We attempted to identify abnormal immune cell components and signaling pathways in lupus nephritis (LN) and to identify potential therapeutic targets. Differentially expressed genes (DEGs) between LN and normal kidney tissues were identified from bulk transcriptome data, and functional annotation was performed. The phenotypic changes in macrophages and aberrant intercellular signaling communications within immune cells were imputed from LN scRNA-seq data using trajectory analysis and verified using immunofluorescence staining. Finally, lentivirus-mediated overexpression of LGALS9, the gene encoding Galectin 9, in THP-1 cells was used to study the functional effect of this gene on monocytic cells. From bulk transcriptome data, a significant activation of interferon (IFN) signaling was observed, and its intensity showed a significantly positive correlation with the abundance of infiltrating macrophages in LN. Analysis of scRNA-seq data revealed 17 immune cell clusters, with macrophages showing the highest enrichment of intercellular signal communication in LN. Trajectory analysis revealed macrophages in LN undergo a phenotypic change from inflammatory patrolling macrophages to phagocytic and then to antigen-presenting macrophages, and secrete various pro-inflammatory factors and complement components. LGALS9 was found significantly upregulated in macrophages in LN, which was confirmed by the immunofluorescence assay. Gene functional study showed that LGALS9 overexpression in THP-1 cells significantly elicited pro-inflammatory activation, releasing multiple immune cell chemoattractants. Our results present an important pathophysiological role for macrophages in LN, and our preliminary results demonstrate significant pro-inflammatory effects of LGALS9 gene in LN macrophages.

中文翻译：

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单细胞和大量转录组数据的综合分析揭示了巨噬细胞在狼疮性肾炎中的重要作用

我们试图识别狼疮性肾炎 (LN) 中的异常免疫细胞成分和信号通路，并确定潜在的治疗靶点。从大量转录组数据中鉴定出 LN 和正常肾组织之间的差异表达基因 (DEG)，并进行功能注释。使用轨迹分析从 LN scRNA-seq 数据估算巨噬细胞的表型变化和免疫细胞内异常的细胞间信号通讯，并使用免疫荧光染色进行验证。最后，利用慢病毒介导的THP-1细胞中LGALS9（编码半乳糖凝集素9的基因）的过度表达来研究该基因对单核细胞的功能影响。从大量转录组数据中，观察到干扰素（IFN）信号的显着激活，其强度与 LN 中浸润巨噬细胞的丰度呈显着正相关。 scRNA-seq 数据分析揭示了 17 个免疫细胞簇，其中巨噬细胞在 LN 中显示出细胞间信号通讯的最高富集度。轨迹分析显示，LN 中的巨噬细胞经历了从炎症巡逻巨噬细胞到吞噬细胞再到抗原呈递巨噬细胞的表型变化，并分泌各种促炎因子和补体成分。免疫荧光检测证实，LN 巨噬细胞中 LGALS9 显着上调。基因功能研究表明，THP-1细胞中LGALS9的过表达显着引发促炎激活，释放多种免疫细胞趋化剂。我们的结果表明巨噬细胞在 LN 中具有重要的病理生理学作用，我们的初步结果表明 LGALS9 基因在 LN 巨噬细胞中具有显着的促炎作用。