Fig. 3.

The neurovascular units (NVU) and Scg3 in healthy and diabetic retina. The NVU is composed of retinal neurons (e.g., retinal ganglion, bipolar, horizontal amacrine cells), glial cells (e.g. Müller cells, astrocytes and microglia) and vascular cells (e.g., ECs and pericytes). a. The NVU in healthy retina. Scg3 is secreted via neurotransmitter vesicles, but its receptor is not expressed on healthy endothelium. b. The NVU in diabetic retina. Both Scg3 and VEGF stimulates retinal leakage and retinal neovascularization but by different mechanisms. Secreted Scg3 is expressed at the similar levels in the diabetic and healthy retina and binds to its receptor, which is present only on diabetic endothelia, to selectively promote angiogenesis and vascular leakage. In contrast, VEGF is markedly induced in the diabetic retina and binds its receptors that are minimally upregulated on diabetic endothelia