Choroidal congestion mouse model: Could it serve as a pachychoroid model?

Pachychoroid spectrum diseases have been described as a new clinical entity within the spectrum of macular disorders. "Pachychoroid" is defined as choroidal thickening associated with dilated outer choroidal vessels often showing retinal pigment epithelium (RPE) degeneration. Although various clinical studies on the pachychoroid spectrum diseases have been conducted, the pathophysiology of pachychoroid has yet to be fully elucidated. In this study, we attempted to establish a mouse model of pachychoroid. We sutured vortex veins in eyes of wild type mice to imitate the vortex vein congestion in pachychoroid spectrum diseases. Fundus photography and ultra-widefield indocyanine green angiography showed dilated vortex veins from the posterior pole to the ampulla in eyes after induction of choroidal congestion. Optical coherence tomography and tissue sections presented choroidal thickening with dilatation of choroidal vessels. The RPE-choroid/retina thickness ratios on the tissue sections in the treated day 1 and day 7 groups were significantly greater than that in the control group (0.19±0.03 and 0.16±0.01 vs. 0.12±0.02, P<0.05 each). Moreover, immunohistochemistry using RPE flatmount revealed focal RPE degeneration in the treated eyes. Furthermore, inflammatory response-related genes were upregulated in eyes with choroidal congestion induction, and macrophages migrated into the thickened choroid. These results indicated that vortex vein congestion triggered some pachychoroid features. Thus, we have established a choroidal congestion mouse model by suturing vortex veins, which would potentially be useful for investigating the pathophysiology of pachychoroid spectrum diseases.