Apoptosis and apoptosis related gene expression in normal conjunctiva and pterygium

RIPK3 and RIPK1 gene expression in pterygium: unveiling molecular insights into pathogenesis

BACKGROUND

Pterygium, characterized by the abnormal proliferation of epithelial cells, matrix remodeling, vascularization, and lesion migration, is a prevalent ocular surface disease involving the growth of fibrovascular tissue on the cornea. Despite the unclear underlying causes of pterygium, numerous investigations have indicated the involvement of cell death pathways in the regulation of cell cycle dynamics. Consequently, the objective of this study was to assess the expression levels of necroptosis markers in individuals diagnosed with pterygium, aiming to shed light on the potential role of necroptosis in the pathogenesis of this condition.

METHODS

This study aimed to investigate the expression patterns of receptor-interacting serine/threonine kinase 3 (RIPK3) and receptor-interacting serine/threonine kinase 1 (RIPK1) genes in pterygium tissues. 41 patients undergoing pterygium excision surgery were recruited. Resected pterygium samples and normal conjunctival tissues were collected, and RIPK3 and RIPK1 mRNA levels were measured using quantitative real-time PCR.

RESULTS

Our findings reveal that the expression of RIPK3 is significantly increased in samples obtained from individuals with pterygium. However, no significant alterations were observed in the expression of RIPK1 in these samples. Results showed significantly higher RIPK3 expression in pterygium tissues compared to controls. Moreover, increased RIPK3 levels correlated negatively with pterygium recurrence rates.

CONCLUSIONS

These findings suggest RIPK3 may play a protective role against pterygium recurrence through necroptosis.

Genomic instability and eye diseases

Background

Genetic information is stored in the bases of double-stranded DNA. However, the integrity of DNA molecules is constantly threatened by various mutagenic agents, including pollutants, ultraviolet light (UV), and medications. To counteract these environmental damages, cells have established multiple mechanisms, such as producing molecules to identify and eliminate damaged DNA, as well as reconstruct the original DNA structures. Failure or insufficiency of these mechanisms can cause genetic instability. However, the role of genome stability in eye diseases is still under-researched, despite extensive study in cancer biology.

Main text

As the eye is directly exposed to the external environment, the genetic materials of ocular cells are constantly under threat. Some of the proteins essential for DNA damage repair, such as pRb, p53, and RAD21, are also key during the ocular disease development. In this review, we discuss five ocular diseases that are associated with genomic instability. Retinoblastoma and pterygium are linked to abnormal cell cycles. Fuchs' corneal endothelial dystrophy and age-related macular degeneration are related to the accumulation of DNA damage caused by oxidative damage and UV. The mutation of the subunit of the cohesin complex during eye development is linked to sclerocornea.

Conclusions

Failure of DNA damage detection or repair leads to increased genomic instability. Deciphering the role of genomic instability in ocular diseases can lead to the development of new treatments and strategies, such as protecting vulnerable cells from risk factors or intensifying damage to unwanted cells.

State of the Art of Pharmacological Activators of p53 in Ocular Malignancies

The pivotal role of p53 in the regulation of a vast array of cellular functions has been the subject of extensive research. The biological activity of p53 is not strictly limited to cell cycle arrest but also includes the regulation of homeostasis, DNA repair, apoptosis, and senescence. Thus, mutations in the p53 gene with loss of function represent one of the major mechanisms for cancer development. As expected, due to its key role, p53 is expressed throughout the human body including the eye. Specifically, altered p53 signaling pathways have been implicated in the development of conjunctival and corneal tumors, retinoblastoma, uveal melanoma, and intraocular melanoma. As non-selective cancer chemotherapies as well as ionizing radiation can be associated with either poor efficacy or dose-limiting toxicities in the eye, reconstitution of the p53 signaling pathway currently represents an attractive target for cancer therapy. The present review discusses the role of p53 in the pathogenesis of these ocular tumors and outlines the various pharmacological activators of p53 that are currently under investigation for the treatment of ocular malignancies.

High-throughput screening of cytochrome P450 (CYP) family of genes in primary and recurrent pterygium

Pterygium is a common degenerative disease characterized fibrovascular outgrowth towards cornea. Around 200 million people have been reported to be affected by the pterygium in the world. Although the risk factors for pterygium are well documented, the molecular pathogenesis of pterygium seems to be very complex and remains highly elusive. However, the common sense for the development of pterygium appears to be deregulation of growth hemostasis due to aberrant apoptosis. In addition, pterygium shares many features with human cancers, including dysregulation of apoptosis, persistent proliferation, inflammation, invasion, and relapse following resection. Cytochrome P450 (CYP) monooxygenases are a superfamily of heme-containing enzymes with a wide range of structural and functional diversity. In the present study, we aimed to identify significant expression signatures of CYP gene in pterygium. For the study, a total number of 45 patients (30 primary and 15 recurrent pterygium) were included. For the high-throughput screening of CYP gene expression, Fluidigm 96.96 Dynamic Array Expression Chip was used and analyzed with BioMark™ HD System Real-Time PCR system. Remarkably, CYP genes were identified to be significantly overexpressed in both primary and recurrent pterygium samples. Most prominent overexpression was observed in CYP1A1, CYP11B2 and CYP4F2 in primary pterygium and CYP11A1 and CYP11B2 in recurrent pterygium. Consequently, present findings suggest the significant involvement of CYP genes in the development and progression of pterygium.

Nintedanib induces apoptosis in human pterygium cells through the FGFR2-ERK signalling pathway

AIM

To investigate whether nintedanib can inhibit pterygium cells through the fibroblast growth factor receptor 2 (FGFR2)/extracellular-signal-regulated kinase (ERK) pathway.

METHODS

Human primary pterygium cells were cultured in vitro. After treatment with nintedanib, the cell morphology was observed under microscopy, the morphological changes of the nucleus were observed after DAPI staining, apoptosis was analyzed by Annexin-V FITC/PI double staining, and the changes of apoptosis-associated proteins were detected by Western blot. The binding ability of nintedanib to FGFR2 was predicted by molecular docking. Finally, by silencing FGFR2, we explored whether nintedanib inhibited FGFR2/ERK pathway.

RESULTS

The results showed that nintedanib inhibited the growth of pterygium cells and caused nuclear pyknosis. The results of Annexin-VFITC/PI double staining showed that nintedanib was able to induce early and late apoptosis of pterygium cells, significantly increasing the expression of apoptosis-associated proteins Bax and cleaved-Caspase3 (P<0.05), and reducing the expression of Bcl-2 (P<0.05). In addition, nintedanib significantly inhibited ERK1/2 phosphorylation through FGFR2 (P<0.05). After silencing the expression of FGFR2, there was no significant difference in the inhibition of ERK1/2 phosphorylation by nintedanib (P>0.05).

CONCLUSION

Nintedanib induces apoptosis of pterygium cells by inhibiting FGFR2/ERK pathway.

Synergic Action of Insulin-like Growth Factor-2 and miRNA-483 in Pterygium Pathogenesis

Pterygium is a multifactorial disease in which UV-B is speculated to play a key role by inducing oxidative stress and phototoxic DNA damage. In search for candidate molecules that are useful for justifying the intense epithelial proliferation observed in pterygium, our attention has been focused on Insulin-like Growth Factor 2 (IGF-2), mainly detected in embryonic and fetal somatic tissues, which regulate metabolic and mitogenic functions. The binding between IGF-2 and its receptor Insulin-like Growth Factor 1 Receptor (IGF-1R) activates the PI3K-AKT pathway, which leads to the regulation of cell growth, differentiation, and the expression of specific genes. Since IGF2 is regulated by parental imprinting, in different human tumors, the IGF2 Loss of Imprinting (LOI) results in IGF-2- and IGF2-derived intronic miR-483 overexpression. Based on these activities, the purpose of this study was to investigate the overexpression of IGF-2, IGF-1R, and miR-483. Using an immunohistochemical approach, we demonstrated an intense colocalized epithelial overexpression of IGF-2 and IGF-1R in most pterygium samples (Fisher's exact test, p = 0.021). RT-qPCR gene expression analysis confirmed IGF2 upregulation and demonstrated miR-483 expression in pterygium compared to normal conjunctiva (253.2-fold and 12.47-fold, respectively). Therefore, IGF-2/IGF-1R co-expression could suggest their interplay through the two different paracrine/autocrine IGF-2 routes for signaling transfer, which would activate the PI3K/AKT signaling pathway. In this scenario, miR-483 gene family transcription might synergically reinforce IGF-2 oncogenic function through its boosting pro-proliferative and antiapoptotic activity.

Evaluation of JUN, FN1 and LAMB1 polymorphisms in pterygium in a Chinese Han population

PURPOSE

To explore the underlying molecular mechanism of pterygium and identify the key genes regulating the development of pterygium.

METHODS

Differentially expressed mRNAs were obtained from the Gene Expression Omnibus (GEO) database. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were performed using the DAVID (http://david.abcc.ncifcrf.gov/). The differential expressions of hub genes were verified using the reverse transcription-real-time fluorescent quantitative PCR (RT-qPCR). The function of the hub genes was further confirmed based on associations between the single nucleotide polymorphisms (SNPs) in hub genes and pterygium. The genotyping results were analyzed using SNPStats online software in five gene models, including codominant, dominant, recessive, overdominant, and log-additive. Five gene models were analyzed using SNPStats.

RESULTS

We found that 240 genes were significantly differentially expressed. Functional enrichment analysis showed that focal adhesion pathway is extremely meaningful, among which JUN, FN1, and LAMB1 were verified to significantly differentially express in pterygium (P = 0.0011, P = 0.0018, and P = 0.0050, respectively). However, the all nine candidate SNPs (rs11688, rs3748814 in JUN; rs1263, rs1132741, rs1250259 in FN1; rs20556, rs35710474, rs25659, rs4320486 in LAMB1), were not statistically associated with pterygium.

CONCLUSION

Our results demonstrated that JUN, FN1, and LAMB1 polymorphisms were not associated with susceptibility to pterygium in Chinese Han population. Considering the fact that these three genes are differentially expressed in pterygium, further research is needed to explain its involvement in pterygium.

Vascular Endothelial Growth Factor expression patterns in non- Human Papillomavirus - related pterygia: an experimental study on cell spot arrays digital analysis

PURPOSE

The role of angiogenic factors -such as vascular endothelial growth factor (VEGF) - in development and progression of pterygia lesions remains under investigation. In the current study, we analyzed VEGF protein expression in a series of pterygia and normal conjunctiva epithelia.

METHODS

Using a liquid based cytology assay, thirty (n = 30) cell specimens were obtained by applying a smooth scraping on conjunctiva epithelia and fixed accordingly. None of them had a history of Human Papillomavirus (HPV) infection. Similarly, the same process was applied also in normal conjunctiva epithelia (n = 10; control group). We constructed five (n = 5) slides each containing eight (n = 8) cell spots. An immunocytochemistry (ICC) assay was implemented. Digital image analysis was also performed for evaluating objectively the corresponding immunostaining intensity levels.

RESULTS

All the examined pterygia cell samples over expressed the marker. High staining intensity levels were detected in 15/30 (50%), whereas the rest 15/30 (50%) demonstrated moderate expression. Overall VEGF expression was statistically significantly higher in pterygia compared to normal conjunctiva epithelia (p=.0001). Concerning the other parameters, VEGF protein expression did not associate with the gender of the patients (p = 0.518), the presence of recurrent lesion (p = 0.311), the anatomical location (p = 0.191) or with their morphology (p = 0.316). Interestingly, the recurrent lesions demonstrated the highest levels of VEGF expression.

CONCLUSIONS

VEGF over expression is a frequent event in pterygia playing a potentially central molecular role in the progression of the lesion. Cell spot array analysis -based on liquid cytology- seems to be an innovative, easy to use technique for analyzing a broad variety of molecules in multiple specimens on the same slide by applying different ICC assays.

Characterization of the Cellular Microenvironment and Novel Specific Biomarkers in Pterygia Using RNA Sequencing

With a worldwide prevalence of ~12%, pterygium is a common degenerative and environmentally triggered ocular surface disorder characterized by wing-shaped growth of conjunctival tissue onto the cornea that can lead to blindness if left untreated. This study characterizes the transcriptional profile and the cellular microenvironment of conjunctival pterygia and identifies novel pterygia-specific biomarkers. Formalin-fixed and paraffin-embedded pterygia as well as healthy conjunctival specimens were analyzed using MACE RNA sequencing (n = 8 each) and immunohistochemistry (pterygia n = 7, control n = 3). According to the bioinformatic cell type enrichment analysis using xCell, the cellular microenvironment of pterygia was characterized by an enrichment of myofibroblasts, T-lymphocytes and various antigen-presenting cells, including dendritic cells and macrophages. Differentially expressed genes that were increased in pterygia compared to control tissue were mainly involved in autophagy (including DCN, TMBIM6), cellular response to stress (including TPT1, DDX5) as well as fibroblast proliferation and epithelial to mesenchymal transition (including CTNNB1, TGFBR1, and FN1). Immunohistochemical analysis confirmed a significantly increased FN1 stromal immunoreactivity in pterygia when compared to control tissue. In addition, a variety of factors involved in apoptosis were significantly downregulated in pterygia, including LCN2, CTSD, and NISCH. Furthermore, 450 pterygia-specific biomarkers were identified by including transcriptional data of different ocular surface pathologies serving as controls (training group), which were then validated using transcriptional data of cultured human pterygium cells. Among the most pterygia-specific factors were transcripts such as AHNAK, RTN4, TPT1, FSTL1, and SPARC. Immunohistochemical validation of SPARC revealed a significantly increased stromal immunoreactivity in pterygia when compared to controls, most notably in vessels and intravascular vessel wall-adherent mononuclear cells. Taken together, the present study provides new insights into the cellular microenvironment and the transcriptional profile of pterygia, identifies new and specific biomarkers and in addition to fibrosis-related genes, uncovers autophagy, stress response and apoptosis modulation as pterygium-associated processes. These findings expand our understanding of the pathophysiology of pterygia, provide new diagnostic tools, and may enable new targeted therapeutic options for this common and sight-threatening ocular surface disease.

Evaluation of Cyclooxygenase-2 and p53 Expression in Pterygium Tissue Following Preoperative Intralesional Ranibizumab Injection

Introduction: Overexpression of vascular endothelial growth factor (VEGF), cyclooxygenase-2 (COX-2), and p53 are the postulated aetiopathogenesis in pterygium. VEGF is responsible for the induction of COX-2 expression, whereas p53 plays an important role in the regulation of VEGF. This study aimed to evaluate the immunohistochemistry of COX-2 and p53 expressions from excised pterygium tissue from patients who received intralesional ranibizumab (anti-VEGF) injection 2 weeks prior to pterygium surgery. Materials and Methods: An interventional comparative study involving patients presenting with primary pterygium was conducted between September 2015 and November 2017. The patients were randomized into either the intervention or control group. Patients in the intervention group were injected with intralesional ranibizumab (0.5 mg/0.05 ml) 2 weeks prior to surgery. Both groups underwent pterygium excision followed by conjunctival autograft. Immunohistochemistry staining was performed to evaluate COX-2 and p53 expressions in the excised pterygium tissue. Results: A total of 50 patients (25 in both the intervention and control groups) were recruited. There were 34 (68%) patients with grade III pterygium and 16 (32%) patients with grade IV pterygium. There was statistically significant difference in reduction of COX-2 expression in the epithelial layer [84.0% (95% CI: 63.9, 95.5)] (p = 0.007) and stromal layer [84.0% (95% CI: 63.9, 95.5)] (p < 0.001) between intervention and control groups. There was no significant difference in the reduction of p53 expression between the two groups. Conclusion: This study demonstrated the possible use of intralesional anti-VEGF treatment prior to pterygium excision as a potential future modality of adjunctive therapy for pterygium surgery.

The roles of mouse double minute 2 (MDM2) oncoprotein in ocular diseases: A review

Mouse double minute 2 (MDM2), an E3 ubiquitin ligase and the primary negative regulator of the tumor suppressor p53, cooperates with its structural homolog MDM4/MDMX to control intracellular p53 level. In turn, overexpression of p53 upregulates and forms an autoregulatory feedback loop with MDM2. The MDM2-p53 axis plays a pivotal role in modulating cell cycle control and apoptosis. MDM2 itself is regulated by the PI3K-AKT and RB-E2F-ARF pathways. While amplification of the MDM2 gene or overexpression of MDM2 (due to MDM2 SNP T309G, for instance) is associated with various malignancies, numerous studies have shown that MDM2/p53 alterations may also play a part in the pathogenetic process of certain ocular disorders (Fig. 1). These include cancers (retinoblastoma, uveal melanoma), fibrocellular proliferative diseases (proliferative vitreoretinopathy, pterygium), neovascular diseases, degenerative diseases (cataract, primary open-angle glaucoma, age-related macular degeneration) and infectious/inflammatory diseases (trachoma, uveitis). In addition, MDM2 is implicated in retinogenesis and regeneration after optic nerve injury. Anti-MDM2 therapy has shown potential as a novel approach to treating these diseases. Despite major safety concerns, there are high expectations for the clinical value of reformative MDM2 inhibitors. This review summarizes important findings about the role of MDM2 in ocular pathologies and provides an overview of recent advances in treating these diseases with anti-MDM2 therapies.

The Role of the Stromal Extracellular Matrix in the Development of Pterygium Pathology: An Update

Pterygium is a benign fibrovascular lesion of the bulbar conjunctiva with frequent involvement of the corneal limbus. Its pathogenesis has been mainly attributed to sun exposure to ultraviolet-B radiation. Obtained evidence has shown that it is a complex and multifactorial process which involves multiple mechanisms such as oxidative stress, dysregulation of cell cycle checkpoints, induction of inflammatory mediators and growth factors, angiogenic stimulation, extracellular matrix (ECM) disorders, and, most likely, viruses and hereditary changes. In this review, we aim to collect all authors’ experiences and our own, with respect to the study of fibroelastic ECM of pterygium. Collagen and elastin are intrinsic indicators of physiological and pathological states. Here, we focus on an in-depth analysis of collagen (types I and III), as well as the main constituents of elastic fibers (tropoelastin (TE), fibrillins (FBNs), and fibulins (FBLNs)) and the enzymes (lysyl oxidases (LOXs)) that carry out their assembly or crosslinking. All the studies established that changes in the fibroelastic ECM occur in pterygium, based on the following facts: An increase in the synthesis and deposition of an immature form of collagen type III, which showed the process of tissue remodeling. An increase in protein levels in most of the constituents necessary for the development of elastic fibers, except FBLN4, whose biological roles are critical in the binding of the enzyme LOX, as well as FBN1 for the development of stable elastin. There was gene overexpression of TE, FBN1, FBLN5, and LOXL1, while the expression of LOX and FBLN2 and -4 remained stable. In conclusion, collagen and elastin, as well as several constituents involved in elastic fiber assembly are overexpressed in human pterygium, thus, supporting the hypothesis that there is dysregulation in the synthesis and crosslinking of the fibroelastic component, constituting an important pathogenetic mechanism for the development of the disease.

Evaluation of Primary Pterygia on Basis of the Loss of Vertical Length of Plica Semilunaris

Purpose

To propose a new grading system for primary pterygia based on the morphological loss of vertical length of plica semilunaris (LPS).

Methods

We included 50 eyes from 41 patients with primary pterygium. LPS was defined and quantified as the ratio of the length of loss of the normal vertical morphology at plica semilunaris to the vertical corneal diameter using anterior-segment photographs. Grades of tear metalloproteinase 9 (MMP-9) expression by point-of-care immunoassay, which is a well-known biomarker for inflammation, was correlated with the extent of LPS (%) of pterygia. Then, LPS was paralleled with the pre-established grading systems on the basis of tissue translucency (i.e., T grade) and vascularity (i.e., V grade) of the pterygium body.

Results

MMP-9 grades was 2.39 ± 1.12 in the group with LPS ≥50% and was 1.56 ± 1.12 in the group with LPS <50% (P = 0.016). In a linear regression, the extent of LPS was positively correlated with MMP-9 grades (r = 0.315, P = 0.026). MMP-9 expression did not differ between T grades or V grades. The extents of LPS were well correlated positively with both T grades (r = 0.495 and P < 0.001) and V grades (r = 0.344 and P = 0.015).

Conclusions

We devised a new grading system using LPS on the basis of morphological loss of the normal vertical plica semilunaris in primary pterygia. The extent of LPS correlated well with T grades and V grades and also reflected the expression of MMP-9 in tears.

Translational Relevance

The new clinical LPS grading system reflects severity and MMP-9 expression in tears in primary pterygia.

MiR-15a Participated in the Pathogenesis of Pterygium via Targeting BCL-2：An Experimental Research

Purpose: To compare the expression levels of miR-15a between pterygium and normal conjunctiva, and further investigate the potential role of miR-15a in the progression of pterygium.Methods: 21 cases of primary pterygium were enrolled in our study. The length of the pterygium invaded into the cornea and the total thickness of the pterygium were measured with anterior segment optical coherence tomography (AS-OCT). The pterygial and adjacent normal conjunctival samples of the 21 patients were collected. Expressions of miR-15a, BCL-2, Bax in both pterygium and normal conjunctiva were measured, and correlations between miR-15a and BCL-2, miR-15a and Bax, miR-15a and clinical parameters were made. Pterygium epithelial cells (PECs) were isolated, cultured and transfected with miR-15a mimic or miR-15a inhibitor to interfere the miR-15a expression levels. The regulation of BCL-2 expression by miR-15a was examined with Real-Time PCR (RT-PCR), Western blot and immunofluorescence. The regulation of Bax expression by miR-15a was also examined with Real-Time PCR (RT-PCR) and Western blot. The cell viability of the transfected PECs was measured with the CCK-8 assay and the apoptosis in these cells was detected using the TUNEL assay.Results: The expression of miR-15a, Bax were significantly decreased while the BCL-2 was significantly increased in pterygium (p < .05). There was a negative correlation in expression between miR-15a and BCL-2 in pterygium tissues (r = -0.516, p < .05). We also found that relative miR-15a level was positively correlated with the length of pterygium invaded into the cornea (r = -0.570, p < .05). In cultured PECs, miR-15a could downregulate the expression of BCL-2 and upregulate the expression of Bax. Promotion of miR-15a could suppress cell proliferation and promote cell apoptosis in cultured PECs.Conclusions: Our study demonstrated that decreased expression of miR-15a in pterygium might be associated with the apoptosis and proliferation of abnormal cell via regulating BCL-2, which could subsequently contribute to the development of pterygium. Downregulation of miR-15a might also contribute to the pathogenesis of pterygium by other mechanisms including abnormal proliferation and neovascularization, which remain to be investigated.

Pterygium-The Good, the Bad, and the Ugly

Pterygium is a multifaceted pathology that displays apparent conflicting characteristics: benign (e.g., self-limiting and superficial), bad (e.g., proliferative and potentially recurrent) and ugly (e.g., signs of preneoplastic transformation). The natural successive question is: why are we lacking reports showing that pterygium lesions become life-threatening through metastasis, especially since pterygium has considerable similarities with UV-related malignancies on the molecular level? In this review, we consider how our pathophysiological understanding of the benign pterygium pathology overlaps with ocular surface squamous neoplasia and skin cancer. The three UV-related disorders share the same initial insult (i.e., UV radiation) and responsive repair mechanisms to the ensuing (in)direct DNA damage. Their downstream apoptotic regulators and other cellular adaptations are remarkably alike. However, a complicating factor in understanding the fine line between the self-limiting nature of pterygium and the malignant transformation in other UV-related diseases is the prominent ambiguity in the pathological evaluation of pterygium biopsies. Features of preneoplastic transformation (i.e., dysplasia) are used to define normal cellular reactions (i.e., atypia and metaplasia) and vice versa. A uniform grading system could help in unraveling the true nature of this ancient disease and potentially help in identifying the earliest intervention point possible regarding the cellular switch that drives a cell’s fate towards cancer.

Expression of p53 and Ki-67 proteins in patients with increasing severity and duration of pterygium

Purpose:

Pterygium is a triangular fibrovascular subepithelial ingrowth of degenerative bulbar conjunctival tissue over the cornea. It is now considered to be a result of uncontrolled cellular proliferation as overexpression of p53 protein and Ki-67 nuclear protein was found in the epithelium. This study was done to find the expression of p53 and Ki-67 with the severity and duration of the pterygium to explain the etiopathogenesis.

Methods:

Data were analyzed from 43 Indian participants of all age groups. All patients were divided according to the severity of pterygium (mild, moderate, and severe groups) and according to the duration of pterygium (<4 years and >4 years). The samples were studied by immunohistochemistry by using antibodies against p53 and Ki-67 proteins considering >5% expression as significant.

Results:

Of 43 cases, p53 and Ki-67 expression were positive in 33 cases. In mild, moderate, and severe cases p53 positivity was 33.3%, 78.4%, 100%, respectively. P53 expression increased with duration, 79.3% positive in <4 years, and 92.9% positive in >4 years. With increasing severity of pterygium, mild, moderate, and severe cases, Ki-67 positivity was 66.7%, 78.37%, 66.7%, respectively. Ki-67 expression with duration, 79.3% positive in <4 years, and 85.7% positive in >4 years of the duration of pterygium with no statistical significance.

Conclusion:

Our study revealed that with increasing duration and severity of pterygium, p53 expression was observed to be increasing. Ki-67 expression increased with the duration of pterygium but not with the severity.

Prevalence of Pterygium and Associated Risk Factors in the High-Altitude Area of Ta'if City, Saudi Arabia

Background

Pterygium is an important public health problem. The prevalence rates of this disease varies widely from 1.2% to 23.4%.

Aim

To determine the prevalence rates and the associated risk factors of pterygium in the high-altitude area - Ta’if city, Saudi Arabia.

Material and method

A cross-sectional study was carried out from September 2018 till September 2019 at the ophthalmology outpatient clinics of King Abdul-Aziz Specialist Hospital, Ta’if area.

Results

Prevalence rate of pterygium in the high-altitude area, Ta’if city, Saudi Arabia was 2.4%. It is significantly higher in older patients belonging to the age group of more than 40 years. As for gender, it was significantly higher in male patients compared to females (2.6% vs. 1.9%). Pterygium prevalence was significantly higher among patients with outdoor occupations compared to indoor occupations (2.9% vs. 2.1%), and among patients with sunlight exposure during daily activities for more than 5 hours (2.6% vs. 2%) (p =< 0.05).

Conclusion

The overall incidence of pterygium in Al-Ta’if area, Saudi Arabia, was 2.4% but still lower than overall worldwide incidence (10.2%). There was an increased incidence of pterygium with age, high-altitude areas, rural areas, outdoor occupations, which is directly proportional to dose of sunlight exposure. Furthermore, smoking might be reported as a protective factor against pterygium.

Identification of Functional Genes in Pterygium Based on Bioinformatics Analysis

Purpose

The competing endogenous RNA (ceRNA) network regulatory has been investigated in the occurrence and development of many diseases. This research aimed at identifying the key RNAs of ceRNA network in pterygium and exploring the underlying molecular mechanism.

Methods

Differentially expressed long noncoding RNAs (lncRNAs), microRNAs (miRNAs), and mRNAs were obtained from the Gene Expression Omnibus (GEO) database and analyzed with the R programming language. LncRNA and miRNA expressions were extracted and pooled by the GEO database and compared with those in published literature. The lncRNA-miRNA-mRNA network was constructed of selected lncRNAs, miRNAs, and mRNAs. Metascape was used to perform Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses on mRNAs of the ceRNA network and to perform Protein-Protein Interaction (PPI) Network analysis on the String website to find candidate hub genes. The Comparative Toxicogenomic Database (CTD) was used to find hub genes closely related to pterygium. The differential expressions of hub genes were verified using the reverse transcription-real-time fluorescent quantitative PCR (RT-qPCR).

Result

There were 8 lncRNAs, 12 miRNAs, and 94 mRNAs filtered to construct the primary ceRNA network. A key lncRNA LIN00472 ranking the top 1 node degree was selected to reconstruct the LIN00472 network. The GO and KEGG pathway enrichment showed the mRNAs in ceRNA networks mainly involved in homophilic cell adhesion via plasma membrane adhesion molecules, developmental growth, regulation of neuron projection development, cell maturation, synapse assembly, central nervous system neuron differentiation, and PID FOXM1 PATHWAY. According to the Protein-Protein Interaction Network (PPI) analysis on mRNAs in LINC00472 network, 10 candidate hub genes were identified according to node degree ranking. Using the CTD database, we identified 8 hub genes closely related to pterygium; RT-qPCR verified 6 of them were highly expressed in pterygium.

Conclusion

Our research found LINC00472 might regulate 8 hub miRNAs (miR-29b-3p, miR-183-5p, miR-138-5p, miR-211-5p, miR-221-3p, miR-218-5p, miR-642a-5p, miR-5000-3p) and 6 hub genes (CDH2, MYC, CCNB1, RELN, ERBB4, RB1) in the ceRNA network through mainly PID FOXM1 PATHWAY and play an important role in the development of pterygium.

Relative gene expression analysis of human pterygium tissues and UV radiation-evoked gene expression patterns in corneal and conjunctival cells

A sight threatening, pterygium is a common ocular surface disorders identified by fibrovascular growth of the cornea and induced by variety of stress factors, like ultraviolet (UV) exposure. However, the genes involved in the etiopathogenesis of this disease is not well studied. Herein, we identified the gene expression pattern of pterygium and examined the expression of pterygium-related genes in UV-B-induced human primary cultured corneal epithelial cells (HCEpCs), telomerase immortalized human corneal epithelial (hTCEpi), primary conjunctival fibroblast (HConFs) and primary pterygium fibroblast cells (HPFCs). A careful analysis revealed that the expression of 10 genes was significantly modulated (by > 10-fold). Keratin 24 (KRT24) and matrix metalloproteinase 9 (MMP-9) were dramatically upregulated by 49.446- and 24.214-fold, respectively. Intriguingly, UV-B exposure (50 J/m²) induced the upregulation of the expressions of MMP-9 in corneal epithelial cells such as HCEpCs and hTCEpi. Furthermore, UV-B exposure (100 and/or 200 J/m²) induced the upregulation of the expressions of MMP-9 in fibroblast such as HConFs and HPFCs. The exposure of HCEpCs to 100 and 200 J/m² UV-B induced significant expressions of KRT24 mRNA. Nevertheless, no expression of KRT24 mRNA was detected in HConFs and HPFCs. The findings provide evidence that the progression of pterygium may involve the modulation of extracellular matrix-related genes and vasculature development and the up-regulation of KRT24 and MMP-9 by UV stress. UV radiation may promote the modulation of these pterygium-related genes and induce the initiation and progression of human pterygium.

Bcl-2, p53, and Ki-67 expression in pterygium and normal conjunctiva and their relationship with pterygium recurrence

PURPOSE

Pterygium is a common lesion of the ocular surface, and its etiology and pathogenesis are still uncertain. This study aimed to investigate the role of apoptosis and proliferation in pterygium formation and recurrence.

MATERIALS AND METHODS

In this study, p53, Bcl-2, and Ki-67 expression levels were evaluated in primary pterygium (n = 35) and recurrent pterygium (n = 32) tissue samples and compared with normal conjunctiva (n = 30) tissue samples. In addition, recurrent pterygiums were divided into three groups based on recurrence time, and their p53, Bcl-2, and Ki-67 expression levels were compared.

RESULTS

The results show that p53, Bcl-2, and Ki-67 expression levels were significantly higher in the pterygium tissue samples as compared to the control group (p < 0.001, p < 0.001, and p < 0.001, respectively). When primary and recurrent pterygium tissues were compared, bcl-2 expression was higher in recurrent pterygium tissue samples (p = 0.003). However, when Ki-67 and p53 expression levels were evaluated, no significant difference was found between primary and recurrent pterygium (p = 0.215, p = 0.321, respectively). Also, p53 and Ki-67 expression were correlated in pterygium tissue samples, and Bcl-2 expression was significantly higher in pterygium that recurrence in the first 6 months after surgery. There was no difference between groups 1, 2, and 3 in terms of p53 and Ki-67 expression.

CONCLUSION

Antiapoptotic mechanisms and proliferation play an important role in the etiopathogenesis of pterygium. Furthermore, Bcl-2 expression may be important in pterygium recurrence.

The Association of MMP7 Genotype With Pterygium

BACKGROUND/AIM

In literature, few studies have examined the diagnostic or prognostic potential of matrix metalloproteinases (MMP) in pterygium, whose formation and progression are closely related to imbalance in the extracellular microenvironment. In this study, we investigated the contribution of MMP7 promoter (A-181G and C-153T) polymorphic genotypes to pterygium risk.

MATERIALS AND METHODS

A total of 134 cases and 268 controls were collected and their MMP7 genotypes at A-181G and C-153T were examined by polymerase chain reaction-restriction fragment length polymorphism methodology.

RESULTS

The AA, AG and GG genotypes at MMP7 promoter A-181G were non-significantly differentially distributed between the two groups at 85.8, 11.2 and 3.0%, respectively, in pterygium cases and 88.4, 9.7 and 1.9% in controls, respectively (p for trend=0.6822). There was no polymorphic genotype for MMP7 C-153T among our Taiwanese cohort.

CONCLUSION

A-181G and C-153T genotypes at MMP7 do not have a direct role in determining Taiwanese susceptibility to pterygium.

Analysis of WWOX gene expression and protein levels in pterygium

PURPOSE

Pterygium, a degenerative and hyperplastic lesion, has premalignant properties as a tumor analog. WWOX is a tumor suppressor gene and involved in many signal pathways, such as cell proliferation, embryonic development, metabolism and apoptosis. In many cancers, the loss of WWOX or the presence of abnormal transcripts indicates the tumor suppressor activity of WWOX. In this study, it was aimed to determine WWOX gene expression and protein levels in pterygium which may be a tumor analog.

METHODS

For this purpose, the WWOX gene expression change in 27 pterygium tissue was investigated by real-time PCR method, and the change in WWOX protein was investigated using the Western blot method.

RESULTS

According to our results, it was found that the expression and protein levels of WWOX gene in pterygium tissue decreased significantly compared to control tissue (p < 0.05).

CONCLUSION

This information indicates that a decrease in expression and protein level in pterygium tissue of WWOX, a tumor suppressor gene, supports claims that pterygium may be a cancer analog tissue.

Pterygium: new insights

Pterygia are common conjunctival degenerations with well-documented risk factors but an unclear pathogenesis. Better understanding of the pathogenesis of pterygium could lead to improved surgical outcomes and decreased postoperative recurrence. Currently, pterygium excision with conjunctival autograft remains the preferred surgical technique to decrease pterygium recurrence. Many adjuvant therapies have been used in pterygium surgery to varying degrees of success. Topical cyclosporine, an immunosuppressive medication, in conjunction with conjunctival autograft was found to be most successful in decreasing pterygium recurrence according to a recent meta-analysis. Other adjuvant therapies such as mitomycin-C (MMC), 5-fluorouracil (5-FU), and beta-irradiation have also been used, though usage of these may cause multiple adverse effects. Recent research indicates that interactions between mouse double minute 2 (MDM2) and p53 could play a role in the occurrence of pterygium. Nutlin, an MDM2 antagonist, was found to have significantly less toxicity in conjunctival cells when compared with MMC on laboratory analysis of pterygium samples.

A novel role for Livin in the response to ultraviolet B radiation and pterygium development

A pterygium is an inflammatory, invasive and proliferative lesion on the ocular surface, which can decrease visual acuity, damage the ocular surface and affect the appearance of the eye. However, the underlying molecular mechanisms of the pathogenesis remain unclear. In the present study, the role of apoptosis-associated protein Livin in the occurrence and development of pterygium was investigated. Primary samples from quiescent or advanced clinical stages of pterygium and normal human conjunctival tissues were used to assess mRNA and protein expression levels of Livin using reverse transcription-quantitative PCR and immunohistochemistry, respectively. Livin was knocked down in pterygium epithelial cells (PECs) using small interfering RNA (siRNA), to investigate the role of Livin in PEC viability, migration, invasion ability and apoptosis. The cell viability, invasion ability and apoptosis of PECs following ultraviolet B (UVB) radiation alone or in combination with Livin silencing were also analyzed. Expression levels of Livin increased in the pterygium tissues compared with those in the normal conjunctiva at both the mRNA and protein levels. Livin expression levels in advanced pterygium were significantly higher compared with those in quiescent pterygium samples. Knockdown of Livin expression levels significantly reduced cell migration, invasion ability and cell viability, and induced apoptosis of PECs. Inhibition of Livin expression in PECs increased the expression levels of caspase-7, caspase-3 and E-cadherin, whereas expression levels of Snail were downregulated. Cell viability and invasion ability in PECs was enhanced following UVB radiation and Livin expression upregulated. UVB irradiation induced cell invasion ability of PECs and this was attenuated by Livin-silencing. Transfection with Livin siRNA also partially recovered the apoptosis rate of PECs, which was reduced by UVB irradiation. In conclusion, Livin was upregulated in pterygium, and UVB radiation functions in the development of pterygium by inducing Livin expression.

Correlation of pterygium severity with IQ-domain GTPase-activating protein 1 (IQGAP1) and mast cells

IQ-domain GTPase-activating protein 1 (IQGAP1) is a multidomain scaffold protein that is involved in cytoskeleton dynamics and tumor metastasis. Although the role of IQGAP1 in various cancers had been reported, the function of IQGAP1 in pterygium has not been studied. In this study, surgically excised pterygium and control conjunctival tissue from cataract patients were analysed by immunohistochemistry, confocal microscopy, and Western blot for IQGAP1 expression, mast cell counts, and microvascular count. Pterygium was clinically divided into mild and severe types according to Tan's classification and Kim's criteria based on translucency and vascularity of the tissue. Greater clinical severity of pterygium was associated with higher expression of IQGAP1 expression. Compared to normal conjunctival tissue, severe pterygium had significantly higher IQGAP1 expression (P = 0.005), which strongly correlated to the number of microvessels (P = 0.003) and mast cells (P = 0.01). Confocal microscopy revealed IQGAP1 colocalization with mast cell and CD31. IQGAP1 expression was higher in the pterygium body compared to the head. In conclusion, the level of IQGAP1 expression was found to be correlated to the clinical severity of pterygium. Mast cells were identified in pterygium and is suspected to be involved in promoting fibrovascular invasion.

Association between Blepharoptosis and Pterygium in Korea: A Population-Based Study during 2010-2012

PURPOSE

To investigate possible correlations between blepharoptosis and pterygium in a nationally representative sample of the Korean population.

METHODS

This population-based, cross-sectional study was comprised of 3,685 males and 4,792 females (≥ 19 years of age) participating in the fifth annual Korea National Health and Nutrition Examination Survey (KNHANES) from 2010 to 2012. The enrolled subjects underwent interviews, clinical examinations, and laboratory tests. Statistical tests were used to compare the prevalence of blepharoptosis, according to pterygium subtypes or pterygium existence. Multiple logistic regression analyses were also used to find the associations of blepharoptosis with pterygium.

RESULTS

Pterygium was present in 10.3% of males and 9.8% of females. The odds ratios (ORs) of pterygium in Korean males significantly decreased as the severity of blepharoptosis increased (p for trend = 0.0252). Using three models in multivariate analyses, males with blepharoptosis had an OR (95% confidence interval, (CI)) of 0.643 (0.435 ~ 0.951) for pterygium compared with males with no blepharoptosis, after adjusting for age, body mass index, smoking status, alcohol consumption, physical activity, serum vitamin D levels, diabetes mellitus, metabolic syndrome, high blood pressure, and stress intolerance. There was no significant association between blepharoptosis and females.

CONCLUSIONS

The association between blepharoptosis and pterygium in the Korean population showed a gender difference. Epidemiologic evidence only showed a negative correlation between blepharoptosis and pterygium in Korean males. Further studies are needed, therefore, to examine the sex difference in the pathogenesis of pterygium.

Immunophenotypic characterization of telocyte-like cells in pterygium

Purpose

Telocytes (TCs) are peculiar interstitial cells, characterized by their typical elongated and interconnected processes called telopodes. TCs are supposed to contribute to maintain tissue homeostasis but also to be involved in the pathophysiology of many disorders. The aim of the study was to identify TCs in pterygium, a chronic condition of bulbar conjunctiva, and to examine possible differences in TCs in terms of immunophenotype and/or localization between pterygium and normal conjunctiva, to evaluate the possible involvement of TCs in pathogenesis of pterygium.

Methods

The analysis of the immunophenotype of TCs was performed on a group of 40 formalin-fixed and paraffin-embedded primary pterygium and ten bulbar conjunctiva samples. We examined with immunohistochemistry the expression of 11 commercially available antibodies (PDGFRα, CD34, c-kit, nestin, vimentin, α-SMA, laminin, S100, VEGF, CD133, and CD31) and with double immunofluorescence the concomitant expression of PDGFRα and CD34, and PDGFRα and nestin. In addition, we performed an ultrastructural study with transmission electron microscopy (TEM) on a group of five pterygium and three conjunctiva biopsy specimens.

Results

TCs, ultrastructurally identified according to their "moniliform" prolongations, were localized underneath the epithelium along the basement membrane, around the vessels, and near the nerves and scattered in the stroma. In contrast, TCs, as fibroblasts, were almost absent in the fibrotic areas. In pterygium and normal conjunctiva, the TCs shared the same distribution pattern, except a marked TC hyperplasia detected in pterygium. Moreover, in pterygium, the immunohistochemical analysis of TCs showed a strong immunoreactivity to PDGFRα, CD34, and nestin. This result was confirmed with double immunofluorescence labeling, revealing that in pterygium stromal TCs always showed a PDGFRα+/nestin+ and PDGFRα+/CD34+ immunophenotype. Furthermore, moderate staining to vimentin and VEGF was detected, but only a small number of cells were weakly immunoreactive to laminin and S100. Only adventitial TCs of the perivascular sheaths exhibited strong immunoreactivity to α-SMA. Conversely, despite showing mild immunoreactivity to PDGFRα and CD34, the TCs in normal conjunctiva did not show any immunoreactivity to nestin and VEGF. Moreover, in pterygium and conjunctiva, the TCs were always negative for c-kit.

Conclusions

Because of the distribution and immunophenotype, TCs in pterygium may represent a subpopulation of relatively immature cells with regenerative potential. In addition, the expression of nestin may suggest possible involvement of TCs as active players in the regeneration of ultraviolet-damaged stroma and vascular remodeling. The fibrotic transformation in the cicatricial area may stand for a breakdown of the regenerative process.

A novel role for CRIM1 in the corneal response to UV and pterygium development

Pterygium is a pathological proliferative condition of the ocular surface, characterised by formation of a highly vascularised, fibrous tissue arising from the limbus that invades the central cornea leading to visual disturbance and, if untreated, blindness. Whilst chronic ultraviolet (UV) light exposure plays a major role in its pathogenesis, higher susceptibility to pterygium is observed in some families, suggesting a genetic component. In this study, a Northern Irish family affected by pterygium but reporting little direct exposure to UV was identified carrying a missense variant in CRIM1 NM_016441.2: c.1235 A > C (H412P) through whole-exome sequencing and subsequent analysis. CRIM1 is expressed in the developing eye, adult cornea and conjunctiva, having a role in cell differentiation and migration but also in angiogenesis, all processes involved in pterygium formation. We demonstrate elevated CRIM1 expression in pterygium tissue from additional individual Northern Irish patients compared to unaffected conjunctival controls. UV irradiation of HCE-S cells resulted in an increase in ERK phosphorylation and CRIM1 expression, the latter further elevated by the addition of the MEK1/2 inhibitor, U0126. Conversely, siRNA knockdown of CRIM1 led to decreased UV-induced ERK phosphorylation and increased BCL2 expression. Transient expression of the mutant H412P CRIM1 in corneal epithelial HCE-S cells showed that, unlike wild-type CRIM1, it was unable to reduce the cell proliferation, increased ERK phosphorylation and apoptosis induced through a decrease of BCL2 expression levels. We propose here a series of intracellular events where CRIM1 regulation of the ERK pathway prevents UV-induced cell proliferation and may play an important role in the in the pathogenesis of pterygium.

Pyroptosis in pterygium pathogenesis

Pterygium is a common ocular disease characterized by proliferating fibrovascular tissue. Pyroptosis, a recently discovered programed cell death, is known to be associated with oxidative stress, one of the main causes of pterygia. Here, we aimed to study the role of pyroptosis in pterygium pathogenesis. The expression of nod-like receptor pyrins-3 (NLRP3), caspase-1, IL-18, and IL-1β was analyzed in 60 human pterygium tissues and 60 human conjunctival epithelium tissues using real-time quantitative polymerase chain reaction (qRT-PCR) and Western blot analysis. Human conjunctival epithelial cells (HConECs) and human pterygium fibroblasts (HPFs) were primary cultured and the level of pyroptosis-associated factors was detected. Both cells were treated with H₂O₂, and cell lysis was detected by lactate dehydrogenase (LDH) release assay, the expression of the factors by qRT-PCR, Western blot analysis, and immunostaining. The downstream factors IL-18 and IL-1β were measured after inhibition of caspase-1 to confirm the caspase-1-dependent pyroptosis. α-SMA and E-cadherin were detected as indicators of pyroptosis-induced myofibroblast activation in HPFs. We discovered that the expression of the factors was significantly increased in pterygium and that caspase-1-dependent pyroptosis presents in both H₂O₂-treated HPFs and HConECs during which the expression of these factors was significantly elevated and the elevation of downstream factors IL-18 and IL-1β was restrained after caspase-1 inhibition. α-SMA increase and E-cadherin down-regulation were detected in H₂O₂-treated HPFs and the changes were reversed by caspase-1 inhibition. Pyroptosis displays a role in the pathological process of pterygium formation and progression. Pyroptosis appears to be an intriguing target to prevent pterygium pathogenesis.

MicroRNA regulation of MDM2-p53 loop in pterygium

PURPOSE

The pathogenesis of pterygium has been linked to limbal stem cell damage, abnormal apoptosis and cellular proliferation. In this study, we investigated the epigenetic regulation through microRNA expression in the pathogenesis of pterygium.

METHODS

Human full-length primary pterygia were microdissected into head and body regions. Specific microRNA and mRNA expression was assayed by TaqMan^® real-time quantitative polymerase chain reaction (qPCR). Tissue localization of target microRNAs was performed by LNA-based in situ hybridization. MicroRNA-145 (miR-145) mimics were transfected to primary culture of human pterygial cells, followed by analyses of cell cycle changes, apoptosis, p53 and MDM2 expression using flow cytometry and qPCR.

RESULTS

The expression of miR-145 was markedly higher in primary human pterygium than in limbus and conjunctiva. Both miR-143 and miR-145 were predominantly expressed in the basal pterygial epithelium. Oncogene MDM2 expression was abundant in pterygial epithelium and stroma, while the expression pattern was opposite to that of miR-145. Ectopic expression of miR-145 in pterygial cells induced G1 arrest, down-regulated MDM2 and elevated p53 expression.

CONCLUSIONS

Our study showed that miR-145 suppressed MDM2 expression, which subsequently influenced the p53-related cell growth pattern in pterygial epithelium. The regulatory miR-145/MDM2-p53 loop can serve as a potential target for treatment of pterygium.

Local pro-inflammatory cytokine and nitric oxide responses are elevated in patients with pterygium

Pterygium is a common ocular surface disease observed in humans. Chronic ultraviolet (UV) exposure is extensively recognized as an aetiological factor in the pathogenesis of this disease. This hypothesis is sustained by epidemiological and histopathological data in relation to UV injured skin. Although some findings have indicated that genetic factors, anti-apoptotic and immunological mechanisms are involved in the pathogenesis of pterygium, the mechanism by which it develops remains poorly understood. In this study, we analysed the in vivo production of IL-17A, IL-6, IL-10 and nitric oxide (NO) in the tears and sera from Algerian patients. Interestingly, we observed that IL-6, IL-17A and NO production in the tears and sera of all patients was strongly associated with inflammatory infiltration, NOS2, NF-κB and Bcl2 expression in pterygia biopsies. Collectively, our results indicate a relationship between local inflammation and anti-apoptotic processes in pterygium disease, leading to both tissue damage and enhanced cellular proliferation.

Myofibroblast transdifferentiation: The dark force in ocular wound healing and fibrosis

Wound healing is one of the most complex biological processes to occur in life. Repair of tissue following injury involves dynamic interactions between multiple cell types, growth factors, inflammatory mediators and components of the extracellular matrix (ECM). Aberrant and uncontrolled wound healing leads to a non-functional mass of fibrotic tissue. In the eye, fibrotic disease disrupts the normally transparent ocular tissues resulting in irreversible loss of vision. A common feature in fibrotic eye disease is the transdifferentiation of cells into myofibroblasts that can occur through a process known as epithelial-mesenchymal transition (EMT). Myofibroblasts rapidly produce excessive amounts of ECM and exert tractional forces across the ECM, resulting in the distortion of tissue architecture. Transforming growth factor-beta (TGFβ) plays a major role in myofibroblast transdifferentiation and has been implicated in numerous fibrotic eye diseases including corneal opacification, pterygium, anterior subcapsular cataract, posterior capsular opacification, proliferative vitreoretinopathy, fibrovascular membrane formation associated with proliferative diabetic retinopathy, submacular fibrosis, glaucoma and orbital fibrosis. This review serves to introduce the pathological functions of the myofibroblast in fibrotic eye disease. We also highlight recent developments in elucidating the multiple signaling pathways involved in fibrogenesis that may be exploited in the development of novel anti-fibrotic therapies to reduce ocular morbidity due to scarring.

Inhibitory effects of rosmarinic acid on pterygium epithelial cells through redox imbalance and induction of extrinsic and intrinsic apoptosis

Pterygium is a common tumor-like ocular disease, which may be related to exposure to chronic ultraviolet (UV) radiation. Although the standard treatment for pterygium is surgical intervention, the recurrence rate of pterygium is high when no effective inhibitory drug is used after surgery. Rosmarinic acid (RA) is a polyphenol antioxidant with many biological activities, including anti-UV and anti-tumor properties. This study aimed to examine the inhibitory effects of RA on pterygium epithelial cells (PECs). Methylthiazolyldiphenyl-tetrazolium bromide (MTT) assay was used to examine the cell cytotoxicity of PECs after RA treatment. A fluorescent probe, DCFH-DA (2',7'-dichlorofluorescin diacetate), was stained with PECs to measure intracellular reactive oxygen species (ROS) levels. Antioxidant activity assays were used to measure the levels of superoxide dismutase (SOD) and catalase (CAT) in PECs. Western blot analysis was used to determine the protein expression of nuclear factor E2-related factor 2 (Nrf2), heme oxygenase 1 (HO-1), quinone acceptor oxidoreductase 1 (NQO1), and apoptosis-associated proteins. RA significantly reduced the cell viability of the PECs. Treatment with RA remarkably increased the Nrf2 protein expression levels in the nucleus, HO-1 and NQO1 protein expression levels, and the activities of SOD and CAT. As a result, intracellular ROS levels in PECs were decreased. Additionally, the induction of extrinsic apoptosis on PECs by RA was associated with increasing expressions levels of Fas, Fas-associated protein with death domain (FADD), tumor necrosis factor-alpha (TNF-α), and caspase 8 protein. Moreover, the induction of intrinsic apoptotic cell death in PECs was confirmed through upregulation of cytochrome c, Bax, caspase 9, and caspase 3 and downregulation of Bcl-2 and pro-caspase 3. Our study demonstrated that RA could inhibit the viability of PECs through regulation of extrinsic and intrinsic apoptosis pathways. Therefore, RA may have potential as a therapeutic medication for pterygium.

Aberrant expression of genes and proteins in pterygium and their implications in the pathogenesis

Pterygium is a common ocular surface disease induced by a variety of factors. The exact pathogenesis of pterygium remains unclear. Numbers of genes and proteins are discovered in pterygium and they function differently in the occurrence and development of this disease. We searched the Web of Science and PubMed throughout history for literatures about the subject. The keywords we used contain pterygium, gene, protein, angiogenesis, fibrosis, proliferation, inflammation, pathogenesis and therapy. In this review, we summarize the aberrant expression of a range of genes and proteins in pterygium compared with normal conjunctiva or cornea, including growth factors, matrix metalloproteinases and tissue inhibitors of metalloproteinases, interleukins, tumor suppressor genes, proliferation related proteins, apoptosis related proteins, cell adhesion molecules, extracellular matrix proteins, heat shock proteins and tight junction proteins. We illustrate their possible mechanisms in the pathogenesis of pterygium as well as the related intervention based on them for pterygium therapy.

Curcuma longa Is Able to Induce Apoptotic Cell Death of Pterygium-Derived Human Keratinocytes

Pterygium is a relatively common eye disease that can display an aggressive clinical behaviour. To evaluate the in vitro effects of Curcuma longa on human pterygium-derived keratinocytes, specimens of pterygium from 20 patients undergoing pterygium surgical excision were collected. Pterygium explants were put into culture and derived keratinocytes were treated with an alcoholic extract of 1.3% Curcuma longa in 0.001% Benzalkonium Chloride for 3, 6, and 24 h. Cultured cells were examined for CAM5.2 (anti-cytokeratin antibody) and CD140 (anti-fibroblast transmembrane glycoprotein antibody) expression between 3th and 16th passage to assess cell homogeneity. TUNEL technique and Annexin-V/PI staining in flow cytometry were used to detect keratinocyte apoptosis. We showed that Curcuma longa exerts a proapoptotic effect on pterygium-derived keratinocytes already after 3 h treatment. Moreover, after 24 h treatment, Curcuma longa induces a significant increase in TUNEL as well as Annexin-V/PI positive cells in comparison to untreated samples. Our study confirms previous observations highlighting the expression, in pterygium keratinocytes, of nuclear VEGF and gives evidence for the first time to the expression of nuclear and cytoplasmic VEGF-R1. All in all, these findings suggest that Curcuma longa could have some therapeutic potential in the treatment and prevention of human pterygium.

Association between pterygium and obesity status in a South Korean population

This study examined the association between pterygium and obesity status by examining a nationally representative sample of South Korean adults.This population-based, cross-sectional study comprised 16,234 adults (aged ≥19 years) who had participated in the fifth annual Korea National Health and Nutrition Examination Survey from 2010 to 2012. The enrolled subjects underwent interviews, clinical examinations, and laboratory investigations. We compared body mass index (BMI) and waist circumference (WC), according to the presence of pterygium. Multiple logistic regression analysis was conducted to examine the associations of each obesity parameter with pterygium after adjusting for age, smoking status, alcohol consumption, physical activities, educational levels, outdoor occupation, area of residence, and daily sun exposure duration.The prevalence rate of pterygium tended to increase as the BMI increased only in women, and both male and female subjects with higher WC were likely to have more pterygium in both sexes. In the multivariate analysis, overweight women had an odd ratio (OR) (95% confidence interval (CI)) of 1.16 (0.86-1.55) and obese women had an OR (95% CI) of 1.35 (1.02-1.77) compared to women with normal weight (P for trend for ORs = 0.04). Compared to women without abdominal obesity, abdominally obese women had an OR (95% CI) of 1.26 (1.01-1.58). There was no significant association between obesity and pterygium in men.The present study provides epidemiologic evidence of an association between obesity and pterygium in women. Further studies are needed to examine the sex difference in the pathogenesis of pterygium.

K-ras oncogene mutation in pterygium

PurposePterygium is claimed to be a benign proliferation triggered by prolonged exposure to ultraviolet radiation. The frequency of K-ras oncogene mutation, which is among the initial mutations in tumorigenesis, is evaluated in this study.Patients and methodsIn this prospective randomized clinical, trial pterygium tissues and normal conjunctiva tissue specimens are obtained from the superotemporal quadrant of patients who underwent primary pterygium excision with autograft transplantation. DNA extraction from tissues was performed using the QIAamp DNA FFPE tissue kit. A PCR reaction was performed to amplify sequences containing codons 12, 13, and 61 of the K-ras gene in DNA. These PCR products then underwent the 'pyrosequencing' procedure for mutations at these codons.ResultsPterygium and normal conjunctival tissue samples of 25 patients (10 females, 15 males) were evaluated in the study. The mean age of the patients was 54.54±13.13 years. Genetic analysis revealed no K-ras mutations in normal conjunctival tissues, whereas pterygium tissues of the same cases demonstrated mutation at codon 12 in one case and mutations at codon 61 in seven cases, which was statistically significant (P<0.05). The point missense mutations at codon 61 were glutamine to arginine (Glu61Arg CAA>CGA) in four cases and glutamine to leucine (Glu61Leu CAA>CTA) in three cases.ConclusionThe significantly higher frequency of codon 61 mutation of the ras oncogene in primary and bilateral pterygium specimens compared with normal conjunctiva supports the tumoral origin of pterygium, and thus set the stage for research into a targeted therapy for pterygium with better outcomes than surgical excision.

The role of ultraviolet radiation in the pathogenesis of pterygia (Review)

Pterygium is a common ophthalmic disease affecting humans only. Extensive epidemiological data have demonstrated a causative effect of chronic ultraviolet (UV) radiation on pterygia. Progress has been made in determining the origin of pterygia, their nasal predilection and wing‑shaped appearance, and the roles of UV radiation in the initiation and the development of pterygia. In the present review, the current understanding of the involvement of UV radiation in the pathogenesis of pterygia is summarized. This involvement includes the alteration of limbal stem cells and fibroblasts that contribute to the initiation of pterygia and the induction of various pro‑inflammatory cytokines, growth factors and matrix metalloproteinases that promote the progression of pterygia. Further elucidation of the roles of UV radiation in the pathogenesis of pterygia may help to encourage individuals at risk of developing pterygia to take preventive measures and aid researchers in the development of novel targeted therapeutic agents to treat pterygia.

Transplantation of Autologous Ex Vivo Expanded Human Conjunctival Epithelial Cells for Treatment of Pterygia: A Prospective Open-label Single Arm Multicentric Clinical Trial

Purpose:

To establish the efficacy and safety of ex vivo cultured autologous human conjunctival epithelial cell (hCjEC) transplantation for treatment of pterygia.

Methods:

Twenty-five patients with pterygia were recruited at different centers across the country. Autologous hCjEC grafts were prepared from conjunctival biopsy specimens excised from the healthy eye and cultured ex vivo on human amniotic membrane mounted on inserts using a unique mounting device. The hCjEC grafts were then transported in an in-house designed transport container for transplantation. Post-surgery, the patients were followed up on days 1, 7, 14, 30, 90, and 180 as per the approved study protocol. Clinical outcomes were assessed by slit lamp examination, visual acuity, imprint cytology, fluorescein/rose bengal staining, Schirmer's test, and photographic evaluation three and 6 months post-transplantation.

Results:

Two patients were lost to follow-up and final analysis included 23 cases. No recurrence of pterygium was observed in 18 (78.3%) patients; all of these eyes showed a smooth conjunctival surface without epithelial defects. Recurrence was observed in 5 (21.7%) patients at 3 months post-treatment. No conjunctival inflammation, secondary infections or other complications were reported. Adequate goblet cells were present in 19 (82.6%) patients at the site of transplantation.

Conclusion:

We have, for the 1^st time, standardized a protocol for preparing autologous hCjEC grafts that can be safely transported to multiple centers across the country for transplantation. The clinical outcome was satisfactory for treating pterygia.

Molecular Basis of Pterygium Development

Pterygium pathogenesis is mainly related to UV light exposure. However, the exact mechanisms by which it is formed have not been elucidated. Clinical advances in surgical treatment use conjunctival autografts and amniotic membranes in combination with adjuvant therapies, including mitomycin C, β-radiation, and 5-fluoroacil, to reduce recurrence. Several studies aim to unveil the molecular mechanisms underlying pterygium growth and proliferation. They demonstrate the role of different factors, such as viruses, oxidative stress, DNA methylation, apoptotic and oncogenic proteins, loss of heterozygosity, microsatellite instability, inflammatory mediators, extracellular matrix modulators, lymphangiogenesis, cell epithelial-mesenchymal transition, and alterations in cholesterol metabolism in pterygium development. Understanding the molecular basis of pterygium provides new potential therapeutic targets for its prevention and elimination. This review focuses on providing a broad overview of what is currently known regarding molecular mechanisms of pterygium pathogenesis.

Prevalence and viral load of oncogenic human papillomavirus (HPV) in pterygia in multi-ethnic patients in the Malay Peninsula

PURPOSE

The aim of the study was to determine the prevalence of human papillomavirus (HPV) in primary and recurrent pterygia samples collected from different ethnic groups in the equatorial Malay Peninsula.

METHODS

DNA was extracted from 45 specimens of freshly obtained primary and recurrent pterygia from patients and from 11 normal conjunctival swabs from volunteers with no ocular surface lesion as control. The presence of HPV DNA was detected by nested PCR. PCR-positive samples were subjected to DNA sequencing to determine the HPV genotypes. Real-time PCR with HPV16 and HPV18 type-specific TaqMan probes was employed to determine the viral DNA copy number.

RESULTS

Of 45 pterygia samples with acceptable DNA quality, 29 (64.4%) were positive for HPV DNA, whereas all the normal conjunctiva swabs were HPV negative. Type 18 was the most prevalent (41.4% of positive samples) genotype followed by type 16 (27.6%). There was one case each of the less common HPV58 and HPV59. Seven of the samples harboured mixed infections of both HPV16 and HPV18. All the four known recurrent pterygia samples were HPV-positive, whereas the sole early-stage pterygium sample in the study was HPV-negative. There was no significant association between HPV-positive status with gender or age. A high proportion of patients from the Indian ethnic group (five of six) were HPV-positive, whereas the Malay patients were found to have higher HPV positivity than the Chinese. The viral load of HPV18 samples ranged between 2 × 10(2) and 3 × 10(4) copies per μg, whereas the viral load of HPV16 specimen was 4 × 10(1) to 10(2) copies per μg.

CONCLUSION

This report describes for the first time the quantitative measurement of HPV viral DNA for pterygium samples. The high prevalence of oncogenic HPVs in our samples suggests a possible role for HPV in the pathogenesis of pterygia. Moreover, the relatively low HPV viral load is concordant with the premalignant nature of this ocular condition.

Proteomic analysis in pterygium; upregulated protein expression of ALDH3A1, PDIA3, and PRDX2

PURPOSE

To identify differentially expressed proteins in the pterygium compared to healthy conjunctiva using a proteomic analysis.

METHODS

Pterygial and healthy conjunctival tissues were obtained from 24 patients undergoing pterygium excision. Total proteins of the pterygia and healthy conjunctiva were analyzed with one-dimensional electrophoresis, and protein bands of interest were excised and subjected to liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-MS/MS) using Thermo's Finnigan ProteomeX workstation LTQ linear ion trap MS/MS. Using bioinformatics, differentially expressed proteins were classified, and three proteins closely involved in the response to oxidative stress were selected for further validation. Differential expression of these proteins was confirmed with western blot and immunohistochemistry.

RESULTS

A web-based gene ontology program, DAVID, was used to classify 230 proteins that were differentially expressed in pterygial tissues. Among these genes, we chose three proteins, aldehyde dehydrogenase, dimeric NADP-preferring (ALDH3A1), protein disulfide-isomerase A3 (PDIA3), and peroxiredoxin-2 (PRDX2), that were significantly upregulated in pterygium and further increased in recurrent pterygium. Immunohistochemistry and western blot analysis confirmed that these three proteins were mainly detected in the basal epithelial layer, and their expression was significantly increased in the pterygium compared to normal conjunctiva.

CONCLUSIONS

This study reported increased expression of ALDH3A1, PDIA3, and PRDX2 in pterygia using a proteomic approach. These proteins are presumed to have a protective role against oxidative stress-induced apoptosis. This result is consistent with the hypothesis that oxidative stress is a significant factor in the pathogenesis of pterygia.

Angiotensin II: immunohistochemical study in Sardinian pterygium

The Angiotensin II (Ang II) is the principal effector peptide of the RAS system. It has a pleiotropic effect and, beside its physiological role, it has the property to stimulate angiogenesis and activate multiple signalling pathways related to cell proliferation. The purpose of the study was to determinate the Ang II expression and localization in Sardinian pterygium and normal conjunctiva by immunohistochemistry, and its possible involvement in the development and progression of the disease. Twenty-three pterygiums and eleven normal conjunctiva specimens obtained from Sardinian patients, were processed for paraffin embedding and assessed for the immunohistochemi-cal revelation of Ang II. Significant Ang II expression was identified in pterygium and conjunctiva. Particularly, thirteen pterygium specimens (n=13) displayed exclusively moderate to strong nuclear staining; some specimens (n=5) showed exclusively a moderate cytoplasmic immunoreactivity, and few specimens (n=2) displayed moderate to strong immunoreactivity in both cytoplasm and nucleus. Only 3 specimens were negative. Statistical significance difference in respect of nuclear and cytoplasmic localization was observed between normal conjunctiva and pterygium (P=0.020). The results showed a predominant intranuclear localization of Ang II in pterygium epithelial cells, in spite of conjunctiva that mainly showed cytoplasmic localization. These findings suggest a possible role for Ang II in the development and/or progression of pterygium mediated by the activation of local RAS system.