Balance of proliferation and cell death between thyrocytes and myofibroblasts regulates thyroid fibrosis in granulomatous experimental autoimmune thyroiditis (G-EAT)

Unraveling the molecular architecture of autoimmune thyroid diseases at spatial resolution

Autoimmune thyroid diseases (AITD) such as Graves' disease (GD) or Hashimoto's thyroiditis (HT) are organ-specific diseases that involve complex interactions between distinct components of thyroid tissue. Here, we use spatial transcriptomics to explore the molecular architecture, heterogeneity and location of different cells present in the thyroid tissue, including thyroid follicular cells (TFCs), stromal cells such as fibroblasts, endothelial cells, and thyroid infiltrating lymphocytes. We identify damaged antigen-presenting TFCs with upregulated CD74 and MIF expression in thyroid samples from AITD patients. Furthermore, we discern two main fibroblast subpopulations in the connective tissue including ADIRF+ myofibroblasts, mainly enriched in GD, and inflammatory fibroblasts, enriched in HT patients. We also demonstrate an increase of fenestrated PLVAP+ vessels in AITD, especially in GD. Our data unveil stromal and thyroid epithelial cell subpopulations that could play a role in the pathogenesis of AITD.

Increased SLAMF7+CD8+ T cells are associated with the pathogenesis of experimental autoimmune pancreatitis in mice

BACKGROUND

IgG4-related autoimmune pancreatitis (AIP) is considered to be a T cell-mediated autoimmune disease. However, CD8+ T cells have only received brief mention, and have yet to be completely studied. The study aimed to investigate the expression of signaling lymphocytic activation molecule family 7 (SLAMF7) on CD8+ T cells and the features of SLAMF7+CD8+ T cells in MRL/Mp mice with AIP.

METHODS

A murine model of AIP was established by intraperitoneal injection with polyinosinic:polycytidylic acid (poly I:C) for 8 weeks. Dexamethasone treatment was daily administrated for the last 2 weeks during a 6-week course of poly I:C. SLAMF7 expression on CD8+ T cells in the spleen and pancreas was detected by flow cytometry. Granzyme B (GZMB) and cytokines including IFN-γ, TNF-α, and IL-2, were monitored in an in vitro T cell activation assay. Dexamethasone suppression assays were performed to downregulate SLAMF7 expression on T cells upon T cell receptor stimulation.

RESULTS

AIP in MRL/Mp mice was induced by repeated intraperitoneal administration of poly I:C and CD8+ T cells were increased in the inflamed pancreas. SLAMF7+CD8+ T cells were elevated in the spleen and pancreas of AIP mice. SLAMF7+CD8+ T subsets produced more GZMB, IFN-γ, TNF-α and IL-2 than SLAMF7-CD8+ T subsets. Dexamethasone treatment ameliorated pancreatic inflammatory and fibrosis of AIP. Dexamethasone could downregulate SLAMF7+CD8+ T cells and reduce GZMB, IFN-γ and TNF-α levels both in vitro and in vivo.

CONCLUSIONS

Increased SLAMF7+CD8+ T cells exhibit enhanced cytotoxicity and cytokines secretion capacity, which may be involved in the pathogenesis of AIP.

New insights into immune cells cross-talk during IgG4-related disease

Immunoglobulin G4-related disease (IgG4-RD) is a newly acknowledged entity, characterized by an immune-mediated fibro-inflammatory process affecting virtually all organs, with infiltration of IgG4⁺ bearing plasma cells. Until today the pathogenesis of IgG4-RD remains unknown. Treatment with anti-CD20 monoclonal antibodies efficiently induced remission and attenuated the secretory phenotype of myofibroblasts responsible of uncontrolled collagen deposition. This supports the pathogenic role of the adaptive immunity, particularly B cell compartment and B cell/T cell interaction. Latest studies have also highlighted the importance of innate immune system that has been underestimated before and the key role of a specific T cell subset, T follicular helper cells that are involved in IgG4-class-switching and plasmablast differentiation. In this review, we aim to review the most recent knowledge of innate immunity, T and B cells involvement in IgG4-RD, and introduce tertiary lymphoid organs (TLO) as a potential marker of relapse in this condition.

Clonally expanded cytotoxic CD4+ T cells and the pathogenesis of IgG4-related disease

IgG4-related disease (IgG4-RD) is a systemic condition of unknown cause characterized by highly fibrotic lesions, with dense lymphoplasmacytic infiltrates containing a preponderance of IgG4-expressing plasma cells. CD4⁺ T cells and B cells constitute the major inflammatory cell populations in IgG4-RD lesions. IgG4-RD patients with active, untreated disease show a marked expansion of plasmablasts in the circulation. Although the therapeutic depletion of B cells suggests a role for these cells in the disease, a direct role for B cells or IgG4 in the pathogenesis of IgG4-RD is yet to be demonstrated. Among the CD4⁺ T-cell subsets, Th2 cells were initially thought to contribute to IgG4-RD pathogenesis, but many previous studies were confounded by the concomitant history of allergic diseases in the patients studied and the failure to use multi-color staining to definitively identify T-cell subsets in tissue samples. More recently, using an unbiased approach to characterize CD4⁺ T-cell subsets in patients with IgG4-RD - based on their clonal expansion and ability to infiltrate affected tissue sites - CD4⁺ CTLs have been identified as the major CD4⁺ T-cell subset in disease lesions as well as in the circulation. CD4⁺ CTLs in affected tissues secrete pro-fibrotic cytokines including IL-1β, TGF-β1, and IFN-γ as well as cytolytic molecules such as perforin and granzymes A and B. In this review, we examine possible mechanisms by which activated B cells and plasmablasts may collaborate with the expanded CD4⁺ CTLs in driving the fibrotic pathology of the disease and describe the lacunae in the field and in our understanding of IgG4-RD pathogenesis.

Macrophage infiltration into thyroid follicles: an immunohistochemical study using donated elderly cadavers

To describe and discuss the morphology of the aged thyroid gland, with particular reference to the contribution of macrophages.With the aid of immunohistochemistry, we examined 1) macrophage accumulation, 2) infiltration of lymphocytes, and 3) the size and density of follicles in the unilateral lobe of the thyroid gland obtained from elderly donated cadavers (mean age, 84 years) without macroscopic malignancy. Each almost entire unilateral lobe of the thyroid showed 2554-9910 follicles per section, and each of the follicles ranged in area from 0.014-0.072 mm². We often found evidence suggesting absorption and fusion of follicles to provide a larger colloidal lumen, containing small follicles and/or epithelial fragments. In addition to dendritic perifollicular macrophages, large and round macrophages often formed clusters in the colloid. Colloidal lumina with weak macrophage immunoreactivity were intermingled with those showing strong reactivity. Notably, a greater number of macrophage foci in the colloid was usually associated with a lower density of perifollicular macrophages. Likewise, perifollicular macrophages were not always associated with lymphocyte infiltration. In the elderly, the initial appearance of colloidal macrophages does not appear to be associated with perifollicular infiltration of mononuclear cells. Macrophage invasion into a follicle might depend on the functional state of each follicle. After destruction of a follicle, a macrophage cluster appears to remain in the perifollicular tissue, and perhaps lymphocyte infiltration occurs secondarily. This course is likely to represent the process of degeneration of the thyroid gland structure with age.

Clonal expansion of CD4(+) cytotoxic T lymphocytes in patients with IgG4-related disease

BACKGROUND

IgG4-related disease (IgG4-RD) is a systemic condition of unknown cause characterized by highly fibrotic lesions with dense lymphoplasmacytic infiltrates. CD4(+) T cells constitute the major inflammatory cell population in IgG4-RD lesions.

OBJECTIVE

We used an unbiased approach to characterize CD4(+) T-cell subsets in patients with IgG4-RD based on their clonal expansion and ability to infiltrate affected tissue sites.

METHODS

We used flow cytometry to identify CD4(+) effector/memory T cells in a cohort of 101 patients with IgG4-RD. These expanded cells were characterized by means of gene expression analysis and flow cytometry. Next-generation sequencing of the T-cell receptor β chain gene was performed on CD4(+)SLAMF7(+) cytotoxic T lymphocytes (CTLs) and CD4(+)GATA3(+) TH2 cells in a subset of patients to identify their clonality. Tissue infiltration by specific T cells was examined by using quantitative multicolor imaging.

RESULTS

CD4(+) effector/memory T cells with a cytolytic phenotype were expanded in patients with IgG4-RD. Next-generation sequencing revealed prominent clonal expansions of these CD4(+) CTLs but not CD4(+)GATA3(+) memory TH2 cells in patients with IgG4-RD. The dominant T cells infiltrating a range of inflamed IgG4-RD tissue sites were clonally expanded CD4(+) CTLs that expressed SLAMF7, granzyme A, IL-1β, and TGF-β1. Clinical remission induced by rituximab-mediated B-cell depletion was associated with a reduction in numbers of disease-associated CD4(+) CTLs.

CONCLUSIONS

IgG4-RD is prominently linked to clonally expanded IL-1β- and TGF-β1-secreting CD4(+) CTLs in both peripheral blood and inflammatory tissue lesions. These active, terminally differentiated, cytokine-secreting effector CD4(+) T cells are now linked to a human disease characterized by chronic inflammation and fibrosis.

NGF Modulates trkANGFR/p75NTR in αSMA-Expressing Conjunctival Fibroblasts from Human Ocular Cicatricial Pemphigoid (OCP)

Objective

In a previous study, we reported the upregulation of Nerve Growth Factor (NGF) and trkA^NGFR expression in Ocular Cicatricial Pemphigoid (OCP), an inflammatory and remodeling eye disease. Herein, we hypothesize a potential NGF-driven mechanism on fibroblasts (FBs) during OCP remodeling events. To verify, human derived OCP-FBs were isolated and characterized either at baseline or after NGF exposure.

Materials and Methods

Conjunctival biopsies were obtained from 7 patients having OCP and 6 control subjects (cataract surgery). Both conjunctivas and primary FB cultures were characterised for αSMA, NGF and trkA^NGFR/p75^NTR expression. Subcultures were exposed to NGF and evaluated for αSMA, NGF, trkA^NGFR/p75^NTR expression as well as TGFβ1/IL4 release. For analysis, early and advanced subgroups were defined according to clinical parameters.

Results

OCP-conjunctivas showed αSMA-expressing FBs and high NGF levels. Advanced OCP-FBs showed higher αSMA expression associated with higher p75^NTR and lower trkA^NGFR expression, as compared to early counterparts. αSMA expression was in keeping with disease severity and correlated to p75^NTR. NGF exposure did not affect trkA^NGFR levels in early OCP-FBs while decreased both αSMA/p75^NTR expression and TGFβ1/IL4 release. These effects were not observed in advanced OCP-FBs.

Conclusions

Taken together, these data are suggestive for a NGF/p75^NTR task in the potential modulation of OCP fibrosis and encourages further studies to fully understand the underlying mechanism occurring in fibrosis. NGF/p75^NTR might be viewed as a potential therapeutic target.

NOD.H-2h4 mice: an important and underutilized animal model of autoimmune thyroiditis and Sjogren's syndrome

NOD.H-2h4 mice express the K haplotype on the NOD genetic background. They spontaneously develop thyroiditis and Sjogren's syndrome, but they do not develop diabetes. Although autoimmune thyroid diseases and Sjogren's syndrome are highly prevalent autoimmune diseases in humans, there has been relatively little emphasis on the use of animal models of these diseases for understanding basic mechanisms involved in development and therapy of chronic organ-specific autoimmune diseases. The goal of this review is to highlight some of the advantages of NOD.H-2h4 mice for studying basic mechanisms involved in development of autoimmunity. NOD.H-2h4 mice are one of relatively few animal models that develop organ-specific autoimmune diseases spontaneously, i.e., without a requirement for immunization with antigen and adjuvant, and in both sexes in a relatively short period of time. Thyroiditis and Sjogren's syndrome in NOD.H-2h4 mice are chronic autoimmune diseases that develop relatively early in life and persist for the life of the animal. Because the animals do not become clinically ill, the NOD.H-2h4 mouse provides an excellent model to test therapeutic protocols over a long period of time. The availability of several mutant mice on this background provides a means to address the impact of particular cells and molecules on the autoimmune diseases. Moreover, to our knowledge, this is the only animal model in which the presence or absence of a single cytokine, IFN-γ, is sufficient to completely inhibit one autoimmune thyroid disease, with a completely distinct autoimmune thyroid disease developing when it is absent.

TRAIL and DR5 promote thyroid follicular cell apoptosis in iodine excess-induced experimental autoimmune thyroiditis in NOD mice

Death receptor-mediated apoptosis has been implicated in target organ destruction in patients with chronic autoimmune thyroiditis. Several apoptosis signaling pathways, such as Fas ligand and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), have been shown to be active in thyroid cells and may be involved in destructive thyroiditis. Thyroid toxicity of iodide excess has been demonstrated in animals fed with an iodide-rich diet, but its pathogenic role remains unclear. The effects of excessive iodine on TRAIL and its death receptor expression in thyroid were investigated. Experimental autoimmune thyroiditis (EAT) was induced by excessive iodine and thyroglobulin (Tg) in non-obese diabetic mice. The expression of TRAIL and its death receptor DR5 was detected by immunofluorescence staining. Following administration of excessive iodine alone, Tg, and excessive iodine combined with Tg, TRAIL-positive cells appear not only in follicular cells but also in lymphocytes infiltrated in the thyroid, whereas DR5-positive cells appear only in follicular cells. Large numbers of CD3-positive cells and a few CD22-positive cells were detected in thyroid. A great amount of follicular cells were labeled specifically by terminal deoxynucleotide transferase-mediated deoxynucleotide triphosphate nick-end labeling assay. Taken together, our results suggest that excessive iodine could induce TRAIL and DR5 abnormal expression in thyroid. TRAIL band with DR5 to promote follicular cells apoptosis thus mediate thyroid destruction in EAT.

Interleukin-10 promotes resolution of granulomatous experimental autoimmune thyroiditis

Granulomatous experimental autoimmune thyroiditis (G-EAT) is induced by mouse thyroglobulin-sensitized splenocytes activated in vitro with mouse thyroglobulin and interleukin (IL)-12. Thyroid lesions reach maximal severity 20 days after cell transfer, and inflammation either resolves or progresses to fibrosis by day 60 depending on the extent of thyroid damage at day 20. Depletion of CD8(+) T cells inhibits G-EAT resolution. Our previous studies indicated that IL-10 was generally higher in G-EAT thyroids that resolved. Using both wild-type and IL-10(-/-) CBA/J mice, this study was undertaken to determine whether G-EAT resolution would be inhibited in the absence of IL-10. The results showed that either depletion of CD8(+) T cells or IL-10 deficiency increased fibrosis and inhibited resolution of inflammation. We also found a correlation between higher expression levels of proinflammatory cytokines and preferential expression levels of proapoptotic molecules, such as FasL and TRAIL, and antiapoptotic molecules, such as FLIP and Bcl-xL, in inflammatory cells from thyroids of both CD8-depleted and IL-10-deficient mice. Furthermore, many of the CD8(+) T cells were also IL-10(+). These results suggest that IL-10 plays an important role in G-EAT resolution and might promote resolution, at least in part, through its production in CD8(+) T cells. Further understanding of the mechanisms that promote the resolution of inflammation will facilitate the development of novel strategies for treating autoimmune diseases.

Expression of transgenic FLIP on thyroid epithelial cells inhibits induction and promotes resolution of granulomatous experimental autoimmune thyroiditis in CBA/J mice

Granulomatous experimental autoimmune thyroiditis (G-EAT) is induced by transfer of thyroglobulin-primed in vitro activated splenocytes. Thyroid lesions reach maximal severity 20 d later, and inflammation resolves or progresses to fibrosis by d 60, depending on the extent of thyroid damage at d 20. Depletion of CD8+ T cells inhibits G-EAT resolution. We showed that expression of Fas-associated death domain-like IL-1beta-converting enzyme inhibitory protein (FLIP) transgene (Tg) on thyroid epithelial cells (TECs) of DBA/1 mice had no effect on G-EAT induction but promoted earlier resolution of G-EAT. However, when CBA/J wild-type donor cells were transferred to transgenic CBA/J mice expressing FLIP on TECs, they developed less severe G-EAT than FLIP Tg- littermates. Both strains expressed similar levels of the FLIP Tg, but endogenous FLIP was up-regulated to a greater extent on infiltrating T cells during G-EAT development in DBA/1 compared with CBA/J mice. After transient depletion of CD8+ T cells, FLIP Tg+ and Tg- CBA/J recipients both developed severe G-EAT at d 20. Thyroid lesions in CD8-depleted Tg+ recipients were resolving by d 60, whereas lesions in Tg- littermates did not resolve, and most were fibrotic. FLIP Tg+ recipients had increased apoptosis of CD3+ T cells compared with Tg- recipients. The results indicate that transgenic FLIP expressed on TECs in CBA/J mice promotes G-EAT resolution, but induction of G-EAT is inhibited unless CD8+ T cells are transiently depleted.

Contrasting roles of IFN-gamma in murine models of autoimmune thyroid diseases

Interferon-gamma (IFN-gamma), a prototypic proinflammatory cytokine produced by several different cell types, including the Th1 subset of CD4(+) T cells, plays an important role in inflammation and autoimmune diseases. This review focuses on the varied and often contrasting roles of IFN-gamma in three murine models of autoimmune thyroid disease, experimentally induced autoimmune thyroiditis, the model of iodine-induced spontaneous autoimmune thyroiditis in NOD.H-2h4 mice and several different murine models of Graves' disease.

Murine FLIP transgene expressed on thyroid epithelial cells promotes resolution of granulomatous experimental autoimmune thyroiditis in DBA/1 mice

Granulomatous experimental autoimmune thyroiditis (G-EAT) is induced by mouse thyroglobulin-sensitized splenocytes activated in vitro with mouse thyroglobulin and interleukin-12. In wild-type (WT) DBA/1 recipients of WT donor splenocytes, thyroid lesions reach maximal severity at day 20, with ongoing inflammation and extensive fibrosis at day 60. Our previous studies indicated the site of expression of FLIP and Fas ligand [thyroid epithelial cells (TECs) versus inflammatory cells] differed in mice when lesions would resolve or progress to fibrosis. To test the hypothesis that expression of FLIP by TECs would promote earlier G-EAT resolution in DBA/1 mice, transgenic (Tg) DBA/1 mice expressing FLIP on TECs were generated. In FLIP Tg(+) and Tg(-) littermate recipients of WT donor splenocytes, G-EAT severity was comparable at day 20, but fibrosis was decreased, and many lesions resolved by day 60 in Tg(+) but not Tg(-) recipients. FLIP and Fas ligand were primarily expressed by TECs in Tg(+) recipients and by inflammatory cells in Tg(-) recipients at day 60. Apoptosis of inflammatory cells was greater, and expression of proinflammatory cytokines was decreased in thyroids of Tg(+) compared with Tg(-) recipients. These results are consistent with the hypothesis that transgenic expression of FLIP on thyroid epithelial cells promotes earlier resolution of granulomatous experimental autoimmune thyroiditis.

Decreasing TNF-alpha results in less fibrosis and earlier resolution of granulomatous experimental autoimmune thyroiditis

Granulomatous experimental autoimmune thyroiditis (G-EAT) is induced in DBA/1 mice by adoptive transfer of mouse thyroglobulin (MTg)-primed spleen cells. TNF-alpha is an important proinflammatory cytokine and apoptotic molecule involved in many autoimmune diseases. To study its role in G-EAT, anti-TNF-alpha mAb was given to recipient mice. Disease severity was comparable between mice with or without anti-TNF-alpha treatment at days 19-21, the time of maximal severity of G-EAT, suggesting TNF-alpha is not essential for development of thyroid inflammation. However, thyroid lesions resolved at day 48 in anti-TNF-alpha-treated mice, while thyroids of rat Ig-treated controls had fibrosis. These results suggested that reducing TNF-alpha contributed to resolution of inflammation and inhibited fibrosis. Gene and protein expression of inflammatory molecules was examined by RT-PCR and immunostaining, and apoptosis was detected using TUNEL staining and an apoptosis kit. Thyroids of anti-TNF-alpha-treated controls had reduced proinflammatory and profibrotic molecules, e.g., IFN-gamma, IL-1beta, IL-17, inducible NOS and MCP-1, at day 19 compared with thyroids of rat Ig-treated mice. There were more apoptotic thyrocytes in rat Ig-treated controls than in anti-TNF-alpha-treated mice. The site of expression of the anti-apoptotic molecule FLIP also differed between rat Ig-treated and anti-TNF-alpha-treated mice. FLIP was predominantly expressed by inflammatory cells of rat Ig-treated mice and by thyrocytes of anti-TNF-alpha-treated mice. These results suggest that anti-TNF-alpha may regulate expression of proinflammatory cytokines and apoptosis in thyroids, resulting in less inflammation, earlier resolution, and reduced fibrosis.

Chemokine expression during development of fibrosis versus resolution in a murine model of granulomatous experimental autoimmune thyroiditis

Severe granulomatous experimental autoimmune thyroiditis (G-EAT) in DBA/1 or CBA/J wild type (WT) mice at day 19 progresses to fibrosis by day 35, but severe G-EAT in DBA/1 interferon (IFN)-gamma-/- mice or less-severe G-EAT at day 19 in WT mice resolves by day 35. To study the role of chemokines in autoimmune diseases and fibrosis, profiles of chemokines and chemokine receptors were analyzed in DBA/1 WT versus IFN-gamma-/- and CBA/J thyroids, which have distinct outcomes of autoimmune inflammation. Gene expression of CXC chemokine ligand 1 (CXCL1) and CXC chemokine receptor 2 (CXCR2) paralleled neutrophil infiltration and thyrocyte destruction in DBA/1 WT or CBA/J thyroids, and gene expression of CC chemokine ligand 11 (CCL11), CCL8, and CC chemokine receptor 3 paralleled eosinophil infiltration in IFN-gamma-/- thyroids. Gene and protein expression of CXCL10, CXCL9, and CXCR3 was significantly lower in IFN-gamma-/- compared with DBA/1 WT thyroids. Moreover, immunostaining showed that CXCL10 was expressed by thyrocytes and inflammatory cells, and strong expression of CXCL10 by thyrocytes was as early as day 7. High expression of CCL2 was only observed in severely destroyed DBA/1 WT or CBA/J thyroids, which would develop fibrosis. Thus, the differential expression of chemokines may direct distinct cellular populations in DBA/1 WT versus IFN-gamma-/- thyroids. Up-regulation of CXCL10 by thyrocytes suggests its role in regulating the recruitment of specific subsets of activated lymphocytes to the thyroid during autoimmune inflammation. The early expression of CXCL1, CXCL10, and CCL2 may suggest their involvement in the initiation and perpetuation of disease in severe G-EAT thyroids, which progress to fibrosis.