Nonarteritic Anterior Ischemic Optic Neuropathy (NAION)

Summary: NAION-like pathology induction leads to an acute ischemia and to edema, inflammation, and acute loss of retinal ganglion cells (RGCs) and optic nerve axons.

Model Description

Nonarteritic anterior ischemic optic neuropathy (NAION) is an acute ischemic stroke of the optic nerve leading to permanent and irreversible blindness (Berry et al., 2017). In rodents, NAION-like pathology can be induced by damaging the optic nerve head capillaries with an administration of photosensitive dye Rose Bengal and subsequent lasering (Guo et al., 2016). After the lasering, an acute ischemia leads to edema, inflammation and acute loss of retinal ganglion cells (RGCs) and optic nerve axons (Ragauskas et al., 2018). 

The typical follow-up time is 2 weeks both in mice and in rats. The induction is unilateral leaving the contralateral eye as naive control. 

Animal speciesMice, Rats
Method of inductionRose Bengal injection (iv) and lasering of optic nerve head area
Follow-up periodTypically 1-2 weeks
Route of compound administrationTopical (e.g. eye drops), intravitreal injections, systemic (iv, ip), subcutaneous
Read-outs1. In vivo imaging (fluorescein angiography, optical coherence tomography)
2. In vivo functional assessment:
– Electroretinography
3. Morphological assessment:
– Optic nerve axon counts (semi-thin optic nerve sections)
– Routine histology (H&E staining for retinal sections)
– Immunohistochemistry (typically RGC marker/glial marker and counterstain in retinal wholemounts),
– Stereology of RGCs (retinal wholemounts) and optic nerve axons
4. Molecular biology (ELISA, Western blotting, qPCR)

Outcomes and Read-Outs 

In vivo imaging

Experimentica uses state-of-the-art in vivo imaging methodologies, which allow the longitudinal evaluation of pathological changes. 

Fluorescein Angiography and fundus imaging are used to assess retinal ischemia at different timepoints after NAION induction (Heidelberg Spectralis, Heidelberg Engineering). 

Fig. 1. Fundus and fluorescein angiography (FA) imaging of the mouse NAION model.
Fig. 1. Fundus and fluorescein angiography (FA) imaging of the mouse NAION model. Note enlarged ischemic area in fundus images at day 14 post-lasering as compared to day 7 (outlined in red). There is also a dramatic loss of fluorescein-filled retinal vasculature in representative FA images (outlined in red) as compared to the healthy eye FA view. 

SD-OCT imaging provides cross-sectional view of optic nerve head and surrounding retinal tissue (Ragauskas et al., 2018). (Envisu R2210 and Envisu R2210, Bioptigen Inc./Leica Microsystems) 

Fig. 2. SD-OCT of optic nerve head (ONH) and surrounding retinal area at 3 days, 7 days and 14 days after NAION induction in the same mouse eye.
Fig. 2. SD-OCT of optic nerve head (ONH) and surrounding retinal area at 3 days, 7 days and 14 days after NAION induction in the same mouse eye. RGCL = retinal ganglion cell layer, ONL = outer nuclear layer, RPE = retinal pigment epithelium. 

Functional evaluation

Induced ischemia causes the loss of retinal ganglion cells (RGCs). RGCs’ function can be quantitatively measured using pattern electroretinography (pERG). 

Fig. 3. Functional assessment of retinal ganglion cell (RGC) function in pigmented C57Bl/6 mice 10 days after NAION induction.
Fig. 3. Functional assessment of retinal ganglion cell (RGC) function in pigmented C57Bl/6 mice 10 days after NAION induction. There is a significant decrease in pattern electroretinography (pERG) amplitude in NAION eyes as compared to baseline values (n=11) 

Histology/morphometry

Immunohistochemical labeling of RGCs and their quantification can be performed in retinal flatmounts or from serially sectioned eyes. 

Fig. 4. Retinal flatmounts from mice are immunostained with RGC-specific RBPMS (in red) and an astrocyte specific GFAP (in green).
Fig. 4. Retinal flatmounts from mice are immunostained with RGC-specific RBPMS (in red) and an astrocyte-specific GFAP (in green). 

References

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