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Updated: Mar 29, 2026
Author Spotlight: Unraveling the Pathogenesis of Age-Related Macular Degeneration and Discovering Potential Therapies
Published on: July 28, 2023
Spatiotemporal Cadence of Macrophage Polarisation in a Model of Light-Induced Retinal Degeneration
Haihan Jiao1, Riccardo Natoli1,2, Krisztina Valter1,2
1John Curtin School of Medical Research, The Australian National University, Canberra, Australian Capital Territory, Australia.
Background:
The recruitment of macrophages accompanies almost every pathogenic state of the retina, and their excessive activation in the subretinal space is thought to contribute to the progression of diseases including age-related macular degeneration. Previously, we have shown that macrophages aggregate in the outer retina following damage elicited by photo-oxidative stress, and that inhibition of their recruitment reduces photoreceptor death. Here, we look for functional insight into macrophage activity in this model through the spatiotemporal interplay of macrophage polarisation over the course of degeneration.
Methods:
Rats were exposed to 1000 lux light damage (LD) for 24 hrs, with some left to recover for 3 and 7 days post-exposure. Expression and localisation of M1- and M2- macrophage markers was investigated in light-damaged retinas using qPCR, ELISA, flow cytometry, and immunohistochemistry.
Results:
Expression of M1- (Ccl3, Il-6, Il-12, Il-1β, TNFα) and M2- (CD206, Arg1, Igf1, Lyve1, Clec7a) related markers followed discrete profiles following light damage; up-regulation of M1 genes peaked at the early phase of cell death, while M2 genes generally exhibited more prolonged increases during the chronic phase. Moreover, Il-1β and CD206 labelled accumulations of microglia/macrophages which differed in their morphological, temporal, and spatial characteristics following light damage.
Conclusions:
The data illustrate a dynamic shift in macrophage polarisation following light damage through a broad swathe of M1 and M2 markers. Pro-inflammatory M1 activation appears to dominate the early phase of degeneration while M2 responses appear to more heavily mark the chronic post-exposure period. While M1/M2 polarisation represents two extremes amongst a spectrum of macrophage activity, knowledge of their predominance offers insight into functional consequences of macrophage activity over the course of damage, which may inform the spatiotemporal employment of therapeutics in retinal disease.
Insights
In retinal degeneration, pro-inflammatory M1 macrophage activation dominates early damage, while M2 markers indicate chronic responses. Understanding this macrophage polarization shift is key for developing targeted retinal disease therapeutics.
Area of Science:
- Ophthalmology
- Immunology
- Neuroscience
Background:
- Macrophage recruitment and activation in the retina are implicated in various pathogenic states, including age-related macular degeneration.
- Excessive subretinal macrophage activation contributes to disease progression.
- Previous studies showed photoreceptor death reduction upon inhibiting macrophage recruitment after photo-oxidative stress.
Purpose of the Study:
- To investigate the functional insights into macrophage activity during retinal degeneration.
- To analyze the spatiotemporal interplay of macrophage polarization following light-induced damage.
Main Methods:
- Rats were subjected to light damage (LD) and allowed to recover for 3 and 7 days.
- Expression and localization of M1 and M2 macrophage markers were assessed using qPCR, ELISA, flow cytometry, and immunohistochemistry.
Main Results:
- M1 marker expression peaked during the early phase of cell death, while M2 markers showed prolonged increases in the chronic phase.
- Distinct morphological, temporal, and spatial characteristics were observed for M1 and M2 macrophage accumulations labeled by Il-1β and CD206.
Conclusions:
- The study demonstrates a dynamic shift in macrophage polarization following light damage, with distinct M1 and M2 profiles.
- Pro-inflammatory M1 activation is prominent in the early degeneration phase, whereas M2 responses are more characteristic of the chronic phase.
- Understanding macrophage polarization dynamics provides insights into functional consequences of macrophage activity, aiding therapeutic strategies for retinal diseases.
