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Updated: Jul 24, 2025
Isolation of Human Primary Valve Cells for In vitro Disease Modeling
Published on: April 16, 2021
PAI-1 Overexpression in Valvular Interstitial Cells Contributes to Hypofibrinolysis in Aortic Stenosis
Magdalena Kopytek1,2, Michał Ząbczyk1,2, Piotr Mazur3,4
1Thromboembolic Disorders Department, Institute of Cardiology, Jagiellonian University Medical College, 80 Pradnicka St., 31-202 Krakow, Poland.
Insights
In aortic stenosis, high LDL cholesterol increases PAI-1, a protein that hinders clot breakdown. This contributes to reduced fibrinolysis and disease severity.
Area of Science:
- Cardiovascular Biology
- Hemostasis and Thrombosis
- Molecular Medicine
Background:
- Aortic stenosis (AS) is linked to hypofibrinolysis, a condition impairing clot breakdown, but the underlying mechanisms remain unclear.
- Low-density lipoprotein (LDL) cholesterol's role in this process, specifically its effect on plasminogen activator inhibitor 1 (PAI-1), requires further investigation.
Purpose of the Study:
- To investigate the relationship between LDL cholesterol, PAI-1 expression, and hypofibrinolysis in patients with severe aortic stenosis.
- To elucidate the role of the nuclear factor-kappa B (NF-κB) pathway in mediating PAI-1 expression in aortic valve interstitial cells (VICs).
Main Methods:
- Analysis of PAI-1, NF-κB, and lipid accumulation in stenotic aortic valves from 75 patients compared to 5 controls.
- In vitro studies assessing PAI-1 expression and fibrinolytic capacity in VICs stimulated with LDL, using PAI-1 and NF-κB inhibitors.
Main Results:
- PAI-1 expression was detected exclusively in AS valves, correlating with lipid accumulation and disease severity, and co-localized with NF-κB.
- LDL stimulation of VICs increased PAI-1 levels and prolonged clot lysis time (CLT), indicating reduced fibrinolysis.
- Inhibition of PAI-1 or NF-κB restored normal CLT, with NF-κB inhibition reducing PAI-1 and SERPINE1 expression.
Conclusions:
- Lipid accumulation in severe AS drives valvular PAI-1 overexpression, contributing to hypofibrinolysis and disease progression.
- The NF-κB pathway is implicated in regulating PAI-1 expression in AS, offering potential therapeutic targets.
Abstract:
Aortic stenosis (AS) is associated with hypofibrinolysis, but its mechanism is poorly understood. We investigated whether LDL cholesterol affects plasminogen activator inhibitor 1 (PAI-1) expression, which may contribute to hypofibrinolysis in AS. Stenotic valves were obtained from 75 severe AS patients during valve replacement to assess lipids accumulation, together with PAI-1 and nuclear factor-κB (NF-κB) expression. Five control valves from autopsy healthy individuals served as controls. The expression of PAI-1 in valve interstitial cells (VICs) after LDL stimulation was assessed at protein and mRNA levels. PAI-1 activity inhibitor (TM5275) and NF-κB inhibitor (BAY 11-7082) were used to suppress PAI-1 activity or NF-κB pathway. Clot lysis time (CLT) was performed to assess fibrinolytic capacity in VICs cultures. Solely AS valves showed PAI-1 expression, the amount of which was correlated with lipid accumulation and AS severity and co-expressed with NF-κB. In vitro VICs showed abundant PAI-1 expression. LDL stimulation increased PAI-1 levels in VICs supernatants and prolonged CLT. PAI-1 activity inhibition shortened CLT, while NF-κB inhibition decreased PAI-1 and SERPINE1 expression in VICs, its level in supernatants and shortened CLT. In severe AS, valvular PAI-1 overexpression driven by lipids accumulation contributes to hypofibrinolysis and AS severity.
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