Primary Sjögren's syndrome (pSS) is an autoimmune condition that causes harm to exocrine glands and also has extra-glandular manifestations (EGM). pSS patients with EGM have a worse prognosis than those with only sicca symptoms. Previous studies have shown that the minor salivary glands (MSG) of pSS patients exhibit a unique profile of cytokines and chemokines compared to healthy controls. However, there is a lack of research comparing pSS with EGM (pSS-EGM) and pSS without EGM (pSS-non-EGM). This study aims to explore potential biomarkers associated with pSS, particularly pSS with EGM. By utilizing RNA sequencing, we conducted an analysis on the gene expression profiles of MSG in 63 patients diagnosed with pSS, as well as 12 non-pSS individuals. Furthermore, we also investigated the MSG of pSS patients, both with and without EGM. Through bioinformatics analysis, we identified genes with differential expression (DEGs) and determined the core hub genes using PPI network. We then analyzed the top 20 DEGs and their correlation with the patients' clinical characteristics, and validated our findings using peripheral blood plasma. A total of 725 differentially expressed genes (DEGs) were identified in the comparison between pSS and non-pSS groups, and 727 DEGs were observed between pSS-EGM and pSS-non-EGM. It is noteworthy that the expression levels of CXCL9 were higher in both pSS patients and pSS-EGM when compared to the control group. Taking into consideration the significance of the top 20 DEGs in relation to clinical parameters and the central hub genes, we ultimately chose CXCL9. In comparison to the non-pSS group, pSS patients exhibited notably greater expression of the CXCL9 gene in the MSG, as well as higher levels of CXCL9 protein in their plasma (p < 0.001). Furthermore, the expression of the CXCL9 gene and levels of CXCL9 protein were notably higher in pSS patients accompanied by EGM and those with SSA antibodies. Additionally, a correlation was found between the expression of the CXCL9 gene and the EULAR Sjogren’s Syndrome Disease Activity Index (ESSDAI), as well as with immunoglobulin G (IgG) levels and erythrocyte sedimentation rate (ESR). Meanwhile, the protein levels of CXCL9 were found to be correlated with IgG levels and ESSDAI. CXCL9 proves to be a valuable biomarker in pSS, specifically due to its strong ability to differentiate between pSS patients with EGM and those without EGM. There is a significant correlation between CXCL9 and various clinical parameters both at the gene and protein level. Therefore, CXCL9 could be a potential target for future treatment of pSS.

中文翻译：

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CXCL9可能作为具有腺外表现的原发性干燥综合征的潜在生物标志物

原发性干燥综合征 (pSS) 是一种自身免疫性疾病，会对外分泌腺造成损害，并且还具有腺外表现 (EGM)。伴有 EGM 的 pSS 患者比仅有干燥症状的患者预后更差。先前的研究表明，与健康对照相比，pSS 患者的小唾液腺 (MSG) 表现出独特的细胞因子和趋化因子特征。然而，缺乏对带 EGM 的 pSS (pSS-EGM) 和不带 EGM 的 pSS (pSS-non-EGM) 进行比较的研究。本研究旨在探索与 pSS 相关的潜在生物标志物，特别是带有 EGM 的 pSS。通过利用 RNA 测序，我们对 63 名诊断为 pSS 的患者以及 12 名非 pSS 个体的 MSG 基因表达谱进行了分析。此外，我们还研究了 pSS 患者的 MSG，无论是否有 EGM。通过生物信息学分析，我们鉴定了具有差异表达（DEG）的基因，并利用PPI网络确定了核心枢纽基因。然后，我们分析了前 20 个 DEG 及其与患者临床特征的相关性，并使用外周血浆验证了我们的研究结果。在pSS和non-pSS组之间的比较中总共鉴定出725个差异表达基因（DEG），并且在pSS-EGM和pSS-non-EGM之间观察到727个DEG。值得注意的是，与对照组相比，pSS 患者和 pSS-EGM 中 CXCL9 的表达水平较高。考虑到前20个DEG与临床参数和中心枢纽基因的重要性，我们最终选择了CXCL9。与非 pSS 组相比，pSS 患者在 MSG 中表现出明显更高的 CXCL9 基因表达，并且血浆中的 CXCL9 蛋白水平更高 (p < 0.001)。此外，伴有EGM和具有SSA抗体的pSS患者中CXCL9基因的表达和CXCL9蛋白的水平显着较高。此外，还发现 CXCL9 基因的表达与 EULAR 干燥综合征疾病活动指数 (ESSDAI) 以及免疫球蛋白 G (IgG) 水平和红细胞沉降率 (ESR) 之间存在相关性。同时，发现CXCL9的蛋白水平与IgG水平和ESSDAI相关。CXCL9 被证明是 pSS 中有价值的生物标志物，特别是因为它具有很强的区分有 EGM 和没有 EGM 的 pSS 患者的能力。CXCL9与各种临床参数在基因和蛋白质水平上均存在显着相关性。因此，CXCL9可能成为未来治疗pSS的潜在靶点。