Cells In Age-related Macular Degeneration Research Articles

The Role of Retinal Pigment Epithelial Cells in Age-Related Macular Degeneration: Phagocytosis and Autophagy.

Age-related macular degeneration (AMD) causes vision loss in the elderly population. Dry AMD leads to the formation of Drusen, while wet AMD is characterized by cell proliferation and choroidal angiogenesis. The retinal pigment epithelium (RPE) plays a key role in AMD pathogenesis. In particular, helioreceptor renewal depends on outer segment phagocytosis of RPE cells, while RPE autophagy can protect cells from oxidative stress damage. However, when the oxidative stress burden is too high and homeostasis is disturbed, the phagocytosis and autophagy functions of RPE become damaged, leading to AMD development and progression. Hence, characterizing the roles of RPE cell phagocytosis and autophagy in the pathogenesis of AMD can inform the development of potential therapeutic targets to prevent irreversible RPE and photoreceptor cell death, thus protecting against AMD.

Investigation of the effect of TNF-α on damage to retinal pigment epithelial cells in age-related macular degeneration

Oxidative stress alters cellular homeostasis and elicits a cellular response that depends on the severity and type of damage: some cells activate defense mechanisms designed to ensure survival; the other, provided that the defense mechanisms are inhibited, triggers alternative signaling pathways that lead to apoptosis, necrosis, pyroptosis, autophagy, and so on. However, the exact cause of such damage and induction of oxidative stress, including the associated oxidative effects around pigment epithelial cells in the context of the onset and progression of age-related macular degeneration – one of the world’s most common eye diseases with blindness, remains unclear. Therefore, in the course of the study we turned to key biogenetic points of regulation of inflammation and apoptosis, in particular TNF. The aim of the work is to shed light on the role of TNF as a genetic determinant that can initiate and influence the course of age-related macular degeneration. For this purpose, the main pathognomonic markers of the morphological structure of the macula were determined in 291 persons with age-related macular degeneration and in 105 persons without ophthalmic pathology, using optical coherence tomography to confirm or exclude the diagnosis of the disease. To detect polymorphism of the TNF gene, we used the method of real-time PCR diagnostics on the BioRad CFX 96 amplifier using LiTech reagents. Statistical processing of the results was performed using Hardy-Weinberg equilibrium, Kruskal-Wallis method, logistic regression analysis and construction of the ROC curve to determine the AUC range and sensitivity and specificity values. The study revealed a significant difference in the distribution of mutant genotypes between patients with both forms of AMD and the control group. There was also a statistically significant effect of mutant allele A on the development of both "dry" (OR = 3.40; 95.0 %; CI = 1.90-6.07, p<0.001) and "wet" form of AMD (OR = 4.78; 95.0 % CI 2.65-8.64, p<0.001), and in the analysis of mutant genotypes it was found that the GA genotype increases the chances of "dry" and "wet" forms of the disease by 3.13 and 4.74 times, respectively, while AA – 5 times, regardless of the form of the disease. confirms the influence of TNF gene polymorphism on the occurrence and progression of age-related macular degeneration. In the analysis of ROC-curves and AUC regions, it was found that all mutant genotypes have a significant effect on the occurrence of age-related macular degeneration (p<0.05). However, the obtained values of sensitivity and specificity, especially in the AA genotype in both "dry" (17.9 % and 95.8 %, respectively) and "wet" (18.2 % and 95.8 %, respectively) forms of age-related macular degeneration indicate a low chance of error-free confirmation of the diagnosis. a disease that may be associated with multifactorial disease and requires further research.

Circulating endothelial and progenitor cells in age-related macular degeneration.

To evaluate circulating endothelial and circulating progenitor cells as biomarkers in age-related macular degeneration patients (both exudative and atrophic forms) in order to establish the possible clinical implication of their assessment. We have enrolled 44 age-related macular degeneration patients: 22 patients with a recently diagnosed exudative (neovascular) form (Group A) and 22 patients with an atrophic (dry) form (Group B). The control group consisted of 22 age and sex-matched healthy subjects (Group C). The number of circulating endothelial progenitor cells (CD34+/KDR+, CD133+/KDR+, and CD34+/KDR+/CD133+), circulating progenitor cells (CD34+, CD133+, and CD34+/CD133+), and circulating endothelial cells were determined in the peripheral venous blood samples by flow cytometry. Neovascular age-related macular degeneration patients were evaluated at baseline and 4 weeks after a loading phase of three consequent intravitreal injections of ranibizumab. Comparing age-related macular degeneration patients with the control group, endothelial progenitor cell and circulating progenitor cell levels were not significantly different, while age-related macular degeneration patients showed significantly higher levels of circulating endothelial cells (p = 0.001). Anti-vascular endothelial growth factor treatment with intravitreal ranibizumab was associated with a significant reduction of endothelial progenitor cell levels, with no significant influence on circulating progenitor cells and circulating endothelial cells. We reported higher levels of circulating endothelial cells in age-related macular degeneration patients in comparison with the control group, thereby supporting the hypothesis of an involvement of endothelial dysregulation in the age-related macular degeneration and a reduction of the endothelial progenitor cell level in neovascular age-related macular degeneration patients after three intravitreal injections of ranibizumab.

Evaluation of intraretinal migration of retinal pigment epithelial cells in age-related macular degeneration using polarimetric imaging

The purpose of the present study was to evaluate the intraretinal migration of the retinal pigment epithelium (RPE) cells in age-related macular degeneration (AMD) using polarimetry. We evaluated 155 eyes at various AMD stages. Depolarized light images were computed using a polarization-sensitive scanning laser ophthalmoscope (PS-SLO), and the degree of polarization uniformity was calculated using polarization-sensitive optical coherence tomography (OCT). Each polarimetry image was compared with the corresponding autofluorescence (AF) images at 488 nm (SW-AF) and at 787 nm (NIR-AF). Intraretinal RPE migration was defined by the presence of depolarization at intraretinal hyperreflective foci on PS-SLO and PS-OCT images, and by the presence of hyper-AF on both NIR-AF and SW-AF images. RPE migration was detected in 52 of 155 eyes (33.5%) and was observed in drusenoid pigment epithelial detachment (PED) and serous PED with significantly higher frequencies than in other groups (P = 0.015). The volume of the migrated RPE cluster in serous PED was significantly correlated with the volume of the PED (R2 = 0.26; P = 0.011). Overall, our results showed that intraretinal RPE migrations occurred in various AMD stages, and that they occurred more commonly in eyes with serous and drusenoid PED.

The immunomodulatory role of retinal microglial cells in age-related macular degeneration

Age-related macular degeneration (AMD) is one of the major causes of visual impairment in the elder population. Recent studies have revealed that retinal microgliacytes may play an important role in the pathogenesis of AMD, and the activation of retinal microglia could regulate the progress of AMD. The immunomodulatory role of retinal microglial cells is reviewed in this article, so as to investigate the mechanism and provide new insight for prevention and treatment of AMD.

Activation of endogenously expressed ion channels by active complement in the retinal pigment epithelium.

Defective regulation of the alternative pathway of the complement system is believed to contribute to damage of retinal pigment epithelial (RPE) cells in age-related macular degeneration. Thus we investigated the effect of complement activation on the RPE cell membrane by analyzing changes in membrane conductance via patch-clamp techniques and Ca(2+) imaging. Exposure of human ARPE-19 cells to complement-sufficient normal human serum (NHS) (25 %) resulted in a biphasic increase in intracellular free Ca(2+) ([Ca(2+)]i); an initial peak followed by sustained Ca(2+) increase. C5- or C7-depleted sera did not fully reproduce the signal generated by NHS. The initial peak of the Ca(2+) response was reduced by sarcoplasmic Ca(2+)-ATPase inhibitor thapsigargin, L-type channel blockers (R)-(+)-BayK8644 and isradipine, transient-receptor-potential (TRP) channel blocker ruthenium-red and ryanodine receptor blocker dantrolene. The sustained phase was carried by CaV1.3 L-type channels via tyrosine-phosphorylation. Changes in [Ca(2+)]I were accompanied by an abrupt hyperpolarization, resulting from a transient increase in membrane conductance, which was absent under extracellular Ca(2+)- or K(+)-free conditions and blocked by (R)-(+)-BayK8644 or paxilline, a maxiK channel inhibitor. Single-channel recordings confirmed the contribution of maxiK channels. Primary porcine RPE cells responded to NHS in a comparable manner. Pre-incubation with NHS reduced H2O2-induced cell death. In summary, in a concerted manner, C3a, C5a and sC5b-9 increased [Ca(2+)]i by ryanodine-receptor-dependent activation of L-type channels in addition to maxi-K channels and TRP channels absent from any insertion of a lytic pore.

AAV-Mediated Gene Transfer of Human X-Linked Inhibitor of Apoptosis Protects against Oxidative Cell Death in Human RPE Cells

To determine whether human X-linked inhibitor of apoptosis (XIAP) enhances the survival of cultured human retinal pigment epithelial cells exposed to H(2)O(2). ARPE-19 cells were exposed to H(2)O(2) to induce oxidative cell death. Intracellular reactive oxygen species (ROS) were measured using 2',7'-dichlorofluorescein diacetate. MTT assay was performed to quantify mitochondrial stress. Cell apoptosis was determined by TUNEL assay. Human XIAP was delivered with bicistronic expression of green fluorescent protein (GFP), using recombinant adeno-associated virus (AAV-XIAP-GFP). The null vector, containing identical sequences but without XIAP, was used as a control (AAV-NULL-GFP). Transduced cells underwent fluorescence-activated cell sorting. XIAP overexpression was examined by immunostaining and Western blot analysis. ARPE-19 cells exposed to 0.25 mM H(2)O(2) for 1 hour showed increased TUNEL staining compared with nonstressed cells (17 ± 1.4 vs. 1.8 ± 0.4 cells per 20 × field; P = 0.000006), accompanied by a significant increase in intracellular ROS (207 ± 46% vs. 100 ± 9.5%; P = 0.0002). The AAV-XIAP-GFP transduced cells had 11-fold higher XIAP expression than the AAV-NULL-GFP controls (1300 ± 126% vs. 120 ± 10%; P = 0.0006). XIAP over-expression significantly reduced the number of apoptotic cells after stress compared with the AAV-NULL-GFP controls (3.2 ± 0.6 vs. 18 ± 1.6 cells per 20 × field; P = 0.00003). Mitochondrial stress was reduced by AAV-XIAP-GFP, but did not reach a statistical significance (68 ± 3.5% vs. 74 ± 3.8%; P = 0.24). Overexpression of human XIAP protects ARPE-19 cells against H(2)O(2)-induced oxidative cell death by acting downstream on the apoptotic pathway. XIAP gene therapy using AAV may provide a means of reducing the effect of oxidative stress to RPE cells in age-related macular degeneration.

Increased Expression of Glutathione Peroxidase 4 Strongly Protects Retina from Oxidative Damage

Oxidative damage contributes to cone cell death in retinitis pigmentosa and death of rods, cones, and retinal pigmented epithelial (RPE) cells in age-related macular degeneration. In this study, we explored the strategy of overexpressing components of the endogenous antioxidant defense system to combat oxidative damage in RPE cells and retina. In transfected cultured RPE cells with increased expression of superoxide dismutase1 (SOD1) or SOD2, there was increased constitutive and stress-induced oxidative damage measured by the level of carbonyl adducts on proteins. In contrast, RPE cells with increased expression of glutathione peroxidase 1 (Gpx1) or Gpx4 did not show an increase in constitutive oxidative damage. An increase in Gpx4, and to a lesser extent Gpx1, reduced oxidative stress-induced RPE cell damage. Co-expression of Gpx4 with SOD1 or 2 partially reversed the deleterious effects of the SODs. Transgenic mice with inducible expression of Gpx4 in photoreceptors were generated, and in three models of oxidative damage-induced retinal degeneration, increased expression of Gpx4 provided strong protection of retinal structure and function. These data suggest that gene therapy approaches to augment the activity of Gpx4 in the retina and RPE should be considered in patients with retinitis pigmentosa or age-related macular degeneration.

The many possible roles of stem cells in age-related macular degeneration.

The many possible roles of stem cells in age-related macular degeneration.