Wai T. Wong

Lutein + zeaxanthin and omega-3 fatty acids for age-related macular degeneration: The Age-Related Eye Disease Study 2 (AREDS2) randomized clinical trial

IMPORTANCE Oral supplementation with the Age-Related Eye Disease Study (AREDS) formulation (antioxidant vitamins C and E, beta carotene, and zinc) has been shown to reduce the risk of progression to advanced age-related macular degeneration (AMD). Observational data suggest that increased dietary intake of lutein + zeaxanthin (carotenoids), omega-3 long-chain polyunsaturated fatty acids (docosahexaenoic acid [DHA] + eicosapentaenoic acid [EPA]), or both might further reduce this risk. OBJECTIVES To determine whether adding lutein + zeaxanthin, DHA + EPA, or both to the AREDS formulation decreases the risk of developing advanced AMD and to evaluate the effect of eliminating beta carotene, lowering zinc doses, or both in the AREDS formulation. DESIGN, SETTING, AND PARTICIPANTS The Age-Related Eye Disease Study 2 (AREDS2), a multicenter, randomized, double-masked, placebo-controlled phase 3 study with a 2 × 2 factorial design, conducted in 2006-2012 and enrolling 4203 participants aged 50 to 85 years at risk for progression to advanced AMD with bilateral large drusen or large drusen in 1 eye and advanced AMD in the fellow eye. INTERVENTIONS Participants were randomized to receive lutein (10 mg) + zeaxanthin (2 mg), DHA (350 mg) + EPA (650 mg), lutein + zeaxanthin and DHA + EPA, or placebo. All participants were also asked to take the original AREDS formulation or accept a secondary randomization to 4 variations of the AREDS formulation, including elimination of beta carotene, lowering of zinc dose, or both. MAIN OUTCOMES AND MEASURES Development of advanced AMD. The unit of analyses used was by eye. RESULTS Median follow-up was 5 years, with 1940 study eyes (1608 participants) progressing to advanced AMD. Kaplan-Meier probabilities of progression to advanced AMD by 5 years were 31% (493 eyes [406 participants]) for placebo, 29% (468 eyes [399 participants]) for lutein + zeaxanthin, 31% (507 eyes [416 participants]) for DHA + EPA, and 30% (472 eyes [387 participants]) for lutein + zeaxanthin and DHA + EPA. Comparison with placebo in the primary analyses demonstrated no statistically significant reduction in progression to advanced AMD (hazard ratio [HR], 0.90 [98.7% CI, 0.76-1.07]; P = .12 for lutein + zeaxanthin; 0.97 [98.7% CI, 0.82-1.16]; P = .70 for DHA + EPA; 0.89 [98.7% CI, 0.75-1.06]; P = .10 for lutein + zeaxanthin and DHA + EPA). There was no apparent effect of beta carotene elimination or lower-dose zinc on progression to advanced AMD. More lung cancers were noted in the beta carotene vs no beta carotene group (23 [2.0%] vs 11 [0.9%], nominal P = .04), mostly in former smokers. CONCLUSIONS AND RELEVANCE Addition of lutein + zeaxanthin, DHA + EPA, or both to the AREDS formulation in primary analyses did not further reduce risk of progression to advanced AMD. However, because of potential increased incidence of lung cancer in former smokers, lutein + zeaxanthin could be an appropriate carotenoid substitute in the AREDS formulation. TRIAL REGISTRATION clinicaltrials.gov Identifier: NCT00345176.

Evaluation of time domain and spectral domain optical coherence tomography in the measurement of diabetic macular edema

PURPOSE To evaluate macular thickness and volume measurements and their intrasession repeatability in two optical coherence tomography (OCT) systems: the Stratus OCT, a time domain system, and the Cirrus HD-OCT, a spectral domain system (both by Carl Zeiss Meditec, Inc., Dublin, CA), in the context of diabetic macular edema (DME). METHODS Thirty-three eyes of 33 diabetic patients with clinically significant macular edema (CSME) were scanned in a single session by a single operator on both OCT systems. Macular thickness measurements of nine standard macular subfields and total macular volume were obtained and analyzed. Bland-Altman plots were constructed to assess agreement in macular measurements. Intraclass correlation coefficients (ICCs), coefficients of repeatability (CR(W)), and coefficients of variation (CV(W)) were used to assess intrasession repeatability. RESULTS Macular thickness in nine retinal subfields and macular volume were significantly higher in the Cirrus HD-OCT system compared with the Stratus OCT system. Subfield thickness and total volume measurements, respectively, were 30 to 55 microm and 3.2 mm(3) greater for the Cirrus HD-OCT system compared with the Stratus OCT system. Both Stratus OCT and Cirrus HD-OCT systems demonstrated high intrasession repeatability, with overlapping ranges for CR(W), CV(W), and ICC. Repeatability measures (CR(W) and CV(W)) differed significantly between systems in only one of nine subfields (outer temporal subfield). CONCLUSIONS Absolute measures of macular thickness and volume in patients with DME differed significantly in magnitude between the Stratus OCT and Cirrus HD-OCT systems. However, both OCT systems demonstrated high intrasessional repeatability. Although the two systems may not be used interchangeably, they appear equally reliable in generating macular measurements for clinical practice and research.

Age-related alterations in the dynamic behavior of microglia

Microglia, the primary resident immune cells of the central nervous system (CNS), exhibit dynamic behavior involving rapid process motility and cellular migration that is thought to underlie key functions of immune surveillance and tissue repair. Although age‐related changes in microglial activation have been implicated in the pathogenesis of neurodegenerative diseases of aging, how dynamic behavior in microglia is influenced by aging is not fully understood. In this study, we employed live imaging of retinal microglia in situ to compare microglial morphology and behavioral dynamics in young and aged animals. We found that aged microglia in the resting state have significantly smaller and less branched dendritic arbors, and also slower process motilities, which probably compromise their ability to survey and interact with their environment continuously. We also found that dynamic microglial responses to injury were age‐dependent. While young microglia responded to extracellular ATP, an injury‐associated signal, by increasing their motility and becoming more ramified, aged microglia exhibited a contrary response, becoming less dynamic and ramified. In response to laser‐induced focal tissue injury, aged microglia demonstrated slower acute responses with lower rates of process motility and cellular migration compared with young microglia. Interestingly, the longer term response of disaggregation from the injury site was retarded in aged microglia, indicating that senescent microglial responses, while slower to initiate, are more sustained. Together, these altered features of microglial behavior at rest and following injury reveal an age‐dependent dysregulation of immune response in the CNS that may illuminate microglial contributions to age‐related neuroinflammatory degeneration.

Microglial Morphology and Dynamic Behavior Is Regulated by Ionotropic Glutamatergic and GABAergic Neurotransmission

Purpose Microglia represent the primary resident immune cells in the CNS, and have been implicated in the pathology of neurodegenerative diseases. Under basal or “resting” conditions, microglia possess ramified morphologies and exhibit dynamic surveying movements in their processes. Despite the prominence of this phenomenon, the function and regulation of microglial morphology and dynamic behavior are incompletely understood. We investigate here whether and how neurotransmission regulates “resting” microglial morphology and behavior. Methods We employed an ex vivo mouse retinal explant system in which endogenous neurotransmission and dynamic microglial behavior are present. We utilized live-cell time-lapse confocal imaging to study the morphology and behavior of GFP-labeled retinal microglia in response to neurotransmitter agonists and antagonists. Patch clamp electrophysiology and immunohistochemical localization of glutamate receptors were also used to investigate direct-versus-indirect effects of neurotransmission by microglia. Results Retinal microglial morphology and dynamic behavior were not cell-autonomously regulated but are instead modulated by endogenous neurotransmission. Morphological parameters and process motility were differentially regulated by different modes of neurotransmission and were increased by ionotropic glutamatergic neurotransmission and decreased by ionotropic GABAergic neurotransmission. These neurotransmitter influences on retinal microglia were however unlikely to be directly mediated; local applications of neurotransmitters were unable to elicit electrical responses on microglia patch-clamp recordings and ionotropic glutamatergic receptors were not located on microglial cell bodies or processes by immunofluorescent labeling. Instead, these influences were mediated indirectly via extracellular ATP, released in response to glutamatergic neurotransmission through probenecid-sensitive pannexin hemichannels. Conclusions Our results demonstrate that neurotransmission plays an endogenous role in regulating the morphology and behavior of “resting” microglia in the retina. These findings illustrate a mode of constitutive signaling between the neural and immune compartments of the CNS through which immune cells may be regulated in concert with levels of neural activity.

Secondary Analyses of the Effects of Lutein/Zeaxanthin on Age-Related Macular Degeneration Progression: AREDS2 Report No. 3

IMPORTANCE The Age-Related Eye Disease Study (AREDS) formulation for the treatment of age-related macular degeneration (AMD) contains vitamin C, vitamin E, beta carotene, and zinc with copper. The Age-Related Eye Disease Study 2 (AREDS2) assessed the value of substituting lutein/zeaxanthin in the AREDS formulation because of the demonstrated risk for lung cancer from beta carotene in smokers and former smokers and because lutein and zeaxanthin are important components in the retina. OBJECTIVE To further examine the effect of lutein/zeaxanthin supplementation on progression to late AMD. DESIGN, SETTING, PARTICIPANTS The Age-Related Eye Disease Study 2 is a multicenter, double-masked randomized trial of 4203 participants, aged 50 to 85 years, at risk for developing late AMD; 66% of patients had bilateral large drusen and 34% had large drusen and late AMD in 1 eye. INTERVENTIONS In addition to taking the original or a variation of the AREDS supplement, participants were randomly assigned in a factorial design to 1 of the following 4 groups: placebo; lutein/zeaxanthin, 10 mg/2 mg; omega-3 long-chain polyunsaturated fatty 3 acids, 1.0 g; or the combination. MAIN OUTCOMES AND MEASURE S Documented development of late AMD by central, masked grading of annual retinal photographs or by treatment history. RESULTS In exploratory analysis of lutein/zeaxanthin vs no lutein/zeaxanthin, the hazard ratio of the development of late AMD was 0.90 (95% CI, 0.82-0.99; P = .04). Exploratory analyses of direct comparison of lutein/zeaxanthin vs beta carotene showed hazard ratios of 0.82 (95% CI, 0.69-0.96; P = .02) for development of late AMD, 0.78 (95% CI, 0.64-0.94; P = .01) for development of neovascular AMD, and 0.94 (95% CI, 0.70-1.26; P = .67) for development of central geographic atrophy. In analyses restricted to eyes with bilateral large drusen at baseline, the direct comparison of lutein/zeaxanthin vs beta carotene showed hazard ratios of 0.76 (95% CI, 0.61-0.96; P = .02) for progression to late AMD, 0.65 (95% CI, 0.49-0.85; P = .002) for neovascular AMD, and 0.98 (95% CI, 0.69-1.39; P = .91) for central geographic atrophy. CONCLUSION AND RELEVANCE The totality of evidence on beneficial and adverse effects from AREDS2 and other studies suggests that lutein/zeaxanthin could be more appropriate than beta carotene in the AREDS-type supplements. TRIAL REGISTRATION clinicaltrials.gov Identifier: NCT00345176.

Ophthalmic Drug Delivery Systems for the Treatment of Retinal Diseases: Basic Research to Clinical Applications

The basic science part of this article focuses on the anatomic barriers to the five major modes of ocular drug delivery: intraocular, periocular, hybrid, topical, and systemic. The second half is a review of the clinical and regulatory components of translational science.

Retinal microglia: just bystander or target for therapy?

Resident microglial cells can be regarded as the immunological watchdogs of the brain and the retina. They are active sensors of their neuronal microenvironment and rapidly respond to various insults with a morphological and functional transformation into reactive phagocytes. There is strong evidence from animal models and in situ analyses of human tissue that microglial reactivity is a common hallmark of various retinal degenerative and inflammatory diseases. These include rare hereditary retinopathies such as retinitis pigmentosa and X-linked juvenile retinoschisis but also comprise more common multifactorial retinal diseases such as age-related macular degeneration, diabetic retinopathy, glaucoma, and uveitis as well as neurological disorders with ocular manifestation. In this review, we describe how microglial function is kept in balance under normal conditions by cross-talk with other retinal cells and summarize how microglia respond to different forms of retinal injury. In addition, we present the concept that microglia play a key role in local regulation of complement in the retina and specify aspects of microglial aging relevant for chronic inflammatory processes in the retina. We conclude that this resident immune cell of the retina cannot be simply regarded as bystander of disease but may instead be a potential therapeutic target to be modulated in the treatment of degenerative and inflammatory diseases of the retina.

Microglia in the Mouse Retina Alter the Structure and Function of Retinal Pigmented Epithelial Cells: A Potential Cellular Interaction Relevant to AMD

Background Age-related macular degeneration (AMD) is a leading cause of legal blindness in the elderly in the industrialized word. While the immune system in the retina is likely to be important in AMD pathogenesis, the cell biology underlying the disease is incompletely understood. Clinical and basic science studies have implicated alterations in the retinal pigment epithelium (RPE) layer as a locus of early change. Also, retinal microglia, the resident immune cells of the retina, have been observed to translocate from their normal position in the inner retina to accumulate in the subretinal space close to the RPE layer in AMD eyes and in animal models of AMD. Methodology/Principal Findings In this study, we examined the effects of retinal microglia on RPE cells using 1) an in vitro model where activated retinal microglia are co-cultured with primary RPE cells, and 2) an in vivo mouse model where retinal microglia are transplanted into the subretinal space. We found that retinal microglia induced in RPE cells 1) changes in RPE structure and distribution, 2) increased expression and secretion of pro-inflammatory, chemotactic, and pro-angiogenic molecules, and 3) increased extent of in vivo choroidal neovascularization in the subretinal space. Conclusions/Significance These findings share similarities with important pathological features found in AMD and suggest the relevance of microglia-RPE interactions in AMD pathogenesis. We speculate that the migration of retinal microglia into the subretinal space in early stages of the disease induces significant changes in RPE cells that perpetuate further microglial accumulation, increase inflammation in the outer retina, and fosters an environment conducive for the formation of neovascular changes responsible for much of vision loss in advanced AMD.

Rapid dendritic movements during synapse formation and rearrangement

Major technical advances in the imaging of live cells have led to a recent flurry of studies demonstrating how dendrites remodel dynamically during development. Taken together with our current understanding of axonal development, these studies help provide a more unified picture of how neural circuits might be formed altered or maintained throughout life.

Microglial aging in the healthy CNS: phenotypes, drivers, and rejuvenation

Neurodegenerative diseases such as Alzheimers disease, Parkinsons disease, and age-related macular degeneration (AMD), share two characteristics in common: (1) a disease prevalence that increases markedly with advancing age, and (2) neuroinflammatory changes in which microglia, the primary resident immune cell of the CNS, feature prominently. These characteristics have led to the hypothesis that pathogenic mechanisms underlying age-related neurodegenerative disease involve aging changes in microglia. If correct, targeting features of microglial senescence may constitute a feasible therapeutic strategy. This review explores this hypothesis and its implications by considering the current knowledge on how microglia undergo change during aging and how the emergence of these aging phenotypes relate to significant alterations in microglial function. Evidence and theories on cellular mechanisms implicated in driving senescence in microglia are reviewed, as are “rejuvenative” measures and strategies that aim to reverse or ameliorate the aging microglial phenotype. Understanding and controlling microglial aging may represent an opportunity for elucidating disease mechanisms and for formulating novel therapies.