Molecular mechanisms underlying the vascular lesions in proliferative diabetic retinopathy

在糖尿病性视网膜病变中，患者的视敏度由于纤维血管组织的形成以及视网膜水肿而受损。通过对临床标本的分析，我们发现视网膜胶质细胞中血管内皮生长因子（VEGF），尤其是其亚型VEGF_<165>1和膜型基质金属蛋白酶（MT 1-MMP）的表达是导致纤维血管组织形成的重要因素。在这项研究中，这些分子的诱导机制进行了调查，与组织缺氧。分离兔视网膜神经胶质细胞，分别在常氧（20%O_2）和低氧（1%O_2）条件下培养。RT-PCR和实时PCR分析表明，缺氧诱导视网膜胶质细胞MT 1-MMP和VEGF的表达。VEGF<165>在缺氧视网膜胶质细胞中选择性上调。VEGF的一种高亲和力受体VEGFR-2也被发现表达于乳腺癌。 ...更多信息 缺氧时视网膜神经胶质细胞的sse，而在常氧时则可忽略。VEGF-2抑制剂SU 1498或抗VEGF抗体均能抑制缺氧诱导的MT 1-MMP表达，提示缺氧视网膜神经胶质细胞中MT 1-MMP的表达是由VEGF-VEGFR-2系统以自分泌方式介导的。另一方面，通过紧密连接分子claudins的表达，分析了由于血-视网膜屏障的破坏而导致的视网膜水肿形成的机制。首先，显示视网膜血管内皮细胞在其细胞边界表达claudin-5。使用培养的bEND.3内皮细胞，证明了在缺氧条件下，紧密连接蛋白-5在内皮细胞的细胞边界处的定位消失，这与屏障功能的破坏密切相关。MAP激酶级联反应参与了缺氧诱导的claudin-5表达的变化。本研究结果提示组织缺氧可能通过改变VEGF、MT 1-MMP和claudin-5的表达而在纤维血管组织和视网膜水肿的形成中发挥作用<165>。少

In diabetic retinopathy, the visual acuity of patients is impaired by the formation of fibrovascular tissue as well as retinal edema. Through analysis of clinical samples, we had obtained the data to suggest that the fibrovascular tissue formation is attributed to the induction of vascular endothelial growth factor (VEGF), especially its isoform VEGF_<165>, and membrane-type 1 matrix metalloproteinase(MT1-MMP) in retinal glial cells. In this study, the mechanisms underlying the induction of these molecules were investigated, with reference to tissue hypoxia. Retinal glial cells were isolated from the rabbit retina, and cultured under either normoxic(20% O_2) or hypoxic(1% O_2) condition. RT-PCR and real-time PCR analyses showed that hypoxia induces the expression of MT1-MMP and VEGF in retinal glial cells. As concerns VEGF, the isoform VEGF_<165> was selectively up-regulated in hypoxic retinal glial cells. One of the high-affinity receptors for VEGF, VEGFR-2, was also found to be expre … More ssed in retinal glial cells under hypoxia, while negligible in those under normoxia. Furthermore, the hypoxia-induced MT1-MMP expression was inhibited in the presence of the VEGFR-2 inhibitor SU1498 or the anti-VEGF antibody, indicating that the expression of MT1-MMP in hypoxic retinal glial cells is mediated by VEGF-VEGFR-2 system in an autocrine fashion. On the other hand, the mechanisms of retinal edema formation due to the breakdown of blood-retinal barrier were analyzed in reference to the expression of tight junction molecules, claudins. First, retinal vascular endothelial cells were shown to express claudin-5 at their cell borders. Using cultured bEND.3 endothelial cells, it was demonstrated that the localization of claudin-5 at the cell borders of endothelial cells disappears under hypoxic condition with close correlation to the breakdown of barrier function. MAP kinase cascades were involved in the hypoxia-induced changes in claudin-5 expression. The data obtained in this study suggest the role of tissue hypoxia in the formation of fibrovascular tissue and retinal edema through alteration of VEGF_<165>, MT1-MMP and claudin-5 expression. Less