Correlation between microRNA-34a levels and lens opacity severity in age-related cataracts

Plasma miR-19b, miR-34a, and miR-146a expression in patients with type 2 diabetes mellitus and cataract: A pilot study

Cataract is among the most common ocular complications in diabetes mellitus (DM). While microRNA (miRNA) dysregulations in DM have been previously reported, consensus is still lacking concerning miRNA expression in cataract. Furthermore, the miRNA profile in diabetic cataract patients remains largely unexplored, and data on plasma expression levels are limited. Our study aimed to assess the plasma levels of three distinct miRNA species (hsa-miR-19b, hsa-miR-34a, and hsa-miR-146a) implicated in the development of cataract and/or DM.We investigated the circulating miRNA expression in DM patients diagnosed with cataract, compared to a non-DM cataract group. We employed qRT-PCR for relative quantification experiments and subsequently conducted a correlation analysis between miRNA expression levels and clinical characteristics. Our findings reveal that hsa-miR-34a and hsa-miR-146a are differentially expressed in the two cohorts. However, no significant correlation was observed between the clinical variables and miRNA levels. In summary, our results suggest a potential role for hsa-miR-34a and hsa-miR-146a in the biology of diabetic cataract.

miR-26 Deficiency Causes Alterations in Lens Transcriptome and Results in Adult-Onset Cataract

Purpose

Despite strong evidence demonstrating that normal lens development requires regulation governed by microRNAs (miRNAs), the functional role of specific miRNAs in mammalian lens development remains largely unexplored.

Methods

A comprehensive analysis of miRNA transcripts in the newborn mouse lens, exploring both differential expression between lens epithelial cells and lens fiber cells and overall miRNA abundance, was conducted by miRNA sequencing. Mouse lenses lacking each of three abundantly expressed lens miRNAs (miR-184, miR-26, and miR-1) were analyzed to explore the role of these miRNAs in lens development.

Results

Mice lacking all three copies of miR-26 (miR-26TKO) developed postnatal cataracts as early as 4 to 6 weeks of age. RNA sequencing analysis of neonatal lenses from miR-26TKO mice exhibited abnormal reduced expression of a cohort of genes found to be lens enriched and linked to cataract (e.g., Foxe3, Hsf4, Mip, Tdrd7, and numerous crystallin genes) and abnormal elevated expression of genes related to neural development (Lhx3, Neurod4, Shisa7, Elavl3), inflammation (Ccr1, Tnfrsf12a, Csf2ra), the complement pathway, and epithelial to mesenchymal transition (Tnfrsf1a, Ccl7, Stat3, Cntfr).

Conclusions

miR-1, miR-184, and miR-26 are each dispensable for normal embryonic lens development. However, loss of miR-26 causes lens transcriptome changes and drives cataract formation.

miR-26 deficiency causes alterations in lens transcriptome and results in adult-onset cataract

Purpose

Despite strong evidence demonstrating that normal lens development requires regulation governed by miRNAs, the functional role of specific miRNAs in mammalian lens development remains largely unexplored.

Methods

A comprehensive analysis of miRNA transcripts in the newborn mouse lens, exploring both differential expression between lens epithelial cells and lens fiber cells and overall miRNA abundance was conducted by miRNA-seq. Mouse lenses lacking each of three abundantly expressed lens miRNAs: miR-184, miR-26 and miR-1 were analyzed to explore the role of these miRNAs in lens development.

Results

Mice lacking all three copies of miR-26 (miR-26TKO) developed postnatal cataracts as early as 4-6 weeks of age. RNA-seq analysis of neonatal lenses from miR-26TKO mice exhibited abnormal reduced expression of a cohort of genes found to be lens-enriched and linked to cataract (e.g. Foxe3, Hsf4, Mip, Tdrd7, and numerous crystallin genes), and abnormal elevated expression of genes related to neural development (Lhx3, Neurod4, Shisa7, Elavl3 ), inflammation (Ccr1, Tnfrsf12a, Csf2ra), the complement pathway, and epithelial to mesenchymal transition (Tnfrsf1a, Ccl7, Stat3, Cntfr).

Conclusion

miR-1, miR-184 and miR-26 are each dispensable for normal embryonic lens development. However, loss of miR-26 causes lens transcriptome changes and drives cataract formation.

Evaluation of expression pattern of cellular miRNAs (let-7b, miR-29a, miR-126, miR-34a, miR-181a-5p) and IL-6, TNF-α, and TGF-β in patients with pseudoexfoliation syndrome

Pseudoexfoliation syndrome (PEX) is a critical clinical and biological extracellular matrix systemic disorder. Despite the unknown nature of PEX etiopathogenesis, it is proven to be associated with various genes and factors. The present research focused on analyzing the expression of miR and inflammatory cytokines in PEX. Serum and aqueous humor (AH) were collected prior to cataract surgery or trabeculectomy from 99 participants (64 with PEX glaucoma, and 35 controls). Real-time PCR was used for assessing the expression pattern of some miRNAs namely let-7b, miR-29a, miR-126, miR-34a, and miR-181a-5p. ELISA was carried out to explore the transcription of some inflammatory cytokines such as TGF-β, TNF-α, and IL-6. The indication of our results was a significant enhancement in the expression of let-7, miR-34a, and miR-181a-5p in PEX in contrast to the control group. Notwithstanding a significant suppression in miR-29a, and miR-126 expression levels in PEX in contrast to the control group. Analysis of ROC curve revealed that miR-29a and miR-34a are able to act as useful markers in order to discriminate the PEX group from the PEX negative subjects which were determined as the control group. According to the results obtained, the mean levels of TGF-β, TNF-α, and IL-6 upregulated among PEX subjects in contrast to control samples. In conclusion, our findings indicated that the selected cytokines alongside the selected miRNAs could be introduced as a biomarker panel in the diagnosis of PEX.

MIR34A modulates lens epithelial cell apoptosis and cataract development via the HK1/caspase 3 signaling pathway

Cataracts are the leading cause of blindness in the world. Age is a major risk factor for cataracts, and with increasing aging, the burden of cataracts will grow, but the exact details of cataractogenesis remain unclear. A recent study showed that microRNA-34a (MIR34A) is involved in the development of cataracts, but the underlying pathogenesis remains obscure. Here, our results of microRNA target prediction showed that hexokinase 1 (HK1) is one of the genes targeted by MIR34A. Based on this finding, we focused on the function of MIR34A and HK1 in the progress of cataracts, whereby the human lens epithelial cell line SRA01/04 and mouse lens were treated with MIR34A mimics and HK1 siRNA. We found that HK1 mRNA is a direct target of MIR34A, whereby the high expression of MIR34A in the cataract lens suppresses the expression of HK1. In vitro, the upregulation of MIR34A together with the downregulation of HK1 inhibits the proliferation, induces the apoptosis of SRA01/04 cells, and accelerates the opacification of mouse lenses via the HK1/caspase 3 signaling pathway. In summary, our study demonstrates that MIR34A modulates lens epithelial cell (LEC) apoptosis and cataract development through the HK1/caspase 3 signaling pathway.

CircMED12L Protects Against Hydrogen Peroxide-induced Apoptotic and Oxidative Injury in Human Lens Epithelial Cells by miR-34a-5p/ALCAM axis

PURPOSE

Cataract is the leading cause of visual impairment and reversible blindness. Despite advances in surgical removal of cataracts, cataract continues to be a leading public-health issue due to the complications after surgery. Circular RNAs (circRNAs) have been showed to be implicated in the pathophysiology of age-related cataract (ARC). Herein, this work elucidated the role and mechanism of circMED12L in the process of ARC.

METHODS

Human lens epithelial cells (HLECs) were exposed to hydrogen peroxide (H₂O₂) in experimental groups. Levels of genes and proteins were measured by qRT-PCR and western blotting. Cell growth was evaluated by Cell Counting Kit-8 (CCK-8) assay and flow cytometry, respectively. The oxidative stress was assessed by detecting the activity of malondialdehyde, catalase, and superoxide dismutase. The interaction between miR-34a-5p and circMED12L or ALCAM (activated leukocyte cell adhesion molecule) was validated using dual-luciferase reporter and RNA immunoprecipitation assays.

RESULTS

CircMED12L expression was lower in the lens epithelium of ARC patients and H₂O₂-induced HLECs compared with the normal individuals and untreated cells. Functionally, forced expression of circMED12L could alleviate H₂O₂-induced viability inhibition, as well as apoptotic and oxidative injury in HLECs. Mechanistically, circMED12L/miR-34a-5p/ALCAM constituted a feedback loop in HLECs. MiR-34a-5p was increased, while ALCAM was decreased in ARC patients and H₂O₂-induced HLECs. High expression of miR-34a-5p reversed the protective effects of circMED12L on HLECs under H₂O₂ treatment. Besides, inhibition of miR-34a-5p could repress H₂O₂-induced apoptotic and oxidative injury in HLECs, which were abolished by subsequent ALCAM knockdown.

CONCLUSION

Overexpression of circMED12L could protect against H₂O₂-induced apoptosis and oxidative stress in HLECs by miR-34a-5p/ALCAM axis.

Noncoding RNAs in cataract formation: star molecules emerge in an endless stream

For decades, research on the pathological mechanism of cataracts has usually focused on the abnormal protein changes caused by a series of risk factors. However, an entire class of molecules, termed non-coding RNA (ncRNA), was discovered in recent years and proven to be heavily involved in cataract formation. Recent studies have recognized the key regulatory roles of ncRNAs in cataracts by shaping cellular activities such as proliferation, apoptosis, migration and epithelial-mesenchymal transition (EMT). This review summarizes our current insight into the biogenesis, properties and functions of ncRNAs and then discusses the development of research on ncRNAs in cataracts. Considering the significant role of ncRNA in cataract formation, research on novel associated regulatory mechanisms is urgently needed, and the development of therapeutic alternatives for the treatment of cataracts seems promising.

Circulating Vitreous microRNA as Possible Biomarker in High Myopic Eyes with Macular Hole

High myopia is a major cause of irreversible visual impairment globally. In the present study, we investigated the microRNA (miRNA) profile in the vitreous of macular hole (MH) and high myopic MH. We performed miRNA analysis using TaqMan® Low Density Arrays (Thermo Fisher Scientific, Waltham, MA, USA) to investigate the circulating vitreous miRNA profile from patients with MH (axial length < 26.5 mm, n = 11) and high myopic MH (axial length ≥ 26.5 mm, n = 11) who underwent pars plana vitrectomy. The vitreous inflammatory cytokine signature was examined in high myopic MH eyes using a multiplex assay. A miRNA-Array analysis revealed that let-7c was significantly up-regulated and miR-200a was significantly down-regulated in high myopic MH eyes compared to those in MH eyes. The bioinformatics analysis for up-regulated miRNA targeted gene identified 23 pathways including mitogen-activated protein kinase (MAPK) and several inflammatory signaling pathways, whereas the bioinformatics analysis for down-regulated miRNA targeted genes showed 32 enriched pathways including phosphoinositide 3-kinase/protein kinase B (PI3K/AKT). The levels of inflammatory cytokines including IP-10, IFN-γ, and MCP-1 were significantly higher in the vitreous of high myopic MH eyes. These results suggest that specific miRNAs expressed in the vitreous may be associated with the pathological condition of high myopic MH and the above mentioned miRNAs may contribute to the development of inflammatory status in the vitreous of high myopic eyes.

Investigation of MicroRNA Expression in Anterior Lens Capsules of Senile Cataract Patients and MicroRNA Differences According to the Cataract Type

Purpose

We investigated the microRNAs (miRNAs) expression in the anterior lens capsules of patients with senile cataract and compared it to that in the anterior lens capsules of healthy controls. Moreover, we compared the differences in miRNAs expression according to the types of cataracts.

Methods

Individual lens epithelium samples were collected from 33 senile patients and 10 controls. The cataract patients were classified into cortical, nuclear, posterior and anterior subcapsular and mixed. The expression of 12 different miRNAs in lens epithelium was measured using real-time polymerase chain reaction and compared between the senile cataract patients and controls. The differences of miRNA levels according to cataract type were analyzed.

Results

The expression levels of let-7g-5p, miR-23a-3p, miR-23b-3p, and miR-125a-5p were significantly upregulated in patients with senile cataract when compared with those in the control group (P < 0.05). The expressions of let-7a-5p, let-7d-5p, miR-16-5p and miR-22-3p were significantly downregulated in the senile cataracts (P < 0.05). Let-7a-5p, let-7d-5p, let-7g-5p and mir-23b-3p had significant difference in expression between nuclear and anterior subcapsular cataracts.

Conclusions

The eight differentially expressed miRNAs may be involved in the pathogenesis of senile cataract, in particular, related to oxidative stress and autophagy.

Translational Relevance

We infer that several miRNAs in lens epithelial cells are promising candidate biomarkers of senile cataracts.

AQP5 regulates vimentin expression via miR-124-3p.1 to protect lens transparency

The pathogenesis of congenital cataract (CC), a major disease associated with blindness in infants, is complex and diverse. Aquaporin 5 (AQP5) represents an essential membrane water channel. In the present study, whole exome sequencing revealed a novel heterozygous missense mutation of AQP5 (c.152 T > C, p. L51P) in the four generations of the autosomal dominant CC (adCC) family. By constructing a mouse model of AQP5 knockout (KO) using the CRISPR/Cas9 technology, we observed that the lens of AQP5-KO mice showed mild opacity at approximately six months of age. miR-124-3p.1 expression was identified to be downregulated in the lens of AQP5-KO mice as evidenced by qRT-PCR analysis. A dual luciferase reporter assay confirmed that vimentin was a target gene of miR-124-3p.1. Organ-cultured AQP5-KO mouse lenses were showed increased opacity compared to those of WT mice, and vimentin expression was upregulated as determined by RT-PCR, western blotting, and immunofluorescence staining. After miR-124-3p.1 agomir was added, the lens opacity in WT mice and AQP5-KO mice decreased, accompanied by the downregulation of vimentin. AQP5-L51P increased vimentin expression of in human lens epithelial cells. Therefore, a missense mutation in AQP5 (c.152 T > C, p. L51P) was associated with adCC, and AQP5 could participate in the maintenance of lens transparency by regulating vimentin expression via miR-124-3p.1.

Long non-coding RNA MEG3 promotes cataractogenesis by upregulating TP53INP1 expression in age-related cataract

Age-related cataract (ARC) is the leading cause of visual impairment or even blindness among the aged population globally. Long non-coding RNA (LncRNA) has been proven to be the potential regulator of ARC. The latest study reveals that maternally expressed gene 3 (MEG3) promotes the apoptosis and inhibits the proliferation of multiple cancer cells. However, the expression and role of MEG3 in ARC are unclear. In this study, we investigated the effects of MEG3 in ARC and explored the regulatory mechanisms underlying these effects. We observed that MEG3 expression was up-regulated in the age-related cortical cataract (ARCC) lens capsules and positively correlated with the histological degree of ARCC. The pro-apoptosis protein, active caspase-3 and Bax increased in the anterior lens capsules of ARCC tissue, while the anti-apoptotic protein Bcl-2 decreased compared to normal lens. Knockdown of MEG3 increased the viability and inhibited the apoptosis of LECs upon the oxidative stress induced by H₂O₂. MEG3 was localized in both nucleus and cytoplasm in LECs. MEG3 facilitated TP53INP1 expression via acting as miR-223 sponge and promoting P53 expression. Additionally, TP53INP1 knockdown alleviated H₂O₂-induced lens turbidity. In summary, MEG3 promoted ARC progression by up-regulating TP53INP1 expression through suppressing miR-223 and promoting P53 expression, which would provide a novel insight into the pathogenesis of ARC.

TGF-β regulation of microRNA miR-497-5p and ocular lens epithelial cell mesenchymal transition

The purpose of this study was to investigate the role of a human lens microRNA (miR-497-5p) in regulating epithelialmesenchymal transition (EMT) under the control of transforming growth factor beta (TGF-β). A microRNA array was used to evaluate the microRNA profiles of untreated and TGF-β-treated human lens epithelial cells in culture. This showed that TGF-β treatment led to the upregulation of 96 microRNAs and downregulation of 39 microRNAs. Thirteen microRNAs were predicted to be involved in the pathogenesis of posterior capsule opacification (PCO). Meanwhile, overexpression of miR-497-5p suppressed cell proliferation and EMT 48 h post-transfection, and inhibition of miR-497-5p accelerated cell proliferation and EMT. Treatment with TGF-β inhibited the expression of miR-497-5p, but not cell proliferation. miR-497-5p was also found to regulate the level of CCNE1 and FGF7, which are reported to be actively involved in EMT. CCNE1 and FGF7 were bona fide targets of miR-497-5p. The results suggest that miR-497-5p participates in the direct regulation of lens epithelial cell EMT and is regulated by TGF-β. miR-497-5p may be a novel target for PCO therapy.

Molecular Processes Implicated in Human Age-Related Nuclear Cataract

Human age-related nuclear cataract is commonly characterized by four biochemical features that involve modifications to the structural proteins that constitute the bulk of the lens: coloration, oxidation, insolubility, and covalent cross-linking. Each of these is progressive and increases as the cataract worsens. Significant progress has been made in understanding the origin of the factors that underpin the loss of lens transparency. Of these four hallmarks of cataract, it is protein-protein cross-linking that has been the most intransigent, and it is only recently, with the advent of proteomic methodology, that mechanisms are being elucidated. A diverse range of cross-linking processes involving several amino acids have been uncovered. Although other hypotheses for the etiology of cataract have been advanced, it is likely that spontaneous decomposition of the structural proteins of the lens, which do not turn over, is responsible for the age-related changes to the properties of the lens and, ultimately, for cataract. Cataract may represent the first and best characterized of a number of human age-related diseases where spontaneous protein modification leads to ongoing deterioration and, ultimately, a loss of tissue function.

Expression of miR-34a in cataract rats and its related mechanism

Expression of miR-34a in cataract rats and its related mechanism were investigated. A total of 30 SD rats were selected and divided into three groups: group A: 2-month-old lucent lens, group B: 18-month-old lucent lens, and group C: 18-month-old naturally occurring cataract lens. The lens was taken and measured by LOC III to determine the degree of lens opacity of the three groups of rats. qPCR was used to detect expression of miR-34a and mRNA of SIRT1 and P53. Western blotting was used to detect the protein expression of SIRT1 and P53. Cell apoptosis was detected by flow cytometry. The lens of rats in group C was more turbid than that of groups A and B (P<0.05). The expression levels of miR-34a and P53 mRNA in the rats lens of group C were significantly higher than those in groups A and B, and the expression of SIRT1 mRNA was significantly lower than that of groups A and group B (P<0.05). Expression of miR-34a in group A was significantly higher than that in group B, the mRNA expression of SIRT1 was significantly lower than that in the lucent lens of 18-month-old rats (P<0.05). The expression of SIRT1 protein in group C was significantly lower than that in groups A and group B, while the expression level of P53 protein in group C was significantly higher than that of groups A and B. The expression of SIRT1 protein in group B was significantly higher than that in group A (P<0.05). The apoptosis rate of group C was higher than that of groups A and group B (P<0.05). In conclusion, the upregulation of expression level of miR-34a is related to cataract occurrence in rats, which may be caused by regulation of SIRT1 protein.

miR-15a: a potential diagnostic biomarker and a candidate for non-operative therapeutic modality for age-related cataract

Introduction: In order to better understand the role of hsa-miR-15a in the pathogenesis of age-related cataracts, we hypothesised altered expression, and of target anti-apoptotic genes, BCL-2 and MCL-1, in lens epithelial cells amongst age-related cataract patients.Material and methods: Reverse transcription quantitative polymerase chain reaction (RT-qPCR) quantified the expression of hsa-miR-15a and the target genes BCL-2 and MCL-1 in lens epithelial cells of 120 age-related cataract patients (40 patients with cortical cataracts, 40 patients with nuclear cataracts and 40 patients with posterior subcapsular cataracts) and 40 controls. Sixty specimens (15 normal and 45 cataracts) were stained immunohistochemically with BCL-2 and MCL-1 markers.Results: The expression of hsa-miR-15a was significantly increased (p = 0.003) in lens epithelial cells of cataract patients compared to the control group. BCL-2 and MCL-1 expression levels were significantly decreased in cataract patients (p < 0.001). A significant increase in hsa-miR-15a expression in the cortical subtype compared to the posterior subcapsular subtype (p = 0.003) and a significant decrease in BCL-2 and MCL-1 expressions in the cortical subtype compared to the nuclear and the posterior subcapsular subtype was detected.Conclusions: The increased expression of hsa-miR-15a in lens epithelial cells of cataract patients may repress the expression of BCL-2 and MCL-1. The expression of hsa-miR-15a and the subsequent apoptosis of lens epithelial cells are part of the pathogenesis of age-related cataracts.

lncRNA H19 contributes to oxidative damage repair in the early age-related cataract by regulating miR-29a/TDG axis

Age‐related cataract (ARC) is caused by the exposure of the lens to UVB which promotes oxidative damage and cell death. This study aimed to explore the role of lncRNA H19 in oxidative damage repair in early ARC. lncRNAs sequencing technique was used to identify different lncRNAs in the lens of early ARC patients. Human lens epithelial cells (HLECs) were exposed to ultraviolet irradiation; and 8‐OHdG ELISA, Cell counting kit 8 (CCK8), EDU, flow cytometry and TUNEL assays were used to detect DNA damage, cell viability, proliferation and apoptosis. Luciferase assay was used to examine the interaction among H19, miR‐29a and thymine DNA glycosylase (TDG) 3'UTR. We found that lncRNA H19 and TDG were highly expressed while miR‐29a was down‐regulated in the three types of early ARC and HLECs exposed to ultraviolet irradiation, compared to respective controls. lncRNA H19 knockdown aggravated oxidative damage, reduced cell viability and proliferation, and promoted apoptosis in HLECs, while lncRNA H19 overexpression led to opposite effects in HLECs. Mechanistically, miR‐29a bound TDG 3'UTR to repress TDG expression. lncRNA H19 up‐regulated the expression of TDG by repressing miR‐29a because it acted as ceRNA through sponging miR‐29a. In conclusion, the interaction among lncRNA H19, miR‐29a and TDG is involved in early ARC. lncRNA H19 could be a useful marker of early ARC and oxidative damage repair pathway of lncRNA H19/miR‐29a/TDG may be a promising target for the treatment of ARC.

MicroRNA-34a inhibits epithelial-mesenchymal transition of lens epithelial cells by targeting Notch1

Posterior capsule opacification (PCO) is a common long-term complication of modern cataract surgery. The epithelial-mesenchymal transition (EMT) of lens epithelial cells (LECs) is a crucial process in the development of PCO. The purpose of this study is to investigate the role of microRNA-34a (miR-34a) in the regulation of EMT and its target gene. Human LECs were treated with TGFβ2 to induce EMT as a model for PCO. The mRNA levels of miR-34a and EMT markers were examined by real-time quantitative polymerase chain reaction (qPCR). The expression level of miR-34a was downregulated, whereas that of Notch1 was upregulated in TGFβ2-induced EMT of LECs. Overexpression of miR-34a by transfection with miR-34a inhibited EMT of LECs and reduced the expression of Notch1; while, inhibition of miR-34a upregulated the expression of both Notch1 and its ligand Jagged1 in LECs. Luciferase reporter assays revealed that Notch1 gene was direct target of miR-34a. Moreover, DAPT, a specific inhibitor of Notch signaling pathway, reversed LEC-EMT. In addition, the expression level of miR-34a was downregulated, whereas that of Notch1 was upregulated in capsular opacification from cataract samples. MiR-34a can negatively regulate EMT of LECs by targeting Notch1. Therefore, miR-34a/Notch1 could serve as a potential therapeutic approach for the treatment of PCO.

MicroRNA-34a suppresses human lens epithelial cell proliferation and migration via downregulation of c-Met

MicroRNAs (miRNAs) are endogenously expressed, non-coding, small RNAs which inhibit protein translation through binding to target mRNAs. Recent studies have demonstrated that miRNAs participate in the regulation of a variety of cell structures and functions including those for cell proliferation and migration. MicroRNA-34a (miR-34a), a potential effector of the p53 tumor suppressor gene, is extensively studied for its suppression of cell growth. In the present study, we investigated the function of miR-34a in human lens epithelial cells. Following confirming that miR-34a expression was increased in a P53 dependent manner in human lens epithelial cells after treatment with doxorubicin, we demonstrated that overexpression of miR-34a in the human lens epithelial cell line HLE B3 led to a significant decrease in cell proliferation and migration, with the use of MTS and transwell migration assays. Moreover, HGF enhanced the proliferation and migration of human lens epithelial cells. miR-34a was found to downregulate the expression of c-Met protein by Western blotting. Furthermore, overexpression of miR-34a downregulated the levels of phosphorylated Akt, phosphorylated ERK1/2 and other cell cycle regulators. miR-34a expression was significantly reduced in posterior capsule opacification (PCO) clinical samples. These results demonstrate that miR-34a may act as a suppressor in PCO by regulating human lens epithelial cell proliferation and migration through downregulation of c-Met.

Identification of H2O2 induced oxidative stress associated microRNAs in HLE-B3 cells and their clinical relevance to the progression of age-related nuclear cataract

BACKGROUND

This study is aimed to screen out the microRNAs (miRNAs) associated with H₂O₂ induced oxidative stress in human lens epithelial B3 (HLE-B3) cell lines and investigate their relations with the progression of age-related nuclear cataract.

METHODS

H₂O₂ was used to induce oxidative stress in HLE-B3 cells. A genome-wide expression profiling of miRNAs in HLE-B3 cells was performed to select the differentially expressed miRNAs before and after H₂O₂ treatment. The selected miRNAs were validated by RT-PCR and fluorescence in situ hybridization (FISH). Clinical specimens were divided into three groups according to the Lens Opacities Classification System III (LOCSIII) and the expression levels of the selected miRNAs were tested by RT-PCR in the three groups. Bioinformatics analyses were applied to predict the target genes of the miRNA hits and construct the miRNA regulatory network. The expression level of MAPK14 was analyzed by Western blot.

RESULTS

The H₂O₂ induced oxidative stress model of HLE-B3 cells was established. Nineteen upregulated and 30 downregulated miRNAs were identified as differentially expressed miRNAs. Seven of the total 49 were validated in the cell model. RT-PCR of the clinical samples showed that the expression levels of miR-34a-5p, miR-630 and miR-335-3p were closely related with the severity of nuclear opacity. The images taken from FISH confirmed the results of RT-PCR. There were 172 target genes of the three miRNAs clustered in the category of response to stress. The regulatory network demonstrated that 23 target genes were co-regulated by multiple miRNAs. MAPK14 was the target gene of three miRNAs and the result were verified by Western blot.

CONCLUSION

Up-regulation of miR-34a-5p and miR-630 and down-regulation of miR-335-3p are related with the progression of age-related nuclear cataract and the underlying mechanism awaits further functional research to reveal.

Downregulation of microRNA-181a attenuates hydrogen peroxide-induced human lens epithelial cell apoptosis in vitro

Apoptosis of human lens epithelial (HLE) cells is a process closely associated with cataract formation. The aim of the present study was to explore the effects of microRNA (miR)‑181a against hydrogen peroxide (H2O2)-induced apoptosis in HLE cells in vitro. The recombinant lentiviral plasmid pLKO. 1‑puro‑miR‑181a was constructed and used to transfect human HLE‑B3 cells with the short hairpin (sh)RNA to silence the expression of miR‑181a. The apoptotic rate of both HLE‑B3 cells in which miR‑181a expression was stably silenced and in untransfected HLE‑B3 cells was assessed in the presence of H2O2 using flow cytometry. The mRNA expression levels of the apoptosis‑related genes caspase-3 (CASP3) and B‑cell lymphoma‑2‑associated X protein (BAX), and of the potential target genes for miR‑181a, c‑MET, cyclooxygenase 2 (COX‑2) and snail family transcriptional repressor 2 (SNAI2) were measured using reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR). Malondialdehyde (MDA), superoxide dismutase (SOD) and catalase (CAT) levels were assessed using ELISA. RT‑qPCR analysis revealed that miR‑181a expression was downregulated in HLE‑B3 cells following transfection with miR‑181a‑shRNA. Treatment with H2O2 significantly reduced the viability of HLE‑B3 cells, whereas miR‑181a knockdown was revealed to attenuate the effects on cell viability following H2O2 treatment. In addition, the downregulation of miR‑181a expression significantly decreased H2O2‑induced cell apoptosis, which was accompanied by a downregulation in CASP3 and BAX and COX‑2 expression. Furthermore, the levels of MDA were decreased, whereas the levels of SOD and CAT were increased following miR‑181a silencing. The present findings suggested that miR‑181a knockdown may protect HLE‑B3 cells against H2O2‑induced apoptosis in vitro. The molecular mechanisms involved in the protective effects of miR‑181a silencing may involve the suppression of CASP3, BAX and COX‑2 expression, and the inhibition of MDA generation.

MicroRNA-34a promotes mitochondrial dysfunction-induced apoptosis in human lens epithelial cells by targeting Notch2

Purpose

Human lens epithelial cell (HLEC) apoptosis is a common pathogenic mechanism in age-related cataracts (ARC). While the function of microRNAs (miRNAs) in the eye is beginning to be explored using miRNA expression array, the role of miR-34a in regulating HLEC apoptosis remains unknown and requires further investigation.

Methods

Quantitative reverse-transcript polymerase chain reaction (RT-PCR) was used to determine the expression level of miR-34a in cataractous and control samples. MiR-34a mimics and small interfering RNAs were transfected into SRA01/04. Cell apoptosis and oxidative stress were assessed by flow cytometry. The Dual-Luciferase Reporter Assay System was used to confirm whether miR-34a bound to the 3'-UTR of the target gene and blocked its activity. The potential roles of the identified target genes in apoptosis and mitochondria dysfunction were also evaluated.

Results

The expression of miR-34a increased in lens epithelial samples of ARC compared with the transparent group (cataract 2.41±0.81 vs. control 1.20±0.44, P=0.005). In cultured SRA01/04, miR-34a increased reactive oxygen species production and induced apoptosis (early apoptosis: 45.55%±5.96% vs. 15.85%±4.93%, P<0.01; late apoptosis: 6.10%±2.67% vs. 0.95%±0.42%, P<0.01). Overexpression of miR-34a promoted mitochondria-mediated apoptosis through activation of caspase-9, disruption of the mitochondrial membrane potential, blocking of mitochondrial energy metabolism and enhancement of cytochrome C release. Furthermore, Notch1 and Notch2 were confirmed as putative targets of miR-34a, but only Notch2 was verified as the effector that triggered mitochondria-mediated apoptosis.

Conclusion

MicroRNA-34a is increased in the cataractous lens and triggers mitochondria-mediated apoptosis and oxidative stress by suppressing Notch2.

MicroRNAs: new players in cataract

Cataract is the most common cause of blindness worldwide. Multiple factors such as aging, eye injury, diabetes mellitus, ultraviolet exposure, drug use and other ocular diseases are etiologically linked to cataractogenesis. Due to a rapid increase in aging population, age-related cataract has become the leading cause of blindness. Therefore, it is urgent to understand the molecular mechanism underlying cataractogenesis. MicroRNAs (miRNAs) are a group of endogenous, small noncoding RNAs that regulate gene expression at the post-translational level through binding with the 3'-untranslated regions of target mRNAs. Studies have shown that miRNAs play important roles in multiple cellular functions, including apoptosis, cell proliferation, senescence and stress response. Deregulated expression of miRNAs is also linked to the pathogenesis of many diseases, including ocular diseases. In our review, we focus on miRNAs that are involved in cataract development and discuss their potential applications as novel diagnostic markers and therapeutic targets.

MiR-30a inhibits BECN1-mediated autophagy in diabetic cataract

Purpose

To investigate the role of microRNAs in the regulation of autophagy and apoptosis in lens epithelial cells (LECs) during diabetic cataract formation.

Methods

A miRNA microarray study and quantitative real-time PCR were performed to identify the expression of miRNAs in LECs of diabetic cataract. Human LECs were cultured in high glucose conditions as a diabetic cataract model. BECN1 and LC3B were detected by Western blotting and quantitative real-time PCR. The extent of apoptosis was measured using FACSCalibur flow cytometry.

Results

Downregulation of miR-30a was identified in LECs attached to diabetic cataract tissues. By the bioinformatic assay and the luciferase activity assay, BECN1 was found to be a direct target of miR-30a. MiR-30a reduced the BECN1-mediated autophagy activity induced by high glucose in LECs in vitro. The ratio of LECs apoptosis was also decreased.

Conclusion

MiR-30a was involved in the inhibition of autophagy by targeting BECN1 in LECs in human diabetic cataract.

MicroRNAs as Peripheral Biomarkers in Aging and Age-Related Diseases

MicroRNAs (miRNAs) are found in the circulatory biofluids considering the important molecules for biomarker study in aging and age-related diseases. Blood or blood components (serum/plasma) are primary sources of circulatory miRNAs and can release these in cell-free form either bound with some protein components or encapsulated with microvesicle particles, called exosomes. miRNAs are quite stable in the peripheral circulation and can be detected by high-throughput techniques like qRT-PCR, microarray, and sequencing. Intracellular miRNAs could modulate mRNA activity through target-specific binding and play a crucial role in intercellular communications. At a pathological level, changes in cellular homeostasis lead to the modulation of molecular function of cells; as a result, miRNA expression is deregulated. Deregulated miRNAs came out from cells and frequently circulate in extracellular body fluids as part of various human diseases. Most common aging-associated diseases are cardiovascular disease, cancer, arthritis, dementia, cataract, osteoporosis, diabetes, hypertension, and neurodegenerative diseases such as Alzheimer's disease, Huntington's disease, Parkinson's disease, and amyotrophic lateral sclerosis. Variation in the miRNA signature in a diseased peripheral circulatory system opens up a new avenue in the field of biomarker discovery. Here, we measure the biomarker potential of circulatory miRNAs in aging and various aging-related pathologies. However, further more confirmatory researches are needed to elaborate these findings at the translation level.

Epigenetics and Common Ophthalmic Diseases

The study of ocular diseases and epigenetic dysregulation is an emerging area of research. The knowledge from the epigenetic mechanisms of DNA methylation, histone modifications, chromatin remodeling, and non-coding RNAs regarding the pathogenesis of ocular diseases will be helpful for improved treatment modalities for our patients. In particular, we focus upon the how epigenetic regulatory mechanisms impact five common ocular diseases: age related macular degeneration, age-related cataract, pterygium, retinoblastoma, and uveal melanoma. Hence, the foundation of this research paves the way for future specific therapeutic targets to treat and prevent vision loss.

MicroRNA-34a promoting apoptosis of human lens epithelial cells through down-regulation of B-cell lymphoma-2 and silent information regulator

AIM

To investigate the role of microRNA-34a (miR-34a) in the induction of apoptosis of human lens epithelial (HLE-B3) cells.

METHODS

The apoptosis of HLE-B3 cells was detected by Annexin V-PE apoptosis detection kit after the treatment with 200 µmol/L H₂O₂ for 24h and lentiviral miR-34a vector transfection. The expression of miR-34a in the cells was quantified by quantitative real time polymerase chain reaction (qRT-PCR) in response to H₂O₂ exposure and the vector transfection. The effects of overexpression of miR-34a on the expression of B-cell lymphoma-2 (Bcl-2) and silent information regulator 1 (SIRT1) was determined by qRT-PCR and Western blot.

RESULTS

The expression of miR-34a was up-regulated by the treatment of H₂O₂ in HLE-B3 cells. The increased expression of miR-34a is accompanied with the cell apoptosis. Consistence with the H₂O₂ exposure, ectopic overexpression of miR-34a in HLE-B3 cells promoted cells apoptosis. Importantly the anti-apoptosis factors Bcl-2 and SIRT1 were reduced significantly by up-regulation of miR-34a in HLE-B3 cells.

CONCLUSION

MiR-34a promotes the apoptosis of HLE-B3 cells by down-regulating Bcl-2 and SIRT1, suggesting that miR-34a may involve in the pathogenesis of cataract formation and targeting miR-34a may be a potentially therapeutic approach for treatment of cataract.

miR‑34a suppresses proliferation and induces apoptosis of human lens epithelial cells by targeting E2F3

microRNA (miRNA) is abnormally expressed in numerous diseases, and it was intimately associated with cell proliferation and apoptosis. However, the mechanism by which miRNAs control cataractogenesis remains unclear. In the current study, it was demonstrated that miR-34a was highly expressed in the cataractous lens by stem-loop reverse transcription-quantitative polymerase chain reaction. Trying to investigate the role of miR-34a in human lens epithelial cells, miR-34a mimics were transfected into SRA01/04 cells, and this suppressed proliferation and induced apoptosis. Subsequently, E2F3 was confirmed as a direct target of miR-34a. Downregulation of E2F3 by small interfering (si) RNA siE2F3 resulted in proliferation inhibition and apoptosis of SRA01/04 cells. Furthermore, it was demonstrated that miR-34a and siE2F3 downregulated E2F3 expression at a protein level. In summary, the current study demonstrated that miR-34a suppressed the proliferation and induced apoptosis of SRA01/04 cells by downregulating E2F3. These observations provide novel insights with potential therapeutic applications for the treatment of cataracts.

Expression of microRNAs in fibroblast of pterygium

AIM

To screen microRNAs (miRNAs) and set up target miRNAs in pterygium.

METHODS

Primary fibroblasts were isolated from pterygium and Tenon's capsule and cultured. Immunocytochemical analysis and Western blotting were performed to confirm the culture of fibroblasts. In all, 1733 miRNAs were screened in the first step by using GeneChip(®) miRNA3.0 Array. Specific miRNAs involved in the pathogenesis of pterygium were subsequently determined using the following criteria: 1) high reproducibility in a repetitive test; 2) base log value of >7.0 for both control and pterygial fibroblasts; and 3) log ratio of >1.0 between pterygial fibroblasts and control fibroblasts.

RESULTS

Primary screening showed that 887/1733 miRNAs were up-regulated and 846/1733 miRNAs were down-regulated in pterygial fibroblasts compared with those in control fibroblasts. Of the 1733 miRNAs screened, 4 miRNAs, namely, miRNA-143a-3p, miRNA-181a-2-3p, miRNA-377-5p and miRNA-411a-5p, met the above-mentioned criteria. Primary screening showed that these 4 miRNAs were up-regulated in pterygial fibroblasts compared with control fibroblasts and that miRNA-143a-3p had the highest mean ratio compared with the miRNAs in control fibroblasts.

CONCLUSION

miRNA-143a-3p, miRNA-181a-2-3p, miRNA-377-5p and miRNA-411a-5p are up-regulated in pterygial fibroblasts compared with control fibroblasts, suggesting their involvement in the pathogenesis of pterygium.

MicroRNA-184 Regulates Corneal Lymphangiogenesis

PURPOSE

MicroRNAs are a class of small noncoding RNAs that negatively regulate gene expression by binding to complimentary sequences of target messenger RNA. Their roles in corneal lymphangiogenesis are largely unknown. This study was to investigate the specific role of microRNA-184 (mir-184) in corneal lymphangiogenesis (LG) in vivo and lymphatic endothelial cells (LECs) in vitro.

METHODS

Standard murine suture placement model was used to study the expressional change of mir-184 in corneal inflammatory LG and the effect of synthetic mir-184 mimic on this process. Additionally, a human LEC culture system was used to assess the effect of mir-184 overexpression on cell functions in vitro.

RESULTS

Expression of mir-184 was significantly downregulated in corneal LG and, accordingly, its synthetic mimic suppressed corneal lymphatic growth in vivo. Furthermore, mir-184 overexpression in LECs inhibited their functions of adhesion, migration, and tube formation in vitro.

CONCLUSIONS

These novel findings indicate that mir-184 is involved critically in LG and potentially could be used as an inhibitor of the process. Further investigation holds the promise for divulging new therapies for LG disorders, which occur inside and outside the eye.

Epigenetics and ocular diseases: from basic biology to clinical study

Epigenetics is an emerging field in ophthalmology and has opened a new avenue for understanding ocular development and ocular diseases related to aging and environment. Epigenetic mechanisms, including DNA methylation, histone modifications, chromatin remodeling, and deployment of non-coding RNAs, result in the heritable silencing of gene expression without any change in DNA sequence. Accumulating evidence suggests a potential link between gene expression, chromatin structure, non-coding RNAs, and cellular differentiation during ocular development. Disruption of the balance of epigenetic networks could become the etiology of several ocular diseases. Here, we summarized the current knowledge about epigenetic regulatory mechanisms in ocular development and diseases.