Longitudinal In Vivo Imaging of Retinal Ganglion Cells and Retinal Thickness Changes Following Optic Nerve Injury in Mice

Abstract

BackgroundRetinal ganglion cells (RGCs) die in sight-threatening eye diseases. Imaging RGCs in humans is not currently possible and proof of principle in experimental models is fundamental for future development. Our objective was to quantify RGC density and retinal thickness following optic nerve transection in transgenic mice expressing cyan fluorescent protein (CFP) under control of the Thy1 promoter, expressed by RGCs and other neurons.Methodology/Principal FindingsA modified confocal scanning laser ophthalmoscopy (CSLO)/spectral-domain optical coherence tomography (SD-OCT) camera was used to image and quantify CFP+ cells in mice from the B6.Cg-Tg(Thy1-CFP)23Jrs/J line. SD-OCT circle (1 B-scan), raster (37 B-scans) and radial (24 B-scans) scans of the retina were also obtained. CSLO was performed at baseline (n = 11) and 3 (n = 11), 5 (n = 4), 7 (n = 10), 10 (n = 6), 14 (n = 7) and 21 (n = 5) days post-transection, while SD-OCT was performed at baseline and 7, 14 and 35 days (n = 9) post-transection. Longitudinal change in CFP+ cell density and retinal thickness were computed. Compared to baseline, the mean (SD) percentage CFP+ cells remaining at 3, 5, 7, 10, 14 and 21 days post-transection was 86 (9)%, 63 (11)%, 45 (11)%, 31 (9)%, 20 (9)% and 8 (4)%, respectively. Compared to baseline, the mean (SD) retinal thickness at 7 days post-transection was 97 (3)%, 98 (2)% and 97 (4)% for the circle, raster and radial scans, respectively. The corresponding figures at 14 and 35 days post-transection were 96 (3)%, 97 (2)% and 95 (3)%; and 93 (3)%, 94 (3)% and 92 (3)%.Conclusions/SignificanceLongitudinal imaging showed an exponential decline in CFP+ cell density and a small (≤8%) reduction in SD-OCT measured retinal thickness post-transection. SD-OCT is a promising tool for detecting structural changes in experimental optic neuropathy. These results represent an important step towards translation for clinical use.

Topical Treatment With Bromfenac Reduces Retinal Gliosis and Inflammation After Optic Nerve Crush

“…This is of special importance in the central retina because in clinical practice, RFNL measurement is employed as an index of RGC loss. Our group and others 22,[58][59][60][61] have shown in animal models that following axotomy of the optic nerve or ocular hypertension there is a 9-day time lapse mismatch between the onset of RGC disappearance and the slower, more protracted, degeneration of the intraretinal axons, which form the RFNL. 22 It is tempting to suggest that such a time delay could be influenced by a RFNL swollen by the astrocyte and Müller cell hypertrophy that occurs upon lesion.…”

Traumatic Optic Neuropathy: A Review

“…40,41 Several studies have employed optical coherence tomography (OCT) to document thinning of the retinal nerve fiber layer (RNFL) following trauma to the ON. [42][43][44] It takes time for this thinning to occur, and in the acute trauma scenario it may not be possible to sit the patient up to perform the OCT, reducing its utility in diagnosis. However, it may be useful for documenting the progression of damage over time and can be employed as part of the long-term follow-up after the injury.…”

Assessing retinal ganglion cell damage

“…These mice have been used for studies of acute injury to RGCs, including optic nerve transection (Figure 3), 45 optic nerve crush, 46 N-methyl-Daspartate (NMDA) receptor induced excitotoxicity, 47 and retinal ischemia induced by increased intraocular pressure. 48,49 In all of these studies, longitudinal imaging was performed in vivo and there was demonstration of quantifiable RGC loss as a result of the injury.…”