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

miRNA‑124 regulates palmitic acid‑induced epithelial‑mesenchymal transition and cell migration in human retinal pigment epithelial cells by targeting LIN7C

The present study revealed that palmitic acid (PA) treatment induced epithelial-mesenchymal transition (EMT) of retinal pigment epithelial (RPE) cells, which are involved in the progression of proliferative vitreoretinopathy (PVR). ARPE-19 cells were treated with PA followed by miRNA screening and EMT marker detection using qRT-PCR. Then, miR-124 mimic or inhibitor was transfected into ARPE-19 cells to explore the role of miR-124 on the EMT of ARPE-19 cells using transwell assay. The underlying mechanism of miRNA were predicted by bioinformatics method and confirmed by luciferase activity reporter assay. Furthermore, gain-of-function strategy was also used to explore the role of LIN7C in the EMT of ARPE-19 cells. The expression of miRNA or mRNA expression was determined by qRT-PCR and the protein expression was determined using western blot assay. The result presented that PA reduced the expression of E-cadherin/ZO-1 whilst increasing the expression of fibronectin/α-SMA. In addition, PA treatment enhanced the expression of microRNA (miR)-124 in ARPE-19 cells. Overexpression of miR-124 enhanced PA-induced upregulation of E-cadherin and ZO-1 expression and downregulation of fibronectin and α-SMA. Moreover, miR-124 mimic also enhanced the migration of ARPE-19 cells induced by PA treatment. Inversely, miR-124 inhibitor presented opposite effect on PA-induced EMT and cell migration in ARPE-19 cells. Luciferase activity reporter assay confirmed that Lin-7 homolog C (LIN7C) was a direct target of miR-124 in ARPE-19 cells. Overexpression of LIN7C was found to suppress the migration ability and expression of fibronectin and α-SMA, while increasing expression of E-cadherin and ZO-1; miR-124 mimic abrogated the inhibitive effect of LIN7C on the EMT of ARPE-19 cells and PA further enhanced this abolishment. Collectively, these findings suggest that miR-124/LIN7C can modulate EMT and cell migration in RPE cells, which may have therapeutic implications in the management of PVR 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.

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.

Polarity and epithelial-mesenchymal transition of retinal pigment epithelial cells in proliferative vitreoretinopathy

Under physiological conditions, retinal pigment epithelium (RPE) is a cellular monolayer composed of mitotically quiescent cells. Tight junctions and adherens junctions maintain the polarity of RPE cells, and are required for cellular functions. In proliferative vitreoretinopathy (PVR), upon retinal tear, RPE cells lose cell-cell contact, undergo epithelial-mesenchymal transition (EMT), and ultimately transform into myofibroblasts, leading to the formation of fibrocellular membranes on both surfaces of the detached retina and on the posterior hyaloids, which causes tractional retinal detachment. In PVR, RPE cells are crucial contributors, and multiple signaling pathways, including the SMAD-dependent pathway, Rho pathway, MAPK pathways, Jagged/Notch pathway, and the Wnt/β-catenin pathway are activated. These pathways mediate the EMT of RPE cells, which play a key role in the pathogenesis of PVR. This review summarizes the current body of knowledge on the polarized phenotype of RPE, the role of cell-cell contact, and the molecular mechanisms underlying the RPE EMT in PVR, emphasizing key insights into potential approaches to prevent PVR.

MicroRNAs in the Vitreous Humor of Patients with Retinal Detachment and a Different Grading of Proliferative Vitreoretinopathy: A Pilot Study

Purpose

Although the expression of microRNAs (miRNAs) in retinal pigment epithelial (RPE) cells undergoing epithelial-mesenchymal transition (EMT) is involved in the pathogenesis of proliferative vitreoretinopathy (PVR), its expression in the vitreous of patients with primary retinal detachment (RD) and different PVR grading has not yet been investigated. We assessed the expression of miRNAs in the vitreous humor (VH) of patients diagnosed with RD and different grading of PVR.

Methods

The VH was extracted from the core of the vitreous chamber in patients who had undergone standard vitrectomy for primary RD. RNA was extracted and TaqMan Low-Density Arrays (TLDAs) were used for miRNA profiling that was performed by single TaqMan assays. A gene ontology (GO) analysis was performed on the differentially expressed miRNAs.

Results

A total of 15 eyes with RD, 3 eyes for each grade of PVR (A, B, C, and D) and 3 from unaffected individuals, were enrolled in this prospective comparative study. Twenty miRNAs were altered in the comparison among pathological groups. Interestingly, the expression of miR-143-3p, miR-224-5p, miR-361-5p, miR-452-5p, miR-486-3p, and miR-891a-5p increased with the worsening of PVR grading. We also identified 34 miRNAs showing differential expression in PVR compared to control vitreous samples. GO analysis showed that the deregulated miRNAs participate in processes previously associated with PVR pathogenesis.

Conclusions

The present pilot study suggested that dysregulated vitreal miRNAs may be considered as a biomarker of PVR and associated with the PVR-related complications in patients with RD.

Translational Relevance

The correlation between vitreal miRNAs and the pathological phenotypes are essential to identify the novel miRNA-based mechanisms underlying the PVR disease that would improve the diagnosis and treatment of the condition.

Beta-adrenergic agonist protects retinal pigment epithelium against hydroxycholoroquine toxicity via cAMP-PKA signal pathway

AIM

To test our hypothesis that activation of protein kinase A (PKA) signal pathway by β-adrenergic agonist plays an important role in the protecting of cultured retinal pigment epithelial (RPE) cells against the hydroxychloroquine (HCQ) toxicity.

METHODS

Cultured human RPE cells were treated with 1) HCQ, 2) HCQ with salbutamol (a β2-adrenergic receptor agonist), and 3) HCQ with salbutamol and a PKA inhibitor, and compared these to 4) untreated cells (controls). After treated for 24h, cell vacuolation, cells viability, PKA and PKA kinase activity levels were determined by the measurement of the size of vacuoles using Image J software, the cell counting with a dye-exclusion testing, Western blot and PKA kinase detection, respectively.

RESULTS

Cell vacuolation and cell death of cultured RPE cells were significantly increased by the treatment of HCQ. Salbutamol significantly elevated PKA and PKA activity levels and this was associated with the inhibition of the vacuolation and cell death. The PKA inhibitor significantly decreased the PKA levels and eliminated the protective effects of salbutamol on HCQ-treated RPE cells.

CONCLUSION

The PKA pathway plays an important role in the protective effects of β2-adrenergic agonist on the RPE cells against HCQ toxicity. These findings reveal a novel potential strategy against HCQ retinopathy by treatment with PKA activating medications.

Protein Kinase A Inhibitor H89 Attenuates Experimental Proliferative Vitreoretinopathy

Purpose

This study aimed to explore the role of the protein kinase A (PKA) pathway in proliferative vitreoretinopathy (PVR) and the effect of the PKA inhibitor H89 on experimental PVR.

Methods

Epiretinal membranes (ERMs) were acquired from PVR patients and analyzed by frozen-section immunofluorescence. An in vivo model was developed by intravitreal injecting rat eyes with ARPE-19 cells and platelet-rich plasma, and changes in eye structures and vision function were observed. An in vitro epithelial-mesenchymal transition (EMT) cell model was established by stimulating ARPE-19 cells with transforming growth factor (TGF)-β. Alterations in EMT-related genes and cell function were detected. Mechanistically, PKA activation and activity were explored to assess the relationship between TGF-β1 stimulation and the PKA pathway. The effect of H89 on the TGF-β-Smad2/3 pathway was detected. RNA sequencing was used to analyze gene expression profile changes after H89 treatment.

Results

PKA was activated in human PVR membranes. In vivo, H89 treatment protected against structural changes in the retina and prevented decreases in electroretinogram b-wave amplitudes. In vitro, H89 treatment inhibited EMT-related gene alterations and partially reversed the functions of the cells. TGF-β-induced PKA activation was blocked by H89 pretreatment. H89 did not affect the phosphorylation or nuclear translocation of regulatory Smad2/3 but increased the expression of inhibitory Smad6.

Conclusions

PKA pathway activation is involved in PVR pathogenesis, and the PKA inhibitor H89 can effectively inhibit PVR, both in vivo and in vitro. Furthermore, the protective effect of H89 is related to an increase in inhibitory Smad6.

Oxidative stress-induced angiogenesis is mediated by miR-205-5p

miR‐205‐5p is known to be involved in VEGF‐related angiogenesis and seems to regulate associated cell signalling pathways, such as cell migration, proliferation and apoptosis. Therefore, several studies have focused on the potential role of miR‐205‐5p as an anti‐angiogenic factor. Vascular proliferation is observed in diabetic retinopathy and the ‘wet’ form of age‐related macular degeneration. Today, the most common treatments against these eye‐related diseases are anti‐VEGF therapies. In addition, both AMD and DR are typically associated with oxidative stress; hence, the use of antioxidant agents is accepted as a co‐adjuvant therapy for these patients. According to previous data, ARPE‐19 cells release pro‐angiogenic factors when exposed to oxidative insult, leading to angiogenesis. Matching these data, results reported here, indicate that miR‐205‐5p is modulated by oxidative stress and regulates VEGFA‐angiogenesis. Hence, miR‐205‐5p is proposed as a candidate against eye‐related proliferative diseases.

miR-194 suppresses epithelial-mesenchymal transition of retinal pigment epithelial cells by directly targeting ZEB1

Background

Epithelial-mesenchymal transition (EMT) of the retinal pigment epithelial (RPE) cells is a critical step in the pathogenesis of proliferative vitreoretinopathy (PVR). Some microRNAs (miRNAs) participate in regulating RPE cell EMT as post-transcriptional regulators. However, the function of miR-194 in RPE cell EMT remains elusive. Here, the role of miR-194 in PVR was investigated.

Methods

Retinal layers were obtained using laser capture microdissection (LCM). Gene expression at the mRNA and protein level in the tissues and cells was examined using quantitative reverse transcription (RT)-polymerase chain reaction and Western blotting, respectively. The related protein expression was observed by immunostaining. The effect of miR-194 on RPE cell EMT was examined by gel contraction, wound healing, and cell migration assays. RNAseq was performed in ARPE-19 with transfection of pSuper-scramble and pSuper-miR-194. The target gene of miR-194 was identified and confirmed via bioinformatics analysis and dual-luciferase reporter assay. ARPE-19 (adult retinal pigment epithelium-19) cells were treated with transforming growth factor (TGF)-β1 in the same fashion as the in vitro RPE cell EMT model. A PVR rat model was prepared by intravitreous injection of ARPE-19 cells with plasma-rich platelets.

Results

miR-194 was preferentially expressed in the RPE cell layer compared with the outer nuclear layer (ONL), inner nuclear layer (INL), and ganglion cell layer in rat retina. RNAseq analysis indicated that miR-194 overexpression was involved in RPE cell processes, including phagocytosis, ECM-receptor interaction, cell adhesion molecules, and focal adhesion. miR-194 overexpression significantly inhibited the TGF-β1-induced EMT phenotype of RPE cells in vitro. Zinc finger E-box binding homeobox 1 (ZEB1), a key transcription factor in EMT, was confirmed as the direct functional target of miR-194. Knockdown of ZEB1 attenuated TGF-β1-induced α-smooth muscle actin expression in ARPE-19 cells, and overexpression of miR-194 could significantly reduce the expression of some genes which were up-regulated by ZEB1. Exogenous miR-194 administration in vivo effectively suppressed PVR in the rat model, both functionally and structurally.

Conclusions

Our findings demonstrate for the first time that miR-194 suppresses RPE cell EMT by functionally targeting ZEB1. The clinical application of miR-194 in patients with PVR merits further investigation.

Diminished LINC00173 expression induced miR-182-5p accumulation promotes cell proliferation, migration and apoptosis inhibition via AGER/NF-κB pathway in non-small-cell lung cancer

Non-small cell lung cancer (NSCLC) is one of the most common malignant tumors in the world, and non-coding RNA (ncRNA) has recently been widely reported to participate in the development of NSCLC. Some ncRNAs, especially microRNAs (miRNAs), are widely reported as tumor drug targets due to their short transcript length and easiness for processing into small molecule compounds. Therefore, exploring the potential roles of specific miRNAs in NSCLC may provide a better understanding of the molecular etiology. In this study, we downloaded the large-scale RNA-seq data from the Cancer Genome Atlas (TCGA) database, and identified 211 differentially expressed miRNAs (121 up-regulated and 90 down-regulated) in NSCLC. Similar to the TCGA database, miR-182-5p was significantly up-regulated in the serum and tissue samples of NSCLC patients. Clinicopathological parameters revealed the positive correlation between miR-182-5p expression and advanced TNM stage. Functional tests showed miR-182-5p overexpression promoted cell proliferation, migration and apoptosis inhibition, while miR-182-5p knockdown weakened the above phenotypes. Besides, advanced glycosylation end-product specific receptor (AGER) was identified as a direct downstream target of miR-182-5p. Alteration of AGER expression or NF-κB inhibitor could partially counteract the bioactive roles induced by miR-182-5p overexpression or knockdown. Further study disclosed down-regulated LINC00173 was negatively corrected with miR-182-5p in NSCLC tissues. LINC00173 could regulate miR-182-5p expression and reversed functional behaviors mediated by miR-182-5p/AGER/NF-κB axis. Taken together, miR-182-5p mediated the malignant phenotypes through NF-κB pathway via targeting AGER, and LINC00173 acted as a potential negative regulator of miR-182-5p in NSCLC cells.

Differential expression of connective tissue growth factor and hepatocyte growth factor in the vitreous of patients with high myopia versus vitreomacular interface disease

Background

To determine the levels of connective tissue growth factor (CTGF) and hepatocyte growth factor (HGF) in the vitreous of patients with high myopia, in comparison with those with a vitreomacular interface disease (VMID).

Methods

Patients with either high myopia (high myopia group) or a VMID (VMID group) were included in this study. Each of the two groups were further subdivided into two subgroups: group A (high myopia with macular hole), group B (high myopia with macular retinoschisis), group C (idiopathic macular hole), and group D (idiopathic epiretinal membrane). Vitreal specimens were collected during vitrectomy, and enzyme-linked immunosorbent assay was used to quantitatively measure the CTGF and HGF levels in the vitreous.

Results

The average axial length was markedly longer in the high myopia group than in the VMID group. The vitreal CTGF level was significantly higher in the high myopia group than in the VMID group. Subgroup analysis revealed significantly higher vitreal CTGF in group A than in the other three subgroups. The vitreal HGF level was not significantly different between the high myopia and VMID groups, but was significantly higher in group D than in group C in the subgroup analysis. Correlation analysis showed that the vitreal CTGF level was positively correlated with the axial length.

Conclusions

The vitreal CTGF level is elevated in highly myopic eyes and may be related to the pathogenesis of high myopia, whereas increased expression of HGF may be involved in the development of idiopathic epiretinal membrane.

The effects of microRNAs in activating neovascularization pathways in diabetic retinopathy

Diabetic retinopathy (DR) is one of the major complications of diabetes mellitus that causes diabetic macular edema and visual loss. DR is categorized, based on the presence of vascular lesions and neovascularization, into non-proliferative and proliferative DR. Vascular changes in DR correlate with the cellular damage and pathological changes in the capillaries of blood-retinal barrier. Several cytokines have been involved in inducing neovascularization. These cytokines activate different signaling pathways which are mainly responsible for the complications of DR. Recently; microRNAs (miRNAs) have been introduced as the key factors in the regulation of the cytokine expression which plays a critical role in neovascularization of retinal cells. Some studies have demonstrated that changing levels of miRNAs have essential role in the pathophysiology of vascular changes in patients with DR. The aim of this study is to identify the effects of miRNAs in the pathogenesis of DR via activating neovascularization pathways.

Hepatocyte growth factor promotes the proliferation of human embryonic stem cell derived retinal pigment epithelial cells

Research that pertains to the molecular mechanisms involved in retinal pigment epithelial (RPE) development can significantly contribute to cell therapy studies. The effects of periocular mesenchymal cells on the expansion of RPE cells remain elusive. We have examined the possible proliferative role of hepatocyte growth factor (HGF) as a mesenchymal cell secretory factor against human embryonic stem cell derived RPE (hESC-RPE). We found that the conditioned medium of human mesenchymal stem cells from apical papilla and/or exogenous HGF promoted proliferation of the hESC-RPE cells as single cells and cell sheets, in addition to rabbit RPE sheets in vitro. Blockage of HGF signaling by HGF receptor inhibitor, PHA-665752, inhibited proliferation of hESC-RPE cells. However, differentiation of hESCs and human-induced pluripotent stem cells to a rostral fate and eye-field specification was unaffected by HGF. Our in vivo analysis showed HGF expression in periocular mesenchymal cells after optic cup formation in chicken embryos. Administration of HGF receptor inhibitor at this developmental stage in chicken embryos led to reduced eye size and disorganization of the RPE sheet. These findings suggested that HGF administration could be beneficial for obtaining higher numbers of hESC-RPE cells in human preclinical and clinical trials.

Analysis of non‑alcoholic fatty liver disease microRNA expression spectra in rat liver tissues

The prevalence of non-alcoholic fatty liver disease (NAFLD) has been increasing in recent years. Previous studies have suggested that micro (mi)RNAs may be involved in the pathogenesis of NAFLD. To investigate the role of miRNAs in rat NAFLD, a total of 16 male Sprague Dawley rats were randomly divided into a control group and a model group. Rats in the control group were fed a normal diet for 12 weeks, whereas the rats in the model group were fed a high‑fat and high‑sugar diet for 12 weeks. Following this, the animals were sacrificed and liver tissues were rapidly removed to investigate the severity of NAFLD. Blood samples were collected to investigate liver function, in addition to total cholesterol, total triglyceride and fasting plasma glucose levels. Total RNA from three fresh liver samples per experimental group was extracted for subsequent miRNA gene chip analysis using GeneChip miRNA 4.0 to investigate differentially expressed miRNAs, and miRNA expression was further verified via reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR). Compared with the control group, the results revealed that there were 10 differentially expressed miRNAs in the model group, five of which were overexpressed and five of which were underexpressed compared with the control group. The results of the RT‑qPCR analysis revealed that miR‑182, miR‑29b‑3p and miR‑741‑3p were significantly overexpressed in the model group compared with the control group, which was largely consistent with the results of the microarray analysis. The results suggested that the differentially expressed microRNAs demonstrated in the present study may be involved in the pathogenesis of NAFLD; however, the mechanism underlying the differential expression of miRNAs in NAFLD requires further investigation.

Akt Protein Kinase, miR-200/miR-182 Expression and Epithelial-Mesenchymal Transition Proteins in Hibernating Ground Squirrels

Hibernating 13-lined ground squirrels (Ictidomys tridecemlineatus; TLGS) rank among the most brain hypoperfusion-tolerant mammals known. Herein we provide some evidence of cycling between an epithelial phenotype and a hybrid epithelial/mesenchymal (E/M) phenotype (partial EMT) within the brains of TLGS during each bout of hibernation torpor. During hibernation torpor, expression of the epithelial marker E-cadherin (E-CDH) was reduced, while expression of the well-known mesenchymal markers vimentin and Sox2 were increased. P-cadherin (P-CDH), which has recently been proposed as a marker of intermediate/partial EMT, also increased during torpor, suggesting that a partial EMT may be taking place during hibernation torpor. Members of the miR-200 family and miR-182 cluster and Akt isoforms (Akt1, Akt2), well-known EMT regulators, were also differentially regulated in the TLGS brain during hibernation bouts. Using SHSY5Y cells, we also demonstrate that the Akt1/Akt2 ratio determined the expression levels of miR-200/miR-182 miRNA family members, and that these miRNAs controlled the expression of EMT-related proteins. Accordingly, we propose that such cell state transitions (EMT/MET) may be one of the mechanisms underlying the extraordinary ischemic tolerance of the TLGS brain during hibernation bouts; hibernator brain cells appear to enter reversible states that confer the stress survival characteristics of cancer cells without the risk of neoplastic transformation.

Biological Involvement of MicroRNAs in Proliferative Vitreoretinopathy

Even with a high surgical success rate for retinal detachment and proliferative vitreoretinopathy (PVR) supported by the robust improvement in vitrectomy surgery and its related devices, certain questions still remain for the pathogenesis and treatment of PVR. One of the important biological events in PVR is epithelial–mesenchymal transition (EMT) of the retinal pigment epithelial (RPE) cells. MicroRNAs are noncoding, small, single-strand RNAs that posttranscriptionally regulate gene expression and have essential roles in homeostasis and pathogenesis in many diseases. Recently, microRNAs also had a critical role in EMT in many tissues and cells. One main purpose of this brief review is to describe the knowledge obtained from microRNA research, especially concerning vitreoretinal diseases. In addition, the potential role of microRNAs in prevention of PVR by regulating EMT in RPE cells is described. Understanding microRNA involvement in PVR could be helpful for developing new biological markers or therapeutic targets and reducing the rate of visual disability due to PVR.