Retinal degeneration triggered by inactivation of PTEN in the retinal pigment epithelium

Age- and sex- divergent translatomic responses of the mouse retinal pigmented epithelium

Aging is the main risk factor for age-related macular degeneration (AMD), a retinal neurodegenerative disease that leads to irreversible blindness, particularly in people over 60 years old. Retinal pigmented epithelium (RPE) atrophy is an AMD hallmark. Genome-wide chromatin accessibility, DNA methylation, and gene expression studies of AMD and control RPE demonstrate epigenomic/transcriptomic changes occur during AMD onset and progression. However, mechanisms by which molecular alterations of normal aging impair RPE function and contribute to AMD pathogenesis are unclear. Here, we specifically interrogate the RPE translatome with advanced age and across sexes in a novel RPE reporter mouse model. We find differential age- and sex- associated transcript expression with overrepresentation of pathways related to inflammation in the RPE. Concordant with impaired RPE function, the phenotypic changes in the aged translatome suggest that aged RPE becomes immunologically active, in both males and females, with some sex-specific signatures, which supports the need for sex representation for in vivo studies.

Myelin regulatory factor ( Myrf ) is a critical early regulator of retinal pigment epithelial development

Myelin regulatory factor (Myrf) is a critical transcription factor in early retinal and retinal pigment epithelial development, and human variants in MYRF are a cause for nanophthalmos. Single cell RNA sequencing (scRNAseq) was performed on Myrf conditional knockout mice ( Rx>Cre Myrf fl/fl ) at 3 developmental timepoints. Myrf was expressed specifically in the RPE, and expression was abrogated in Rx>Cre Myrf fl/fl eyes. scRNAseq analysis revealed a loss of RPE cells at all timepoints resulting from cell death. GO-term analysis in the RPE revealed downregulation of melanogenesis and anatomic structure morphogenesis pathways, which were supported by electron microscopy and histologic analysis. Novel structural target genes including Ermn and Upk3b , along with macular degeneration and inherited retinal disease genes were identified as downregulated, and a strong upregulation of TGFß/BMP signaling and effectors was observed. Regulon analysis placed Myrf downstream of Pax6 and Mitf and upstream of Sox10 in RPE differentiation. Together, these results suggest a strong role for Myrf in the RPE maturation by regulating melanogenesis, cell survival, and cell structure, in part acting through suppression of TGFß signaling and activation of Sox10 .

SUMMARY STATEMENT

Myrf regulates RPE development, melanogenesis, and is important for cell structure and survival, in part through regulation of Ermn , Upk3b and Sox10, and BMP/TGFb signaling.

Protective effects of triptolide against oxidative stress in retinal pigment epithelium cells via the PI3K/AKT/Nrf2 pathway: a network pharmacological method and experimental validation

PURPOSE

Among aging adults, age-related macular degeneration (AMD), is a prevalent cause of blindness. Nevertheless, its progression may be halted by antioxidation in retinal pigment epithelium (RPE). The primary effective constituent of Tripterygium wilfordii Hook. F., triptolide (TP), has demonstrated anti-inflammatory, antiproliferative, and antioxidant properties. The mechanics of the protective effect of triptolide against the oxidative damage in retinal pigment epithelial (RPE) were assessed in this study.

METHODS

ARPE-19 cells were pretreated with TP, and then exposed to sodium iodate (SI). First, cell viability was assessed using CCK-8. Subsequently, we measured indicators for cell oxidation including reactive oxygen species (ROS), catalase (CAT), superoxide dismutase (SOD), and malondialdehyde (MDA). Then, we used network pharmacological analysis and molecular docking to explore the signaling pathway of TP. Last, we used western blot, ELISA, and immunofluorescence assays to clarify the potential mechanistic pathways.

RESULTS

The network pharmacology data suggested that TP may inhibit AMD by regulating the PI3K/Akt signaling pathway. Experimental results showed that the potential mechanism is that it regulates the PI3K/Akt pathway and promotes Nrf2 phosphorylation and activation, thereby raising the level of antioxidant factors (HO-1, NQO1) and reducing the generation of ROS, which inhibit oxidative damage.

CONCLUSION

Our findings suggested that the effect of TP on SI-exposed RPE cells principally relies on the regulation of oxidative stress through the PI3K/Akt/Nrf2 signaling pathway.

Deletion of IFT20 exclusively in the RPE ablates primary cilia and leads to retinal degeneration

Vision impairment places a serious burden on the aging society, affecting the lives of millions of people. Many retinal diseases are of genetic origin, of which over 50% are due to mutations in cilia-associated genes. Most research on retinal degeneration has focused on the ciliated photoreceptor cells of the retina. However, the contribution of primary cilia in other ocular cell types has largely been ignored. The retinal pigment epithelium (RPE) is a monolayer epithelium at the back of the eye intricately associated with photoreceptors and essential for visual function. It is already known that primary cilia in the RPE are critical for its development and maturation; however, it remains unclear whether this affects RPE function and retinal tissue homeostasis. We generated a conditional knockout mouse model, in which IFT20 is exclusively deleted in the RPE, ablating primary cilia. This leads to defective RPE function, followed by photoreceptor degeneration and, ultimately, vision impairment. Transcriptomic analysis offers insights into mechanisms underlying pathogenic changes, which include transcripts related to epithelial homeostasis, the visual cycle, and phagocytosis. Due to the loss of cilia exclusively in the RPE, this mouse model enables us to tease out the functional role of RPE cilia and their contribution to retinal degeneration, providing a powerful tool for basic and translational research in syndromic and non-syndromic retinal degeneration. Non-ciliary mechanisms of IFT20 in the RPE may also contribute to pathogenesis and cannot be excluded, especially considering the increasing evidence of non-ciliary functions of ciliary proteins.

A New Preclinical Model of Retinitis Pigmentosa Due to Pde6g Deficiency

Purpose

Retinitis pigmentosa (RP) is the most common cause of inherited blindness, with onset occurring as early as 4 years of age in certain rare but severe forms caused by mutations in the gamma subunit of phosphodiesterase 6 (PDE6). Studies in humans and mice have shown that RP pathology begins with progressive photoreceptor death, which then drives changes in downstream neurons, neighboring retinal pigment epithelium (RPE), and vasculature. Here, we present the first detailed analysis of RP disease progression in Pde6g-deficient mice.

Design

Experimental study of an RP mouse model.

Subjects

We studied Pde6g-/- and Pde6g+/- mice at the age of 7, 16, 30, 44, and 56 days with n = 2 to 5 per group and time point.

Methods

Photoreceptor degeneration and retinal remodeling were analyzed in retinal sections by immunofluorescence. Retinal blood vessel degradation was analyzed in flat-mounted retinas immunolabeled for isolectin GS-IB4. Protein expression was measured by immunoblot. Acellular capillaries were assessed in trypsin-digested and hematoxylin-eosin-stained retinas at postnatal day (P) 44. Retinal pigment epithelium cells were delineated in flat-mounted RPE-choroid-sclera by immunolabeling for the cell-adhesion protein β-catenin.

Main Outcome Measures

Immunofluorescence and morphometry (quantitative analysis of outer nuclear layer, dendrite area, vessel area, acellular vessels, RPE cell size, number of nuclei per RPE cell, RPE cell eccentricity, and RPE cell solidity).

Results

This novel RP model exhibits early onset and rapid rod degeneration, with the vast majority gone by P16. This pathology leads to retinal remodeling, including changes of inner retinal neurons, early activation of glia cells, degradation of retinal vasculature, and structural abnormalities of the RPE.

Conclusions

The pathology in our Pde6g-/- mouse model precisely mirrors human RP progression. The results demonstrate the significant role of the gamma subunit in maintaining phosphodiesterase activity and provide new insights into the disease progression due to Pde6g deficiency.

Financial Disclosures

Proprietary or commercial disclosure may be found after the references.

Circadian regulation in aging: Implications for spaceflight and life on earth

Alterations in the circadian system are characteristic of aging on Earth. With the decline in physiological processes due to aging, several health concerns including vision loss, cardiovascular disorders, cognitive impairments, and muscle mass loss arise in elderly populations. Similar health risks are reported as "red flag" risks among astronauts during and after a long-term Space exploration journey. However, little is known about the common molecular alterations underlying terrestrial aging and space-related aging in astronauts, and controversial conclusions have been recently reported. In light of the regulatory role of the circadian clock in the maintenance of human health, we review here the overlapping role of the circadian clock both on aging on Earth and spaceflight with a focus on the four most affected systems: visual, cardiovascular, central nervous, and musculoskeletal systems. In this review, we briefly introduce the regulatory role of the circadian clock in specific cellular processes followed by alterations in those processes due to aging. We next summarize the known molecular alterations associated with spaceflight, highlighting involved clock-regulated genes in space flown Drosophila, nematodes, small mammals, and astronauts. Finally, we discuss common genes that are altered in terms of their expression due to aging on Earth and spaceflight. Altogether, the data elaborated in this review strengthen our hypothesis regarding the timely need to include circadian dysregulation as an emerging hallmark of aging on Earth and beyond.

Wnt/β-Catenin Signaling Pathway Is Necessary for the Specification but Not the Maintenance of the Mouse Retinal Pigment Epithelium

β-Catenin (Ctnnb1) has been shown to play critical roles in the development and maintenance of epithelial cells, including the retinal pigment epithelium (RPE). Ctnnb1 is not only a component of intercellular junctions in the epithelium, it also functions as a transcriptional regulator in the Wnt signaling pathway. To identify which of its functional modalities is critically involved in mouse RPE development and maintenance, we varied Ctnnb1 gene content and activity in mouse RPE lineage cells and tested their impacts on mouse eye development. We found that a Ctnnb1 double mutant (Ctnnb1dm), which exhibits impaired transcriptional activity, could not replace Ctnnb1 in the RPE, whereas Ctnnb1Y654E, which has reduced affinity for the junctions, could do so. Expression of the constitutively active Ctnnb1∆ex3 mutant also suppressed the development of RPE, instead facilitating a ciliary cell fate. However, the post-mitotic or mature RPE was insensitive to the loss, inactivation, or constitutive activation of Ctnnb1. Collectively, our results suggest that Ctnnb1 should be maintained within an optimal range to specify RPE through transcriptional regulation of Wnt target genes in the optic neuroepithelium.

SIRT6 overexpression in the nucleus protects mouse retinal pigment epithelium from oxidative stress

Retinal pigment epithelium (RPE) is essential for the survival of retinal photoreceptors. To study retinal degeneration, sodium iodate (NaIO3) has been used to cause oxidative stress-induced RPE death followed by photoreceptor degeneration. However, analyses of RPE damage itself are still limited. Here, we characterized NaIO3-induced RPE damage, which was divided into three regions: periphery with normal-shaped RPE, transitional zone with elongated cells, and center with severely damaged or lost RPE. Elongated cells in the transitional zone exhibited molecular characteristics of epithelial-mesenchymal transition. Central RPE was more susceptible to stresses than peripheral RPE. Under stresses, SIRT6, an NAD+-dependent protein deacylase, rapidly translocated from the nucleus to the cytoplasm and colocalized with stress granule factor G3BP1, leading to nuclear SIRT6 depletion. To overcome this SIRT6 depletion, SIRT6 overexpression was induced in the nucleus in transgenic mice, which protected RPE from NaIO3 and partially preserved catalase expression. These results demonstrate topological differences of mouse RPE and warrant further exploring SIRT6 as a potential target for protecting RPE from oxidative stress-induced damage.

IKKβ Inhibition Attenuates Epithelial Mesenchymal Transition of Human Stem Cell-Derived Retinal Pigment Epithelium

Epithelial-mesenchymal transition (EMT), which is well known for its role in embryonic development, malignant transformation, and tumor progression, has also been implicated in a variety of retinal diseases, including proliferative vitreoretinopathy (PVR), age-related macular degeneration (AMD), and diabetic retinopathy. EMT of the retinal pigment epithelium (RPE), although important in the pathogenesis of these retinal conditions, is not well understood at the molecular level. We and others have shown that a variety of molecules, including the co-treatment of human stem cell-derived RPE monolayer cultures with transforming growth factor beta (TGF-β) and the inflammatory cytokine tumor necrosis factor alpha (TNF-α), can induce RPE-EMT; however, small molecule inhibitors of RPE-EMT have been less well studied. Here, we demonstrate that BAY651942, a small molecule inhibitor of nuclear factor kapa-B kinase subunit beta (IKKβ) that selectively targets NF-κB signaling, can modulate TGF-β/TNF-α-induced RPE-EMT. Next, we performed RNA-seq studies on BAY651942 treated hRPE monolayers to dissect altered biological pathways and signaling events. Further, we validated the effect of IKKβ inhibition on RPE-EMT-associated factors using a second IKKβ inhibitor, BMS345541, with RPE monolayers derived from an independent stem cell line. Our data highlights the fact that pharmacological inhibition of RPE-EMT restores RPE identity and may provide a promising approach for treating retinal diseases that involve RPE dedifferentiation and EMT.

Pten associates with important gene regulatory network to fine-tune Müller glia-mediated zebrafish retina regeneration

Unlike mammals, zebrafish possess a remarkable ability to regenerate damaged retina after an acute injury. Retina regeneration in zebrafish involves the induction of Müller glia-derived progenitor cells (MGPCs) exhibiting stem cell-like characteristics, which are capable of restoring all retinal cell-types. The induction of MGPC through Müller glia-reprograming involves several cellular, genetic and biochemical events soon after a retinal injury. Despite the knowledge on the importance of Phosphatase and tensin homolog (Pten), which is a dual-specificity phosphatase and tumor suppressor in the maintaining of cellular homeostasis, its importance during retina regeneration remains unknown. Here, we explored the importance of Pten during zebrafish retina regeneration. The Pten gets downregulated upon retinal injury and is absent from the MGPCs, which is essential to trigger Akt-mediated cellular proliferation essential for retina regeneration. We found that the downregulation of Pten in the post-injury retina accelerates MGPCs formation, while its overexpression restricts the regenerative response. We observed that Pten regulates the proliferation of MGPCs not only through Akt pathway but also by Mmp9/Notch signaling. Mmp9-activity is essential to induce the proliferation of MGPCs in the absence of Pten. Lastly, we show that expression of Pten is fine-tuned through Mycb/histone deacetylase1 and Tgf-β signaling. The present study emphasizes on the stringent regulation of Pten and its crucial involvement during the zebrafish retina regeneration.

Self-delivering RNAi compounds as therapeutic agents in the central nervous system to enhance axonal regeneration after injury

The therapeutic use of RNAi has grown but often faces several hurdles related to delivery systems, compound stability, immune activation, and on-target/off-tissue effects. Self-delivering RNAi (sdRNA) molecules do not require delivery agents or excipients. Here we demonstrate the ability of sdRNA to reduce the expression of PTEN (phosphatase and tensin homolog) to stimulate regenerative axon regrowth in the injured adult CNS. PTEN-targeting sdRNA compounds were tested for efficacy in vivo by intravitreal injection after adult rat optic nerve injury. We describe critical steps in lead compound generation through the optimization of nucleotide modifications, enhancements for stability in biological matrices, and screening for off-target immunostimulatory activity. The data show that PTEN expression in vivo can be reduced using sdRNA and this enhances regeneration in adult CNS neurons after injury, raising the possibility that this method could be utilized for other clinically relevant nervous system indications.

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self-delivering siRNA (sdRNA) can decrease neuronal gene expression in vivo

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sdRNA can be successfully delivered in vivo without using vectors or excipients

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Phosphatase and tensin homolog (PTEN)-targeting sdRNA can enhance CNS neuronal regeneration after injury

Retinal pigment epithelium-specific CLIC4 mutant is a mouse model of dry age-related macular degeneration

Age-related macular degeneration (AMD) is the leading cause of blindness among the elderly. Dry AMD has unclear etiology and no treatment. Lipid-rich drusen are the hallmark of dry AMD. An AMD mouse model and insights into drusenogenesis are keys to better understanding of this disease. Chloride intracellular channel 4 (CLIC4) is a pleomorphic protein regulating diverse biological functions. Here we show that retinal pigment epithelium (RPE)-specific Clic4 knockout mice exhibit a full spectrum of functional and pathological hallmarks of dry AMD. Multidisciplinary longitudinal studies of disease progression in these mice support a mechanistic model that links RPE cell-autonomous aberrant lipid metabolism and transport to drusen formation.

Fine Tuning of an Oxidative Stress Model with Sodium Iodate Revealed Protective Effect of NF-κB Inhibition and Sex-Specific Difference in Susceptibility of the Retinal Pigment Epithelium

Oxidative stress of the retinal pigment epithelium (RPE) is a major risk factor for age-related macular degeneration (AMD). As a dry AMD model via oxidative stress, sodium iodate (NaIO₃), which is primarily toxic to the RPE, has often been used at a high dose to cause RPE death for studying photoreceptor degeneration. Thus, characterization of RPE damage by a low dose of NaIO₃ is still limited. To quantify RPE damage caused by NaIO₃ in mice, we recently developed a morphometric method using RPE flat-mounts. Here, we report that NaIO₃ has a narrow range of dose–effect correlation at 11–18 mg/kg body weight in male C57BL/6J mice. We evaluated the usefulness of our quantification method in two experimental settings. First, we tested the effect of NF-κB inhibition on NaIO₃-induced RPE damage in male C57BL/6J mice. IKKβ inhibitor BAY 651942 suppressed upregulation of NF-κB targets and protected the RPE from oxidative stress. Second, we tested sex-specific differences in NaIO₃-induced RPE damage in C57BL/6J mice using a low dose near the threshold. NaIO₃ caused more severe RPE damage in female mice than in male mice. These results demonstrate the usefulness of the quantification method and the importance of fine-tuning of the NaIO₃ dose. The results also show the therapeutic potential of IKKβ inhibition for oxidative stress-related RPE diseases, and reveal previously-unrecognized sex-specific differences in RPE susceptibility to oxidative stress.

Retinoid Metabolism in the Degeneration of Pten-Deficient Mouse Retinal Pigment Epithelium

In vertebrate eyes, the retinal pigment epithelium (RPE) provides structural and functional homeostasis to the retina. The RPE takes up retinol (ROL) to be dehydrogenated and isomerized to 11-cis-retinaldehyde (11-cis-RAL), which is a functional photopigment in mammalian photoreceptors. As excessive ROL is toxic, the RPE must also establish mechanisms to protect against ROL toxicity. Here, we found that the levels of retinol dehydrogenases (RDHs) are commonly decreased in phosphatase tensin homolog (Pten)-deficient mouse RPE, which degenerates due to elevated ROL and that can be rescued by feeding a ROL-free diet. We also identified that RDH gene expression is regulated by forkhead box O (FOXO) transcription factors, which are inactivated by hyperactive Akt in the Pten-deficient mouse RPE. Together, our findings suggest that a homeostatic pathway comprising PTEN, FOXO, and RDH can protect the RPE from ROL toxicity.

HYPERREFLECTIVE FOCI AS A PATHOGENETIC BIOMARKER IN CHOROIDEREMIA

PURPOSE

To assess hyperreflective foci (HF) number and distribution in choroideremia (CHM) using spectral domain optical coherence tomography.

METHODS

Observational, cross-sectional case series. Consecutive patients and matched controls (20 eyes each) underwent best-corrected visual acuity measurement, fundoscopy, blue-light autofluorescence (BL-FAF) and spectral domain optical coherence tomography. Hyperreflective foci were assessed on a horizontal spectral domain optical coherence tomography scan, in the 500-µm area centered on the umbo, and in the 500-μm-wide areas internal (preserved border) and external (pathologic border) to the chorioretinal atrophy of CHM patients, and in the parafovea of controls. Hyperreflective foci were subclassified as retinal or choroidal. The spared central islet was measured on BL-FAF. Primary outcome was HF quantification in CHM. Secondary outcomes included their relationships with atrophy extent.

RESULTS

Choroideremia eyes disclosed a significantly higher HF number across the pathologic border and in the fovea when compared with controls; in particular, these HF were primarily located in the choroid (59-87%). Moreover, choroidal HF in the pathologic border inversely correlated with the area of the preserved central islet.

CONCLUSION

Hyperreflective foci might turn out to be a potential biomarker of CHM activity or severity. In this regard, we hypothesize that HF may be related to macrophages activation or progressive retinal pigment epithelium degeneration.

Retinal Manifestations of Mitochondrial Oxidative Phosphorylation Disorders

Purpose

The purpose of this paper was to discuss manifestations of primary mitochondrial dysfunctions and whether the retinal pigment epithelium or the photoreceptors are preferentially affected.

Methods

A retrospective analysis was performed of patients with clinically and laboratory confirmed diagnoses of maternally inherited diabetes and deafness (MIDD) or Kearns–Sayre syndrome (KSS). Patients underwent full ophthalmic examination, full-field electroretinogram, and multimodal imaging studies, including short-wavelength autofluorescence, spectral domain-optical coherence tomography, and color fundus photography.

Results

A total of five patients with MIDD and four patients with KSS were evaluated at two tertiary referral centers. Mean age at initial evaluation was 50.3 years old. Nascent outer retinal tubulations corresponding with faint foci of autofluorescence were observed in two patients with MIDD. Characteristic features of this cohort included a foveal sparing phenotype observed in 13 of 18 eyes (72%), global absence of intraretinal pigment migration, and preserved retinal function on full-field electroretinogram testing in 12 of 16 eyes (75%). One patient diagnosed with MIDD presented with an unusual pattern of atrophy surrounding the parapapillary region and one patient with KSS presented with an atypical choroideremia-like phenotype.

Conclusions

MIDD and KSS are phenotypically heterogeneous disorders. Several features of disease suggest that primary mitochondrial dysfunction may first affect the retinal pigment epithelium followed by secondary photoreceptor loss. Similarities between primary mitochondrial degenerations and retinal disorders, such as age-related macular degeneration may suggest a primary role of mitochondria in the pathogenesis of these oligogenic disorders.

HO-1-mediated ferroptosis as a target for protection against retinal pigment epithelium degeneration

Oxidative stress-mediated retinal pigment epithelium (RPE) degeneration plays a vital role in retinal degeneration with irreversible visual impairment, most notably in age-related macular degeneration (AMD), but a key pathogenic factor and the targeted medical control remain controversial and unclear. In this work, by sophisticated high-throughput sequencing and biochemistry investigations, the major pathologic processes during RPE degeneration in the sodium iodate-induced oxidative stress model has been identified to be heme oxygenase-1 (HO-1)-regulated ferroptosis, which is controlled by the Nrf2–SLC7A11–HO-1 hierarchy, through which ferrous ion accumulation and lethal oxidative stress cause RPE death and subsequently photoreceptor degeneration. By direct knockdown of HO-1 or using HO-1 inhibitor ZnPP, the specific inhibition of HO-1 overexpression has been determined to significantly block RPE ferroptosis. In mice, treatment with ZnPP effectively rescued RPE degeneration and achieved superior therapeutic effects: substantial recovery of the retinal structure and visual function. These findings highlight that targeting HO-1-mediated RPE ferroptosis could serve as an effectively retinal-protective strategy for retinal degenerative diseases prevention, including AMD.

Tsg101 Is Necessary for the Establishment and Maintenance of Mouse Retinal Pigment Epithelial Cell Polarity

The retinal pigment epithelium (RPE) forms a monolayer sheet separating the retina and choroid in vertebrate eyes. The polarized nature of RPE is maintained by distributing membrane proteins differentially along apico-basal axis. We found the distributions of these proteins differ in embryonic, post-natal, and mature mouse RPE, suggesting developmental regulation of protein trafficking. Thus, we deleted tumor susceptibility gene 101 (Tsg101), a key component of endosomal sorting complexes required for transport (ESCRT), in embryonic and mature RPE to determine whether ESCRT-mediated endocytic protein trafficking correlated with the establishment and maintenance of RPE polarity. Loss of Tsg101 severely disturbed the polarity of RPE, which forms irregular aggregates exhibiting non-polarized distribution of cell adhesion proteins and activation of epidermal growth factor receptor signaling. These findings suggest that ESCRT-mediated protein trafficking is essential for the development and maintenance of RPE cell polarity.

Signaling roles of phosphoinositides in the retina

The field of phosphoinositide signaling has expanded significantly in recent years. Phosphoinositides (also known as phosphatidylinositol phosphates or PIPs) are universal signaling molecules that directly interact with membrane proteins or with cytosolic proteins containing domains that directly bind phosphoinositides and are recruited to cell membranes. Through the activities of phosphoinositide kinases and phosphoinositide phosphatases, seven distinct phosphoinositide lipid molecules are formed from the parent molecule, phosphatidylinositol. PIP signals regulate a wide range of cellular functions, including cytoskeletal assembly, membrane budding and fusion, ciliogenesis, vesicular transport, and signal transduction. Given the many excellent reviews on phosphoinositide kinases, phosphoinositide phosphatases, and PIPs in general, in this review, we discuss recent studies and advances in PIP lipid signaling in the retina. We specifically focus on PIP lipids from vertebrate (e.g., bovine, rat, mouse, toad, and zebrafish) and invertebrate (e.g., Drosophila, horseshoe crab, and squid) retinas. We also discuss the importance of PIPs revealed from animal models and human diseases, and methods to study PIP levels both in vitro and in vivo. We propose that future studies should investigate the function and mechanism of activation of PIP-modifying enzymes/phosphatases and further unravel PIP regulation and function in the different cell types of the retina.

SLC6A20 transporter: a novel regulator of brain glycine homeostasis and NMDAR function

Glycine transporters (GlyT1 and GlyT2) that regulate levels of brain glycine, an inhibitory neurotransmitter with co‐agonist activity for NMDA receptors (NMDARs), have been considered to be important targets for the treatment of brain disorders with suppressed NMDAR function such as schizophrenia. However, it remains unclear whether other amino acid transporters expressed in the brain can also regulate brain glycine levels and NMDAR function. Here, we report that SLC6A20A, an amino acid transporter known to transport proline based on in vitro data but is understudied in the brain, regulates proline and glycine levels and NMDAR function in the mouse brain. SLC6A20A transcript and protein levels were abnormally increased in mice carrying a mutant PTEN protein lacking the C terminus through enhanced β‐catenin binding to the Slc6a20a gene. These mice displayed reduced extracellular levels of brain proline and glycine and decreased NMDAR currents. Elevating glycine levels back to normal ranges by antisense oligonucleotide‐induced SLC6A20 knockdown, or the competitive GlyT1 antagonist sarcosine, normalized NMDAR currents and repetitive climbing behavior observed in these mice. Conversely, mice lacking SLC6A20A displayed increased extracellular glycine levels and NMDAR currents. Lastly, both mouse and human SLC6A20 proteins mediated proline and glycine transports, and SLC6A20 proteins could be detected in human neurons. These results suggest that SLC6A20 regulates proline and glycine homeostasis in the brain and that SLC6A20 inhibition has therapeutic potential for brain disorders involving NMDAR hypofunction.

CircRNA Is a Rising Star in Researches of Ocular Diseases

A newly rediscovered subclass of noncoding RNAs, circular RNAs (circRNAs), is produced by a back-splicing mechanism with a covalently closed loop structure. They not only serve as the sponge for microRNAs (miRNAs) and proteins but also regulate gene expression and epigenetic modification, translate into peptides, and generate pseudogenes. Dysregulation of circRNA expression has opened a new chapter in the etiology of various human disorders, including cancer and cardiovascular, neurodegenerative, and ocular diseases. Recent studies recognized the vital roles that circRNAs played in the pathogenesis of various eye diseases, highlighting circRNAs as promising biomarkers for diagnosis and assessment of progression and prognosis. Interventions targeting circRNAs provide insights for developing novel treatments for these ocular diseases. This review summarizes our current perception of the properties, biogenesis, and functions of circRNAs and the development of circRNA researches related to ophthalmologic diseases, including diabetic retinopathy, age-related macular degeneration, retinopathy of prematurity, glaucoma, corneal neovascularization, cataract, pterygium, proliferative vitreoretinopathy, retinoblastoma, and ocular melanoma.

Differences in Intraretinal Pigment Migration Across Inherited Retinal Dystrophies

PURPOSE

To determine whether there are differences in the prevalence of intraretinal pigment migration (IPM) across ages and genetic causes of inherited retinal dystrophies (IRDs).

DESIGN

Retrospective cohort study.

METHODS

Patients were evaluated at a single tertiary referral center. All patients with a clinical diagnosis of IRD and confirmatory genetic testing were included in these analyses. A total of 392 patients fit inclusion criteria, and 151 patients were excluded based on inconclusive genetic testing. Patients were placed into 3 groups, ciliary and ciliary-related photoreceptor, nonciliary photoreceptor, and retinal pigment epithelium (RPE), based on the cellular expression of the gene and the primary affected cell type. The presence of IPM was evaluated by using slit lamp biomicroscopy, indirect ophthalmoscopy, and wide-field color fundus photography.

RESULTS

IPM was seen in 257 of 339 patients (75.8%) with mutations in photoreceptor-specific genes and in 18 of 53 patients (34.0%) with mutations in RPE-specific genes (P < .0001). Pairwise analysis following stratification by age and gene category suggested significant differences at all age groups between patients with mutations in photoreceptor-specific genes and patients with mutations in RPE-specific genes (P < .05). A fitted multivariate logistic regression model was produced and demonstrated that the incidence of IPM increases as a function of both age and gene category.

CONCLUSIONS

IPM is a finding more commonly observed in IRDs caused by mutations in photoreceptor-specific genes than RPE-specific genes. The absence of IPM does not always rule out IRD and should raise suspicion for disease mutations in RPE-specific genes.

Role of Epithelial-Mesenchymal Transition in Retinal Pigment Epithelium Dysfunction

Retinal pigment epithelial (RPE) cells maintain the health and functional integrity of both photoreceptors and the choroidal vasculature. Loss of RPE differentiation has long been known to play a critical role in numerous retinal diseases, including inherited rod-cone degenerations, inherited macular degeneration, age-related macular degeneration, and proliferative vitreoretinopathy. Recent studies in post-mortem eyes have found upregulation of critical epithelial-mesenchymal transition (EMT) drivers such as TGF-β, Wnt, and Hippo. As RPE cells become less differentiated, they begin to exhibit the defining characteristics of mesenchymal cells, namely, the capacity to migrate and proliferate. A number of preclinical studies, including animal and cell culture experiments, also have shown that RPE cells undergo EMT. Taken together, these data suggest that RPE cells retain the reprogramming capacity to move along a continuum between polarized epithelial cells and mesenchymal cells. We propose that movement along this continuum toward a mesenchymal phenotype be defined as RPE Dysfunction. Potential mechanisms include impaired tight junctions, accumulation of misfolded proteins and dysregulation of several key pathways and molecules, such as TGF-β pathway, Wnt pathway, nicotinamide, microRNA 204/211 and extracellular vesicles. This review synthesizes the evidence implicating EMT of RPE cells in post-mortem eyes, animal studies, primary RPE, iPSC-RPE and ARPE-19 cell lines.

Phosphoinositide Lipids in Ocular Tissues

Inositol phospholipids play an important role in cell physiology. The inositol head groups are reversibly phosphorylated to produce seven distinct phosphorylated inositides, commonly referred to as phosphoinositides (PIs). These seven PIs are dynamically interconverted from one PI to another by the action of PI kinases and PI phosphatases. The PI signals regulate a wide variety of cellular functions, including organelle distinction, vesicular transport, cytoskeletal organization, nuclear events, regulation of ion channels, cell signaling, and host–pathogen interactions. Most of the studies of PIs in ocular tissues are based on the PI enzymes and PI phosphatases. In this study, we examined the PI levels in the cornea, retinal pigment epithelium (RPE), and retina using PI-binding protein as probes. We have examined the lipids PI(3)P, PI(4)P, PI(3,4)P₂, PI(4,5)P₂, and PI(3,4,5)P₃, and each is present in the cornea, RPE, and retina. Alterations in the levels of these PIs in mouse models of retinal disease and corneal infections have been reported, and the results of our study will help in the management of anomalous phosphoinositide metabolism in ocular tissues.

D609 protects retinal pigmented epithelium as a potential therapy for age-related macular degeneration

Accumulated oxidative damage may lead to irreversible retinal pigmented epithelium (RPE) cell death, which is considered to be the primary cause of dry age-related macular degeneration (AMD), leading to blindness in the elderly. However, an effective therapy for this disease is lacking. Here, we described a robust high-content screening procedure with a library of 814 protective compounds and found that D609 strongly protected RPE cells from sodium iodate (SI)-induced oxidative cell death and prolonged their healthy survival. D609 effectively attenuated excessive reactive oxygen species (ROS) and prevented severe mitochondrial loss due to oxidative stress in the RPE cells. Surprisingly, the potent antioxidative effects of D609 were not achieved through its own reducibility but were primarily dependent on its ability to increase the expression of metallothionein. The injection of this small water-soluble molecule also showed an explicit protective effect of the RPE layer in an SI-induced AMD mouse model. These findings suggested that D609 could serve as a novel antioxidative protector of RPE cells both in vitro and in vivo and unveiled a novel antioxidative mechanism of D609, which may ultimately have clinical applications for the treatment of AMD.

Circular Noncoding RNA NR3C1 Acts as a miR-382-5p Sponge to Protect RPE Functions via Regulating PTEN/AKT/mTOR Signaling Pathway

Age-related macular degeneration (AMD) is a universal leading cause for irreversible blindness in the elderly population. Dedifferentiation of retinal pigment epithelium (RPE) cells initiates early pathological events in atrophic AMD. Herein, we aim to investigate effects of a circular RNA derived from the NR3C1 gene (circNR3C1) on regulating RPE function and AMD pathogenesis. circNR3C1 expression was consistently upregulated along with RPE differentiation and was downregulated in dysfunctional RPE and blood serum of AMD patients. Silencing of circNR3C1 reduced RPE characteristic transcripts and proteins, interrupted phagocytosis, accelerated intracellular reactive oxygen species (ROS) generation, and promoted RPE proliferation in vitro. circN3C1 silencing also decreased expressions of RPE characteristic markers and disturbed the ultrastructure of RPE in vivo, as shown by a thickened RPE with twisted basal infoldings and outer segments. Mechanistically, circNR3C1 acted as an endogenous microRNA-382-5p (miR-382-5p) sponge to sequester its activity, which increased phosphatase and tensin homolog on chromosome 10 (PTEN) expression and inhibited the protein kinase B/mammalian target of rapamycin (AKT/mTOR) pathway. miR-382-5p overexpression and PTEN silencing mimicked effects of circNR3C1 silencing on RPE phenotypes in vivo and in vitro. In conclusion, circNR3C1 prevents AMD progression and protects RPE by directly sponging miR-382-5p to block its interaction with PTEN and subsequently blocks the AKT/mTOR pathway. Pharmacological circNR3C1 supplementations are promising therapeutic options for atrophic AMD.

INTRARETINAL HYPERREFLECTIVE FOCI IN BEST VITELLIFORM MACULAR DYSTROPHY

PURPOSE

To report on the presence of hyperreflective foci (HF) on spectral domain optical coherence tomography in patients with Best vitelliform macular dystrophy (BVMD), and to describe the relationship between HF and stages of the disease.

METHODS

Consecutive patients diagnosed with BVMD were enrolled in a prospective cross-sectional study. All patients and control subjects underwent a complete ophthalmologic examination, including best-corrected visual acuity and spectral domain optical coherence tomography.

MAIN OUTCOME MEASURE

identification of HF in BVMD. Secondary outcome: assessment of the HF in each stage and correlation with best-corrected visual acuity.

RESULTS

Overall, 75 eyes of 39 patients were included in the study (Stage 1: 13%, Stage 2: 43%, Stage 3: 15%, Stage 4: 21%, and Stage 5: 8%). On spectral domain optical coherence tomography assessment, intraretinal HF were present in 83% of all eyes, in 91% of eyes affected by clinical BVMD (Stages 2-5) and in 100% of patients in Stages 4 and 5. In 46% of clinically diseased eyes, HF were localized in the fovea and in correspondence with the BVMD lesions at the level of the outer nuclear layer and outer plexiform layer. Hyperreflective foci were present in 16% of control eyes. Mean number of HF in eyes affected by clinical BVMD stood at 7.67 ± 7.35. These were predominantly small HF (6.23 ± 6.14, P < 0.001) localized in the outer nuclear layer (5.19 ± 5.38, P = 0.001) and presented largely in the extrafoveal, rather than the foveal area (5.21 ± 5.57 vs 2.46 ± 2.73, P = 0.001). Analysis of HF distribution revealed that the control group and Stage 1 eyes had the fewest HF; Stage 4 displayed a significant increase in the number of HF compared with Stages 2 and 3; Stage 5 also showed an increased number of HF, although this difference was statistically significant only with Stage 3 eyes. The best-corrected visual acuity was negatively related to the number of HF, with best-corrected visual acuity deteriorating as the number of HF increased in Stages 2 to 5 (P < 0.001).

CONCLUSION

This study describes the presence of HF in BVMD using spectral domain optical coherence tomography. Our data suggest that HF identification is correlated with the progression of the disease and could represent a useful biomarker of BVMD.

Identification of hyperreflective foci in angioid streaks

AIMS

To assess hyperreflective foci (HF) number in angioid streaks (AS) by means of spectral-domain optical coherence tomography (SD-OCT).

METHODS

Observational and cross-sectional study. Sixty-two eyes with AS and 62 controls underwent best-corrected visual acuity (BCVA), fundoscopy, and SD-OCT. HF were assessed on the horizontal scan of a six-line radial OCT, in the fovea (1500-μm diameter) and parafovea (500 μm external to the fovea), and sub-classified as retinal or choroidal, small or large. Eyes were distributed in one of four groups, as carrying foveal AS without choroidal neovascularization (CNV) (14 eyes), extra-foveal AS without CNV (14), active CNV (20), and inactive CNV (14). Primary outcome was HF assessment in AS. Secondary outcomes included their correlations with BCVA.

RESULTS

AS-affected eyes had higher HF numbers. Our sub-analysis revealed that patients with active CNV had a larger number of retinal and choroidal HF than all the other groups, whereas retinal and choroidal foci were significantly increased in inactive CNV only with respect to controls. Interestingly, patients with foveal AS showed HF number increase in the choroid and fovea. BCVA deterioration positively correlated with the total HF number found in the fovea and the choroid.

CONCLUSION

HF are significantly increased in patients with AS. Despite being especially evident in active CNV, the increasing number in eyes without CNV might suggest new pathogenetic aspects of the disease.

High efficient differentiation of human adipose-derived stem cells into retinal pigment epithelium-like cells in medium containing small molecules inducers with a simple method

BACKGROUND

The induction of retinal pigmented epithelium cells (RPE) is one of the most important objectives in research focused on treating retinal degenerative diseases. The present study aims to differentiate human adipose stem cells (hADSCs) into RPE cells for replacement therapies in cases of retinal degenerative diseases.

METHODS

Lipoaspirate-derived human adipose stem cells (LA-hADSCs) were obtained from abdominal samples and examined by immunocytochemistry for the expression of mesenchymal adipose stem cell markers. RPE cells were also obtained from human samples and cultured to be used as control after being examined for the expression of their designated markers. hADSCs differentiated into RPE cells after 80 days using chemical inducers in one steps. The differentiated cells were then compared to control cells in marker expression. The differentiated cells were also examined under a scanning electron microscope for the presence of apical microvilli and cell connection.

RESULTS

Cultured hADSCs at the fourth passage was shown to express the surface markers CD90 (98 ± 2%), CD11b (96 ± 3%), and CD105 (95 ± 4%). The RPE cells obtained from human samples expressed the marker RPE65 quite well. 80 days after differentiation, the previously hADSCs expressed both RPE65 (100%) and CRALBP (96 ± 1%) and were thus significantly similar to the RPE cells obtained from human samples. Morphologically, differentiated cells appeared to have epithelial and cytoplasmic pigment granules. Observations using a scanning electron microscope recorded clear connections among the differentiated RPE cells and revealed apical microvilli.

CONCLUSION

Human adipose stem cells can differentiate into retinal pigmented epithelium cells, which can be used in cell replacement therapy for degenerative diseases including age-related macular degeneration (AMD) as well as retinitis pigmentosa (RP).

Rates of Bone Spicule Pigment Appearance in Patients With Retinitis Pigmentosa Sine Pigmento

PURPOSE

To determine rate of bone spicule pigmentation appearance in patients with retinitis pigmentosa (RP).

DESIGN

Retrospective, observational case series.

PARTICIPANTS

A total of 240 patients were analyzed for this study.

METHODS

A retrospective analysis was conducted at the Electrodiagnostic Clinic at Columbia University Medical Center of all patients' medical records with a diagnosis of RP between July 2017 and January 2018. The medical records of these patients were analyzed to determine whether the patients presented with pigment migration on their first and last visit to our clinic. Among those who did not have bone spicule at first visit, we examined the time to appearance of newly formed bone spicule. The survival distribution was then estimated using the Kaplan-Meier estimator, where the event is bone spicule and time starts at first visit.

RESULTS

From the 240 patients analyzed, 213 patients presented with intraretinal pigmentation on the first visit to our clinic, and 27 patients presented without intraretinal pigmentation. Of these 27 patients, 10 patients developed pigmentation by their follow-up, with a median time to appearance of bone spicule of 5.4 years from first visit, according to the Kaplan-Meier estimates.

CONCLUSIONS

The timeline of bone spicule pigment appearance in RP has important implications in the natural history characterization of disease progression and application as a biomarker for interventional trials.

A Role for βA3/A1-Crystallin in Type 2 EMT of RPE Cells Occurring in Dry Age-Related Macular Degeneration

Purpose

The RPE cells have a major role in the development of dry age-related macular degeneration (AMD). We present novel evidence that βA3/A1-crystallin, encoded by the Cryba1 gene, a protein known to be important for lysosomal clearance in the RPE, also has a role in epithelial-to-mesenchymal transition (EMT) of RPE cells.

Methods

RPE from dry AMD globes, genetically engineered mice lacking Cryba1 globally or specifically in the RPE, spontaneous mutant rats (Nuc1) with a loss-of-function mutation in Cryba1, and the melanoma OCM3 cell line were used. Spatial localization of proteins was demonstrated with immunofluorescence, gene expression levels were determined by quantitative PCR (qPCR), and protein levels by Western blotting. Cell movement was evaluated using wound healing and cell migration assays. Co-immunoprecipitation was used to identify binding partners of βA3/A1-crystallin.

Results

βA3/A1-crystallin is upregulated in polarized RPE cells compared to undifferentiated cells. Loss of βA3/A1-crystallin in murine and human RPE cells resulted in upregulation of Snail and vimentin, downregulation of E-cadherin, and increased cell migration. βA3/A1-crystallin binds to cortactin, and loss of βA3/A1-crystallin resulted in increased P-cortactin^Y421. The RPE from AMD samples had increased Snail and vimentin, and decreased E-cadherin, compared to age-matched controls.

Conclusions

We introduced a novel concept of dry AMD initiation induced by lysosomal clearance defects in the RPE and subsequent attempts by RPE cells to avoid the resulting stress by undergoing EMT. We demonstrate that βA3/A1-crystallin is a potential therapeutic target for AMD through rejuvenation of lysosomal dysfunction and potentially, reversal of EMT.

Sodium Iodate Disrupted the Mitochondrial-Lysosomal Axis in Cultured Retinal Pigment Epithelial Cells

PURPOSE

Low doses of sodium iodate (NaIO₃) impair visual function in experimental animals with selective damage to retinal pigment epithelium (RPE) and serve as a useful model to study diseases caused by RPE degeneration. Mitochondrial dysfunction and defective autophagy have been suggested to play important roles in normal aging as well as many neurodegenerative diseases. In this study, we examined whether NaIO₃ treatment disrupted the mitochondrial-lysosomal axis in cultured RPE.

METHODS

The human RPE cell line, ARPE-19, was treated with low concentrations (≤500 μM) of NaIO₃. The expression of proteins involved in the autophagic pathway and mitochondrial biogenesis was examined with Western blot. Intracellular acidic compartments and lipofuscinogenesis were evaluated by acridine orange staining and autofluorescence, respectively. Mitochondrial mass, mitochondrial membrane potential (MMP), and mitochondrial function were quantified by MitoTracker Green staining, tetramethylrhodamine methyl ester staining, and the MTT assay, respectively. Phagocytosis and the degradation of photoreceptor outer segments (POS) were assessed by fluorescence-based approaches and Western blot against rhodopsin.

RESULTS

Treatment with low concentrations of NaIO₃ decreased cellular acidity, blocked autophagic flux, and resulted in increased lipofuscinogenesis in ARPE-19 cells. Despite increases in protein levels of Sirtuin 1 and PGC-1α, mitochondrial function was compromised, and this decrease was attributed to disrupted MMP. POS phagocytic activities decreased by 60% in NaIO₃-treated cells, and the degradation of ingested POS was also impaired. Pretreatment and cotreatment with rapamycin partially rescued NaIO₃-induced RPE dysfunction.

CONCLUSIONS

Low concentrations of NaIO₃ disrupted the mitochondrial-lysosomal axis in RPE and led to impaired phagocytic activities and degradation capacities.

Cadherins in the retinal pigment epithelium (RPE) revisited: P-cadherin is the highly dominant cadherin expressed in human and mouse RPE in vivo

The retinal pigment epithelium (RPE) supports the health and function of retinal photoreceptors and is essential for normal vision. RPE cells are post-mitotic, terminally differentiated, and polarized epithelial cells. In pathological conditions, however, they lose their epithelial integrity, become dysfunctional, even dedifferentiate, and ultimately die. The integrity of epithelial cells is maintained, in part, by adherens junctions, which are composed of cadherin homodimers and p120-, β-, and α-catenins linking to actin filaments. While E-cadherin is the major cadherin for forming the epithelial phenotype in most epithelial cell types, it has been reported that cadherin expression in RPE cells is different from other epithelial cells based on results with cultured RPE cells. In this study, we revisited the expression of cadherins in the RPE to clarify their relative contribution by measuring the absolute quantity of cDNAs produced from mRNAs of three classical cadherins (E-, N-, and P-cadherins) in the RPE in vivo. We found that P-cadherin (CDH3) is highly dominant in both mouse and human RPE in situ. The degree of dominance of P-cadherin is surprisingly large, with mouse Cdh3 and human CDH3 accounting for 82-85% and 92-93% of the total of the three cadherin mRNAs, respectively. We confirmed the expression of P-cadherin protein at the cell-cell border of mouse RPE in situ by immunofluorescence. Furthermore, we found that oxidative stress induces dissociation of P-cadherin and β-catenin from the cell membrane and subsequent translocation of β-catenin into the nucleus, resulting in activation of the canonical Wnt/β-catenin pathway. This is the first report of absolute comparison of the expression of three cadherins in the RPE, and the results suggest that the physiological role of P-cadherin in the RPE needs to be reevaluated.

Regulation of the tumor suppressor PTEN by natural anticancer compounds

The tumor suppressor phosphatase and tensin homologue (PTEN) has phosphatase activity, with phosphatidylinositol (3,4,5)-trisphosphate (PIP3), a product of phosphatidylinositol 3-kinase (PI3K), as one of the principal substrates. PTEN is a negative regulator of the Akt pathway, which plays a fundamental role in controlling cell growth, survival, and proliferation. Loss of PTEN function has been observed in many different types of cancer. Functional inactivation of PTEN as a consequence of germ-line mutations or promoter hypermethylation predisposes individuals to malignancies. PTEN undergoes posttranslational modifications, such as oxidation, acetylation, phosphorylation, SUMOylation, and ubiquitination, which influence its catalytic activity, interactions with other proteins, and subcellular localization. Cellular redox status is crucial for posttranslational modification of PTEN and its functional consequences. Oxidative stress and inflammation are major causes of loss of PTEN function. Pharmacologic or nutritional restoration of PTEN function is considered a reliable strategy in the management of PTEN-defective cancer. In this review, we highlight natural compounds, such as curcumin, indol-3 carbinol, and omega-3 fatty acids, that have the potential to restore or potentiate PTEN expression/activity, thereby suppressing cancer cell proliferation, survival, and resistance to chemotherapeutic agents.

Prostate cancer, PI3K, PTEN and prognosis

Loss of function of the PTEN tumour suppressor, resulting in dysregulated activation of the phosphoinositide 3-kinase (PI3K) signalling network, is recognized as one of the most common driving events in prostate cancer development. The observed mechanisms of PTEN loss are diverse, but both homozygous and heterozygous genomic deletions including PTEN are frequent, and often accompanied by loss of detectable protein as assessed by immunohistochemistry (IHC). The occurrence of PTEN loss is highest in aggressive metastatic disease and this has driven the development of PTEN as a prognostic biomarker, either alone or in combination with other factors, to distinguish indolent tumours from those likely to progress. Here, we discuss these factors and the consequences of PTEN loss, in the context of its role as a lipid phosphatase, as well as current efforts to use available inhibitors of specific components of the PI3K/PTEN/TOR signalling network in prostate cancer treatment.

PTEN Reduced UVB-Mediated Apoptosis in Retinal Pigment Epithelium Cells

Age-related macular degeneration (AMD) is a leading cause of blindness and progressive loss of central vision in the elderly population. The important factor of AMD pathogenesis is the degeneration of retinal pigment epithelial (RPE) cells by oxidative stress. Inactivation of PTEN can disrupt intercellular adhesion in the RPE cells, but the mechanism of oxidative stress is less known. Here we presented evidence that UVB-mediated oxidative stress induced apoptosis in ARPE-19 cells. Downregulation of the expression of PTEN in UVB-irradiative RPE cells triggered DNA damage and increased the level of UVB-induced apoptosis by activating p53-dependent pathway. However, overexpression of PTEN increased cell survival by suppressing p-H2A in response to DNA damage and apoptosis. When using Pifithrin-α (one of p53 inhibitors), the level of p53-dependent apoptosis was significantly lower than untreated, which suggested that p53 was possibly involved in PTEN-dependent apoptosis. Thus, it elucidated the molecular mechanisms of UVB-induced damage in RPE cells and may offer an alternative therapeutic target in dry AMD.

Region-specific role for Pten in maintenance of epithelial phenotype and integrity

Previous studies have demonstrated resistance to naphthalene-induced injury in proximal airways of mice with lung epithelial-specific deletion of the tumor-suppressor gene Pten, attributed to increased proliferation of airway progenitors. We tested effects of Pten loss following bleomycin injury, a model typically used to study distal lung epithelial injury, in conditional Pten^SFTPC-cre knockout mice. Pten-deficient airway epithelium exhibited marked hyperplasia, particularly in small bronchioles and at bronchoalveolar duct junctions, with reduced E-cadherin and β-catenin expression between cells toward the luminal aspect of the hyperplastic epithelium. Bronchiolar epithelial and alveolar epithelial type II (AT2) cells in Pten^SFTPC-cre mice showed decreased expression of epithelial markers and increased expression of mesenchymal markers, suggesting at least partial epithelial-mesenchymal transition at baseline. Surprisingly, and in contrast to previous studies, mutant mice were exquisitely sensitive to bleomycin, manifesting rapid weight loss, respiratory distress, increased early mortality (by day 5), and reduced dynamic lung compliance. This was accompanied by sloughing of the hyperplastic airway epithelium with occlusion of small bronchioles by cellular debris, without evidence of increased parenchymal lung injury. Increased airway epithelial cell apoptosis due to loss of antioxidant defenses, reflected by decreased expression of superoxide dismutase 3, in combination with deficient intercellular adhesion, likely predisposed to airway sloughing in knockout mice. These findings demonstrate an important role for Pten in maintenance of airway epithelial phenotype integrity and indicate that responses to Pten deletion in respiratory epithelium following acute lung injury are highly context-dependent and region-specific.

Intraretinal Hyperreflective Foci in Acquired Vitelliform Lesions of the Macula: Clinical and Histologic Study

PURPOSE

To describe the natural course, visual outcomes, and anatomic changes and provide histologic correlates in eyes with intraretinal hyperreflective foci associated with acquired vitelliform lesions.

DESIGN

Retrospective cohort study and imaging-histology correlation in a single donor eye.

METHODS

participants: Patients with intraretinal hyperreflective foci and acquired vitelliform lesions from 2 tertiary referral centers were evaluated from January 2002 to January 2014.

MAIN OUTCOME MEASURES

The chronology of clinical and imaging features of retinal anatomic changes and the pattern of intraretinal hyperreflective foci migration were documented using spectral-domain optical coherence tomography (OCT). One donor eye with intraretinal hyperreflective foci was identified in a pathology archive by ex vivo OCT and was studied with high-resolution light and electron microscopic examination.

RESULTS

Intraretinal hyperreflective foci were associated with acquired vitelliform lesions in 25 of 254 eyes (9.8%) with a strong female preponderance (86% of patients). Focal disruptions to the ellipsoid zone and external limiting membrane overlying the acquired vitelliform lesions were observed prior to the occurrence of intraretinal hyperreflective foci in 75% of cases. Histologic evaluation showed that intraretinal hyperreflective foci represent cells of retinal pigment epithelium origin that are similar to those found in the vitelliform lesions themselves and contain lipofuscin granules, melanolipofuscin granules, and melanosomes. The occurrence of intraretinal hyperreflective foci was not a significant determinant of final visual acuity (P = .34), but development of outer retinal atrophy was (P = .003).

CONCLUSIONS

Intraretinal hyperreflective foci associated with acquired vitelliform lesions are of retinal pigment epithelium origin, and the natural course and functional changes are described.

MicroRNA-29 regulates high-glucose-induced apoptosis in human retinal pigment epithelial cells through PTEN

Hyperglycemia or high-glucose (HG)-induced apoptosis in human retinal pigment epithelial (RPE) cells is a characteristic process in diabetic retinopathy. In our study, we examined whether microRNA-29 (miR-29) may regulate HG-induced RPE cell apoptosis. Human RPE cell line, ARPE-19 cells, was treated with various high concentration of glucose in vitro. HG-induced RPE cell apoptosis was examined by terminal deoxynucleotide transferase-mediated dUTP nick end labeling (TUNEL) assay and miR-29 gene expression by quantitative RT-PCR (qRT-PCR). miR-29 was then downregulated in RPE cells, and its effect on HG-induced apoptosis was examined by TUNEL assay and western blot assay on caspase-7 protein. Association of miR-29 on its downstream target, PTEN, in HG-induced RPE cell apoptosis was evaluated by dual-luciferase assay and qRT-PCR. PTEN was silenced in RPE cells. The effects of PTEN downregulation on miR-29-mediated HG-induced RPE cell apoptosis were also examined by TUNEL and western blot assays. HG induced significant apoptosis in RPE cells in a dose-dependent manner. miR-29 was upregulated by HG in RPE cells. miR-29 downregulation protected HG-induced apoptosis and reduced the production of caspase-7 protein in RPE cells. PTEN was shown to be directly downregulated by HG and then upregulated by miR-29 downregulation in RPE cells. Small interfering RNA (siRNA)-mediated PTEN downregulation reversed the protective effect of miR-29 downregulation on HG-induced RPE cell apoptosis. This study demonstrates that miR-29, through inverse association of PTEN, plays an important role in the process of HG-induced apoptosis in RPE cells.

A Method for the Isolation and Culture of Adult Rat Retinal Pigment Epithelial (RPE) Cells to Study Retinal Diseases

Diseases such as age-related macular degeneration (AMD) affect the retinal pigment epithelium (RPE) and lead to the death of the epithelial cells and ultimately blindness. RPE transplantation is currently a major focus of eye research and clinical trials using human stem cell-derived RPE cells are ongoing. However, it remains to be established to which extent the source of RPE cells for transplantation affects their therapeutic efficacy and this needs to be explored in animal models. Autotransplantation of RPE cells has attractions as a therapy, but existing protocols to isolate adult RPE cells from rodents are technically difficult, time-consuming, have a low yield and are not optimized for long-term cell culturing. Here, we report a newly devised protocol which facilitates reliable and simple isolation and culture of RPE cells from adult rats. Incubation of a whole rat eyeball in 20 U/ml papain solution for 50 min yielded 4 × 10(4) viable RPE cells. These cells were hexagonal and pigmented upon culture. Using immunostaining, we demonstrated that the cells expressed RPE cell-specific marker proteins including cytokeratin 18 and RPE65, similar to RPE cells in vivo. Additionally, the cells were able to produce and secrete Bruch's membrane matrix components similar to in vivo situation. Similarly, the cultured RPE cells adhered to isolated Bruch's membrane as has previously been reported. Therefore, the protocol described in this article provides an efficient method for the rapid and easy isolation of high quantities of adult rat RPE cells. This provides a reliable platform for studying the therapeutic targets, testing the effects of drugs in a preclinical setup and to perform in vitro and in vivo transplantation experiments to study retinal diseases.

Effect of Storage Temperature on Key Functions of Cultured Retinal Pigment Epithelial Cells

Purpose. Replacement of the diseased retinal pigment epithelium (RPE) with cells capable of performing the specialized functions of the RPE is the aim of cell replacement therapy for treatment of macular degenerative diseases. A storage method for RPE is likely to become a prerequisite for the establishment of such treatment. Herein, we analyze the effect of storage temperature on key functions of cultured RPE cells. Methods. Cultured ARPE-19 cells were stored in Minimum Essential Medium at 4°C, 16°C, and 37°C for seven days. Total RNA was isolated and the gene expression profile was determined using DNA microarrays. Comparison of the microarray expression values with qRT-PCR analysis of selected genes validated the results. Results. Expression levels of several key genes involved in phagocytosis, pigment synthesis, the visual cycle, adherens, and tight junctions, and glucose and ion transport were maintained close to control levels in cultures stored at 4°C and 16°C. Cultures stored at 37°C displayed regulational changes in a larger subset of genes related to phagocytosis, adherens, and tight junctions. Conclusion. RPE cultures stored at 4°C and 16°C for one week are capable of maintaining the expression levels of genes important for key RPE functions close to control levels.

Subducted and melanotic cells in advanced age-related macular degeneration are derived from retinal pigment epithelium

PURPOSE

To describe, illustrate, and account for two cell types plausibly derived from RPE in geographic atrophy (GA) and choroidal neovascularization (CNV) of AMD, using melanosomes, lipofuscin, and basal laminar deposit (BLamD) as anatomical markers.

METHODS

Human donor eyes with GA (n = 13) or CNV (n = 39) were histologically processed, photodocumented, and analyzed for frequencies of occurrence. We defined RPE as cells containing spindle-shaped melanosomes and RPE lipofuscin, internal to basal lamina or BLamD, if present, or Bruch's membrane if not, and RPE-derived cells as those plausibly derived from RPE and not attached to basal lamina or BLamD.

RESULTS

'Subducted' cells contain RPE melanosomes and localize to the sub-RPE space, on Bruch's membrane. Credible transitional forms from RPE cells were seen. Grades of RPE overlying 'Subducted' cells were 'Atrophic with BLamD' (32.2% vs. 37.0% of 'Subducted,' for GA and CNV eyes, respectively), 'Dissociated' (22.0% vs. 21.7%), 'Nonuniform' (22.0% vs. 23.9%), and 'Sloughed' RPE (10.2% vs. 4.3%). Found exclusively in CNV scars, 'Melanotic' cells containing spherical melanosomes were adjacent to 'Entombed' RPE with spindle-shaped and spherical melanosomes. Of subretinal 'Melanotic' cells, 40.0% associated with 'Atrophy with BLamD,' 36.8% with 'Atrophy without BLamD,' and 20.6% with 'Entombed.'

CONCLUSIONS

'Dissociated' RPE within atrophic areas may be the source of 'Subducted' cells. 'Entombed' RPE within fibrovascular and fibrocellular scars may be the source of 'Melanotic' cells. An imaging correlate for 'Subducted' cells awaits discovery; 'Melanotic' cells appear gray-black in the CNV fundus. Results provide a basis for future molecular phenotyping studies.

Connection between Tumor Suppressor BRCA1 and PTEN in Damaged DNA Repair

Genomic instability finally induces cell death or apoptosis. The tumor suppressor, phosphatase and tensin homolog on chromosome 10 (PTEN), is a dual-specificity phosphatase, which has protein phosphatase activity and lipid phosphatase activity that antagonizes PI3K activity. Cells that lack PTEN have constitutively higher levels of PIP3 and activated downstream PI3K/AKT targets. BRCA1, a well-known breast cancer tumor suppressor, is to associate with breast cancer risk and genetic susceptibility. Many studies have demonstrated that PTEN, as well as BRCA1, plays a critical role in DNA damage responses. The BRCA1 functionally cooperates with PTEN and might be an essential blockage in the development of several tumors. Actually, the PTEN and BRCA1 genes are recognized as one of the most frequently deleted and/or mutated in many human cancers. The PI3K/AKT pathway is constitutively active in BRCA1-defective human cancer cells. Loss or decrease of these PTEN or BRCA1 function, by either mutation or reduced expression, has a role in various tumor developments. This review summarizes recent findings of the function of BRCA1 and PTEN involved in genomic stability and cancer cell signaling.

Link between PI3K/AKT/PTEN Pathway and NOX Proteinin Diseases

Accumulating evidence has revealed that thePI3K/AKT/PTENpathway acts as a pivotal determinant of cell fate regarding senescence and apoptosis, which is mediated by intracellular reactive oxygen species (ROS) generation. NADPH oxidase (NOX) family of enzymes generates the ROS. The regulation of NOX enzymes is complex, with many members of this family exhibiting complexity in terms of subunit composition, cellular location, and tissue-specific expression. Cells are continuously exposed to the ROS, which represent mutagens and are thought to be a major contributor to several diseases including cancer and aging process. Therefore, cellular ROS sensing and metabolism are firmly regulated by a variety of proteins involved in the redox mechanism. In this review, the roles of oxidative stress in PI3K/AKT/PTEN signaling are summarized with a focus on the links between the pathways and NOX protein in several diseases including cancer and aging.

Protection of retina by αB crystallin in sodium iodate induced retinal degeneration

Age-related macular degeneration (AMD) is a leading cause of blindness in the developed world. The retinal pigment epithelium (RPE) is a critical site of pathology in AMD and αB crystallin expression is increased in RPE and associated drusen in AMD. The purpose of this study was to investigate the role of αB crystallin in sodium iodate (NaIO₃)-induced retinal degeneration, a model of AMD in which the primary site of pathology is the RPE. Dose dependent effects of intravenous NaIO₃ (20-70 mg/kg) on development of retinal degeneration (fundus photography) and RPE and retinal neuronal loss (histology) were determined in wild type and αB crystallin knockout mice. Absence of αB crystallin augmented retinal degeneration in low dose (20 mg/kg) NaIO₃-treated mice and increased retinal cell apoptosis which was mainly localized to the RPE layer. Generation of reactive oxygen species (ROS) was observed with NaIO₃ in mouse and human RPE which increased further after αB crystallin knockout or siRNA knockdown, respectively. NaIO₃ upregulated AKT phosphorylation and peroxisome proliferator–activator receptor–γ (PPAR_γ) which was suppressed after αB crystallin siRNA knockdown. Further, PPAR_γ ligand inhibited NaIO₃-induced ROS generation. Our data suggest that αB crystallin plays a critical role in protection of NaIO₃-induced oxidative stress and retinal degeneration in part through upregulation of AKT phosphorylation and PPAR_γ expression.

Transcription factor SOX9 plays a key role in the regulation of visual cycle gene expression in the retinal pigment epithelium

The retinal pigment epithelium (RPE) performs specialized functions to support retinal photoreceptors, including regeneration of the visual chromophore. Enzymes and carrier proteins in the visual cycle function sequentially to regenerate and continuously supply 11-cis-retinal to retinal photoreceptor cells. However, it is unknown how the expression of the visual cycle genes is coordinated at the transcriptional level. Here, we show that the proximal upstream regions of six visual cycle genes contain chromatin-accessible sex-determining region Y box (SOX) binding sites, that SOX9 and LIM homeobox 2 (LHX2) are coexpressed in the nuclei of mature RPE cells, and that SOX9 acts synergistically with orthodenticle homeobox 2 (OTX2) to activate the RPE65 and retinaldehyde binding protein 1 (RLBP1) promoters and acts synergistically with LHX2 to activate the retinal G protein-coupled receptor (RGR) promoter. ChIP reveals that SOX9 and OTX2 bind to the promoter regions of RPE65, RLBP1, and RGR and that LHX2 binds to those of RPE65 and RGR in bovine RPE. ChIP with human fetal RPE cells shows that SOX9 and OTX2 also bind to the human RPE65, RLBP1, and RGR promoters. Conditional inactivation of Sox9 in mouse RPE results in reduced expression of several visual cycle genes, most dramatically Rpe65 and Rgr. Furthermore, bioinformatic analysis predicts that multiple common microRNAs (miRNAs) regulate visual cycle genes, and cotransfection of miRNA mimics with luciferase reporter constructs validated some of the predicted miRNAs. These results implicate SOX9 as a key regulator of visual cycle genes, reveal for the first time the functional role of LHX2 in the RPE, and suggest the possible regulation of visual cycle genes by common miRNAs.

Retinal pigment epithelium development, plasticity, and tissue homeostasis

The retinal pigment epithelium (RPE) is a simple epithelium interposed between the neural retina and the choroid. Although only 1 cell-layer in thickness, the RPE is a virtual workhorse, acting in several capacities that are essential for visual function and preserving the structural and physiological integrities of neighboring tissues. Defects in RPE function, whether through chronic dysfunction or age-related decline, are associated with retinal degenerative diseases including age-related macular degeneration. As such, investigations are focused on developing techniques to replace RPE through stem cell-based methods, motivated primarily because of the seemingly limited regeneration or self-repair properties of mature RPE. Despite this, RPE cells have an unusual capacity to transdifferentiate into various cell types, with the particular fate choices being highly context-dependent. In this review, we describe recent findings elucidating the mechanisms and steps of RPE development and propose a developmental framework for understanding the apparent contradiction in the capacity for low self-repair versus high transdifferentiation.

Disruption of epithelial architecture caused by loss of PTEN or by oncogenic mutant p110α/PIK3CA but not by HER2 or mutant AKT1

Genetic changes in HER2, PTEN, PIK3CA and AKT1 are all common in breast cancer and lead to the elevated phosphorylation of downstream targets of the PI3K/AKT signalling pathway. Changes in HER2, PTEN, PIK3CA and AKT have all been reported to lead to both enhanced proliferation and failures in hollow lumen formation in three dimensional epithelial culture models, but it is not clear whether these failures in lumen formation are caused by any failure in the spatial coordination of lumen formation (hollowing) or purely a failure in the apoptosis and clearance of luminal cells (cavitation). Here, we use normal murine mammary gland (NMuMG) epithelial cells, which form a hollow lumen without significant apoptosis, to compare the transformation by these four genetic changes. We find that either mutant PIK3CA expression or PTEN loss, but not mutant AKT1 E17K, cause disrupted epithelial architecture, whereas HER2 overexpression drives strong proliferation without affecting lumen formation in these cells. We also show that PTEN requires both lipid and protein phosphatase activity, its extreme C-terminal PDZ binding sequence and probably Myosin 5A to control lumen formation through a mechanism that does not correlate with its ability to control AKT, but which is selectively lost through mutation in some tumours. These findings correlate AKT-independent signalling activated by mutant PIK3CA or PTEN loss, but not strongly by HER2, with disrupted epithelial architecture and tumour formation.