AAV-norrin gene therapy rescues retinal defects in mice with Norrie disease and oxygen-induced retinopathy.

Norrin, secreted by retinal Müller cells, activates canonical Wnt signaling via Frizzled-4 and co-receptors. Loss-of-function mutations abolish intraretinal capillary formation in mice. In humans, mutations in NDP, which encodes norrin, cause Norrie disease, characterized by retinal hypovascularization and congenital blindness, and X-linked familial exudative vitreoretinopathy (FEVR), resembling retinopathy of prematurity (ROP). We evaluated adeno-associated viral (AAV) vectors expressing norrin as gene therapy for Norrie disease, FEVR, and ROP. AAV2-7m8 and AAV-ShH10 were tested in juvenile wild-type and norrin-deficient (Ndp KO) mice via intravitreal injection at postnatal day 7, with some mice subjected to oxygen-induced retinopathy (OIR). AAV2-7m8 transduced Müller glia, while AAV-ShH10 targeted retinal ganglion cells. Both vectors fully restored intraretinal capillary growth in Ndp KO mice, normalizing vessel density and plexus organization, preserving the blood-retinal barrier, and rescuing visual function. In OIR, scAAV2-7m8-huNorrin reduced vaso-obliteration and neovascular tuft formation, increasing deep plexus coverage, and suppressed Vegfa164 and Ang-2 upregulation. The findings demonstrate that AAV-mediated norrin delivery efficiently targets retinal glia and neurons, restores vascular structure and function, stabilizes the blood-retinal barrier, and mitigates OIR-induced pathological angiogenesis, supporting its potential as a therapeutic strategy for Norrie-related retinopathies and ROP.