Diabetes promotes retinal vascular endothelial cell injury through inducing CCN1 expression

PURPOSE: Diabetic retinopathy (DR) is one of the most common diabetic microvascular complications. However, the pathogenesis of DR is not thoroughly illustrated yet. This study aimed to discover novel and key molecules involved in DR pathogenesis, which could potentially be therapeutic targets for DR intervention.METHODS: To find clues of genes that involved in the pathogenesis of DR, we analyzed the public database of neovascular membranes (NVMs) from patients with proliferative diabetic retinopathy (PDR) and healthy controls (GSE102485). Further, we compared these findings by performing RNA-sequencing analysis of peripheral blood mononuclear cells (PBMC) from DR, non-complicated diabetes mellitus control patient (DMC) and healthy controls (HC). To reveal the critical role of candidate genes in DR, knocking-down or knock-out was performed in human retinal vascular endothelial cells (HRVECs), and the oxidative stress pathway, as well as tight junction integrity, were analyzed.RESULTS: The transcriptional profiles showed a distinct pattern in the NVMs of DR patients from those of the healthy controls. Those genes enriched in either ECM-receptor interaction or focal adhesion pathways were up-regulated prominently. Both pathways were important for maintaining the integrity of retinal vascular structure and function. Importantly, the matricellular protein CCN1, a key gene in cell physiology, was differentially expressed in both two pathways. Knocking-down of CCN1 by siRNA or knock-out of CCN1 by CRISPR-Cas9 technique in HRVECs significantly increased the protein level of VE-Cadherin, reduced the protein level of NADPH oxidase 4 (NOX4), and inhibited the levels of reactive oxygen species (ROS), respectively.CONCLUSION: Our study identifies CCN1 as an important regulator in the pathogenesis of DR. The increased expression of CCN1 stimulates oxidative stress and destroys tight junction integrity in endothelial cells through inducing NOX4. Thus, targeting the CCN1/NOX4 axis provides a therapeutic strategy for treating DR through alleviating the endothelial cell injury.