Pathophysiology of age-related macular degeneration

Elovl4 5-bp deletion does not accelerate cone photoreceptor degeneration in an all-cone mouse

Mutations in the elongation of very long chain fatty acid 4 (ELOVL4) gene cause Stargardt macular dystrophy 3 (STGD3), a rare, juvenile-onset, autosomal dominant form of macular degeneration. Although several mouse models have already been generated to investigate the link between the three identified disease-causing mutations in the ELOVL4 gene, none of these models recapitulates the early-onset cone photoreceptor cell death observed in the macula of STGD3 patients. To address this specifically, we investigated the effect of mutant ELOVL4 in a mouse model with an all-cone retina. Hence, we bred mice carrying the heterozygously mutated Elovl4 gene on the R91W;Nrl^-/- all-cone background and analyzed the retinal lipid composition, morphology, and function over the course of 1 year. We observed a reduction of total phosphatidylcholine-containing very long chain-polyunsaturated fatty acids (PC-VLC-PUFAs) by 39% in the R91W;Nrl^-/-;Elovl4 mice already at 6 weeks of age with a pronounced decline of the longest forms of PC-VLC-PUFAs. Total levels of shorter-chain fatty acids (< C26) remained unaffected. However, this reduction in PC-VLC-PUFA content in the all-cone retina had no impact on morphology or function and did not accelerate retinal degeneration in the R91W;Nrl^-/-;Elovl4 mice. Taken together, mutations in the ELOVL4 gene lead to cone degeneration in humans, whereas mouse models expressing the mutant Elovl4 show predominant rod degeneration. The lack of a phenotype in the all-cone retina expressing the mutant form of the protein supports the view that aberrant function of ELOVL4 is especially detrimental for rods in mice and suggests a more subtle role of VLC-PUFAs for cone maintenance and survival.

The Role of c-Jun N-Terminal Kinase (JNK) in Retinal Degeneration and Vision Loss

c-Jun N-terminal kinase (JNK), a member of stress-induced mitogen-activated protein (MAP) kinase family, has been shown to modulate a variety of biological processes associated with neurodegenerative pathology of the retina. In particular, various retinal cell culture and animal models related to glaucoma, age-related macular degeneration (AMD), and retinitis pigmentosa indicate that JNK signaling may contribute to disease pathogenesis. This mini-review discusses the impact of JNK signaling in retinal disease, with a focus on retinal ganglion cells (RGCs), photoreceptor cells, retinal pigment epithelial (RPE) cells, and animal studies, with particular attention to modulation of JNK signaling as a potential therapeutic target for the treatment of retinal disease.

VEGF Polymorphisms Among Neovascular Age-Related Macular Degenerative Subjects in a Multiethnic Population

AIM

To determine the association of vascular endothelial growth factor (VEGF) polymorphisms with neovascular age-related macular degeneration (nAMD).

MATERIALS AND METHODS

One hundred thirty-five nAMD patients and 135 controls were recruited to determine the association of the -460 C/T, the -2549 I/D, and the +405 G/C polymorphisms with the VEGF gene. Genotyping was conducted using the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) approach, and association analyses were conducted using chi-square analysis and logistic regression analysis.

RESULTS

A significant association was observed between nAMD and the VEGF +405 G/C genotypes (p = 0.002) and alleles (odds ratio = 1.36, 95% confidence interval = 1.12-1.62, p = < 0.001) compared with the controls. This association was confirmed by logistic regression analyses, using two different genetic models (additive and dominant) resulting in p-values of p = 0.001 and p < 0.001, respectively. In addition, the dominant model of VEGF +405 G/C was also found to be at risk of the CC genotype with nAMD among subjects that were aged ≥60 years, female, of Chinese ethnicity, hypertensive, diabetic, and smokers.

CONCLUSION

With the exception of several limitations, the present study showed evidence of an association between the VEGF +405 G/C polymorphism and nAMD in Malaysian subjects.

MMP-2 Rs24386 (C-->T) gene polymorphism and the phenotype of age-related macular degeneration

AIM

To examine the MMP-2 (-1306 C/T) gene polymorphism and the phenotype characterized by soft and hard drusen of early age-related macular degeneration (AMD) and geographic atrophy of late AMD form.

METHODS

The study enrolled 850 investigations (290 AMD patients with soft and hard drusen, 34 with geographic atrophy and a random sample of the population n=526). Early AMD was classified according to the International Classification and Grading System. For geographic atrophy diagnosis the Age-Related Eye Disease Study classification was used. The potential association with single nucleotide polymorphisms on MMP-2 Rs243865 was evaluated for all patients, adjusted for age and sex. The genotyping test of MMP-2 Rs243865 (C-->T) was conducted using the real-time polymerase chain reaction method.

RESULTS

MMP-2 (-1306 C/T) C/C genotype was more frequently detected in AMD patients with hard drusen than the soft drusen or control group (66.43% vs 53.74%, vs 54.94%, P=0.047). Logistic regression analysis showed that the MMP-2 (-1306) C/C genotype increased the likelihood to develop hard drusen in AMD patients (OR=1.7, 95% CI: 1.06-2.74; P=0.028). No association between MMP-2 (-1306 C/T) gene polymorphism in patients with atrophic AMD and control group was found (54.94%, 37.64%, 7.41% vs 50%, 38.24%, 11.76%; P=0.6).

CONCLUSION

The MMP-2 Rs24386 (C-->T) polymorphism is found to be associated with the development of hard drusen in patients with AMD.

Drusen in patient-derived hiPSC-RPE models of macular dystrophies

Age-related macular degeneration (AMD) and related macular dystrophies (MDs) are a major cause of vision loss. However, the mechanisms underlying their progression remain ill-defined. This is partly due to the lack of disease models recapitulating the human pathology. Furthermore, in vivo studies have yielded limited understanding of the role of specific cell types in the eye vs. systemic influences (e.g., serum) on the disease pathology. Here, we use human induced pluripotent stem cell-retinal pigment epithelium (hiPSC-RPE) derived from patients with three dominant MDs, Sorsby's fundus dystrophy (SFD), Doyne honeycomb retinal dystrophy/malattia Leventinese (DHRD), and autosomal dominant radial drusen (ADRD), and demonstrate that dysfunction of RPE cells alone is sufficient for the initiation of sub-RPE lipoproteinaceous deposit (drusen) formation and extracellular matrix (ECM) alteration in these diseases. Consistent with clinical studies, sub-RPE basal deposits were present beneath both control (unaffected) and patient hiPSC-RPE cells. Importantly basal deposits in patient hiPSC-RPE cultures were more abundant and displayed a lipid- and protein-rich "drusen-like" composition. Furthermore, increased accumulation of COL4 was observed in ECM isolated from control vs. patient hiPSC-RPE cultures. Interestingly, RPE-specific up-regulation in the expression of several complement genes was also seen in patient hiPSC-RPE cultures of all three MDs (SFD, DHRD, and ADRD). Finally, although serum exposure was not necessary for drusen formation, COL4 accumulation in ECM, and complement pathway gene alteration, it impacted the composition of drusen-like deposits in patient hiPSC-RPE cultures. Together, the drusen model(s) of MDs described here provide fundamental insights into the unique biology of maculopathies affecting the RPE-ECM interface.

Systematic Functional Testing of Rare Variants: Contributions of CFI to Age-Related Macular Degeneration

Purpose

Genome-wide association (GWAS) and sequencing studies for AMD have highlighted the importance of coding variants at loci that encode components of the complement pathway. However, assessing the contribution of such alleles to AMD, especially when they are rare, remains coarse, in part because of the persistent challenge in establishing their functional relevance. Others and we have shown previously that rare alleles in complement factor I (CFI) can be tested functionally using a surrogate in vivo assay of retinal vascularization in zebrafish embryos. Here, we have implemented and scaled these tools to assess the overall contribution of rare alleles in CFI to AMD.

Methods

We performed targeted sequencing of CFI in 731 AMD patients, followed by replication in a second patient cohort of 511 older healthy individuals. Systematic functional testing of all alleles and post-hoc statistical analysis of functional variants was also performed.

Results

We discovered 20 rare coding nonsynonymous variants, including the previously reported G119R allele. In vivo testing led to the identification of nine variants that alter CFI; six of which are associated with hypoactive complement factor I (FI). Post-hoc analysis in ethnically matched, population controls showed six of these to be present exclusively in cases.

Conclusions

Taken together, our data argue that multiple rare and ultra-rare alleles in CFI contribute to AMD pathogenesis; they improve the precision of the assessment of the contribution of CFI to AMD; and they offer a rational route to establishing both causality and direction of allele effect for genes associated with this disorder.

An in silico model of retinal cholesterol dynamics (RCD model): insights into the pathophysiology of dry AMD

We developed an in silico mathematical model of retinal cholesterol (Ch) dynamics (RCD) to quantify the physiological rate of Ch turnover in the rod outer segment (ROS), the lipoprotein transport mechanisms by which Ch enters and leaves the outer retina, and the rates of drusen growth and macrophage-mediated clearance in dry age-related macular degeneration. Based on existing experimental data and mechanistic hypotheses, we estimated the Ch turnover rate in the ROS to be 1–6 pg/mm²/min, dependent on the rate of Ch recycling in the outer retina, and found comparable rates for LDL receptor-mediated endocytosis of Ch by the retinal pigment epithelium (RPE), ABCA1-mediated Ch transport from the RPE to the outer retina, ABCA1-mediated Ch efflux from the RPE to the choroid, and the secretion of 70 nm ApoB-Ch particles from the RPE. The drusen growth rate is predicted to increase from 0.7 to 4.2 μm/year in proportion to the flux of ApoB-Ch particles. The rapid regression of drusen may be explained by macrophage-mediated clearance if the macrophage density reaches ∼3,500 cells/mm². The RCD model quantifies retinal Ch dynamics and suggests that retinal Ch turnover and recycling, ApoB-Ch particle efflux, and macrophage-mediated clearance may explain the dynamics of drusen growth and regression.

Beta-amyloid sequelae in the eye: a critical review on its diagnostic significance and clinical relevance in Alzheimer's disease

Alzheimer's disease (AD) is a progressive and fatal neurodegenerative disorder. There is no test for its definitive diagnosis in routine clinical practice. Although phase III clinical trials have failed, only symptomatic treatment is currently available; a possible reason for these failed trials is that intervention commenced at an advanced stage of the disease. The hallmarks of an AD brain include plaques comprising of extracellular beta-amyloid (Aβ) protein aggregates and intracellular hyperphosphorylated neurofibrillary tangles of tau. Research into the preclinical diagnosis of AD has provided considerable evidence regarding early neuropathological changes using brain Aβ imaging and the cerebrospinal fluid biomarkers, Aβ and tau. Both these approaches have limitations that are expensive, invasive or time consuming and thus preclude them from screening at-risk population. Recent studies have demonstrated the presence of Aβ plaques in the eyes of AD subjects, which is positively associated with their brain Aβ burden. Thus ocular biomarkers point to a potential avenue for an earlier, relatively low-cost diagnosis in order for therapeutic interventions to be effective. Here we review the literature that spans the investigation for the presence of Aβ in aging eyes and the significance of its deposition in relation to AD pathology. We discuss clinical studies investigating in vivo imaging of Aβ in the eye and its association with brain Aβ burden and therapies that target ocular Aβ. Finally, we focus on the need to characterize AD-specific retinal Aβ to differentiate Aβ found in some eye diseases. Based on the current evidence, we conclude that integration of ocular biomarkers that can correctly predict brain Aβ burden would have an important role as a non-invasive, yet economical surrogate marker in the diagnostic process of AD.

Vandetanib and ADAM inhibitors synergistically attenuate the pathological migration of EBV-infected retinal pigment epithelial cells by regulating the VEGF-mediated MAPK pathway

The extracellular signals induced by vascular endothelial growth factor (VEGF) are implicated in choroidal neovascularization (CNV) and thus, are associated with vision-limiting complications in the human retina. Vandetanib is an oral anticancer drug that selectively inhibits the activities of VEGF receptor and epidermal growth factor receptor tyrosine kinase; however, the effects of vandetanib on VEGF in retinal pigment epithelial (RPE) cells have not yet been studied. In the present study, a combined treatment of vandetanib and a disintegrin and metalloproteinase (ADAM) protein inhibitors were used to assess the regulation of Epstein-Barr virus (EBV)-infected ARPE19 cells (ARPE19/EBV) migration as a model of CNV. Vandetanib suppressed the expression of the mesenchymal markers ADAM10 and ADAM17 in ARPE19/EBV cells, and also upregulated epithelial cell markers of the RPE cells, E-cadherin and N-cadherin. The migratory activity of ARPE19/EBV induced by VEGF was efficiently blocked by vandetanib. Furthermore, co-treatment with vandetanib and an ADAM10 inhibitor (GI254023X) or ADAM17 inhibitor (Marimastat) synergistically prevented migration and the expression of vimentin, Snail and α-smooth muscle actin by regulating extracellular signal-regulated kinase and p38 mitogen-activated protein kinase. These results suggest that a combination treatment of vandetanib and ADAM inhibitors may be developed as a novel therapeutic regimen to control retina neovascular disease.

Associations between Rs4244285 and Rs762551 gene polymorphisms and age-related macular degeneration

BACKGROUND

Age-related macular degeneration is the leading cause of blindness in elderly individuals in developed countries. The etiology and pathophysiology of age-related macular degeneration have not been elucidated yet. Knowing that the main pathological change of age-related macular degeneration is formation of drusen containing about 40% of lipids, there have been attempts to find associations between age-related macular degeneration and genes controlling lipid metabolism.

PURPOSE

To determine the frequency of CYP2C19 (G681A) Rs4244285 and CYP1A2 (-163C>A) Rs762551 genotypes in patients with age-related macular degeneration.

METHODS

The study enrolled 150 patients with early age-related macular degeneration and 296 age- and gender-matched healthy controls. The genotyping of Rs4244285 and Rs762551 was carried out by using the real-time polymerase chain reaction method.

RESULTS

The CYP1A2 (-163C>A) Rs762551 C/C genotype was more frequently detected in patients with age-related macular degeneration than in the control group (32.7% vs. 21.6%, p = 0.011) and was associated with an increased risk of developing early age-related macular degeneration (OR = 1.759, 95% CI: 1.133-2.729; p = 0.012). The CYP1A2 (-163C>A) Rs762551 C/A genotype was more frequently documented in the control group compared with patients with age-related macular degeneration (46.3% vs. 30.7%, p = 0.002) and was associated with a decreased risk of having age-related macular degeneration (OR = 0.580. 95% CI: 0.362-0.929, p = 0.023) in the co-dominant model.

CONCLUSION

The study showed that the CYP1A2 (-163C>A) Rs762551 C/C genotype was associated with an increased risk of age-related macular degeneration.

Features of Age-Related Macular Degeneration in the General Adults and Their Dependency on Age, Sex, and Smoking: Results from the German KORA Study

Age-related macular degeneration (AMD) is a vision impairing disease of the central retina characterized by early and late forms in individuals older than 50 years of age. However, there is little knowledge to what extent also younger adults are affected. We have thus set out to estimate the prevalence of early AMD features and late AMD in a general adult population by acquiring color fundus images in 2,840 individuals aged 25 to 74 years of the Cooperative Health Research in the Region of Augsburg project (KORA) in South Germany. Among the 2,546 participants with gradable images for each eye, 10.9% (n = 277) had early AMD features (applying the 9-step Age-Related Eye Disease Study Severity Scale), 0.2% (n = 6) had late AMD. Prevalence increased with age, reaching 26.3% for early AMD features and 1.9% for late AMD at the age 70+. However, signs of early AMD were found in subjects as young as 25 years, with the risk for early AMD features increasing linearly by years of age in men, and, less consistent with a linear increase, in women. Risk for early AMD features increased linearly by pack years of smoking in men, not in women, nor was there any association with other lifestyle or metabolic factors. By providing much sought-after prevalence estimates for AMD from Central Europe, our data underscores a substantial proportion of the adult population with signs of early AMD, including individuals younger than 50 years. This supports the notion that early AMD features in the young might be under-acknowledged.

ROCK Inhibition Promotes Attachment, Proliferation, and Wound Closure in Human Embryonic Stem Cell-Derived Retinal Pigmented Epithelium

Purpose

Nonexudative (dry) age-related macular degeneration (AMD), a leading cause of blindness in the elderly, is associated with the loss of retinal pigmented epithelium (RPE) cells and the development of geographic atrophy, which are areas devoid of RPE cells and photoreceptors. One possible treatment option would be to stimulate RPE attachment and proliferation to replace dying/dysfunctional RPE and bring about wound repair. Clinical trials are underway testing injections of RPE cells derived from pluripotent stem cells to determine their safety and efficacy in treating AMD. However, the factors regulating RPE responses to AMD-associated lesions are not well understood. Here, we use cell culture to investigate the role of RhoA coiled coil kinases (ROCKs) in human embryonic stem cell–derived RPE (hESC-RPE) attachment, proliferation, and wound closure.

Methods

H9 hESC were spontaneously differentiated into RPE cells. hESC-RPE cells were treated with a pan ROCK1/2 or a ROCK2 only inhibitor; attachment, and proliferation and cell size within an in vitro scratch assay were examined.

Results

Pharmacological inhibition of ROCKs promoted hESC-RPE attachment and proliferation, and increased the rate of closure of in vitro wounds. ROCK inhibition decreased phosphorylation of cofilin and myosin light chain, suggesting that regulation of the cytoskeleton underlies the mechanism of action of ROCK inhibition.

Conclusions

ROCK inhibition promotes attachment, proliferation, and wound closure in H9 hESC-RPE cells. ROCK isoforms may have different roles in wound healing.

Translational Relevance

Modulation of the ROCK-cytoskeletal axis has potential in stimulating wound repair in transplanted RPE cells and attachment in cellular therapies.

A novel fluorescence-based assay for measuring A2E removal from human retinal pigment epithelial cells to screen for age-related macular degeneration inhibitors

Age-related macular degeneration (AMD) is a common retinal disease that leads to irreversible central vision loss in the elderly population. Recent studies have identified many factors related to the development of dry AMD, such as aging, cigarette smoking, genetic predispositions, and oxidative stress, eventually inducing the accumulation of lipofuscin, which is one of the most critical risk factors. One of the major lipofuscins in retinal pigment epithelial (RPE) cells is N-retinylidene-N-retinylethanolamine (also known as A2E), a pyridinium bis-retinoid. Currently there is a lack of effective therapy to prevent or restore vision loss caused by dry AMD. Recent studies have shown that 430 nm blue light induces the oxidation of A2E and the activation of caspase-3 to subsequently cause the death of RPE cells, suggesting that removal of A2E from retinal pigment cells might be critical for preventing AMD. Here, we developed a fluorescence-labeled A2E analog (A2E-BDP) that functions similar to A2E in RPE cells, but is more sensitive to detection than A2E. A2E-BDP-based tracing of intracellular A2E will be helpful, not only for studying the accumulation and removal of A2E in human RPE cells but also for identifying possible inhibitors of AMD.

AMD-like retinopathy associated with intravenous iron

Iron accumulation in the retina is associated with the development of age-related macular degeneration (AMD). IV iron is a common method to treat iron deficiency anemia in adults, and its retinal manifestations have not hitherto been identified. To assess whether IV iron formulations can be retina-toxic, we generated a mouse model for iron-induced retinal damage. Male C57BL/6J mice were randomized into groups receiving IV iron-sucrose (+Fe) or 30% sucrose (-Fe). Iron levels in neurosensory retina (NSR), retinal pigment epithelium (RPE), and choroid were assessed using immunofluorescence, quantitative PCR, and the Perls' iron stain. Iron levels were most increased in the RPE and choroid while levels in the NSR did not differ significantly in +Fe mice compared to controls. Eyes from +Fe mice shared histological features with AMD, including Bruch's membrane (BrM) thickening with complement C3 deposition, as well as RPE hypertrophy and vacuolization. This focal degeneration correlated with areas of high choroidal iron levels. Ultrastructural analysis provided further detail of the RPE/photoreceptor outer segment vacuolization and Bruch's membrane thickening. Findings were correlated with a clinical case of a 43-year-old patient who developed numerous retinal drusen, the hallmark of AMD, within 11 months of IV iron therapy. Our results suggest that IV iron therapy may have the potential to induce or exacerbate a form of retinal degeneration. This retinal degeneration shares features with AMD, indicating the need for further study of AMD risk in patients receiving IV iron treatment.

AMD and the alternative complement pathway: genetics and functional implications

Age-related macular degeneration (AMD) is an ocular neurodegenerative disorder and is the leading cause of legal blindness in Western societies, with a prevalence of up to 8 % over the age of 60, which continues to increase with age. AMD is characterized by the progressive breakdown of the macula (the central region of the retina), resulting in the loss of central vision including visual acuity. While its molecular etiology remains unclear, advances in genetics and genomics have illuminated the genetic architecture of the disease and have generated attractive pathomechanistic hypotheses. Here, we review the genetic architecture of AMD, considering the contribution of both common and rare alleles to susceptibility, and we explore the possible mechanistic links between photoreceptor degeneration and the alternative complement pathway, a cascade that has emerged as the most potent genetic driver of this disorder.

Genetic factors associated with the development of age-related macular degeneration

Age-related macular degeneration (AMD) affects the macula and is the leading cause of significant and irreversible central visual loss. It is the most common cause of visual loss in people aged more than 60 years. This disease affects 2.5 million individuals in Europe. AMD is caused by both environmental and genetic factors. Numerous risk factors have been reported, but the pathogenesis of AMD is complex and fairly understood. Age, female gender, obesity, race, education status, family history, hyperopia, iris color, cigarette smoking, previous cataract surgery, history of cardiovascular and cerebrovascular disease, diabetes, sunlight exposure and many other factors have been shown to be associated with AMD development. Scientific evidence shows that genes may play a role in the development of nearly 3 out of 4 cases of this devastating eye disease. The genes that have been shown to be associated with AMD are genes encoding complement system components such as CFH, C2, C3, CFB, and other.

CYP4F2 (rs2108622) Gene Polymorphism Association with Age-Related Macular Degeneration

Background. Age-related macular degeneration is the leading cause of blindness in elderly individuals where aetiology and pathophysiology of age-related macular degeneration are not absolutely clear. Purpose. To determine the frequency of the genotype of rs2108622 in patients with early and exudative age-related macular degeneration. Methods. The study enrolled 190 patients with early age-related macular degeneration, 181 patients with exudative age-related macular degeneration (eAMD), and a random sample of 210 subjects from the general population (control group). The genotyping of rs2108622 was carried out using the real-time polymerase chain reaction method. Results. The analysis of rs2108622 gene polymorphism did not reveal any differences in the distribution of C/C, C/T, and T/T genotypes between the early AMD group, the eAMD group, and the control group. The CYP4F2 (1347C>T) T/T genotype was more frequent in males with eAMD compared to females (10.2% versus 0.8%; p = 0.0052); also T/T genotype was less frequently present in eAMD females compared to healthy control females (0.8% versus 6.2%; p = 0.027). Conclusion. Rs2108622 gene polymorphism had no predominant effect on the development of early AMD and eAMD. The T/T genotype was more frequent in males with eAMD compared to females and less frequently present in eAMD females compared to healthy females.

Inflammatory Cytokines Induce Expression of Chemokines by Human Retinal Cells: Role in Chemokine Receptor Mediated Age-related Macular Degeneration

Chemokine reeptor-3 (CCR-3) was shown to be associated with choroidal neovascularization (CNV) in age-related macular degeneration (AMD). AMD is a vision threatening retinal disease that affects the aging population world-wide. Retinal pigment epithelium and choroid in the posterior part of the retina are the key tissues targeted in the pathogenesis of CNV in AMD. We used human retinal pigment epithelial (HRPE) and choroidal fibroblast (HCHF) cells, prepared from aged adult human donor eyes, to evaluate the expression of major CCR-3 ligands, CCL-5, CCL -7, CCL-11,CCL-24 and CCL-26. Microarray analysis of gene expression in HRPE cells treated with inflammatory cytokine mix (ICM= IFN-γ+TNF-α+IL-1β) revealed 75 and 23-fold increase in CCL-5 and CCL-7 respectively, but not CCL-11, CCL-24 and CCL-26. Chemokine secretion studies of the production of CCL5 and CCL7 by HRPE corroborated with the gene expression analysis data. When the HRPE cells were treated with either individual cytokines or the ICM, both CCL-5 and CCL-7 were produced in a dose dependent manner. Similar to the gene expression data, the ICM did not enhance HRPE production of CCL-11, CCL-24 and CCL-26. CCL-11 and CCL-26 were increased with IL-4 treatment and this HRPE production was augmented in the presence of TNF-α and IL1β. When HCHF cells were treated with either individual cytokines or the ICM, both CCL-5 and CCL-7 were produced in a dose dependent fashion. IL-4 induced low levels of CCL-11 and CCL-26 in HCHF and this production was significantly enhanced by TNF-α. Under these conditions, neither HRPE nor HCHF were demonstrated to produce CCL-24. These data demonstrate that chronic inflammation triggers CCL-5 and CCL-7 release by HRPE and HCHF and the subsequent interactions with CCR3 may participate in pathologic processes in AMD.

Laser treatment of drusen to prevent progression to advanced age-related macular degeneration

BACKGROUND

Drusen are amorphous yellowish deposits beneath the sensory retina. People with drusen, particularly large drusen, are at higher risk of developing age-related macular degeneration (AMD). The most common complication in AMD is choroidal neovascularisation (CNV), the growth of new blood vessels in the centre of the macula. The risk of CNV is higher among people who are already affected by CNV in one eye.It has been observed clinically that laser photocoagulation of drusen leads to their disappearance and may prevent the occurrence of advanced disease (CNV or geographic atrophy) associated with visual loss.

OBJECTIVES

To examine the effectiveness and adverse effects of laser photocoagulation of drusen in AMD.

SEARCH METHODS

We searched CENTRAL (which contains the Cochrane Eyes and Vision Group Trials Register) (2015, Issue 7), Ovid MEDLINE, Ovid MEDLINE In-Process and Other Non-Indexed Citations, Ovid MEDLINE Daily, Ovid OLDMEDLINE (January 1946 to August 2015), EMBASE (January 1980 to August 2015), Latin American and Caribbean Health Sciences Literature Database (LILACS) (January 1982 to August 2015), the ISRCTN registry (www.isrctn.com/editAdvancedSearch), ClinicalTrials.gov (www.clinicaltrials.gov) and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). We did not use any date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 3 August 2015.

SELECTION CRITERIA

Randomised controlled trials (RCTs) of laser treatment of drusen in AMD in which laser treatment had been compared with no intervention or sham treatment. Two types of trials were included. Some trials studied one eye of each participant (unilateral studies); other studies recruited participants with bilateral drusen and randomised one eye to photocoagulation or control and the fellow eye to the other group.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected studies and extracted data. We pooled data from unilateral and bilateral studies using a random-effects model. For the bilateral studies, we estimated the within-person correlation coefficient from one study and assumed it was valid for the others.

MAIN RESULTS

The update of this review found two additional studies, totaling 11 studies that randomised 2159 participants (3580 eyes) and followed them up to two years, of which six studies (1454 participants) included people with one eye randomised to treatment and one to control. Studies were conducted in Australia, Europe and North America.Overall, the risk of bias in the included studies was low, particularly for the larger studies and for the primary outcome development of CNV. Photocoagulation did not reduce the development of CNV at two years' follow-up (odds ratio (OR) 1.07, 95% confidence interval (CI) 0.79 to 1.46, 11 studies, 2159 participants (3580 eyes), high quality evidence). This estimate means that, given an overall occurrence of CNV of 8.3% in the control group, we estimated an absolute risk reduction by no more than 1.4% in the laser group, according to the lower CI limit. Only two studies investigated the effect on the development of geographic atrophy and could not show a difference, but estimates were imprecise (OR 1.30, 95% CI 0.38 to 4.51, two studies, 148 participants (148 eyes), low quality evidence).Among secondary outcomes, photocoagulation led to drusen reduction (OR 9.16, 95% CI 6.28 to 13.4, three studies, 570 participants (944 eyes), high quality evidence) but was not shown to limit loss of 3 or more lines of visual acuity (OR 0.99, 95% CI 0.81 to 1.22, nine studies, 2002 participants (2386 eyes), moderate quality evidence).In a subgroup analysis, no difference could be shown for conventional visible (eight studies) versus subthreshold invisible (four studies) photocoagulation for the primary outcomes (P value = 0.29). The effect in the subthreshold group did not suggest a relevant benefit (OR 1.27, 95% CI 0.82 to 1.98). No study used micropulse subthreshold photocoagulation.No other adverse effects (apart from development of CNV, geographic atrophy or visual loss) were reported.

AUTHORS' CONCLUSIONS

The trials included in this review confirm the clinical observation that laser photocoagulation of drusen leads to their disappearance. However, treatment does not result in a reduction in the risk of developing CNV, and was not shown to limit the occurrence of geographic atrophy or visual acuity loss.Ongoing studies are being conducted to assess whether the use of extremely short laser pulses (i.e. nanosecond laser treatment) cannot only lead to drusen regression but also prevent neovascular AMD.

The Project MACULA Retinal Pigment Epithelium Grading System for Histology and Optical Coherence Tomography in Age-Related Macular Degeneration

PURPOSE

To seek pathways of retinal pigment epithelium (RPE) fate in age-related macular degeneration via a morphology grading system; provide nomenclature, visualization targets, and metrics for clinical imaging and model systems.

METHODS

Donor eyes with geographic atrophy (GA) or choroidal neovascularization (CNV) and one GA eye with previous clinical spectral-domain optical coherence tomography (SDOCT) imaging were processed for histology, photodocumented, and annotated at predefined locations. Retinal pigment epithelial cells contained spindle-shaped melanosomes, apposed a basal lamina or basal laminar deposit (BLamD), and exhibited recognizable morphologies. Thicknesses and unbiased estimates of frequencies were obtained.

RESULTS

In 13 GA eyes (449 locations), 'Shedding,' 'Sloughed,' and 'Dissociated' morphologies were abundant; 22.2% of atrophic locations had 'Dissociated' RPE. In 39 CNV eyes (1363 locations), 37.3% of locations with fibrovascular/fibrocellular scar had 'Entombed' RPE; 'Sloughed,' 'Dissociated,' and 'Bilaminar' morphologies were abundant. Of abnormal RPE, CNV and GA both had ~35% 'Sloughed'/'Intraretinal,' with more Intraretinal in CNV (9.5% vs. 1.8%). 'Shedding' cells associated with granule aggregations in BLamD. The RPE layer did not thin, and BLamD remained thick, with progression. Granule-containing material consistent with three morphologies correlated to SDOCT hyperreflective foci in the previously examined GA patient.

CONCLUSIONS

Retinal pigment epithelium morphology indicates multiple pathways in GA and CNV. Atrophic/scarred areas have numerous cells capable of transcribing genes and generating imaging signals. Shed granule aggregates, possibly apoptotic, are visible in SDOCT, as are 'Dissociated' and 'Sloughed' cells. The significance of RPE phenotypes is addressable in longitudinal, high-resolution imaging in clinic populations. Data can motivate future molecular phenotyping studies.

Inner Segment Remodeling and Mitochondrial Translocation in Cone Photoreceptors in Age-Related Macular Degeneration With Outer Retinal Tubulation

PURPOSE

To quantify impressions of mitochondrial translocation in degenerating cones and to determine the nature of accumulated material in the subretinal space with apparent inner segment (IS)-like features by examining cone IS ultrastructure.

METHODS

Human donor eyes with advanced age-related macular degeneration (AMD) were screened for outer retinal tubulation (ORT) in macula-wide, high-resolution digital sections. Degenerating cones inside ORT (ORT cones) and outside ORT (non-ORT cones) from AMD eyes and unaffected cones in age-matched control eyes were imaged using transmission electron microscopy. The distances of mitochondria to the external limiting membrane (ELM), cone IS length, and cone IS width at the ELM were measured.

RESULTS

Outer retinal tubulation and non-ORT cones lose outer segments (OS), followed by shortening of IS and mitochondria. In non-ORT cones, IS broaden. Outer retinal tubulation and non-ORT cone IS myoids become undetectable due to mitochondria redistribution toward the nucleus. Some ORT cones were found lacking IS and containing mitochondria in the outer fiber (between soma and ELM). Unlike long, thin IS mitochondria in control cones, ORT and non-ORT IS mitochondria are ovoid or reniform. Shed IS, some containing mitochondria, were found in the subretinal space.

CONCLUSIONS

In AMD, macula cones exhibit loss of detectable myoid due to IS shortening in addition to OS loss, as described. Mitochondria shrink and translocate toward the nucleus. As reflectivity sources, translocating mitochondria may be detectable using in vivo imaging to monitor photoreceptor degeneration in retinal disorders. These results improve the knowledge basis for interpreting high-resolution clinical retinal imaging.

Bicyclic [3.3.0]-Octahydrocyclopenta[c]pyrrolo Antagonists of Retinol Binding Protein 4: Potential Treatment of Atrophic Age-Related Macular Degeneration and Stargardt Disease

Antagonists of retinol-binding protein 4 (RBP4) impede ocular uptake of serum all-trans retinol (1) and have been shown to reduce cytotoxic bisretinoid formation in the retinal pigment epithelium (RPE), which is associated with the pathogenesis of both dry age-related macular degeneration (AMD) and Stargardt disease. Thus, these agents show promise as a potential pharmacotherapy by which to stem further neurodegeneration and concomitant vision loss associated with geographic atrophy of the macula. We previously disclosed the discovery of a novel series of nonretinoid RBP4 antagonists, represented by bicyclic [3.3.0]-octahydrocyclopenta[c]pyrrolo analogue 4. We describe herein the utilization of a pyrimidine-4-carboxylic acid fragment as a suitable isostere for the anthranilic acid appendage of 4, which led to the discovery of standout antagonist 33. Analogue 33 possesses exquisite in vitro RBP4 binding affinity and favorable drug-like characteristics and was found to reduce circulating plasma RBP4 levels in vivo in a robust manner (>90%).

A comparison of some organizational characteristics of the mouse central retina and the human macula

Mouse models have greatly assisted our understanding of retinal degenerations. However, the mouse retina does not have a macula, leading to the question of whether the mouse is a relevant model for macular degeneration. In the present study, a quantitative comparison between the organization of the central mouse retina and the human macula was made, focusing on some structural characteristics that have been suggested to be important in predisposing the macula to stresses leading to degeneration: photoreceptor density, phagocytic load on the RPE, and the relative thinness of Bruch’s membrane. Light and electron microscopy measurements from retinas of two strains of mice, together with published data on human retinas, were used for calculations and subsequent comparisons. As in the human retina, the central region of the mouse retina possesses a higher photoreceptor cell density and a thinner Bruch’s membrane than in the periphery; however, the magnitudes of these periphery to center gradients are larger in the human. Of potentially greater relevance is the actual photoreceptor cell density, which is much greater in the mouse central retina than in the human macula, underlying a higher phagocytic load for the mouse RPE. Moreover, at eccentricities that correspond to the peripheral half of the human macula, the rod to cone ratio is similar between mouse and human. Hence, with respect to photoreceptor density and phagocytic load of the RPE, the central mouse retina models at least the more peripheral part of the macula, where macular degeneration is often first evident.

Evaluation of topical hesperetin matrix film for back-of-the-eye delivery

PURPOSE

The goal of the present study was to develop a poly (ethylene oxide) N10 (PEO N10) based melt-cast matrix system for efficient and prolonged delivery of hesperetin (HT), a promising bioflavonoid, to the posterior segment of the eye through the topical route.

METHODS

HT film was prepared by melt-cast method using PEO N10 and cut into 4mm×2mm segments, each weighing 8mg. This film was evaluated with respect to in vitro release rates and also transmembrane delivery across Spectra/Por® membrane (MWCO: 10,000 Daltons) and isolated rabbit corneas. Ocular tissue concentrations were also determined postapplication of the film in ex vivo and in vivo models.

RESULTS

HT release from the film was determined to be about 95.3% within 2h. In vitro transcorneal flux was observed to be 0.58±0.05μg/min/cm(2) across the isolated rabbit cornea. High levels of HT were detected in the retina-choroid (RC) and vitreous humor (VH) in the ex vivo model following topical application of the film. Significant levels of HT were observed in both anterior and posterior segment ocular tissues 1h post topical application of the 10 and 20%w/w HT films on the rabbit eye. Moreover, HT was detected in the VH and RC even after 6h following topical application of the film in vivo.

CONCLUSION

The results from this study suggest that the melt-cast films can serve as a viable platform for sustained topical delivery of bioflavonoids, and other therapeutic agents, into the back-of-the eye tissues.

Morphological and physiological retinal degeneration induced by intravenous delivery of vitamin A dimers in rabbits

The eye uses vitamin A as a cofactor to sense light and, during this process, some vitamin A molecules dimerize, forming vitamin A dimers. A striking chemical signature of retinas undergoing degeneration in major eye diseases such as age-related macular degeneration (AMD) and Stargardt disease is the accumulation of these dimers in the retinal pigment epithelium (RPE) and Bruch's membrane (BM). However, it is not known whether dimers of vitamin A are secondary symptoms or primary insults that drive degeneration. Here, we present a chromatography-free method to prepare gram quantities of the vitamin A dimer, A2E, and show that intravenous administration of A2E to the rabbit results in retinal degeneration. A2E-damaged photoreceptors and RPE cells triggered inflammation, induced remolding of the choroidal vasculature and triggered a decline in the retina's response to light. Data suggest that vitamin A dimers are not bystanders, but can be primary drivers of retinal degeneration. Thus, preventing dimer formation could be a preemptive strategy to address serious forms of blindness.

Ocular surface temperature in age-related macular degeneration

Background. The aim of this study is to investigate the ocular thermographic profiles in age-related macular degeneration (AMD) eyes and age-matched controls to detect possible hemodynamic abnormalities, which could be involved in the pathogenesis of the disease. Methods. 32 eyes with early AMD, 37 eyes with atrophic AMD, 30 eyes affected by untreated neovascular AMD, and 43 eyes with fibrotic AMD were included. The control group consisted of 44 healthy eyes. Exclusion criteria were represented by any other ocular diseases other than AMD, tear film abnormalities, systemic cardiovascular abnormalities, diabetes mellitus, and a body temperature higher than 37.5°C. A total of 186 eyes without pupil dilation were investigated by infrared thermography (FLIR A320). The ocular surface temperature (OST) of three ocular points was calculated by means of an image processing technique from the infrared images. Two-sample t-test and one-way analysis of variance (ANOVA) test were used for statistical analyses. Results. ANOVA analyses showed no significant differences among AMD groups (P value >0.272). OST in AMD patients was significantly lower than in controls (P > 0.05). Conclusions. Considering the possible relationship between ocular blood flow and OST, these findings might support the central role of ischemia in the pathogenesis of AMD.

Squamosamide derivative FLZ protects retinal pigment epithelium cells from oxidative stress through activation of epidermal growth factor receptor (EGFR)-AKT signaling

Reactive oxygen species (ROS)-mediated retinal pigment epithelium (RPE) cell apoptosis is attributed to age-related macular degeneration (AMD) pathogenesis. FLZ, a novel synthetic squamosamide derivative from a Chinese herb, Annona glabra, has displayed significant cyto-protective activity. In the current study, we explored the pro-survival effect of FLZ in oxidative stressed-RPE cells and studied the underlying signaling mechanisms. Our results showed that FLZ attenuated hydrogen peroxide (H2O2)-induced viability decrease and apoptosis in the RPE cell line (ARPE-19 cells) and in primary mouse RPE cells. Western blotting results showed that FLZ activated AKT signaling in RPE cells. The AKT-specific inhibitor, MK-2206, the phosphoinositide 3-kinase (PI3K)/AKT pan inhibitor, wortmannin, and AKT1-shRNA (short hairpin RNA) depletion almost abolished FLZ-mediated pro-survival/anti-apoptosis activity. We discovered that epidermal growth factor receptor (EGFR) trans-activation mediated FLZ-induced AKT activation and the pro-survival effect in RPE cells, and the anti-apoptosis effect of FLZ against H2O2 was inhibited by the EGFR inhibitor, PD153035, or by EGFR shRNA-knockdown. In conclusion, FLZ protects RPE cells from oxidative stress through activation of EGFR-AKT signaling, and our results suggest that FLZ might have therapeutic values for AMD.

Design, synthesis, and evaluation of nonretinoid retinol binding protein 4 antagonists for the potential treatment of atrophic age-related macular degeneration and Stargardt disease

Accumulation of lipofuscin in the retina is associated with pathogenesis of atrophic age-related macular degeneration and Stargardt disease. Lipofuscin bisretinoids (exemplified by N-retinylidene-N-retinylethanolamine) seem to mediate lipofuscin toxicity. Synthesis of lipofuscin bisretinoids depends on the influx of retinol from serum to the retina. Compounds antagonizing the retinol-dependent interaction of retinol-binding protein 4 (RBP4) with transthyretin in the serum would reduce serum RBP4 and retinol and inhibit bisretinoid formation. We recently showed that A1120 (3), a potent carboxylic acid based RBP4 antagonist, can significantly reduce lipofuscin bisretinoid formation in the retinas of Abca4^–/– mice. As part of the NIH Blueprint Neurotherapeutics Network project we undertook the in vitro exploration to identify novel conformationally flexible and constrained RBP4 antagonists with improved potency and metabolic stability. We also demonstrate that upon acute and chronic dosing in rats, 43, a potent cyclopentyl fused pyrrolidine antagonist, reduced circulating plasma RBP4 protein levels by approximately 60%.

ROCK Inhibition Extends Passage of Pluripotent Stem Cell-Derived Retinal Pigmented Epithelium

Human embryonic stem cells (hESCs) offer a potentially unlimited supply of cells for emerging cell-based therapies. Unfortunately, the process of deriving distinct cell types can be time consuming and expensive. In the developed world, age-related macular degeneration (AMD) is the leading cause of blindness in the elderly, with more than 7.2 million people afflicted in the U.S. alone. Both hESC-derived retinal pigmented epithelium (hESC-RPE) and induced pluripotent stem cell-derived RPE (iPSC-RPE) are being developed for AMD therapies by multiple groups, but their potential for expansion in culture is limited. To attempt to overcome this passage limitation, we examined the involvement of Rho-associated, coiled-coil protein kinase (ROCK) in hESC-RPE and iPSC-RPE culture. We report that inhibiting ROCK1/2 with Y-27632 allows extended passage of hESC-RPE and iPSC-RPE. Microarray analysis suggests that ROCK inhibition could be suppressing an epithelial-to-mesenchymal transition through various pathways. These include inhibition of key ligands of the transforming growth factor-β pathway (TGFB1 and GDF6) and Wnt signaling. Two important processes are affected, allowing for an increase in hESC-RPE expansion. First, ROCK inhibition promotes proliferation by inducing multiple components that are involved in cell cycle progression. Second, ROCK inhibition affects many pathways that could be converging to suppress RPE-to-mesenchymal transition. This allows hESC-RPE to remain functional for an extended but finite period in culture.

2-ethylpyridine, a cigarette smoke component, causes mitochondrial damage in human retinal pigment epithelial cells in vitro

Purpose:

Our goal was to identify the cellular and molecular effects of 2-ethylpyridine (2-EP, a component of cigarette smoke) on human retinal pigment epithelial cells (ARPE-19) in vitro.

Materials and Methods:

ARPE-19 cells were exposed to varying concentrations of 2-EP. Cell viability (CV) was measured by a trypan blue dye exclusion assay. Caspase-3/7 and caspase-9 activities were measured by fluorochrome assays. The production of reactive oxygen/nitrogen species (ROS/RNS) was detected with a 2’,7’-dichlorodihydrofluorescein diacetate dye assay. The JC-1 assay was used to measure mitochondrial membrane potential (ΔΨm). Mitochondrial redox potential was measured using a RedoxSensor Red kit and mitochondria were evaluated with Mitotracker dye.

Results:

After 2-EP exposure, ARPE-19 cells showed significantly decreased CV, increased caspase-3/7 and caspase-9 activities, elevated ROS/RNS levels, decreased ΔΨm value and decreased redox fluorescence when compared with control samples.

Conclusions:

These results show that 2-EP treatment induced cell death by caspase-dependent apoptosis associated with an oxidative stress and mitochondrial dysfunction. These data represent a possible mechanism by which smoking contributes to age-related macular degeneration and other retinal diseases and identify mitochondria as a target for future therapeutic interventions.

Emerging roles for nuclear receptors in the pathogenesis of age-related macular degeneration

Age-related macular degeneration (AMD) is the leading cause of vision loss in the elderly in the Western world. Over the last 30 years, our understanding of the pathogenesis of the disease has grown exponentially thanks to the results of countless epidemiology, genetic, histological, and biochemical studies. This information, in turn, has led to the identification of multiple biologic pathways potentially involved in development and progression of AMD, including but not limited to inflammation, lipid and extracellular matrix dysregulation, and angiogenesis. Nuclear receptors are a superfamily of transcription factors that have been shown to regulate many of the pathogenic pathways linked with AMD and as such they are emerging as promising targets for therapeutic intervention. In this review, we will present the fundamental phenotypic features of AMD and discuss our current understanding of the pathobiological disease mechanisms. We will introduce the nuclear receptor superfamily and discuss the current literature on their effects on AMD-related pathophysiology.

The generation of induced pluripotent stem cells for macular degeneration as a drug screening platform: identification of curcumin as a protective agent for retinal pigment epithelial cells against oxidative stress

Age-related macular degeneration (AMD) is one retinal aging process that may lead to irreversible vision loss in the elderly. Its pathogenesis remains unclear, but oxidative stress inducing retinal pigment epithelial (RPE) cells damage is perhaps responsible for the aging sequence of retina and may play an important role in macular degeneration. In this study, we have reprogrammed T cells from patients with dry type AMD into induced pluripotent stem cells (iPSCs) via integration-free episomal vectors and differentiated them into RPE cells that were used as an expandable platform for investigating pathogenesis of the AMD and in-vitro drug screening. These patient-derived RPEs with the AMD-associated background (AMD-RPEs) exhibited reduced antioxidant ability, compared with normal RPE cells. Among several screened candidate drugs, curcumin caused most significant reduction of ROS in AMD-RPEs. Pre-treatment of curcumin protected these AMD-RPEs from H2O2-induced cell death and also increased the cytoprotective effect against the oxidative stress of H2O2 through the reduction of ROS levels. In addition, curcumin with its versatile activities modulated the expression of many oxidative stress-regulating genes such as PDGF, VEGF, IGFBP-2, HO1, SOD2, and GPX1. Our findings indicated that the RPE cells derived from AMD patients have decreased antioxidative defense, making RPE cells more susceptible to oxidative damage and thereby leading to AMD formation. Curcumin represented an ideal drug that can effectively restore the neuronal functions in AMD patient-derived RPE cells, rendering this drug an effective option for macular degeneration therapy and an agent against aging-associated oxidative stress.

Resveratrol Suppresses Expression of VEGF by Human Retinal Pigment Epithelial Cells: Potential Nutraceutical for Age-related Macular Degeneration

Age-related macular degeneration (AMD) is a sight threating retinal eye disease that affects millions of aging individuals world-wide. Choroid-retinal pigment epithelium (RPE)-neuroretina axis in the posterior compartment of the eye is the primary site of AMD pathology. There are compelling evidence to indicate association of vascular endothelial growth factors (VEGF) to AMD. Here, we report the inhibitory actions of resveratrol (RSV) on inflammatory cytokine, TGF-β and hypoxia induced VEGF secretion by human retinal pigment epithelial cells (HRPE). HRPE cultures prepared from aged human donor eyes were used for the studies in this report. HRPE secreted both VEGF-A and VEGF-C in small quantities constitutively. Stimulation with a mixture of inflammatory cytokines (IFN-γ, TNF-α, IL-1β), significantly increased the secretion of both VEGF-A and VEGF-C. RSV, in a dose dependent (10-50 uM) manner, suppressed VEGF-A and VEGF-C secretion induced by inflammatory cytokines significantly. RT-PCR analysis indicated that effects of RSV on VEGF secretion were possibly due to decreased mRNA levels. TGF-β and cobalt chloride (hypoxia mimic) also upregulated HRPE cell production of VEGF-A, and this was inhibited by RSV. In contrast, RSV had no effect on anti-angiogenic molecules, endostatin and pigment epithelial derived factor secretion. Studies using an in vitro scratch assay revealed that wound closure was also inhibited by RSV. These results demonstrate that RSV can suppress VEGF secretion induced by inflammatory cytokines, TGF-β and hypoxia. Under pathological conditions, over expression of VEGF is known to worsen AMD. Therefore, RSV may be useful as nutraceutical in controlling pathological choroidal neovascularization processes in AMD.

Ras homolog enriched in the brain is linked to retinal ganglion cell apoptosis after light injury in rats

Ras homolog enriched in the brain (Rheb) is a small GTPase of the Ras family. It has been confirmed that Rheb activation not only regulates cell growth and migration but also induces neuron apoptosis after toxic stimuli. However, the function of Rheb in the retina is still not fully understood. To find out whether Rheb was involved in retinal neuron death, the expression profile of Rheb in light-damaged retinal ganglion cells (RGCs) of adult rats was investigated. Western blotting showed the expression of Rheb was significantly upregulated in the injured retina. Rheb was mainly detected in apoptotic RGCs by using double immunofluorescent staining. Active caspase-3 was upregulated and co-labeled with Rheb. Meanwhile, terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) showed that Rheb-positive RGCs underwent apoptosis after light exposure, which suggested that Rheb might be relevant to RGC apoptosis following phototoxicity. Furthermore, Western blotting and immunofluorescence showed that the expression profiles of CyclinD1 and cyclin-dependent kinase 4 (CDK4) were parallel with that of Rheb in a time-space dependent manner. Based on this study, it is speculated that Rheb might play an important role in physiological and pathological process in light-induced retina damage, which might provide a potential therapeutic avenue of retinal degeneration.

Emergence of dual VEGF and PDGF antagonists in the treatment of exudative age-related macular degeneration

Neovascular ('wet') age-related macular degeneration (AMD) is the leading cause of blindness among Caucasians over the age of 55 in the USA and is an important cause of ocular morbidity worldwide. Progress in oncology, and more recently ophthalmology, led to the development of VEGF antagonists, three of which are now approved for the treatment of wet AMD. Recent discoveries in ophthalmology and vascular biology, however, suggest that combined inhibition of VEGF and platelet-derived growth factor (PDGF) may be more beneficial than inhibition of VEGF alone. Accordingly, numerous studies are underway to evaluate the role of anti-VEGF/PDGF combination therapies for the treatment of wet AMD. This review discusses the biology of VEGF and PDGF and current preclinical and clinical data exploring the use of combined VEGF/PDGF inhibitors in the treatment of neovascular age-related macular degeneration.

Nature and nurture- genes and environment- predict onset and progression of macular degeneration

Age-related macular degeneration (AMD) is a common cause of irreversible visual loss and the disease burden is rising world-wide as the population ages. Both environmental and genetic factors contribute to the development of this disease. Among environmental factors, smoking, obesity and dietary factors including antioxidants and dietary fat intake influence onset and progression of AMD. There are also several lines of evidence that link cardiovascular, immune and inflammatory biomarkers to AMD. The genetic etiology of AMD has been and continues to be an intense and fruitful area of investigation. Genome-wide association studies have revealed numerous common variants associated with AMD and sequencing is increasing our knowledge of how rare genetic variants strongly impact disease. Evidence for interactions between environmental, therapeutic and genetic factors is emerging and elucidating the mechanisms of this interplay remains a major challenge in the field. Genotype-phenotype associations are evolving. The knowledge of non-genetic, modifiable risk factors along with information about heritability and genetic risk variants for this disease acquired over the past 25 years have greatly improved patient management and our ability to predict which patients will develop or progress to advanced forms of AMD. Personalized medicine and individualized prevention and treatment strategies may become a reality in the near future.

Comparisons of amplitude of pseudoaccommodation with aspheric yellow, spheric yellow, and spheric clear monofocal intraocular lenses

Purpose

To determine the amplitude of pseudoaccommodation and higher-order aberrations with three types of implanted monofocal intraocular lenses (IOLs): aspheric yellow (IQ); spheric yellow (NT); and spheric clear (AT).

Setting

Department of Ophthalmology, Nara Medical University, Nara, Japan.

Methods

We studied 60 patients who underwent small incision phacoemulsification with the implantation of a monofocal IQ, NT, or AT IOL. The pseudoaccommodation was measured by the lens-loading method, and the postoperative ocular higher-order aberrations were measured with a Hartmann–Shack wavefront analyzer through natural and 4 mm pupils.

Results

Sixty eyes of 60 patients were studied. The average amplitude of the pseudoaccommodation was 0.45±0.24 D with the IQ IOL, which was significantly lower than that with the AT IOL at 0.81±0.37 D (Tukey’s test; P<0.01). The differences in the amplitude of the pseudoaccommodation between the IQ and the NT IOLs, and between the NT and the AT IOLs were not significant (Tukey’s test; P>0.05). The degree of spherical aberration was significantly different for the IQ, NT, and AT lenses (analysis of variance, P=0.016). The spherical aberration through the IQ IOL was significantly lower than that through the NT and the AT IOLs (Tukey’s test; P<0.01). The fourth-order RMS (root mean square) aberration of the IQ lens was also significantly lower than that of the NT and AT IOLs (Tukey’s test; P<0.01).

Conclusion

Our results suggest that the spherical aberration and selective spectral transmission of IOLs may work together to increase the amplitude of the pseudoaccommodation.

Immunology of age-related macular degeneration

Age-related macular degeneration (AMD) is a leading cause of blindness in aged individuals. Recent advances have highlighted the essential role of immune processes in the development, progression and treatment of AMD. In this Review we discuss recent discoveries related to the immunological aspects of AMD pathogenesis. We outline the diverse immune cell types, inflammatory activators and pathways that are involved. Finally, we discuss the future of inflammation-directed therapeutics to treat AMD in the growing aged population.

HtrA1 is induced by oxidative stress and enhances cell senescence through p38 MAPK pathway

Genetic predisposition and senescence of retinal pigment epithelium induced by oxidative stress are major contributors to age-related macular degeneration (AMD). Single-nucleotide polymorphisms in HTRA1 are strongly linked to the onset of AMD. In this study, we examine the role of HtrA1 in premature senescence and cell death induced by oxidative stress. HtrA1 mRNA and protein were up-regulated during premature senescence induced by H2O2 in both mouse embryonic fibroblasts (MEFs) and ARPE-19 cells. Expression of the senescence markers p21(CIP1/WAF1) and p16(INK4a), and SA-β-galactosidase activity, were higher in HtrA1+/- MEFs than in HtrA1-/- MEFs. HtrA1+/+ and HtrA1+/- MEFs were more resistant than HtrA1-/- MEFs to H2O2-induced cell death. Activation of p38 MAPK by oxidative stress was quicker in HtrA1+/- MEFs than in HtrA1-/- MEFs. The effects of excess HtrA1 were examined by transient transfection of cells with HtrA1 expression vectors or by addition of recombinant proteins. Excess wild type HtrA1 accelerated premature senescence of MEFs and ARPE-19 cells, while the protease-inactive HtrA1 S328A did not. HtrA1-induced senescence was abrogated by inhibition of p38 MAPK. We conclude that HtrA1 is induced by oxidative stress and promotes premature cell senescence through p38 MAPK in a protease activity-dependent manner.

Pharmacological inhibition of lipofuscin accumulation in the retina as a therapeutic strategy for dry AMD treatment

Age-related macular degeneration (AMD) is the leading cause of blindness in the western world. There is no FDA-approved treatment for the most prevalent dry (atrophic) form of AMD. Photoreceptor degeneration in dry AMD is triggered by abnormalities in the retinal pigment epithelium (RPE). It has been suggested that excessive accumulation of fluorescent lipofuscin pigment in the RPE represents an important pathogenic factor in etiology and progression of dry AMD. Cytotoxic lipofuscin bisretinoids, such as A2E, are formed in the retina in a non-enzymatic way from visual cycle retinoids. Inhibition of toxic bisretinoid production in the retina seems to be a sound treatment strategy for dry AMD. In this review we discuss the following classes of pharmacological treatments inhibiting lipofuscin bisretinoid formation in the retina: direct inhibitors of key visual cycle enzymes, RBP4 antagonists, primary amine-containing aldehyde traps, and deuterated analogs of vitamin A.

Biological effects of cigarette smoke in cultured human retinal pigment epithelial cells

The goal of the present study was to determine whether treatment with cigarette smoke extract (CSE) induces cell loss, cellular senescence, and extracellular matrix (ECM) synthesis in primary human retinal pigment epithelial (RPE) cells. Primary cultured human RPE cells were exposed to 2, 4, 8, and 12% of CSE concentration for 24 hours. Cell loss was detected by cell viability assay. Lipid peroxidation was assessed by loss of cis-parinaric acid (PNA) fluorescence. Senescence-associated ß-galactosidase (SA-ß-Gal) activity was detected by histochemical staining. Expression of apolipoprotein J (Apo J), connective tissue growth factor (CTGF), fibronectin, and laminin were examined by real-time PCR, western blot, or ELISA experiments. The results showed that exposure of cells to 12% of CSE concentration induced cell death, while treatment of cells with 2, 4, and 8% CSE increased lipid peroxidation. Exposure to 8% of CSE markedly increased the number of SA-ß-Gal positive cells to up to 82%, and the mRNA expression of Apo J, CTGF, and fibronectin by approximately 3–4 fold. Treatment with 8% of CSE also increased the protein expression of Apo J and CTGF and the secretion of fibronectin and laminin. Thus, treatment with CSE can induce cell loss, senescent changes, and ECM synthesis in primary human RPE cells. It may be speculated that cigarette smoke could be involved in cellular events in RPE cells as seen in age-related macular degeneration.

Effects of hydroquinone on retinal and vascular cells in vitro

Aim:

To explore the molecular pathophysiology that might explain the epidemiologic association between cigarette smoke and age-related macular degeneration (AMD) by examining the effects of hydroquinone (HQ), a toxic compound present in high concentration in cigarette smoke-related tar, on human retinal pigment epithelial cells (ARPE-19), rat retinal neurosensory cells (R-28), and human microvascular endothelial cells (HMVEC).

Materials and Methods:

ARPE-19, R-28, and HMVEC were treated for 24 h with four different concentrations of HQ (500 μM, 200 μM, 100 μM, 50 μM). Cell viability, caspase-3/7 activation, DNA laddering patterns, and lactate dehydrogenase (LDH) levels were analyzed.

Results:

At 50 μM HQ, R-28 cells showed a significant decrease in cell viability compared with the dimethyl sulfoxide (DMSO)-treated controls. At the 100–500 μM concentrations, all three cell lines showed significant cell death (P < 0.001). In the ARPE-19, R-28, and HMVEC cultures, the caspase-3/7 activities were not increased at any of the HQ concentration.

Conclusion:

Our findings suggest that the mechanism of cell death in all three cell lines was through non-apoptotic pathway. In addition, neuroretinal R-28 cells were more sensitive to HQ than the ARPE-19 and HMVEC cultures.

Canadian expert consensus: optimal treatment of neovascular age-related macular degeneration

BACKGROUND

New therapeutic approaches, particularly anti-vascular endothelial growth factor (anti-VEGF) therapies, prevent, and in some cases reverse, vision damage caused by age-related macular degeneration (AMD). Unequal access to care across Canada remains a problem for many retina specialists and their patients.

OBJECTIVE

To develop a consensus concerning the management of patients with exudative age-related macular degeneration (AMD).

DESIGN

Consensus document.

PARTICIPANTS

Ten Canadian retina specialists.

METHODS

The development of a consensus among Canadian experts concerning optimal treatment of AMD began with a review of the clinical evidence, daily practices, existing guidelines, and current national and international approvals and policies. The experts met on June 29, 2010, in Quebec City to discuss their findings and to propose strategies for consensus.

RESULTS

The result of this expert panel is a consensus proposal for Canadian ophthalmologists and retina specialists who are treating patients with or at risk for developing neovascular AMD.

CONCLUSIONS

The consensus provides guidelines to aid retina specialists in managing exudative AMD. Currently, ranibizumab is the only agent with sufficient Level I evidence and a Health Canada-approved indication for the treatment of wet AMD. Bevacizumab has been shown to be noninferior in preserving and improving visual acuity when compared to ranibizumab. Potential safety differences between the 2 drugs remain to be elucidated. The positioning of ranibizumab in this therapeutic area will be further defined as additional data for existing and emerging therapies become available. Until then, this agent remains the therapy of choice for individuals with neovascular AMD.