Neuronal sirtuin1 mediates retinal vascular regeneration in oxygen-induced ischemic retinopathy

Regeneration of blood vessels in ischemic neuronal tissue is critical to reduce tissue damage in diseases. In proliferative retinopathy, initial vessel loss leads to retinal ischemia, which can induce either regrowth of vessels to restore normal metabolism and minimize damage, or progress to hypoxia-induced sight-threatening pathologic vaso-proliferation. It is not well understood how retinal neurons mediate regeneration of vascular growth in response to ischemic insults. In this study we aim to investigate the potential role of Sirtuin 1 (Sirt1), a metabolically-regulated protein deacetylase, in mediating the response of ischemic neurons to regulate vascular regrowth in a mouse model of oxygen-induced ischemic retinopathy (OIR). We found that Sirt1 is highly induced in the avascular ischemic retina in OIR. Conditional depletion of neuronal Sirt1 leads to significantly decreased retinal vascular regeneration into the avascular zone and increased hypoxia-induced pathologic vascular growth. This effect is likely independent of PGC-1α, a known Sirt1 target, as absence of PGC-1α in knockout mice does not impact vascular growth in retinopathy. We found that neuronal Sirt1 controls vascular regrowth in part through modulating deacetylation and stability of hypoxia-induced factor 1α and 2α, and thereby modulating expression of angiogenic factors. These results indicate that ischemic neurons induce Sirt1 to promote revascularization into ischemic neuronal areas, suggesting a novel role of neuronal Sirt1 in mediating vascular regeneration in ischemic conditions, with potential implications beyond retinopathy

Retinal neurons govern angiogenesis by regulating opposing actions of Semaphorin 3A and nuclear Protease-activated receptor 2

Proliferative retinopathies (PRs), such as proliferative diabetic retinopathy and retinopathy of prematurity, are leading causes of blindness in children and working age adults. PRs are characterized by initial microvascular degeneration, followed by a compensatory albeit pathological hyper-vascularization mounted by the hypoxic retina attempting to reinstate metabolic equilibrium. Paradoxically, this secondary revascularization fails to grow into the most ischemic regions of the retina. Instead, the new vessels are misdirected towards the vitreous, suggesting that vaso-repulsive forces operate in the avascular hypoxic retina. Here we demonstrate that the neuronal guidance cue Semaphorin3A (Sema3A) secreted by severely hypoxic neurons participates in hindering revascularization of ischemic zones within the retina by deviating vessels away from these avascular areas. Using a rodent model of oxygen induced retinopathy, we provide evidence that Sema3A produced by ischemic retinal ganglion neurons contributes to microvascular decay and later forms a chemical barrier that impedes normal revascularization by repelling neo-vessel towards the vitreous. Conversely, silencing Sema3A expression enhances normal vascular regeneration within the ischemic retina, thereby preserving retinal neuronal function, and consequently diminishing aberrant neovascularization. Protease-activated receptor 2 (PAR2) partakes in retinal angiogenesis and was found to inhibit the production of Sema3A in ischemic retinal ganglion cells (RGCs). In light of the newly recognized contribution of RGCs in regulating retinal angiogenesis, we studied the expression and function of PAR2 in these neurons. Interestingly, we detected PAR2 at the cell nucleus of RGCs. To date, many G-protein coupled receptors (GPCRs), like PAR2, have been reported at the cell nucleus where they evoke in situ gene induction. However, the sub-cellular origin of nuclear GPCRs, the mechanisms governing this localization and their nuclear function, as well as the in vivo physiologic manifestation of nuclear GPCRs are not known. We show that PAR2 translocates from the plasma membrane to the nucleus, requiring specific receptor domains (C-terminus and nuclear localization signals) as well as the recruitment of Importin-β1 and Sorting nexin 11 (SNX11), which interact with microtubules. In turn, nuclear PAR2 recruits transcription factor Sp1 to trigger angiogenic genes and ensued neovascularization. This is the first demonstration of the in vivo physiologic manifestation governed by the nuclear localization of a GPCR. The sub-cellular localization and function of a receptor should therefore be considered in order to achieve more selective therapeutic goals. Approaches that foster normal retinal revascularization and in turn counter pathological neovascularization could prevent or delay the onset of blindness in patients afflicted with ischemic proliferative retinopathies.Les rétinopathies prolifératives (RPs), telles que la rétinopathie diabétique ou du prématuré, sont les principales causes de cécité chez l'enfant et les adultes en âge de travailler. Les RPs sont caractérisées par une phase initiale de dégénérescence microvasculaire, suivie d'une surcompensation pathologique donnant lieu à une hyper-vascularisation initiée par la rétine hypoxique tentant de rétablir l'équilibre métabolique. Paradoxalement, cette revascularisation secondaire ne parvient pas à pénétrer les régions les plus ischémiques de la rétine. Au contraire, ces nouveaux vaisseaux croissent de façon inappropriée vers le corps vitré, ce qui suggère la présence de forces répulsives libérées dans la rétine avasculaire hypoxique. Cette thèse démontre que le signal de guidage neuronal Semaphorin3A (Sema3A) sécrété par les neurones hypoxiques participe à entraver la revascularisation des zones ischémiques de la rétine en repoussant les vaisseaux vers le corps vitré. En utilisant le modèle murin de rétinopahtie induite par l'oxygène, nous démontrons que Sema3A sécrété par les neurones ganglionnaires de la rétine ischémique contribue à la dégénérescence microvasculaire et forme une barrière chimique qui empêche la revascularisation normale de la rétine. À l'inverse, lorsque l'on inhibe l'expression de Sema3A, la revascularisation de la rétine ischémique est accélérée, préservant ainsi la fonction neuronale rétinienne et diminuant la néovascularisation pathologique.Le récepteur activé par les protéases 2 (PAR2) contribue au développement de nouveaux vaisseaux sanguins rétiniens et diminue l'expression de Sema3A. À la lumière de la contribution des cellules ganglionnaires de la rétine dans la régulation de l'angiogenèse rétinienne, nous avons par la suite étudié l'expression et la fonction de PAR2 dans ces neurones. Nous détectons la présence de PAR2 aux noyaux des neurones rétiniens. Plusieurs récepteurs couplés aux protéines G (GPCRs) ont été identifiés au noyau de la cellule, où ils induisent localement différents gènes. Toutefois, l'origine subcellulaire des GPCRs nucléaires, les mécanismes qui gouvernent cette localisation et leur fonction au noyau, de même que leur contribution physiologique demeurent inconnus. Notre travail démontre que PAR2 migre de la membrane plasmatique jusqu'au noyau par l'entremise des microtubules et nécessitant certains domaines spécifiques (région C-terminale et signaux de localisation nucléaire), de même que le recrutement d'importin-β1 et Sorting nexin 11 (SNX11). Ensuite, PAR2 nucléaire recrute le facteur de transcription Sp1 pour déclencher l'expression de gènes pro-angiogéniques et une néovascularization rétinienne. Il s'agit de la première description des manifestations physiologiques in vivo régis par la localisation nucléaire d'un GPCR. La distribution subcellulaire et son influence sur la fonction d'un récepteur doivent être pris en considération afin d'identifier des cibles thérapeutiques plus spécifiques. Des approches thérapeutiques favorisant la revascularization normale des régions ischémiques, et par le fait même freinant la néovascularization pathologique, pourrait prévenir ou retarder l'apparition de la cécité chez les patients souffrant d'une rétinopathie proliférative

OSMR controls glioma stem cell respiration and confers resistance of glioblastoma to ionizing radiation

The suppression of the receptor for oncostatin M (OSMR) can prevent glioblastoma cell growth. Here, the authors demonstrate a role for OSMR in modulating glioma stem cell respiration and its impact on resistance to ionizing radiation

Inhibition of type I PRMTs reforms muscle stem cell identity enhancing their therapeutic capacity

In skeletal muscle, muscle stem cells (MuSC) are the main cells responsible for regeneration upon injury. In diseased skeletal muscle, it would be therapeutically advantageous to replace defective MuSCs, or rejuvenate them with drugs to enhance their self-renewal and ensure long-term regenerative potential. One limitation of the replacement approach has been the inability to efficiently expand MuSCs ex vivo, while maintaining their stemness and engraftment abilities. Herein, we show that inhibition of type I protein arginine methyltransferases (PRMTs) with MS023 increases the proliferative capacity of ex vivo cultured MuSCs. Single cell RNA sequencing (scRNAseq) of ex vivo cultured MuSCs revealed the emergence of subpopulations in MS023-treated cells which are defined by elevated Pax7 expression and markers of MuSC quiescence, both features of enhanced self-renewal. Furthermore, the scRNAseq identified MS023-specific subpopulations to be metabolically altered with upregulated glycolysis and oxidative phosphorylation (OxPhos). Transplantation of MuSCs treated with MS023 had a better ability to repopulate the MuSC niche and contributed efficiently to muscle regeneration following injury. Interestingly, the preclinical mouse model of Duchenne muscular dystrophy had increased grip strength with MS023 treatment. Our findings show that inhibition of type I PRMTs increased the proliferation capabilities of MuSCs with altered cellular metabolism, while maintaining their stem-like properties such as self-renewal and engraftment potential

Developmental role of macrophages modeled in human pluripotent stem cell-derived intestinal tissue

Summary: Macrophages populate the embryo early in gestation, but their role in development is not well defined. In particular, specification and function of macrophages in intestinal development remain little explored. To study this event in the human developmental context, we derived and combined human intestinal organoid and macrophages from pluripotent stem cells. Macrophages migrate into the organoid, proliferate, and occupy the emerging microanatomical niches of epithelial crypts and ganglia. They also acquire a transcriptomic profile similar to that of fetal intestinal macrophages and display tissue macrophage behaviors, such as recruitment to tissue injury. Using this model, we show that macrophages reduce glycolysis in mesenchymal cells and limit tissue growth without affecting tissue architecture, in contrast to the pro-growth effect of enteric neurons. In short, we engineered an intestinal tissue model populated with macrophages, and we suggest that resident macrophages contribute to the regulation of metabolism and growth of the developing intestine

Developmental role of macrophages modeled in human pluripotent stem cell-derived intestinal tissue

Macrophages populate the embryo early in gestation, but their role in development is not well defined. In particular, specification and function of macrophages in intestinal development remain little explored. To study this event in the human developmental context, we derived and combined human intestinal organoid and macrophages from pluripotent stem cells. Macrophages migrate into the organoid, proliferate, and occupy the emerging microanatomical niches of epithelial crypts and ganglia. They also acquire a transcriptomic profile similar to that of fetal intestinal macrophages and display tissue macrophage behaviors, such as recruitment to tissue injury. Using this model, we show that macrophages reduce glycolysis in mesenchymal cells and limit tissue growth without affecting tissue architecture, in contrast to the pro-growth effect of enteric neurons. In short, we engineered an intestinal tissue model populated with macrophages, and we suggest that resident macrophages contribute to the regulation of metabolism and growth of the developing intestine

Deficiency in the metabolite receptor SUCNR1 (GPR91) leads to outer retinal lesions

International audienceAge-related macular degeneration (AMD) is a prominent cause of blindness in the Western world. To date, its molecular pathogenesis as well as the sequence of events leading to retinal degeneration remain largely ill-defined. While the invasion of choroidal neovessels in the retina is the primary mechanism that precipitates loss of sight, an earlier dry form precedes it. Here we provide the first evidence for the protective role of the Retinal Pigment Epithelium (RPE)-resident metabolite receptor, succinate receptor 1 (SUCNR1; G-Protein coupled Receptor-91 (GPR91), in preventing dry AMD-like lesions of the outer retina. Genetic analysis of 925 patients with geographic atrophy and 1199 AMD-free peers revealed an increased risk of developing geographic atrophy associated with intronic variants in theSUCNR1 gene. In mice, outer retinal expression of SUCNR1 is observed in the RPE as well as microglial cells and decreases progressively with age. Accordingly, Sucnr1-/- mice show signs of premature sub-retinal dystrophy with accumulation of oxidized-LDL, abnormal thickening of Bruch's membrane and a buildup of subretinal microglia. The accumulation of microglia in Sucnr1-deficient mice is likely triggered by the inefficient clearance of oxidized lipids by the RPE as bone marrow transfer of wild-type microglia into Sucnr1-/- mice did not salvage the patho-phenotype and systemic lipolysis was equivalent between wild-type and control mice. Our findings suggest that deficiency in SUCNR1 is a possible contributing factor to the pathogenesis of dry AMD and thus broaden our understanding of this clinically unmet need

Dietary ω-3 polyunsaturated fatty acids decrease retinal neovascularization by adipose-endoplasmic reticulum stress reduction to increase adiponectin.

Retinopathy of prematurity (ROP) is a vision-threatening disease in premature infants. Serum adiponectin (APN) concentrations positively correlate with postnatal growth and gestational age, important risk factors for ROP development. Dietary ω-3 (n-3) long-chain polyunsaturated fatty acids (ω-3 LCPUFAs) suppress ROP and oxygen-induced retinopathy (OIR) in a mouse model of human ROP, but the mechanism is not fully understood

Neuropilin-1 expression in adipose tissue macrophages protects against obesity and metabolic syndrome

Neuropilin-1–expressing adipose tissue macrophages are critical mediators of protective inflammation during weight gain.</jats:p