Abstract Body: Background
Varicose veins (VV) are a complex vascular condition driven by both genetic and epigenetic influences. The disease is characterized by venous hypertension, inflammation, and dilation of the vein wall, leading to dysfunction in endothelial cells (ECs) and smooth muscle cells (SMCs). However, limited availability of patient-derived vascular cells has hindered detailed investigation of the underlying molecular mechanisms. Induced pluripotent stem cells (iPSCs) offer a valuable platform to model disease in vitro by enabling the generation of patient-specific vascular cell types that retain the donor’s genetic background.

Goals
By creating iPSCs from VV patients, we can model and characterize to recapitulate the disease phenotype. With these efforts, our goal is to elucidate the underlying disease mechanisms and validate the candidate genes that are, in part responsible for VV.

Methods
Vein tissues and peripheral blood mononuclear cells (PBMCs) were collected from 50 patients with varicose veins at the Stanford clinic. Tissue samples were subjected to single-nucleus multiomic analysis (snMultiome) to characterize cellular and regulatory features. In parallel, iPSC lines were generated from PBMCs and subsequently differentiated into ECs.

Results
snMultiome profiling of VV and control tissues enabled simultaneous assessment of chromatin accessibility and gene expression. High-quality nuclei were confirmed by ATAC-seq quality control metrics.
In parallel, we applied a chemically defined monolayer differentiation protocol that reproducibly generates 80–95% CD31 endothelial cells from iPSCs. Using this approach, iPSCs derived from both control and VV patients were successfully differentiated into endothelial cells. Expression of endothelial markers, including PECAM1, NOS3, CDH5, and VWF, was confirmed by RT-qPCR.

Conclusion
Patient-specific iPSC-derived vascular cells provide a platform to model individual responses to therapies and to identify genetic factors contributing to disease variability. In addition, this system offers a foundation for investigating molecular mechanisms underlying VV. However, the distinction between venous and arterial phenotypes was not assessed in this study.