Chung Sook Hyun, Sin Tzu-Ni, Ngo Taylor, Yiu Glenn
Department of Ophthalmology and Vision Science, University of California, Davis, Sacramento, CA, United States.
Front Genome Ed. 2020 Dec 22;2:594984. doi: 10.3389/fgeed.2020.594984. eCollection 2020.
Among genome engineering tools, Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)-based approaches have been widely adopted for translational studies due to their robustness, precision, and ease of use. When delivered to diseased tissues with a viral vector such as adeno-associated virus, direct genome editing can be efficiently achieved to treat different ophthalmic conditions. While CRISPR has been actively explored as a strategy for treating inherited retinal diseases, with the first human trial recently initiated, its applications for complex, multifactorial conditions such as ocular angiogenesis has been relatively limited. Currently, neovascular retinal diseases such as retinopathy of prematurity, proliferative diabetic retinopathy, and neovascular age-related macular degeneration, which together constitute the majority of blindness in developed countries, are managed with frequent and costly injections of anti-vascular endothelial growth factor (anti-VEGF) agents that are short-lived and burdensome for patients. By contrast, CRISPR technology has the potential to suppress angiogenesis , with the added benefit of targeting intracellular signals or regulatory elements, cell-specific delivery, and multiplexing to disrupt different pro-angiogenic factors simultaneously. However, the prospect of permanently suppressing physiologic pathways, the unpredictability of gene editing efficacy, and concerns for off-target effects have limited enthusiasm for these approaches. Here, we review the evolution of gene therapy and advances in adapting CRISPR platforms to suppress retinal angiogenesis. We discuss different Cas9 orthologs, delivery strategies, and different genomic targets including VEGF, VEGF receptor, and HIF-1α, as well as the advantages and disadvantages of genome editing vs. conventional gene therapies for multifactorial disease processes as compared to inherited monogenic retinal disorders. Lastly, we describe barriers that must be overcome to enable effective adoption of CRISPR-based strategies for the management of ocular angiogenesis.
在基因组工程工具中，基于成簇规律间隔短回文重复序列（CRISPR）的方法因其强大、精准且易于使用的特点，已被广泛应用于转化研究。当通过腺相关病毒等病毒载体递送至患病组织时，可有效实现直接基因组编辑，以治疗不同的眼科疾病。虽然CRISPR作为治疗遗传性视网膜疾病的策略已得到积极探索，且最近已启动首例人体试验，但其在诸如眼部血管生成等复杂多因素疾病中的应用相对有限。目前，诸如早产儿视网膜病变、增殖性糖尿病视网膜病变和新生血管性年龄相关性黄斑变性等新生血管性视网膜疾病，共同构成了发达国家大多数失明病例的病因，这些疾病通过频繁且昂贵地注射抗血管内皮生长因子（anti-VEGF）药物来治疗，而这些药物作用时间短，给患者带来沉重负担。相比之下，CRISPR技术有潜力抑制血管生成，其额外优势在于能够靶向细胞内信号或调控元件、进行细胞特异性递送以及多重编辑以同时破坏不同的促血管生成因子。然而，永久抑制生理途径的前景、基因编辑疗效的不可预测性以及对脱靶效应的担忧，限制了人们对这些方法的热情。在此，我们回顾了基因治疗的发展历程以及在调整CRISPR平台以抑制视网膜血管生成方面取得的进展。我们讨论了不同的Cas9直系同源物、递送策略以及包括VEGF、VEGF受体和HIF-1α在内的不同基因组靶点，还比较了与遗传性单基因视网膜疾病相比，基因组编辑在多因素疾病过程中相对于传统基因治疗的优缺点。最后，我们描述了为有效采用基于CRISPR的策略来管理眼部血管生成而必须克服的障碍。
