年龄相关性黄斑变性的代谢生理学。

Metabolic physiology in age related macular degeneration.

机构信息

University of Iceland, National University Hospital, 101 Reykjavík, Iceland.

出版信息

Prog Retin Eye Res. 2011 Jan;30(1):72-80. doi: 10.1016/j.preteyeres.2010.09.003. Epub 2010 Oct 15.

Abstract

Ischemia and hypoxia have been implicated in the pathophysiology of age related macular degeneration (AMD). This has mostly been based on studies on choroidal perfusion, which is not the only contributor to retinal hypoxia found in AMD eyes. Other features of AMD may also interfere with retinal oxygen metabolism including confluent drusen, serous or hemorrhagic retinal detachment, retinal edema and vitreoretinal adhesion. Each of these features contributes to retinal hypoxia: the drusen and retinal elevation by increasing the distance between the choriocapillaris and retina; vitreoretinal adhesion by reducing diffusion and convection of oxygen towards and vascular endothelial growth factor (VEGF) away from hypoxic retinal areas. Hypoxia-inducible-factor is known to exist in subretinal neovascularization and hypoxia is the main stimulus for the production of VEGF. Each feature may not by itself create enough hypoxia and VEGF accumulation to stimulate wet AMD, but they may combine to do so. Choroidal ischemia in AMD has been demonstrated by many researchers, using different technologies. Choroidal ischemia obviously decreases oxygen delivery to the outer retina. Confluent drusen, thickening of Bruch's membrane and any detachment of retina or retinal pigment epithelium, increases the distance between the choriocapillaris and the retina and thereby reduces the oxygen flux from the choroid to the outer retina according to Fick's law of diffusion. Retinal elevation and choroidal ischemia may combine forces to reduce choroidal oxygen delivery to the outer retina, produce retinal hypoxia. Hypoxia leads to production of VEGF leading to neovascularization and tissue edema. A vicious cycle may develop, where VEGF production increases effusion, retinal detachment and edema, further increasing hypoxia and VEGF production. Adhesion of the viscous posterior vitreous cortex to the retina maintains a barrier to diffusion and convection currents in the vitreous cavity according to the laws of Fick's, Stokes-Einstein and Hagen-Poiseuille. If the vitreous is detached from the surface of the retina, the low viscosity fluid transports oxygen and nutrients towards an ischemic area of the retina, and cytokines away from the retina, at a faster rate than through attached vitreous gel. Vitreoretinal adhesion can exacerbate retinal hypoxia and accumulation of cytokines, such as VEGF. Vitreoretinal traction can also cause hypoxia by retinal elevation. Conceivably, the basic features of AMD, drusen, choroidal ischemia, and vitreoretinal adhesion are independently determined by genetics and environment and may combine in variable proportions. If the resulting hypoxia and consequent VEGF accumulation crosses a threshold, this will trigger effusion and neovascularization.

摘要

缺血和缺氧与年龄相关性黄斑变性 (AMD) 的病理生理学有关。这主要是基于脉络膜灌注的研究,而脉络膜灌注并不是 AMD 眼中发现的视网膜缺氧的唯一贡献者。AMD 的其他特征也可能干扰视网膜的氧代谢,包括融合性玻璃膜疣、浆液性或出血性视网膜脱离、视网膜水肿和玻璃体视网膜粘连。这些特征中的每一个都导致视网膜缺氧:玻璃膜疣和视网膜抬高通过增加脉络膜毛细血管和视网膜之间的距离;玻璃体视网膜粘连通过减少氧气向缺氧视网膜区域的扩散和对流以及血管内皮生长因子 (VEGF) 的扩散来实现。众所周知,缺氧诱导因子存在于视网膜下新生血管中,缺氧是产生 VEGF 的主要刺激因素。每个特征本身可能不会产生足够的缺氧和 VEGF 积累来刺激湿性 AMD,但它们可能会结合起来。许多研究人员使用不同的技术证明了 AMD 中的脉络膜缺血。脉络膜缺血显然会降低向视网膜外层输送氧气。融合性玻璃膜疣、Bruch 膜增厚和任何视网膜或视网膜色素上皮的脱离都会增加脉络膜毛细血管和视网膜之间的距离,从而根据菲克扩散定律减少脉络膜向视网膜外层的氧气通量。视网膜抬高和脉络膜缺血可能会合力降低脉络膜向视网膜外层输送氧气,导致视网膜缺氧。缺氧导致 VEGF 的产生,从而导致新生血管形成和组织水肿。可能会发展出一个恶性循环,其中 VEGF 的产生增加了渗出、视网膜脱离和水肿,进一步增加了缺氧和 VEGF 的产生。粘性玻璃体后皮质与视网膜的粘连根据菲克、斯托克斯-爱因斯坦和哈根-泊肃叶定律维持玻璃体腔内扩散和对流电流的屏障。如果玻璃体与视网膜表面分离,低粘度液体将氧气和营养物质输送到视网膜缺血区域,并将细胞因子从视网膜输送出去,速度比通过附着的玻璃体凝胶更快。玻璃体视网膜粘连会加剧视网膜缺氧和细胞因子(如 VEGF)的积累。玻璃体视网膜牵引也会通过视网膜抬高引起缺氧。可以想象,AMD 的基本特征,如玻璃膜疣、脉络膜缺血和玻璃体视网膜粘连,是由遗传和环境独立决定的,并且可能以不同的比例组合。如果由此产生的缺氧和随之而来的 VEGF 积累超过一个阈值,这将触发渗出和新生血管形成。

文献AI研究员

20分钟写一篇综述,助力文献阅读效率提升50倍

立即体验

用中文搜PubMed

大模型驱动的PubMed中文搜索引擎

马上搜索