Uremic Serum Exposure Leads to Differential Phenotypic Switch in Porcine Arterial and Venous Smooth Muscle Cells

Abstract

Many end-stage kidney disease (ESKD) patients 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 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 MTT assay demonstrated that 30% of uremic serum was able to stimulate 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 PCNA expression and reduced calponin expression. Intriguingly, we found that several key aspects of this uremia-induced phenotypic switch were stronger in ApSMCs as compared to 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 kruppel-like factor 4 (KLF-4)), and a proinflammatory state (high expression of tumor necrosis factor α (TNFα) 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 hemodialysis patients. This information could contribute to the development of novel uremia-specific therapies for both vascular access dysfunction and CVD/PAD in ESKD patients.

Keywords: Uremia; cardiovascular disease; peripheral arterial disease; vascular access; vascular smooth muscle cells.