Abstract
Purpose :
Central Retinal Artery Occlusion (CRAO) can lead to partial loss of vision or even blindness, with no clinically proven treatment. Surgical ligation of the CRA is only feasible in large animals but not rodents and middle cerebral artery occlusion (MCAO) causes significant hemiparalysis. This study evaluates an alternative procedure that uses ligation of the external carotid (ECA), pterygopalatine (PPA), superior thyroid (STA) arteries, called EPS, for its potential use in preclinical interventional studies in mice.
Methods :
The internal carotid artery and ECA are exposed, and the ECA and STA permanently ligated in anesthetized mice. The PPA is reversibly ligated and released at varying intervals. The impact of intravitreal (IVT) injection, a potential route for therapeutic intervention, was assessed using vehicle injected before occlusion or after reperfusion in a masked design. Blood flow was assessed using fundus imaging (Micron II; Phoenix Research Laboratories, Inc.) and apoptosis by immunohistochemistry (ApopTag, Millipore/Sigma). Retinal sections were imaged and the level of apoptosis in the ganglion cell layer (GCL) quantitated using the “find nuclei” algorithm in FIJI/ImageJ or manually by masked observers.
Results :
Occlusion and reperfusion can be completed in 30-60 and 10-20 minutes, respectively. Of 60 procedures, adverse complications included death during (n=3) or after (n=2) surgery, mild head tilt (n=2), and major anatomical deviation (n=1), the latter two did not alter outcomes. Occluded retinal blood flow could be visualized, but was often obscured by transient lens clouding. Apoptosis was detected in all retinal layers, with the level dependent on occlusion duration. In the GCL, a 3-hour occlusion resulted in 12.5% ± 6.3 apoptosis (n=3) compared to 1.2% ± 0.9 and 0.4% ± 0.4 for 1- or 2-hour occlusions (n=3 each), respectively. Ongoing, masked analysis of potential damage from IVT injection will be presented.
Conclusions :
The EPS procedure effectively models CRAO with retinal apoptosis after a 3-hour occlusion, and minimal adverse effects compared to significant hemiparalysis seen in MCAO. Cell death is most likely caused by the extended period of retinal blood flow loss, and not reperfusion. The ability to modulate the level of apoptosis by the occlusion duration and potentially with therapeutic interventions, combined with the mild complications makes EPS a versatile model for translational trials.
This is a 2020 ARVO Annual Meeting abstract.