New genetic therapy approaches for inherited retinal diseases

遗传性视网膜疾病，包括视网膜色素变性和Leber先天性视神经病变（LHON），是发达国家年轻人群中无法治愈的失明的主要原因。它们是由基因突变引起的，导致视网膜中对视力很重要的细胞过早丧失。在视网膜色素变性中，称为光感受器的光检测细胞丢失，但其他视网膜细胞如将脉冲传递到大脑的神经节细胞保持完整。在LHON中，线粒体基因的突变首先影响神经节细胞，因此来自视网膜的信号无法发送到大脑。在研究开发这些疾病的基因治疗方面取得了重大进展，我们现在有一种批准的基因治疗方法Luxturna，用于治疗由特定基因突变引起的一种疾病。基因治疗的目的是用健康的拷贝取代突变的基因。然而，对于许多患者来说，突变是未知的，对于那些晚期出现的患者，其中光感受器已经丢失，基因替代可能是不可能的。在这些患者中，光遗传学疗法是一种非常有前途的策略，其中光敏蛋白在视网膜的存活细胞（包括神经节细胞）中表达，使它们能够检测光并恢复视力。然而，迄今为止尚未实现用基因疗法有效靶向这些细胞。此外，由于神经节细胞中的线粒体在LHON中受到影响，如果我们能够将健康的基因传递给这些细胞，特别是线粒体，那么就有可能减缓神经节细胞变性和相关的视力丧失。在这个项目中，我们的目标是开发一种使用机器人的外科手术，以更有效地为视网膜神经节细胞提供基因治疗。该手术将涉及机器人辅助的直接注入动物模型中的视神经，这是目前不可能在患者中手动执行的。在实现这一目标后，我们的目标是开发这种技术的应用，包括光遗传学应用和在未来的人类临床试验中治疗视神经病变。最后，该项目旨在探索使用一种名为CRISPRa的创新基因编辑技术的可能性，以激活患者自己的基因拷贝，并使它们在存活的视网膜细胞中表达具有恢复视力潜力的光检测蛋白。这些方法有可能导致更广泛的致盲性疾病的治疗。光遗传学治疗可能成为一种普遍的治疗方法，并恢复视力，在任何晚期视网膜变性，无论遗传原因。视网膜神经节细胞靶向的改善可能导致LHON和其他视神经病变的潜在治疗，包括青光眼，这是全球不可逆失明的最常见原因。此外，改进的线粒体靶向可能对治疗导致全身性疾病并涉及眼睛以外器官的其他遗传性线粒体疾病具有意义。

Inherited retinal diseases, including retinitis pigmentosa and Leber congenital optic neuropathy (LHON) are the leading cause of untreatable blindness in the younger population in developed countries. They are caused by genetic mutations that lead to premature loss of cells in the retina that are important for vision. In retinitis pigmentosa, light detecting cells called photoreceptors are lost, but other retinal cells such as ganglion cells that transmit impulses to the brain remain intact. In LHON, mutations in mitochondrial genes affect the ganglion cells first, so the signal from the retina cannot be sent to the brain. Significant advances have been made in research to develop genetic treatments for these diseases, and we now have an approved gene therapy treatment, Luxturna, for one form of the disease caused by mutations in a specific gene. Gene therapy treatments aim to replace the mutated genes by healthy copies. However, for many patients, mutations are not known and for those who present late, where the photoreceptors have already been loss, gene replacement may not be possible. In these patients, optogenetic therapy is a very promising strategy where light sensitive proteins are expressed in surviving cells of the retina, including ganglion cells, to make them able to detect light and restore vision. However, efficient targeting of these cells with genetic therapies has not been achieved to date. Moreover, as the mitochondria in ganglion cells are affected in LHON, if we can deliver healthy genes to these cells, and in particular to the mitochondria, then there is potential to slow down ganglion cell degeneration and associated loss of vision. In this project we aim to develop a surgical procedure using a robot to more effectively deliver genetic therapies to retinal ganglion cells. The procedure will involve robot-assisted direct infusion into the optic nerve in an animal model, which is currently not possible to perform manually in patients. Having achieved this, we then aim to develop applications for this technique including optogenetic applications and for the treatment of optic neuropathies in future human clinical trials. Lastly, the project aims to explore the possibility of using an innovative gene editing technique called CRISPRa, to activate patients' own copies of genes and make them express light-detecting proteins in surviving retinal cells with potential to restore vision. The approaches have potential to lead to the treatment of a much broader range of blinding diseases. Optogenetic therapy could become a universal treatment and restore vision in any late stage retinal degeneration irrespective of genetic cause. Improved targeting of retinal ganglion cells could lead to potential treatments of LHON and other optic neuropathies including glaucoma, the most common cause of irreversible blindness worldwide. In addition, improved mitochondrial targeting may have implications for treatment of other inherited mitochondrial disease that lead to systemic diseases and involve organs other than the eye.