Introduction:
ESKD patients suffer from both an aggressive vascular access stenosis in the venous segment of AVFs and AVGs and widespread peripheral arterial disease (PAD). Both disease states respond poorly to conventional endovascular and surgical interventions. Despite the magnitude of the clinical problem, the exact pathogenetic role of the uremic state in both these conditions remains unclear. The goal of this study was to investigate the impact of uremic serum on both the activation and phenotypic switch profile of pig venous (VpSMCs) and arterial (ApSMCs) smooth muscle cells.
Methods:
Primary cultures of VpSMC and ApSMC were generated from pig carotid artery and jugular vein. Uremic serum was obtained from our previously described pig model of uremia (documented creatinine of >8mg/dL for over 3 weeks). Control serum was obtained from an age matched non-uremic pig. The MTT assay was used to assess cell proliferation and a cell-scratch assay was utilized to assess cell migration. Western blot expression was used to assess markers of cellular proliferation (PCNA and p53), phenotypic switch (myocardin and calponin), extracellular matrix (ECM) production (vitronectin and fibronectin) and calcification (Runx2).
Results:
The MTT assay demonstrated that 30% uremic serum was able to stimulate the proliferation of both arterial (1.25±0.14 fold increase) and venous (1.17±0.13 fold increase) SMCs. Uremic serum also consistently enhanced PCNA and p53 expression in both cell types. The production of ECM proteins such as vitronectin and fibronectin was also increased when cells were exposed to uremic serum (ApSMC > VpSMC). SMC migration measured by the scratch assay showed that uremic serum increased the migration of both ApSMC (1.21±0.14 fold increase) and VpSMC (1.23±0.12 fold increase). Uremia also induced a phenotypic switch in both cell types (greater in ApSMC), with a suppression of myocardin and calponin expression (indicating a switch to a more activated, dedifferentiated and synthetic phenotype). Uremic serum also significantly stimulated cellular calcification (Runx2) particularly in ApSMC.
Conclusions:
Uremia results in a dedifferentiation (phenotypic switch) of both venous and arterial SMCs in vitro with an increase in proliferation and migration, ECM production and expression of cell calcification markers. These changes were often exaggerated in ApSMCs as compared to VpSMCs. Our findings suggest that uremia per se could play an important role in both the aggressive arteriovenous stenosis and PAD in hemodialysis patients. In addition, continued investigation into the molecular pathways responsible for this cellular activation could result in novel uremia specific therapies for both vascular access dysfunction and peripheral arterial disease in hemodialysis patients.
Some of the above data would have been presented at ASN Kidney Week 2024
I have no potential conflict of interest to disclose.
I did not use generative AI and AI-assisted technologies in the writing process.