UBC Theses and Dissertations
Vascular endothelial growth factor-induced permeability in the pathogenesis of cardiac allograft vasculopathy Wong, Brian Wing Chi
Rationale: Endothelial dysfunction can lead to increased permeability, and this may contribute to the pathogenesis of cardiac allograft vasculopathy (CAV). This dissertation focuses on vascular endothelial growth factor (VEGF), a protein that can mediate angiogenesis and is a potent inducer of vascular permeability. It was my goal to characterize the expression and localization of VEGF in CAV and to elucidate the mechanisms which may relate to its role in the pathogenesis of CAV. Central hypothesis: VEGF plays a significant role in the pathogenesis of CAV by inducing endothelial cell hyperpermeability to low-density lipoproteins (LDL). Methods: Immunohistochemistry and in situ hybridization for VEGF were performed on coronary artery segments from patients with native atherosclerosis (NA), diabetes mellitus with atherosclerosis (DM) and CAV. Human coronary artery endothelial cell (HCAEC) and human cardiac microvascular endothelial cell (HCMEC) primary cultures were used to investigate VEGF-induced permeability using transendothelial electrical resistance (TER) measurements, immunocytochemistry for tight junction proteins and LDL permeability. A mouse model of heterotopic cardiac transplantation was used to assess the therapeutic potential of abrogation of VEGF function on CAV using soluble VEGF receptor-1 (sVEGFR1) administration. Key results: There was significant upregulation of VEGF-A in the intima and media of coronary arteries in CAV, NA and DM. As well, there was significant upregulation of VEGF-D in the media of coronary arteries in CAV and in the intima and media of coronary arteries in DM. Treatment with VEGF-A₁₂₁, VEGF-A₁₆₅ and VEGF-D significantly decreased TER, significantly increased LDL permeability, and induced the formation of intercellular gaps and decreased immunoreactivity of the tight junctional protein zonula occludens-1 (ZO-1) along adjacent endothelial membranes in confluent monolayers. Co-incubation with the mitogen-activated protein kinase kinase (MAPKK/MEK1) inhibitor U0126 prevented the formation of intercellular gaps and maintained regularity of ZO-1 immunoreactivity along endothelial membranes. Administration of sVEGFR1 in a mouse model of heterotopic cardiac transplantation resulted in a significant decrease in luminal narrowing in transplanted hearts at 21 days post-transplantation. Conclusion: Taken together, this body of work clearly demonstrates that VEGF plays a significant role in the pathogenesis of CAV.
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