Ruxolitinib improves outcomes in association with altered fibroblast immunobiology in mouse models of Sjögren’s disease

OBJECTIVE: Sjögren Disease (SjD) is a common rheumatologic disease with symptoms of dryness attributed to autoimmune exocrinopathy. JAK-STAT signaling pathway activity contributes to SjD salivary gland pathogenesis. We hypothesized that treatment of SjD model mice with ruxolitinib, a JAK-inhibitor, would improve disease course. METHODS: NOD.B10 and Aec SjD model mice were treated with vehicle or ruxolitinib for two weeks. We measured plasma immunoglobulins and cytokines, and assessed submandibular salivary glands (SMSGs) histologically, with flow cytometry, and spatial transcriptomics. RESULTS: Aec mice had a more robust inflammatory profile than NOD.B10 mice as measured by SMSG lymphocytic infiltrate, peripheral immunoglobulins and cytokine concentrations. Ruxolitinib treatment reduced plasma [IgG], [CXCL13], and focus score in Aec but not NOD.B10 mice. In Aec mice, flow cytometry showed reductions in phosphorylated (p) STAT1 in SMSG epithelial cells, leukocytes, and fibroblasts with treatment. pSTAT1 correlated with salivary flow rate and focus score. Spatial transcriptomic sequencing and immunofluorescence of SMSGs revealed a treatment effect upon fibroblast-macrophage spatial relationships. CONCLUSION: Ruxolitinib treatment improved disease course in Aec mice but not NOD.B10 mice, suggesting these mice model different SjD subpopulations and ruxolitinib efficacy may be subpopulation dependent. Flow cytometry, spatial transcriptomics, and immunostaining results implicated ruxolitinib-induced changes of fibroblast-immune cell interactions in the SMSG thereby suggesting these unique interactions as a pathogenic element and novel treatment target. These results underscore the therapeutic potential of JAK-STAT pathway inhibition for treatment of SjD, and with ruxolitinib specifically, at least for specific SjD subpopulations.