Aims

Neurodegeneration of the optic nerve and retinal ganglion cells (RGCs) leads to progressive vision loss. As part of the central nervous system, RGCs show limited ability to regenerate and there is extensive search for neuroprotective agents for optic nerve damage. Methylene blue (MB) exhibits beneficial effects against various neurodegenerative diseases of the central nervous system. However, the mechanisms associated with its putative protection on neuronal survival and regeneration remain obscure. This study used the optic nerve transection model to examine the effects of MB on RGC survival, the expression of regenerative marker GAP-43 in RGCs and microglial activation.

Main methods

Axons of RGCs were injured by cutting the optic nerve. MB was injected intravitreally either immediately post-injury or delayed to 3 days post-injury. Using immunohistochemical staining, surviving RGCs, GAP-43-positive RGCs and microglial cells were quantified in wholemount retinas 7 days post-injury.

Key findings

Both immediate and delayed (a more clinically realistic situation) intravitreal injection of MB promoted RGC survival. MB also increased the number of GAP-43-positive RGCs, suggesting an enhanced ability of RGCs to regenerate. This was exemplified by the regenerative sprouting of axon-like processes from injured RGCs after MB treatment. The increase in RGC survival and GAP-43 expression correlated with an increase in the number of microglial cells.

Significance

These results reveal that MB has survival-promoting and growth-promoting effects on RGCs after optic nerve injury. Together with the established safety profile of MB in humans, MB is a promising treatment for neurodegeneration and injury of the optic nerve.

中文翻译：

---

亚甲基蓝促进视神经横断后视网膜神经节细胞的存活和GAP-43表达。

目的

视神经和视网膜神经节细胞（RGC）的神经变性会导致进行性视力丧失。作为中枢神经系统的一部分，RGCs的再生能力有限，因此人们广泛寻找视神经损伤的神经保护剂。亚甲蓝（MB）对中枢神经系统的各种神经退行性疾病表现出有益的作用。然而，与其对神经元存活和再生的假定保护相关的机制仍然不清楚。这项研究使用视神经横断模型研究了MB对RGC存活，再生标记GAP-43在RGC中的表达以及小胶质细胞活化的影响。

主要方法

RGC的轴突被切断视神经而受伤。损伤后立即玻璃内注射MB，或延迟至损伤后3天。使用免疫组织化学染色，在损伤后7天对全视网膜中的存活RGC，GAP-43阳性RGC和小胶质细胞进行定量。

主要发现

立即和延迟（更现实的临床情况）MB玻璃体内注射均可促进RGC生存。MB还增加了GAP-43阳性RGC的数量，表明RGC的再生能力增强。MB处理后，受伤的RGC会出现轴突样过程的再生萌芽，从而证明了这一点。RGC存活和GAP-43表达的增加与小胶质细胞数量的增加相关。

意义

这些结果表明MB对视神经损伤后的RGC具有存活促进和生长促进作用。连同已建立的MB在人体内的安全性，MB是一种用于神经变性和视神经损伤的有前途的治疗方法。