Sjögren's syndrome-like disease of C57BL/6.NOD-Aec1 Aec2 mice: gender differences in keratoconjunctivitis sicca defined by a cross-over in the chromosome 3 Aec1 locus

Altered characteristics of regulatory T cells in target tissues of Sjögren's syndrome in murine models

Sjӧgren's syndrome (SS), also known as Sjögren's disease, is a chronic autoimmune condition predominantly affecting the salivary and lacrimal glands. The disease is driven by autoimmune responses involving the activation and actions of major innate- and adaptive immune cell subsets. However, the specific characteristics and roles of regulatory T cells (Tregs) in SS remain elusive. This study seeks to clarify the main phenotypic and functional attributes of Tregs in the salivary glands and their draining lymph nodes in murine models of SS. Our flow cytometric analysis revealed that Tregs in the salivary gland-draining lymph nodes of female non-obese diabetic (NOD) mice, a spontaneous model of SS, exhibited a greater proportion of activated Tregs and fewer resting Tregs compared to Balb/c mice. Furthermore, Tregs from the salivary gland-draining lymph nodes of female C57BL/6.NOD-Aec1Aec2 (B6.NOD-Aec) mice, a model for primary SS, demonstrated significantly lower IL-10 production but markedly higher IFNγ- and IL-17 production than their C57BL/6 counterparts. Additionally, treatment of C57BL/6 Tregs with IL-7, a cytokine critical for SS pathogenesis, resulted in diminished IL-10 production and enhanced IFNγ and IL-17 production in these cells. Notably, the alterations in B6.NOD-Aec Tregs also included an increased expression of the immune-inhibitory molecule CTLA-4 compared to the C57BL/6 Tregs. Intriguingly, in vitro co-cultures of Tregs with conventional CD4 T cells and other key immune populations from lymph nodes indicated that Tregs from salivary gland-draining lymph nodes of both B6.NOD-Aec and C57BL/6 strains exhibited comparable and limited immunosuppressive effects on the proliferation and function of conventional CD4 T cells. The ability of B6.NOD-Aec Tregs to directly inflict damages to salivary gland epithelial tissues and contribute to SS pathologies through IFNγ and IL-17 that they produce warrants further investigations. In addition, enhancing the relatively weak immunosuppressive capacities of these Tregs may also serve as a viable strategy to alleviate the SS phenotype in the mouse models and potentially in patients.

Current experimental methods to investigate the impact of specialized pro-resolving lipid mediators on Sjögren's syndrome

Sjögren's syndrome is a chronic inflammatory autoimmune disease characterized by diminished secretory function of the exocrine glands. Although extensive investigation has been done to understand Sjögren's syndrome, the causes of the disease are as yet unknown and treatments remain largely ineffective, with established therapeutic interventions being limited to use of saliva substitutes with modest effectiveness. A primary feature of Sjögren's syndrome is uncontrolled inflammation of exocrine tissues and previous studies have demonstrated that lipid-based specialized pro-resolving mediators reduce inflammation and restores tissue integrity in salivary glands. However, these studies are limited to a single specialized pro-resolving lipid mediator's family member resolvin D1 or RvD1 and its aspirin-triggered epimer, AT-RvD1. Consequently, additional studies are needed to explore the potential benefits of other members of the specialized pro-resolving lipid mediator's family and related molecules (e.g., additional resolvin subtypes as well as lipoxins, maresins and protectins). In support of this goal, the current review aims to briefly describe the range of current experimental methods to investigate the impact of specialized pro-resolving lipid mediators on Sjögren's syndrome, including both strengths and weaknesses of each approach where this information is known. With this article, the possibilities presented by specialized pro-resolving lipid mediators will be introduced to a wider audience in immunology and practical advice is given to researchers who may wish to take up this work.

GABA Administration Ameliorates Sjogren’s Syndrome in Two Different Mouse Models

Sjögren’s syndrome (SS) is a chronic autoimmune disease characterized by lymphocytic infiltrates in the salivary and lachrymal glands resulting in oral and ocular dryness. There are no clinically approved therapies to slow the progression of SS. Immune cells possess receptors for the neurotransmitter GABA (GABA-Rs) and their activation has immunoregulatory actions. We tested whether GABA administration has potential for amelioration of SS in NOD.B10-H2^b and C57BL/6.NOD-Aec1Aec2 mice, two spontaneous SS models. Oral GABA treatment was initiated (1) after the development of sialadenitis but before the onset of overt symptoms, or (2) after the appearance of overt symptoms. When assessed weeks later, GABA-treated mice had greater saliva and tear production, as well as quicker times to salvia flow, in both SS mouse models. This was especially evident when GABA treatment was initiated after the onset of overt disease. This preservation of exocrine function was not accompanied by significant changes in the number or area of lymphocytic foci in the salivary or lachrymal glands of GABA-treated mice and we discuss the possible reasons for these observations. Given that GABA-treatment preserved saliva and tear production which are the most salient symptoms of SS and is safe for consumption, it may provide a new approach to help ameliorate SS.

Experimental Models, Induction Protocols, and Measured Parameters in Dry Eye Disease: Focusing on Practical Implications for Experimental Research

Dry eye disease (DED) is one of the major ophthalmological healthcare challenges worldwide. DED is a multifactorial disease characterized by a loss of homeostasis of the tear film, and its main pathogenesis is chronic ocular surface inflammation related with various cellular and molecular signaling cascades. The animal model is a reliable and effective tool for understanding the various pathological mechanisms and molecular cascades in DED. Considerable experimental research has focused on developing new strategies for the prevention and treatment of DED. Several experimental models of DED have been developed, and different animal species such as rats, mice, rabbits, dogs, and primates have been used for these models. Although the basic mechanisms of DED in animals are nearly identical to those in humans, proper knowledge about the induction of animal models is necessary to obtain better and more reliable results. Various experimental models (in vitro and in vivo DED models) were briefly discussed in this review, along with pathologic features, analytical approaches, and common measurements, which will help investigators to use the appropriate cell lines, animal, methods, and evaluation parameters depending on their study design.

Studying Sjögren's syndrome in mice: What is the best available model?

Sjögren's syndrome (SS) is a common autoimmune disease characterized by lymphocytic infiltration and destruction of exocrine glands. The disease manifests primarily in the salivary and lacrimal glands, but other organs are also involved, leading to dry mouth, dry eyes, and other extra-glandular manifestations. Studying the disease in humans is entailed with many limitations and restrictions; therefore, the need for a proper mouse model is mandatory. SS mouse models are categorized, depending on the disease emergence into spontaneous or experimentally manipulated models. The usefulness of each mouse model varies depending on the SS features exhibited by that model; each SS model has advanced our understanding of the disease pathogenesis. In this review article, we list all the available murine models which have been used to study SS and we comment on the characteristics exhibited by each mouse model to assist scientists to select the appropriate model for their specific studies. We also recommend a murine strain that is the most relevant to the ideal SS model, based on our experience acquired during previous and current investigations.

Early Covert Appearance of Marginal Zone B Cells in Salivary Glands of Sjögren's Syndrome-Susceptible Mice: Initiators of Subsequent Overt Clinical Disease

The C57BL/6.NOD-Aec1Aec2 mouse model has been extensively studied to define the underlying cellular and molecular bioprocesses critical in the onset of primary Sjögren’s Syndrome (pSS), a human systemic autoimmune disease characterized clinically as the loss of lacrimal and salivary gland functions leading to dry eye and dry mouth pathologies. This mouse model, together with several gene knockout mouse models of SS, has indicated that B lymphocytes, especially marginal zone B (MZB) cells, are necessary for development and onset of clinical manifestations despite the fact that destruction of the lacrimal and salivary gland cells involves a classical T cell-mediated autoimmune response. Because migrations and functions of MZB cells are difficult to study in vivo, we have carried out ex vivo investigations that use temporal global RNA transcriptomic analyses to profile autoimmunity as it develops within the salivary glands of C57BL/6.NOD-Aec1Aec2 mice. Temporal profiles indicate the appearance of Notch2-positive cells within the salivary glands of these SS-susceptible mice concomitant with the early-phase appearance of lymphocytic foci (LF). Data presented here identify cellular bioprocesses occurring during early immune cell migrations into the salivary glands and suggest MZB cells are recruited to the exocrine glands by the upregulated Cxcl13 chemokine where they recognize complement (C’)-decorated antigens via their sphingosine-1-phosphate (S1P) and B cell (BC) receptors. Based on known MZB cell behavior and mobility, we propose that MZB cells activated in the salivary glands migrate to splenic follicular zones to present antigens to follicular macrophages and dendritic cells that, in turn, promote a subsequent systemic cell-mediated and autoantibody-mediated autoimmune T cell response that targets exocrine gland cells and functions. Overall, this study uses the power of transcriptomic analyses to provide greater insight into several molecular events defining cellular bioprocesses underlying SS that can be modelled and more thoroughly studied at the cellular level.

Small RNA Deep Sequencing Identifies a Unique miRNA Signature Released in Serum Exosomes in a Mouse Model of Sjögren's Syndrome

Sjögren's Syndrome (SS) is an autoimmune disease characterized by lymphocytic infiltration and loss of function of moisture-producing exocrine glands as well as systemic inflammation. SS diagnosis is cumbersome, subjective and complicated by manifestation of symptoms that overlap with those of other rheumatic and ocular diseases. Definitive diagnosis averages 4–5 years and this delay may lead to irreversible tissue damage. Thus, there is an urgent need for diagnostic biomarkers for earlier detection of SS. Extracellular vesicles called exosomes carry functional small non-coding RNAs which play a critical role in maintaining cellular homeostasis via transcriptional and translational regulation of mRNA. Alterations in levels of specific exosomal miRNAs may be predictive of disease status. Here, we have assessed serum exosomal RNA using next generation sequencing in a discovery cohort of the NOD mouse, a model of early-intermediate SS, to identify dysregulated miRNAs that may be indicative of SS. We found five miRNAs upregulated in serum exosomes of NOD mice with an adjusted p < 0.05—miRNA-127-3p, miRNA-409-3p, miRNA-410-3p, miRNA-541-5p, and miRNA-540-5p. miRNAs 127-3p and 541-5p were also statistically significantly upregulated in a validation cohort of NOD mice. Pathway analysis and existing literature indicates that differential expression of these miRNAs may dysregulate pathways involved in inflammation. Future studies will apply these findings in a human cohort to understand how they are correlated with manifestations of SS as well as understanding their functional role in systemic autoimmunity specific to SS.

Recent Advances in Mouse Models of Sjögren's Syndrome

Sjögren's syndrome (SS) is a complex rheumatoid disease that mainly affects exocrine glands, resulting in xerostomia (dry mouth) and xerophthalmia (dry eye). SS is characterized by autoantibodies, infiltration into exocrine glands, and ectopic expression of MHC II molecules on glandular epithelial cells. In contrast to the well-characterized clinical and immunological features, the etiology and pathogenesis of SS remain largely unknown. Animal models are powerful research tools for elucidating the pathogenesis of human diseases. To date, many mouse models of SS, including induced models, in which disease is induced in mice, and genetic models, in which mice spontaneously develop SS-like disease, have been established. These mouse models have provided new insight into the pathogenesis of SS. In this review, we aim to provide a comprehensive overview of recent advances in the field of experimental SS.

Inhibition of bone morphogenetic protein 6 receptors ameliorates Sjögren's syndrome in mice

Primary Sjögren’s syndrome (pSS) is a chronic autoimmune disease, with only palliative treatments available. Recent work has suggested that increased bone morphogenetic protein 6 (BMP6) expression could alter cell signaling in the salivary gland (SG) and result in the associated salivary hypofunction. We examined the prevalence of elevated BMP6 expression in a large cohort of pSS patients and tested the therapeutic efficacy of BMP signaling inhibitors in two pSS animal models. Increased BMP6 expression was found in the SGs of 54% of pSS patients, and this increased expression was correlated with low unstimulated whole saliva flow rate. In mouse models of SS, inhibition of BMP6 signaling reduced phosphorylation of SMAD1/5/8 in the mouse submandibular glands, and led to a recovery of SG function and a decrease in inflammatory markers in the mice. The recovery of SG function after inhibition of BMP6 signaling suggests cellular plasticity within the salivary gland and a possibility for therapeutic intervention that can reverse the loss of function in pSS.

Testosterone Influence on Gene Expression in Lacrimal Glands of Mouse Models of Sjögren Syndrome

Purpose

Sjögren syndrome is an autoimmune disorder that occurs almost exclusively in women and is associated with extensive inflammation in lacrimal tissue, an immune-mediated destruction and/or dysfunction of glandular epithelial cells, and a significant decrease in aqueous tear secretion. We discovered that androgens suppress the inflammation in, and enhance the function of, lacrimal glands in female mouse models (e.g., MRL/MpJ-Tnfrsf6^lpr [MRL/lpr]) of Sjögren syndrome. In contrast, others have reported that androgens induce an anomalous immunopathology in lacrimal glands of nonobese diabetic/LtJ (NOD) mice. We tested our hypothesis that these hormone actions reflect unique, strain- and tissue-specific effects, which involve significant changes in the expression of immune-related glandular genes.

Methods

Lacrimal glands were obtained from age-matched, adult, female MRL/lpr and NOD mice after treatment with vehicle or testosterone for up to 3 weeks. Tissues were processed for analysis of differentially expressed mRNAs using CodeLink Bioarrays and Affymetrix GeneChips. Data were analyzed with bioinformatics and statistical software.

Results

Testosterone significantly influenced the expression of numerous immune-related genes, ontologies, and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways in lacrimal glands of MRL/lpr and NOD mice. The nature of this hormone-induced immune response was dependent upon the autoimmune strain, and was not duplicated within lacrimal tissues of nonautoimmune BALB/c mice. The majority of immune-response genes regulated by testosterone were of the inflammatory type.

Conclusions

Our findings support our hypothesis and indicate a major role for the lacrimal gland microenvironment in mediating androgen effects on immune gene expression.

Inhibition of Cathepsin S Reduces Lacrimal Gland Inflammation and Increases Tear Flow in a Mouse Model of Sjögren's Syndrome

Cathepsin S (CTSS) is highly increased in Sjögren's syndrome (SS) patients tears and in tears and lacrimal glands (LG) of male non-obese diabetic (NOD) mice, a murine model of SS. To explore CTSS's utility as a therapeutic target for mitigating ocular manifestations of SS in sites where CTSS is increased in disease, the tears and the LG (systemically), the peptide-based inhibitor, Z-FL-COCHO (Z-FL), was administered to 14-15 week male NOD mice. Systemic intraperitoneal (i.p.) injection for 2 weeks significantly reduced CTSS activity in tears, LG and spleen, significantly reduced total lymphocytic infiltration into LG, reduced CD3+ and CD68+ cell abundance within lymphocytic infiltrates, and significantly increased stimulated tear secretion. Topical administration of Z-FL to a different cohort of 14-15 week male NOD mice for 6 weeks significantly reduced only tear CTSS while not affecting LG and spleen CTSS and attenuated the disease-progression related reduction of basal tear secretion, while not significantly impacting lymphocytic infiltration of the LG. These findings suggest that CTSS inhibitors administered either topically or systemically can mitigate aspects of the ocular manifestations of SS.

Gene Expression Profiling of Lacrimal Glands Identifies the Ectopic Expression of MHC II on Glandular Cells as a Presymptomatic Feature in a Mouse Model of Primary Sjögren's Syndrome

Ectopic expression of MHC II molecules on glandular cells is a feature of primary Sjögren's syndrome (pSS). However, the cause of this ectopic expression and its potential role in the pathogenesis of the disease remains elusive. Here, we report that ectopic expression of MHC II molecules on glandular cells represents an early presymptomatic event in a mouse model of pSS induced by immunization of Ro60_316-335 peptide emulsified in TiterMax® as an adjuvant. Ectopic expression of MHC II was induced by TiterMax® but not by complete freund's adjuvant (CFA). Furthermore, immunization with Ro60_316-335 peptide emulsified in TiterMax®, but not in CFA, induced a pSS-like disease in mice. Our results suggests that ectopic expression of MHC II molecules on glandular cells represents a presymptomatic feature of pSS and that such ectopic expression can be induced by exogenous factors. In addition, this study also provides a novel mechanism how adjuvants can amplify immune responses.

TFOS DEWS II Sex, Gender, and Hormones Report

One of the most compelling features of dry eye disease (DED) is that it occurs more frequently in women than men. In fact, the female sex is a significant risk factor for the development of DED. This sex-related difference in DED prevalence is attributed in large part to the effects of sex steroids (e.g. androgens, estrogens), hypothalamic-pituitary hormones, glucocorticoids, insulin, insulin-like growth factor 1 and thyroid hormones, as well as to the sex chromosome complement, sex-specific autosomal factors and epigenetics (e.g. microRNAs). In addition to sex, gender also appears to be a risk factor for DED. "Gender" and "sex" are words that are often used interchangeably, but they have distinct meanings. "Gender" refers to a person's self-representation as a man or woman, whereas "sex" distinguishes males and females based on their biological characteristics. Both gender and sex affect DED risk, presentation of the disease, immune responses, pain, care-seeking behaviors, service utilization, and myriad other facets of eye health. Overall, sex, gender and hormones play a major role in the regulation of ocular surface and adnexal tissues, and in the difference in DED prevalence between women and men. The purpose of this Subcommittee report is to review and critique the nature of this role, as well as to recommend areas for future research to advance our understanding of the interrelationships between sex, gender, hormones and DED.

Multiple Roles for B-Lymphocytes in Sjogren's Syndrome

Sjogren’s syndrome (SS) is a complex heterogeneous autoimmune disease resulting in loss of salivary gland and lacrimal gland function that may include multiple systemic manifestations including lymphoma. Multiple cell types participate in disease pathogenesis. This review discusses evidence for abnormal B cell subpopulations in patients with SS, critical roles of B cells in SS and the status of B cell–directed therapies in the management of patients with SS.

Aquaporin gene therapy corrects Sjögren's syndrome phenotype in mice

Primary Sjögren's syndrome (pSS) is a chronic autoimmune disease that is estimated to affect 35 million people worldwide. Currently, no effective treatments exist for Sjögren's syndrome, and there is a limited understanding of the physiological mechanisms associated with xerostomia and hyposalivation. The present work revealed that aquaporin 5 expression, a water channel critical for salivary gland fluid secretion, is regulated by bone morphogenetic protein 6. Increased expression of this cytokine is strongly associated with the most common symptom of primary Sjögren's syndrome, the loss of salivary gland function. This finding led us to develop a therapy in the treatment of Sjögren's syndrome by increasing the water permeability of the gland to restore saliva flow. Our study demonstrates that the targeted increase of gland permeability not only resulted in the restoration of secretory gland function but also resolved the hallmark salivary gland inflammation and systemic inflammation associated with disease. Secretory function also increased in the lacrimal gland, suggesting this local therapy could treat the systemic symptoms associated with primary Sjögren's syndrome.

Sexual dimorphism in an animal model of Sjögren's syndrome: a potential role for Th17 cells

Sjögren's syndrome is a complex autoimmune disease with an array of diverse immunological, genetic and environmental etiologies, making identification of the precise autoimmune mechanism difficult to define. One of the most distinctive aspects of Sjögren's syndrome is the high sexual dimorphism with women affected 10-20 times more than men. It is nearly impossible to study the sexual dimorphic development of Sjögren's syndrome in human patients; therefore it is pertinent to develop an appropriate animal model which resembles human disease. The data indicated that female C57BL/6.NOD-Aec1Aec2 mice developed an earlier onset of sialadenitis with a higher composition of CD3⁺ T cells and a 10-fold increase in glandular infiltration of Th17 cells at the onset of clinical disease compared to male mice. Inflammatory Th17 cells of female mice exhibited a stronger proliferation in response to disease-specific antigen than their male counterpart. At the clinical disease stage, altered autoantibody patterns can be detected in females whereas they are seldom observed in male C57BL/6.NOD-Aec1Aec2 mice. Interestingly, male C57BL/6.NOD-Aec1Aec2 mice developed an earlier loss of secretory function, despite the fact that female C57BL/6.NOD-Aec1Aec2 mice exhibited a more rapid secretory loss. This data indicates the strong sexual dimorphism in the SjS-susceptible C57BL/6.NOD-Aec1Aec2 animal model, making it an appropriate animal model to examine human disease.

Summary: Sjogren's syndrome (SjS) is the one of the most common sexual dimorphic autoimmune diseases. This study demonstrates that female C57BL/6.NOD-Aec1Aec2 mice develop earlier onset and more severe symptoms of SjS than male counterparts. Therefore, the C57BL/6.NOD-Aec1Aec2 mouse model could be an appropriate model to study sexual dimorphism in SjS.

Age-Related Conjunctival Disease in the C57BL/6.NOD-Aec1Aec2 Mouse Model of Sjögren Syndrome Develops Independent of Lacrimal Dysfunction

PURPOSE

To investigate parameters of ocular surface disease in C57BL/6.NOD-Aec1Aec2 (Aec) mice with aging and their correlation with development of Sjögren syndrome (SS)-like lacrimal gland (LG) disease.

METHODS

Aec and C57BL/6 wild-type (B6) female mice were evaluated at 4, 12, and 20 weeks of age. Whole LG and eyes and adnexa were excised for histology and gene expression analysis and evaluated by flow cytometry and immunohistochemistry. Tear volume and goblet cell density was measured. Quantitative PCR evaluated T-cell-related cytokine expression in cornea and conjunctiva.

RESULTS

Both strains showed age-related conjunctival goblet cell loss that was more pronounced in the Aec strain and significantly greater than in B6 mice at 12 weeks. This was accompanied by CD4+ T-cell infiltration of the conjunctiva that was greater in Aec strain at 20 weeks. Aec mice had higher levels of IL-17A, IL-17R, IL-1α, IL-1β, and TNF-α in the conjunctiva, and they significantly increase with aging. Aec mice had greater lymphocytic infiltration of the LG and conjunctiva at 20 weeks that consisted of a mixture of CD4+ and CD8+ cells. Flow cytometry showed a significant increase in CD4+ T cells in Aec LG compared to B6 mice. Tear volume was significantly increased in both strains at 20 weeks.

CONCLUSIONS

Aec mice developed greater conjunctival goblet cell loss associated with lymphocytic infiltration of the LG and conjunctiva with aging. Increased expression of certain T helper or inflammatory cytokines in these tissues was observed in Aec mice. The conjunctival disease appeared to be due to inflammation and not a decrease in tear volume.

IL-17 sequestration via salivary gland gene therapy in a mouse model of Sjogren's syndrome suppresses disease-associated expression of the putative autoantigen Klk1b22

INTRODUCTION

IL-17 has a putative role in the pathophysiology of Sjogren's syndrome (SS) and has been shown to be upregulated in the salivary glands of affected individuals. Sequestration of IL-17 with Adenoviral-mediated gene therapy has previously shown a benefit upon the SS-like phenotype in the Aec1/Aec2 mouse model. We sought to understand the proteomic consequences of IL-17 sequestration in the salivary gland of this mouse model as a means of illuminating the role of IL-17 in SS-like disease.

METHODS

Ultrasound-assisted gene transfer (UAGT) was utilized to express a fusion protein composed of the extracellular portion of the IL-17 receptor fused to fragment of crystallization (Fc) in the submandibular glands of Aec1/Aec2 mice at 8 weeks of age. After confirming expression of the fusion protein and local and systemic sequestration of IL-17, proteomic profiling was performed on submandibular glands of a treated cohort of Aec1/Aec2 animals relative to the background strain and sham-treated animals.

RESULTS

The most notable proteomic signatures of IL-17 sequestration on SS-like disease-related proteins were Kallikrein-related peptidases, including the putative autoantigen Klk1b22. IL-17 sequestration also notably led to an isoelectric shift, but not a molecular weight shift, of Kallikrein-1, attributed to phosphorylation.

CONCLUSION

Non-viral IL-17 sequestration gene therapy in the salivary gland is feasible and downregulates expression of a putative SS autoantigen in the Aec1/Aec2 mouse.

The value of animal models to study immunopathology of primary human Sjögren's syndrome symptoms

Sjögren's syndrome (SjS) is a complex chronic autoimmune disease of multifactorial etiology that results in eventual loss of secretory function in the exocrine glands. The challenges towards finding a therapeutic prevention or treatment for SjS are due primarily to a lack of understanding in the pathophysiological and clinical progression of the disease. In order to circumnavigate this problem, there is a need for appropriate animal models that resemble the major phenotypes of human SjS and deliver a clear underlying biological or molecular mechanism capable of defining various aspects for the disease. Here, we present an overview of SjS mouse models that are providing insight into the autoimmune process of SjS and advance our focus on potential diagnostic and therapeutic targets.

Candidate chromosome 1 disease susceptibility genes for Sjogren's syndrome xerostomia are narrowed by novel NOD.B10 congenic mice

Sjogren's syndrome (SS) is characterized by salivary gland leukocytic infiltrates and impaired salivation (xerostomia). Cox-2 (Ptgs2) is located on chromosome 1 within the span of the Aec2 region. In an attempt to demonstrate that COX-2 drives antibody-dependent hyposalivation, NOD.B10 congenic mice bearing a Cox-2flox gene were generated. A congenic line with non-NOD alleles in Cox-2-flanking genes failed manifest xerostomia. Further backcrossing yielded disease-susceptible NOD.B10 Cox-2flox lines; fine genetic mapping determined that critical Aec2 genes lie within a 1.56 to 2.17Mb span of DNA downstream of Cox-2. Bioinformatics analysis revealed that susceptible and non-susceptible lines exhibit non-synonymous coding SNPs in 8 protein-encoding genes of this region, thereby better delineating candidate Aec2 alleles needed for SS xerostomia.

Type I interferon receptor deficiency prevents murine Sjogren's syndrome

In Sjögren's Syndrome (SS), inherent glandular defects, autoimmunity, and mononuclear cell infiltration within the salivary glands cause reduced salivation leading to xerostomia. Excessive production of type I interferons (IFN), triggered by environmental and genetic factors, is considered pathogenic in this disorder. However, whether type I IFN production is causative or an outcome of the disease process is not known. To address this question, we introduced a deficiency of interferon alpha receptor 1 (Ifnar1) into B6.Aec1Aec2 mice, which are known to have the genetic loci necessary for developing a SS-like disorder. This new mouse strain, B6.Aec1Aec2Ifnar1 (-/-), lacking type I IFN-mediated signaling, was characterized for pilocarpine-induced salivation, the presence of serum autoantibodies, sialoadenitis, and dacryoadenitis. Compared with the B6.Aec1Aec2Ifnar1 (+/+) (wild-type) mice, the B6.Aec1Aec2Ifnar1 (-/-) (knockout) mice had significantly lower mononuclear cell infiltration in the salivary and lacrimal glands. The knockout mice were completely protected from salivary gland dysfunction. Surprisingly, they had a robust autoantibody response comparable with that of the wild-type mice. These findings demonstrate that, in the absence of type I IFN-mediated signaling, systemic autoantibody responses can be dissociated from glandular pathology. Our study suggests that, in genetically susceptible individuals, the type I IFN pathway can instigate certain features of SS.

Current concepts: mouse models of Sjögren's syndrome

Sjögren's syndrome (SjS) is a complex chronic autoimmune disease of unknown etiology which primarily targets the exocrine glands, resulting in eventual loss of secretory function. The disease can present as either primary SjS or secondary SjS, the latter of which occurs concomitantly with another autoimmune disease such as rheumatoid arthritis, systemic lupus erythematosus, scleroderma, or primary biliary cirrhosis. Current advancements in therapeutic prevention and treatment for SjS are impeded by lack of understanding in the pathophysiological and clinical progression of the disease. Development of appropriate mouse models for both primary and secondary SjS is needed in order to advance knowledge of this disease. This paper details important features, advantages, and pitfalls of current animal models of SjS, including spontaneous, transgenic, knockout, immunization, and transplantation chimera mouse models, and emphasizes the need for a better model in representing the human SjS phenotype.

An autoimmune response to odorant binding protein 1a is associated with dry eye in the Aire-deficient mouse

Sjögren's Syndrome (SS) is a human autoimmune disease characterized by immune-mediated destruction of the lacrimal and salivary glands. In this study, we show that the Aire-deficient mouse represents a new tool to investigate autoimmune dacryoadenitis and keratoconjunctivitis sicca, features of SS. Previous work in the Aire-deficient mouse suggested a role for alpha-fodrin, a ubiquitous Ag, in the disease process. Using an unbiased biochemical approach, however, we have identified a novel lacrimal gland autoantigen, odorant binding protein 1a, targeted by the autoimmune response. This novel autoantigen is expressed in the thymus in an Aire-dependent manner. The results from our study suggest that defects in central tolerance may contribute to SS and provide a new and clinically relevant model to investigate the pathogenic mechanisms in lacrimal gland autoimmunity and associated ocular surface sequelae.

An NZW-derived interval on chromosome 7 moderates sialadenitis, but not insulitis in congenic nonobese diabetic mice

Autoimmune lymphocytic infiltration of the salivary glands, termed sialadenitis, is a pathologic feature of Sjögren's syndrome (SjS) that is also prominent in nonobese diabetic (NOD) mice. Genetic factors regulate sialadenitis, and a previous (NOD x NZW)F2 study detected linkage to murine chromosome (Chr) 7. The locus, subsequently annotated as Ssial3, maps to the distal end of Chr7 and overlaps a region associated with type 1 diabetes susceptibility in NOD mice. To examine whether Ssial3 could contribute to both diseases, or was specific for SjS, we generated a congenic mouse strain that harbored an NZW-derived Chr7 interval on the NOD genetic background. This congenic strain exhibited reduced sialadenitis compared with NOD mice and confirmed Ssial3. This reduction, however, did not ameliorate saliva abnormalities associated with SjS-like disease in NOD mice, nor were congenic mice protected against insulitis (lymphocytic infiltration of the pancreatic islets) or diabetes onset. Thus, the Ssial3 locus appears to have a tissue-specific effect for which the NZW allele is unable to prevent other autoimmune traits in the NOD mouse. Anomalous increases for antinuclear Ab production and frequency of marginal-zone B cells were also identified in congenic mice, indicating that the NZW-derived Chr7 interval has a complex effect on the NOD immune system.

Sjögren syndrome: advances in the pathogenesis from animal models

Sjögren syndrome is an autoimmune disease characterized by hyposecretion of the lacrimal and salivary glands, resulting in dryness of the eyes and mouth. Individuals may experience primary Sjögren syndrome or a secondary form accompanying another rheumatic autoimmune disease, such as rheumatoid arthritis or systemic lupus erythematosus. The pathogenic mechanisms of Sjögren syndrome remain largely unknown, in part a consequence of the heterogeneity of the disease. Animal models have shed light on the connections between specific pathways and symptoms, but an ideal system is wanting. Improved disease models will enable a better understanding of Sjögren syndrome, including how immune tolerance is lost and potential therapeutic interventions. Most importantly, an optimal model will enable detection of disease biomarkers, since injury to the salivary glands may precede lymphocytic infiltration. This review aims to characterize available mice models of Sjögren syndrome, including advantages and disadvantages, from the researcher's perspective.

Differential gene expression in the salivary gland during development and onset of xerostomia in Sjögren's syndrome-like disease of the C57BL/6.NOD-Aec1Aec2 mouse

INTRODUCTION

Recently, we reported the development of the C57BL/6.NOD-Aec1Aec2 mouse that carries two genetic intervals derived from the non-obese diabetic (NOD) mouse capable of conferring Sjögren's syndrome (SjS)-like disease in SjS-non-susceptible C57BL/6 mice. In an attempt to define the molecular bases underlying the onset of stomatitis sicca (xerostomia) in this C57BL/6.NOD-Aec1Aec2 mouse model, we have carried out a study using genomic microarray technology.

METHODS

By means of oligonucleotide microarrays, gene expression profiles of salivary glands at 4, 8, 12, 16, and 20 weeks of age were generated for C57BL/6.NOD-Aec1Aec2 male mice. Using Linear Models for Microarray Analysis and B-statistics software, 480 genes were identified as being differentially expressed (P < 0.01 and Q < 0.0001) during the development of SjS-like disease in the salivary glands.

RESULTS

The 480 genes could be arranged into four clusters, with each cluster defining a unique pattern of temporal expression, while the individual genes within each cluster could be grouped according to related biological functions. By means of pair-wise analysis, temporal changes in transcript expressions provided profiles indicating that many additional genes are differentially expressed at specific time points during the development of disease. Multiple genes reportedly showing an association with autoimmunity and/or SjS, in either humans or mouse models, were found to exhibit differential expressions, both quantitatively and temporally. Selecting various families of genes associated with specific functions (for example, antibody production, complement, and chemokines), we noted that only a limited number of family members showed differential expressions and these correlated with specific phases of disease.

CONCLUSIONS

Taking advantage of known functions of these genes, investigators can construct interactive gene pathways, leading to modeling of possible underlying events inducing salivary gland dysfunction. Thus, these different approaches to analyzing microarray data permit the identification of multiple sets of genes of interest whose expressions and expression profiles may correlate with molecular mechanisms, signaling pathways, and/or immunological processes involved in the development and onset of SjS.

Altered expression of genes functioning in lipid homeostasis is associated with lipid deposition in NOD mouse lacrimal gland

Functional atrophy and accompanying lymphocytic infiltration and destruction of the lacrimal gland (LG) are characteristics of Sjögren's Syndrome (SjS). The male NOD mouse is an experimental model for the autoimmune exocrinopathy that develops in the LG of SjS patients. Acinar cells in LG of male NOD mice aged 3-4 months were previously shown to accumulate lipid droplets. In the current study, analysis of lipid components revealed that the accumulated lipids were mostly cholesteryl esters (CE). Gene expression microarray analysis followed by real-time RT-PCR revealed alterations in the expression of several genes involved in lipid homeostasis in LG of 12-week-old male NOD mice relative to matched BALB/c controls. A series of upregulated genes including apolipoprotein E, apolipoprotein F, hepatic lipase, phosphomevalonate kinase, ATP-binding cassette D1 and ATP-binding cassette G1 were identified. Comparison of liver mRNAs to LG mRNAs in BALB/c and NOD mice revealed that the differential expressions were LG-specific. Gene expression profiles were also characterized in LGs of female mice, younger mice and immune-incompetent NOD SCID mice. Investigation of the cellular distribution of Apo-E and Apo-F proteins suggested that these proteins normally coordinate to mediate lipid efflux from the acinar cells but that dysfunction of these processes due to missorting of Apo-F may contribute to CE deposition. Finally, the initiation and extent of lipid deposition were correlated with lymphocytic infiltration in the LG of male NOD mice. We propose that impaired lipid efflux contributes to lipid deposition, an event that may contribute to the development and/or progression of dacryoadenitis in the male NOD mouse.

Sjögren's syndrome: an old tale with a new twist

Sjögren's syndrome (SjS) is chronic autoimmune disease manifested by the loss of saliva and/or tear secretion by salivary and/or lacrimal glands, respectively. The pathogenesis of the disease remains elusive, perhaps due to the multiple triggers of the disease. However, substantial advances have been made in attempting to resolve the complexity of SjS using both animal models and human subjects. The primary objectives of this review are to provide a better understanding of the disease processes with major emphasis on the use of mouse models, how genetic predisposition plays a role in the natural history of the disease, as well as a presentation of new findings pertaining to the role of T(H)1, T(H)2, and T(H)17 cells in the pathogenesis of SjS.

Identification of possible candidate genes regulating Sjögren's syndrome-associated autoimmunity: a potential role for TNFSF4 in autoimmune exocrinopathy

Introduction

Sjögren syndrome (SjS) is a systemic autoimmune disease in which an immunological attack primarily against the salivary and lacrimal glands results in the loss of acinar cell tissue and function, leading to stomatitis sicca and keratoconjunctivitis sicca. In recent years, two genetic regions, one on chromosome 1 (designated autoimmune exocrinopathy 2 or Aec2) and the second on chromosome 3 (designated autoimmune exocrinopathy 1 or Aec1) derived from nonobese diabetic (NOD) mice, have been shown to be necessary and sufficient to replicate SjS-like disease in nonsusceptible C57BL/6 mice.

Methods

Starting with the SjS-susceptible C57BL/6-derived mouse, referred to as C57BL/6.NOD-Aec1Aec2, we generated a large set of recombinant inbred (RI) lines containing portions of Aec2 as a means of identifying more precisely the genetic elements of chromosome 1 responsible for disease development.

Results

Disease profiling of these RI lines has revealed that the SjS susceptibility genes of Aec2 lie within a region located at approximately 79 ± 5 cM distal to the centromere, as defined by microsatellite markers. This chromosomal region contains several sets of genes known to correlate with various immunopathological features of SjS as well as disease susceptibility genes for both type 1 diabetes and systemic lupus erythematosus in mice. One gene in particular, tumor necrosis factor (ligand) superfamily member 4 (or Ox40 ligand), encoding a product whose biological functions correlate with both physiological homeostasis and immune regulations, could be a potential candidate SjS susceptibility gene.

Conclusions

These new RI lines represent the first step not only in fine mapping SjS susceptibility loci but also in identifying potential candidate SjS susceptibility genes. Identification of possible candidate genes permits construction of models describing underlying molecular pathogenic mechanisms in this model of SjS and establishes a basis for construction of specific gene knockout mice.

Differential gene expressions in the lacrimal gland during development and onset of keratoconjunctivitis sicca in Sjögren's syndrome (SJS)-like disease of the C57BL/6.NOD-Aec1Aec2 mouse

Recently, we reported development of the C57BL/6.NOD-Aec1Aec2 mouse carrying two genetic intervals derived from the NOD mouse. These two genetic regions confer Sjögren's syndrome (SjS)-like disease in SjS-non-susceptible C57BL/6 mice. In an attempt to define the molecular bases underlying onset of dacryoadenitis and subsequently keratoconjunctivitis sicca (or xerophthalmia) in the C57BL/6.NOD-Aec1Aec2 mouse model, we have carried out a study utilizing microarray technology. Using oligonucleotide microarrays, gene expression profiles of lacrimal glands at 4, 8, 12, 16 and 20weeks of age were generated for C57BL/6.NOD-Aec1Aec2 male mice. Analyses using Linear Models for Microarray Analysis package and B-statistics, 552 genes were identified as being differentially expressed (adjusted p-value <0.01 and B <1.5) during the development of SjS-like disease. These 552 genes could be arranged into four clusters, with each cluster defining a unique pattern of temporal expression, while the individual genes within each cluster could be grouped according to related function. Using a pair-wise analysis, temporal changes in gene expressions provided profiles indicating that individual genes were differentially expressed at specific time points during development of SjS. In addition, multiple genes that have been reported to show, either in humans or mouse models, an association with autoimmunity and/or SjS, e.g., ApoE, Baff, Clu, Ctla4, Fas/Fasl, Irf5, Lyzs, Nfkb, Socs3, Stat4, Tap2, Tgfbeta1, Tnfa, and Vcam1 were also found to exhibit differential expressions, both quantitatively and temporally. Selecting a few families of genes, e.g., cystatins, cathepsins, metalloproteinases, lipocalins, complement, kallikreins, carbonic anhydrases and tumor necrosis factors, it was noted that only a limited number of family members showed differential expressions, suggesting a restricted glandular expression. Utilizing these genes, pathways of inter-reactive genes have been constructed for apoptosis and fatty acid homeostasis, leading to modeling of possible underlying events inducing disease. Thus, these different approaches to analyze microarray data permit identification of multiple sets of genes of interest whose expressions and expression profiles may correlate with molecular mechanisms, signaling pathways and/or immunological processes involved in the development and onset of SjS in this mouse model, thereby providing new insight into the underlying cause or regulation of this disease.

Gender and autoimmunity

The enhanced immunoreactivity in females is a double-edged sword that provides better protection against infections, but may lead to enhanced autoreactivity and thereby contribute to the induction of autoimmunity. Autoimmune diseases demonstrate a gender bias and represent the fifth leading cause of death by disease among females of reproductive age. Clinical and murine experimental studies indicate that the gender bias in autoimmunity may be influenced by sex hormones, predominantly displayed in the development and exacerbations of the prototypical autoimmune disease lupus. The associations between sex hormones and other autoimmune diseases are less clear. Our review on the impact of gender via sex hormones and sex related genes in the pathogenesis of several autoimmune diseases suggests that a better understanding of the underlying mechanisms behind the sexual dimorphism of the immune system may lead to the development of novel therapeutic approaches to autoimmunity.