RNA sequencing reveals BMP4 as a basis for the dual-target treatment of diabetic retinopathy.

Background: Diabetic retinopathy (DR), currently considered as a neurovascular disease, has become the major cause of blindness. More and more scholars believe that DR is no longer just a kind of microvascular disease, but accompanied by retinal neurodegenerative changes. Intravitreal injection of anti-vascular endothelial growth factor (VEGF) drugs is a classic treatment for DR; however, anti-VEGF drugs can exacerbate fibrosis and eventually lead to retinal detachment. The aim of this study was to explore the pathogenesis of DR and identified new treatments that can provide dual-target intervention for angiogenesis and fibrosis.

Methods: We explored changes in gene expression in high glucose-induced vascular endothelial cells using RNA sequencing (RNA-seq) technology. We identified bone morphogenetic protein 4 (BMP4) and SMAD family member 9 (SMAD9) among 449 differentially expressed genes from RNA-seq data and confirmed the expression of these two genes in the blood of diabetes patients by RT-PCR and in streptozotocin-induced rat retinas by RT-PCR, immunofluorescence, and western blot. Moreover, considering that DR is a multifactorial and multicellular disease, we used hydrogen peroxide (HO), advanced glycation end products (AGEs), CoCl, 4-hydroxynonenal (4-HNE), and hypoxia to induce three human retinal cell types (Müller, retinal pigment epithelium, and human retinal capillary endothelial cells) to simulate the pathogenesis of DR, and MTT experiment, scratch experiment, Transwell experiment, and lumen formation experiment were used to test whether the model was successfully established. Then, we verified the overexpression of these two genes in the cell models by RT-PCR, immunofluorescence, and western blot. We further tested the effects of BMP4 on retinal cells. We use BMP4 to stimulate retinal cells and observe the effect of BMP4 on retinal cells by MTT experiment, scratch experiment, and RT-PCR.

Results: The results demonstrated that BMP4 and SMAD9 were highly expressed in both in vivo and in vitro models, while BMP4 could significantly upregulate the expression of SMAD9 and promote the expression of VEGF and fibrosis factors.

Conclusions: This study is the first to analyze the mechanism by which high glucose levels affect retinal vascular endothelial cells through RNA transcriptome sequencing and indicates that BMP4 may be a potential target for the dual-target treatment (anti-VEGF and anti-fibrosis) of DR.

Key Messages: • High-glucose effect on vascular endothelial cell was analyzed by RNA-seq. • KEGG analysis revealed enrichment of TGF-beta signaling pathway. • SMAD9 and BMP4 expression was upregulated in all samples. • Dual-target therapy of PDR by antagonizing BMP4.