Abstract
Purpose :
While anti-VEGF drugs show high efficacy in the treatment of neovascular AMD, many patients develop geographic atrophy after a longer treatment. We performed an experimental in vitro study to evaluate influence of anti-VEGF drugs on cultivated microglial cells, which are the intrinsic immune cells of the retina and may play a key role in degenerative processes in the retina.
Methods :
Microglial cells were isolated and cultivated from pig eyes. Identity of the cells was confirmed by staining against the typical microglial markers Iba1, CD11b and CD68. Microglial cells were exposed to the anti-VEGF drugs aflibercept and bevacizumab of different concentrations ranging from 0.33 to 5.71 mg/ml and ranibizumab at 5 mg/ml. Proliferation was checked by the Click-iT Edu assay, cell viability by ATP viability luciferase assay and phagocytic ability by measuring of the uptake of fluorescent micro beads. Moreover, we looked at the morphology of the cells and investigated influence of simultaneous presence of LPS or microglial inhibitors dexamethasone, minocycline and tripeptide TKP on phagocytosis.
Results :
Extent of proliferation was not changed by anti-VEGF drugs. At the highest concentration of the drugs, cells treated with bevacizumab and ranibizumab showed a reduced size, loss of processes and a “foam”-like appearance. Cells treated with aflibercept showed only mild changes of morphology. Cell viability was reduced down to about 70±5% at the highest drug concentrations. Ability to phagocytose decreased clearly already at 0.33 mg/ml bevacizumab (61.0±2.7%) and at 0.66 mg/ml aflibercept (61.4±4.9%). At the highest concentrations of the drugs, ability to phagocytose diminished almost completely (bevacizumab 2.4±0.5%, aflibercept 5.6±0.8%, ranibizumab 5.2±0.8%). LPS or the microglia inhibitors did not change the phenomenon that the drugs reduced phagocytosis, nevertheless, extent of that reduction was smaller depending on the inhibitor and the anti-VEGF drug. When anti-VEGF drug was exchanged by clean medium, ability to phagocytose recovered quickly depending on time and drug concentration.
Conclusions :
Anti-VEGF drugs reduce viability moderately and do not show effect on proliferation of microglial cells. In contrast, their ability to phagocytose is reduced dramatically. It may be speculated that reduced microglial phagocytosis allows enhanced accumulation of cellular debris, which in turn may promote progression of dry AMD.
This is a 2021 ARVO Annual Meeting abstract.