Lenti-viral overexpression of RhoGEF Trio reduces CD8 T cell extravasation into atherosclerotic vein graft lesions in mice

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Rembrandt Institute for Cardiovascular Sciences Background In advanced atherosclerotic plaques, such as vein graft lesions, neovessels grow into the hypoxic plaque. This intraplaque angiogenic neovessels lack proper endothelial cell-cell junctions and are therefore susceptible to extravasation of leukocytes, which results in inflammation and atherosclerosis. T cells are the largest leukocyte subset found in atherosclerotic plaques and are key drivers of inflammation and plaque progression. RhoGEF Trio improves endothelial barrier function by strengthening endothelial cell-cell junctions in vitro, but its effect on T cell transmigration and its therapeutic potential to impede atherogenesis remains unknown. Methods ApoE3*Leiden mice (n=10/group) underwent bypass surgery in which a donor caval vein was interpositioned into the arterial circulation at the site of the right common carotid artery. Immediately post-operatively, a pluronic gel containing either GFP-Lentivirus (LV) (control) or Trio-GFP-LV (Trio) was locally applied around the vein graft to induce local overexpression of Trio. At post-op day 28, vein grafts were harvested and processed for morphometric and compositional analysis of the atherosclerotic lesions. Additionally, CD4 and CD8 T cells were isolated from healthy human donors and used in vitro to assess the role of Trio on trans-endothelial migration over in vitro-cultured HUVECs. Results At post-op day 28, both luminal and neovessel endothelial cells were GFP positive indicating successful transfection. CD8 T cell infiltration into the atherosclerotic plaque was reduced in the Trio group (45%, p=0.0426), whilst plaque size and the number of neovessels were unaffected. Mechanistically, we observed that adherence of CD8, but not CD4 T cells to the endothelial monolayer was reduced in vitro upon transfection with Trio-LV. This resulted in a decrease in the absolute number of transmigrated CD8 T cells (56%, p=0.0197), whilst the number of transmigrated CD4 T cells was unaffected. Interestingly, CD8 T cells exhibited no difference trans-/paracellular diapedesis, whilst for CD4 T cells Trio overexpression induced transcellular, rather than paracellular, transmigration. Conclusions LV transfection of vein grafts by local application of a pluronic gel holds promise a therapeutic strategy to improve bypass surgery outcomes. LV transfection with RhoGEF Trio did reduce CD8 T cell transmigration (in vivo and in vitro), but not CD4 T cell transmigration (in vitro) into the atherosclerotic plaque, whilst plaque size was not affected. Ongoing investigations focus on the effect of Trio on micro-vascular leakage as well as infiltration of other immune cells into the plaque.