Experimental Study Of Anti-VEGF Drugs Bevacizumab On Retinal Safety

Background:Vascular endothelial growth factor (VEGF) has been implicated as the key angiogenic stimulus responsible for the formation of ocular neovascularization, especially exudative AMD. Recently, the development of VEGF antagonists introduced a new treatment regimen which has led to better long-term results for ocular neovascularization. Bevacizumab (Avastin; Genentech, South San Francisco, CA) is used off-label in AMD and has shown good effectiveness and tolerability. However, previous research has shown that VEGF exerts neutrophic and neuroprotective effects on nervous system. This may raise the concern that therapeutic inhibition on VEGF for the treatment of neovascular eye diseases may have an adverse impact on the neuroprotective effects of VEGF, thus may cause the injury to neural retinal cells, even though clinical evidence for this theoretical assumption is lacking to date.Objective:To evaluate the effect of Bevacizumab on the neurosensory retinas in culture to approve the safety in clinical use in ophthalmology.Methods:The complex eye tissues of the adult porcine, including retina, choroid and sclera, were cultured for12,24and48hours. Bevacizumab was added to the culture at different concentrations (group A were given no Bevacizumab as controls, group B, C and D were given Bevacizumab at the concentrations of0.125,0.25,1.25mg/ml respectively). After12,24and48hours in culture, the neurosensory retinas were analyzed histologically under light microscope, immunohistochemically for the expression of glial fibrillary acidic protein (GFAP), by TUNEL for apoptosis and by electromicroscopy for the ultrastructure.Results:Histomorphologic observation showed well-preserved nuclear layers with no signs of cellular disorganization, retinal inflammation after exposure to group B and the controls, whereas in group C and D, found the swelling and the loss of retinal ganglion cells (RGCs), and the disorganized photoreceptor layer (PRL). TUNEL system showed no evident increase of apoptosis in each retinal nuclear layer in group B compared to the controls (P>0.05). Group C (24h,48h) and group D (12h,24h) had an evident rise in cell apoptosis in RGC layer (P<0.05), but not in the internal nuclear layer and outer nuclear layer. GFAP expression in Muller cells were detected in group C (48h) and group D (24h,48h), no such signals were observed in other groups and in controls. By electron microscopic observation, the dilation of the rough endoplasmic reticulum(RER) in RGCs, and the decrease even loss of the mitochondrial cristae in the inner segraents of photoreceptors were found in group C and D.Conclusion:No evident signs of retinal toxicity were found histologically, immunohistochemically, by TUNEL testing and by electron microscopy in the concentration of0.125mg/ml, while some certain damage of RGCs and photoreceptor cells were observed in the concentrations of0.25mg/ml and1.25mg/ml, which indicates a lower concentration of Bevacizumab is probably safe to the neurosensory retina, and higher concentration may have an advese effect. Therefore, we should be cautious to the dosage and frequency of Bevacizumab when using in the vitreal injection.