Neuron-Derived Semaphorin 3A is an Early Inducer of Vascular Permeability in Diabetic Retinopathy

Abstract

Diabetic macular edema (DME), the main cause of central vision loss in diabetics, is a manifestation of diabetic retinopathy (DR) caused by the deterioration of the blood-retinal barrier, which leads to thickening of the ischemic retina through increased retinal vascular permeability (VP). Our lab has shown that Semaphorin 3A (Sema3A), a classic neuronal guidance protein involved in endothelial cell (EC) behaviour, participates in vascular degeneration and later blocks physiological revascularization of the ischemic retina. Given the vaso-modulatory role of Sema3A, we studied the ability of Sema3A to promote increased retinal VP in DR. Human vitreous samples from DR patients showed a robust increase in Sema3A protein, by western blot (Wb) analysis, when compared to vitreous from patients with non-vascular ocular pathology (control). Retinal lysates from streptozotocin (STZ)-treated mice (T1DM model) exhibited significant 2.25- and 2.5-fold increases in Sema3A mRNA levels after 4 and 8 weeks of diabetes, respectively. Retinal VP, quantified by Evans Blue permeation assay, was 2.1-fold higher in mice that had received an intravitreal injection of Sema3A relative to vehicle-injected controls. In addition, confluent EC monolayers treated with rhSema3A showed compromised barrier function (measured by Electric Cell-substrate Impedance Sensing) and induction of phosphorylated Src, FAK and vascular endothelial cadherin (by Wb), which are associated with increased VP. Sema3A is induced in the retinas of diabetic patients and mice in a T1DM model. This increase in Sema3A is associated with increased retinal vascular leakage.