Uremic serum exposure leads to differential phenotypic switch in porcine arterial and venous smooth muscle cells

Many patients with end-stage kidney disease (ESKD) frequently suffer from both aggressive vascular access stenosis in the venous segment of arteriovenous fistula or arteriovenous graft, and widespread cardiovascular disease (CVD) or peripheral arterial disease (PAD). Despite the magnitude of these clinical problems, the pathogenic role of the uremic state in both of these conditions remains unclear. To investigate the underlying mechanisms, we used porcine-derived arterial smooth muscle cells (ApSMCs) and venous smooth muscle cells (VpSMCs) to examine several key aspects of cell behavior in response to uremic serum. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay demonstrated that 30% of uremic serum was able to stimulate the proliferation of both subtypes of cells equally. Cell migration, measured by the scratch assay, showed that uremic serum increased migration of both cells, but was more robust in VpSMCs. Importantly, uremic serum induced phenotypic switching (e.g., dedifferentiation) in both subtypes of cells, as indicated by increased proliferating cell nuclear antigen expression and reduced calponin expression. Intriguingly, we found that several key aspects of this uremia-induced phenotypic switch were stronger in ApSMCs as compared with VpSMCs, including the production of extracellular matrix (ECM) proteins, such as fibronectin, cellular calcification [high expression of RUNX family transcription factor 2 (Runx2), alkaline phosphatase (ALP), and Krüppel-like factor 4 (KLF-4)], and a proinflammatory state [high expression of tumor necrosis factor-α (TNF-α) and interleukin 6 (IL-6)]. Our findings suggest that uremia plays an important role in both the aggressive arteriovenous stenosis and CVD/PAD that affect many patients undergoing hemodialysis. This information could contribute to the development of novel uremia-specific therapies for both vascular access dysfunction and CVD/PAD in patients with ESKD.<b>NEW & NOTEWORTHY</b> This study was the first one to directly explore the differential response of arterial VSMCs and venous VSMCs to uremic serum exposure side by side. Both similarities and differences were detected in this in vitro study, which provides insight into the clinical manifestations we observed in patients with ESKD. Furthermore, these results may also be valuable information for uremia-specific therapies for both vascular access dysfunction and CVD/PAD in patients with ESKD.