Progress in understanding autoimmune exocrinopathy using the non-obese diabetic mouse: an update

Rodent models for dry eye syndrome (DES)

Dry eye syndrome (DES) is a range of ophthalmic conditions characterized by compromised tear film homeostasis, resulting from various pathological factors and primarily manifesting as ocular discomfort and impaired ocular surface integrity. With the rise in screen time due to modern lifestyles, the prevalence of DES is increasing annually, posing a significant global public health challenge. Pathophysiologically, DES involves damage to the lacrimal functional unit (LFU), including the lacrimal glands, meibomian glands, and corneoconjunctival epithelium, highlighting its multifactorial etiology. Current treatments mainly focus on artificial tears for moisture replacement and anti-inflammatory therapies, but both are limited. Consequently, animal models are crucial for understanding the complex pathological mechanisms of DES and identifying potential therapeutic agents. Rodent eyes, with their structural and physiological similarities to human eyes and cost-effectiveness, have become widely used in DES research. This manuscript reviews the current understanding of DES pathogenesis and rodent models, discussing their strengths, weaknesses, and relevant genetic models. The aim is to furnish critical insights and provide a scholarly resource to propel future investigative endeavors into the pathogenesis of and therapy for DES.

A comprehensive review of Sjögren's syndrome: Classification criteria, risk factors, and signaling pathways

Sjögren's syndrome (SS) is a chronic autoimmune disease that affects the exocrine glands and may lead to a range of systemic symptoms that impact various organs. Both innate and adaptive immune pathways might trigger the disease. Studying the signaling pathways underlying SS is crucial for enhancing diagnostic and therapeutic effectiveness. SS poses an ongoing challenge for medical professionals owing to the limited therapeutic options available. This review offers a comprehensive understanding of the intricate nature of SS, encompassing disease classification criteria, risk factors, and signaling pathways in immunity and inflammation. The advancements summarized herein have the potential to spark new avenues of research into SS.

Marginal Zone B (MZB) Cells: Comparison of the Initial Identification of Immune Activity Leading to Dacryoadenitis and Sialadenitis in Experimental Sjögren's Syndrome

Although multiple mouse strains have been advanced as models for Sjögren's syndrome (SS), which is a human systemic autoimmune disease characterized primarily as the loss of lacrimal and salivary gland functions, the C57BL/6.NOD-Aec1Aec2 recombinant inbred (RI) mouse derived from the NOD/ShiLtJ line is considered one of the more appropriate models exhibiting virtually all the characteristics of the human disease. This mouse model, as well as other mouse models of SS, have shown that B lymphocytes are essential for the onset and development of observed clinical manifestations. Recently, studies carried out in the C57BL/6.IL14α transgenic mouse have provided clear evidence that the marginal zone B (MZB) cell population is directly involved in the early pathological events initiating the development of the clinical SS disease, as well as late-stage lymphomagenesis resulting in B-cell lymphomas. Since MZB cells are difficult to study in vivo and in vitro, we carried out a series of ex vivo investigations that utilize temporal global RNA transcriptomic analyses to profile differentially expressed genes exhibiting temporal upregulation during the initial onset and subsequent development of pathophysiological events within the lacrimal and salivary gland tissues per se or associated with the leukocyte cell migrations into these glands. The initial transcriptomic analyses revealed that while the upregulated gene expression profiles obtained from lacrimal and salivary glands overlap, multiple genetic differences exist between the defined activated pathways. In the current study, we present a concept suggesting that the initial pathological events differ between the two glands, yet the subsequent upregulated TLR4/TLR3 signal transduction pathway that activates the type-1 interferon signature appears to be identical in the two glands and indicates an autoimmune response against dsRNA, possibly a virus. Here, we attempt to put these findings into perspective and determine how they can impact the design of future therapeutic protocols.

Neurosensory abnormalities and stability of a mouse model of dry eye disease

This study aimed to use a mouse model of dry eye disease (DED) induced by topical administration of benzalkonium chloride (BAK) and assess its stability and the presence of neurosensory abnormalities, including ocular pain. Eight-week-old C57BL6/6 N male mice were used in this study. Mice were treated with 10 μL of 0.2% BAK dissolved in artificial tears (AT), administered twice daily for 7 days. After one week, animals were randomized into two groups: one was administered with 0.2% BAK in AT once per day for 7 days, while the other was not further treated. Corneal epitheliopathy was quantified at days 0, 3, 7, 12, and 14. Moreover, tear secretions, corneal nociception, and corneal nerve integrity were measured after BAK treatment. After sacrifice, corneas were dissected to assess nerve density and leukocyte infiltration by immunofluorescence. Topical BAK instillation for 14 days significantly increased corneal fluorescein staining (p < 0.0001) compared to day 0. On the other hand, interruption of BAK instillation was associated with improvement of corneal epitheliopathy (day 12, p < 0.0001; day 14, p < 0.001). BAK treatment increased ocular pain (p < 0.0001) and resulted in a significant increase in leukocyte infiltration in the cornea (p < 0.01). Moreover, corneal sensitivity was reduced (p < 0.0001), together with corneal nerve density (p < 0.0001) and tear secretion (p < 0.0001). One week twice a day, followed by one additional week once a day, of 0.2% BAK topical administration induces stable clinical and histological signs of DED, which is associated with neurosensory abnormalities, including pain.

A MZB Cell Activation Profile Present in the Lacrimal Glands of Sjögren's Syndrome-Susceptible C57BL/6.NOD-Aec1Aec2 Mice Defined by Global RNA Transcriptomic Analyses

The C57BL/6.NOD-Aec1Aec2 mouse has been extensively studied to define the underlying cellular and molecular basis for the onset and development of Sjögren's syndrome (SS), a human systemic autoimmune disease characterized clinically as the loss of normal lacrimal and salivary gland functions leading respectively to dry eye and dry mouth pathologies. While an overwhelming majority of SS studies in both humans and rodent models have long focused primarily on pathophysiological events and the potential role of T lymphocytes in these events, recent studies in our murine models have indicated that marginal zone B (MZB) lymphocytes are critical for both development and onset of SS disease. Although migration and function of MZB cells are difficult to study in vivo and in vitro, we have carried out ex vivo investigations that use temporal global RNA transcriptomic analyses to track early cellular and molecular events in these exocrine glands of C57BL/6.NOD-Aec1Aec2 mice. In the present report, genome-wide transcriptome analyses of lacrimal glands indicate that genes and gene-sets temporally upregulated during early onset of disease define the Notch2/NF-kβ14 and Type1 interferon signal transduction pathways, as well as identify chemokines, especially Cxcl13, and Rho-GTPases, including DOCK molecules, in the cellular migration of immune cells to the lacrimal glands. We discuss how the current results compare with our recently published salivary gland data obtained from similar studies carried out in our C57BL/6.NOD-Aec1Aec2 mice, pointing out both similarities and differences in the etiopathogeneses underlying the autoimmune response within the two glands. Overall, this study uses the power of transcriptomic analyses to identify temporal molecular bioprocesses activated during the preclinical covert pathogenic stage(s) of SS disease and how these findings may impact future intervention therapies as the disease within the two exocrine glands may not be identical.

The NOD Mouse Beyond Autoimmune Diabetes

Autoimmune diabetes arises spontaneously in Non-Obese Diabetic (NOD) mice, and the pathophysiology of this disease shares many similarities with human type 1 diabetes. Since its generation in 1980, the NOD mouse, derived from the Cataract Shinogi strain, has represented the gold standard of spontaneous disease models, allowing to investigate autoimmune diabetes disease progression and susceptibility traits, as well as to test a wide array of potential treatments and therapies. Beyond autoimmune diabetes, NOD mice also exhibit polyautoimmunity, presenting with a low incidence of autoimmune thyroiditis and Sjögren's syndrome. Genetic manipulation of the NOD strain has led to the generation of new mouse models facilitating the study of these and other autoimmune pathologies. For instance, following deletion of specific genes or via insertion of resistance alleles at genetic loci, NOD mice can become fully resistant to autoimmune diabetes; yet the newly generated diabetes-resistant NOD strains often show a high incidence of other autoimmune diseases. This suggests that the NOD genetic background is highly autoimmune-prone and that genetic manipulations can shift the autoimmune response from the pancreas to other organs. Overall, multiple NOD variant strains have become invaluable tools for understanding the pathophysiology of and for dissecting the genetic susceptibility of organ-specific autoimmune diseases. An interesting commonality to all autoimmune diseases developing in variant strains of the NOD mice is the presence of autoantibodies. This review will present the NOD mouse as a model for studying autoimmune diseases beyond autoimmune diabetes.

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.

Advances in Pathogenesis of Sjögren's Syndrome

Sjögren's syndrome (SS) is a chronic autoimmune disease of unknown etiology that mainly involves exocrine glands. Patients present with dry mouth and eyes, fever, arthralgia, and other systemic symptoms. In severe cases, the quality of life of patients is affected. At present, there is no cure for SS, and the treatment options are extremely limited. In recent years, studies of patients and animal models have identified abnormalities of immune cell function and cytokines to be involved in SS. A systematic review of the literature may clarify the etiology and pathogenesis of SS, as well as provide a theoretical basis for the development of new drugs for the treatment of SS.

Animal models of dry eye: Their strengths and limitations for studying human dry eye disease

Dry eye disease (DED), also called the keratoconjunctivitis sicca, is one of the most common diseases in the ophthalmology clinics. While DED is not a life-threatening disease, life quality may be substantially affected by the discomfort and the complications of poor vision. As such, a large number of studies have made contributions to the investigation of the DED pathogenesis and novel treatments. DED is a multifactorial disease featured with various phenotypic consequences; therefore, animal models are valuable tools suitable for the related studies. Accordingly, selection of the animal model to recapitulate the clinical presentation of interest is important for appropriately addressing the research objective. To this end, we systemically reviewed different murine and rabbit models of DED, which are categorized into the quantitative (aqueous-deficient) type and the qualitative (evaporative) type, based on the schemes to establish. The clinical manifestations of dry eye on animal models can be induced by mechanical or surgical approaches, iatrogenic immune response, topical eye drops, blockage of neural pathway, or others. Although these models have shown promising results, each has its own limitation and cannot fully reproduce the pathophysiological mechanisms that occur in patients. Nonetheless, the animal models remain the best approximation of human DED and represent the valuable tool for the DED studies.

Effect of Myd88 deficiency on gene expression profiling in salivary glands of female non-obese diabetic (NOD) mice

OBJECTIVES

Sjögren's syndrome (SS) is a chronic autoimmune disease characterized by inflammatory lesions in the salivary and lacrimal glands, which are caused by distinct lymphocytic infiltrates. Female non-obese diabetic (NOD) mice spontaneously develop inflammatory lesions of the salivary glands with SS-like pathological features. Previous studies have shown that MyD88, a crucial adaptor protein that activates innate immune signaling, affects lymphocytic infiltration, but its detailed role remains unclear. In this study, we investigated the role of MyD88 through gene expression profiling in the early phase of pathogenesis in the salivary glands of female NOD mice.

METHODS

Submandibular glands collected from 10-week-old female wild-type and Myd88-deficient NOD mice were used for RNA preparation, followed by microarray analysis. The microarray dataset was analyzed to identify Myd88-dependent differentially expressed genes (DEGs). Data generated were used for GO enrichment, KEGG pathway, STRING database, and INTERFEROME database analyses.

RESULTS

Myd88 deficiency was found to affect 230 DEGs, including SS-associated genes, such as Cxcl9 and Bpifa2. Most of the DEGs were identified as being involved in immunological processes. KEGG pathway analysis indicated that the DEGs were putatively involved in autoimmune diseases, such as systemic lupus erythematosus and rheumatoid arthritis. Furthermore, the DEGs included 149 interferon (IFN)-regulated genes.

CONCLUSIONS

MyD88 is involved in the expression of specific genes associated with IFN-associated immunopathological processes in the salivary glands of NOD mice. Our findings are important for understanding the role of MyD88-dependent innate immune signaling in SS manifestation.

Secreted factors from dental pulp stem cells improve Sjögren's syndrome via regulatory T cell-mediated immunosuppression

Background

Sjögren’s syndrome (SS) is a chronic autoimmune disease primarily characterized by inflammation in the salivary and lacrimal glands. Activated T cells contribute to disease pathogenesis by producing proinflammatory cytokines, which leads to a positive feedback loop establishment. The study aimed to evaluate the effects of secreted factors derived from dental pulp stem cells (DPSCs) or bone marrow mesenchymal stem cells (BMMSCs) on hyposalivation in SS and to investigate the mechanism involved.

Methods

Eighty percent confluent stem cells were replenished with serum-free Dulbecco’s modified Eagle’s medium and incubated for 48 h; following which, conditioned media from DPSCs (DPSC-CM) and BMMSCs (BMMSC-CM) were collected. Cytokine array analysis was performed to assess the types of cytokines present in the media. Flow cytometric analysis was performed to evaluate the number of activated T cells cultured in DPSC-CM or BMMSC-CM. Subsequently, DPSC-CM or BMMSC-CM was administered to an SS mouse model. The mice were categorized into the following groups (n = 6 each): non-treatment, Dulbecco’s modified Eagle’s medium (−), BMMSC-CM, and DPSC-CM. Histological analysis of the salivary glands was performed. The gene and protein expression levels of cytokines associated with T helper subsets in the submandibular glands (SMGs) were evaluated.

Results

DPSC-CM contained more secreted factors with tissue-regenerating mechanisms, such as cell proliferation, anti-inflammatory effects, and immunomodulatory effects. DPSC-CM was more effective in suppressing the activated T cells than other groups in the flow cytometric analysis. The stimulated salivary flow rate increased in SS mice with DPSC-CM compared with that in the other groups. In addition, the number of inflammation sites in SMGs of the mice administered with DPSC-CM was lower than that in the other groups. The expression levels of interleukin (Il)-10 and transforming growth factor-β1 were upregulated in the DPSC-CM group, whereas those of Il-4 and Il-17a were downregulated. The DPSC-CM-administered group presented with a significantly increased percentage of regulatory T (Treg) cells and a significantly decreased percentage of type 17 Th (Th17) cells compared with the other groups.

Conclusions

These results indicated that DPSC-CM ameliorated SS by promoting Treg cell differentiation and inhibiting Th17 cell differentiation in the mouse spleen.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02236-6.

Early diagnosis and treatment for Sjögren's syndrome: current challenges, redefined disease stages and future prospects

There are some challenges and unmet needs in the early diagnosis and management of Sjögren's syndrome (SjS) such as prominent glandular dysfunction at diagnosis and long diagnostic delay. Those challenges are partly attributed to the lack of a good knowledge of the early stages of SjS, which is a major obstacle to delivering appropriate care to SjS patients. Findings from both clinical and experimental studies suggest the plausibility of a redefined SjS course consisting of 4 stages, which includes initiation stage, preclinical stage, asymptomatic SjS stage and overt SjS stage. More studies focusing on the pathological processes and changes during the early stages of SjS are needed. To enable early diagnosis and treatment for SjS, more useful biomarkers of the early stages of SjS need to be identified, and individuals at high risk of SjS development need to be identified. Appropriate screening can be performed to facilitate the early diagnosis of SjS among those high-risk individuals.

Innate Immunity and Biological Therapies for the Treatment of Sjögren's Syndrome

Sjögren's syndrome (SS) is a systemic autoimmune disorder affecting approximately 3% of the population in the United States. This disease has a female predilection and affects exocrine glands, including lacrimal and salivary glands. Dry eyes and dry mouths are the most common symptoms due to the loss of salivary and lacrimal gland function. Symptoms become more severe in secondary SS, where SS is present along with other autoimmune diseases like systemic lupus erythematosus, systemic sclerosis, or rheumatoid arthritis. It is known that aberrant activation of immune cells plays an important role in disease progression, however, the mechanism for these pathological changes in the immune system remains largely unknown. This review highlights the role of different immune cells in disease development, therapeutic treatments, and future strategies that are available to target various immune cells to cure the disease.

Injection of CD40 DNA vaccine ameliorates the autoimmune pathology of non-obese diabetic mice with Sjögren's syndrome

BACKGROUND

Overexpression of CD40 has been reported in patients with primary Sjögren's syndrome (pSS). The increased CD40 expression promote autoimmune response and enhance inflammation in pSS. The aim of this study is to block CD40-CD154 interaction with CD40 DNA vaccine to slow the disease progression of SS in non-obese diabetic (NOD) mice.

METHODS

Female NOD mice were treated with CD40 DNA vaccine, empty vector and normal saline. The salivary flow rate was measured, whereas lymphocytes infiltration in the salivary glands was assessed by histopathology. Expression of CD40 and B220 in salivary were examined by immunohistochemistry. Splenic lymphocyte phenotypes were analyzed by flow cytometry. CD40, IL-1β, TNF-α and IL-6 levels in the salivary glands were detected by PCR. Serum anti-CD40 antibody was measured by ELISA. Serum anti-nuclear antibody (ANA) was monitored by immunofluorescence.

RESULTS

NOD mice treated with CD40 DNA vaccine showed higher levels of anti-CD40 antibody compared with the controls. The expression of CD40 in the salivary glands of NOD mice in CD40 DNA vaccine group was decreased. The infiltration of lymphocytes was reduced in the salivary glands and saliva secretion was increased in the treatment group. The expression level of TNF-α and IL-6 in salivary glands were declined. The splenic dendritic cell and plasma cell populations were reduced and the level of ANA was decreased in NOD mice with CD40 DNA vaccine treatment.

CONCLUSIONS

CD40 DNA vaccine inhibits the immune response and reduce inflammation in epithelial tissues SS in non-obese diabetic (NOD) mice, suggesting that CD40 DNA vaccine could be a new therapeutic approach in treatment of pSS.

Dental erosion in mice with impaired salivary gland function

Objective: Salivary flow rate exerts an essential impact on the development and progression of dental erosion. In this work, the experimental dental erosion in non-obese diabetic (NOD) mice with reduced salivary flow rate was induced, and the erosive effect of acidic drinks on their dentition was studied.Material and methods: Three acidic drinks (sports drink, cola light drink and sugar containing cola drink) were given to adult NOD mice (groups: N = 11) as the only drink for 6 weeks. Two control groups were included; wild type and NOD control (groups: N = 9). Experimental and control (water) teeth were dissected out and observed by scanning electron microscopy (SEM). Mandibular first molars were subsequently embedded in Epon, ground transversely, observed again by SEM, and the enamel thickness and tooth height were measured.Results: Mandibular molars were considerably more eroded than maxillary molars. The erosive process started at the top of the cusps and subsequently extended in the cervical, mesio-distal, and pulpal direction. Erosive lesions were evident in increased succession from sports drink, cola light to cola drink exposed mandibular molars, with the lingual tooth height being approximately 23%, 26%, and 37% lower, respectively, compared to the control. The lingual enamel was approximately 48% thinner in sports drink molars and 62% thinner in cola light molars. In cola drink molars, the lingual enamel was totally eroded, and significant erosion of dentine was evident.Conclusion: Reduced salivary flow, together with a high consumption of acidic drinks, results in severe erosion of NOD mice molars.

Metabolic abnormalities exacerbate Sjögren's syndrome by and is associated with increased the population of interleukin-17-producing cells in NOD/ShiLtJ mice

Background

Sjögren’s syndrome (SS) is an autoimmune disease mediated by lymphocytic infiltration into exocrine glands, resulting in progressive lacrimal and salivary destruction and dysfunctional glandular secretion. Metabolic syndrome influences the immune system. To investigate its relationship with metabolic abnormalities, we evaluated the pathogenesis of SS and the immune cell populations in non-obese diabetic NOD/ShiLtJ mice with type 1 diabetes (T1D).

Methods

To induce metabolic abnormalities, streptozotocin (STZ)—a glucosamine–nitrosourea compound that destroys pancreatic β cells, resulting in T1D—was injected into NOD/ShiLtJ mice. The blood glucose level was measured to evaluate induction of T1D. The severity of SS was assessed by determining the body weight, salivary flow rate, and histologic parameters. The expression levels of proinflammatory factors in the salivary glands, lacrimal gland, and spleen were quantified by real–time PCR. The populations of various T– and B–cell subtypes in the peripheral blood, spleen, and salivary glands were assessed by flow cytometry.

Results

Induction of T1D in NOD/ShiLtJ mice increased both the severity of SS and the levels of proinflammatory cytokines in the salivary glands compared to the controls. Furthermore, the number of interleukin-17–producing immune cells in the peripheral blood, spleen, and salivary glands was increased in STZ- compared to vehicle-treated NOD/ShiLtJ mice.

Conclusions

Metabolic abnormalities play an important role in the development of SS.

The Effect of Chloroquine on the Development of Dry Eye in Sjögren Syndrome Animal Model

Purpose

Sjögren syndrome (SS) is an autoimmune disease characterized by the inflammatory destruction of salivary and lacrimal glands (LG). Chloroquine (CQ) was known as an immunomodulatory drug and in the inhibition of autophagy. The purpose of the study is to investigate the effect of CQ on the development of dry eye in NOD-LtJ mice.

Methods

NOD-LtJ mice were observed, during which the occurrence of dry eye was confirmed by tear secretion, corneal staining, and the infiltration of foci into the LG from 13-week-old mice. Intraperitoneal (IP) administration of CQ was performed in 13-week-old mice for 4 weeks and maintained untreated for another 4 weeks. Additionally, CQ was injected IP in 19-week-old mice for 2 weeks from when the disease was fully developed.

Results

Interestingly, the expression of autophagy marker ATG5 and LC3B-II was observed in the LG from week 5. When CQ had been administered for 4 weeks from week 13 and then maintained untreated for 4 weeks, tear secretion, corneal staining score, foci formation in the LG, conjunctival goblet cells and proinflammatory cytokine expressions were significantly better than untreated mice. The infiltration of immune cells and the expression of autophagy markers in LG were decreased in the CQ group. These indices improved significantly as well when the 19-week-old mice with severe clinical phenotypes had been treated with CQ for 2 weeks.

Conclusions

This study demonstrated that autophagy was induced in the early stages of the SS model and that CQ treatment in the early stages could inhibit disease progression.

Interleukin‑12 exacerbates Sjögren's syndrome through induction of myeloid‑derived suppressor cells

Interleukin (IL)-12 modulates the generation and function of various immune cells and plays a vital role in the pathogenesis of Sjögren's syndrome (SS). Myeloid-derived suppressor cells (MDSCs) are involved in autoimmune diseases by regulating various immune responses. However, it has not been confirmed whether inflammatory IL-12 participates in the progression of SS via regulating MSDCs. In the present study, the plasma levels of IL-12 were detected by ELISA in SS-like non-obese diabetic (NOD) mice. The mice were treated by intraperitoneal injection of IL-12 and anti-IL-12 antibody, respectively, and then the salivary flow rate was detected. The pathology of submandibular glands was evaluated in tissue sections stained with hematoxylin and eosin. The proportion of MDSCs was assessed by flow cytometry. The results showed that plasma IL-12 was significantly increased in the SS-like NOD mice comparing with that noted in the control mice. The exogenous IL-12 exacerbated SS-like symptoms of NOD mice and promoted the generation of both bone marrow (BM) and splenic MDSCs in the SS-like NOD mice. Of note, anti-IL-12 alleviated SS-like symptoms of NOD mice and inhibited the generation of BM and splenic MDSCs. Moreover, the generation of MDSCs was crippled in the IL-12-deficient C57BL/6 (Il-12^−/− B6) mice. Our findings suggest that aggravation of SS-like symptoms by IL-12 in NOD mice may be attributed to its promotion of MDSC development.

Current and Emerging Evidence for Toll-Like Receptor Activation in Sjögren's Syndrome

While the importance of Toll-like receptor (TLR) signaling is well established in many autoimmune diseases, the role of TLR activation in Sjögren's syndrome (SS) is poorly understood. Studies in mice and humans reveal that TLRs are potent mediators of inflammation in SS. TLRs are expressed and functional in salivary tissue, and TLRs in peripheral blood cells of SS patients are also upregulated and hyperresponsive to ligation. In this review, we will detail observations in mouse models regarding the importance of TLR activation in both local and systemic disease. We will then discuss studies in SS patients that provide evidence of the importance of TLR-mediated signaling in disease. While the ligands that activate TLRs in the context of SS are unknown, emerging data suggest that damage-associated molecular patterns (DAMPs) may be significant drivers of the chronic and unremitting inflammation that is characteristic of SS. We will discuss putative DAMPs that may be of clinical significance in disease. Therapies that target TLR signaling cascades will likely reduce both exocrine-specific and systemic manifestations of SS.

Update on Pathogenesis of Sjogren's Syndrome

Sjogren's syndrome is a common autoimmune disease that presents with sicca symptoms and extraglandular features. Sjogren's syndrome is presumably as common as RA; yet it is poorly understood, underdiagnosed and undertreated. From the usual identity as an autoimmune exocrinopathy to its most recent designate as an autoimmune epithelitis - the journey of SS is complex. We herein review some of the most important milestones that have shed light on different aspects of pathogenesis of this enigmatic disease. This includes role of salivary gland epithelial cells, and their interaction with cells of the innate and adaptive immune system. Non-immune factors acting in concert or in parallel with immune factors may also be important. The risk genes identified so far have only weak association, nevertheless advances in genetics have enhanced understanding of disease mechanisms. Role of epigenetic and environmental role factors is also being explored. SS has also some unique features such as congenital heart block and high incidence of lymphoma; disease mechanisms accounting for these manifestations are also reviewed.

Sjögren-Like Lacrimal Keratoconjunctivitis in Germ-Free Mice

Commensal bacteria play an important role in the formation of the immune system but their role in the maintenance of immune homeostasis at the ocular surface and lacrimal gland remains poorly understood. This study investigated the eye and lacrimal gland phenotype in germ-free and conventional C57BL/6J mice. Our results showed that germ-free mice had significantly greater corneal barrier disruption, greater goblet cell loss, and greater total inflammatory cell and CD4⁺ T cell infiltration within the lacrimal gland compared to the conventionally housed group. A greater frequency of CD4⁺IFN-γ⁺ cells was observed in germ-free lacrimal glands. Females exhibited a more severe phenotype compared to males. Adoptive transfer of CD4⁺ T cells isolated from female germ-free mice into RAG1KO mice transferred Sjögren-like lacrimal keratoconjunctivitis. Fecal microbiota transplant from conventional mice reverted dry eye phenotype in germ-free mice and decreased CD4⁺IFN-γ⁺ cells to levels similar to conventional C57BL/6J mice. These findings indicate that germ-free mice have a spontaneous lacrimal keratoconjunctivitis similar to that observed in Sjögren syndrome patients and demonstrate that commensal bacteria function in maintaining immune homeostasis on the ocular surface. Thus, manipulation of intestinal commensal bacteria has the potential to become a novel therapeutic approach to treat Sjögren Syndrome.

AT-RvD1 combined with DEX is highly effective in treating TNF-α-mediated disruption of the salivary gland epithelium

Sjögren's syndrome (SS) is an autoimmune disorder characterized by chronic inflammation and destruction of salivary and lacrimal glands leading to dry mouth and dry eyes, respectively. Currently, the etiology of SS is unknown and the current therapies have no permanent benefit; therefore, new approaches are necessary to effectively treat this condition. Resolvins are highly potent endogenous lipid mediators that are synthesized during the resolution of inflammation to restore tissue homeostasis. Previous studies indicate that the resolvin family member, RvD1, binds to the ALX/FPR2 receptor to block inflammatory signals caused by tumor necrosis factor-alpha (TNF-α) in the salivary epithelium. More recently, the corticosteroid, dexamethasone (DEX), was shown to be effective in reducing salivary gland inflammation. However, DEX, as with other corticosteroids, elicits adverse secondary effects that could be ameliorated when used in smaller doses. Therefore, we investigated whether the more stable aspirin-triggered (AT) epimer, AT-RvD1, combined with reduced doses of DEX is effective in treating TNF-α-mediated disruption of polarized rat parotid gland (Par-C10) epithelial cell clusters. Our results indicate that AT-RvD1 and DEX individually reduced TNF-α-mediated alteration in the salivary epithelium (i.e, maintained cell cluster formation, increased lumen size, reduced apoptosis, and preserved cell survival signaling responses) as compared to untreated cells. Furthermore, AT-RvD1 combined with a reduced dose of DEX produced stronger responses (i.e., robust salivary cell cluster formation, larger lumen sizes, further reduced apoptosis, and sustained survival signaling responses) as compared to those observed with individual treatments. These studies demonstrate that AT-RvD1 combined with DEX is highly effective in treating TNF-α-mediated disruption of salivary gland epithelium.

What can Sjögren's syndrome-like disease in mice contribute to human Sjögren's syndrome?

For decades, Sjögren's syndrome (SS) and Sjögren's syndrome-like (SS-like) disease in patients and mouse models, respectively, have been intensely investigated in attempts to identify the underlying etiologies, the pathophysiological changes defining disease phenotypes, the nature of the autoimmune responses, and the propensity for developing B cell lymphomas. An emerging question is whether the generation of a multitude of mouse models and the data obtained from their studies is actually important to the understanding of the human disease and potential interventional therapies. In this brief report, we comment on how and why mouse models can stimulate interest in specific lines of research that apparently parallel aspects of human SS. Focusing on two mouse models, NOD and B6·Il14α, we present the possible relevance of mouse models to human SS, highlighting a few selected disease-associated biological processes that have baffled both SS and SS-like investigations for decades.

Age-related spontaneous lacrimal keratoconjunctivitis is accompanied by dysfunctional T regulatory cells

In both humans and animal models, the development of Sjögren syndrome (SS) and non-SS keratoconjunctivitis sicca (KCS) increases with age. Here, we investigated the ocular surface and lacrimal gland (LG) phenotype of NOD.B10.H2^b mice at 7-14, 45-50, and 96-100 weeks. Aged mice develop increased corneal permeability, CD4⁺ T-cell infiltration, and conjunctival goblet cell loss. Aged mice have LG atrophy with increased lymphocyte infiltration and inflammatory cytokine levels. An increase in the frequency of CD4⁺Foxp3⁺ T regulatory cells (Tregs) was observed with age in the cervical lymph node (CLN), spleen, and LG. These CD4⁺CD25⁺ cells lose suppressive ability, while maintaining expression of Foxp3 (forkhead box P3) and producing interleukin-17 (IL-17) and interferon-γ (IFN-γ). An increase of Foxp3⁺IL-17⁺ or Foxp3⁺IFN-γ⁺ cells was observed in the LG and LG-draining CLN. In adoptive transfer experiments, recipients of either purified Tregs or purified T effector cells from aged donors developed lacrimal keratoconjunctivitis, whereas recipients of young Tregs or young T effector cells failed to develop disease. Overall, these results suggest inflammatory cytokine-producing CD4⁺Foxp3⁺ cells participate in the pathogenesis of age-related ocular surface disease.

Osteopontin Bridging Innate and Adaptive Immunity in Autoimmune Diseases

Osteopontin (OPN) regulates the immune response at multiple levels. Physiologically, it regulates the host response to infections by driving T helper (Th) polarization and acting on both innate and adaptive immunity; pathologically, it contributes to the development of immune-mediated and inflammatory diseases. In some cases, the mechanisms of these effects have been described, but many aspects of the OPN function remain elusive. This is in part ascribable to the fact that OPN is a complex molecule with several posttranslational modifications and it may act as either an immobilized protein of the extracellular matrix or a soluble cytokine or an intracytoplasmic molecule by binding to a wide variety of molecules including crystals of calcium phosphate, several cell surface receptors, and intracytoplasmic molecules. This review describes the OPN structure, isoforms, and functions and its role in regulating the crosstalk between innate and adaptive immunity in autoimmune diseases.

Review: The Lacrimal Gland and Its Role in Dry Eye

The human tear film is a 3-layered coating of the surface of the eye and a loss, or reduction, in any layer of this film may result in a syndrome of blurry vision and burning pain of the eyes known as dry eye. The lacrimal gland and accessory glands provide multiple components to the tear film, most notably the aqueous. Dysfunction of these glands results in the loss of aqueous and other products required in ocular surface maintenance and health resulting in dry eye and the potential for significant surface pathology. In this paper, we have reviewed products of the lacrimal gland, diseases known to affect the gland, and historical and emerging dry eye therapies targeting lacrimal gland dysfunction.

Early BAFF receptor blockade mitigates murine Sjögren's syndrome: Concomitant targeting of CXCL13 and the BAFF receptor prevents salivary hypofunction

Sjögren's syndrome (SS) is a debilitating autoimmune disease. Patients with SS may develop xerostomia. This process is progressive, and there are no therapeutics that target disease etiology. We hypothesized BAFF receptor (BAFFR) blockade would mitigate SS disease development, and neutralization of CXCL13 and BAFF signaling would be more efficacious than BAFFR blockade alone. We treated NOD/ShiLtJ SS mice with soluble BAFF receptor (BAFFR-Fc) or anti-CXCL13/BAFFR-Fc in combination, prior to the development of clinical disease. Our results show treatment with BAFFR-Fc reduced peripheral B cell numbers and decreased sialadenitis. In addition, this treatment reduced total serum immunoglobulin as well as IgG and IgM specific anti-nuclear autoantibodies. NOD/ShiLtJ mice treated with BAFFR-Fc and anti-CXCL13 antibody were protected from salivary deficits. Results from this study suggest blockade of CXCL13 and BAFFR together may be an effective therapeutic strategy in preventing salivary hypofunction and reducing autoantibody titers and sialadenitis in patients with SS.

Dysregulated co-stimulatory molecule expression in a Sjögren's syndrome mouse model with potential implications by microRNA-146a

Sjögren's syndrome (SjS) is an autoimmune condition that primarily affects salivary and lacrimal glands, causing loss of secretion. We have previously shown that microRNA-146a (miR-146a) is over-expressed in the salivary glands and peripheral blood mononuclear cells (PBMC) of SjS-prone mice (C57BL/6.NOD-Aec1Aec2, B6DC) and in PBMC of SjS patients. The purpose of this research was to identify a target molecule of miR-146a and identify subpopulations of cells affected by altered miR-146a in the salivary glands of SjS-prone mice. In silico analyses identified costimulatory molecule CD80 as a potential target of miR-146a. Luciferase assay of the human CD80 3'untranslated region demonstrated miR-146a directly inhibited CD80 protein expression as indicated by reduced luciferase reporter expression and an examination of B6DC salivary glands revealed a reduction in CD80 protein. More interestingly, the specific reduction in CD80 protein was detected from the salivary gland epithelial cell population and in interstitial dendritic cells in the glands as well. The reduction in CD80 protein levels in salivary gland epithelial cells were negatively associated with elevated miR-146a expression. Therefore, this study provides the first indication that salivary gland epithelial cells may be critically involved in SjS progression by altering CD86:CD80 protein ratio in response to miR-146a upregulation.

Analysis of IgM antibody production and repertoire in a mouse model of Sjögren's syndrome

This study tested the hypothesis that B cells from salivary tissue are distinct in terms of proliferative capacity, immunoglobulin M secretion, repertoire, and autoantibody enrichment in Sjögren's syndrome. We sorted purified B cells from the spleen, cervical lymph nodes, and submandibular glands of a primary Sjögren's syndrome mouse model (Id3(-/-)). Enzyme-linked immunospot and proliferation assays were performed with stimulated B cells. We single-cell sorted B cells from the spleen, cervical lymph nodes, and submandibular gland tissue from Sjögren's syndrome mice and sequenced immunoglobulin M heavy-chain variable regions. Finally, autoantigen arrays were performed using immunoglobulin M derived from sera, cervical lymph nodes, spleens, and submandibular gland tissue of Id3(-/-) animals. Results suggest B cells from salivary tissue of Sjögren's syndrome mice are similar to those from secondary immune sites in terms of proliferative and secretory capacity. However, differences in repertoire usage, heavy chain complementarity-determining region 3 length, mutational frequency, and N region addition were observed among B cells derived from submandibular gland, cervical lymph node, and spleen tissue. Moreover, autoantigen array data show immunoglobulin M from salivary B cells have enriched specificity for Ro (Sjögren's syndrome A) and La (Sjögren's syndrome B). All together, these data suggest salivary B cells have unique repertoire characteristics that likely influence autoantigen binding and contribute to Sjögren's syndrome disease in a tissue-specific manner.

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.

Changes in the Submandibular Salivary Gland Epithelial Cell Subpopulations During Progression of Sjögren's Syndrome-Like Disease in the NOD/ShiLtJ Mouse Model

Sjögren's syndrome (SS), an autoimmune exocrinopathy, is associated with dysfunction of the secretory salivary gland epithelium, leading to xerostomia. The etiology of SS disease progression is poorly understood as it is typically not diagnosed until late stage. Since mouse models allow the study of disease progression, we investigated the NOD/ShiLtJ mouse to explore temporal changes to the salivary epithelium. In the NOD/ShiLtJ model, SS presents secondary to autoimmune diabetes, and SS disease is reportedly fully established by 20 weeks. We compared epithelial morphology in the submandibular salivary glands (SMG) of NOD/ShiLtJ mice with SMGs from the parental strain at 12, 18, and 22 weeks of age and used immunofluorescence to detect epithelial proteins, including the acinar marker, aquaporin 5, ductal cell marker, cytokeratin 7, myoepithelial cell marker, smooth muscle α-actin, and the basal cell marker, cytokeratin 5, while confirming immune infiltrates with CD45R. We also compared these proteins in the labial salivary glands of human SS patients with control tissues. In the NOD/ShiLtJ SMG, regions of lymphocytic infiltrates were not associated with widespread epithelial tissue degradation; however, there was a decrease in the area of the gland occupied by secretory epithelial cells in favor of ductal epithelial cells. We observed an expansion of cells expressing cytokeratin 5 within the ducts and within the smooth muscle α-actin(+) basal myoepithelial population. The altered acinar/ductal ratio within the NOD/ShiLtJ SMG likely contributes to salivary hypofunction, while the expansion of cytokeratin 5 positive-basal cells may reflect loss of function or indicate a regenerative response.

The clinical relevance of animal models in Sjögren's syndrome: the interferon signature from mouse to man

Mouse models have been widely used to elucidate the pathogenic mechanisms of human diseases. The advantages of using these models include the ability to study different stages of the disease with particular respect to specific target organs, to focus on the role of specific pathogenic factors and to investigate the effect of possible therapeutic interventions. Sjögren's syndrome (SS) is a systemic autoimmune disease, characterised by lymphocytic infiltrates in the salivary and lacrimal glands. To date, effective therapy is not available and treatment has been mainly symptomatic. Ongoing studies in murine models are aimed at developing more effective and targeted therapies in SS. The heterogeneity of SS will most probably benefit from optimising therapies, tailored to specific subgroups of the disease. In this review, we provide our perspective on the importance of subdividing SS patients according to their interferon signature, and recommend choosing appropriate mouse models for interferon-positive and interferon-negative SS subtypes. Murine models better resembling human-disease phenotypes will be essential in this endeavour.

The osteopontin transgenic mouse is a new model for Sjögren's syndrome

Osteopontin (Opn) is a cytokine involved in both physiological and pathological processes, and is elevated in many autoimmune diseases. Sjögren's syndrome (SS) is an autoimmune disease with a strong female predilection characterized by lymphocytic infiltration of exocrine glands. We hypothesized that Opn contributes to SS pathogenesis. We examined an established SS model and found increased Opn locally and systemically. Next, we examined Opn transgenic (Opn Tg) mice for evidence of SS. Opn Tg animals exhibited lymphocytic infiltration of salivary and lacrimal glands, and Opn co-localized with the infiltrates. Moreover, saliva production was reduced, and SS autoantibodies were observed in the serum of these mice. Finally, female Opn Tg mice showed more severe disease compared to males. Taken together, these data support a role for Opn in SS pathogenesis. We identify a new model of spontaneous SS that recapitulates the human disease in terms of sex predilection, histopathology, salivary deficits, and autoantibodies.

Sjögren's syndome and extragonadal sex steroid formation: a clue to a better disease control?

Sjögren's syndrome (SS) is an autoimmune disease characterized by lymphoplasmacytoid focal adenitis leading to mucosal dryness, with 9:1 female dominance and peak incidence at menopause. Due to autoimmune adenitis it can be speculated that the normal epithelial cell renewal has failed, possibly as a result of local intracrine failure to process dehydroepiandrosterone (DHEA) to dihydrotestosterone (DHT). Local intracrine/-cellular DHT deficiency seems to predispose to SS if estrogens are low, in menopausal women and in men. This intracrine failure could be the initial noxious stimulus, factor X, initiating the development of SS. Abnormal release and presentation of exocrine gland-derived antigens (Ag-epitopes), in a complex with major histocompatibility complex class II (MHC II), by migratory dendritic cells (DC) activates T-cells in the regional lymph nodes. B-cells with the same specificity capture and present self-Ag to Th-cells which provide T-cell help. B-cells transform to plasma cells and start to produce autoantibodies (Ab) against these T-cell-dependent Ag. Ab against SS-A/Ro and SS-B/La ribonucleoproteins occur only in HLA-DQw2.1/DQw6 heterozygous individuals, but hY-RNA and RNA polymerase III transcripts in these Ag may in all SS patients stimulate toll-like receptors (TLR) 7 and 9 of the plasmacytoid DCs, because IFN-α and IFN-signature are produced. CD8+αEβ7+cytotoxic T-cells activated via cross-presentation recirculate to attack intracrine-deficient, apoptotic epithelial cells expressing self-Ag on their surface. Exocrine glands fall into the sphere of mucosal/gut-associated lymphatic tissue. This together with immune complexes spreads the immunological memory/aggression to extra-glandular sites explaining the systemic nature of the syndrome. Secondary SS could be explained by disturbed lymphocyte recirculation. There is no conclusive evidence that SS in those few men affected is more severe than in women, suggesting that sex steroid endo-/intracrinology has its major impact on the target tissue, not on immune modulation. This article is part of a Special Issue entitled 'Essential role of DHEA'.

Reduction of T cell receptor diversity in NOD mice prevents development of type 1 diabetes but not Sjögren's syndrome

Non-obese diabetic (NOD) mice are well-established models of independently developing spontaneous autoimmune diseases, Sjögren’s syndrome (SS) and type 1 diabetes (T1D). The key determining factor for T1D is the strong association with particular MHCII molecule and recognition by diabetogenic T cell receptor (TCR) of an insulin peptide presented in the context of I-A^g7 molecule. For SS the association with MHCII polymorphism is weaker and TCR diversity involved in the onset of the autoimmune phase of SS remains poorly understood. To compare the impact of TCR diversity reduction on the development of both diseases we generated two lines of TCR transgenic NOD mice. One line expresses transgenic TCRβ chain originated from a pathogenically irrelevant TCR, and the second line additionally expresses transgenic TCRα^mini locus. Analysis of TCR sequences on NOD background reveals lower TCR diversity on Treg cells not only in the thymus, but also in the periphery. This reduction in diversity does not affect conventional CD4⁺ T cells, as compared to the TCR^mini repertoire on B6 background. Interestingly, neither transgenic TCRβ nor TCR^mini mice develop diabetes, which we show is due to lack of insulin B:9–23 specific T cells in the periphery. Conversely SS develops in both lines, with full glandular infiltration, production of autoantibodies and hyposalivation. It shows that SS development is not as sensitive to limited availability of TCR specificities as T1D, which suggests wider range of possible TCR/peptide/MHC interactions driving autoimmunity in SS.

Temporal histological changes in lacrimal and major salivary glands in mouse models of Sjogren's syndrome

Background

Evidence in imaging studies suggests that there may be differences in glandular involvement in Sjogren’s syndrome (SS) depending on the stage of the disease. No detailed histological studies are available to show if there are any such difference in glandular involvement at various time periods and stages of SS. This cross sectional study examines the inflammatory changes in mouse models of SS at various ages.

Methods

The histological changes in major salivary and lacrimal glands were studied at ages of 3, 6, 9, 12, 15 and 18 months in both sexes in well characterized mouse models of SS, non-obese diabetes mouse and Interleukin-14 alpha-transgenic mice.

Results

Our results indicate that early inflammation concurrently occur in submandibular and lacrimal glands around the age of 6 weeks. Parotid glands are involved much later in the course of SS with less severe inflammation. Sublingual glands are rarely involved.

Conclusions

Our conclusions are that SS may be an organ specific disease with early inflammation occurring in submandibular and lacrimal glands, followed by the parotid. Non organ specific events occur in later courses of the disease. The understanding of the disease progression is important in tailoring early local therapeutic interventions before complete destruction of salivary and lacrimal glands.

Effects of total glucosides of paeony for delaying onset of Sjogren's syndrome: an animal study

OBJECTIVE

To investigate the effectiveness of total glucosides of paeony (TGP) on Sjogren's syndrome (SS) using non-obese diabetic (NOD) mice model.

STUDY DESIGN

Twenty-seven 8-week-old female NOD mice were assigned into TGP group, hydroxychloroquine (HCQ) group and normal saline (NS) group, receiving corresponding drugs respectively and sacrificed at 24-week-old. Saliva flow rate (SFR), ration of regulatory T cells, level of anti-SSA/SSB, histological changes in submandibular glands (SMG) and microarray analysis were assessed. The data were analyzed using SPSS.

RESULTS

Compared to NS group, in TGP group, SFR, SMG index and the ration of regulatory T cells were significantly higher, while anti-SSA/SSB and lymphocytic foci were significantly lower. HCQ group demonstrated similar results except SMG index. Altered gene expression was found in 10.71% of TGP and 13.09% of HCQ of the profile.

CONCLUSION

TGP demonstrated a similar effectiveness as HCQ in delaying the onset of SS-like disease in NOD mice.

The Interferon-Signature of Sjögren's Syndrome: How Unique Biomarkers Can Identify Underlying Inflammatory and Immunopathological Mechanisms of Specific Diseases

Innate immune responses direct the nature and specificity of downstream adaptive responses in autoimmune diseases. One of the strongest markers of innate immunity is the up-regulated expression of interferon (IFN) and IFN-responsive/stimulated genes (IRGs/ISGs). While multiple IRGs are induced during the innate phase of host responses, transcriptome data suggest unique IRG-signatures for different diseases. Sjögren's syndrome (SjS) is characterized by chronic immune attacks against exocrine glands leading to exocrine dysfunction, plus strong up-regulated expressions of IFN IRG transcripts. Genome-wide transcriptome analyses indicate that differentially expressed IRGs are restricted during disease development and therefore define underlying etiopathological mechanisms. Here we review the innate immune-associated IFN-signature of SjS and show how differential gene expressions of IRG/ISG sets interact molecularly and biologically to identify critical details of SjS etiopathogenesis.

Local administration of soluble CD40:Fc to the salivary glands of non-obese diabetic mice does not ameliorate autoimmune inflammation

Objective

CD40–CD154 (CD40 ligand) interaction in the co-stimulatory pathway is involved in many (auto)immune processes and both molecules are upregulated in salivary glands of Sjögren’s syndrome (SS) patients. Interference within the CD40 pathway has ameliorated (auto)inflammation in a number of disease models. To test the potential role of the CD40 pathway in loss of gland function and inflammation in SS, an inhibitor of CD40-CD154 interaction was overexpressed in the salivary glands (SGs) of a spontaneous murine model of SS; the Non-Obese Diabetic (NOD) mouse.

Materials and Methods

At different disease stages an adeno associated viral vector encoding CD40 coupled to a human Fc domain (CD40:Fc) was injected locally into the SGs of NOD mice. Delivery was confirmed by PCR. The overall effect on local inflammation was determined by assessment of the focus score (FS), quantification of infiltrating cell types, immunoglobulin levels, and microarray analysis. The effect on SG function was determined by measuring stimulated salivary flow.

Results

CD40:Fc was stably expressed in the SG of NOD mice, and the protein was secreted into the blood stream. Microarray analysis revealed that expression of CD40:Fc affected the expression of many genes involved in regulation of the immune response. However, FS, infiltrating cell types, immunoglobulin levels, and salivary gland output were similar for treated and control mice.

Discussion

Although endogenous CD40 is expressed in SG inflammatory foci in the SG of NOD mice, the expression of soluble CD40:Fc did not lead to reduced overall inflammation and/or improved salivary gland function. These data indicate possible redundancy of the CD40 pathway in the SG and suggests that targeting CD40 alone may not be sufficient to alter the disease phenotype.

Deletion of interferon-γ delays onset and severity of dacryoadenitis in CD25KO mice

Introduction

To investigate the role of interferon-gamma (IFN-γ) in the onset and severity of dacryoadenitis in the CD25 knockout (KO) mouse model of Sjögren Syndrome.

Methods

CD25/IFN-γ double KO (γDKO) mice were created by crossbreeding CD25KO and IFN-γKO mice. Mice were used at 8, 12, and 16 weeks. Lacrimal gland (LG) infiltrating lymphocytes were characterized with flow cytometry. Tear epidermal growth factor (EGF) concentration was measured with enzyme-linked immunosorbent assay (ELISA). Quantitative polymerase chain reaction (PCR) evaluated T-cell-related cytokines in LGs. Serum autoantibodies against M3R in LG lysates were detected with Western blot.

Results

γDKO LG showed lower lymphocytic infiltration at 8 weeks than in the CD25KO parental strain (˜20% versus ˜60%, respectively), which increased to CD25KO levels at 16 weeks. Flow-cytometry analysis showed an increase in CD4⁺ and CD8⁺ T cells with aging in γDKO LG, similar to that in CD25KO. γDKO had lower levels of interleukin (IL)-17A, transforming growth-factor (TGF)-β1, IL-21, and CCL20, and higher IL-1β and IL-13 mRNA transcripts in the LG than in the parental CD25KO strain. Autoantibodies to M3R were observed in both strains and significantly increased with aging in both strains. CD25KO mice had very low tear EGF concentrations at all ages, whereas the ear EGF concentration in γDKO mice significantly decreased with aging and inversely correlated with the presence of M3R autoantibodies and the degree of LG CD4 and CD8⁺ T-cell infiltration.

Conclusions

The deletion of IFN-γ in the CD25KO mice strain delays glandular destruction and preserves glandular function. M3R autoantibodies increased with aging in both the γDKO and the CD25KO strains. The decrease in LG function in γDKO correlated with the degree of T-cell infiltration and the presence of M3R autoantibodies.

Destruction of salivary and lacrimal glands by Th1-polarized reaction in a model of secondary Sjögren's syndrome in lupus-prone female NZB × NZWF(1) mice

T helper (Th)1/Th2 balance determines the direction of some kinds of autoimmune diseases. The involvement of acini areas by CD4(+) helper T(Th) cell subset in submandibular and lacrimal glands are largely unknown in secondary Sjögren's syndrome (sSjS) with systemic lupus erythematosus (SLE). Submandibular and lacrimal glands were examined immunopathologically in lupus-prone female NZB × NZW(B/W)F(1) mice, model for human sSjS with SLE. Dacryoadenitis and sialoadenitis with renal failure developed with age. Infiltration of lymphoid cells (lymphocytes and plasma cells) expanded from the periductal areas in striated ducts to the acini, and the isolated foci in the acini were observed in those organs. The destruction of duct and acini epithelium, including the myoepithelium, was induced by interferon (IFN)-γ(+) and IgG2a(+) lymphoid cells, but not by interleukin(IL)-4(+), IL-5(+), IL-13(+), and IgG1(+) lymphoid cells. Compared with IL-5 and IL-13, high values of IFN-γ were produced systemically at various ages. Also local expression of IFN-γ mRNA was higher than that of IL-4 mRNA. The result suggests that the acini destruction in submandibular and lacrimal glands may be induced by systemic and local Th1 cell dominant reactions in lupus-prone B/WF(1) mice with sSjS.

Current Aspects of Pathogenesis in Sjögren's Syndrome

Sjögren's syndrome is a chronic autoimmune process that primarily affects the exocrine glands and leads to their functional impairment. The exocrine gland involvement is characterized by a focal, mononuclear cell infiltrate which is accumulated around ducts and, in some patients, extends and replaces the secretory functional units. The mechanisms of this autoimmune 'exocrinopathy' are not fully understood. The immune attack that follows activation or apoptosis of glandular epithelial cells exposing autoantigens in genetically predisposed individuals may drive the immune-mediated tissue injury. Abnormalities related to the upregulation of type I interferon-regulated genes (interferon signature), abnormal expression of B-cell-activating factor (BAFF) and activation of the IL-23/TH17 pathway are among the immune mediators implicated in the pathogenesis of autoimmune lesions within the salivary glands. Such abnormalities demonstrate the complex interplay between innate and adaptive immunity that contributes to autoimmune 'exocrinopathy'.

STIM1 and STIM2 protein deficiency in T lymphocytes underlies development of the exocrine gland autoimmune disease, Sjogren's syndrome

Primary Sjögren's Syndrome (pSS) is an autoimmune disease involving salivary and other exocrine glands that leads to progressive lymphocytic infiltration into the gland, tissue damage, and secretory defects. The mechanism underlying this disease remains poorly understood. Here we report that mice with T-cell-targeted deletion of Stromal Interaction Molecule (STIM) 1 and STIM2 [double-knockout (DKO)] mice develop spontaneous and severe pSS-like autoimmune disease, displaying major hallmarks of the disease. In DKO mice, diffuse lymphocytic infiltration was seen in submandibular glands, a major target of pSS, by age 6 wk, progressing to severe inflammation by age 12 wk. Sjögren's syndrome-specific autoantibodies (SSA/Ro and SSB/La) were detected in the serum, and progressive salivary gland destruction and loss of fluid secretion were also seen. Importantly, we report that peripheral blood mononuclear cells as well as lymphocytic infiltrates in submandibular glands from patients with pSS demonstrated significant reductions in STIM1 and STIM2 proteins. Store-operated calcium entry was also reduced in peripheral blood mononuclear cells from pSS patients compared with those from healthy controls. Thus, deficiency of STIM1 and STIM2 proteins in T cells, and consequent defects in Ca(2+) signaling, are associated with salivary gland autoimmunopathy in DKO mice and pSS patients. These data reveal a previously unreported link between STIM1 and STIM2 proteins and pSS.

Involvement of toll-like receptors in autoimmune sialoadenitis of the non-obese diabetic mouse

The aim of this study was to characterize the expression of Toll-like receptors (TLRs) during the development of sialoadenitis in the non-obese diabetic mouse. Submandibular glands were dissected from non-obese diabetic mice at 4, 8, 10, 12, and 16 weeks of age. The mRNA expression levels of TLR1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 12, 13, MyD88, and TRIF was quantified using real-time reverse transcription polymerase chain reaction. The mRNA expression levels in 4-week-old non-obese diabetic mice were used as controls. The expression levels of TLR1, 2, 4, and 9 were significantly higher at 8, 10, 12, and 16 weeks than the levels in the controls. The expression level of TLR3 was significantly higher at 16 weeks than in the controls. A group of mice were given drinking water containing 4.75% chloroquine starting at 4 weeks. Chloroquine caused a significant decrease in the expression of TLR1, 2, 3, 4, and 9 at 16 weeks compared with control mice who did not receive chloroquine. The areas of lymphocyte infiltration seen on serial sections of submandibular glands in the mice receiving chloroquine were significantly smaller than the areas of infiltration in control glands. Increased expression of Toll-like receptors may be involved in the development and/or progression of sialoadenitis in the non-obese diabetic mouse. Toll-like receptors may be a therapeutic target for autoimmune sialoadenitis.