Aflibercept exerts structural protection against diabetic retinopathy-associated inner retinal abnormalities in the mouse STZ model

Abstract

Purpose : Streptozotocin (STZ)-induced diabetic retinopathy (DR) in rodents is widely-used model for drug discovery for novel anti-angiogenic agents targeting DR-associated phenotypes. The purpose of this Study was to investigate the pharmacological effects of aflibercept (Eylea^®) in the mouse STZ model.

Methods : Eight-week-old male C57BL/6JRj (Janvier, France) mice received five consecutive daily injections of STZ (60 mg/ml). Hyperglycemia was monitored daily for the first week after the last STZ injection and then weekly for 10 weeks. Mice that did not develop hyperglycemia (defined as a blood glucose level of at least 20 mmol/L) were excluded from the study. Mice received intravitreal injections of either PBS (2 µl) or aflibercept (2 µl; 80 µg/eye) on Days 17 and 28 post-STZ. Retinal structure and function were assessed by spectral domain optical coherence tomography (SD-OCT) and flash electroretinography (fERG) at baseline (prior to STZ) and 70 days after STZ injections. Data were analyzed using Two-Way ANOVA with Šidák's multiple comparison test.

Results : STZ resulted in significant loss of visual function, as indicated by a ~50% reduction in fERG a-wave amplitudes (145±7 vs. 72±7 µV; n=13; p<0.001) and a 45% reduction in b-wave amplitudes (164±9 vs. 107 ± 10 µV; n=12; p<0.001) in PBS-treated eyes. fERG amplitudes in aflibercept-treated eyes decreased by 37% for a-wave (145 ± 9 vs. 82 ± 9 µV; n=12; p<0.01) and 28% for b-wave (165 ± 12 vs. 107 ± 10 µV; n=12; p<0.01). However, there was no statistically significant difference between PBS- and aflibercept-treated eyes. Thickness of the inner retinal layer decreased significantly in PBS-treated eyes (60.2 ± 4.7 µm vs. 56.1 ± 0.6 µm; n=13; p<0.01). Here, aflibercept prevented thinning of the inner retinal layer (60.2 ± 0.4 µm vs. 59.2 ± 0.9 µm, respectively; n=11; p>0.05).

Conclusions : Induction of DR phenotypes by STZ resulted in abnormalities of both the inner and the outer retina. Aflibercept did not protect against functional effects quantified by fERG. However, complete structural protection of the inner retinal layer was observed in aflibercept-treated eyes. Additional studies are warranted assessing the structure-function relationships in the mouse STZ model.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.