Cytokine Levels in Experimental Branch Retinal Vein Occlusion Treated With Either Bevacizumab or Triamcinolone Acetonide.

Purpose: To compare gene expression changes following branch retinal vein occlusion (BRVO) in the pig with and without bevacizumab (BEV) and triamcinolone acetonide (TA). Methods: Photothrombotic BRVOs were created in both eyes of four groups of nine pigs (2, 6, 10, and 20 days). In each group, six pigs received intravitreal injections of BEV in one eye and TA in the fellow eye, with three pigs serving as untreated BRVO controls. Three untreated pigs served as healthy controls. Expression of mRNA of vascular endothelial growth factor (VEGF), glial fibrillary acidic protein (GFAP), dystrophin (DMD), potassium inwardly rectifying channel subfamily J member 10 protein (Kir4.1, KCNJ10), aquaporin-4 (AQP4), stromal cell-derived factor-1α (CXCL12), interleukin-6 (IL6), interleukin-8 (IL8), monocyte chemoattractant protein-1 (CCL2), intercellular adhesion molecule 1 (ICAM1), and heat shock factor 1 (HSF1) were analyzed by quantitative reverse-transcription polymerase chain reaction. Retinal VEGF protein levels were characterized by immunohistochemistry. Results: In untreated eyes, BRVO significantly increased expression of GFAP, IL8, CCL2, ICAM1, HSF1, and AQP4. Expression of VEGF, KCNJ10, and CXCL12 was significantly reduced by 6 days post-BRVO, with expression recovering to healthy control levels by day 20. Treatment with BEV or TA significantly increased VEGF, DMD, and IL6 expression compared with untreated BRVO eyes and suppressed BRVO-induced CCL2 and AQP4 upregulation, as well as recovery of KCNJ10 expression, at 10 to 20 days post-BRVO. Conclusions: Inflammation and cellular osmohomeostasis rather than VEGF suppression appear to play important roles in BRVO-induced retinal neurodegeneration, enhanced in both BEV- and TA-treated retinas. Translational Relevance: Inner retinal neurodegeneration seen in this acute model of BRVO appears to be mediated by inflammation and alterations in osmohomeostasis rather than VEGF inhibition, which may have implications for more specific treatment modalities in the acute phase of BRVO.

Inner Retinal Changes in Acute Experimental BRVO Treated With Bevacizumab or Triamcinolone Acetonide.

Purpose: Apoptosis is a key process in neural degeneration associated with retinal vascular diseases. Vascular endothelial growth factor (VEGF) antagonists, including bevacizumab, are used to treat macular edema in these diseases. As VEGF has a critical role in the preservation of retinal neuronal cells, this study investigates the effects of bevacizumab on neural damage in a pig model of branch retinal vein occlusion (BRVO) and compares it with triamcinolone acetonide (TA) which is reported to possess neuroprotective properties. Methods: Thirty-six pigs had a photothrombotic BRVO in both eyes. Six pigs were injected with bevacizumab in one eye and TA in the fellow eye, then they were sacrificed, the eyes enucleated, and retinas processed at 2, 6, 10, and 20 days, respectively, together with three pigs (six eyes) BRVO only and three normal pigs (six eyes). Neuronal degeneration (apoptosis) and associated inner retinal changes were determined by terminal deoxyynuclotidyl transferase dUTP nick-end labeling (TUNEL), histology, and immunohistochemistry for macrophages. Results: TUNEL labeling showed significantly higher apoptosis rates in the ganglion cell layer (GCL) and the inner nuclear layer (INL) in the bevacizumab-treated compared with the TA-treated retinas at 2, 10, and 20 day time points after occlusion (P < 0.05). Pyknotic cells were significantly higher in the GCL in bevacizumab-treated eyes at 6, 10, and 20 days and in the INL at 2 days compared to TA-treated retinas (P < 0.05). Macrophage infiltration was seen at all time points in both untreated and treated retinas with an absence of significance between bevacizumab- and TA-treated retinas (P > 0.05). Conclusions: Neurodegeneration in the BRVO acute phase is exacerbated by current standard treatments for BRVO. These results may have implications for the timing and treatment type. Translational Relevance: In the acute phase of BRVO, VEGF suppression with bevacizumab and to a lesser extent with triamcinolone exacerbates apoptosis in the inner retinal layers, which has implications for both the timing and choice of treatment.