Progress in the pathogenesis of pterygium

Expression of CD44, PCNA and E-cadherin in pterygium tissues

PURPOSE

Pterygium is a common ocular surface disease defined by fibrovascular conjunctival growth extending onto the cornea. However, its pathogenesis remains unclear. This study aimed to determine the role of CD44, proliferating cell nuclear antigen (PCNA), and E-cadherin in pterygium formation and recurrence.

METHODS

Sixty patients with pterygium participated in the study, and we collected conjunctival samples from 30 patients to form a control group. CD44, PCNA, and E-cadherin expressions in surgically excised pterygium were compared with tissue samples from the control group.

RESULTS

We observed that the percentages of CD44 and PCNA were statistically higher in the primary pterygium group and recurrent pterygium group than in the control group (P < 0.001 and P < 0.001, respectively). Conversely, E-cadherin values were statistically higher in the control group than in the primary and recurrent pterygium groups (P = 0.013 and P < 0.001, respectively).

CONCLUSION

Cell proliferation and cell adhesion factors may play important roles in the pathogenesis of pterygium.

Single-cell RNA sequencing reveals the complex cellular niche of pterygium

PURPOSE

Pterygium is a vision-threatening conjunctival fibrovascular degenerated disease with a high global prevalence up to 12 %, while no absolute pharmacotherapy has been applied in clinics. In virtue of single-cell RNA sequencing (scRNA-seq) technique, our study investigated underlying pathogeneses and potential therapeutic targets of pterygium from the cellular transcriptional level.

METHODS

A total of 45605 cells from pterygium of patients and conjunctiva of normal controls (NC) were conducted with scRNA-seq, and then analyzed via integrated analysis, pathway enrichment, pseudotime trajectory, and cell-cell communications. Besides, immunofluorescence and western blot were performed in vivo and in vitro to verify our findings.

RESULTS

In brief, 9 major cellular types were defined, according to canonical markers. Subsequently, we further determined the subgroups of each major cell lineages. Several newly identified cell sub-clusters could promote pterygium, including immuno-fibroblasts, epithelial mesenchymal transition (EMT)-epithelial cells, and activated vascular endothelial cells (activated-vEndo). Besides, we also probed the enrichment of immune cells in pterygium. Particularly, macrophages, recruited by ACKR1+activated-vEndo, might play an important role in the development of pterygium by promoting angiogenesis, immune suppression, and inflammation.

CONCLUSION

An intricate cellular niche was revealed in pterygium via scRNA-seq analysis and the interactions between macrophages and ACKR1+ activated-vEndo might be the key part in the development of pterygia.

Are Periocular and Systemic Allergy Conditions Risk Factors for Pterygium?

PURPOSE

To evaluate risk factors for pterygium and prevalence of periocular and systemic diseases among patients with pterygium.

METHODS

A retrospective case-control study was conducted among members of Clalit Health Services (CHS) in Israel, from 2001 to 2022. A total of 13,944 patients diagnosed with pterygium were included. For each case, three controls were matched among all CHS patients according to year of birth, sex, and ethnicity. Mixed models were used to assess differences in demographic characteristics, ocular and systemic diseases between the groups. Generalized estimating equation (GEE) logistic regression was used to estimate the odds ratios (OR) and adjust for confounders.

RESULTS

The average age of pterygium patients was 49 ± 17 years; 51% were male. The results showed significant associations between pterygium and risk factors of vernal kerato-conjunctivitis (OR 2.52, 95% confidence interval [CI]: [1.96-3.24]), chronic allergic conjunctivitis (OR 1.98, 95% CI: [1.65-2.39]), blepharitis (OR 1.91, 95% CI: [1.78-2.04]), chalazion (OR 1.47, 95% CI: [1.30-1.67]) and unspecified systemic allergy (OR 1.21, 95% CI [1.09-1.34]), after adjusting for rural residency status. Glaucoma (OR 0.74, 95% CI [0.64-0.85]) and smoking (OR 0.70, 95% CI [0.66-0.75]) were protective factors against pterygium.

CONCLUSION

Systemic and periocular inflammatory and allergic diseases are risk factors for pterygium.

Up-to-date molecular medicine strategies for management of ocular surface neovascularization

Ocular surface neovascularization and its resulting pathological changes significantly alter corneal refraction and obstruct the light path to the retina, and hence is a major cause of vision loss. Various factors such as infection, irritation, trauma, dry eye, and ocular surface surgery trigger neovascularization via angiogenesis and lymphangiogenesis dependent on VEGF-related and alternative mechanisms. Recent advances in antiangiogenic drugs, nanotechnology, gene therapy, surgical equipment and techniques, animal models, and drug delivery strategies have provided a range of novel therapeutic options for the treatment of ocular surface neovascularization. In this review article, we comprehensively discuss the etiology and mechanisms of corneal neovascularization and other types of ocular surface neovascularization, as well as emerging animal models and drug delivery strategies that facilitate its management.

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.

Impact of pterygium on central corneal thickness measured by optical coherence tomography in older adults

PURPOSE

To measure the central corneal thickness (CCT) using anterior segment optical coherence tomography (AS-OCT) in older adults with and without pterygium from the Brazilian Amazon Region Eye Survey (BARES).

METHODS

BARES is a population-based epidemiological cross-sectional study conducted in Parintins city. Participants were residents ≥45 years of age identified through a door-to-door interview. Eligible participants were invited for a comprehensive eye exam. Pterygium occurrence and severity were assessed by ophthalmologists through slit-lamp examination considering its location (nasal or/and temporal) and severity (lesion with extension <3 mm, ≥3 mm not reaching the pupillary margin or ≥3 mm reaching the pupillary margin). CCTs were obtained and measurements from the more severely affected eye were included. Images were analyzed offline by masked observers.

RESULTS

A total of 671 subjects, 533 (79.4%) with pterygium in at least one eye and 138 (20.6%) without pterygium in either eye, were examined. The mean CCT evaluated by multiple linear regression and adjusted for demographic variables and pterygium severity was 521 ± 34 μm (median = 521; range = 304-665). Decreased CCT was significantly associated with age and pterygium severity. Individuals aged 65-74 years had CCT 7 μm thinner than those aged 45-54 years (p = 0.044), individuals aged 75 years and older had CCT 15 μm thinner than those aged 45-54 years (p = 0.001), and eyes with severe pterygium had CCT 33 μm thinner than eyes without pterygium (p < 0.001).

CONCLUSIONS

The CCT analysis in this population-based sample shows that a thinner cornea is associated with pterygium severity and older age.

Oxidative Stress in the Anterior Ocular Diseases: Diagnostic and Treatment

The eye is a metabolically active structure, constantly exposed to solar radiations making its structure vulnerable to the high burden of reactive oxygen species (ROS), presenting many molecular interactions. The biomolecular cascade modification is caused especially in diseases of the ocular surface, cornea, conjunctiva, uvea, and lens. In fact, the injury in the anterior segment of the eye takes its origin from the perturbation of the pro-oxidant/antioxidant balance and leads to increased oxidative damage, especially when the first line of antioxidant defence weakens with age. Furthermore, oxidative stress is related to mitochondrial dysfunction, DNA damage, lipid peroxidation, protein modification, apoptosis, and inflammation, which are involved in anterior ocular disease progression such as dry eye, keratoconus, uveitis, and cataract. The different pathologies are interconnected through various mechanisms such as inflammation, oxidative stress making the diagnostics more relevant in early stages. The end point of the molecular pathway is the release of different antioxidant biomarkers offering the potential of predictive diagnostics of the pathology. In this review, we have analysed the oxidative stress and inflammatory processes in the front of the eye to provide a better understanding of the pathomechanism, the importance of biomarkers for the diagnosis of eye diseases, and the recent treatment of anterior ocular diseases.

Identification of the circRNA-miRNA-mRNA Regulatory Network in Pterygium-Associated Conjunctival Epithelium

To investigate the regulatory mechanism of pterygium formation, we detected differentially expressed messenger RNAs (DE-mRNAs) and differentially expressed circular RNAs (DE-circRNAs) in pterygium-associated conjunctival epithelium (PCE) and normal conjunctival epithelium (NCE). Genome-wide mRNA and circRNA expression profiles of PCE and NCE were determined using high-throughput sequencing. Bioinformatics analyses, including Gene Ontology (GO) analysis, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis, gene set enrichment analysis (GSEA), and protein-protein interaction (PPI) analysis, were conducted. The microRNAs (miRNAs) interacting with the hub DE-mRNAs and DE-circRNAs were predicted and verified using real-time quantitative PCR (RT-qPCR). The data showed that there were 536 DE-mRNAs (280 upregulated and 256 downregulated mRNAs) and 78 DE-circRNAs (20 upregulated and 58 downregulated circRNAs) in PCE. KEGG enrichment analysis indicated that the DE-mRNAs were mainly involved in the following biological processes: IL-17 signalling pathway, viral protein interaction with cytokine and cytokine receptor, cytokine-cytokine receptor interaction, ECM-receptor interaction, and focal adhesion. The GSEA results revealed that the epithelial mesenchymal transition (EMT) process was significantly enriched in upregulated mRNAs. The pterygium-associated circRNA-miRNA-mRNA network was established based on the top 10 DE-circRNAs, 4 validated miRNAs (upregulated miR-376a-5p and miR-208a-5p,downregulated miR-203a-3p and miR-200b-3p), and 31 DE-mRNAs. We found that miR-200b-3p, as a regulator of FN1, SDC2, and MEX3D, could be regulated by 5 upregulated circRNAs. In addition, we screened out EMT-related DE-mRNAs, including 6 upregulated DE-mRNAs and 6 downregulated DE-mRNAs. The EMT-related circRNA-miRNA-mRNA network was established with the top 10 circRNAs, 8 validated miRNAs (upregulated miR-17-5p, miR-181a-5p, and miR-106a-5p, downregulated miR-124-3p, miR-9-5p, miR-130b-5p, miR-1-3p, and miR-26b-5P), and 12 EMT-related DE-mRNAs. We found that hsa_circ_0002406 might upregulate FN1 and ADAM12 by sponging miR-26b-5p and miR-1-3p, respectively, thus promoting EMT in pterygium. Briefly, the study provides a novel viewpoint on the molecular pathological mechanisms in pterygium formation. CircRNA-miRNA-mRNA regulatory networks participate in the pathogenesis of pterygium and might become promising targets for pterygium prevention and treatment.

Fibroblast Growth Factor-2 (FGF-2) Expression in Pterygia Using Cell Spot Arrays

Fibroblast growth factor (FGF) is a main regulator of cell differentiation, cell migration and angiogenesis in normal and abnormal conjunctiva epithelia, but specific mechanisms of its aberrant expression are yet to be investigated. In the present study, we investigated FGF-2 protein expression within several pterygia. Using a liquid-based cytology assay, we obtained cell specimens from pterygia and healthy tissues directly from patients. A combination of immunocytochemistry followed by digital image analysis showed significant overexpression of FGF-2 in all the examined pterygia. In 30/60 (50%) cases there were high levels of staining intensity, whereas in the remaining 30/60 (50%) cases there were moderate levels of expression. FGF-2 levels of the control group were significantly lower in comparison with the pterygia group. There was no significant correlation between FGF-2 levels and either sex or location of the pterygium. FGF-2 levels had a significant correlation with morphological characteristics of the pterygia. More specifically, FGF-2 levels were significantly higher in the pterygia with a fleshy morphology. Interestingly, recurrent lesions demonstrated high expression levels. An overexpression of FGF-2 has been observed frequently in pterygia, where it may play a crucial role in determining the lesion’s progression. FGF-2 upregulation correlates with the morphology of pterygia and its tendency to recur. Cell spot analysis based on liquid-based cytology is a simple, yet effective, method for detecting a broad spectrum of protein markers and could be useful in analyzing potential pterygia patient samples.

The association of sun exposure, ultraviolet radiation effects and other risk factors for pterygium (the SURE RISK for pterygium study) in geographically diverse adult (≥40 years) rural populations of India -3rd report of the ICMR-EYE SEE study group

Purpose

To determine the prevalence and risk factors for pterygium in geographically diverse regions of India.

Methods

A population-based, cross-sectional multicentric study was conducted in adults aged ≥40 years in plains, hilly and coastal regions of India. All participants underwent a detailed questionnaire-based assessment for sun exposure, usage of sun protective measures, exposure to indoor smoke, and smoking. Detailed ocular and systemic examinations were performed. Pterygium was diagnosed and graded clinically by slit-lamp examination. Association of pterygium with sociodemographic, ophthalmological, and systemic parameters was assessed. Physical environmental parameters for the study period were estimated.

Results

Of the 12,021 eligible subjects, 9735 (81% response rate) participated in the study. The prevalence of pterygium in any eye was 13.2% (95% CI: 12.5%-13.9%), and bilateral pterygium was 6.7% (95% CI: 6.2–7.2). The prevalence increased with age (<0.001) irrespective of sex and was highest in those aged 60–69 years (15.8%). The prevalence was highest in coastal (20.3%), followed by plains (11.2%) and hilly regions (9.1%). On multi-logistic regression, pterygium was positively associated with coastal location (P<0.001), illiteracy (P = 0.037), increasing lifetime sun exposure (P<0.001), and negatively associated with BMI ≥25 kg/m2 (P = 0.009).

Conclusion

Pterygium prevalence is high in the rural Indian population. The association of pterygium with several potentially modifiable risk factors reflects its multifactorial etiology and provides targets for preventive measures.

Host Defense Peptides at the Ocular Surface: Roles in Health and Major Diseases, and Therapeutic Potentials

Sight is arguably the most important sense in human. Being constantly exposed to the environmental stress, irritants and pathogens, the ocular surface – a specialized functional and anatomical unit composed of tear film, conjunctival and corneal epithelium, lacrimal glands, meibomian glands, and nasolacrimal drainage apparatus – serves as a crucial front-line defense of the eye. Host defense peptides (HDPs), also known as antimicrobial peptides, are evolutionarily conserved molecular components of innate immunity that are found in all classes of life. Since the first discovery of lysozyme in 1922, a wide range of HDPs have been identified at the ocular surface. In addition to their antimicrobial activity, HDPs are increasingly recognized for their wide array of biological functions, including anti-biofilm, immunomodulation, wound healing, and anti-cancer properties. In this review, we provide an updated review on: (1) spectrum and expression of HDPs at the ocular surface; (2) participation of HDPs in ocular surface diseases/conditions such as infectious keratitis, conjunctivitis, dry eye disease, keratoconus, allergic eye disease, rosacea keratitis, and post-ocular surgery; (3) HDPs that are currently in the development pipeline for treatment of ocular diseases and infections; and (4) future potential of HDP-based clinical pharmacotherapy for ocular diseases.

Biomarkers in the Occurrence and Development of Pterygium

Pterygium is a kind of common conjunctival degeneration. The pathogenesis of pterygium is complex, and various biomarkers provide new targets for treatment and prognosis. Currently, the most common treatment for pterygium is surgical excision, but it is invasive risk and has a high recurrence rate. Since the development of sequencing, gene chip technology, and proteomics technologies has been rapid, research on the internal mechanism of disease has been facilitated. This review focuses on recent advances in the discovery of biomarkers from the fields of genetics, proteomics, and epigenetics and their likely functional mechanisms and clinical applications 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.

A novel lncRNA lnc-PPRL promotes pterygium development by activating PI3K/PDK1 signaling pathway

A sight threatening, pterygium is a common proliferative and degenerative disease of the ocular surface. LncRNAs have been widely studied in the occurrence and development of various diseases, however, the study of lncRNAs in pterygium has just relatively lacking. In the present study, we performed the high-throughput RNA sequencing (HTS) technology to identify differentially expressed lncRNAs in pterygium. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses were carried out to forecast the regulatory and functional role of lncRNAs in pterygium. Notably, we identified a novel lncRNA, LOC102724238, which we named pterygium positively-related lncRNA (lnc-PPRL), was up-regulated in pterygium. Lnc-PPRL showed to be preferentially accumulated in cytoplasm, and it can promote cell proliferation, migration and invasion of human pterygium epithelium cells (hPECs). Further study of underlying mechanisms demonstrated that lnc-PPRL may exert its biological effect by activating canonical PI3K/PDK1 pathway, and subsequently promoting the activation of Akt/mTOR signaling pathway and its downstream effectors. Interestingly, lnc-PPRL was also proved to influence YAP nuclear localization. Taken together, our study firstly suggested that the "big molecule" lnc-PPRL have potential as a novel therapeutic target for the prevention and treatment of pterygium.

Expression profiling suggests the involvement of hormone-related, metabolic, and Wnt signaling pathways in pterygium progression

BACKGROUND

Pterygium is an ocular surface disease that can cause visual impairment if it progressively invades the cornea. Although many pieces of research showed ultraviolet radiation is a trigger of pterygium pathological progress, the underlying mechanism in pterygium remains indistinct.

METHODS

In this study, we used microarray to evaluate the changes of transcripts between primary pterygium and adjacent normal conjunctiva samples in China. Then, we performed Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) functional enrichment analyses. Moreover, we constructed protein-protein interaction (PPI) and miRNA-mRNA regulatory networks to predict possible regulatory relationships. We next performed gene set enrichment analysis (GSEA) to explore the similarities and differences of transcripts between Asian studies from the Gene Expression Omnibus database. Furthermore, we took the intersection of differentially expressed genes (DEGs) with other data and identified hub genes of the development of pterygium. Finally, we utilized real-time quantitative PCR to verify the expression levels of candidate genes.

RESULTS

A total of 49 DEGs were identified. The enrichment analyses of DEGs showed that pathways such as the Wnt-signaling pathway and metabolism-related pathways were upregulated, while pathways such as hormone-related and transcription factor-associated pathways were downregulated. The PPI and miRNA-mRNA regulatory networks provide ideas for future research directions. The GSEA of selecting Asian data revealed that epithelial-mesenchymal transition and myogenesis existed in the pathology of pterygium in the Asian group. Furthermore, five gene sets (interferon-gamma response, Wnt beta-catenin signaling, oxidative phosphorylation, DNA repair, and MYC targets v2) were found only in our Chinese datasets. After taking an intersection between selecting datasets, we identified two upregulated (SPP1 and MYH11) and five downregulated (ATF3, FOS, EGR1, FOSB, and NR4A2) hub genes. We finally chose night genes to verify their expression levels, including the other two genes (SFRP2 and SFRP4) involved in Wnt signaling; Their expression levels were significantly different between pterygium and conjunctiva.

CONCLUSIONS

We consider hormone-related, metabolic, and Wnt signaling pathways may be important in the pathology of pterygium development. Nine candidate genes we identified deserve further study and can be potential therapeutic targets.

Association between outpatient visits for pterygium and air pollution in Hangzhou, China

Air pollution could be a risk factor for the development of pterygium. This study aimed to investigate the potential associations between outpatient visits for pterygium and air pollutants. Using a time-stratified case-crossover design, the data of 3017 outpatients with pterygium visiting an eye center in Hangzhou, China, and the air pollution data of the Environmental Protection Department of Zhejiang Province between July 1, 2014, and November 30, 2019, were examined. The relationships between the air pollutants nitrogen dioxide (NO₂), sulfur dioxide (SO₂), ozone, and fine particulate matter (PM) with median aerometric diameter <2.5 μm (PM_2.5) and <10 μm (PM₁₀) and outpatient visits for primary pterygium were assessed using single- and multiple-pollutant models. Significant associations between outpatient visits for pterygium and air pollutants (PM_2.5, PM₁₀, SO₂, and NO₂) were observed. Younger patients were found to be more sensitive to air pollution. Interestingly, the younger female patients with pterygium were more vulnerable to PM_2.5 exposure during the warm season, while the younger male patients with pterygium were more sensitive to NO₂ during the cold season. Significant effects were also observed between the pterygium outpatients and PM_2.5 (odds ratio [OR] = 1.06, P = 0.02), PM₁₀ (OR = 1.04, P = 0.01), and SO₂ (OR = 1.26, P = 0.01) during the warm season, as well as NO₂ (OR = 1.06, P = 0.01) during the cold season. Our study provides evidence that outpatient visits for pterygium are positively associated with increases in the air pollutants PM_2.5, PM₁₀, SO₂, and NO₂, revealing the important role of air pollution in the occurrence and development of pterygium.

SPARC knockdown attenuated TGF-β1-induced fibrotic effects through Smad2/3 pathways in human pterygium fibroblasts

PURPOSE

Secreted protein acidic and rich in cysteine (SPARC), a matricellular glycoprotein, has been found to regulate processes involved in fibrotic diseases. The aim of this study was to investigate the anti-fibrotic effects of SPARC in primary human pterygium fibroblasts (HPFs) and elucidate the underlying mechanisms.

METHODS

The expression of SPARC in HPFs was knocked down by RNA interference-based approach. Subsequently, we examined the expression of profibrotic markers induced by transforming growth factor-β1 (TGF-β1), including type 1 collagen (COL1), α-smooth muscle actin (α-SMA), and fibronectin (FN). The changes in signaling pathways and matrix metalloproteinases (MMPs) were also detected by western blotting. The cellular migration ability, proliferation ability, apoptosis, and contractile phenotype were detected using the wound healing assay, Cell Counting Kit-8 assay, flow cytometry, and collagen gel contraction assay, respectively. The interaction between SPARC and TGF-β RII was detected by Co-IP RESULTS: Silencing of SPARC inhibited the basal and TGF-β1-induced expression of COL1, α-SMA, and FN in HPFs, and suppressed the expression of p-Smad2, p-Smad3, Smad4 and MMP2, MMP9. The downregulation of SPARC also attenuated the cell migration and contractile phenotype of HPFs. SPARC could bind to TGF-βRII under TGF-β1 treatment. However, knockdown of SPARC did not affect the proliferation and apoptosis of HPFs.

CONCLUSION

SPARC knockdown attenuated the fibrotic effect induced by TGF-β1 at least in part by inactivating the Smad2/3 pathways in HPFs. Therefore, SPARC may be a promising therapeutic target for the treatment of pterygium.

Sunlight exposure and eye disorders in an economically active population: data from the KNHANES 2008-2012

BACKGROUND

Sunlight exposure is a major risk factor for eye disorders. Most outdoor workers cannot avoid sunlight exposure. This study aimed to analyze the relationship between outdoor sunlight exposure and eye disorders in an economically active population.

METHODS

This study analyzed the 2008-2012 Korea National Health and Nutritional Examination Survey data. Sunlight exposure was categorized as < 5 hours and > 5 hours. We also analyzed the dose-dependent relationship between exposure to sunlight and eye disorders (cataracts, pterygium, and age-related macular degeneration [AMD]) using data from 2010 to 2012 by subdividing the exposure groups into < 2 hours, 2-5 hours, and ≥ 5 hours. Eye disorders were diagnosed by an ophthalmologist. The study participants were stratified by sex, and the results were analyzed using the χ2 test and multiple logistic regression analysis.

RESULTS

In the female group, the odds ratio of pterygium in the high-level sunlight exposure group was 1.47 (95% confidence interval [CI]: 1.15-1.89). Regarding AMD, the odds ratios were 1.42 (95% CI: 1.16-1.73), 1.33 (95% CI: 1.03-1.73), and 1.58 (95% CI: 1.15-2.16) in the total, male, and female groups, respectively. Analysis of the dose-response relationship revealed that the odds ratios of pterygium in the high-level sunlight exposure subgroups of the total and female groups were 1.62 (95% CI: 1.25-2.08) and 2.00 (95% CI: 1.39-2.88), respectively.

CONCLUSIONS

This study demonstrated a relationship between sunlight exposure and eye disorders in an economically active population. Women were found to be especially vulnerable to pterygium. However, additional prospective studies to clarify the pathophysiology of pterygium are needed.

The Role of Eph Receptors and Ephrins in Corneal Physiology and Diseases

The cornea, while appearing to be simple tissue, is actually an extremely complex structure. In order for it to retain its biomechanical and optical properties, perfect organization of its cells is essential. Proper regeneration is especially important after injuries and in the course of various diseases. Eph receptors and ephrin are mainly responsible for the proper organization of tissues as well as cell migration and communication. In this review, we present the current state of knowledge on the role of Eph and ephrins in corneal physiology and diseases, in particular, we focused on the functions of the epithelium and endothelium. Since the role of Eph and ephrins in the angiogenesis process has been well established, we also analyzed their influence on conditions with corneal neovascularization.

Time to Keratometric Stability After Pterygium Excision and the Associated Factors: A Clinical Perspective

Purpose

To determine the percentage of eyes with corneal astigmatic power stability and mean corneal keratometric power at 6-month post-pterygium excision, and to identify the time, and the associated factors, required to achieve stability.

Methods

This prospective observational study enrolled patients undergoing pterygium excision. Patients were evaluated for baseline characteristics and keratometric data before and every month after pterygium excision for six months using IOL Master 500^® (Carl Zeiss, Meditec). Clinically stable corneal astigmatic power and keratometric power were, respectively, defined as changes in these parameters of less than 0.25 and 0.27 diopters after two consecutive visits. Time to corneal astigmatic and keratometric power stability, as well as factors associated with the stability, were analyzed.

Results

Forty percent and 73.3% of eyes, respectively, demonstrated corneal astigmatic and corneal keratometric stability at six months post-operation. Within three months of reaching initial stability, the corneal astigmatic power and the mean keratometric power showed instability in 46.7% and 27.3% of patients, respectively. No patients with keratometric stability for more than three months became unstable during the study period. The extension of pterygium exceeding 3.0 mm was associated with a delay in time to corneal astigmatic stability (HRadjusted 0.41; 95% CI 0.19-0.89; P= 0.02).

Conclusion

According to the clinical relevance, 40% and 73% of patients, respectively, presented corneal astigmatic and keratometric stability within six months post-operation. Patients with a pterygium extension of more than 3 mm required a longer time for corneal astigmatic stability. It is recommended that keratometric stability be achieved for at least three months before commencing with additional procedures.

Histopathological Variability and Concomitant Lesions in Pterygium in a Large Case Series

Pterygium is a common lesion consisting of fleshy conjunctival growth extending towards the cornea. There is no documented risk of malignant transformation; however, concomitant disease is not rare, and its link to sunlight exposure indicates a risk of other malignancies. The purpose of our study is to describe histopathological features of resected pterygiums and to recognize patients at risk of other conjunctival diseases. One hundred and forty-nine formalin-fixed and paraffin-embedded pterygium samples were subjected to histopathological analysis. Histological H&E sections were obtained and digitalized using a Zeiss Axio Scan.Z1 slide scanner. Thirteen predefined morphological features were used to record histopathological changes in the epithelium and substantia propria. Neovascularization was observed in 54% of the samples. Sun damage, comprising solar elastosis and stromal plaque, was present in 81% of the samples. Variation in epithelial thickness was the most common change, with acanthosis and atrophy being observed in 62% and 26% of the samples, respectively. In our series, 21% (31/149) of pterygiums showed mild to moderate dysplasia, a finding that may be associated to ocular surface squamous neoplasia (OSSN). Moreover, 32% (47/149) of the cases showed melanocytic hyperplasia, which could represent primary acquired melanosis (PAM). There is a positive correlation between dysplasia and chronic inflammation (p=0.012) and an inverse correlation with epithelial atrophy (p=0.001) and neovascularization (p=0.05). Similarly, a positive correlation is observed between goblet cell hyperplasia and melanocytic hyperplasia (p=0.02). Our findings show that pterygiums harbour histological features that may be suggestive of OSSN or PAM in 53% of our patients. Whilst being on the benign side of the spectrum, these two entities are known for their potential progression to malignancy. A recommendation is made for all surgically excised pterygiums to be sent for histopathological diagnosis, and clear guidelines for reporting of these lesions should be established. Associated histopathological findings suggestive of other concomitant diseases should be identified to insure adequate follow-up of these patients.

Expression and role of specificity protein 1 and collagen I in recurrent pterygial tissues

AIM

To investigate the expression profiles of the transcription factor specificity protein 1 (Sp1) and collagen I in recurrent pterygial tissues. What is more, to compare the changes of Sp1 and collagen I among primary pterygial tissue, recurrent pterygial tissue and conjunctival tissue.

METHODS

In the prospective study, we collected the pterygial tissues of 40 patients who underwent resection of primary pterygial tissue and recurrent pterygial tissue, and the conjunctival tissues of 10 patients with enucleation due to trauma. The relative expression levels of Sp1 and collagen I were analyzed by reverse transcription quantitative-polymerase chain reaction and Western blot. Paired t-test was performed to compare the Sp1 and collagen I of recurrent pterygial tissues, as well as the primary pterygial tissues and conjunctival tissues. In further, Pearson's hypothesis testing of correlation coefficients was used to compare the correlations of Sp1 and Collagen I.

RESULTS

The content of Sp1 and collagen I mRNA and protein was significantly greater in recurrent pterygial tissue than that was in primary and conjunctival tissue (P<0.05). There was a positive correlation between the mRNA and protein levels of Sp1 and collagen I in recurrent pterygial tissues (protein: r=0.913, P<0.05; mRNA: r=0.945, P<0.05).

CONCLUSION

Sp1 and collagen I are expressed in normal conjunctival, primary, and recurrent pterygial tissues, but expression is significantly greater in the latter. Sp1 and collagen I may be involved in the regulation of the development of recurrent pterygium.

Understanding cornea epithelial stem cells and stem cell deficiency: Lessons learned using vertebrate model systems

Animal models have contributed greatly to our understanding of human diseases. Here, we focus on cornea epithelial stem cell (CESC) deficiency (commonly called limbal stem cell deficiency, LSCD). Corneal development, homeostasis and wound healing are supported by specific stem cells, that include the CESCs. Damage to or loss of these cells results in blindness and other debilitating ocular conditions. Here we describe the contributions from several vertebrate models toward understanding CESCs and LSCD treatments. These include both mammalian models, as well as two aquatic models, Zebrafish and the amphibian, Xenopus. Pioneering developments have been made using stem cell transplants to restore normal vision in patients with LSCD, but questions still remain about the basic biology of CESCs, including their precise cell lineages and behavior in the cornea. We describe various cell lineage tracing studies to follow their patterns of division, and the fates of their progeny during development, homeostasis, and wound healing. In addition, we present some preliminary results using the Xenopus model system. Ultimately, a more thorough understanding of these cornea cells will advance our knowledge of stem cell biology and lead to better cornea disease therapeutics.

The inhibitive effects of proteasome inhibitor MG-132 on pterygium fibroblasts in vitro and the potential key regulators involved

This study aimed to determine whether MG-132 as a proteasome inhibitor can effectively hinder pterygium progression, and to screen out potential regulators involved in MG-132 mediated process. Human pterygium fibroblasts (HPFs) were derived from pterygium tissues from 5 patients. Cell proliferation was examined by MTT, cell cycle and apoptosis were detected by flow cytometry. The overgrowth pterygium tissues were characterized by H&E staining and IHC compared with normal tissues. Differential mRNA expression with MG-132 treatment was determined by RNA sequencing and analyzed by GO and KEGG pathways. The expression levels of Nrf2, MCPIP1, CDKN1B and XBP1, four genes closely associated with pterygium, were detected by RT-qPCR and western blotting. MG-132 dose-dependently inhibited the growth of HPFs, induced G2/M phase arrest of cell cycle at a certain dose, and also caused cell apoptosis, with the levels of cleaved caspase3, cleaved PARP, Bax and p21 increased. Ki-67 and Bcl-2 were highly expressed while Bax was decreased in pterygium tissues. Total 7199 differentially expressed genes (DEGs) were identified, including HSPA family most significantly increased, and AL590428.1, AL122125.1 and lincRNAs such as FGF14-AS2 decreased. The up-regulated DEGs were mainly enriched in RNA degradation pathway, while down-regulated DEGs were related to the regulation of cell cycle. The expressions of Nrf2 and MCPIP1 were significantly increased, while XBP1 and CDKN1B were decreased. In conclusion, MG-132 inhibited the proliferation and induced apoptosis of HPFs in vitro with 7199 DEGs participated in, which may provide a useful reference for the exploitation of MG-132 in treating pterygium.

Recurrent pterygium: A review

Purpose:

To summarize the recent evidence regarding different aspects of pterygium recurrence.

Methods:

Human-based studies from PubMed, Scopus, and Google Scholar were identified using the following keywords: conjunctival disease, pterygium, recurrent pterygium, pterygium recurrence, pterygium management/surgery, conjunctival autograft (CAU), amniotic membrane graft/transplant, and adjuvant therapy (January 2009 to February 2021). We reviewed risk factors associated with the recurrence of pterygium, timing of recurrence, medical treatments to prevent from recurrence, and nonsurgical and surgical alternatives for management of recurrence.

Results:

Dry eye disease, black race, and young age are considered definite risk factors for recurrence. However, fleshy appearance of the pterygium and preoperative size remain controversial. Surgical techniques such as excessive suturing, insufficient conjunctival graft size, thick conjunctival graft with remained Tenon tissue, and postoperative graft retraction are considered possible risk factors for recurrence. Using fibrin glue instead of sutures can further reduce recurrence rates. Although recurrence could occur even after many years, most recurrences happen in the first 3–6 months after surgery. Multiple kinds of adjuvant medications are used before, during, or after the operation including mitomycin C (MMC), 5-fluorouracil (5-FU), corticosteroids, and anti-vascular endothelial growth factors (anti-VEGFs). Multiple weekly subconjunctival 5-FU injections are shown to be safe and effective in halting the progression of recurrent pterygium. Although topical bevacizumab is found to inhibit the growth of impending recurrent pterygium, the effect is mostly temporary. CAU is superior to amniotic membrane transplantation in the treatment for recurrent pterygia.

Conclusions:

There is yet to be a panacea in treating recurrent pterygium. Currently, there is not a globally accepted recommendation for treating recurrent pterygium with anti-VEGFs or 5-FU as a nonsurgical treatment. We strongly recommend using MMC as an adjunct to surgery in recurrent cases, with consideration of its specific complications. CAU is the most effective surgical treatment for recurrent pterygium, and other new surgical therapies need further investigation.

CircRNA Is a Rising Star in Researches of Ocular Diseases

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

Targeted delivery of mitomycin C-loaded and LDL-conjugated mesoporous silica nanoparticles for inhibiting the proliferation of pterygium subconjunctival fibroblasts

Pterygium is a degenerative disease that characterized by excessive fibrovascular proliferation. To reduce the recurrence rate, surgery is the main strategy, in combination with adjacent procedures or adjunctive therapy. One of the most common adjunctive agents, mitomycin C (MMC), is known as an alkylating agent that inhibits fibroblast proliferation but is limitedly applied in pterygium due to various complications. A previous study demonstrated that activated pterygium subconjunctival fibroblasts overexpressed low-density lipoprotein (LDL) receptors. In this study, we designed and synthesized MMC-loaded mesoporous silica nanoparticles conjugated with LDL (MMC@MSNs-LDL) to deliver MMC into activated pterygium fibroblasts in a targeted manner. The MMC loading efficiency was approximately 6%. The cell viability test (CCK-8 assay) revealed no cytotoxicity for the empty carrier MSNs at a concentration of ≤1 mg/ml after administration for 48 h in subconjunctival fibroblasts. Primary pterygium and normal human subconjunctival fibroblasts with or without stimulation by vascular endothelial growth factor (VEGF) were treated as follows: 1) 10 μg/ml MMC@MSNs-LDL for 24 h (MMC concentration: 0.6 μg/ml); 2) 0.2 mg/ml MMC for 5 min then cultured for 24 h after MMC removal; and 3) normal culture without any drug treatment. At 24 h, the anti-proliferative effect of MMC@MSNs-LDL in activated pterygium fibroblasts was similar to that of MMC (cell viability: 46.2 ± 5.5% vs 40.5 ± 1.1%, respectively, P = 0.349). Furthermore, the cytotoxicity of MMC@MSNs-LDL to normal fibroblasts with or without VEGF stimulation was significantly lower than that of traditional MMC (cell viability: 75.6 ± 4.4% vs 36.0 ± 1.5%, respectively, P < 0.001; 84.7 ± 5.5% vs 35.7 ± 1.3%, P < 0.001). The binding of fluorescently labeled MMC@MSNs-LDL in fibroblasts was assessed using confocal fluorescence microscopy. The uptake of targeted nanoparticles in fibroblasts was time dependent and saturated at 6 h. VEGF-activated pterygium fibroblasts showed more uptake of MMC@MSNs-LDL than normal fibroblasts with or without VEGF activation (both P < 0.001). Our data strongly suggest that MMC@MSNs-LDL had an effective antiproliferative role in activated pterygium fibroblasts, with reduced toxicity to normal fibroblasts compared to traditional application of MMC. LDL-mediated drug delivery might have great potential in the management of pterygium recurrence.

Postoperative treatment compliance rate and complications with two different protocols after pterygium excision and conjunctival autografting

AIM

To evaluate compliance rate to pterygium postoperative treatment with two different protocols.

METHODS

Review of clinical data of patients submitted to pterygium excision and conjunctival autografting in a single centre (and a single surgeon) in Barcelona between March 2014 and December 2017. Initial postoperative protocol (protocol 1) consisted of 4 months of topical steroids in a tapering fashion. Protocol 2 consisted of topical steroids tapered over 5 weeks. Compliance rate, complications and clinical outcomes were evaluated, and statistical comparisons were made.

RESULTS

120 surgeries were performed in 99 patients. Protocol 1 was applied in 63 cases and the next 57 followed protocol 2. Compliance with protocol 1 (57.6%) was lower than with protocol 2 (84.9%) (p = 0.002). Intraoperative complications (graft tear, corneal thinning, corneal perforation and bleeding) were found in 10 cases of protocol 1 and three cases of protocol 2, p = 0.08. Postoperative complications (graft dislocation, graft haematoma, ocular hypertension and recurrence) were found in 31 cases of protocol 1 (46.2%) and eight cases of protocol 2 (14%), p = 0.001. Six weeks after surgery, ocular hypertension was detected in eight cases corresponding to protocol 1 (13.6%) and two cases of protocol 2 (3.8%), p = 0.099. Recurrence rate during first year was higher in protocol 1 (26.3%) compared to protocol 2 (7.6%), p = 0.011. No cases of visual acuity worsening or infection were registered.

CONCLUSION

Protocol 2 has shown to have higher compliance rate than protocol 1 and less postoperative complications, proving to be a safe and effective postoperative treatment after pterygium surgery.

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.

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.

The in vitro anti-fibrotic effect of Pirfenidone on human pterygium fibroblasts is associated with down-regulation of autocrine TGF-β and MMP-1

We aimed to investigate the in vitro effect of pirfenidone (PFD) on proliferation, migration and collagen contraction of human pterygium fibroblasts (HPFs). HPFs were obtained from tissue explants during pterygium surgery. After treatment with pirfenidone, the HPFs proliferation was measured by MTT, cell cycle progression measured by flow cytometry, cell migration measured by the scratch assay, and cell contractility evaluated in fibroblast-populated collagen gels. The expression of TGF-β1, TGF-β2, MMP-1 and TIMP-1 were also determined with quantitative PCR, western blot and immunofluorescence staining. Results showed pirfenidone markedly inhibited HPFs proliferation with an IC₅₀ of approximately 0.2 mg/ml. After treatment with 0.2 mg/ml pirfenidone for 24 hours, HPFs were at G0/G1 cell cycle arrest, with significantly reduced cell migration capability and collagen contraction, decreased mRNA and protein expressions of TGF-β1, TGF-β2 and MMP-1, and no alterations of TIMP-1 expression. Thus, we have concluded that pirfenidone at 0.2 mg/ml inhibits proliferation, migration, and collagen contraction of HPFs, which is associated with decreased expression of TGF-β and MMP-1, and pirfenidone might represent a potentially therapeutic agent to prevent the recurrence of pterygium after surgery.

Elevation of S100 calcium-binding protein A7 in recurrent pterygium

Recurrent pterygium, a common ophthalmic disease, is difficult to treat as its pathogenesis is unclear. To investigate the key genes responsible for the recurrence of pterygium, tissue samples were collected from six patients with primary pterygium (primary group), six patients with recurrent pterygium (recurrent group) and six patients with ocular trauma (control group) who underwent surgery between December 2014 and June 2017. The differentially expressed genes amongst these tissues were detected using expression profiling microarrays and verified by reverse transcription-quantitative PCR (RT-qPCR). Comparing the primary and control groups, 10 genes, including PP7080, small proline-rich protein 2A, keratin 24, small proline-rich protein 2F, defensin β4A, serpin family A member 3, S100 calcium-binding protein A7 (S100A7), Fc fragment of IgG binding protein and BPI Fold Containing Family A Member 1, were identified to be consistently upregulated in recurrent pterygium tissues, whilst two genes (H19 imprinted maternally expressed transcript and secretoglobin family 2A member 1) were consistently downregulated. Following RT-qPCR verification, it was identified that that S100A7 gene was significantly upregulated in recurrent pterygium tissues compared with the other groups. Protein-protein interaction and Gene Ontology analysis further revealed that all genes interacting with S100A7 were mainly involved in the regulation of defense mechanisms against bacteria, mitogen-activated protein kinase (MAPK) pathway activation and receptor for advanced glycation end-products receptor binding. The present findings confirmed that elevation of S100A7 expression in recurrent pterygium may be associated with the inflammatory response and activation of the MAPK signaling pathway.

The broad spectrum of application of optical coherence tomography angiography to the anterior segment of the eye in inflammatory conditions: a review of the literature

Background

With an increased number of papers on how to interpret optical coherence tomography angiography (OCTA) findings in uveitis, the aim of this review is to assess its efficacy for the quantitative monitoring of structural and functional changes in inflamed conjunctiva and iris vessels in patients with acute anterior uveitis and iris neovascularization.

Main body

OCTA, currently designed as a retinal vascular imaging system, has been recently adapted for anterior segment and showed good potential for successful imaging of the conjunctiva, the cornea, and the iris. OCTA can successfully delineate corneal vessels with substantial image quality. At the same time, it can detect changes in conjunctival and limbal vascularization and thus can be applied to pseudo-inflammatory conditions such as pterygium. Anterior segment OCTA allows analysis of iris vasculature and 3-D reconstruction of the normal iris vessels. OCTA can determined iris vessel filling defects or their flow increase, when present, secondary to inflammatory conditions. In addition, OCTA gives qualitative vessel density values that can be compared pre- and post-anti-inflammatory treatment. OCTA for imaging of the iris vasculature in health and disease is highly dependent on iris pigmentation. In both OCTA and fluorescein angiography, iris pigmentation causes vasculature imaging blockage, but OCTA provides more detailed iris vasculature images. Fine, clinically invisible iris vessels can be visualized by OCTA in the very early stages as well as in the regressed stage of NVI. Additional studies including different iris pathologies are needed to determine the most optimal scanning parameters in OCTA of the anterior segment.

Conclusions

This review aims to establish the current application of OCTA to anterior segment disorders of the eye, with an emphasis on exploring its use in iris vessel dilation seen in various forms of iritis, as a predictive factor for further episodes of inflammation. In addition, OCTA can depict neovascularization of the iris secondary to proliferative diabetic retinopathy.

Understanding cornea homeostasis and wound healing using a novel model of stem cell deficiency in Xenopus

Limbal Stem Cell Deficiency (LSCD) is a painful and debilitating disease that results from damage or loss of the Corneal Epithelial Stem Cells (CESCs). Therapies have been developed to treat LSCD by utilizing epithelial stem cell transplants. However, effective repair and recovery depends on many factors, such as the source and concentration of donor stem cells, and the proper conditions to support these transplanted cells. We do not yet fully understand how CESCs heal wounds or how transplanted CESCs are able to restore transparency in LSCD patients. A major hurdle has been the lack of vertebrate models to study CESCs. Here we utilized a short treatment with Psoralen AMT (a DNA cross-linker), immediately followed by UV treatment (PUV treatment), to establish a novel frog model that recapitulates the characteristics of cornea stem cell deficiency, such as pigment cell invasion from the periphery, corneal opacity, and neovascularization. These PUV treated whole corneas do not regain transparency. Moreover, PUV treatment leads to appearance of the Tcf7l2 labeled subset of apical skin cells in the cornea region. PUV treatment also results in increased cell death, immediately following treatment, with pyknosis as a primary mechanism. Furthermore, we show that PUV treatment causes depletion of p63 expressing basal epithelial cells, and can stimulate mitosis in the remaining cells in the cornea region. To study the response of CESCs, we created localized PUV damage by focusing the UV radiation on one half of the cornea. These cases initially develop localized stem cell deficiency characteristics on the treated side. The localized PUV treatment is also capable of stimulating some mitosis in the untreated (control) half of those corneas. Unlike the whole treated corneas, the treated half is ultimately able to recover and corneal transparency is restored. Our study provides insight into the response of cornea cells following stem cell depletion, and establishes Xenopus as a suitable model for studying CESCs, stem cell deficiency, and other cornea diseases. This model will also be valuable for understanding the nature of transplanted CESCs, which will lead to progress in the development of therapeutics for LSCD.

Ocular Human Papillomavirus Infections

CONTEXT

- Human papillomavirus (HPV) has a well-known role in the pathogenesis of squamous cell carcinoma and precursor lesions of the cervix, anogenital region, and head and neck, but its role in the development of squamous neoplasms of the eye, particularly the conjunctiva, remains unclear.

OBJECTIVE

- To review recent evidence implicating HPV in the pathophysiology of ocular lesions.

DATA SOURCES

- Published articles obtained from a PubMed search of the English literature were the primary sources for this review.

CONCLUSIONS

- The low-risk HPV types 6 and 11 appear to play a role in the development of at least a subset of conjunctival squamous papillomas. The role of HPV in the pathogenesis of pterygium and ocular surface squamous neoplasia is less well defined. There is evidence to suggest that HPV may be a cofactor in the development of these lesions, acting in concert with ultraviolet radiation and/or human immunodeficiency virus infection in a subgroup of cases.

Assessment of miR-182, miR-183, miR-184, and miR-221 Expressions in Primary Pterygium and Comparison With the Normal Conjunctiva

OBJECTIVES

The aim of this study was to investigate the expression levels of miR-126-3p, miR-182-5p, miR-183-5p, miR-184, miR-221-3p, and miR-205-5p in primary pterygium tissue and compare these levels with those in healthy conjunctiva tissue.

METHODS

Twenty-four patients who were diagnosed with grade 3 primary pterygium and scheduled for surgery between January 2014 and January 2016 and had no systemic disease or other ocular pathology were included in the study. The control group comprised nasal interpalpebral conjunctival tissue specimens from 24 age- and sex-matched patients with no history of systemic disease or ocular pathology other than cataract. Expression levels of miR-126-3p, miR-182-5p, miR-183-5p, miR-184, miR-221-3p, and miR-205-5p were determined and compared between the pterygium and conjunctiva specimens.

RESULTS

Expression levels of miR-182-5p, miR-183-5p, and miR-184 were significantly higher in pterygium tissue compared with normal conjunctival specimens (P<0.0001, P=0.01, and P=0.01, respectively), whereas expression of miR-221-3p was significantly lower (P=0.02). Expression levels of miR-126-3p and miR-205-5p did not differ significantly between the 2 groups (P>0.05).

CONCLUSIONS

Expression levels of miR-182-5p, miR-183-5p, and miR-184 are increased, whereas expression of miR-221-3p is decreased in primary pterygium tissue, and these miRNAs may play a role in the pathogenesis of pterygium.

Bromfenac Inhibits TGF-β1-Induced Fibrotic Effects in Human Pterygium and Conjunctival Fibroblasts

Purpose

Nonsteroidal anti-inflammatory drugs (NSAIDs) have shown antifibrotic effects on several diseases. The aims of the present in vitro study were to investigate the antifibrotic effects of bromfenac (a kind of NSAID) on primary human pterygium fibroblasts (HPFs) and primary human conjunctival fibroblasts (HConFs), as well as to explore the possible mechanisms of these effects.

Methods

The cells used in this study were primary HPFs and HConFs, and profibrotic activation was induced by transforming growth factor-beta1 (TGF-β1). Western blot, quantitative real-time PCR, and immunofluorescence (IF) assays were used to detect the effects of TGF-β1 and bromfenac on the synthesis of fibronectin (FN), type III collagen (COL3), and alpha-smooth muscle actin (α-SMA) in HPFs and HConFs; the changes of signaling pathways were detected by Western blot; cell migration ability was detected by wound healing assay; cell proliferation ability was detected by CCK-8 assay; and pharmaceutical inhibitions of the downstream signaling pathways of TGF-β1 were used to assess their possible associations with the effects of bromfenac.

Results

Bromfenac suppressed the TGF-β1-induced protein expression of FN (0.59 ± 0.07 folds, P = 0.008), COL3 (0.48 ± 0.08 folds, P = 0.001), and α-SMA (0.61 ± 0.03 folds, P = 0.008) in HPFs. Bromfenac also attenuated TGF-β1-induced cell migration (0.30 ± 0.07 folds, P < 0.001), cell proliferation (0.64 ± 0.03 folds, P = 0.002) and the expression levels of p-AKT (0.66 ± 0.08 folds, P = 0.032), p-ERK1/2 (0.69 ± 0.11 folds, P = 0.003), and p-GSK-3β-S9 (0.65 ± 0.10 folds, P = 0.002) in HPFs. PI3K/AKT inhibitor (wortmannin) and MEK/ERK inhibitor (U0126) reduced the TGF-β1-induced synthesis of FN, COL3, and α-SMA in HPFs. All the results were similar in HConFs.

Conclusions

Bromfenac protects against TGF-β1-induced synthesis of FN, α-SMA, and COL3 in HPFs and HConFs at least in part by inactivating the AKT and ERK pathways.

Evaluation of antimitotic and antiangiogenic effect of preoperative subconjunctival application of mitomycin C in primary pterygium: a randomized trial

PURPOSE

To evaluate the influence of preoperative mitomycin C (MMC) on the proliferative behavior of fibroblasts and fibrovascular tissue derived from the primary pterygium using the immunohistochemical method (Ki67 and CD34).

DESIGN

Randomized clinical trial.

SUBJECTS, PARTICIPANTS AND/OR CONTROLS

Sixty-five patients with primary pterygium were randomly selected and divided into one of three groups. The control group had 29 patients that were only submitted to pterygium removal. The group that received the MMC injection a month before surgery had 16 patients, and the group that received the MMC 2 weeks before surgery had 20 patients. Each patient only had one eye operated on.

METHODS

Sixty-five patients were selected to undergo pterygium excision surgery. We randomly placed the patients into three groups: one without MMC (n = 29), one with MMC application 1 month before surgery (n = 16) and another with MMC application 2 weeks before surgery (n = 20). Subconjunctival injection was applied with 0.1 ml of 0.02% MMC in the pterygium body, and patients were followed for 2 years.

MAIN OUTCOME MEASURES

Proliferative behavior of fibroblasts and fibrovascular tissue using the immunohistochemical method (Ki67 and CD34) comparing the three groups.

RESULTS

Of the total 29 patients (44.6%) in the control group (without MMC application), 11 cases had recurrence (37.9%), of which seven (63.6%) were within 3 months of follow-up and four (36.3%) within 6 months of follow-up. The mean proliferation index of the recurrent cases was 4.5%, and of the cases without recurrence, it was 6.1%. There were 16 patients (24.6%) in the MMC application group 1 month before surgery, in which one case (6.25%) recurred at 6 months. In the group with MMC application 2 weeks before surgery, of the total of 20 patients (30.7%), there was one case of recurrence (5%) at 6 months. The proliferation index of the group that had MMC administered and did not have a recurrence was 7.2%, and in the group with recurrence, it was 6.4%. The CD34-labeled cell count was 5.8% among cases with recurrence and 5.6% in cases without recurrence. No side effects of MMC application were reported during the study follow-up period.

CONCLUSION

MMC was efficient to reduce the recurrence index despite the absence of a direct relation with its antimitotic and antiangiogenic effect in the samples that were analyzed.

Increased Expressions of ICAM-2 and ICAM-3 in Pterygium

Purpose: Pterygium, one of the most common ocular surface diseases, is characterized by inflammatory infiltrates, proliferation, angiogenesis, fibrosis, and extracellular matrix breakdown. The objective of this study was to elucidate the levels of the intercellular adhesion molecule (ICAM)-2, and ICAM-3 gene and protein expressions in pterygium. Methods: A total of 59 patients with pterygium were included in this study. mRNA from pterygial and conjunctival autograft tissues were extracted, and real-time polymerase chain reaction on the BioMark HD dynamic array system was performed for the ICAM-2 and ICAM-3 gene expressions. ICAM-2 and ICAM-3 protein expressions using western blot and immunohistochemistry methods were also investigated in pterygial and conjunctival autograft tissues. Results: ICAM-2 and ICAM-3 gene expressions were markedly augmented in pterygial tissues (P = 0.0018 and P = 0.0023, respectively). Significant increases in protein expressions in pterygial tissues were also detected for ICAM-2 and ICAM-3 (P = 0.0116 and P = 0.0252, respectively). In the immunohistochemical studies, there was a marked increase in ICAM-3 (P = 0.0152), but not in ICAM-2 (P = 0.1041), protein expressions in pterygial tissues. Significant positive correlations between pterygia grading with ICAM-2 protein expression (P = 0.0398) and ICAM-3 immunohistochemical scores (P = 0.0138) were observed. Conclusion: These results demonstrate, for the first time, the expressions of ICAM-2 and ICAM-3 in the pterygium. These findings may help to understand the signal transduction mechanisms in the pterygium formation and provide a new therapy strategy for pterygium treatment.

Circular RNAs: Novel Promising Biomarkers in Ocular Diseases

Circular RNAs (circRNAs) are a novel class of endogenous non-coding RNAs produced by back-splicing. They are found to be expressed in eukaryotic cells and play certain roles in various cellular functions, including fibrosis, cell proliferation, differentiation, apoptosis and angiogenesis. Dysregulated circRNAs are found in several human disorders including, malignancy, vascular, inflammatory as well as nervous diseases. Although, increasing evidence suggests that circRNAs may also contribute in different ocular diseases, the outline of circRNAs in ocular diseases remains obscure. In this review we consider the current state of knowledge regarding the potential role and underlying mechanism of circRNAs in ocular diseases including pterygium, age-related cataract, glaucoma, diabetic retinopathy, retinoblastoma, retinal vascular dysfunction and hyperhomocysteinemia induced ocular diseases, emphasizing that circRNAs could be promising biomarkers for the diagnosis and prognosis evaluation. Future circRNAs-targeted intervention may become a novel therapeutic tool for the treatment of ocular diseases.

Corneal Epithelial Damage and Impaired Tear Functions in Patients with Inflamed Pinguecula

Purpose

In this study, we evaluated corneal epithelial integrity and tear film parameters in patients with inflamed pinguecula and compared these findings with their fellow eyes and with healthy controls.

Methods

We evaluated the fluorescein staining properties and performed the tear break-up time (TBUT) test and Schirmer 2 test (ST2) measurements of 32 patients who had symptomatic unilateral inflamed pinguecula and compared the results with their fellow eyes and also with an age- and sex-matched control group.

Results

Twenty-three eyes (72%) in the inflamed pinguecula group and 1 eye (3.1%) in the fellow eyes group had punctate epithelial staining (PES) or epithelial defect on the nasal cornea (p < 0.001). There was no PES or epithelial defect in the control group. Eyes with inflamed pinguecula (n = 32) had lower TBUT and ST2 values compared to the control group (n = 32) (p < 0.001 for both). Fellow eyes (n = 32) also had lower TBUT and ST2 values compared to the control group (p=0.003 for both). There was no difference in the TBUT and ST2 results between the eyes with inflamed pinguecula and fellow eyes (p=0.286 and p=0.951, respectively).

Conclusion

A high percentage of eyes with inflamed pinguecula had nasal corneal epithelial staining or epithelial defect. We also found lower TBUT and ST2 results in eyes with inflamed pinguecula and the fellow eyes compared to the control group. These findings may be important in pathogenesis of pinguecula and pterygium and also in uncovering their relation.

Evaluation of Autologous Blood in Pterygium Surgery With Conjunctival Autograft

PURPOSE

Autologous blood has been used exploratively with conjunctival autograft in pterygium surgery. However, it is controversial whether autologous blood performed better than other fixation methods, including fibrin glue and sutures. This meta-analysis was conducted to evaluate the effectiveness of using autologous blood in pterygium surgery with conjunctival autograft.

METHODS

The study was conducted according to the PRISMA guidelines. The MEDLINE, Cochrane library, and Embase databases were systematically searched from their establishment until April 1, 2018. Randomized controlled trials comparing autologous blood with fibrin glue/suture in pterygium surgery with conjunctival autograft were included. The methodological quality of the included studies was assessed using the Cochrane risk of bias tool. Outcome measurements were recurrence, graft displacement, graft retraction, and surgical duration. Review Manager 5.3 (Cochrane Community, Cochrane Collaboration, London, UK) was used to perform the statistical analysis. When I < 50%, statistical heterogeneity was considered acceptable, and a fixed-effects model was adopted; alternatively, the random-effects model was used.

RESULTS

Seven randomized controlled trials including 516 patients were finally included in the meta-analysis. Four studies with 379 patients compared autologous blood and fibrin glue. Autologous blood was inferior to fibrin glue with respect to surgical duration, graft retraction, and graft displacement. However, there was no statistical difference between the 2 groups in terms of the recurrence rate. Four studies with 152 patients compared autologous blood and traditional suturing. Autologous blood was superior to sutures in terms of surgical duration and inferior to sutures in terms of graft retraction. No difference was detected in terms of graft displacement and recurrence rate.

CONCLUSIONS

In conclusion, autologous blood is an appropriate method for graft fixation in pterygium surgery. Current research suggests that autologous blood derivatives may be a promising approach after pterygium excision. However, this requires further confirmation.

Novel grid and sectoral analyses in monitoring corneal scars

PURPOSE

We aim to design two sampling methods, the grid and sectoral methods, to provide more precise detection of focal corneal scar changes with time following pterygium excision with the Pentacam imaging system.

METHODS

This is a retrospective study of our previous prospective observational case series. Thirty patients underwent primary pterygium excision with adjuvant topical mitomycin-C application were followed up and imaged with Pentacam system at postoperative weeks 1, 4, 12 and month 18. Grid and sectoral methods were used to sample density changes (in grayscale units, GSU) over the scarred areas as well as the clear pole of the same cornea.

RESULTS

Using the grid method, the average corneal densities were 39.4, 37.1, 36.7 and 34.7 GSU at postoperative 1, 4, 12 weeks and 18 months, respectively. On the other hand, using the sectoral method, the average corneal densities were 35.3, 33.3, 32.5 and 31.9 GSU at postoperative 1, 4, 12 weeks and 18 months, respectively. Paired t tests achieved statistical significance when comparing all follow-up time points to first postoperative visit. A statistically significant effect of time on the average density was shown on ANOVA (p < 0.001) using both analyses over the scarred areas, but not over the clear pole of the same cornea (p > 0.05).

CONCLUSION

Our novel approach to monitor corneal density changes using the grid or sectoral sampling methods seemingly enhances the power in monitoring density changes in corneal scars when compared to conventional total-diameter average densitometry.

Cellular Proliferation and Migration of Human Pterygium Cells: Mitomycin Versus Small-Molecule Inhibitors

PURPOSE

Nutlin is a drug that has been reported to activate p53 in various cell lines. We aim to study the effects of Nutlin in pterygium and compare the effects of Nutlin and mitomycin C (MMC) in pterygium cell lines.

METHODS

Pterygium samples (n = 3) were collected during surgical excision. Normal conjunctival tissues (n = 3) were collected from another quadrant of the same eye. Cell lines were established, and cells from passages 2 to 5 were used. Pterygium and conjunctival cells were treated with different doses of Nutlin and MMC. Cell proliferation and cell migration were measured.

RESULTS

Cell proliferation was reduced by 39-fold after treatment with 50 μM Nutlin. Cell migration was inhibited with increasing dosages of Nutlin (95% and 28% after treating with 2 and 50 μM Nutlin, respectively). Compared with MMC, Nutlin induced more pterygium cell death and less conjunctival cell death at low doses. At 50% lethal dose for pterygium cells, 95% of conjunctival cells survived after Nutlin treatment, whereas only 63% of conjunctival cells survived after MMC treatment. p21 expression was not detectable in MMC-treated pterygium cells but was detectable after Nutlin treatment.

CONCLUSIONS

In our study, MMC induced cell death in pterygium and conjunctival cell lines, whereas Nutlin had a targeted impact on pterygium cells. Our results implied that MMC inhibited both pterygium cell proliferation and migration through an apoptosis-independent pathway.

In Situ Blood Coagulum versus Sutures for Autograft Fixation after Pterygium Excision

PURPOSE

To compare the outcomes of autograft fixation using patient's own blood coagulum and using sutures after pterygium excision.

METHODS

In this prospective clinical study, 30 eyes of 30 patients with primary pterygium were randomly assigned into two groups: Group 1 (15 eyes) underwent autograft fixation with 10/0 nylon sutures and Group 2 (15 eyes) underwent autograft fixation by using in situ blood coagulum following pterygium excision. Primary outcome measure of this study was graft failure and displacement. Recurrence, the duration of surgery and patient discomfort were also evaluated. The patients were examined at day 1, day 7, month 1, month 6, and month 12.

RESULTS

Mean duration of surgery was significantly less in Group 2 (mean duration 14 ± 2 minutes) compared with Group 1 (mean duration 48 ± 2 minutes). Graft failure and displacement were more common in Group 2 (13.3%) compared with Group 1 (6.7%). Recurrence was reported equally in both groups. Patient discomfort was found significantly more in Group 1 (foreign body sensation due to sutures.) Conclusions: Autograft fixation by using in situ blood coagulum after pterygium excision is an effective technique with less patient discomfort and shorter operation time.

Long-Term Stability of Keratometry, Scheimpflug-Derived True Net Power, and Total Corneal Refractive Power After Primary Pterygium Excision

PURPOSE

To evaluate long-term changes in mean keratometry, astigmatism, true net power (TNP), and total corneal refractive power (TCRP) of corneas after primary pterygium excision.

METHODS

This is a prospective observational series conducted at a tertiary teaching hospital eye center in Hong Kong. A total of 31 eyes of 31 patients with primary pterygium excision were included. Patients with recurrent or double-headed pterygia or a history of corneal scars from previous trauma, infection, or surgery were excluded. Data were collected prospectively at postoperative weeks 1, 4, 12, and month 18.

RESULTS

Mean keratometry of the anterior cornea was 44.3 diopters (D) [95% confidence interval (CI): 43.6-44.9 D] at week 1, 44.3 D (95% CI: 43.6-44.9 D, standard error = 0.3) at week 4, 44.3 D (95% CI: 43.7-44.9 D) at week 12, and 44.1 D (95% CI: 43.5-44.7 D) at month 18. Mean astigmatism of the anterior cornea was 1.1 D (95% CI: 0.7-1.4 D), 1.0 D (95% CI: 0.7-1.3 D), 0.9 D (95% CI: 0.6-1.1 D), and 1.0 D (95% CI: 0.7-1.3 D) at postoperative 1, 4, 12 weeks, and 18 months, respectively. Mean keratometry, astigmatism of the anterior and posterior cornea, TNP and TCRP at 2.0-mm, 3.0-mm, 4.0-mm rings and zones remained unchanged on all follow-up visits (P = 1 for all comparisons).

CONCLUSIONS

Keratometric values including TNP and TCRP were stable as soon as 1 week after pterygium excision. This information might help clinicians in planning subsequent intraocular surgery that requires biometric assessment for intraocular lens implantation.