[Identification of endothelial cell key genes associated with pathogenesis and invasion of human venous malformations using single-nucleus RNA sequencing-based co-expression network analysis].

<b>Objective:</b> This study aimed to identify key genes in endothelial cell (EC) associated with the pathogenesis and progression of human venous malformations (VMs) through bioinformatics analysis, providing potential biomarkers for early screening and targeted therapy of VMs. <b>Methods:</b> A case-control study was conducted using surgically resected tissue specimens from VMs patients at the Third Affiliated Hospital of Zhengzhou University (from September 2021 to September 2023), with malformed venous tissues as the experimental group and distal normal venous tissues as controls. Single-nucleus RNA sequencing (snRNA-seq) was performed on paired experimental and control samples from four VM patients. High-dimensional weighted gene co-expression network analysis (hdWGCNA), combined with gene ontology (GO), Kyoto encyclopedia of genes and genomes (KEGG), and protein-protein interaction (PPI) network analysis, identified critical genes. Validation experiments included 15 additional VM cases and controls using reverse transcription quantitative polymerase chain reaction (RT-qPCR), immunohistochemistry (IHC), and Western blot. <b>Results:</b> A total of 55 430 nuclei were captured using snRNA-seq, with 30 391 nuclei from the experimental group and 25 039 nuclei from the control group. Cluster analysis identified 22 distinct cell populations, which were annotated into 8 cell types. hdWGCNA revealed four modules associated with invasion, which were enriched in angiogenesis, integrin signaling, and cell adhesion according to GO analysis. KEGG pathway analysis indicated that the PI3K-AKT signaling pathway and focal adhesion are key regulatory mechanisms. PPI network analysis combined with cytoscape identified <i>EGFL7</i>, <i>TEK</i>, and <i>FLT1</i> as key genes. RT-qPCR results demonstrated that the relative mRNA expression levels of these three genes in the experimental group (6.66±2.31, 1.86±0.62, 3.49±0.58) were significantly higher than those in the control group (1.05±0.14, 1.00±0.14, 1.06±0.25), with statistically significant differences (<i>t</i>=9.37, 4.27, 11.20, <i>P</i><0.05). Immunohistochemical analysis showed that the relative protein expression levels of these three genes in the cytoplasm of the experimental group (0.84±0.15, 0.68±0.14, 0.85±0.12) were also significantly higher than those in the control group (0.19±0.05, 0.23±0.06, 0.30±0.05), with statistically significant differences (<i>t</i>=16.62, 5.93, 11.68, <i>P</i><0.05). Western blot analysis confirmed that the relative protein expression levels of these three genes in the experimental group (0.35±0.04, 0.36±0.09, 0.31±0.04) were significantly higher than those in the control group (0.19±0.01, 0.13±0.02, 0.14±0.04), with statistically significant differences (<i>t</i>=7.05, 4.61, 5.93, <i>P</i><0.05). <b>Conclusion:</b> <i>EGFL7, FLT1,</i> and <i>TEK</i> in EC may play crucial roles in the occurrence and invasion of VMs.