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Natalie Hudson, Shervin Liddie, Ema Ozaki, Sarah Doyle, Eleanor Demmons, Akeem Browne, Matthew S Lawrence, Matthew Campbell; Circadian rhythm mediated regulation of the inner blood retina barrier; Relevance for geographic atrophy development.. Invest. Ophthalmol. Vis. Sci. 2019;60(9):2997. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Recently, we have discovered that the inner blood retina barrier (iBRB) is highly dynamic and is regulated by an entrained circadian rhythm. Here, we sought to determine the iBRB integrity in mice and non-human primates and explore the relevance of the inner retina to age-related macular degeneration (AMD).
Fundus fluorescein angiography (FFA) and optical coherence tomography (OCT) was carried out in the morning and evening in both C57BL6/J mice and non-human primates (African green monkeys – Chlorocebus sabaeus) to assess iBRB permeability changes. Sub-retinal injections of adeno-associated virus (AAV) vectors under doxycycline control targeting the iBRB tight junction protein claudin-5, or non-targeting control were carried out to characterize the effect of constant claudin-5 suppression on retinal and retinal pigment epithelium (RPE) integrity. In mice studies, drinking water was supplemented with doxycycline to induce suppression of claudin-5. In non-human primate studies, doxycycline was mixed with a concentrated sweetener and administered via a handheld syringe. RPE integrity was assessed by immunohistochemistry following sacrifice.
The iBRB vasculature has more permeable vessels in the evening compared to morning with increased fluorescein signal in both mice (***P < 0.001) and non-human primates (*P < 0.05). In C57BL6/J mice injected sub-retinally with an AAV targeting claudin-5 we observed striking RPE cell atrophy. In monkeys, FFA analysis showed clear fluorescein extravasation at the site of claudin-5 AAV injection (superior peri-macular) compared to the non-targeting AAV (inferior peri-macular). OCT analysis of the injected sites showed aberrant RPE structure at the site of claudin-5 AAV, but normal laminar structure for the non-targeting AAV injected region. Additionally, over-expression of claudin-5, using a CMV-driven AAV, sub-retinally injected into mice also showed RPE atrophy.
Our results indicate the iBRB is a highly dynamic structure that is tightly regulated by the circadian clock. We have developed a new model of geographic atrophy (GA) whereby prolonged suppression of claudin-5 expression leads to RPE cell atrophy indicating an inner retina derived contribution to GA pathology. These results suggest that re-establishing claudin-5 cycling at the iBRB may represent a novel therapeutic target for GA prevention and treatment.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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