A contemporary concept of the blood-aqueous barrier
A contemporary concept of the blood-aqueous barrier
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DOI：
10.1016/j.preteyeres.2012.10.004
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发表时间：
2013-01-01
影响因子：
17.8
通讯作者：
Freddo, Thomas F.
中科院分区：
文献类型：
--
作者：
Freddo, Thomas F.
本文回顾了近20年来血-水屏障（BAB）概念的演变。经典模型简单地规定虹膜血管和睫状体上皮的紧密连接将血浆蛋白从房水（AH）中排除。它未能调和AH蛋白水平等于血浆中发现的1%的存在。此外，屏障动力学模型假设AH分泌和血浆蛋白进入的过程直接相关。因此，AH蛋白水平的升高只能通过BAB的病理性分解来解释。在过去的20年中，已经表明正常AH中的血浆蛋白完全绕过后房。相反，这些蛋白质从睫状体基质的毛细血管扩散到虹膜基质中，然后进入前房。这就在虹膜基质中产生了一个血浆蛋白库，而不是来自虹膜血管。虹膜后壁上皮的紧密连接阻止了虹膜后壁的扩散。瞳孔置于前透镜囊上形成的单向阀，与AH通过瞳孔的连续向前流动相结合，防止蛋白质回流到后房中。重要的是，在新的范例中，AH的分泌和血浆蛋白进入AM是半独立的事件。这开启了AM蛋白水平在没有BAB分解的情况下增加的可能性。这种新的范式的BAB的临床后果进行了讨论。(C)2012爱思唯尔有限公司保留所有权利。
This review traces the evolution of the concept of the blood aqueous barrier (BAB) during the past 20 years. The Classical model simply stipulated that the tight junctions of the iris vasculature and ciliary epithelium excluded plasma proteins from the aqueous humor (AH). It failed to reconcile the presence of AH protein levels equal to 1% of that found in plasma. Moreover, models of barrier kinetics assumed that the processes of AH secretion and plasma protein entry were directly linked. Thus, elevations of AH protein levels could only be explained by a pathological breakdown of the BAB. Over the last 20 years it has been shown that the plasma proteins in normal AH by-pass the posterior chamber entirely. Instead, these proteins diffuse from the capillaries of ciliary body stroma, into the iris stroma and then into the anterior chamber. This creates a reservoir of plasma-proteins in the iris stroma that is not derived from the iris vessels. This reservoir is prevented from diffusing posteriorly by tight junctions in the posterior iris epithelium. The one-way valve created by the pupil resting on the anterior lens capsule, combined with the continuous, forward flow of AH through the pupil, prevents protein reflux into the posterior chamber. Importantly, in the new paradigm, secretion of AH and the entry of plasma proteins into AM, are semi-independent events. This opens the possibility that AM protein levels could increase in the absence of breakdown of the BAB. Clinical consequences of this new paradigm of the BAB are discussed. (C) 2012 Elsevier Ltd. All rights reserved.