Sjögren's and non-Sjögren's sicca share a similar symptom burden but with a distinct symptom-associated proteomic signature

Deleting Mitochondrial Superoxide Dismutase 2 in Salivary Gland Ductal Epithelial Cells Recapitulates Non-Sjögren's Sicca Syndrome

Elevated oxidative stress can play a pivotal role in autoimmune diseases by exacerbating inflammatory responses and tissue damage. In Sjögren's disease (SjD), the contribution of oxidative stress in the disease pathogenesis remains unclear. To address this question, we created mice with a tamoxifen-inducible conditional knockout (KO) of a critical antioxidant enzyme, superoxide dismutase 2 (Sod2), in the salivary glands (i-sg-Sod2 KO mice). Following tamoxifen treatment, Sod2 deletion occurred primarily in the ductal epithelium, and the salivary glands showed a significant downregulation of Sod2 expression. At twelve weeks post-treatment, salivary glands from the i-sg-Sod2 KO mice exhibited increased 3-Nitrotyrosine staining. Bulk RNA-seq revealed alterations in gene expression pathways related to ribosome biogenesis, mitochondrial function, and oxidative phosphorylation. Significant changes were noted in genes characteristic of salivary gland ionocytes. The i-sg-Sod2 KO mice developed reversible glandular hypofunction. However, this functional loss was not accompanied by glandular lymphocytic foci or circulating anti-nuclear antibodies. These data demonstrate that although localized oxidative stress in salivary gland ductal cells was insufficient for SjD development, it induced glandular dysfunction. The i-sg-Sod2 KO mouse resembles patients classified as non-Sjögren's sicca and will be a valuable model for deciphering oxidative-stress-mediated glandular dysfunction and recovery mechanisms.

OHIP-14 Scores in Patients with Sjögren's Syndrome Compared to Sicca Syndrome: A Systematic Review with Meta-Analysis

Objectives

Primary Sjögren's syndrome (pSS) is a chronic autoimmune disorder characterized by dryness of mucous membranes, predominantly the eyes and mouth, following glandular tissue substitution. The onset of oral dryness constitutes a significant source of discomfort that negatively affects overall quality of life. This systematic review aimed at investigating the differences in Oral Health Impact Profile-14 (OHIP-14) questionnaire scores in patients diagnosed with Sjögren's syndrome compared to sicca syndrome, to assess the influence of the two conditions on oral health. Study Design. A systematic electronic and manual search was performed up to December 2023 for studies reporting OHIP-14 questionnaire scores in pSS patients versus sicca syndrome. Two authors independently reviewed, selected, and extracted the data. The outcome was the assessment of OHIP-14 scores in studies comparing pSS- and sicca syndrome-affected patients. Meta-analysis was conducted on available quantitative data.

Results

Literature search retrieved 30 articles, and 3 articles met the criteria for inclusion in the review. Meta-analysis revealed significantly higher scores in patients with sicca syndrome compared to pSS, although salivary flow was markedly reduced in pSS.

Conclusions

While offering supplementary information to standard tests and supporting the assessment of pSS and sicca syndrome patients, further validation is necessary to establish OHIP-14 validity in determining the impact of pSS and sicca syndrome on patients' quality of life.

Deciphering the role of cDC2s in Sjögren's syndrome: transcriptomic profile links altered antigen processes with IFN signature and autoimmunity

OBJECTIVE

Type 2 conventional dendritic cells (cDC2s) are key orchestrators of inflammatory responses, linking innate and adaptative immunity. Here we explored the regulation of immunological pathways in cDC2s from patients with primary Sjögren's syndrome (pSS).

METHODS

RNA sequencing of circulating cDC2s from patients with pSS, patients with non-Sjögren's sicca and healthy controls (HCs) was exploited to establish transcriptional signatures. Phenotypical and functional validation was performed in independent cohorts.

RESULTS

Transcriptome of cDC2s from patients with pSS revealed alterations in type I interferon (IFN), toll-like receptor (TLR), antigen processing and presentation pathways. Phenotypical validation showed increased CX3CR1 expression and decreased integrin beta-2 and plexin-B2 on pSS cDC2s. Functional validation confirmed impaired capacity of pSS cDC2s to degrade antigens and increased antigen uptake, including self-antigens derived from salivary gland epithelial cells. These changes in antigen uptake and degradation were linked to anti-SSA/Ro (SSA) autoantibodies and the presence of type I IFNs. In line with this, in vitro IFN-α priming enhanced the uptake of antigens by HC cDC2s, reflecting the pSS cDC2 profile. Finally, pSS cDC2s compared with HC cDC2s increased the proliferation and the expression of CXCR3 and CXCR5 on proliferating CD4⁺ T cells.

CONCLUSIONS

pSS cDC2s are transcriptionally altered, and the aberrant antigen uptake and processing, including (auto-)antigens, together with increased proliferation of tissue-homing CD4⁺ T cells, suggest altered antigen presentation by pSS cDC2s. These functional alterations were strongly linked to anti-SSA positivity and the presence of type I IFNs. Thus, we demonstrate novel molecular and functional pieces of evidence for the role of cDC2s in orchestrating immune response in pSS, which may yield novel avenues for treatment.