Probes for INS

Transforming growth factor β (TGFβ) signaling has manifold functions such as regulation of cell growth, differentiation, migration, and apoptosis. Moreover, there is increasing evidence that it also acts in a neuroprotective manner. We recently showed that TGFβ receptor type 2 (Tgfbr2) is upregulated in retinal neurons and Müller cells during retinal degeneration. In this study we investigated if this upregulation of TGFβ signaling would have functional consequences in protecting retinal neurons. To this end, we analyzed the impact of TGFβ signaling on photoreceptor viability using mice with cell type-specific deletion of Tgfbr2 in retinal neurons and Müller cells (Tgfbr2ΔOC) in combination with a genetic model of photoreceptor degeneration (VPP). We examined retinal morphology and the degree of photoreceptor degeneration, as well as alterations of the retinal transcriptome. In summary, retinal morphology was not altered due to TGFβ signaling deficiency. In contrast, VPP-induced photoreceptor degeneration was drastically exacerbated in double mutant mice (Tgfbr2ΔOC; VPP) by induction of pro-apoptotic genes and dysregulation of the MAP kinase pathway. Therefore, TGFβ signaling in retinal neurons and Müller cells exhibits a neuroprotective effect and might pose promising therapeutic options to attenuate photoreceptor degeneration in humans.

Microglia, the resident immune cells in the retina and nervous system, make irreplaceable contributions to the maintenance of normal homeostasis and immune surveillance of these systems. Recently, great progress has been made in determining the origin, distribution, features and functions of retinal microglia and in identifying their roles in retinal diseases. In the retinal microenvironment, microglia constantly monitor changes in their surroundings and maintain balanced functions by communicating with other retinal cells. When disturbed, activated microglia may kill degenerated neurons and photoreceptors through phagocytosis and exacerbate retinal injury by producing multiple proinflammatory mediators. Numerous animal studies and in situ analyses of human tissue have shown that retinal microglia are involved in multiple retinal diseases. The functions and mechanisms of activated microglia in retinal disorders are gradually being elucidated. Increasing evidence points towards the dual roles of microglia in the retina and they are regulated by many factors. How to inhibit the detrimental effects of microglia and promote beneficial effects are worth studying. This review focuses primarily on the features and functions of microglia and how they participate in retinal diseases based on existing research findings. We also discuss current opinions about microglial transdifferentiation.

RESULTS : Uniform Manifold Approximation and Projection clustering identified distinct expression signatures from the ganglion cell layer(GCL), inner nuclear layer(INL), retinal pigment epithelium (RPE)/choroid/sclera, optic nerve, and ciliary body (Fig, 1) but not the outer nuclear layer(ONL) which was contaminated with expression from other layers. Our findings highlight Clu, C4b, Apoe, and C1qa genes (z-score 3.0, 2.4, 2.3, and 2.2) as potential markers of disease in the RPE. Gene Set Enrichment analysis between rd6 and WT eyes showed upregulation of glycolysis and carbon metabolism pathways in the GCL and Rap1, Hippo and lysosome pathways in the RPE/Choroid/sclera. The ribosomal pathway was downregulated in these layers. No significant pathways were found in the INL, ciliary body or optic nerve.

RESULTS : PR-specific expression of _PRLΔE1_ was observed in the following canine models of progressive inherited retinal degeneration (IRD): _RPGR_-XLPRA1 and _NPHP5_-LCA. In _RPGR_-XLPRA2 carrier retinas that undergo random X-inactivation, patches of_ PRLΔE1 _expression correlated with patches of PR degeneration. However, we did not observe expression of _PRLΔE1_ 24 hrs and 2 wks after light exposure that triggers acute rod loss in the canine RHO-T4R model of adRP. No _PRLΔE1 _expression was seen either in the _CNGB3_-ACHM3 retina that undergoes extremely slow cone degeneration. In _RPGR-_XLPRA1 and _RPGR-_XLPRA2 dogs subretinally-injected with an AAV-_RPGR_ vector, _PRLΔE1 _was completely absent in treated PRs while robust expression was seen in diseased/untreated areas.

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 β-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 hypothesized that genetic deficiency of galectin-3 or its modulation via TD139 dampens mononuclear phagocyte reactivity and delays retinal degeneration.Galectin-3 expression in AMD patients was analyzed by immunohistochemical stainings. Galectin-3 knockout and BALB/cJ mice were exposed to white bright light with an intensity of 15,000 lux for 1 h and Cx3cr1GFP/+ mice to focal blue light of 50,000 lux for 10 min. BALB/cJ and Cx3cr1GFP/+ mice received intraperitoneal injections of 15 mg/kg TD139 or vehicle for five consecutive days, starting one day prior to light exposure. The effects of galectin-3 deficiency or inhibition on microglia were analyzed by immunohistochemical stainings and in situ hybridization of retinal sections and flat mounts. Pro-inflammatory cytokine levels in the retina and retinal pigment epithelium (RPE) were quantified by qRT-PCR and transcriptomic changes were analyzed by RNA-sequencing. Retinal thickness and structure were evaluated by optical coherence tomography.We found that galectin-3 expression was strongly upregulated in reactive retinal mononuclear phagocytes of AMD patients and in the two related mouse models of light-induced retinal degeneration. The experimental in vivo data further showed that specific targeting of galectin-3 by genetic knockout or administration of the small-molecule inhibitor TD139 reduced microglia reactivity and delayed retinal damage in both light damage conditions.This study defines galectin-3 as a potent driver of retinal degeneration and highlights the protein as a drug target for ocular immunomodulatory therapies.