Sharma, Dhyana;
(2024)
Determining the Adaptations of Retinal Endothelial Cells Which Elicit the Development of Acquired Resistance to Anti-VEGF Therapy in Neovascular Eye Diseases.
Doctoral thesis (Ph.D), UCL (University College London).
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Abstract
Neovascular eye diseases are characterised by aberrant angiogenesis and hyperpermeability of retinal blood vessels through increased vascular endothelial growth factor (VEGF). Anti-VEGF agents like bevacizumab are a primary therapeutic strategy but display acquired resistance over time. Neuropilin-1 has been associated with VEGF-independent angiogenesis and permeability mechanisms, so may be a pathway through which resistance develops. This study sought to investigate the mechanisms of acquired resistance to bevacizumab in vitro, focussing on the effect of bevacizumab on neuropilin-1 alongside global changes in gene expression in human retinal microvascular endothelial cells (HRMECs). The cells were characterised based on their morphology, characteristic endothelial cell behaviours, and response to VEGF and bevacizumab in comparison to human umbilical vein endothelial cells (HUVECs). The effect of bevacizumab on the expression of neuropilin-1, neuropilin-2 and VEGF receptor 2 (VEGFR2) and secretion of neuropilin-1 ligands was then examined, alongside the role of neuropilin-1 blockade on endothelial tubule formation and proliferation mechanisms. This was followed by the investigation of the effect of bevacizumab on the global gene expression of HRMECs through RNA sequencing. The findings revealed key endothelial cell characteristics of HRMECs and HUVECs were similar, but with HRMECs being larger and more sensitive to higher VEGF concentrations. Bevacizumab increased the surface expression of neuropilin-1 and VEGFR2 without increasing whole cell or mRNA expression. Bevacizumab also reduced the secretion of the neuropilin-1 ligand PlGF over time compared to VEGF-only controls. RNA sequencing found a significant downregulation in DLL4 gene expression, and genes associated with Wnt/β-catenin signalling after bevacizumab treatment, potentially associated with pathological mechanisms such as VEGF-independent retinal vessel hyper branching, angiogenic tip cell formation, and disruption of blood-retinal-barrier homeostasis. These findings suggest that vascular processes related to DLL4 downregulation may be mechanisms through which anti-VEGF therapy elicits acquired resistance and disease progression in neovascular eye diseases.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | Determining the Adaptations of Retinal Endothelial Cells Which Elicit the Development of Acquired Resistance to Anti-VEGF Therapy in Neovascular Eye Diseases |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Copyright © The Author 2024. Original content in this thesis is licensed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) Licence (https://creativecommons.org/licenses/by-nc/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request. |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Medical Sciences UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Medical Sciences > Div of Medicine |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10200171 |
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