Department of Bioengineering, University of California, Riverside, CA, USA.
Division of Neuroscience, Oregon National Primate Research Center, Oregon Health and Sciences University, Beaverton, OR, USA.
J Pathol. 2022 Jul;257(3):314-326. doi: 10.1002/path.5892. Epub 2022 Apr 8.
Age-related macular degeneration (AMD) is the leading cause of blindness in the aging population. Yet no therapies exist for ~85% of all AMD patients who have the dry form that is marked by degeneration of the retinal pigmented epithelium (RPE) and underlying choroidal vasculature. As the choroidal vessels are crucial for RPE development and maintenance, understanding how they degenerate may lead to effective therapies for dry AMD. One likely causative factor for choroidal vascular loss is the cytolytic membrane attack complex (MAC) of the complement pathway that is abundant on choroidal vessels of humans with early dry AMD. To examine this possibility, we studied the effect of complement activation on choroidal endothelial cells (ECs) isolated from a rhesus monkey model of early AMD that, we report, exhibits MAC deposition and choriocapillaris endothelial loss similar to that seen in human early AMD. Treatment of choroidal ECs from AMD eyes with complement-competent normal human serum caused extensive actin cytoskeletal injury that was significantly less pronounced in choroidal ECs from young normal monkey eyes. We further show that ECs from AMD eyes are significantly stiffer than their younger counterparts and exhibit peripheral actin organization that is distinct from the longitudinal stress fibers in young ECs. Finally, these differences in complement susceptibility and mechanostructural properties were found to be regulated by the differential activity of the small GTPases Rac and Rho, because Rac inhibition in AMD cells led to simultaneous reduction in stiffness and complement susceptibility, while Rho inhibition in young cells exacerbated complement injury. Thus, by identifying cell stiffness and cytoskeletal regulators Rac and Rho as important determinants of complement susceptibility, the current findings offer a new mechanistic insight into choroidal vascular loss in early AMD that warrants further investigation for assessment of translational potential. © 2022 The Pathological Society of Great Britain and Ireland.
年龄相关性黄斑变性（AMD）是导致老年人群失明的主要原因。然而，对于所有患有干性 AMD 的患者，约 85%的患者没有有效的治疗方法，干性 AMD 的特征是视网膜色素上皮（RPE）和脉络膜血管的变性。由于脉络膜血管对 RPE 的发育和维持至关重要，因此了解它们如何变性可能会为干性 AMD 的有效治疗方法提供线索。脉络膜血管丧失的一个可能的致病因素是补体途径中的细胞毒性膜攻击复合物（MAC），它在患有早期干性 AMD 的人类脉络膜血管中大量存在。为了研究这种可能性，我们研究了补体激活对从早期 AMD 恒河猴模型中分离出的脉络膜内皮细胞（EC）的影响，我们报告称，该模型显示出 MAC 沉积和脉络膜毛细血管内皮细胞丢失，类似于人类早期 AMD 所见。用补体功能正常的正常人血清处理 AMD 眼的脉络膜 EC 会引起广泛的肌动蛋白细胞骨架损伤，而在来自年轻正常猴眼的脉络膜 EC 中，这种损伤明显较轻。我们进一步表明，AMD 眼的 EC 比年轻的 EC 更硬，并且表现出与年轻 EC 中的纵向应激纤维不同的周围肌动蛋白组织。最后，发现 AMD 细胞中 Rac 和 Rho 的小 GTPase 活性差异调节了补体敏感性和力学结构特性的差异，因为在 AMD 细胞中抑制 Rac 会导致细胞硬度和补体敏感性同时降低，而在年轻细胞中抑制 Rho 会加剧补体损伤。因此，通过鉴定细胞硬度和肌动蛋白细胞骨架调节剂 Rac 和 Rho 作为补体敏感性的重要决定因素，目前的研究结果为早期 AMD 中脉络膜血管丢失提供了新的机制见解，值得进一步研究以评估其转化潜力。 ©2022 大不列颠及爱尔兰病理学学会。
