessels. In addition, grafts retain some features of the pretransplantation tissue, such as lymphoid follicles, lymphatic and high endothelial venule markers. We also show that SDF-1 is capable of inducing the migration of a SDF-1-responsive cell line (U937) and human PBLs from the murine circulation into the grafts in a dose-dependent manner, inhibitable by CXCR4 blockade. The mechanism of action of SDF-1 in this model is independent from that of TNF-alpha and does not rely on the up-regulation of adhesion molecules (such as ICAM-1) on the graft vascular endothelium. This is the first description of huPLN transplantation into SCID mice and of the functional effects of SDF-1 in regard to the migration of human cells into huPLN in vivo. This model provides a powerful tool to investigate the pathways involved in cell migration into lymphoid organs and potentially to target them for therapeutic purposes.

Stromal cell-derived factor 1 (CXCL12) induces monocyte migration into human synovium transplanted onto SCID Mice

OBJECTIVE

The mechanisms by which monocyte/macrophage cells migrate to the joint involve a series of integrated adhesion and signaling events in which chemokines and their receptors are strongly implicated. This study was undertaken to investigate the hypothesis that stromal cell-derived factor 1 (SDF-1), a CXC chemokine (CXCL12), plays a critical role in monocyte/macrophage localization to synovium.

METHODS

SDF-1 and CXC receptor 4 (CXCR4) expression in rheumatoid arthritis (RA) and osteoarthritis synovium and graft SDF-1, tumor necrosis factor alpha (TNF alpha), and human and murine vascular markers were examined by immunohistochemistry and double-immunofluorescence. The functional capacity of SDF-1 to modulate monocyte migration into joints was investigated by examining the localization of pro-myelomonocytic U937 cells into synovial tissue transplanted into SCID mice. SDF-1, TNF alpha, or saline was injected into graft sites and response determined by the number of fluorescently labeled U937 cells (injected intravenously) detected in grafts by ultraviolet microscopy.

RESULTS

SDF-1 and CXCR4 were highly expressed in CD68+ cells in the RA synovium. SDF-1 induced U937 cell migration in vitro and in vivo in a dose-dependent manner and, in vivo, SDF-1 was more effective than TNF alpha. In contrast to TNF alpha, SDF-1 did not induce intracellular adhesion molecule 1 in transplant microvasculature. Furthermore, intragraft injection of SDF-1 did not up-regulate TNF alpha, or vice versa.

CONCLUSION

This study demonstrates, for the first time, that SDF-1 is functional in vivo when injected into synovial grafts. In addition, SDF-1 is more potent than TNF alpha, and its mechanisms of action appear to be autonomous. Therefore, SDF-1 may be an important TNF-independent molecule involved in the migration to and retention of inflammatory effector cells in the joint.

The role of TNF-alpha in the pathogenesis of inflammation and joint destruction in rheumatoid arthritis (RA): a study using a human RA/SCID mouse chimera

OBJECTIVE

In order to elucidate which cytokine preferentially stimulates the synovium in patients with rheumatoid arthritis (RA), we investigated the roles of tumour necrosis factor alpha (TNF-alpha) and interleukin 6 (IL-6) using SCID mice engrafted with human RA tissue (SCID-HuRAg).

METHODS

The SCID-HuRAg mice were prepared according to our previously described method. First, SCID-HuRAg mice were treated with chimeric anti-TNF-alpha monoclonal antibody (mAb, 100 microg/mouse) and histological changes were examined 4 weeks after the initial treatment. Secondly, a total of 100 microg of recombinant TNF-alpha or IL-6 (0.6 microg/h) was administered daily to mice using an osmium pump. The histological changes and serum cytokine levels were examined 4 weeks after the initial administration. Human immunoglobulin G (IgG) was administered to mice as a control.

RESULTS

Synovial inflammatory cells were significantly decreased after the anti-TNF-alpha mAb treatment; conversely, the degree of synovial inflammation was significantly exacerbated by TNF-alpha administration. The levels of both IL-6 and TNF-alpha in sera were significantly increased by recombinant TNF-alpha administration, while TNF-alpha levels were unchanged by IL-6 administration. This suggests that TNF-alpha controls IL-6 production. Despite the profound changes in inflammation, we found no effects on bone and no articular cartilage damage was produced by TNF-alpha.

CONCLUSION

This study provides strong evidence that TNF-alpha is a key molecule in the control of the inflammatory changes that occur in the RA synovium. In addition, TNF-alpha regulates IL-6 production. However, other inflammatory pathways independent of TNF-alpha may contribute to the bone and cartilage damage seen in RA.

Inflammation, immune reactivity, and angiogenesis in a severe combined immunodeficiency model of rheumatoid arthritis

Severe combined immunodeficiency (SCID) mice were engrafted with rheumatoid arthritis (RA) synovium and evaluated to determine whether RA synovial morphology and function were maintained in the RA-SCID grafts. The four major components of RA synovitis, inflammation, immune reactivity, angiogenesis, and synovial hyperplasia persisted in RA-SCID grafts for 12 weeks. Retention of chronic inflammatory infiltrates was demonstrated by histological evaluation and by immunohistology for CD3, CD20, and CD68. Staining for CD68 also revealed that the grafts had undergone reorganization of the tissue, possibly as a result of fibroblast hyperplasia. Immune and inflammatory components were confirmed by the detection of human immunoglobulins and human interleukin-6 in serum samples obtained from grafted animals. Human blood vessels were detected by dense expression of CD31. Small vessels persistently expressed the vitronectin receptor, alpha v beta 3, a marker of angiogenesis. All vessels expressed VAP-1, a marker of activated endothelial cells. Finally, the grafts retained the ability to support immigration by human leukocytes, as demonstrated by the functional capacity to recruit adoptively transferred 5- (and -6)-carboxyfluorescein diacetate succinimidyl ester-labeled T cells. T cells entering the RA-SCID grafts became activated and produced interferon-gamma, as detected by reverse transcriptase-polymerase chain reaction analysis. These studies demonstrate that the RA-SCID model maintains many of the phenotypic and functional features of the inflamed RA synovium.