Project description:In many forms of retinal degenerative diseases in human, microglia relocate to and accumulate in the subretinal space. However, the roles of microglia in retinal degeneration are poorly understood. By leveraging single cell RNA-seq, we identified a distinct microglia subtype in the subretinal space. These microglia underwent transcriptional reprogramming characterized by reduced expression of homeostatic checkpoint genes and upregulation of injury-responsive genes. Importantly, this transition is associated with protection of the retinal pigment epithelium from damage caused by disease. Therefore, our data demonstrated microglial heterogeneity in retinal degeneration and may provide important implications for developing new strategies to prevent loss of vision.
Project description:Dysfunctional humoral and cellular innate immunity are key components in the development and progression of age-related macular degeneration (AMD). Specifically, chronically activated microglia and their disturbed regulatory system contribute to retinal degeneration. Galectin-3, a b-galactose binding protein, is a potent driver of macrophage and microglia activation and has been implicated in neuroinflammation, including neurodegenerative diseases of the brain. Here, we report that galectin-3 is strongly upregulated in reactive retinal microglia of AMD patients and in two related mouse models of retinal degeneration. Specific targeting of galectin-3 by genetic knockout or using the small-molecule inhibitor TD139 blocks microglia reactivity and protects from retinal damage in different models of light-induced retinal degeneration. These data define galectin-3 as potent driver of retinal degeneration and highlight the protein as a drug target for ocular immunomodulatory therapies.
Project description:To investigate the role of aldose reductase (AR) inhibition using Sorbinil on retinal microglia (RMG) activation, retinal ganglion cell (RGC) survival, and axon regeneration after optic nerve trauma. We observed that AR inhibition using Sorbinil attenuates RMG activation and subsequently promotes RGC survival and delays axon degeneration one week after optic nerve crush.
Project description:Both resident microglia and invading peripheral immune cells can respond to injury and degeneration in the central nervous system. However, after dead and dying neurons have been cleared and homeostasis is re-established, it is unknown whether resident immune cells fully resume normal functions and to what degree the peripheral immune cells take up residence. Using flow cytometry, in vivo retinal imaging, immunohistochemistry, and single-cell mRNA sequencing, we assess resident microglia and monocyte-derived macrophages in the retina during and after the loss of photoreceptors in the Arr1-/- mouse model of inducible degeneration. We find that photoreceptor loss results in a small, sustained increase in mononuclear phagocytes and, after degeneration wanes, these cells re-establish a spatial mosaic reminiscent of healthy retinas. Transcriptomic analysis revealed the population remained unusually heterogeneous, with several subpopulations expressing gene patterns consistent with mildly activated phenotypes. Roughly a third of “new resident” cells expressed markers traditionally associated with both microglial and monocytic lineages, making their etiology ambiguous. Using an inducible Cre-based fluorescent lineage tracing paradigm to confirm the origins of new resident immune cells, we found approximately equal numbers of microglia and monocyte-derived macrophages after degeneration had subsided. In vivo retinal imaging and immunohistochemical analysis showed that both subpopulations remained functionally responsive to sites of local damage, though on average the monocyte-derived cells had less morphological complexity, expressed higher levels of MHCII, and had less migratory activity than the native resident population. Monocytic cells that infiltrate the retina during degeneration differentiate into monocyte-derived macrophages that can remain in the retina long-term. These monocyte-derived macrophages adopt ramified morphologies and microglia-like gene expression. However, they remain distinguishable in morphology and gene expression from resident microglia and appear to differ functionally, showing less responsiveness to subsequent retinal injuries. These findings support the idea that persistent changes in the local immune population in response to cell loss in aging and progressive retinal diseases may include subpopulations of bone marrow derived cells whose ability to respond to subsequent insults wanes over time.
Project description:Age-related macular degeneration (AMD) is a leading cause of vision loss, with its dry form characterized by retinal pigment epithelium (RPE) degeneration and photoreceptor loss. However, the underlying mechanisms driving these pathological changes remain poorly understood. Here, we identify a critical role for microglia-RPE cell interactions mediated by the SPP1-ITGAV signaling axis in dry AMD pathogenesis.
Project description:Retinal degeneration is a collection of devastating conditions with progressive loss of vision which often lead to blindness. Research on retinal microglial cells offers great therapeutic potential in deterring the progression of the condition. This study explored the mechanisms underlying the TREM2-mediated protective function of activated microglial cells during retinal degeneration. A significant upregulation of disease-associated microglia signature genes was observed during photoreceptor degeneration.
Project description:We used single cell RNA-seq to comprehensively map all retinal microglia populations in a mouse model of oxygen-induced PR. We unveiled several unique types of PR-associated microglia (PRAM) and identified markers, signaling pathways, and regulons associated with these cells. Among these microglial subpopulations, we found a highly proliferative subset of cells with a high self-renewal capacity and a subset of cells with hypermetabolism that expresses high levels of activating microglia markers, glycolytic enzymes, and pro-angiogenic insulin-like growth factor 1. Immunohistochemical staining shows that PRAMs were spatially located within neovascular tufts. These unique microglial subtypes have the potential to promote retinal angiogenesis, which may have important implications for the future treatment of PR and other ocular diseases characterized by pathological angiogenesis.
Project description:Microglia are the tissue-resident macrophages of the retina and brain, being critically involved in organ development, tissue homeostasis, and response to cellular damage. Until now, little is known about the transcriptional profile of human retinal microglia and how they differentiate from peripheral monocytes, as well as from brain microglia. Additionally, the degree to which mice are suitable models for human retinal microglia is still not clear. The present study applies fluorescence-activated cell sorting to isolate human retinal microglia from enucleated eyes and compares their transcriptional profile with that of whole retinal tissue, as well as classical, intermediate and non-classical monocytes. In addition, human retinal microglia are compared to murine retinal microglia, isolated from at least two-years old Cx3cr1GFP/+ mice, as well as human brain microglia obtained from the literature. Several overexpressed genes were identified in retinal microglia when compared to whole retinal tissue, as well as classical, intermediate, and non-classical monocytes, among them IL1B, C2, C3, TREM2, P2RY12 and SPP1. In relation to whole retina sequencing, several risk genes, such as APOE and TGBR1, as well as PLXDC2 and ARHGAP22 associated with age-related macular degeneration (AMD) and diabetic retinopathy (DRP), were preferentially expressed in retinal microglia, indicating their potential pathophysiological involvement. The top expressed genes exhibited a strong consistency between retinal and brain microglia, among them CD74, SPP1, ACTB, FTL and C3. There was a high degree of similarity between human and murine retinal microglia, although there were several species-specific genes, revealing for which genes mice are suitable models for human retinal microglia. This study provides detailed insights into the molecular profile of human retinal microglia and indicate a high similarity to brain microglia. It advances our under-standing about their role in human retinal disease, such as AMD and DRP. The similarities and differences between human and mice will facilitate the transferability of knowledge between both species.
Project description:X-linked retinoschisis (XLRS), caused by Retinoschisin 1 (RS1) gene mutations, leads to progressive retinal degeneration. While photoreceptor loss is a hallmark of the disease, its early pathogenic mechanisms are not well understood. Using CRISPR/Cas9-edited Rs1-exon2-knockout mice, we investigated the temporal progression of the retinal degeneration. Single-cell RNA sequencing revealed that the degeneration of bipolar cells, particularly the OFF-cone subtype, precedes photoreceptor loss. This early degeneration was driven by microglial activation and their subsequent phagocytosis of bipolar cells via phosphatidylserine exposure and C3b activation that was independent of apoptosis. These findings reveal a temporal sequence of neurodegeneration in XLRS, highlighting bipolar cells as a critical therapeutic target for early intervention.