Cellular and Molecular Changes Underpinning the Formation of Intimal Hyperplasia in a Model of Static Human Saphenous Vein Ex Vivo Culture.

OBJECTIVE: Intimal hyperplasia (IH) significantly limits the long term patency of saphenous vein grafts following bypass surgery, with no widely accepted human models that fully capture its complex pathogenesis. Although animal models, primarily murine systems, have provided mechanistic insights into IH, limitations persist in translating these findings to human pathophysiology. This study aimed to evaluate the translational value of a static ex vivo culture model using human saphenous vein segments to study IH. METHODS: Human saphenous vein segments obtained from patients who underwent lower limb bypass surgery were cultured ex vivo for seven days under static conditions. Bulk ribonucleic acid sequencing and spatial transcriptomics (GeoMx) were employed to characterise the localised transcriptional alterations, which were subsequently validated using histology, quantitative polymerase chain reaction, Western blotting, and immunohistochemistry. RESULTS: Cultured vein segments developed characteristic features of IH, including marked endothelial dysfunction, increased vascular smooth muscle cell (VSMC) apoptosis and proliferation, extracellular matrix remodelling, and neointima formation. Bulk and spatial transcriptomics revealed localised VSMC dedifferentiation and activation of inflammatory, oxidative stress, and extracellular matrix remodelling pathways similar to that of failed vein grafts. It was further observed that upregulation of osteogenic markers SOX9 and RUNX2, and RUNX2 inhibition limited IH. CONCLUSION: Using an established ex vivo human saphenous vein culture model, this study provided comprehensive characterisation of the vein intrinsic cellular programs driving IH, including endothelial dysfunction, VSMC plasticity, and osteochondrogenic transitions. Despite the lack of blood flow and blood borne cells, this translational model is valuable for evaluating novel therapeutic strategies targeting graft IH, such as inhibition of VSMC osteochondrogenic transformation.