Project description:The innate immune system plays key roles in tissue regeneration. For example, microglia promote neurogenesis in Müller glia in birds and fish after injury. Although mammalian retina does not normally regenerate, neurogenesis can be induced in mouse Müller glia by Ascl1, a proneural transcription factor. We show that in mice, microglia inhibit the Ascl1-mediated retinal regeneration, suggesting the innate immune system limits the regenerative response to injury.
Project description:In order to evaluate the gene expression profile of retinal microglia cells in different age, we purified CD11b-positive microglia from the retinas of wild type C57BL/6 mice at 3, 12, 18, and 24 months age using cell sorting method with flow cytometry. Age-related genes from isolated retinal microglia were performed using 16 Affymetrix GeneChips of Mouse Exon 1.0ST Arrays. Gene expression level between consecutive age groups (i.e. between 3 and 12 months, 12 and 18 months, and 18 and 24 months) was examined to identify microglia relevant aging genes that demonstrated significant changes. We identified a total 719 genes that showed increasing or decreasing more than 1.5-fold change (p<0.05, one-way ANOVA) for at least one of the three inter age-group comparisons. These identified genes were subjected to a hierarchical cluster analysis to visualize trends in differential expression across individual biological repeats in the 4 age groups. The microglia cells were isolated from wild type C57BL/6 mice with microglia cell specific marker CD11b conjugated with FITC using flowcytometry sorting. The aging time point was designed as 4 groups: 3 moth, 12 month, 18 month and 24 month; each group includes 4 repeats. The total RNA was extracted from isolated retinal microglia cells and reverse transcripted to cDNA after amplification and labeling. The gene expression profile was detected with Affymetrix GeneChip of Mouse Exon 1.0ST Arrays
Project description:Retinal ganglion cells (RGCs) convey the major output of information collected from the eye to the brain. RGCs are irreversibly lost when injured in degenerative diseases such as glaucoma; this failure can be partially reversed by eliminating the retinal mobile zinc (Zn2+) and leads to substantial axon regeneration. ZnT3 conditional knockout in retinal amacrine cells blocks the synaptic transport of Zn2+, which promotes RGC survival and axonal regeneration in optic nerve jinjury (ONC). Here, we conducted an mRNA sequencing of flow cytometry-isolated RGCs 3 days after optic nerve injury with or without ZnT3 expression in retinal amacrine cells.
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: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:Many retinal diseases lead to the loss of retinal neurons and cause visual impairment. The adult mammalian retina has little capacity for regeneration. By contrast, teleost fish functionally regenerate their retina following injury, and Müller glia (MG) are the source of regenerated neurons. The proneural transcription factor Ascl1 is upregulated in MG after retinal damage in zebrafish and is necessary for regeneration. Although Ascl1 is not expressed in mammalian MG after injury, forced expression of Ascl1 in mouse MG induces a neurogenic state in vitro and in vivo after NMDA (N-methyl-d-aspartate) damage in young mice. However, by postnatal day 16, mouse MG lose neurogenic capacity, despite Ascl1 overexpression. Loss of neurogenic capacity in mature MG is accompanied by reduced chromatin accessibility, suggesting that epigenetic factors limit regeneration. Here we show that MG-specific overexpression of Ascl1, together with a histone deacetylase inhibitor, enables adult mice to generate neurons from MG after retinal injury. The MG-derived neurons express markers of inner retinal neurons, synapse with host retinal neurons, and respond to light. Using an assay for transposase-accessible chromatin with high-throughput sequencing (ATAC-seq), we show that the histone deacetylase inhibitor promotes accessibility at key gene loci in the MG, and allows more effective reprogramming. Our results thus provide a new approach for the treatment of blinding retinal diseases.
Project description:Müller glia can serve as a source for retinal regeneration in some non-mammalian vertebrates. Recently we found that this process can be induced in mouse Müller glia after injury, by combining transgenic expression of the proneural transcription factor Ascl1 and the HDAC inhibitor TSA. However, new neurons are only generated from a subset of Müller glia in this model, and identifying factors that limit Ascl1-mediated MG reprogramming could potentially make this process more efficient, and potentially useful clinically. One factor that limits neurogenesis in some non-mammalian vertebrates is the STAT pathway activation that occurs in Müller glia in response to injury. In this report, we tested whether injury induced STAT activation hampers the ability of Ascl1 to reprogram Müller glia into retinal neurons. Using a STAT inhibitor, in combination with our previously described reprogramming paradigm, we found a large increase in the ability of Müller glia to generate neurons, similar to those we described previously. Single-cell RNA-seq showed that the progenitor-like cells derived from Ascl1-expressing Müller glia have a higher level of STAT signaling than those that become neurons. Using Ascl1 ChIP-seq and DNase-seq, we found that developmentally inappropriate Ascl1 binding sites (that were unique to the overexpression context) had enrichment for the STAT binding motif. This study provides evidence that STAT pathway activation reduces the efficiency of Ascl1-mediated reprogramming in Müller glia, potentially by directing Ascl1 to developmentally inappropriate targets.