BMP2/ALKs Signaling System in Diabetic Retinopathy

Summary Proliferative diabetic retinopathy is a major cause of vision impairment in diabetic patients due to pathological diabetic macular edema and retinal neovascularization. Our previous research identified bone morphogenetic proteins-2 and -4 (BMP2/4) and their receptors Activin-receptor-Like-Kinases (ALK2 and ALK3) as significant factors in retinal endothelial cell barrier dysfunction associated with diabetic retinopathy and excess fibronectin production. Activation of BMP2/4-ALK in diabetes is associated with activation of both canonical (SMAD) and non-canonical (p38 MAPK) pathways and hyperpermeability in retinal endothelial cells. This study aims to deepen understanding of BMP2/4-ALK signaling in progression of diabetic retinopathy and retinal neovascularization and explore therapeutic interventions by targeting this pathway. Preliminary data showed elevated BMP2/4 expression in retina of oxygen-induced retinopathy and reduced retinal neovascularization upon inhibition of BMP2/4 signaling or targeted deletion of both ALK2 and ALK3 in endothelial cells (ALK2/3eKO). Additionally, retinal levels of βB2 and B3-crystallins (βB2/βB3) were decreased in both diabetic and a mouse model of oxygen-induced retinopathy, a change restored by noggin, an inhibitor of BMP2/4 signaling. βB2/βB3- crystallins were expressed in retinal vessels in humans and mice, with BMP2/4 inducing angiogenesis in human retinal endothelial cells, mitigated by βB2-crystallin. We also observed dysregulation of microRNAs in human retinal endothelial cells by BMP2 treatment, particularly miR-126. This study will test the hypothesis that BMP2/4- ALKs play a significant role in promoting the progression of diabetic retinopathy and retinal neovascularization through dysregulation of βB2/βB3-crystallins, involving miR126 modification. Aim 1 focuses on evaluating the therapeutic potential of inhibiting BMP2/4-ALK signaling in pathological retinal neovascularization. We hypothesize that activated BMP2/4-ALKs contribute to retinal neovascularization development. This aim involves assessing changes in key signaling components and gene transcription in both mice with oxygen-induced retinopathy and in human retinal endothelial cells. Pharmacological inhibition and targeted deletion of endothelial ALK2/3 will be investigated to understand their effects on retinal neovascularization and angiogenesis-related genes. Aim 2 focuses on elucidating the role of βB2/βB3-crystallins in BMP2/4, hyperglycemia or hypoxia- mediated dysfunction in retinal endothelial cells. The roles of βB2/βB3-crystallins in diabetic retinopathy and retinal neovascularization present an unexplored area ripe for investigation. We will validate our proteomic findings that demonstrate downregulation of retinal β-crystallin protein family in streptozotocin-induced diabetic mice, investigating the impact of βB2/βB3-crystallins on retinal endothelial cell dysfunction, assessing changes in signaling components, gene transcription, and protein levels as well as exploring epigenetic mechanisms involved. We will focus particularly on the possible role of miR-126. Through this project, we expect to identify the mechanistic relationship between BMP2/4-ALK- βB2/βB3-crystallins signaling and retinal neovascularization.