Dhyana SharmaNational Institute for Biological Standards and Control (NIBSC), Uk
Title: Investigating the Mechanisms behind the Development of Acquired Resistance to Anti-VEGF Therapy in Neovascular Diabetic Eye Disease
Diabetes can cause vision loss through severe retinal microvascular complications, leading to the development of proliferative diabetic retinopathy (PDR) and diabetic macular edema (DME). Abnormal angiogenesis and increased vascular permeability are the major pathophysiological features of both diseases and are exacerbated by the over-expression of vascular endothelial growth factor (VEGF). Anti-VEGF biologic drugs bind VEGF to perturbate pathological angiogenesis. Clinical findings present a decrease in efficacy in some patients after treatment, suggesting the development of acquired resistance. The present study examines the mechanisms behind this in vitro, focusing on neuropilin-1 (NRP-1) and its ligands, which have been associated with pathophysiological features of PDR and DME independently to VEGF.
Human retinal microvascular endothelial cells (HRMECs) have been characterized as a cellular model for this project. The effects of anti-VEGF treatment on NRP-1 and NRP-1 ligands were measured by treating HRMECs with repeated bevacizumab over 10 days. Samples were collected over the treatment period for examination of changes in cell surface expression of NRP-1 and secretion of NRP-1 ligands. NRP-1 blocking antibody was applied to co-cultures of endothelial cells and fibroblasts, an in vitro model of angiogenesis, and HRMEC-seeded transwell inserts, an in vitro model of the blood-retinal barrier, to assess microtubule formation and cellular permeability respectively.
HRMEC surface expression of NRP-1 increases after repeated treatment of bevacizumab, with downregulated secretion of its ligand, placental growth factor. Further studies suggest the latter may be an indirect effect of VEGF blockade. NRP-1 inhibition elicits an angiostatic effect on endothelial cells, independently to bevacizumab. These findings suggest a role of NRP-1 and NRP-1 ligands in retinal endothelial growth and differentiation independently to VEGF, potentially uncovering a mechanism for the development of acquired resistance to anti-VEGF therapy in the retinal microvasculature.
Dhyana Sharma is a 3rd year PhD candidate at the National Institute for Biological Standards and Control (NIBSC, a branch of the Medicines and Healthcare products Regulatory Agency, MHRA) and University College London (UCL). Studying under Dr Haiyan Jia (NIBSC) and Professor Ian Zachary (UCL), her project investigates the mechanisms behind the development of acquired resistance to anti-VEGF therapy in neovascular diabetic eye disease, with particular focus on neuropilin-1 and its ligands. With her prior research encompassing elements of study into chemotherapy, chronic pain, childhood cancer, angiogenesis and neovascular eye diseases, Dhyana’s background knowledge is broad. Her aim for the remainder of her study is to narrow down this broad knowledge and learn the intricacies of the many pathways researched within her PhD project.