Abstract
Purpose :
In the CNS, microglia have been shown to be important for synaptic pruning during development but its role during neurodegenerative processes is not well understood. Our previous work demonstrates that after intraocular pressure (IOP) elevation, microglia proliferate, activate, and increase their colocalization with synapses. Here we use live imaging to record microglia movement and their interaction with retinal ganglion cell (RGC) post-synaptic puncta in the inner plexiform layer (IPL).
Methods :
Adult Cx3cr1-GFP mice had one eye undergo laser-induced ocular hypertension, a model in which IOP is transiently elevated and returns to baseline by 7 days. Prior to IOP elevation, some animals underwent intravitreal injection with AAV-PSD95-RFP, resulting in RGCs that express fluorescently labelled post-synaptic puncta. Contralateral eye served as control. Animals were euthanized 7 days post-laser. Time-lapse z-stack images of ex vivo retina was acquired with a spinning disk confocal every 30 seconds for a total of ten minutes. Statistics were performed using Student’s t-test.
Results :
After IOP elevation, IPL microglia increase in number and exhibit morphological change consistent with activation. Increased movement is seen in the microglia from the lasered eye, where there is active filament displacement, extension, and retraction. In response to IOP elevation, microglia show greater process displacement length (2.14 um in laser (SE=0.45) vs. 0.79 um in control (SE=0.19); P=0.03) and faster process speed in the lasered (0.01 um/s; SE=0.005) in comparison to control (0.002 um/s; SE= 0.0005; P=0.02). Microglia contact with PSD95 is seen in both control and lasered eye. However, microglia in the control eye exhibit less process displacement and motility, and furthermore, microglia contact with PSD95 is more superficial in the control condition. In contrast, after IOP elevation activated microglia appear to have engulfed PSD95.
Conclusions :
Activated microglia increase their motility, survey their environment, and possibly engulf synaptic proteins. Whether this activity is neuroprotective or neurodegenerative remains a subject of ongoing study.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.