Following an oxygen-induced retinopathy Wnt/β-catenin signaling in microvascular endothelial and Müller cells is essential for vascular repair.

Abstract

Purpose : There is evidence that active Wnt/β-catenin signaling, which can be induced by several distinct signaling molecules including norrin, is essential for normal retinal vascular development. Here we investigated if endogenous Wnt/β-catenin signaling in microvascular endothelial or Müller cells is involved in vascular repair after induction of oxygen-induced retinopathy (OIR), the model of retinopathy of prematurity in mice.

Methods : Mice with an inducible and conditional β-catenin deficiency in microvascular endothelial (Cdh5^CreERT/Ctnnb^fl/fl) or Müller cells (Slc1a3^CreERT/Ctnnb^fl/fl) were generated. For induction of an OIR mice were incubated in 75% oxygen from postnatal day (P) 7 for 5 days and returned back to room air at P12. To analyze vascular changes, mice were perfused with FITC-coupled dextran and retinal whole mounts were isolated. In addition, mRNA expression of VEGF, IGF-1 and angiopoietin-2 in retina from Slc1a3^CreERT/Ctnnb^fl/fl mice was analyzed.

Results : At P17 and 5 days after induction of OIR, the vaso-obliterated area was approximately 80% and 60% larger in mice with β-catenin deficiency in microvascular endothelial or Müller cells, respectively, when compared with Cre-recombinase negative Ctnnb^fl/fl littermates that were used as controls. In addition, the area that was covered by intraretinal vessels was significantly smaller by more than 30% in Cdh5^CreERT/Ctnnb^fl/fl and 20% in Slc1a3^CreERT/Ctnnb^fl/fl mice when compared with controls. Further on, in Slc1a3^CreERT/Ctnnb^fl/fl mice the formation of preretinal tufts was increased by 2.6-fold compared to control. In contrast, in Cdh5^CreERT/Ctnnb^fl/fl mice the number of tufts was reduced by 25% compared to controls. Moreover, following an OIR at P15, in Slc1a3^CreERT/Ctnnb^fl/fl mice retinal mRNA level for IGF-1 and angiopoietin-2 were significantly reduced while that of VEGF was unchanged when compared to littermate controls.

Conclusions : In summary, our results clearly indicate that Wnt/β-catenin signaling in microvascular endothelial and Müller cells augments vascular repair following an OIR. In mice with a β-catenin deficiency in Müller cells the effects are most likely mediated via a decreased expression of angiogenic factors such as IGF-1 and angiopoietin-2.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.