Abstract
Purpose: :
Immune-mediated inflammation and blood-retina-barrier integrity are implicated in retinal degenerative diseases. Neuroprotectin D1 (NPD1), a DHA-derived lipid mediator, inhibits leukocyte infiltration across blood-brain-barrier after ischemia-reperfusion. Two chemokine genes, Ccl2 & Cx3cr1, are essential to leukocyte brain/retina trafficking. Deficiency in mouse (DKO) results in retinal degenerative pathologies. To establish a basis for studies of NPD1 on chemokine signaling, blood-retina-barrier integrity, and retinal degeneration, we assessed the onset, locality, and progression of retinal pathologies in this mouse.
Methods: :
DKO & WT mice 1 to 27 mo were used. Redfree (RF) and autofluorescent (AF) funduscopy, fluorescein angiography, and 3D SD-OCT were used with a Spectralis HRA+OCT imaging system. These results were compared to histologic sections. Image analysis and en face transformations of 3D OCT data were performed with NIH ImageJ and our "Open Heyex Raw" plugin (Experimental Eye Research, 2010).
Results: :
Many irregular regions were detected by RF & AF. SD-OCT showed focal columns of hyper-reflective densities in ONL. Histology validated OCT abnormalities as lesions. En face transformation of 3D SD-OCT at ONL revealed lesions shaped similar to RF and AF exams. Image analysis showed that RF, AF, and en face OCT lesions colocalize. Discrete lesions are detectable by SD-OCT at 21 d but not in WT. Large lesion complexes develop as lesions arise and fuse with adjacent lesions. These mostly occur in central inferior retina and spread laterally. A maturity timeline exists as old central lesions degenerate by 8 mo, leaving younger lesions toward the periphery. Photoreceptors degenerate slower in non-lesioned areas. In superior retina, only slow age-related degeneration occurs in ONL. Retinal neovascularization and leakage occurs inferiorly after 7 mo. Here, no anastomosis with choroidal vessels was seen.
Conclusions: :
We have shown hyperfluorescent fundus areas colocalize with abnormal SD-OCT reflectance in ONL, which correlate histologically with lesions; established their locality, onset, and progression; and observed retinal neovascularization. This establishes a basis for studies of potential neuroprotective signaling, as well as other retinal degenerative mechanisms.
Keywords: imaging/image analysis: non-clinical • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • photoreceptors