Kir4.2 Potassium Channels in Retinal Pigment Epithelial Cells In Vitro: Contribution to Cell Viability and Proliferation, and Down-Regulation by Vascular Endothelial Growth Factor.

Dedifferentiation and proliferation of retinal pigment epithelial (RPE) cells are characteristics of retinal diseases. Dedifferentiation is likely associated with changes of inwardly rectifying potassium (Kir) channels. The roles of Kir4.

Morphology of foveal hypoplasia: Hyporeflective zones in the Henle fiber layer of eyes with high-grade foveal hypoplasia.

Background: Foveal hypoplasia is characterized by the persistance of inner retinal layers at the macular center. We evaluated using spectral-domain optical coherence tomography (SD-OCT) morphological parameters of the macular center of eyes with foveal hypoplasia and describe the presence of hyporeflective zones in the Henle fiber layer (HFL) of eyes with high-grade foveal hypoplasia.

Methods: Eyes with foveal hypoplasia were classified into two groups: high-grade foveal hypoplasia with thick inner retinal layers at the macular center (thickness above 100 μm; 16 eyes of 9 subjects) and low-grade foveal hypoplasia with thinner inner retinal layers at the macular center (thickness below 100 μm; 25 eyes of 13 subjects).

Age- and sex-related variations of individual retinal layer thickness in the foveal center of healthy eyes.

Alterations of the visual function during life are associated with changes in the morphological parameters of the outer retinal layers of the fovea. We evaluated age- and sex-related variations of the mean thicknesses of the different retinal layers at the central foveola which provides the maximal visual acuity. The vertical expansions of the following structures were measured on spectral-domain optical coherence tomographic images of 2944 healthy eyes of 1990 subjects with ages between 5 and 85 years: the total thickness of the retinal tissue, the thickness of the retinal pigment epithelium, the lengths of photoreceptors (receptor segments), photoreceptor outer segments (POS), and photoreceptor inner segments (PIS), and the thicknesses of the ellipsoid zone (EZ), myoid zone (MZ), external limiting membrane, outer nuclear layer, Henle fiber layer, and the horizontal layer of the Müller cell cone.

Hypoxic and osmotic expression of Kir2.1 potassium channels in retinal pigment epithelial cells: Contribution to vascular endothelial growth factor expression.

Retinal pigment epithelial (RPE) cells express different subtypes of inwardly rectifying potassium (Kir) channels. We investigated whether human and rat RPE cells express genes of strongly rectifying Kir2 channels. We also determined the hypoxic and hyperosmotic regulation of Kir2.

Foveal regeneration after resolution of cystoid macular edema without and with internal limiting membrane detachment: presumed role of glial cells for foveal structure stabilization.

Aim: To document with spectral-domain optical coherence tomography the morphological regeneration of the fovea after resolution of cystoid macular edema (CME) without and with internal limiting membrane (ILM) detachment and to discuss the presumed role of the glial scaffold for foveal structure stabilization.

Methods: A retrospective case series of 38 eyes of 35 patients is described. Of these, 17 eyes of 16 patients displayed foveal regeneration after resolution of CME, and 6 eyes of 6 patients displayed CME with ILM detachment.

Müller cells and astrocytes in tractional macular disorders.

Tractional deformations of the fovea mainly arise from an anomalous posterior vitreous detachment and contraction of epiretinal membranes, and also occur in eyes with cystoid macular edema or high myopia. Traction to the fovea may cause partial- and full-thickness macular defects. Partial-thickness defects are foveal pseudocysts, macular pseudoholes, and tractional, degenerative, and outer lamellar holes.

Foveal configurations with disappearance of the foveal pit in eyes with macular pucker: Presumed role of Müller cells in the formation of foveal herniation.

Many eyes with macular pucker are characterized by a centripetal displacement of the inner foveal layers which may result in a disappearance of the foveal pit. In this retrospective case series of 90 eyes with macular pucker of 90 patients, we describe using spectral-domain optical coherence tomography different foveal configurations with ectopic inner foveal layers, document the relationship between posterior vitreous detachment (PVD) and idiopathic epiretinal membrane (ERM) formation and spontaneous and postoperative morphological alterations of the fovea, and propose an active role of Müller cells in the development of foveal herniation. We found that ERM were formed during or after partial perifoveal PVD, or after foveal deformations caused by tissue edema.

Osmotic regulation of aquaporin-8 expression in retinal pigment epithelial cells in vitro: Dependence on K channel activation.

Purpose: The expression of aquaporin-8 (), which plays a crucial role in the maintenance of the cellular fluid and electrolyte balance, was shown to be increased in RPE cells under hyperosmotic conditions. The aim of the present study was to investigate the mechanisms of hyperosmotic gene expression and the localization of AQP8 in cultured human RPE cells.

Methods: Hyperosmolarity was produced with the addition of 100 mM NaCl or 200 mM sucrose.

Degenerative lamellar macular holes: tractional development and morphological alterations.

Purpose: The development of degenerative lamellar macular holes (DLH) is largely unclear. This study was aimed at documenting with spectral-domain optical coherence tomography the tractional development and morphological alterations of DLH.

Methods: A retrospective case series of 44 eyes of 44 patients is described.

Different modes of full-thickness macular hole formation.

Full-thickness macular holes (FTMH) are an important cause of visual deterioration. However, different modes of FTMH formation are less investigated. It is also not clear whether the development of edematous cysts contributes to FTMH formation.

Morphology of partial-thickness macular defects: presumed roles of Müller cells and tissue layer interfaces of low mechanical stability.

Background: The pathogenesis of partial-thickness macular defects and the role of Müller glial cells in the development of such defects are not well understood. We document the morphological characteristics of various types of partial-thickness macular defects using spectral-domain optical coherence tomography, with the focus on tractional and degenerative lamellar holes, and discuss possible pathogenic mechanisms.

Methods: A retrospective case series of 61 eyes of 61 patients with different types of partial-thickness macular defects is described.

Two different populations of Müller cells stabilize the structure of the fovea: an optical coherence tomography study.

Purpose: To document with spectral-domain optical coherence tomography the structural stabilization of the fovea and the sealing of outer macular defects by Müller cells.

Methods: A retrospective case series of 45 eyes of 34 patients is described.

Results: In cases of a cystic disruption of the foveola as in macular telangiectasia type 2 and vitreomacular traction, the Müller cell cone provides the structural stability of the fovea.

Osmotic and hypoxic induction of osteopontin in retinal pigment epithelial cells: Involvement of purinergic receptor signaling.

Purpose: Osteopontin (OPN) is a neuroprotective factor in the retina that improves photoreceptor survival. The aim of the present study was to investigate whether human RPE cells express and respond to OPN.

Methods: Hypoxia and chemical hypoxia were induced by cell culture in 0.

Different modes of foveal regeneration after closure of full-thickness macular holes by (re)vitrectomy and autologous platelet concentrate.

Aim: To describe using spectral-domain optical coherence tomography the regeneration of the foveal morphology after pars plana (re)vitrectomy surgery and gas tamponade combined with injection of autologous platelet concentrate to treat full-thickness macular holes, and to describe different anatomical outcome.

Methods: A retrospective case series of 8 eyes of 8 patients was described.

Results: In all cases investigated, the platelet-assisted closure of macular holes was associated with a rapid resolution of cystic cavities in the foveal walls.

Glia of the human retina.

The human retina contains three types of glial cells: microglia and two types of macroglia, astrocytes and Müller cells. Macroglia provide homeostatic and metabolic support to photoreceptors and neurons required for neuronal activity. The fovea, the site of the sharpest vision which is astrocyte- and microglia-free, contains two populations of Müller glia: cells which form the Müller cell cone in the foveola and z-shaped Müller cells of the foveal walls.

Spontaneous closure of small full-thickness macular holes: Presumed role of Müller cells.

Purpose: To document with spectral domain optical coherence tomography the formation and spontaneous closure of small full-thickness macular holes and to propose the active role of Müller cells in macular hole closure.

Methods: A retrospective case series of five patients with spontaneous closure of macular holes is reviewed. In one patient, foveal images were recorded over a period of 18 months.

Osmotic induction of cyclooxygenase-2 in RPE cells: Stimulation of inflammasome activation.

Purpose: Systemic hypertension is a risk factor of age-related macular degeneration, a disease associated with chronic retinal inflammation. The main cause of acute hypertension in the elderly is consumption of dietary salt (NaCl) resulting in increased extracellular osmolarity. The aim of the present study was to determine whether extracellular osmolarity regulates the expression of cyclooxygenase () genes in cultured human retinal pigment epithelial (RPE) cells, and whether COX activity is involved in mediating the osmotic expression of key inflammatory ( and ) and angiogenic factor () genes.

Structure and function of the bird fovea.

The cellular structure and functional relevance of the bird fovea are still incompletely understood. This review gives an overview of the cellular composition of the bird fovea, with special regard to Müller glial cells that provide the mechanical stability of the foveal tissue. A survey of previous data shows that the visual acuity of different bird groups (with the exception of owls) depends on the eye size, while the shape of the foveal pit does not correlate with the visual acuity.

Cone-to-Müller cell ratio in the mammalian retina: A survey of seven mammals with different lifestyle.

Mammalian retinal glial (Müller) cells are known to guide light through the inner retina to photoreceptors (Franze et al., 2007; Proc Natl Acad Sci U S A 104:8287-8292). It was shown that Müller cells transmit predominantly red-green and less violet-blue light (Labin et al.

Hypoxic expression of NLRP3 and VEGF in cultured retinal pigment epithelial cells: contribution of P2Y receptor signaling.

Retinal hypoxia is a major condition of the chronic inflammatory disease age-related macular degeneration. Extracellular ATP is a danger signal which is known to activate the NLRP3 inflammasome in various cell systems. We investigated in cultured human retinal pigment epithelial (RPE) cells whether hypoxia alters the expression of inflammasome-associated genes and whether purinergic receptor signaling contributes to the hypoxic expression of key inflammatory (NLRP3) and angiogenic factor (VEGF) genes.

Activator protein-1 contributes to the NaCl-induced expression of VEGF and PlGF in RPE cells.

Purpose: Systemic hypertension is a risk factor of neovascular age-related macular degeneration; consumption of dietary salt resulting in extracellular hyperosmolarity is a main cause of hypertension. Extracellular hyperosmolarity was shown to induce expression of angiogenic growth factors, such as vascular endothelial growth factor (VEGF) and placental growth factor (PlGF), in RPE cells. The aim of the present study was to determine whether the hyperosmotic expression of growth factor genes in RPE cells is mediated by activator protein-1 (AP-1), and whether c-Fos and c-Jun genes are regulated by extracellular osmolarity.

Osmotic and hypoxic induction of the complement factor C9 in cultured human retinal pigment epithelial cells: Regulation of VEGF and NLRP3 expression.

Purpose: Variants of complement factor genes, hypoxia and oxidative stress of the outer retina, and systemic hypertension affect the risk of age-related macular degeneration. Hypertension often results from the high intake of dietary salt that increases extracellular osmolarity. We determined the effects of extracellular hyperosmolarity, hypoxia, and oxidative stress on the expression of complement genes in cultured (dedifferentiated) human RPE cells and investigated the effects of C9 siRNA and C9 protein on RPE cells.

drusen model - three-dimensional spheroid culture of retinal pigment epithelial cells.

Age-related macular degeneration (AMD) is a leading cause of blindness in people over 50 years of age in many developed countries. Drusen are yellowish extracellular deposits beneath retinal pigment epithelium (RPE) found in aging eyes and considered as a biomarker of AMD. However, the biogenesis of drusen has not been elucidated.

Müller glial cells contribute to dim light vision in the spectacled caiman (Caiman crocodilus fuscus): Analysis of retinal light transmission.

In this study, we show the capability of Müller glial cells to transport light through the inverted retina of reptiles, specifically the retina of the spectacled caimans. Thus, confirming that Müller cells of lower vertebrates also improve retinal light transmission. Confocal imaging of freshly isolated retinal wholemounts, that preserved the refractive index landscape of the tissue, indicated that the retina of the spectacled caiman is adapted for vision under dim light conditions.

Retinal adaptation to dim light vision in spectacled caimans (Caiman crocodilus fuscus): Analysis of retinal ultrastructure.

It has been shown that mammalian retinal glial (Müller) cells act as living optical fibers that guide the light through the retinal tissue to the photoreceptor cells (Agte et al., 2011; Franze et al., 2007).