Retinal Microglia

We congratulate Dr. Liu and colleagues for their study on the in vivo tracking of retinal microglial cells after experimental damage to the optic nerve. ¹ In a recent histomorphometric study, ² the varying morphology of microglia cells has been differentiated into 6 stages of bidirectional microglial activation (A) and deactivation (R): 

 

“from stage 1A to 6A, the cell body size increased, the cell process number decreased, and the cell processes retracted and thickened, orienting toward the direction of the injury site; until stage 6A, when all processes disappeared. In contrast, in deactivation stages 6R to 1R, the microglia returned to the original site, exhibiting a stepwise retransformation to the original morphology. Thin highly branched processes re-formed in stage 1R, similar to those in stage 1A. This reverse transformation mirrored the forward transformation except in stages 6R to 1R: cells showed multiple nuclei which were slowly absorbed.”

 

We would ask Dr. Liu and colleagues, whether they were able to in vivo categorize the retinal microglial cells in their study by using a staging system similar to the one described above? Such a staging system could facilitate the description and quantification of changes in the retinal microglial system after damage to the retina and optic nerve.