An optical coherence tomography based in vivo scoring system for experimental autoimmune uveoretinitis

Abstract

Purpose: Despite advances in assessing immune responses affecting the retina, post-mortem histology remains the standard for quantifying disease severity in murine experimental autoimmune uveoretinitis (EAU). Therefore, progression or the effect of therapeutic intervention cannot be observed in real time. We wished to ascertain whether optical coherence tomography (OCT) could detect intraretinal changes during inflammation and determine its utility as a tool for accurate in vivo scoring of EAU.

Methods: Three independent cohorts of C57BL/6J mice were immunised with IRBP 1-20, CFA and pertussis toxin. Contemporaneous Spectralis-OCT scanning, fluorescein fundus angiography (FFA), topical endoscopic fundal imaging (TEFI) and CD45-immunolabelled histology were performed at 15, 26, 36 and 60 days post-induction. OCT features were characterised on corresponding retinal flat-mounts using immunohistochemistry for T-cells (CD4 & CD8), activated myeloid cells (lectin B4), microglia (Iba1) and vascular changes (collagen IV). Imaris software was used for 3D reconstructions. All eyes were scored by three masked assessors, using our newly developed OCT-based EAU scoring system as well as established TEFI and histology-based analyses.

Results: OCT identified optic disc swelling and vitreous opacities, which corresponded to CD45+ cell infiltration on histology. Vasculitis detected by FFA and OCT matched inflamed vessels surrounded by myeloid and T-cell infiltrates in retinal flat-mounts and could be differentiated from unaffected vessels. Evolution of these changes could also be followed over time in the same eye. Structural changes such as retinal folds were visible and encapsulated mixed populations of activated myeloid cells, T-cells and microglia as shown by 3D reconstruction. Using these features, an OCT-based EAU scoring system was developed, with significant correlation to histological (Pearson r²=0.6392, P<0.0001, n=31 eyes) and TEFI based scoring systems (r²=0.6784, P<0.0001).

Conclusions: OCT distinguishes key features of murine EAU in vivo, permits dynamic assessment of intraretinal changes, accurate disease stage synchronisation prior to histological or cellular assessment and more efficient animal usage. By correlating OCT signals with immunohistochemistry in EAU, our findings may also inform the interpretation of OCT changes in human uveitis.

Keywords: 746 uveitis-clinical/animal model • 552 imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • 557 inflammation