Sequential structural and functional change in geographic atrophy on multimodal imaging in non-exudative age-related macular degeneration.

PURPOSE: To investigate the temporal order of photoreceptor atrophy, retinal pigment epithelium (RPE) atrophy and visual acuity loss in patients with center-involving geographic atrophy (GA) in non-exudative age-related macular degeneration (neAMD). METHODS: Forty eyes of 25 consecutive patients who eventually developed center-involving GA were investigated. Fundus autofluorescence (FAF) and infrared image coupled optical coherence tomography (OCT) were acquired at each visit. Development of RPE atrophy and photoreceptor atrophy was defined as abnormal hyper/hypo-fluorescence on FAF and photoreceptor loss on OCT over 50% of the vertical or horizontal diameters of the center 1 mm circle, respectively. Visual acuity loss was defined as worsening of more than 0.2 logMAR compared to baseline. Kaplan-Meier analyses was performed to compare the sequential order of these three events. RESULTS: Mean age was 72.72 ± 8.63 years, and follow-up duration was 27.36 ± 17.22 months, with an average number of visits of 3.04 ± 1.54 during follow-up. GA progressed from photoreceptor atrophy on OCT, RPE atrophy on FAF, and then to vision loss (p < 0.001). The median survival time of photoreceptors preceded that of visual acuity by 16.3 months, and the median survival time of RPE preceded that of visual acuity by 7.0 months. At baseline, majority of eyes showed drusen only (57.5%), while the most common feature was incomplete RPE and outer retinal atrophy at 3-year follow-up (40.4%). CONCLUSION: In the progression of center-involving GA, photoreceptor atrophy on OCT and RPE atrophy on FAF precedes visual decline, and can act as biomarkers predicting future visual decline within the following years.

Mitochondrial quality control in non-exudative age-related macular degeneration: From molecular mechanisms to structural and functional recovery.

Non-exudative age-related macular degeneration (NE-AMD) is the leading blindness cause in the elderly. Clinical and experimental evidence supports that early alterations in macular retinal pigment epithelium (RPE) mitochondria play a key role in NE-AMD-induced damage. Mitochondrial dynamics (biogenesis, fusion, fission, and mitophagy), which is under the central control of AMP-activated kinase (AMPK), in turn, determines mitochondrial quality. We have developed a NE-AMD model in C57BL/6J mice induced by unilateral superior cervical ganglionectomy (SCGx), which progressively reproduces the disease hallmarks circumscribed to the temporal region of the RPE/outer retina that exhibits several characteristics of the human macula. In this work we have studied RPE mitochondrial structure, dynamics, function, and AMPK role on these parameters' regulation at the nasal and temporal RPE from control eyes and at an early stage of experimental NE-AMD (i.e., 4 weeks post-SCGx). Although RPE mitochondrial mass was preserved, their function, which was higher at the temporal than at the nasal RPE in control eyes, was significantly decreased at 4 weeks post-SCGx at the same region. Mitochondria were bigger, more elongated, and with denser cristae at the temporal RPE from control eyes. Exclusively at the temporal RPE, SCGx severely affected mitochondrial morphology and dynamics, together with the levels of phosphorylated AMPK (p-AMPK). AMPK activation with metformin restored RPE p-AMPK levels, and mitochondrial dynamics, structure, and function at 4 weeks post-SCGx, as well as visual function and RPE/outer retina structure at 10 weeks post-SCGx. These results demonstrate a key role of the temporal RPE mitochondrial homeostasis as an early target for NE-AMD-induced damage, and that pharmacological AMPK activation could preserve mitochondrial morphology, dynamics, and function, and, consequently, avoid the functional and structural damage induced by NE-AMD.

Choroidal structural features of acquired vitelliform lesions in non-exudative age-related macular degeneration.

PURPOSE: To define the choroidal morphological characteristics of non-exudative age-related macular degeneration (AMD) cases associated with acquired vitelliform lesions (AVLs). METHODS: This retrospective study included intermediate AMD patients with AVLs (Group1, 21eyes) and without AVLs (Group2, 21eyes). A healthy control group was (Group3, 23eyes) also included. Subfoveal choroidal thickness (SFCT), greatest basal diameter (GBD), and maximum height (MH) of the largest PED were measured on spectral domain optical coherence tomography. Internal reflectivity of PEDs and total choroidal area (TCA) were measured using ImageJ software. The TCA was binarized to the luminal area (LA) and stromal area. The choroidal vascularity index (CVI) was assessed. RESULTS: The mean SFCT, TCA, and LA were higher in Group 1 (290.3 ± 86.8 µm, 0.840 ± 0.302 mm2, 0.602 ± 0.227 mm2) than in Group 2 (215.6 ± 85.0 µm, 0.594 ± 0.183 mm2, 0.429 ± 0.139 mm2) (p = 0.014, p = 0.017, p = 0.020, respectively). There was no significant difference in the CVI measurements between Group 1 and Group 2 (p = 1.000). The mean GBD and MH of the PED was higher in Group 1 (1443 ± 595 µm, 188 ± 86 µm) than in Group 2 (851 ± 368 µm, 119 ± 38 µm) (p = <0.001, p = 0.001, respectively). Internal PED reflectivity was significantly lower in Group 1 (0.44 ± 0.21) than in Group 2 (0.66 ± 0.17) (p = <0.001). Internal PED reflectivity showed negative correlation with GBD and MH of the PED in Group 1 (r = -0.587, p = 0.005; rho = -0.448, p = 0.042, respectively). In Group 2, internal PED reflectivity had a negative correlation with MH of the PED (rho = -0.511, p = 0.018). CONCLUSION: Non-exudative AMD patients with AVLs are more prone to have a thick choroid and large hyporeflective PEDs as compared to the those without AVLs.

Risuteganib-a novel integrin inhibitor for the treatment of non-exudative (dry) age-related macular degeneration and diabetic macular edema.

INTRODUCTION: Non-exudative (dry) age-related macular degeneration (AMD) and diabetic macular edema (DME) are leading causes of vision loss worldwide. Besides age-related eye disease study (AREDS) vitamin supplements, there are no efficacious pharmaceutical interventions for dry AMD available. While numerous pharmacologics are available to treat diabetic macular edema (DME), many patients respond suboptimally to existing therapies. Risuteganib is a novel anti-integrin peptide that targets the multiple integrin heterodimers involved in the pathophysiology of dry AMD and DME. Inhibiting these selected integrin heterodimers may benefit patients with these conditions. AREAS COVERED: This article offers a brief overview of current pharmaceuticals available for dry AMD and DME. The proposed role of integrins in AMD and DME is reviewed and later, risuteganib, a novel anti-integrin peptide is introduced. The data from initial Phase 1 and Phase 2 risuteganib clinical trials are discussed in the latter part of the paper. EXPERT OPINION: While there are currently limited treatment options for dry AMD, more data are needed before we can truly evaluate the benefits of adopting risuteganib into the clinic. Conversely, several effective treatment options exist for DME; hence, risuteganib must show that it can add to these results, especially in those with refractory disease, before retina specialists adopt risuteganib into their treatment regimens.

Oxidative stress damage circumscribed to the central temporal retinal pigment epithelium in early experimental non-exudative age-related macular degeneration.

Non-exudative age-related macular degeneration (NE-AMD) represents the leading cause of blindness in the elderly. The macular retinal pigment epithelium (RPE) lies in a high oxidative environment because its high metabolic demand, mitochondria concentration, reactive oxygen species levels, and macular blood flow. It has been suggested that oxidative stress-induced damage to the RPE plays a key role in NE-AMD pathogenesis. The fact that the disease limits to the macular region raises the question as to why this area is particularly susceptible. We have developed a NE-AMD model induced by superior cervical ganglionectomy (SCGx) in C57BL/6J mice, which reproduces the disease hallmarks exclusively circumscribed to the temporal region of the RPE/outer retina. The aim of this work was analyzing RPE regional differences that could explain AMD localized susceptibility. Lower melanin content, thicker basal infoldings, higher mitochondrial mass, and higher levels of antioxidant enzymes, were found in the temporal RPE compared with the nasal region. Moreover, SCGx induced a decrease in the antioxidant system, and in mitochondria mass, as well as an increase in mitochondria superoxide, lipid peroxidation products, nuclear Nrf2 and heme oxygenase-1 levels, and in the occurrence of damaged mitochondria exclusively at the temporal RPE. These findings suggest that despite the well-known differences between the human and mouse retina, it might not be NE-AMD pathophysiology which conditions the localization of the disease, but the macular RPE histologic and metabolic specific attributes that make it more susceptible to choroid alterations leading initially to a localized RPE dysfunction/damage, and secondarily to macular degeneration.

Transient acceleration of autophagic degradation by pharmacological Nrf2 activation is important for retinal pigment epithelium cell survival.

Non-exudative age-related macular degeneration (AMD) is mainly caused by the accumulation of lipofuscin and drusen on the retinal pigment epithelium (RPE). Both oxidative stress and autophagic dysfunction accelerate the deposition of lipofuscin at the RPE. One of the key regulators in the response against oxidative stress is the NF-E2-Related Factor 2 (Nrf2)-kelch like ECH associated protein 1 (Keap1) axis, which is also closely associated with the autophagy pathway. Nrf2 activation upregulates the expression levels of certain anti-oxidative enzymes [e.g. Heme oxygenase-1 (HO-1)], which attenuates oxidative damage. However, until now, the relationship between cytoprotective effects of Nrf2 activation and autophagic degradation remain unclear. To address these questions, we investigated the effects of a novel Nrf2 activator, RS9, on RPE damage. We found that RS9 protected ARPE-19 cells against NaIO3-induced oxidative damage, and that the protective effects of RS9 were inhibited by co-treatment with zinc protoporphyrin, an HO-1 inhibitor. Next, we examined the involvement of autophagic degradation in the protective effects of RS9. Co-treatment with RS9 and chloroquine, a lysosomal acidification inhibitor, inhibited the protective effect. Furthermore, western blotting and immunostaining showed that RS9 accelerated autophagy flux and induced transient upregulation of p62 [also known as sequestosome 1 (SQSTM1)]. Co-treatment with chloroquine and RS9 also inhibited the degradation of autophagosomes. Transient upregulation of SQSTM1 by RS9 was unaltered by HO-1 knockdown using siRNA. RS9 and chloroquine had the same actions in light damaged adult zebrafish retina as those in vitro. In conclusion, we clarified the relationship between acceleration of the autophagy pathway and the cytoprotective effects of Nrf2 activation in RPE cells and zebrafish retina. These findings indicated that Nrf2 activation could be a promising therapeutic approach for non-exudative AMD by supporting RPE maintenance.