Individual and temporal variability of the retina after chronic bilateral common carotid artery occlusion (BCCAO)

Animal models of disease are an indispensable element in our quest to understand pathophysiology and develop novel therapies. Ex vivo studies have severe limitations, in particular their inability to study individual disease progression over time. In this respect, non-invasive in vivo technologies offer multiple advantages. We here used bilateral common carotid artery occlusion (BCCAO) in mice, an established model for ischemic retinopathy, and performed a multimodal in vivo and ex vivo follow-up. We used scanning laser ophthalmoscopy (SLO), ocular coherence tomography (OCT) and electroretinography (ERG) over 6 weeks followed by ex vivo analyses. BCCAO leads to vascular remodeling with thickening of veins starting at 4 weeks, loss of photoreceptor synapses with concomitant reduced b-waves in the ERG and thinning of the retina. Mononuclear phagocytes showed fluctuation of activity over time. There was large inter-individual variation in the severity of neuronal degeneration and cellular inflammatory responses. Ex vivo analysis confirmed these variable features of vascular remodeling, neurodegeneration and inflammation. In summary, we conclude that multimodal follow-up and subgroup analysis of retinal changes in BCCAO further calls into question the use of ex vivo studies with distinct single end-points. We propose that our approach can foster the understanding of retinal disease as well as the clinical translation of emerging therapeutic strategies.