Abstract
Purpose :
Retinal pigment epithelium (RPE) is known to secrete factors important in retinal homeostasis. How this secretome changes in diabetics treated with anti-vascular endothelial growth factor (VEGF) drugs is unclear. We present an in vitro model to mimic the hypoxic and and high glucose state observed in diabetic retinopathy and to evaluate the change in secretion of growth factors by the RPE in the presence of anti-VEGF drugs.
Methods :
ARPE-19 and human primary RPE cells were cultured in media containing 1% FCS and either low/physiological (1g/L) or high (4.5g/L) glucose. Hypoxic stress was induced through addition of cobalt chloride (CoCl2). Cell viability was assessed using a resazurin assay. Expression of HIF-1α was measured using Western blot. Secretion of VEGF-A was measured by an enzyme-linked immunosorbent assay (ELISA). Following optimisation of the stress condition, clinically relevant doses of bevacizumab, ranibizumab and aflibercept were added to the media. Secretion of placental growth factor (PlGF) and basic fibroblast growth factor (bFGF) was measured by ELISA after 24 hours of treatment. Changes were measured with one-way ANOVA.
Results :
HIF-1α expression was increased at all concentrations of CoCl2 when ARPE-19 were cultured in low glucose media but only at concentrations equal to or above 200μM in high glucose media. VEGF-A secretion was significantly upregulated at all concentrations of CoCl2 regardless of glucose concentration. bFGF secretion was increased with addition of bevacizumab and ranibizumab in the presence of oxidative stress in low but not high glucose media. This effect was mitigated with the addition of all anti-VEGF drugs under CoCl2-induced oxidative stress. Ranibizumab and aflibercept tended to increase secretion of bFGF in high glucose and oxidative stress conditions. PlGF secretion was not detected in control or treatment groups. Primary cells were more resistant to hypoxic stress than ARPE-19, requiring higher concentrations of CoCl2 to lose viability.
Conclusions :
Anti-VEGF drugs may influence bFGF secretion from RPE in different ways when cells are exposed to low and high glucose under oxidative stress. This has potential clinical implications for preservation of vision in patients receiving anti-VEGF therapy. Further studies are warranted to determine the impacts of these drugs on multiple factors involved in neuroprotection and retinal fibrosis in diabetes.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.