Immunofibroblasts are pivotal drivers of tertiary lymphoid structure formation and local pathology.

Resident fibroblasts at sites of infection, chronic inflammation, or cancer undergo phenotypic and functional changes to support leukocyte migration and, in some cases, aggregation into tertiary lymphoid structures (TLS). The molecular programming that shapes these changes and the functional requirements of this population in TLS development are unclear. Here, we demonstrate that external triggers at mucosal sites are able to induce the progressive differentiation of a population of podoplanin (pdpn)-positive stromal cells into a network of immunofibroblasts that are able to support the earliest phases of TLS establishment. This program of events, that precedes lymphocyte infiltration in the tissue, is mediated by paracrine and autocrine signals mainly regulated by IL13. This initial fibroblast network is expanded and stabilized, once lymphocytes are recruited, by the local production of the cytokines IL22 and lymphotoxin. Interfering with this regulated program of events or depleting the immunofibroblasts in vivo results in abrogation of local pathology, demonstrating the functional role of immunofibroblasts in supporting TLS maintenance in the tissue and suggesting novel therapeutic targets in TLS-associated diseases.

CXCL13 as biomarker for histological involvement in Sjögren's syndrome.

OBJECTIVES: SS is an autoimmune condition characterized by systemic B-cell activation, autoantibody production and ectopic germinal centres' formation within the salivary gland (SG). The extent of SG infiltrate has been proposed as a biomarker of disease severity. Plasma levels of CXCL13 correlate with germinal centres' activity in animal models and disease severity in SS, suggesting its potential use as a surrogate serum marker to monitor local B-cell activation. The aim of this study was to evaluate the potential role of CXCL13 as a biomarker of SG pathology in two independent SS cohorts. METHODS: 109 patients with SS were recruited at Sapienza University of Rome (Italy) (n = 60), or at Queen Elizabeth Hospital in Birmingham and Barts Health NHS Trust in London (n = 49). Both sera and matched minor SG biopsy were available. Sicca (n = 57) and healthy subjects' (n = 19) sera were used as control. RESULTS: CXCL13 serum level was higher in SS patients compared with controls. Correlations between its serum levels and a series of histomorphological parameters, including size of the aggregates and the presence germinal centres', were observed. CONCLUSION: Our data foster the use of CXCL13 to monitor the extent of local pathology in SS and its validation in longitudinal clinical studies.

Phosphatidylinositol 3-kinase delta pathway: a novel therapeutic target for Sjögren's syndrome.

BACKGROUND: The phosphatidylinositol 3-kinase delta isoform (PI3Kδ) belongs to an intracellular lipid kinase family that regulate lymphocyte metabolism, survival, proliferation, apoptosis and migration and has been successfully targeted in B-cell malignancies. Primary Sjögren's syndrome (pSS) is a chronic immune-mediated inflammatory disease characterised by exocrine gland lymphocytic infiltration and B-cell hyperactivation which results in systemic manifestations, autoantibody production and loss of glandular function. Given the central role of B cells in pSS pathogenesis, we investigated PI3Kδ pathway activation in pSS and the functional consequences of blocking PI3Kδ in a murine model of focal sialoadenitis that mimics some features of pSS. METHODS AND RESULTS: Target validation assays showed significant expression of phosphorylated ribosomal protein S6 (pS6), a downstream mediator of the phosphatidylinositol 3-kinase delta (PI3Kδ) pathway, within pSS salivary glands. pS6 distribution was found to co-localise with T/B cell markers within pSS aggregates and the CD138+ plasma cells infiltrating the glands. In vivo blockade of PI3Kδ activity with seletalisib, a PI3Kδ-selective inhibitor, in a murine model of focal sialoadenitis decreased accumulation of lymphocytes and plasma cells within the glands of treated mice in the prophylactic and therapeutic regimes. Additionally, production of lymphoid chemokines and cytokines associated with ectopic lymphoneogenesis and, remarkably, saliva flow and autoantibody production, were significantly affected by treatment with seletalisib. CONCLUSION: These data demonstrate activation of PI3Kδ pathway within the glands of patients with pSS and its contribution to disease pathogenesis in a model of disease, supporting the exploration of the therapeutic potential of PI3Kδ pathway inhibition in this condition.

Immunofibroblasts regulate LTα3 expression in tertiary lymphoid structures in a pathway dependent on ICOS/ICOSL interaction.

Immunofibroblasts have been described within tertiary lymphoid structures (TLS) that regulate lymphocyte aggregation at sites of chronic inflammation. Here we report, for the first time, an immunoregulatory property of this population, dependent on inducible T-cell co-stimulator ligand and its ligand (ICOS/ICOS-L). During inflammation, immunofibroblasts, alongside other antigen presenting cells, like dendritic cells (DCs), upregulate ICOSL, binding incoming ICOS + T cells and inducing LTα3 production that, in turn, drives the chemokine production required for TLS assembly via TNFRI/II engagement. Pharmacological or genetic blocking of ICOS/ICOS-L interaction results in defective LTα expression, abrogating both lymphoid chemokine production and TLS formation. These data provide evidence of a previously unknown function for ICOSL-ICOS interaction, unveil a novel immunomodulatory function for immunofibroblasts, and reveal a key regulatory function of LTα3, both as biomarker of TLS establishment and as first driver of TLS formation and maintenance in mice and humans.

Cenerimod, a selective S1P1 receptor modulator, improves organ-specific disease outcomes in animal models of Sjögren's syndrome.

BACKGROUND: Sjögren's syndrome is a systemic autoimmune disease characterized by immune cells predominantly infiltrating the exocrine glands and frequently forming ectopic lymphoid structures. These structures drive a local functional immune response culminating in autoantibody production and tissue damage, associated with severe dryness of mucosal surfaces and salivary gland hypofunction. Cenerimod, a potent, selective and orally active sphingosine-1-phosphate receptor 1 modulator, inhibits the egress of lymphocytes into the circulation. Based on the mechanism of action of cenerimod, its efficacy was evaluated in two mouse models of Sjögren's syndrome. METHODS: Cenerimod was administered in two established models of Sjögren's syndrome; firstly, in an inducible acute viral sialadenitis model in C57BL/6 mice, and, secondly, in the spontaneous chronic sialadenitis MRL/lpr mouse model. The effects of cenerimod treatment were then evaluated by flow cytometry, immunohistochemistry, histopathology and immunoassays. Comparisons between groups were made using a Mann-Whitney test. RESULTS: In the viral sialadenitis model, cenerimod treatment reduced salivary gland immune infiltrates, leading to the disaggregation of ectopic lymphoid structures, reduced salivary gland inflammation and preserved organ function. In the MRL/lpr mouse model, cenerimod treatment decreased salivary gland inflammation and reduced T cells and proliferating plasma cells within salivary gland ectopic lymphoid structures, resulting in diminished disease-relevant autoantibodies within the salivary glands. CONCLUSIONS: Taken together, these results suggest that cenerimod can reduce the overall autoimmune response and improve clinical parameters in the salivary glands in models of Sjögren's syndrome and consequently may reduce histological and clinical parameters associated with the disease in patients.

Autophagy occurs in lymphocytes infiltrating Sjögren's syndrome minor salivary glands and correlates with histological severity of salivary gland lesions.

BACKGROUNDS: The organization of minor salivary glands (MSG) infiltrates, in patients with Sjögren's syndrome (SS), associates with disease severity and progression. Aberrant regulation of lymphocyte autophagy is involved in autoimmunity, and in previous work, we provided the first evidence of upregulated autophagy in CD4+ T cells infiltrating SS MSG. The aim of this study was to further explore autophagy in SS infiltrating and circulating lymphocytes and to investigate its role in disease histopathological progression. METHODS: After collection of 20 SS MSG, the presence of lymphocyte aggregates (foci) and the formation of germinal center (GC)-like structures were observed by H&E and confirmed by immunohistochemistry. The expression of autophagy-related genes, Atg5 and MAP1LC3A, was detected by RT-PCR on microdissected salivary gland tissue and control tonsils. In MSG and tonsils, autophagic lymphocytes were identified by the detection of the autophagosome protein LC3B visualized as LC3 puncta staining by immunofluorescence. Peripheral blood autophagy was assessed by flow cytometry in SS and healthy controls (HC). RESULTS: Real-time PCR demonstrated higher expression in the autophagy genes Atg5 and MAP1LC3A in MSG GCs as compared to both small foci (p = 0.0075, p = 0.0002) and GCs from tonsils (p = 0.0001, p = 0.0037). In MSG, LC3 puncta staining was detectable on both CD3+ and CD20+ lymphocytes; in tonsils, LC3 puncta was almost undetectable on all lymphocytes. Compared to HC (n = 20), flow cytometry did not reveal any increase of autophagy in SS circulating lymphocytes (n = 30). CONCLUSIONS: In SS MSG, lymphocytes' autophagy is a feature of infiltrating T and B cells and is associated with histological severity. Interestingly, in MSG aberrant regulation of autophagy is detectable in GC-like structures possibly indicating its involvement in the development and persistence of the autoimmune process within the lesions.

Leflunomide-hydroxychloroquine combination therapy in patients with primary Sjögren's syndrome (RepurpSS-I): a placebo-controlled, double-blinded, randomised clinical trial.

BACKGROUND: Primary Sjögren's syndrome is a systemic autoimmune disease characterised by secretory gland dysfunction, for which no effective therapy is available. Based on the complementary properties of leflunomide and hydroxychloroquine in inhibiting activation of key immune cells in primary Sjögren's syndrome, we aimed to evaluate the clinical efficacy and safety of leflunomide-hydroxychloroquine combination therapy in patients with primary Sjögren's syndrome. METHODS: We did a placebo-controlled, double-blinded, phase 2A randomised clinical trial in patients with primary Sjögren's syndrome at the University Medical Center Utrecht (Utrecht, Netherlands). Eligible patients were aged 18-75 years, had a European League Against Rheumatism (EULAR) Sjögren's syndrome disease activity index (ESSDAI) score of 5 or higher, and a lymphocytic focus score of 1 or higher in labial salivary gland biopsy specimens. Patients were randomly assigned (2:1) with block randomisation (block size of six) to receive leflunomide 20 mg and hydroxychloroquine 400 mg daily or placebo for 24 weeks. The primary endpoint was the between-group difference in change in ESSDAI scores from 0 to 24 weeks, adjusted for baseline ESSDAI score. Patients were analysed according to the intention-to-treat principle. This study is registered with EudraCT, 2014-003140-12. FINDINGS: Between March 7, 2016, and Nov 30, 2017, 37 patients were screened, of whom 29 patients (28 women and one man) were enrolled. 21 patients were assigned to receive leflunomide-hydroxychloroquine and eight patients were assigned to receive placebo. One patient in the placebo group required high-dose prednisone to treat polymyalgia rheumatica at week 13 and was excluded from the primary analysis. From 0 to 24 weeks, the mean difference in ESSDAI score, adjusted for baseline values, in the leflunomide-hydroxychloroquine group compared with the placebo group was -4·35 points (95% CI -7·45 to -1·25, p=0·0078). No serious adverse events occurred in the leflunomide-hydroxychloroquine group and two serious adverse events occurred in the placebo group (hospital admission for pancreatitis and hospital admission for nephrolithiasis). The most common adverse events in the leflunomide-hydroxychloroquine group were gastrointestinal discomfort (11 patients [52%] vs two [25%] in the placebo group), modest transient increases in alanine aminotransferase (ten [48%] vs one [13%]), and short episodes of general malaise and shivering (nine [43%] vs one [13%]). INTERPRETATION: Leflunomide-hydroxychloroquine was safe and resulted in a clinical response in patients with primary Sjögren's syndrome. These results warrant further evaluation of leflunomide-hydroxychloroquine combination therapy in larger clinical trials. FUNDING: ZonMw.

Kinase-independent inhibition of cyclophosphamide-induced pathways protects the ovarian reserve and prolongs fertility.

Premature ovarian failure and infertility are adverse effects of cancer therapies. The mechanism underlying chemotherapy-mediated depletion of the ovarian reserve remains unclear. Here, we aim to identify the signaling pathways involved in the loss of the ovarian reserve to prevent the damaging effects of chemotherapy. We evaluated the effects of cyclophosphamide, one of the most damaging chemotherapeutic drugs, against follicle reserve. In vivo studies showed that the cyclophosphamide-induced loss of ovarian reserve occurred through a sequential mechanism. Cyclophosphamide exposure induced the activation of both DNAPK-γH2AX-checkpoint kinase 2 (CHK2)-p53/TAp63α isoform and protein kinase B (AKT)-forkhead box O3 (FOXO3a) signaling axes in the nucleus of oocytes. Concomitant administration of an allosteric ABL inhibitor and cyclophosphamide modulated both pathways while protecting the ovarian reserve from chemotherapy assaults. As a consequence, the fertility of the treated mice was prolonged. On the contrary, the administration of an allosteric ABL activator enhanced the lethal effects of cyclophosphamide while shortening mouse fertility. Therefore, kinase-independent inhibition may serve as an effective ovarian-protective strategy in women under chemotherapy.

P63 in health and cancer.

TP63 is the most ancient member of the p53 gene family. The p53 family comprises three transcription factors (p53/p63/p73). They share a high degree of homology and similar domain structure. Yet, they can exist as truncated isoforms. Alternative promoters and splicing sites lead to the generation of several molecules. P53/p63/p73 are important to maintain cell homeostasis. P63 and p73 regulate many p53 target genes. This is due to their common structural features. Both proteins may compensate the loss of p53. This is a common event occurring in more than 50% of malignancies. Yet, p63 (or p73) has its own role. Studies from p63-null mice have shown the key role of p63 in embryo development. Several reports have supported the p63 role in epidermal development and in skin homeostasis. P63 involvement in heart development is currently being researched. Recent studies have found p63 to be "the guardian of human reproduction". In addition, p63 has an important, even controversial, role in cancer. Here, we provide a general overview of p63 regulation and activity. We discuss emerging concepts about its role in germ line protection, metabolism and cancer.

P53 and Sirt1: routes of metabolism and genome stability.

The tumor suppressor p53 is a transcription factor that regulates key processes. But, the outcomes of the p53 response go beyond its role as a nuclear transcription factor. Sirtuin (SIRT1) regulates p53 functions as transcription factor. At the same time, SIRT1 protects the genome under stress conditions. The link between p53 and SIRT1 responses is unique. Both regulate metabolism, stress signaling, cell survival, cell cycle control and genome stability. Recent studies have proposed cancer as a metabolic disease. This is due to the switch from aerobic to anaerobic metabolism during tumor development. Yet, the complex molecular circuits (in and out of the nucleus) of tumor progression remain elusive. In this review, we will focus on the interplay between p53 and SIRT1. We will discuss their roles as nodes for possible therapeutic intervention.