Proliferation Of Retinal Glial Cells Research Articles

Massive retinal gliosis mimicking an intraocular neoplasm

Background: Massive retinal gliosis (MRG) refers to a pseudoneoplastic proliferation of retinal glial cells.1 MRG is associated with trauma, phthisis bulbi, microphthalmia, and retinal detachment.1 MRG has overlapping microscopic features with other entities; namely: astrocytic lesions of tuberous sclerosis, retinoblastoma, choroidal melanoma, medulloepithelioma, and large schwannomas.2

Circular RNA-ZNF609 regulates retinal neurodegeneration by acting as miR-615 sponge.

Glaucoma is a major cause of visual impairment characterized by progressive retinal neurodegeneration. Circular RNAs are a class of endogenous noncoding RNAs that regulate gene expression in eukaryotes. In this study, we investigated the role of cZNF609 in retinal neurodegeneration induced by glaucoma.Methods: qRT-PCR and Sanger sequencing were conducted to detect cZNF609 expression pattern during retinal neurodegeneration. Immunofluorescence staining was conducted to detect the effect of cZNF609 silencing on retinal neurodegeneration in vivo. MTT assay, Ki67 staining, and PI staining were conducted to detect the effect of cZNF609 silencing on retinal glial cells and RGC function in vitro. Bioinformatics analysis, RNA pull-down assays, and in vitro studies were conducted to reveal the mechanism of cZNF609-mediated retinal neurodegeneration.Results: cZNF609 expression was significantly up-regulated during retinal neurodegeneration. cZNF609 silencing reduced retinal reactive gliosis and glial cell activation, and facilitated RGC survival in vivo. cZNF609 silencing directly regulated Müller cell function but indirectly regulated RGC function in vitro. cZNF609 acted as an endogenous miR-615 sponge to sequester and inhibit miR-615 activity, which led to increased METRN. METRN overexpression could partially rescue cZNF609 silencing-mediated inhibitory effects on retinal glial cell proliferation.Conclusion: Intervention of cZNF609 expression is a promising therapeutic strategy for retinal neurodegeneration.

The inhibitory effects of baicalein on overexpression of proline hydroxylase 2 in hypoxia-induced retinal glial cells

Background Proline hydroxylase 2 (PHD2) is a degrading enzyme of hypoxia-inducible factor-1α (HIF-1α) and can regulate the expression of vascular endothelial growth factor (VEGF) and erythropoietin that promote hypoxia-induced blood vessel generation.Baicalein is an inhibitor of PHD2.Understanding the inhibitory effects of baicalein on overexpression of PHD2 in hypoxia-induced retinal glial cells is helpful for elucidating the pathogenesis of the ocular nevascular diseases. Objective This study aimed to observe the expression change of PHD2 in hypoxia-induced retinal glial cells and explore the inhibition of baicalein on PHD2. Methods The study protocol was approved by Experimental Animal Ethic Committee.Retinal glial cells were isolated from SPF neonatal SD rats (within 48 hours) and primarily cultured in DEME by explant cell culture.Cultured cells were identified by immunofluorescence staining of glial fibrillary acidic protein.The cells were divided into normal control group, CoCl2 group and CoCl2+ baicalein group.The cells in the normal control group were cultured in the conventional medium, and 200 μmol/L CoCl2 was added in the medium to establish the hypoxia cell models in the CoCl2 group, and 200 μmol/L CoCl2 and 50 μmol/L baicalein were added in the medium in the CoCl2+ baicalein group.The proliferation (absorbancy) of the cells was detected by cell counting kit-8 (CCK-8). The expression of PHD2 and VEGF in the cells was detected and located using immunofluorescence staining.The expressions of PHD2 mRNA and VEGF mRNA and their proteins in the cells were assayed by real-time quantitative PCR and Western blot, respectively. Results The proliferation (absorbancy) of the cells was significantly different among the groups (F=132.05, P=0.00), and the absorbancy was considerably increased in the CoCl2 group compared with normal control group and CoCl2+ baicalein group, with significant differences between the groups (both at P<0.01). Immunofluorescence staining showed that the PHD2 and VEGF were weakly expressed in the cells of the normal control group, and the expression intensity was high in the CoCl2 group.The expression intensities of PHD2 and VEGF in the cells were weakened in the CoCl2+ baicalein group compared with those of the CoCl2 group.The relative expression levels of PHD2 mRNA were 0.366±0.034, 0.894±0.015 and 0.445±0.017 and those of PHD2 protein were 131.27±2.61, 140.12±4.29, 133.14±2.11; those of VEGF mRNA were 1.346±0.008, 3.465±0.048 and 2.264±0.073 and those of VEGF protein were 532.25±19.92, 601.13±10.21, 537.34±5.96 in the normal control group, CoCl2 group and CoCl2+ baicalein group, showing significant differences among the three groups (PHD2: F=905.89, 43.18, both at P<0.01.VEGF: F=27.13, 185.79, both at P<0.01), and the relative expression levels of PHD2 and VEGF mRNA and protein in the CoCl2group were higher than those in the normal control group and CoCl2+ baicalein group (all at P<0.01). Conclusions Hypoxia stimulates the proliferation of retinal glial cells and increase the expression of PHD2 and VEGF.Baicalein can effectively inhibit the overexpression of PHD2 and VEGF in retinal glial cells and proliferation of retinal glial cells induced by hypoxia.PHD2 is a potential provention and treatment target of hypoxia-induced retinal neovascularization. Key words: Proline hydroxylase 2; Hypoxia; Retinal glial cells; Vascular endothelial growth factor; Proliferation; Baicalein

Neuropeptide Y-evoked proliferation of retinal glial (Muller) cells.

Glial cells in human retinas and in fibrocellular membranes from patients with proliferative vitreoretinopathy (PVR) have been described to upregulate their expression of Y1 receptors for neuropeptide Y (NPY) (Soler et al.: Glia 39:320, 2002). However, it is unknown whether Y1 receptor activation causes proliferation of retinal glial cells. We investigated whether NPY exerts a proliferation-stimulating effect on retinal glial cells, and compared the NPY-evoked signaling with the signaling of purinergic P2Y receptors. Proliferation assays using bromodeoxyuridine were carried out on primarily cultured Muller glial cells of the guinea pig, in the absence and presence of blockers of Y1 receptors, of receptor tyrosine kinases (RTKs), of mitogen-activated protein kinases (MAPKs) and of phosphatidylinositol-3 kinase (PI3K). NPY exerted a biphasic effect on Muller cell proliferation. At low concentrations (0.1 ng/ml and 1 ng/ml) it decreased the proliferation rate of the cells, while at higher concentration (100 ng/ml) it increased Muller cell proliferation. The NPY-evoked proliferation was mediated by Y1 receptor stimulation and by activation of the p44/p42 MAPKs and partially of the p38 MAPK. Moreover, Y1 receptor-induced activation of PI3K as well as transactivations of the platelet-derived and the epidermal growth factor RTKs were necessary for full mitogenic effect of NPY. Y1 and P2Y receptors share partially common signal transduction pathways in Muller cells. It is suggested that NPY may be involved in stimulation of retinal glial cell proliferation during PVR when it is released at higher amounts into the injured retina.

Regulation of retinal glial cell proliferation by antiproliferative molecules

Glial cells normally do not proliferate in the adult retina despite the presence of glial mitogens. In this study, we examined the hypothesis that endogenous antiproliferative molecules inhibit the effects of glial mitogens. Using cultures of glial cells obtained from the adult human retina, we found that transforming growth factor beta 2 (TGF beta 2) and a metabotrophic glutamate agonist (t-ACPD) inhibit the mitogenic effects of basic fibroblast growth factor, platelet-derived growth factor, epidermal growth factor and insulin-like growth factor-1. These antiproliferative effects may involve activation of protein kinase C (PKC) since chelerythine, a specific PKC inhibitor, blocks the antiproliferative effects of TGF beta 2 and t-ACPD. Furthermore, exposure of the glia to a phorbol ester mimics the inhibitory effects of TGF beta 2 or t-ACPD. Although TGF beta 2 and t-ACPD markedly inhibit a number of mitogens, they do not alter the mitogenic response of retinal glia to thrombin and glutamate. A common characteristic of the mitogens sensitive to TGF beta 2 or t-ACPD is activation of tyrosine kinase-linked receptors. In contrast, thrombin acts at a G-protein-linked receptor, and glutamate stimulates retinal glial proliferation via activation of an NMDA receptor. It appears that TGF beta 2 and t-ACPD may selectively inhibit retinal glial mitogenesis mediated by activation of tyrosine kinase-linked receptors. Our experiments support the idea that endogenous antiproliferative molecules play a role in preventing glial proliferation in the retina.