Gu Xiaowu, Truong Tom, Heaster-Ford Tiffany, Kim Tae-Hoon, Kang Gyeong Jin, Yung Joanna, Baca Miriam, Chaney Shawnta Y, Hofmann Jeffrey W, Eastham Jeffrey, Jeanne Marion
Department of Neuroscience, Genentech, Inc., South San Francisco, California, United States.
Department of Translational Immunology, Genentech, Inc., South San Francisco, California, United States.
Invest Ophthalmol Vis Sci. 2025 Sep 2;66(12):56. doi: 10.1167/iovs.66.12.56.
Microgliosis is a key neuroinflammatory feature in human glaucomatous retinas, believed to contribute to disease progression. This study aims to characterize changes in microglia and intra-retinal axons following optic nerve crush (ONC) and investigate microglial involvement in retinal ganglion cell (RGC) and axonal degeneration.
Using the CD11c.YFP.Venus.Tg mouse line, we tracked microglial activation and assessed the spatiotemporal changes in TUJ1+ intraretinal axons over a 2-week period post-ONC. Microglial function was examined by depleting microglia with the CSF1R inhibitor PLX5622 and using Trem2-deficient mice with dampened microglial activation.
Activated microglia accumulated significantly in the retina from day 4 post-ONC, peaking at day 7. Retinal microglia became hypertrophic by day 1 and started proliferating. Axon beading occurred primarily in the peripheral retina by day 2 post-ONC, with more beaded axons appearing along long axonal bundles toward the optic nerve head (ONH) by day 7 and day 14. There was a significant reduction in overall TUJ1 expression and axonal bundle thickness during this period. Despite complete microglial depletion and significantly reduced activation, no differences were observed in the RGC count or the extent of optic nerve damage following ONC.
Microglial activation is secondary to axonal injury and plays a bystander role in the ONC model. Robust RGC and axonal degeneration appear unaffected by activated microglia. This finding challenges the utility of the ONC model for evaluating microglia-based glaucoma treatments. Additionally, the study reaffirms the value of combining fluorescent reporter mouse lines with noninvasive ocular imaging for streamlining future research.
小胶质细胞增生是人类青光眼视网膜的关键神经炎症特征，被认为会促进疾病进展。本研究旨在表征视神经挤压（ONC）后小胶质细胞和视网膜内轴突的变化，并研究小胶质细胞在视网膜神经节细胞（RGC）和轴突退变中的作用。
使用CD11c.YFP.Venus.Tg小鼠品系，我们追踪小胶质细胞的激活情况，并评估ONC后2周内TUJ1+视网膜内轴突的时空变化。通过用CSF1R抑制剂PLX5622清除小胶质细胞并使用小胶质细胞激活减弱的Trem2缺陷小鼠来检测小胶质细胞功能。
激活的小胶质细胞在ONC后第4天开始在视网膜中显著积聚，在第7天达到峰值。视网膜小胶质细胞在第1天开始肥大并开始增殖。轴突串珠主要在ONC后第2天出现在周边视网膜，到第7天和第14天，沿着朝向视神经乳头（ONH）的长轴突束出现更多串珠状轴突。在此期间，总体TUJ1表达和轴突束厚度显著降低。尽管小胶质细胞完全耗尽且激活显著减少，但ONC后RGC计数或视神经损伤程度未观察到差异。
小胶质细胞激活继发于轴突损伤，在ONC模型中起旁观者作用。强烈的RGC和轴突退变似乎不受激活的小胶质细胞影响。这一发现挑战了ONC模型在评估基于小胶质细胞的青光眼治疗中的实用性。此外，该研究重申了将荧光报告小鼠品系与非侵入性眼部成像相结合以简化未来研究的价值。
