Glutamatergic neuronal activity regulates retinal angiogenesis and blood-retinal barrier via Norrin/b-catenin signaling
Interactions among neuroglial and vascular components are crucial for retinal angiogenesis and blood-retinal barrier (BRB) maturation. Neuronal synaptic dysfunctions precede vascular abnormalities in many retinal pathologies. However, whether neuronal activity, specifically glutamatergic activity, regulates retinal angiogenesis and BRB maturation remains unclear. Using in vivo genetic studies in mice, single-cell RNA-sequencing and functional validation, we found that deep plexus angiogenesis and paracellular BRB maturation are delayed in Vglut1-/- retinas, where neurons fail to release glutamate. In contrast, deep plexus angiogenesis and paracellular BRB maturation are accelerated in Gnat1-/- retinas, where constitutively depolarized rods release excess glutamate. Mechanistically, Norrin expression and endothelial Norrin/b-catenin signaling are downregulated in Vglut1-/- retinas, and upregulated in Gnat1-/- retinas. Pharmacological activation of endothelial Norrin/ b-catenin signaling in Vglut1-/- retinas rescued both deep plexus angiogenesis and paracellular BRB integrity. Thus, our findings demonstrate that glutamatergic neuronal activity regulates retinal angiogenesis and BRB maturation by modulating Norrin/b-catenin signaling. Overall design: Retina was isolated from P10 wild-type and Vglut-/- mice in the C57BL/6J background. Following single cell dissociation of the retinal tissue, endothelial cells were labeled with CD31-APC antibody and FACS for single cell RNA sequencing analysis.