Alterations of Gene Expression and Signaling Pathway Activity in Venous Smooth Muscle Cells After Uremic Serum Exposure

Uremia is the most common pathophysiological symptom in chronic kidney disease (CKD) patients, particularly in end-stage kidney disease (ESKD) patients. Uremia can lead to several vein-specific vascular diseases, such as renal vein thrombosis (RVT), deep vein thrombosis (DVT) and dialysis access-induced venous stenosis. One of our previous studies demonstrated that uremic serum exposure induced different cellular responses in pig venous smooth muscle cells (vSMCs) compared with arterial smooth muscle cells (aSMCs). To explore the underlying mechanisms responsible for vein-specific cellular responses, bulk RNA sequencing was utilized to examine differential gene expression in porcine vSMCs after uremic serum exposure. Differentially expressed genes (DEG) analysis revealed that 408 genes were upregulated, and 387 genes were downregulated after uremic serum treatment. Gene Ontology Biological Process analysis demonstrated that uremic serum exposure led to transcriptomic downregulation of cellular energy expenditure activities, such as the Cell Cycle, and positive transcriptomic enrichment of Cellular Response to Endoplasmic Reticulum (ER) stress, unfolded protein response and hypoxia. Both Gene Set Enrichment Analysis (GSEA) and Overrepresentation Analysis (ORA) obtained similar results. ORA revealed additional signaling pathways predicted to be transcriptomically downregulated, such as the Hippo signaling pathway and Focal Adhesion and Cytoskeletal Structure Regulating pathways. ORA also predicted several positively enriched signaling pathways related to cellular stress responses and waste disposal. To precisely identify vSMC-specific alterations, an interaction-based KEGG GSEA was performed. The analysis revealed several significantly different responses between vSMCs and aSMCs, such as Protein Processing in the Endoplasmic Reticulum, Integrated Stress Response signaling pathway and Mitophagy, which showed more positive responses in vSMCs, while oxidative phosphorylation showed a more positive response in aSMCs. These altered signaling pathways may be responsible for vein-specific clinical symptoms, such as venous segment stenosis in arteriovenous fistula, observed in CKD/ESKD patients.