Department of Oral Surgery and Oral Medicine, Institute of Clinical Odontology, University of Oslo, Oslo, Norway.
Gade Laboratory for Pathology, Department of Clinical Medicine, University of Bergen, Bergen, Norway.
Autoimmunity. 2020 Sep;53(6):333-343. doi: 10.1080/08916934.2020.1795140. Epub 2020 Jul 20.
Salivary gland involvement is a characteristic feature of primary Sjögren's syndrome (pSS), where tissue destruction is mediated by infiltrating immune cells, and may be accompanied by the presence of adipose tissue. Optimally diagnosing this multifactorial disease requires the incorporation of additional routines. Screening for disease-specific biomarkers in biological fluid could be a promising approach to increase diagnostic accuracy. We have previously investigated disease biomarkers in saliva and tear fluid of pSS patients, identifying Neutrophil gelatinase-associated lipocalin (NGAL) as the most upregulated protein in pSS. In the current study, we aimed to explore for the first time NGAL expression at the site of inflammation in the pSS disease target organ. Immunohistochemical staining was conducted on minor salivary gland biopsies from 11 pSS patients and 11 non-SS sicca subjects, targeting NGAL-specific cells. Additional NGAL/PNAd double staining was performed to study NGAL expression in high endothelial venules, known as specialised vascular structures. Moreover, NGAL mRNA expression was measured utilising quantitative real-time polymerase chain reaction (qRT-PCR) on minor salivary gland biopsies from 15 pSS patients and 7 non-SS sicca individuals that served as tissue controls. Our results demonstrated NGAL expression in acinar and ductal epithelium within the salivary gland of pSS patients, where significantly greater levels of acinar NGAL were observed in pSS patients ( < .0018) when compared to non-SS subjects. Also, acinar expression positively correlated with focus score values ( = 0.54, < .02), while ductal epithelial expression showed a negative such correlation ( = 0.74, < .003). Some PNAD endothelial venules also expressed NGAL. An increase in NGAL staining with increased fatty replacement was also observed in pSS patients. Concurringly, a 27% increase in NGAL mRNA levels were also detected in the minor salivary glands of pSS patients when compared to non-SS tissue control subjects. In conclusion, there is a positive association between increase in NGAL expression and inflammation in the pSS disease target organ, which also coincides with its previously demonstrated upregulation in the saliva of pSS patients. Additional functional analyses are needed to better understand the immunological implications of this potential biomarker.
唾液腺受累是原发性干燥综合征(pSS)的特征性表现,其中组织破坏由浸润免疫细胞介导,并且可能伴有脂肪组织的存在。最佳诊断这种多因素疾病需要纳入额外的常规检查。在生物体液中筛查疾病特异性生物标志物可能是提高诊断准确性的一种有前途的方法。我们之前已经研究了 pSS 患者唾液和泪液中的疾病生物标志物,发现中性粒细胞明胶酶相关脂质运载蛋白(NGAL)是 pSS 中上调最明显的蛋白。在本研究中,我们旨在首次探索 NGAL 在 pSS 疾病靶器官炎症部位的表达。对 11 名 pSS 患者和 11 名非干燥综合征口干患者的小唾液腺活检组织进行了 NGAL 特异性细胞的免疫组织化学染色。进行了额外的 NGAL/PNAd 双重染色,以研究已知的高内皮静脉中的 NGAL 表达,高内皮静脉是专门的血管结构。此外,利用定量实时聚合酶链反应(qRT-PCR)测量了 15 名 pSS 患者和 7 名非干燥综合征口干患者小唾液腺活检组织中的 NGAL mRNA 表达,这些患者作为组织对照。我们的结果表明,在 pSS 患者的唾液腺中,NGAL 表达在腺泡和导管上皮细胞中,与非干燥综合征患者相比,pSS 患者的腺泡 NGAL 水平显著升高(<0.0018)。此外,腺泡表达与焦点评分值呈正相关(=0.54,<0.02),而导管上皮细胞表达呈负相关(=0.74,<0.003)。一些 PNAd 内皮静脉也表达了 NGAL。在 pSS 患者中,随着脂肪替代的增加,NGAL 染色也增加。同时,与非干燥综合征组织对照相比,pSS 患者的小唾液腺中 NGAL mRNA 水平也增加了 27%。总之,在 pSS 疾病靶器官中,NGAL 表达的增加与炎症之间存在正相关关系,这与之前在 pSS 患者唾液中观察到的上调相一致。需要进一步的功能分析来更好地了解这种潜在生物标志物的免疫学意义。