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Mira Schaupper, Anthony Mukwaya, Anton Lennikov, Zaheer Ali, Lasse Jensen, Neil S Lagali; Regression of hypoxia-induced vessels in zebrafish retina after return to normoxia environment. Invest. Ophthalmol. Vis. Sci. 2017;58(8):595. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Retinal neovascularisation due to pathological angiogenesis and metabolic alteration leads to vision impairment. Here, we investigate the feasibility to study pathological neovascularisation during hypoxia and induced vascular regression after a return to normoxia, in an adult zebrafish model.
Hypoxia-induced retinal neovascularisation was induced in in 6 months old Tg(fli1:EGFP)y1 zebrafish by placement of animals into low oxygen water (10% air-saturation) for up to 9 days. Subsequently animals were returned to normoxic environment (100% air-saturation). Morphological changes in retinal vasculature were investigated at day 3, 6 and 9 of hypoxia and 6 h, 12h, 24h, 48h, 72h and 96h after return to normoxia, including quantitative analysis of capillary density, vessel diameter, sprouts/anastomoses, branching points and tortuosity. Gene expression profiles for zVEGF-Aa and DLL4 (n=4) were evaluated and ZO-1 staining was performed at the same time points.
Animals displayed after significant (p<0.05) decrease in the amount of new sprouts in the retinal vasculature following return to normoxia (time-point: 6h), compared to day 9 hypoxia-treated group. Sprouts continued to regress over time, coupled to regained integrity of endothelial cell intercellular junctions indicated by ZO-1 staining. We found that retinal vessels regress by a unique mechanism; by first pinching off the main capillary at the site of contact, followed by impaired flow leading to vessel collapse and regression. Among genes analyzed by qPCR; zVEGF-Aa and DLL4 were found to be significantly decreased (p>0.001) at 24h and 96h following return to normoxia compared with the continued hypoxia-treatment group.
Return to normoxia initiated phenotypic regression, return of tight junctions, downregulation of sprouting and upregulation of remodeling. Our results demonstrate the involvement of previously uncharacterized mode of vascular regression in adult zebrafish retina, suggesting that this process, important for treatment of diabetic retinopathy and retinopathy of pre-maturity, could be different from previously described vascular regression mechanisms in other ocular and peripheral tissues. Therefore, adult zebrafish retina provides a viable model for studying hypoxia-associated capillary regression and warrants further investigation.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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