Time-Dependent Vascular Dysfunction in Sepsis: Insights from an Ex Vivo Porcine Saphenous Vein Model

Presenter: Nubia Silva, University of Minnesota

Background: To model and characterize time-dependent vascular dysfunction induced by sepsis in an ex vivo porcine vein system.

Introduction: Sepsis is clinical syndrome driven by an overwhelming host response to infection, often progressing to circulatory failure and organ dysfunction. The vascular response to sepsis is characterized by vasoplegia—a state where blood vessels lose their ability to constrict, resulting in persistently low blood pressure resistant to usual therapies. Understanding how infection transitions to vasoplegia, particularly through vascular nitric oxide (NO) signaling, is essential for developing new therapies. We modeled these vascular changes ex vivo using porcine saphenous vein segments, providing insight to guide future in vivo sepsis studies.

Methods: Saphenous vein segments were collected post-mortem from n = 3 healthy adult pigs (~40–50 kg) euthanized following isolated heart protocols at the Visible Heart Laboratory (VHL), at the University of Minnesota. A longitudinal 8–10 cm skin incision was made on the medial aspect of the hind limb, from just above the ankle toward the knee. The saphenous vein, lying superficially, was identified by blunt dissection, carefully sparing adjacent nerves and arteries. Once mobilized using the “no touch” technique, the vein was clamped proximally and distally, transected, and placed in the PBS buffer. No additional anesthesia or analgesia was required specifically for vein harvest. Vein segments (~2 cm) were carefully dissected free of surrounding tissue, mounted in oxygenated muscle baths at 37°C and incubated with 1 μg/mL lipopolysaccharide (LPS) for 2, 4, or 6 hours to simulate inflammatory insult. Vascular relaxation responses to cumulative doses of carbachol (CCH; endothelium-dependent NO production) and sodium nitroprusside (SNP; endothelium-independent NO donor) were continuously recorded.

Results: Lipopolysaccharide (LPS) incubation of porcine saphenous vein segments caused a progressive, time-dependent decline in vascular relaxation. After 2 hours, CCH-induced, endothelium-dependent relaxation was reduced (p < 0.05). EDR further decreased at both four hours (p < 0.01) and six hours (p < 0.001). Sodium nitroprusside (SNP)-induced relaxation, reflecting smooth muscle responsiveness, also decreased notably at 6 hours (p < 0.05), demonstrating injury to both cellular components of veins. These findings highlight a progressive loss of vascular reactivity during sustained inflammatory exposure and identify potential therapeutic windows to prevent irreversible dysfunction implicated in vasoplegia.

Conclusion: Prolonged exposure to inflammatory stimuli (LPS) leads to time-dependent (progressive) impairment of both endothelial and smooth muscle responsiveness, demonstrating ex vivo recapitulation of the pathophysiology of vasoplegia. This model enables controlled investigations into the mechanisms of sepsis-induced vascular failure and provides a valuable platform for testing therapeutic strategies aimed at preserving vascular tone in critically ill patients.