Xia Tina, Rizzolo Lawrence J
Departments of Surgery and Ophthalmology and Visual Science, Yale University School of Medicine, PO Box 208062, New Haven, CT 06520-8062, USA.
Vision Res. 2017 Oct;139:72-81. doi: 10.1016/j.visres.2017.02.006. Epub 2017 Mar 30.
Diabetic retinopathy is a debilitating microvascular complication of diabetes mellitus. A rich literature describes the breakdown of retinal endothelial cells and the inner blood-retinal barrier, but the effects of diabetes on the retinal pigment epithelium (RPE) has received much less attention. RPE lies between the choroid and neurosensory retina to form the outer blood-retinal barrier. RPE's specialized and dynamic barrier functions are crucial for maintaining retinal health. RPE barrier functions include a collection of interrelated structures and activities that regulate the transepithelial movement of solutes, including: diffusion through the paracellular spaces, facilitated diffusion through the cells, active transport, receptor-mediated and bulk phase transcytosis, and metabolic processing of solutes in transit. In the later stages of diabetic retinopathy, the tight junctions that regulate the paracellular space begin to disassemble, but there are earlier effects on the other aspects of RPE barrier function, particularly active transport and metabolic processing. With advanced understanding of RPE-specific barrier functions, and more in vivo-like culture models, the time is ripe for revisiting experiments in the literature to resolve controversies and extend our understanding of how diabetes affects the outer blood-retinal barrier.
糖尿病性视网膜病变是糖尿病一种使人衰弱的微血管并发症。大量文献描述了视网膜内皮细胞和内血视网膜屏障的破坏，但糖尿病对视网膜色素上皮（RPE）的影响却很少受到关注。RPE位于脉络膜和神经感觉视网膜之间，形成外血视网膜屏障。RPE特有的动态屏障功能对于维持视网膜健康至关重要。RPE屏障功能包括一系列相互关联的结构和活动，这些结构和活动调节溶质的跨上皮运动，包括：通过细胞旁间隙的扩散、通过细胞的易化扩散、主动转运、受体介导的和批量相转胞吞作用，以及转运中溶质的代谢处理。在糖尿病性视网膜病变的后期，调节细胞旁间隙的紧密连接开始分解，但对RPE屏障功能的其他方面，特别是主动转运和代谢处理，有更早的影响。随着对RPE特异性屏障功能的深入理解，以及更多类似体内的培养模型，重新审视文献中的实验以解决争议并扩展我们对糖尿病如何影响外血视网膜屏障的理解的时机已经成熟。
