Hypothesis

With advancing age, senescent endothelial cells release extracellular vesicles (EVs) that carry ultra‑large von Willebrand factor (VWF) multimers and stabilize circulating factor VIII (FVIII), thereby amplifying thrombin generation independently of plasma VWF/FVIII concentration alone.

Mechanistic Rationale

• Endothelial senescence, driven by cumulative DNA damage and chronic inflammation, up‑regulates the secretory autophagy pathway, loading EVs with VWF, P‑selectin, and microRNA‑126 that suppresses ADAMTS13 activity 1.
• EV‑associated VWF resists proteolytic cleavage, preserving its high‑molecular‑weight forms that bind FVIII with greater affinity, reducing its clearance and extending its half‑life 2.
• The EV surface phosphatidylserine provides a catalytic platform for tenase and prothrombinase complexes, further boosting thrombin burst measured by calibrated automated thrombography (CAT) 3.

Testable Predictions

1. Plasma EV‑VWF and EV‑FVIII levels will correlate more strongly with age‑related CAT peak thrombin and endogenous thrombin potential than total VWF antigen or FVIII activity.
2. In elderly volunteers, a short course of the senolytic drug dasatinib +  quercetin will reduce circulating EV‑VWF/EV‑FVIII by ≥30 % and lower CAT parameters without increasing bleeding time.
3. Genetic deficiency of ADAMTS13 will exacerbate the EV‑mediated effect, whereas recombinant ADAMTS13 administration will normalize EV‑VWF multimer size and thrombin generation.

Experimental Approach

• Cohort: 120 participants aged 60‑80, stratified by blood group O vs non‑O, with baseline comorbidities recorded.
• Sampling: Collect platelet‑poor plasma, isolate EVs by size‑exclusion chromatography, quantify EV‑VWF (ELISA) and EV‑FVIII (chromogenic assay).
• Functional assay: Perform CAT to derive lag time, peak thrombin, and endogenous thrombin potential.
• Intervention sub‑study: Randomized, double‑blind, placebo‑controlled 4‑week dasatinib + quercetin vs placebo; repeat EV and CAT measurements.
• Outcome: Primary – change in EV‑VWF; secondary – change in CAT peak thrombin and bleeding time (IPASS).

If EV‑VWF/FVIII drives the thrombotic phenotype, senolytic reduction of EVs should uncouple total VWF/FVIII from functional thrombin generation, offering a mechanistic target that mitigates thrombosis without exacerbating bleeding—a direct test of the hypothesis.