Department of Oral Biology/Anatomy College of Dental Medicine, Georgia Reagents University (Augusta) (GRU(A)), USA; Vision Discovery Institute, Medical College of Georgia, GRU(A), USA; Oral and Dental Research Division, Department of Surgery and Medicine, National Research Center, Egypt.
Department of Oral Biology/Anatomy College of Dental Medicine, Georgia Reagents University (Augusta) (GRU(A)), USA; Vision Discovery Institute, Medical College of Georgia, GRU(A), USA.
Exp Eye Res. 2014 Aug;125:79-88. doi: 10.1016/j.exer.2014.05.012. Epub 2014 Jun 6.
Diabetic retinopathy (DR) is one of the most common complications of diabetes mellitus. Vision loss in DR principally occurs due to breakdown of the blood-retinal barrier (BRB), leading to macular edema, retinal detachment and inner retinal and vitreous hemorrhage. Several growth factors have been shown to play crucial role in the development of these vascular changes; however, the cellular and molecular mechanisms of DR are not yet fully revealed. In the current study we investigated the role of bone morphogenetic protein-2 (BMP2) in DR. We examined the changes in the protein levels of BMP2 in human vitreous and retina in addition to the mouse retina of streptozotocin-induced diabetes. To detect the source of BMP2 during diabetes, human retinal endothelial cells (hRECs) were subjected to high glucose (HG) for 5 days and levels of BMP2 protein were analyzed in conditioned media of these cells relative to control. We also evaluated the effect of BMP2 on the levels of VEGF in cultured rat Müller cells (rMC1). In addition, we tested the pro-inflammatory effects of BMP2 by examining its effect on leukocyte adhesion to cultured hRECs, and levels of adhesion molecules and cytokines production. Finally, the effect of different concentrations of BMP2 on permeability of confluent monolayer of hRECs was evaluated using FITC-Dextran flux permeability assay and by measuring Transcellular Electrical Resistance (TER) using Electric Cell-substrate Impedance Sensing (ECIS). Our results show, for the first time, the up-regulation of BMP2 in diabetic human and mouse retinas in addition to its detection in vitreous of patients with proliferative DR (72 ± 7 pg/ml). In vitro, hRECs showed upregulation of BMP2 in HG conditions suggesting that these cells are a potential source of BMP2 in diabetic conditions. Furthermore, BMP2 induced VEGF secretion by Müller cells in-vitro; and showed a dose response in increasing permeability of cultured hRECs. Meanwhile, BMP2 pro-inflammatory effects were recognized by its ability to induce leukocyte adhesion to the hRECs, intercellular adhesion molecule-1 (ICAM-1) and upregulation of interleukin-6 and 8 (IL-6 and IL-8). These results show that BMP2 could be a contributing growth factor to the development of microvascular dysfunction during DR via enhancing both pro-angiogenic and inflammatory pathways. Our findings suggest BMP2 as a potential therapeutic target to prevent/treat DR.
糖尿病性视网膜病变(DR)是糖尿病最常见的并发症之一。DR 导致的视力丧失主要是由于血视网膜屏障(BRB)的破坏,导致黄斑水肿、视网膜脱离以及内视网膜和玻璃体积血。已经有几种生长因子被证明在这些血管变化的发展中起关键作用;然而,DR 的细胞和分子机制尚未完全揭示。在本研究中,我们研究了骨形态发生蛋白 2(BMP2)在 DR 中的作用。我们检查了人玻璃体和视网膜中 BMP2 蛋白水平的变化,以及链脲佐菌素诱导的糖尿病小鼠视网膜中的变化。为了在糖尿病期间检测 BMP2 的来源,将人视网膜内皮细胞(hRECs)置于高葡萄糖(HG)中 5 天,并相对于对照分析这些细胞条件培养基中 BMP2 蛋白的水平。我们还评估了 BMP2 对培养的大鼠 Müller 细胞(rMC1)中 VEGF 水平的影响。此外,我们通过检查白细胞黏附到培养的 hRECs 的水平以及黏附分子和细胞因子产生的水平,测试了 BMP2 的促炎作用。最后,通过使用 FITC-葡聚糖通量渗透率测定法评估不同浓度的 BMP2 对共培养 hRECs 单层通透性的影响,并使用细胞-基底阻抗传感(ECIS)测量跨细胞电阻(TER)。我们的结果首次显示,除了在糖尿病患者的玻璃体中检测到 BMP2 之外,在糖尿病人和小鼠的视网膜中也上调了 BMP2。在体外,hRECs 在 HG 条件下显示出 BMP2 的上调,这表明这些细胞是糖尿病条件下 BMP2 的潜在来源。此外,BMP2 诱导 Müller 细胞体外分泌 VEGF;并表现出增加培养的 hRECs 通透性的剂量反应。同时,BMP2 通过诱导白细胞黏附到 hRECs、细胞间黏附分子-1(ICAM-1)和上调白细胞介素-6 和 8(IL-6 和 IL-8)来发挥其促炎作用。这些结果表明,BMP2 可以通过增强促血管生成和炎症途径,成为 DR 中小血管功能障碍发展的一个促生长因子。我们的研究结果表明,BMP2 可以作为一种潜在的治疗靶点,以预防/治疗 DR。