In Vivo Vascular Injury Readouts in Mouse Retina to Promote Reproducibility
Summary
Here, we present three data analysis protocols for fluorescein angiography (FA) and optical coherence tomography (OCT) images in the study of Retinal Vein Occlusion (RVO).
Abstract
Advancements in ophthalmic imaging tools offer an unprecedented level of access to researchers working with animal models of neurovascular injury. To properly leverage this greater translatability, there is a need to devise reproducible methods of drawing quantitative data from these images. Optical coherence tomography (OCT) imaging can resolve retinal histology at micrometer resolution and reveal functional differences in vascular blood flow. Here, we delineate noninvasive vascular readouts that we use to characterize pathological damage post vascular insult in an optimized mouse model of retinal vein occlusion (RVO). These readouts include live imaging analysis of retinal morphology, disorganization of retinal inner layers (DRIL) measure of capillary ischemia, and fluorescein angiography measures of retinal edema and vascular density. These techniques correspond directly to those used to examine patients with retinal disease in the clinic. Standardizing these methods enables direct and reproducible comparison of animal models with clinical phenotypes of ophthalmic disease, increasing the translational power of vascular injury models.
Introduction
Neurovascular disease is a major healthcare problem responsible for ischemic strokes, a leading cause of mortality and morbidity, and retinal vascular diseases that lead to vision loss1,2. To model neurovascular disease, we employ a mouse model of retinal vein occlusion (RVO). This model is noninvasive and utilizes similar in vivo imaging techniques to those used to examine people with retinal vascular disease in a clinical setting. The use of this model thus increases the translational potential of studies utilizing this model. As with all mouse models, it is critical to maximize reproducibility of the model.
Retinal vascular diseases are a major cause of vision loss in people under the age of 70. RVO is the second most common retinal vascular disease after diabetic retinopathy3. Clinical features characteristic of RVO include ischemic injury, retinal edema, and vision loss as a consequence of neuronal loss3,4. Mouse models of RVO using laser photocoagulation of major vessels have been developed and refined to replicate key clinical pathologies observed in human RVO5,6,7. Advancements in ophthalmic imaging also allow for replication of noninvasive diagnostic tools used in humans, namely, fluorescein angiography (FA) and optical coherence tomography (OCT)6. Fluorescein Angiography allows for the observation of leakage due to the breakdown of the blood-retinal barrier (BRB) as well as blood flow dynamics in the retina, including sites of occlusion, using the injection of fluorescein, a small fluorescent dye8,9. OCT imaging allows for the acquisition of high-resolution cross-sectional images of the retina and the study of the thickness and organization of retinal layers10. Analysis of FA images has historically been largely qualitative, which limits the potential for direct and reproducible comparison between studies. Recently, a number of methods have been developed for the quantification of layer thickness in OCT imaging, though there is currently no standardized analysis protocol and the site of OCT image acquisition varies11. In order to properly leverage these tools, standardized, quantitative, and replicable data analysis methodology are needed. In this paper, we present three such vascular readouts used to evaluate pathological damage in a mouse model of RVO-fluorescein leakage, OCT layer thickness, and disorganization of retinal layers.
Protocol
Representative Results
Discussion
Noninvasive rodent retinal imaging presents an avenue to study pathology and develop interventions. Previous studies have developed and optimized a mouse model of RVO, limiting variability and allowing for reliable translation of common clinical pathologies in the murine retina5,7,13. Developments in ophthalmic imaging technology further allow for the use of clinical in vivo imaging techniques such as FA and OCT in expe…
Divulgazioni
The authors have nothing to disclose.
Acknowledgements
This work was supported by the National Science Foundation Graduate Research Fellowship Program (NSF-GRFP) grant DGE – 1644869(to CKCO), the National Eye Institute (NEI) 5T32EY013933 (to AMP), the National Institute of Neurological Disorders and Stroke (RO1 NS081333, R03 NS099920 to CMT), and the Department of Defense Army/Air Force (DURIP to CMT).
Materials
| AK-Fluor 10% | Akorn | NDC: 17478-253-10 | light-sensitive |
| Carprofen | Rimadyl | NADA #141-199 | keep at 4 °C |
| GenTeal | Alcon | 00658 06401 | |
| Image J | NIH | ||
| InSight 2D | Phoenix Technology Group | OCT analysis software | |
| Ketamine Hydrochloride | Henry Schein | NDC: 11695-0702-1 | |
| Phenylephrine | Akorn | NDCL174478-201-15 | |
| Phoenix Micron IV | Phoenix Technology Group | Retinal imaging microscope | |
| Phoenix Micron Meridian Module | Phoenix Technology Group | Laser photocoagulator software | |
| Phoenix Micron Optical Coherence Tomography Module | Phoenix Technology Group | OCT imaging software | |
| Phoenix Micron StreamPix Module | Phoenix Technology Group | Fundus imaging and acquisition targeting | |
| Photoshop | Adobe | ||
| Refresh | Allergan | 94170 | |
| Tropicamide | Akorn | NDC: 174478-102-12 | |
| Xylazine | Akorn | NDCL 59399-110-20 |
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