Procoagulant effects of extracellular vesicles in patients with livedo reticularis.

Background: Extracellular vesicles (EVs) are lipid-delimited particles that mediate intercellular communication and have been implicated in both autoimmune and prothrombotic conditions. Livedo reticularis (LR) is a cutaneous vascular pattern associated with impaired dermal arteriolar blood flow and increased vascular risk, yet the contribution of EVs to LR pathogenesis has not been studied. Objectives: To characterize the procoagulant properties, cellular origin, and proteomic profile of plasma-derived EVs in LR. Methods: Plasma-derived EVs were isolated from 12 LR patients and seven healthy controls. Tissue factor (TF) activity, EV concentration, proteomic cargo, and cellular origin were assessed using chromogenic assays, nanoparticle tracking analysis, mass spectrometry, and flow cytometry. Results: TF activity was significantly increased in LR plasma and was enriched within the small EV fraction. Sequential centrifugation demonstrated a stepwise reduction in TF activity, implicating both large and small EVs as contributors. EV concentrations did not differ between groups, indicating qualitative rather than quantitative differences. Proteomic analysis revealed a distinct EV cargo in LR, with widespread protein downregulation and enrichment of coagulation, vascular homeostasis, and VEGF signaling pathways. Notably, KLF8 was markedly reduced. The composition of cells of origin was different, as EVs from LR patients showed an increased leukocyte-derived and decreased platelet-derived profile. Conclusion: LR is associated with an EV-driven procoagulant and inflammatory phenotype characterized by TF activity, altered cargo, and immune-cell origin, suggesting a role for EV-mediated thrombo-inflammatory microvascular dysfunction in LR pathogenesis. Abundance of KLF8 is markedly reduced, which renders it a target for further mechanistic research.