miR-184 regulates ezrin, LAMP-1 expression, affects phagocytosis in human retinal pigment epithelium and is downregulated in age-related macular degeneration

The role of peripheral blood microRNAs in the pathogenesis and treatment response of age-related macular degeneration

Age-related macular degeneration is a leading cause of vision loss in aging populations, driven by complex interactions between genetic, environmental, and molecular factors. MicroRNAs have emerged as crucial regulators of cellular processes such as oxidative stress, inflammation, and angiogenesis, all of which contribute to AMD pathogenesis. This narrative review aims to summarize the involvement of peripheral blood microRNAs in the pathogenesis of AMD, focusing on key pathways such as oxidative stress, inflammation, and angiogenesis. Additionally, it explores their potential as biomarkers for predicting treatment response, particularly to anti-VEGF therapies. The potential of miRNAs as noninvasive biomarkers for early diagnosis and personalized treatment strategies is also explored, highlighting future directions for research.

Enhance Efferocytosis and Block the Macrophages-Platelets Feedback Loop for Targeted Treatment of Psoriasis

Efferocytosis of macrophages infiltrated in psoriatic lesions is mostly impaired, thus promoting the progression of psoriasis. Herein, we reveal that there exists a feedback loop between activated platelets and efferocytosis-impaired macrophages in psoriatic. Or rather, efferocytosis-impaired macrophages stimulate platelet activation, which in turn down-regulates the expression of the phagocytic receptor Mer on macrophages and polarizes macrophages to the M1-phenotype of weaker efferocytosis ability. Therefore, we construct a combined nanoplatform for more precise targeting to efferocytosis-impaired macrophages and activated platelets. The macrophage-targeting part of the nanoplatform efficiently orientates to efferocytosis-impaired macrophages through macrophage membrane encapsulation and targeting peptide modification. This increases the expression of Mer, simultaneously enhances the acidification and maturation of efferosomes, ultimately restores efferocytosis of macrophages, and promotes the phagocytosis and clearance of apoptotic cells. On the other hand, the activated platelet-targeting nanoparticles inhibit the activation of platelets, thus blocking the feedback loop and eventually preventing the down-regulation of Mer expression on macrophages. Furthermore, the combined nanoplatform suppresses the infiltration of macrophages and platelets in psoriatic lesions, reduces the release of pro-inflammatory factors such as IL-17A, and consequently improves the therapeutic effect of psoriasis and prevention of its recurrence in vivo. Collectively, this two-pronged strategy with multifunctionality in repairing efferocytosis, inhibiting platelet activation, and blocking the feedback loop may provide options available for the treatment of psoriasis.

Small Extracellular Vesicle-Associated MiRNAs in Polarized Retinal Pigmented Epithelium

Purpose

Oxidative stress in the retinal pigmented epithelium (RPE) has been implicated in age-related macular degeneration by impacting endocytic trafficking, including the formation, content, and secretion of extracellular vesicles (EVs). Using our model of polarized primary porcine RPE (pRPE) cells under chronic subtoxic oxidative stress, we tested the hypothesis that RPE miRNAs packaged into EVs are secreted in a polarized manner and contribute to maintaining RPE homeostasis.

Methods

Small EVs (sEVs) enriched for exosomes were isolated from apical and basal conditioned media from pRPE cells grown for up to four weeks with or without low concentrations of hydrogen peroxide using two sEV isolation methods, leading to eight experimental groups. The sEV miRNA expression was profiled using miRNA-Seq with Illumina MiSeq, followed by quality control and bioinformatics analysis for differential expression using the R computing environment. Expression of selected miRNAs were validated using qRT-PCR.

Results

We identified miRNA content differences carried by sEVs isolated using two ultracentrifugation-based methods. Regardless of the sEV isolation method, miR-182 and miR-183 were enriched in the cargo of apically secreted sEVs, and miR-122 in the cargo of basally secreted sEVs from RPE cells during normal homeostatic conditions. After oxidative stress, miR-183 levels were significantly decreased in the cargo of apically released sEVs from stressed RPE cells.

Conclusions

We curated RPE sEV miRNA datasets based on cell polarity and oxidative stress. Unbiased miRNA analysis identified differences based on polarity, stress, and sEV isolation methods. These findings suggest that miRNAs in sEVs may contribute to RPE homeostasis and function in a polarized manner.

Decrease of alpha-crystallin A by miR-325-3p in retinal cells under blue light exposure

Exposure to blue light can lead to retinal degeneration, causing adverse effects on eye health. Although the loss of retinal cells due to blue light exposure has been observed, the precise molecular mechanisms underlying this process remain poorly understood. In this study, we investigate the role of alpha-crystallin A (CRYAA) in neuro-retinal degeneration and their regulation by blue light. We observed significant apoptotic cell death in both the retina of rats and the cultured neuro-retinal cells. The expressions of Cryaa mRNA and protein were significantly downregulated in the retina exposed to blue light. We identified that miR-325-3p reduces Cryaa mRNA and protein by binding to its 3'-untranslated region. Upregulation of miR-325-3p destabilized Cryaa mRNA and suppresses CRYAA, whereas downregulation of miR-325-3p increased both expressions. Blue light-induced neuro-retinal cell death was alleviated by CRYAA overexpression. These results highlight the critical role of Cryaa mRNA and miR-325-3p molecular axis in blue light-induced retinal degeneration. Consequently, targeting CRYAA and miR-325-3p presents a potential strategy for protecting against blue light-induced retinal degeneration.

Profiling miRNAs in tear extracellular vesicles: a pilot study with implications for diagnosis of ocular diseases

PURPOSE

To estimate the roles of extracellular vesicles (EVs) in tears and to determine whether their profiles are associated with the type of ocular disease.

STUDY DESIGN

Cross-sectional study.

METHODS

Tear EVs were extracted from 14 healthy participants and from 21 patients with retinal diseases (age-related macular degeneration [AMD] or diabetic macular edema [DME]). The surface marker expression of tear EVs was examined, and microRNAs (miRNAs) were extracted and profiled by use of real-time PCR array. The stability of the expression of the miRNAs was determined, and their functions were assessed by network analyses. Classification accuracy was evaluated by use of a random forest classifier and k-fold cross-validation.

RESULTS

The miRNAs that were highly expressed in tear EVs were miR-323-3p, miR-548a-3p, and miR-516a-5p. The most stably expressed miRNAs independent of diseases were miR-520h and miR-146b-3p. The primary networks of the highly stably expressed endogenous miRNAs were annotated as regulation of organismal injury and abnormalities. The highly expressed miRNAs for severe retinal disease were miR-151-5p for AMD and miR-422a for DME, suggesting potential roles of tear EVs in liquid biopsy. Nine miRNAs (miR-25, miR-30d, miR-125b, miR-132, miR-150, miR-184, miR-342-3p, miR-378, and miR-518b) were identified as distinguishing individuals with AMD from healthy individuals with a classification accuracy of 91.9%.

CONCLUSIONS

The finding that tear EVs contain characteristic miRNA species indicates that they may help in maintaining homeostasis and serve as a potential tool for disease diagnosis.

microRNA-184 in the landscape of human malignancies: a review to roles and clinical significance

MicroRNAs (miRNAs) are a class of non-coding RNAs (ncRNAs) with a short length of 19-22 nucleotides. miRNAs are posttranscriptional regulators of gene expression involved in various biological processes like cell growth, apoptosis, and angiogenesis. miR-184 is a well-studied miRNA, for which most studies report its downregulation in cancer cells and tissues and experiments support its role as a tumor suppressor inhibiting malignant biological behaviors of cancer cells in vitro and in vivo. To exert its functions, miR-184 affects some signaling pathways involved in tumorigenesis like Wnt and β-catenin, and AKT/mTORC1 pathway, oncogenic factors (e.g., c-Myc) or apoptotic proteins, such as Bcl-2. Interestingly, clinical investigations have shown miR-184 with good performance as a prognostic/diagnostic biomarker for various cancers. Additionally, exogenous miR-184 in cell and xenograft animal studies suggest it as a therapeutic anticancer target. In this review, we outline the studies that evaluated the roles of miR-184 in tumorigenesis as well as its clinical significance.

Construction of miRNA-mRNA regulatory network indicates potential biomarkers for primary open-angle glaucoma

BACKGROUND

Trabecular meshwork (TM) dysfunction-induced elevation of intraocular pressure has been identified as the main risk factor of irreversible optic nerve injury in Primary open‑angle glaucoma (POAG). Increasing evidences suggest that microRNA (miRNA) plays a vital role in the pathogenesis of POAG. This study aims to construct a miRNA-mRNA regulatory network and identify biomarkers for POAG.

METHODS

miRNAs and mRNAs expression profiling of TM samples from controls and POAG patients were assessed through microarray analysis. Target genes of differentially expressed miRNAs (DEmiRNAs) were predicted by miEAA and miRNet. Then GO and KEGG pathway analysis of differentially expressed mRNAs (DEmRNAs) were performed. PPI of top 30 hub genes was identified and miRNA-mRNA network was established by STRING database and Cytoscape software. GSE27276 and GSE105269 datasets were used to verify the expression of hub genes and to predict potential biomarkers in TM and aqueous humor (AH) for POAG, respectively. Finally, GSEA analysis was conducted to estimate the main signaling pathway of POAG pathogenesis.

RESULTS

A total of 29 up-regulated and 7 down-regulated miRNAs, 923 up-regulated and 887 down-regulated mRNAs were identified in TM of POAG compared with controls. Target genes and DEmRNAs were mainly enriched in nitric oxide biosynthetic process, vasopressin-regulated water reabsorption, and so on. Through miRNA-mRNA network construction, top 30 hub genes were regulated by 24 DEmiRNAs. 8 genes were aberrantly expressed in dataset GSE27276. 3 genes (CREB1, CAPZA2, SLC2A3) and 2 miRNAs (miR-106b-5p, miR-15a-5p) were identified as potential biomarkers for POAG in TM and AH, respectively. GSEA analysis revealed that these 3 genes modulated POAG through different pathways.

CONCLUSION

In this study, construction of miRNA-mRNA network and identification of biomarkers provide a novel insight into the pathogenesis, early diagnosis and treatment for POAG.

Knockout of miR-184 in zebrafish leads to ocular abnormalities by elevating p21 levels

miR-184 is one of the most abundant miRNAs expressed in the lens and corneal tissue. Mutations in the seed region of miR-184 are responsible for inherited anterior segment dysgenesis. Animal models recapitulating miR-184-related anterior segment dysgenesis are still lacking, and the molecular basis of ocular abnormalities caused by miR-184 dysfunction has not been well elucidated in vivo. In the present study, we constructed a miR-184-/- zebrafish line by destroying both two dre-mir-184 paralogs with CRISPR-Cas9 technology. Although there were no gross developmental defects, the miR-184-/- zebrafish displayed microphthalmia and cataract phenotypes. Cytoskeletal abnormalities, aggregation of γ-crystallin, and lens fibrosis were induced in miR-184-/- lenses. However, no obvious corneal abnormalities were observed in miR-184-/- zebrafish. Instead of apoptosis, deficiency of miR-184 led to aberrant cell proliferation and a robust increase in p21 levels in zebrafish eyes. Inhibition of p21 by UC2288 compromised the elevation of lens fibrosis markers in miR-184-/- lenses. RNA-seq demonstrated that levels of four transcriptional factors HSF4, Sox9a, CTCF, and Smad6a, all of which could suppress p21 expression, were reduced in miR-184-/- eyes. The predicted zebrafish miR-184 direct target genes (e.g., atp1a3a and nck2a) were identified and verified in miR-184-/- eye tissues. The miR-184-/- zebrafish is the first animal model mimicking miR-184-related anterior segment dysgenesis and could broaden our understanding of the roles of miR-184 in eye development.

MicroRNAs as potential biomarkers and therapeutic targets in age-related macular degeneration

Age-related macular degeneration (AMD) involves degenerative and neovascular alteration in the macular region of the retina resulting in central vision loss. AMD can be classified into dry (dAMD) and wet AMD (wAMD). There is no established treatment for dAMD, and therapies available for wAMD have limited success. Diagnosis in early AMD stages is difficult due to the absence of clinical symptoms. Currently, imaging tests are used in the diagnosis of AMD, but cannot predict the clinical course. The clinical limitations to establishing a diagnosis of AMD have led to exploration for innovative and more sensitive tests to support the diagnosis and prognosis of the disease. MicroRNAs (miRNAs) are small single-stranded non-coding RNA molecules that negatively regulate genes by post-transcriptional gene silencing. Because these molecules are dysregulated in various processes implicated in the pathogenesis of AMD, they could contribute to the early detection of the disease and monitoring of its progression. Studies of miRNA profiling have indicated several miRNAs as potential diagnostic biomarkers of AMD, but no approved biomarker is available at present for early AMD detection. Thus, understanding the function of miRNAs in AMD and their use as potential biomarkers may lead to future advances in diagnosis and treatment. Here we present a brief review of some of the miRNAs involved in regulating pathological processes associated with AMD and discuss several candidate miRNAs proposed as biomarkers or therapeutic targets for AMD.

Retinal Pigment Epithelium Cell Development: Extrapolating Basic Biology to Stem Cell Research

The retinal pigment epithelium (RPE) forms an important cellular monolayer, which contributes to the normal physiology of the eye. Damage to the RPE leads to the development of degenerative diseases, such as age-related macular degeneration (AMD). Apart from acting as a physical barrier between the retina and choroidal blood vessels, the RPE is crucial in maintaining photoreceptor (PR) and visual functions. Current clinical intervention to treat early stages of AMD includes stem cell-derived RPE transplantation, which is still in its early stages of evolution. Therefore, it becomes essential to derive RPEs which are functional and exhibit features as observed in native human RPE cells. The conventional strategy is to use the knowledge obtained from developmental studies using various animal models and stem cell-based exploratory studies to understand RPE biogenies and developmental trajectory. This article emphasises such studies and aims to present a comprehensive understanding of the basic biology, including the genetics and molecular pathways of RPE development. It encompasses basic developmental biology and stem cell-based developmental studies to uncover RPE differentiation. Knowledge of the in utero developmental cues provides an inclusive methodology required for deriving RPEs using stem cells.

Potential gene identification and pathway crosstalk analysis of age-related macular degeneration

Age-related macular degeneration (AMD), the most prevalent visual disorder among the elderly, is confirmed as a multifactorial disease. Studies demonstrated that genetic factors play an essential role in its pathogenesis. Our study aimed to make a relatively comprehensive study about biological functions of AMD related genes and crosstalk of their enriched pathways. 1691 AMD genetic studies were reviewed, GO enrichment and pathway crosstalk analyses were conducted to elucidate the biological features of these genes and to demonstrate the pathways that these genes participate. Moreover, we identified novel AMD-specific genes using shortest path algorithm in the context of human interactome. We retrieved 176 significantly AMD-related genes. GO results showed that the most significant term in each of these three GO categories was: signaling receptor binding (P_BH = 4.835 × 10⁻⁷), response to oxygen-containing compound (P_BH = 2.764 × 10⁻²¹), and extracellular space (P_BH = 2.081 × 10⁻¹⁹). The pathway enrichment analysis showed that complement pathway is the most enriched. The pathway crosstalk study showed that the pathways could be divided into two main modules. These two modules were connected by cytokine-cytokine receptor interaction pathway. 42 unique genes potentially participating AMD development were obtained. The aberrant expression of the mRNA of FASN and LRP1 were validated in AMD cell and mouse models. Collectively, our study carried out a comprehensive analysis based on genetic association study of AMD and put forward several evidence-based genes for future study of AMD.

The Role of Dysregulated miRNAs in the Pathogenesis, Diagnosis and Treatment of Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is an eye disease causing damage to the macular region of the retina where most of the photoreceptors responsible for central visual acuity are located. MicroRNAs (miRNAs) are small single-stranded non-coding RNA molecules that negatively regulate genes by silent post-transcriptional gene expressions. Previous studies have shown that changes in specific miRNAs are involved in the pathogenesis of eye diseases, including AMD. Altered expressions of miRNAs are related to disturbances of regulating oxidative stress, inflammation, angiogenesis, apoptosis and phagocytosis, which are known factors in the pathogenesis of AMD. Moreover, dysregulation of miRNA is involved in drusen formation. Thus, miRNAs may be used as potential molecular biomarkers for the disease and, furthermore, tailoring therapeutics to particular disturbances in miRNAs may, in the future, offer hope to prevent irreversible vision loss. In this review, we clarify the current state of knowledge about the influence of miRNA on the pathogenesis, diagnosis and treatment of AMD. Our study material consisted of publications, which were found in PubMed, Google Scholar and Embase databases using “Age-related macular degeneration”, “miRNA”, “AMD biomarkers”, “miRNA therapeutics” and “AMD pathogenesis” as keywords. Paper search was limited to articles published from 2011 to date. In the section “Retinal, circulating and vitreous body miRNAs found in human studies”, we limited the search to studies with patients published in 2016–2021.

MicroRNA-184 attenuates hypoxia and oxidative stress-related injury via suppressing apoptosis, DNA damage and angiogenesis in an in vitro age-related macular degeneration model

Age-related macular degeneration (AMD) is one of the leading causes of blindness worldwide, particularly in developed countries. Recently, microRNAs (miRs) have become popular research area to develop new treatment options of AMD. However, interaction between hsa-miR-184 and AMD remain largely unexplored. In this study, sub-lethal levels of Deforoxamine Mesylate salt (DFX) and H₂O₂ were applied to ARPE-19 cells to establish a severe in vitro AMD model, via durable hypoxia and oxidative stress. We found that up-regulation of miR-184 level in AMD can suppress hypoxia-related angiogenic signals through HIF-1α/VEGF/MMPs axis. Also, miR-184 suppressed the hypoxia sensor miR-155 and genes in the EGFR/PI3K/AKT pathway, which is an alternative pathway in angiogenesis. To investigate the mechanism behind this protective effect, we evaluated the impact of miR-184 on retinal apoptosis in a model of AMD. miR-184 inhibited retinal apoptosis by upregulating BCL-2 and downregulating pro-apoptototic BAX, TRAIL, Caspase 3 and 8 signals as well as p53. Taken together, miR-184 attenuates retinal cell damage induced by severe AMD pathologies through suppressing hypoxia, angiogenesis and apoptosis. The safety profile of miR-184 was observed to be similar to Bevacizumab, which is in wide use clinically, but miR-184 was found to provide a more effective therapeutic potential by regulating simultaneously multiple pathologies.

MicroRNAs as Regulators of Phagocytosis

MicroRNAs (miRNAs) are short non-coding RNAs that regulate gene expression and thus act as important regulators of cellular phenotype and function. As their expression may be dysregulated in numerous diseases, they are of interest as biomarkers. What is more, attempts of modulation of some microRNAs for therapeutic reasons have been undertaken. In this review, we discuss the current knowledge regarding the influence of microRNAs on phagocytosis, which may be exerted on different levels, such as through macrophages polarization, phagosome maturation, reactive oxygen species production and cytokines synthesis. This phenomenon plays an important role in numerous pathological conditions.

Differential Circulating MicroRNA Expression in Age-Related Macular Degeneration

This study explored the expression of several miRNAs reported to be deregulated in age-related macular degeneration (AMD). Total RNA was isolated from sera from patients with dry AMD (n = 12), wet AMD (n = 14), and controls (n = 10). Forty-two previously investigated miRNAs were selected based on published data and their role in AMD pathogenesis, such as angiogenic and inflammatory effects, and were co-analysed using a miRCURY LNA miRNA SYBR^® Green PCR kit via quantitative real-time polymerase chain reaction (qRT-PCR) to validate their presence. Unsupervised hierarchical clustering indicated that AMD serum specimens have a different miRNA profile to healthy controls. We successfully validated the differentially regulated miRNAs in serum from AMD patients versus controls. Eight miRNAs (hsa-let-7a-5p, hsa-let-7d-5p, hsa-miR-23a-3p, hsa-miR-301a-3p, hsa-miR-361-5p, hsa-miR-27b-3p, hsa-miR-874-3p, hsa-miR-19b-1-5p) showed higher expression in the serum of dry AMD patients than wet AMD patients and compared with healthy controls. Increased quantities of certain miRNAs in the serum of AMD patients indicate that these miRNAs could potentially serve as diagnostic AMD biomarkers and might be used as future AMD treatment targets. The discovery of significant serum miRNA biomarkers in AMD patients would provide an easy screening tool for at-risk populations.

MicroRNA regulation of critical retinal pigment epithelial functions

MicroRNAs are short, evolutionarily conserved noncoding RNAs that are critical for the control of normal cellular physiology. In the retina, photoreceptors are highly specialized neurons that transduce light into electrical signals. Photoreceptors, however, are unable to process visual stimuli without the support of the retinal pigment epithelium (RPE). The RPE performs numerous functions to aid the retina, including the generation of visual chromophore and metabolic support. Recent work has underscored how microRNAs enable vision through their contributions to RPE functions. This review focuses on the biogenesis and control of microRNAs in rodents and humans, the roles microRNAs play in RPE function and degeneration, and how microRNAs could serve as potential therapeutics and biomarkers for visual diseases.

Proteomic and phosphoproteomic analyses identify liver-related signaling in retinal pigment epithelial cells during EMT

Epithelial-mesenchymal transition (EMT) of the retinal pigment epithelium (RPE) is associated with several blinding retinal diseases. Using proteomics and phosphoproteomics studies of human induced pluripotent stem cell-derived RPE monolayers with induced EMT, we capture kinase/phosphatase signaling cascades 1 h and 12 h after induction to better understand the pathways mediating RPE EMT. Induction by co-treatment with transforming growth factor β and tumor necrosis factor alpha (TGNF) or enzymatic dissociation perturbs signaling in many of the same pathways, with striking similarity in the respective phosphoproteomes at 1 h. Liver hyperplasia and hepatocyte growth factor (HGF)-MET signaling exhibit the highest overall enrichment. We also observe that HGF and epidermal growth factor signaling, two cooperative pathways inhibited by EMT induction, regulate the RPE transcriptional profile.

Investigation of Key Signaling Pathways Associating miR-204 and Common Retinopathies

MicroRNAs are a large group of small noncoding RNAs that work in multiple cellular pathways. miR-204, as one of the key axes in the development, maintenance, and pathogenesis of the retina, plays several roles by modulating its target genes. This study was aimed at evaluating the target genes of miR-204 involved in the development and progression of common retinopathies such as glaucoma, retinoblastoma, and age-related macular degeneration. In this study, three datasets related to retinopathies (GSE50195, GSE27276, and GSE97508) were selected from Gene Expression Omnibus. miR-204 target genes were isolated from TargeScan. The shares between retinopathy and miR-204 target genes were then categorized. Using Enrichr and STRING, we highlighted the signaling pathways and the relationships between the proteins. SHC1 events in ERBB2, adherent junction's interactions, NGF signaling via TRKA from the plasma membrane, IRF3-mediated activation of type 1 IFN, pathways in upregulated genes and G0 and early G1, RORA-activated gene expression, PERK-regulated gene expression, adherent junction's interactions, and CREB phosphorylation pathways in downregulated genes were identified in glaucoma, retinoblastoma, and age-related macular degeneration. WEE1, SMC2, HMGB1, RRM2, and POLA1 proteins were also observed to be involved in the progression and invasion of retinoblastoma; SLC24A2 and DTX4 in age-related macular degeneration; and EPHB6, EFNB3, and SHC1 in glaucoma. Continuous bioinformatics analysis has shown that miR-204 has a significant presence and expression in retinal tissue, and approximately 293 genes are controlled and regulated by miR-204 in this tissue; also, target genes of miR-204 have the potential to develop various retinopathies; thus, a study of related target genes can provide appropriate treatment strategies in the future.

Therapeutic effects of mesenchymal stem cells-derived extracellular vesicles' miRNAs on retinal regeneration: a review

Extracellular vesicles (EVs), which consist of microvesicles and exosomes, are secreted from all cells to transform vital information in the form of lipids, proteins, mRNAs and small RNAs such as microRNAs (miRNAs). Many studies demonstrated that EVs' miRNAs have effects on target cells. Numerous people suffer from the blindness caused by retinal degenerations. The death of retinal neurons is irreversible and creates permanent damage to the retina. In the absence of acceptable cures for retinal degenerative diseases, stem cells and their paracrine agents including EVs have become a promising therapeutic approach. Several studies showed that the therapeutic effects of stem cells are due to the miRNAs of their EVs. Considering the effects of microRNAs in retinal cells development and function and studies which provide the possible roles of mesenchymal stem cells-derived EVs miRNA content on retinal diseases, we focused on the similarities between these two groups of miRNAs that could be helpful for promoting new therapeutic techniques for retinal degenerative diseases.

Functional microRNA targetome undergoes degeneration-induced shift in the retina

BACKGROUND

MicroRNA (miRNA) play a significant role in the pathogenesis of complex neurodegenerative diseases including age-related macular degeneration (AMD), acting as post-transcriptional gene suppressors through their association with argonaute 2 (AGO2) - a key member of the RNA Induced Silencing Complex (RISC). Identifying the retinal miRNA/mRNA interactions in health and disease will provide important insight into the key pathways miRNA regulate in disease pathogenesis and may lead to potential therapeutic targets to mediate retinal degeneration.

METHODS

To identify the active miRnome targetome interactions in the healthy and degenerating retina, AGO2 HITS-CLIP was performed using a rodent model of photoreceptor degeneration. Analysis of publicly available single-cell RNA sequencing (scRNAseq) data was performed to identify the cellular location of AGO2 and key members of the microRNA targetome in the retina. AGO2 findings were verified by in situ hybridization (RNA) and immunohistochemistry (protein).

RESULTS

Analysis revealed a similar miRnome between healthy and damaged retinas, however, a shift in the active targetome was observed with an enrichment of miRNA involvement in inflammatory pathways. This shift was further demonstrated by a change in the seed binding regions of miR-124-3p, the most abundant retinal AGO2-bound miRNA, and has known roles in regulating retinal inflammation. Additionally, photoreceptor cluster miR-183/96/182 were all among the most highly abundant miRNA bound to AGO2. Following damage, AGO2 expression was localized to the inner retinal layers and more in the OLM than in healthy retinas, indicating a locational miRNA response to retinal damage.

CONCLUSIONS

This study provides important insight into the alteration of miRNA regulatory activity that occurs as a response to retinal degeneration and explores the miRNA-mRNA targetome as a consequence of retinal degenerations. Further characterisation of these miRNA/mRNA interactions in the context of the degenerating retina may provide an important insight into the active role these miRNA may play in diseases such as AMD.

Roles of miR-204 in retinal development and maintenance

The retina is the innermost part of the eye of most vertebrates and it is essential for vision. The development, maintenance, and function of this laminated structure is tightly regulated by numerous genes. Deficiencies in the expression of these genes as well as deregulation of various molecular mechanisms can cause retinopathies and blindness. MicroRNAs (miRNAs) are one of the most important and effective molecular regulatory mechanisms that underlie the biology of the retina. miRNAs have specific functional roles in the development and maintenance of different retinal layers and retinal cell types. While previous studies have reported a large number of miRNAs linked to development, maintenance and diseases of the retina, no comprehensive study has properly discussed and integrated data from these studies. Given the particular importance of miR-204 in retinal biology, we intend to critically discuss the expression and functional significance of this miRNA in the development, maintenance, and pathologies of the retina. Moreover, we explore biological processes through which miR-204 influences retinal pathophysiology. This review highlights the crucial functions of miR-204 in the retina and suggests the putative mechanism of miR-204 action in retinal biology.

MicroRNAs in the regulation of autophagy and their possible use in age-related macular degeneration therapy

Age-related macular degeneration (AMD) is a progressive sight-impairing disease of the elderly. The pathogenic mechanisms of AMD are not well understood although both genetic and many environmental factors have been associated with the development of AMD. One clinical hallmark of AMD is the detrimental aggregation of damaged proteins. Recently, it has been suggested that the weakening of autophagy clearance is an important mechanism in the pathogenesis of AMD. Autophagy is important in the removal of damaged or no longer needed cellular material and its recycling. A considerable number of autophagy-targeting microRNAs (miRNAs), small RNA molecules and epigenetic regulators have been found to be either up- or down-regulated in AMD patients and experimental models. The important role of autophagy-targeting miRNAs is supported by several studies and can open the prospect of the use of these miRNAs in the therapy for AMD.

The Impact of miRNAs in Health and Disease of Retinal Pigment Epithelium

MicroRNAs (miRNAs), a class of non-coding RNAs, are essential key players in the control of biological processes in both physiological and pathological conditions. miRNAs play important roles in fine tuning the expression of many genes, which often have roles in common molecular networks. miRNA dysregulation thus renders cells vulnerable to aberrant fluctuations in genes, resulting in degenerative diseases. The retinal pigment epithelium (RPE) is a monolayer of polarized pigmented epithelial cells that resides between the light-sensitive photoreceptors (PR) and the choriocapillaris. The demanding physiological functions of RPE cells require precise gene regulation for the maintenance of retinal homeostasis under stress conditions and the preservation of vision. Thus far, our understanding of how miRNAs function in the homeostasis and maintenance of the RPE has been poorly addressed, and advancing our knowledge is central to harnessing their potential as therapeutic agents to counteract visual impairment. This review focuses on the emerging roles of miRNAs in the function and health of the RPE and on the future exploration of miRNA-based therapeutic approaches to counteract blinding diseases.

circRNA-miRNA-mRNA network in age-related macular degeneration: From construction to identification

The aim of the present study was to investigate the pathogenesis of age-related macular degeneration (AMD) by constructing a regulatory circRNA-miRNA-mRNA network. By adjusting the P value to <0.05 and the absolute log value of fold change to >0.25, 2920 and 1057 differentially expressed mRNAs were identified from GSE50195 and GSE29801, respectively. Based on a literature review, Starbase database analysis, and RNA hybrid assays, we obtained 77 miRNA-mRNA and 331 circRNA-miRNA pairs. After combining these pairs, we constructed a circRNA-miRNA-mRNA network possessing 303 circRNA nodes, 4 miRNA nodes, 51 mRNA nodes, and 408 edges. By utilizing protein-protein network analysis, the MCODE algorithm, and the highest degree of circRNA node, we identified the regulatory axis of hsa_circRNA7329/hsa-miR-9/SCD. Hsa_circRNA7329 may regulate SCD through hsa-miR-9 to promote macrophage-mediated inflammation and pathologic angiogenesis, which lead to AMD development. However, the underlying details require further investigation.

Mutation-Independent Therapies for Retinal Diseases: Focus on Gene-Based Approaches

Gene therapy is proving to be an effective approach to treat or prevent ocular diseases ensuring a targeted, stable, and regulated introduction of exogenous genetic material with therapeutic action. Retinal diseases can be broadly categorized into two groups, namely monogenic and complex (multifactorial) forms. The high genetic heterogeneity of monogenic forms represents a significant limitation to the application of gene-specific therapeutic strategies for a significant fraction of patients. Therefore, mutation-independent therapeutic strategies, acting on common pathways that underly retinal damage, are gaining interest as complementary/alternative approaches for retinal diseases. This review will provide an overview of mutation-independent strategies that rely on the modulation in the retina of key genes regulating such crucial degenerative pathways. In particular, we will describe how gene-based approaches explore the use of neurotrophic factors, microRNAs (miRNAs), genome editing and optogenetics in order to restore/prolong visual function in both outer and inner retinal diseases. We predict that the exploitation of gene delivery procedures applied to mutation/gene independent approaches may provide the answer to the unmet therapeutic need of a large fraction of patients with genetically heterogeneous and complex retinal diseases.

Detrimental Effects of UVB on Retinal Pigment Epithelial Cells and Its Role in Age-Related Macular Degeneration

Retinal pigment epithelial (RPE) cells are an essential part of the human eye because they not only mediate and control the transfer of fluids and solutes but also protect the retina against photooxidative damage and renew photoreceptor cells through phagocytosis. However, their function necessitates cumulative exposure to the sun resulting in UV damage, which may lead to the development of age-related macular degeneration (AMD). Several studies have shown that UVB induces direct DNA damage and oxidative stress in RPE cells by increasing ROS and dysregulating endogenous antioxidants. Activation of different signaling pathways connected to inflammation, cell cycle arrest, and intrinsic apoptosis was reported as well. Besides that, essential functions like phagocytosis, osmoregulation, and water permeability of RPE cells were also affected. Although the melanin within RPE cells can act as a photoprotectant, this photoprotection decreases with age. Nevertheless, the changes in lens epithelium-derived growth factor (LEDGF) and autophagic activity or application of bioactive compounds from natural products can reverse the detrimental effect of UVB. Additionally, in vivo studies on the whole retina demonstrated that UVB irradiation induces gene and protein level dysregulation, indicating cellular stress and aberrations in the chromosome level. Morphological changes like retinal depigmentation and drusen formation were noted as well which is similar to the etiology of AMD, suggesting the connection of UVB damage with AMD. Therefore, future studies, which include mechanism studies via in vitro or in vivo and other potential bioactive compounds, should be pursued for a better understanding of the involvement of UVB in AMD.

MicroRNA-184 negatively regulates corneal epithelial wound healing via targeting CDC25A, CARM1, and LASP1

Background

MicroRNAs (miRNAs) play critical roles in corneal development and functional homeostasis. Our previous study identified miR-184 as one of the most highly expressed miRNAs in the corneal epithelium. Even though its expression level plummeted dramatically during corneal epithelial wound healing (CEWH), its precise role in mediating corneal epithelial renewal was unresolved. The present study aimed to reveal the function and mechanism of miR-184 in regulating CEWH.

Methods

Quantitative RT-PCR analysis characterized the miR-184 expression pattern during CEWH in mice. Ectopic miR-184 injection determined its effect on this process in vivo. We evaluated the effects of miR-184 and its target genes on the proliferation, cell cycle, and migration of human corneal epithelial cells (HCECs) using MTS, flow cytometry, and wound-healing assay, respectively. Bioinformatic analysis, in conjunction with gene microarray analysis and cell-based luciferase assays, pinpointed gene targets of miR-184 contributing to CEWH.

Results

MiR-184 underwent marked downregulation during mouse CEWH. Ectopic miR-184 overexpression delayed this process in mice. Furthermore, miR-184 transfection into HCECs significantly inhibited cell proliferation, cell cycle progression, and cell migration. MiR-184 directly targeted CDC25A, CARM1, and LASP1, and downregulated their expression in HCECs. CARM1 downregulation inhibited both HCEC proliferation and migration, whereas a decrease in LASP1 gene expression only inhibited migration.

Conclusions

Our results demonstrate that miR-184 inhibits corneal epithelial cell proliferation and migration via targeting CDC25A, CARM1, and LASP1, suggesting it acts as a negative modulator during CEWH. Therefore, identifying strategies to suppress miR-184 expression levels has the potential to promote CEWH.

MicroRNA-184 is a key molecule responsible for the transforming growth factor-β2 -induced epithelial-mesenchymal transition in human lens epithelial-B3 cells

BACKGROUND

TGF-β2-induced epithelial-mesenchymal transition (EMT) is an important mechanism for posterior capsule opacity (PCO) in lens epithelial cells (LECs). This study aimed to investigate if MicroRNA-184 (miR-184) plays a role in the TGF-β2-induced EMT in LECs.

METHODS

Human LECs (HLE-B3 cells) were used in this study. Quantitative real-time polymerase chain reaction (PCR) (qRT-PCR) was performed to analyse miR-184 expressions in HLE-B3 treated with TGF-β2 at different concentrations (0-15 ng/mL) and different time (10 ng/mL, 0-48 hours). After transfection of miR-184 mimics or miR-184 inhibitor, cells were treated with 10 ng/mL TGF-β2 for 24 hours, and the expression levels of miR-184, E-cadherin, vimentin, zinc finger E-box binding homeobox 2 (ZEB2), α-Smooth muscle actin (α-SMA), Collagen 1 and bin3 were determined by qRT-PCR and Western blot, respectively.

RESULTS

TGF-β2 treatment significantly downregulated E-cadherin and upregulated vimentin generally in a dose-dependent and time-dependent manner. TGF-β2 treatment significantly elevated the level of miR-184 in both dose- and time-dependent manners. In addition, transfection of miR-184 inhibitor RNA significantly attenuated TGF-β2-induced downregulation of E-cadherin as well as upregulation of vimentin, ZEB2, α-SMA and Collagen 1, whereas transfection of miR-184 mimic further enhanced the effects of TGF-β2 on the expressions of these markers. Furthermore, TGF-β2 treatment significantly downregulated bin3, and transfection of miR-184 mimic and miR-184 inhibitor significantly enhanced and attenuated the inhibition effect of TGF-β2 on bin3, respectively.

CONCLUSIONS

miR-184 plays a key role in the TGF-β2-induced EMT in LECs, and bin3 may be a downstream protein.

A Circulating MicroRNA Profile in a Laser-Induced Mouse Model of Choroidal Neovascularization

Choroidal neovascularization (CNV) is a pathological process in which aberrant blood vessels invade the subretinal space of the mammalian eye. It is a characteristic feature of the prevalent neovascular age-related macular degeneration (nAMD). Circulating microRNAs (cmiRNAs) are regarded as potentially valuable biomarkers for various age-related diseases, including nAMD. Here, we investigated cmiRNA expression in an established laser-induced CNV mouse model. Upon CNV induction in C57Bl/6 mice, blood-derived cmiRNAs were initially determined globally by RNA next generation sequencing, and the most strongly dysregulated cmiRNAs were independently replicated by quantitative reverse transcription PCR (RT-qPCR) in blood, retinal, and retinal pigment epithelium (RPE)/choroidal tissue. Our findings suggest that two miRNAs, mmu-mir-486a-5p and mmur-mir-92a-3p, are consistently dysregulated during CNV formation. Furthermore, in functional in vitro assays, a significant impact of mmu-mir-486a-5p and mmu-mir-92a-3p on murine microglial cell viability was observed, while mmu-mir-92a-3p also showed an impact on microglial mobility. Taken together, we report a robust dysregulation of two miRNAs in blood and RPE/choroid after laser-induced initiation of CNV lesions in mice, highlighting their potential role in pathology and eventual therapy of CNV-associated complications.

MiR-505 promotes M2 polarization in choroidal neovascularization model mice by targeting transmembrane protein 229B

We aimed to analyse the relative abundance of miR-505 in age-related macular degeneration (AMD) and elucidate its underlying mechanisms. Relative expression of miR-505 was analysed by real-time polymerase chain reaction (PCR). Macrophage polarization was characterized by measurement of molecular markers including Ym-1, Arg-1, TNF-α and iNOS via both real-time PCR and Western blot. Vascular endothelial growth factor (VEGF) content was determined by enzyme-linked immunosorbent assay. Choroidal neovascularization (CNV) formation was evaluated by choroidal flat mount technique. The regulatory action of miR-505-5p on 3'UTR of Transmembrane Protein 229B (TMEM229B) was interrogated by luciferase reporter assay. miR-505 was aberrantly upregulated in both AMD and laser-induced choroidal neovascularization mouse model. Administration with miR-505 specific inhibitor suppressed M2 polarization in CNV mice as indicated by decreasing both Ym-1 and Arg-1. Meanwhile, VEGF expression and CNV formation were greatly suppressed by miR-505 inhibition as well. The similar phenotype was consolidated in Prostaglandin E2 (PGE2)-stimulated bone marrow-derived macrophages. At the molecular level, miR-505-5p directly targeted and negatively regulated TMEM229B expression, while forced ectopic expression of TMEM229B significantly rescued miR-505-imposed M2 polarization. Our data have uncovered the critical contribution of miR-505 in AMD, which is predominantly mediated by downregulation of TMEM229B.

Deletion of miR-182 Leads to Retinal Dysfunction in Mice

Purpose

MicroRNA-182 (miR-182) is abundantly expressed in mammalian retinas; however, the association between miR-182 and retinal function remains unclear. In this study, we explored whether miR-182 contributes to functional decline in retinas using a miR-182 depleted mouse.

Methods

Electroretinogram (ERG) amplitudes at different ages were measured in miR-182 knockout (KO) mice. The thickness and lamination of retinas were assessed using a color fundus camera and high-resolution optical coherence tomography. Expression levels of key photoreceptor-specific genes and the miR-183/96/182 cluster (miR-183C) were quantified using quantitative real-time PCR. RNA sequencing and light-induced damage were carried out to observe the changes in the retinal transcriptome and sensitivity to light damage in the miR-182 KO mice.

Results

The ERG recording reveals that the ERG response amplitude decreased both at early and later ages when compared with control littermates. The expression of some key photoreceptor-specific genes was down-regulated with deletion of miR-182 in retina. RNA sequencing indicated that some biological processes of visual system were affected, and the numbers of potential target genes of miR-182 were presented in the mouse retina using bioinformatics analysis. The miR-182 KO mice were characterized by progressively losing the outer segment after being treated with light-damage exposure. The thickness and lamination of retina as well as compensatory expression of miR-183C showed no apparent changes in retina of miR-182 KO mice under normal laboratory lighting condition.

Conclusions

Our findings provided new insights into the relationship between the miR-182 and retinal development and revealed that miR-182 may play a critical role in maintaining retinal function.

Rev-Erbα and Photoreceptor Outer Segments modulate the Circadian Clock in Retinal Pigment Epithelial Cells

Retinal photoreceptor outer segments (POS) are renewed daily through phagocytosis by the adjacent retinal pigment epithelial (RPE) monolayer. Phagocytosis is mainly driven by the RPE circadian clock but the underlying molecular mechanisms remain elusive. Using ARPE-19 (human RPE cell-line) dispersed and monolayer cell cultures, we investigated the influence of cellular organization on the RPE clock and phagocytosis genes. PCR analysis revealed rhythmic expression of clock and phagocytosis genes in all ARPE-19 cultures. Monolayers had a tendency for higher amplitudes of clock gene oscillations. In all conditions ARNTL, CRY1, PER1-2, REV-ERBα, ITGB5, LAMP1 and PROS1 were rhythmically expressed with REV-ERBα being among the clock genes whose expression showed most robust rhythms in ARPE-19 cells. Using RPE-choroid explant preparations of the mPer2^Luc knock-in mice we found that Rev-Erbα deficiency induced significantly longer periods and earlier phases of PER2-bioluminescence oscillations. Furthermore, early phagocytosis factors β₅-Integrin and FAK and the lysosomal marker LAMP1 protein levels are rhythmic. Finally, POS incubation affects clock and clock-controlled phagocytosis gene expression in RPE monolayers in a time-dependent manner suggesting that POS can reset the RPE clock. These results shed some light on the complex interplay between POS, the RPE clock and clock-controlled phagocytosis machinery which is modulated by Rev-Erbα.

Expression levels and significance of miR-184 and miR-126 in burned rats

Expression levels and significance of miR-184 and miR-126 in burned rats were investigated. A total of 30 healthy rats were selected to construct a burn rat model, and another 10 healthy rats as the control group. The modeled rats were divided into groups I, II and III according to burn area, 10 for each group. The reverse transcription-quantitative polymerase chain reaction (RT-q.PCR) was used to detect the expression of miR-184 and miR-126 in the serum of three groups of burned rats, and ELISA was employed to detect the expression levels in peripheral blood and the correlation. There was no difference in the expression levels of miR-184 and miR-126 among the four groups of rats before modeling (P>0.05). Those of miR-184 and miR-126 at each time point were lower than those at the previous one in groups I, II and III (P<0.05). There was no significant change in the expression levels of miR-184 and miR-126 in the control group (P>0.05). At the same time point, those of miR-184 and miR-126 decreased with the increase of burn degree, and the difference was statistically significant between every two groups (P<0.05). The results of Pearson's correlation analysis revealed that the expression level of miR-184 was positively correlated with that of miR-126 (r=0.832, P=0.002). miR-184 and miR-126 were positively correlated with burn degree (r=0.901, P=0.001, r=0.775, P=0.001) and time after burn (r=0.732, P=0.004, r=0.753, P=0.002). The expression levels of miR-184 and miR-126 decrease in burned rats. The changes of their levels may be used as a reference standard for clinical efficacy evaluation to evaluate burn degree, preventing burn wounds from deepening.

Identification of aberrantly methylated differentially expressed genes in age-related macular degeneration

DNA methylation plays a significant role in many diseases. Age-related macular degeneration (AMD) is a leading cause of vision loss for people aged 50 years and above, but the etiology and pathogenesis are largely unknown. This study aimed to identify the aberrantly methylated differentially expressed genes (DEGs) in AMD and predict the related pathways on the basis of public data.Aberrant methylation can influence the functions of key genes by altering their expression. Here, we found out DEGs by overlapping public microarray data (GSE29801 and GSE102952). Functional and enrichment analyses of selected genes were performed using the DAVID database. Subsequently, protein-protein interaction (PPI) networks were constructed by using STRING and visualized in cytoscape to determine hub genes. Finally, we collected AMD patients' blood samples to identify the methylation statuses of these hub genes by using methylated DNA immunoprecipitation.In total, 156 hypermethylation-low expression genes and 127 hypomethylation-high expression genes were predicted. The hypermethylation-low expression genes were enriched in biological processes of response to cardiac conduction, ATP binding, and cell-cell junction assembly. The top 5 hub genes of the PPI network were HSP90AA1, HSPA1L, HSPE1, HSP90B1, and NOP56. Meanwhile, the hypomethylation-high expression genes were enriched in the biological processes of response to positive regulation of the MAPK cascade, actin cytoskeleton reorganization, dentate gyrus development, and cell migration. The top 5 hub genes of this PPI network were PIK3R1, EZR, IGF2, SLC2A1, and CDKN1C. Moreover, the methylation statuses of NOP56, EZR, IGF2, SLC2A1, CDKN1C were confirmed to be altered in the blood of AMD patients.This study indicated possible aberrantly methylated DEGs and differentially expressed pathways in AMD by bioinformatics analysis, providing novel insights for unraveling the pathogenesis of AMD. Hub genes, including NOP56, EZR, IGF2, SLC2A1, CDKN1C, might serve as aberrant methylation-based candidate biomarkers for AMD in future applications.

Conditional Dicer1 depletion using Chrnb4-Cre leads to cone cell death and impaired photopic vision

Irreversible photoreceptor cell death is a major cause of blindness in many retinal dystrophies. A better understanding of the molecular mechanisms underlying the progressive loss of photoreceptor cells remains therefore crucial. Abnormal expression of microRNAs (miRNAs) has been linked with the aetiology of a number of retinal dystrophies. However, their role during the degenerative process remains poorly understood. Loss of cone photoreceptors in the human macula has the greatest impact on sight as these cells provide high acuity vision. Using a Chrnb4-cre; Dicerflox/flox conditional knockout mouse (Dicer CKO) to delete Dicer1 from cone cells, we show that cone photoreceptor cells degenerate and die in the Dicer-deleted retina. Embryonic eye morphogenesis appeared normal in Dicer CKO mice. Cone photoreceptor abnormalities were apparent by 3 weeks of age, displaying either very short or absent outer segments. By 4 months 50% of cones were lost and cone function was impaired as assessed by electroretinography (ERG). RNAseq analysis of the Dicer CKO retina revealed altered expression of genes involved in the visual perception pathway. These data show that loss of Dicer1 leads to early-onset cone cell degeneration and suggest that Dicer1 is essential for cone photoreceptor survival and homeostasis.

Proteomics of Human Retinal Pigment Epithelium (RPE) Cells

Retinal pigment epithelium (RPE) are specialized, multifunctional cells in the retina that form a monolayer of cuboidal, polarized cells adjoining the photoreceptor cells. The RPE are a critical component of the blood-retinal barrier, and they play essential functional roles for maintenance of retinal homeostasis and for support and health of photoreceptors. Age-dependent, progressive dysfunction and death of RPE cells and the resultant loss of photoreceptors contribute significantly to the development and progression of age-related macular degeneration (AMD) and other retinal degenerative diseases. Several different RPE cell culture models have been developed and utilized extensively as surrogates for cellular and molecular examinations of the RPE, and a large body of knowledge on RPE function in normal and pathological scenarios has been amassed in studies with cultured RPE. Proteomics has been an integral part of research efforts aimed to advance our understanding of RPE cell biology in health and disease. This review focuses on applications of proteomics to in vitro qualitative and quantitative investigation of human RPE cell culture models. The disease context discussed focuses on AMD.

Dissecting microRNA dysregulation in age-related macular degeneration: new targets for eye gene therapy

MicroRNAs (miRNAs) are key regulators of gene expression in humans. Overexpression or depletion of individual miRNAs is associated with human disease. Current knowledge suggests that the retina is influenced by miRNAs and that dysregulation of miRNAs as well as alterations in components of the miRNA biogenesis machinery are involved in retinal diseases, including age-related macular degeneration (AMD). Furthermore, recent studies have indicated that the vitreous has a specific panel of circulating miRNAs and that this panel varies according to the specific pathological stress experienced by the retinal cells. MicroRNA (miRNA) profiling indicates subtype-specific miRNA profiles for late-stage AMD highlighting the importance of proper miRNA regulation in AMD. This review will describe the function of important miRNAs involved in inflammation, oxidative stress and pathological neovascularization, the key molecular mechanisms leading to AMD, and focus on dysregulated miRNAs as potential therapeutic targets in AMD.

MicroRNA-184 promotes differentiation of the retinal pigment epithelium by targeting the AKT2/mTOR signaling pathway

Dedifferentiation of retinal pigment epithelium (RPE) cells is a crucial contributing factor to the pathology of retinal degenerative diseases, including age-related macular degeneration (AMD). Herein, we aim to reveal the roles of microRNAs (miRNAs) in RPE dedifferentiation and seek for potential therapeutic targets. Based on the microarray data, miR-184 was sorted out as the most up-regulated signature along with the differentiation from human induced pluripotent stem cells (hiPSC) to RPE cells, suggesting its potential promotive role in RPE differentiation. In vitro study indicated that miR-184 insufficiency suppressed RPE differentiation, typified by reduction of RPE markers, and promoted cell proliferation and migration. The role of miR-184 in maintaining regular RPE function was further proved in zebrafish studies. We also noticed that miR-184 expression was reduced in the macular RPE-choroid from a donor with RPE dysfunction compared to a healthy control. We next demonstrated that RAC-beta serine/threonine-protein kinase (AKT2) was a direct target for miR-184. MiR-184 promoted RPE differentiation via suppression of AKT2/mammalian target of rapamycin (mTOR) signaling pathway. We also found that AKT2 was up-regulated in macular RPE-choroid of the donor with RPE dysfunction and dry AMD patients. Taken together, our findings suggest that miR-184 insufficiency is involved in the pathogenesis of dry AMD. MiR-184 promotes RPE differentiation via inhibiting the AKT2/mTOR signaling pathway. MiR-184 based supplementary therapeutics and mTOR blocker, like rapamycin, are prospective options for AMD treatment.

Comparative proteomic analysis of human embryonic stem cell-derived and primary human retinal pigment epithelium

Human embryonic stem cell-derived retinal pigment epithelial cells (hESC-RPE) provide an unlimited cell source for retinal cell replacement therapies. Clinical trials using hESC-RPE to treat diseases such as age-related macular degeneration (AMD) are currently underway. Human ESC-RPE cells have been thoroughly characterized at the gene level but their protein expression profile has not been studied at larger scale. In this study, proteomic analysis was used to compare hESC-RPE cells differentiated from two independent hESC lines, to primary human RPE (hRPE) using Isobaric tags for relative quantitation (iTRAQ). 1041 common proteins were present in both hESC-RPE cells and native hRPE with majority of the proteins similarly regulated. The hESC-RPE proteome reflected that of normal hRPE with a large number of metabolic, mitochondrial, cytoskeletal, and transport proteins expressed. No signs of increased stress, apoptosis, immune response, proliferation, or retinal degeneration related changes were noted in hESC-RPE, while important RPE specific proteins involved in key RPE functions such as visual cycle and phagocytosis, could be detected in the hESC-RPE. Overall, the results indicated that the proteome of the hESC-RPE cells closely resembled that of their native counterparts.

Down-regulation of protein kinase C alpha/ezrin signals in light-induced phagocytic crisis of retinal pigment epithelium cells

AIM

To investigate the roles of PKC-α/ezrin signals in phagocytosis crisis of retinal pigment epithelium (RPE) cells in light damage model.

METHODS

Light induced mice RPE injury model was established by continuously irradiating cool white light at different exposure time (0, 4, 8h light intensity: 4.18×10^-6 J/cm²). In vitro, human ARPE-19 cells treated with the doses and intensity (1.57×10^-6 J/cm²) of laser irradiation. Histology analysis was evaluated by hematoxylin and eosin (HE) staining. In vivo RPE phagocytosis was quantified by measuring the accumulation of photoreceptor outer segments in the sub-retinal space. In vitro RPE phagocytosis was assessed by calculating the relative fluorescence intensity of FITC-labeled microspheres in ARPE-19 cells. To further investigate the molecular mechanism, the activation of PKC-α/ezrin signal was evaluated by Western blot in vivo and in vitro.

RESULTS

HE staining revealed that the thickness of outer nuclear layer decreased significantly after 4 and 8h light exposure. By immunostaining with rhodopsin, a significant greater accumulation of photoreceptor outer segment was noticed after light injury. In vitro, light injured RPE cells had less phagocytic activity in a dose dependent manner than that of the normal control (P<0.01). Western blot suggested the activation of PKC-α/ezrin signaling was down-regulated in a dose-dependent manner after light exposure.

CONCLUSION

Our data suggest that light induced phagocytic crisis of RPE cells may result from the down-regulation of PKC-α/ezrin signaling.

Anatomical and Gene Expression Changes in the Retinal Pigmented Epithelium Atrophy 1 (rpea1) Mouse: A Potential Model of Serous Retinal Detachment

Purpose

The purpose of this study was to examine the rpea1 mouse whose retina spontaneously detaches from the underlying RPE as a potential model for studying the cellular effects of serous retinal detachment (SRD).

Methods

Optical coherence tomography (OCT) was performed immediately prior to euthanasia; retinal tissue was subsequently prepared for Western blotting, microarray analysis, immunocytochemistry, and light and electron microscopy (LM, EM).

Results

By postnatal day (P) 30, OCT, LM, and EM revealed the presence of small shallow detachments that increased in number and size over time. By P60 in regions of detachment, there was a dramatic loss of PNA binding around cones in the interphotoreceptor matrix and a concomitant increase in labeling of the outer nuclear layer and rod synaptic terminals. Retinal pigment epithelium wholemounts revealed a patchy loss in immunolabeling for both ezrin and aquaporin 1. Anti-ezrin labeling was lost from small regions of the RPE apical surface underlying detachments at P30. Labeling for tight-junction proteins provided a regular array of profiles outlining the periphery of RPE cells in wild-type tissue, however, this pattern was disrupted in the mutant as early as P30. Microarray analysis revealed a broad range of changes in genes involved in metabolism, signaling, cell polarity, and tight-junction organization.

Conclusions

These data indicate changes in this mutant mouse that may provide clues to the underlying mechanisms of SRD in humans. Importantly, these changes include the production of multiple spontaneous detachments without the presence of a retinal tear or significant degeneration of outer segments, changes in the expression of proteins involved in adhesion and fluid transport, and a disrupted organization of RPE tight junctions that may contribute to the formation of focal detachments.

Genetic variants in microRNAs and their binding sites within gene 3'UTRs associate with susceptibility to age-related macular degeneration

Age-related macular degeneration (AMD), the leading cause of blindness in the elderly, is a complex disease that results from multiple genetic and environmental factors. MicroRNAs (miRNAs) are small noncoding RNAs that post-transcriptionally regulate target mRNAs and are frequently implicated in human diseases. Here, we investigated the association of genetic variants in miRNAs and miRNA-binding sites within gene 3'-untranslated regions (3'UTRs) with AMD using data from the largest AMD genome-wide association study. First, we identified three variants in miRNAs significantly associated with AMD. These include rs2168518:G>A in the miR-4513 seed sequence, rs41292412:C>T in pre-miR-122/miR-3591, and rs4351242:C>T in the terminal-loop of pre-miR-3135b. We demonstrated that these variants reduce expression levels of the mature miRNAs in vitro and pointed the target genes that may mediate downstream effects of these miRNAs in AMD. Second, we identified 54 variants (in 31 genes) in miRNA-binding sites associated with AMD. Based on stringent prioritization criteria, we highlighted the variants that are more likely to have an impact on the miRNA-target interactions. Further, we selected rs4151672:C>T within the CFB 3'UTR and experimentally showed that while miR-210-5p downregulates expression of CFB, the variant decreases miR-210-5p-mediated repression of CFB. Together, our findings support the notion that miRNAs may play a role in AMD.

Multimodal Regulation Orchestrates Normal and Complex Disease States in the Retina

Regulation of biological processes occurs through complex, synergistic mechanisms. In this study, we discovered the synergistic orchestration of multiple mechanisms regulating the normal and diseased state (age related macular degeneration, AMD) in the retina. We uncovered gene networks with overlapping feedback loops that are modulated by nuclear hormone receptors (NHR), miRNAs, and epigenetic factors. We utilized a comprehensive filtering and pathway analysis strategy comparing miRNA and microarray data between three mouse models and human donor eyes (normal and AMD). The mouse models lack key NHRS (Nr2e3, RORA) or epigenetic (Ezh2) factors. Fifty-four total miRNAs were differentially expressed, potentially targeting over 150 genes in 18 major representative networks including angiogenesis, metabolism, and immunity. We identified sixty-eight genes and 5 miRNAS directly regulated by NR2E3 and/or RORA. After a comprehensive analysis, we discovered multimodal regulation by miRNA, NHRs, and epigenetic factors of three miRNAs (miR-466, miR1187, and miR-710) and two genes (Ell2 and Entpd1) that are also associated with AMD. These studies provide insight into the complex, dynamic modulation of gene networks as well as their impact on human disease, and provide novel data for the development of innovative and more effective therapeutics.

CD164 regulates proliferation and apoptosis by targeting PTEN in human glioma

Cluster of differentiation 164 (CD164), a sialomucin, has been demonstrated to be involved in the regulation of proliferation, apoptosis, adhesion and differentiation in multiple cancers. CD164 is regarded to be a potential promotor of tumor growth. However, the involvement of CD164 in human glioma proliferation and apoptosis remains unknown. The aim of the present study was to investigate the expression and oncogenic function of CD164 in normal human astrocytes (NHA) and glioma cells in vitro and in vivo. The results of the present study demonstrated that CD164 mRNA and protein levels were significantly increased in human glioma cell lines and tissue samples. CD164 overexpression promoted the proliferation of NHA in vitro, and its tumorigenic effect was confirmed in a murine xenograft model. Knockdown of CD164 inhibited cell proliferation and promoted apoptosis of the U87 human glioma cell line in vitro and in vivo. In addition, knockdown of CD164 was demonstrated to upregulate the Bax/Bcl2 ratio and phosphatase and tensin homolog (PTEN) expression, reduce protein kinase B (AKT) phosphorylation and promote the expression of p53 in U87 cells. The results suggest that CD164 expression may have affected the proliferation and apoptosis of human glioma cells via the PTEN/phosphoinositide 3-kinase/AKT pathway, and may therefore present a potential target for the diagnosis and treatment of glioma.

An Eye on Age-Related Macular Degeneration: The Role of MicroRNAs in Disease Pathology

Age-related macular degeneration (AMD) is the primary cause of blindness in developed countries, and is the third leading cause worldwide. Emerging evidence suggests that beside environmental and genetic factors, epigenetic mechanisms, such as microRNA (miRNA) regulation of gene expression, are relevant to AMD providing an exciting new avenue for research and therapy. MiRNAs are short, non-coding RNAs thought to be imperative for coping with cellular stress. Numerous studies have analyzed miRNA dysregulation in AMD patients, although with varying outcomes. Four studies which profiled dysregulated circulating miRNAs in AMD yielded unique sets, and there is only minimal overlap in ocular miRNA profiling of AMD. Mouse models of AMD, including oxygen-induced retinopathy and laser-induced choroidal neovascularization, showed similarities to some extent with miRNA patterns in AMD. For example, miR-146a is an extensively researched miRNA thought to modulate inflammation, and was found to be upregulated in AMD mice and cellular systems, but also in human AMD retinae and vitreous humor. Similarly, mir-17, miR-125b and miR-155 were dysregulated in multiple AMD mouse models as well as in human AMD plasma or retinae. These miRNAs are thought to regulate angiogenesis, apoptosis, phagocytosis, and inflammation. A promising avenue of research is the modulation of such miRNAs, as the phenotype of AMD mice could be ameliorated with antagomirs or miRNA-mimic treatment. However, before meaningful strides can be made to develop miRNAs as a diagnostic or therapeutic tool, reproducible miRNA profiles need to be established for the various clinical outcomes of AMD.

MicroRNA-182 Suppresses HGF/SF-Induced Increases in Retinal Pigment Epithelial Cell Proliferation and Migration through Targeting c-Met

As increases in hepatocyte growth factor/scatter factor (HGF/SF) induce retinal pigment epithelial (RPE) migration and proliferation into the vitreous cavity and contribute to proliferative vitreoretinopathy (PVR) development, we determined if changes in miR-182 expression affect such behavioral changes. We found that miR-182 expression was less in PVR clinical samples than in primary RPE cells whereas c-Met was upregulated. Ectopic miR-182 inhibited RPE cell proliferation, cell cycle, and migration. Bioinformatic analysis identified c-Met as a miR-182 target, which was confirmed with the luciferase reporter assay. Transfection of miR-182 into RPE cells induced c-Met downregulation, which led to reduced cell proliferation and migration through declines in p-Akt formation. MiR-182 downregulation along with c-Met upregulation in PVR tissues suggest that these two opposing effects play important roles in PVR development. As ectopic miR-182 expression suppressed RPE cell proliferation and migration, strategies to selectively upregulate miR-182 expression in a clinical setting may provide a novel option to treat this disease.