Non-resolving inflammation is a key characteristic of retinal degenerative diseases. During disease, microglia, typically responsible for maintenance of the steady-state, become pathogenic. This pathogenic response includes an increase in phagocytosis, cytokine production and complement deposition, and migration of the local population to the site of damage. Activation of microglia is supplemented by infiltration of blood-borne macrophages into the retina, contributing to the progression of neurodegenerations. While much of the molecular dynamics surrounding the messenger RNA and protein content of the retinal immune population have been characterised, the role that non-coding RNAs play to regulate the microglia/macrophage state in the retina is still poorly understood.
In this study we utilised a Cx3Cr1-Yfp reporter mouse line to study the activation of retinal microglia/macrophage in response to retinal degeneration. Mice underwent 7 days photo-oxidative damage which recapitulates characteristic degenerative processes including outer nuclear layer thinning, microglia activation and macrophage recruitment. Isolated retinal YFP positive immune cells using fluorescence activated cell sorting for subsequent RNA extraction and high throughput Illumina sequencing of the RNA populations.
Overall, we show that the contribution of different RNA biotypes of the retinal immune population undergoes a significant shift in response to retinal degeneration. We further identified modulations in specific miRNA, piRNA, snRNA, rRNA and lncRNA in the photo-oxidative damage samples when compared to controls. We also observed that downregulated mRNA targets were involved in pathways such as ‘post-transcriptional gene silencing’, ‘splicing via transesterification reactions’ and ‘regulation of mRNA processing’.
Our data suggests that RNA regulation plays a role in neurodegeneration in the retina. We theorise that targeting this connection to manage the pro-inflammatory functions of microglia/macrophages, could provide significant advancement towards the development of therapeutic interventions.