Background/Purpose: Primary Sjögren’s syndrome (pSS) is a chronic rheumatic disease characterized by lymphocytic infiltration of exocrine glands, resulting in sicca syndrome with extra-glandular autoimmune features. The etiopathogeny is unknown, involving environmental and hormonal factors on a predisposing genetic background. For fundamental research, several inbred mice strains predisposed to SS exist but backcrossing them with transgenic mice from another genetic background is tedious and time consuming. The aim of this work is to describe an inducible model of pSS that is easy to implement and compatible with CreLox transgenic mice on a C57Bl/6 background, using NFAT5 conditional knockout (KO) mice as a proof of concept.

Methods: Female C57Bl/6 UbC-Cre-NFAT5flx/flx or UbC-Cre+NFAT5flx/flx mice were injected subcutaneously at weeks 12 and 15 with either 25mg/kg 5,6-dimethylxanthenone-4-acetic acid (DMXAA) or vehicule, then at week 17 with two consecutive intraperitoneal injections (at 24h interval) of either 100µl of corn oil or 20mg/ml tamoxifen (TAM). Saliva and lacrymal flow were measured under pilocarpine stimulation at week 18. Mice were sacrified at week 19. Orbit content, submandibular and lacrymal glands were evaluated by histology. Anti-Ro/SSA, anti-Ro/SSB and rheumatoid factor (RF) antibodies were detected by ELISA. FACS analysis of lymphocytic populations was performed on submandibular glands. RNA-sequencing was performed to generate a comprehensive global gene expression profile of submandibular glands from DMXAA-treated groups compared to controls.

Results: Compared to controls, DMXAA/oil- and DMXAA/TAM-treated Cre- mice display a significant decrease in salivary flow (p=0.0009) and Schirmer’s test (p=0.03). Histologically, treated groups show low-grade focal sialadenitis within the submandibular glands, increased corneal epithelium thickness but no reproducible dacryoadenitis within the external lacrimal glands. FACS analysis on submandibular glands confirms the presence of predominantly CD8+ and CD4+ T-cells infiltrate. Treated groups also show higher serum reactivity for Ro/SSA (p=0.011), anti-Ro/SSA and RF positivity (both 0% vs 12.5% vs 31.2%, p=0.0232). Only 1 out of 21 mice in the DMXAA/TAM-treated Cre- group showed double anti-Ro/SSA and anti-La/SSB positivity. Comparative analysis of the transcriptomes revealed distinct gene expression patterns in DMXAA-treated groups compared to control mice. Notably, there was in both DMXAA-treated group a significant enrichment of interferon (IFN)-related genes. Compared to DMXAA/TAM-treated Cre- mice, induction of NFAT5 KO in DMXAA/TAM-treated Cre+ mice results in reduced focus-score (p=0.0238), anti-Ro/SSA reactivity (p=0.0127), but does not restore salivary (p=0.77) or lacrimal flow (p=0.9355).

Conclusion: DMXAA-based inducible mouse model of pSS – demonstrating key phenotypic features of human pSS – is an attractive alternative to spontaneous inbred models, allowing the use of any C57Bl/6 mice in pSS experiments.In this study, induction of NFAT5 KO at week 17 reduced focal sialadenitis and anti-Ro/SSA levels but did not rescue salivary and lacrimal flow at week 19.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/new-inducible-mouse-model-of-sjogrens-syndrome-represents-a-valuable-tool-to-assess-the-impact-of-gene-knockout-on-the-diseases-physiopathology/