Microglia depletion/repopulation does not affect light-induced retinal degeneration in mice
Nils Laudenberg1, Urbanus Muthai Kinuthia1,2, Thomas Langmann1,2
1Laboratory for Experimental Immunology of the Eye, Department of Ophthalmology, Faculty of Medicine and University Hospital Cologne, University of Cologne, Cologne, Germany.
Abstract:
Reactive microglia are a hallmark of age-related retinal degenerative diseases including age-related macular degeneration (AMD). These cells are capable of secreting neurotoxic substances that may aggravate inflammation that leads to loss of photoreceptors and impaired vision. Despite their role in driving detrimental inflammation, microglia also play supporting roles in the retina as they are a crucial cellular component of the regulatory innate immune system. In this study, we used the colony stimulating factor 1 receptor (CSF1R)-antagonist PLX3397 to investigate the effects of microglia depletion and repopulation in a mouse model of acute retinal degeneration that mimics some aspects of dry AMD. Our main goal was to investigate whether microglia depletion and repopulation affects the outcome of light-induced retinal degeneration. We found that microglia depletion effectively decreased the expression of several key pro-inflammatory factors but was unable to influence the extent of retinal degeneration as determined by optical coherence tomography (OCT) and histology. Interestingly, we found prominent cell debris accumulation in the outer retina under conditions of microglia depletion, presumably due to the lack of efficient phagocytosis that could not be compensated by the retinal pigment epithelium. Moreover, our in vivo experiments showed that renewal of retinal microglia by repopulation did also not prevent rapid microglia activation or preserve photoreceptor death under conditions of light damage. We conclude that microglia ablation strongly reduces the expression of pro-inflammatory factors but cannot prevent photoreceptor loss in the light-damage paradigm of retinal degeneration.
Insights
Microglia depletion in retinal degeneration models reduces inflammation but does not prevent photoreceptor loss. Repopulation also failed to protect against light-induced damage, suggesting limited therapeutic benefit.
Area of Science:
- Ophthalmology
- Neuroscience
- Immunology
Background:
- Reactive microglia are implicated in age-related retinal diseases like AMD.
- While contributing to neuroinflammation, microglia also have essential immune-regulatory roles in the retina.
Purpose of the Study:
- To investigate the impact of microglia depletion and repopulation on light-induced retinal degeneration.
- To assess the role of microglia in photoreceptor survival and inflammation in a dry AMD model.
Main Methods:
- Utilized PLX3397, a CSF1R antagonist, for microglia depletion in a mouse model.
- Evaluated retinal degeneration using optical coherence tomography (OCT) and histology.
- Assessed pro-inflammatory factor expression and photoreceptor death.
Main Results:
- Microglia depletion reduced pro-inflammatory factors but did not alter the extent of retinal degeneration.
- Observed significant cell debris accumulation in depleted retinas, indicating impaired phagocytosis.
- Microglia repopulation did not prevent photoreceptor death or reduce microglia activation under light damage.
Conclusions:
- Microglia ablation decreases inflammation but does not prevent photoreceptor loss in this model.
- The phagocytic capacity of microglia is crucial for clearing debris in retinal degeneration.
- Targeting microglia solely for depletion may not be a sufficient therapeutic strategy for AMD.
