Immunohistochemical Profile and VEGF, TGF-β and PGE2 in Human Pterygium and Normal Conjunctiva: Experimental Study and Review of the Literature

Study of biomarkers p53, Ki-67, Bcl-2, and VEGF in pterygium

PURPOSE

To study the biomarkers present in primary pterygium samples of patients of Indian ethnicity and compare it with the samples obtained from the unaffected conjunctiva of the same eye.

METHODS

A prospective case-control study of 17 eyes in patients above 10 years of age with primary pterygium who underwent pterygium excision using limbal conjunctival autograft technique. The pterygium samples (cases) and conjunctival samples (controls) were sent for immunohistochemical (IHC) staining for the following biomarkers: p53, Bcl-2, Ki-67, and vascular endothelial growth factor (VEGF).

RESULT

The immunohistochemistry of the samples and the controls revealed p53 positivity in 47.05% of pterygium samples and 29.4% of controls ( P < 0.587). Nine cases each in pterygium and control samples were positive for Ki-67 expression. Differences in the staining pattern between the two groups were not statistically significant ( P < 1.000). Bcl-2 positivity was seen in 10 pterygium samples (58.8%) and 12 controls (70.5%), with no statistical difference between the two groups ( P < 0.455). VEGF expression was seen in both epithelial and endothelial cells of the samples and controls, with no statistical difference between the two groups, with P = 1.000 for the epithelial staining and P = 0.637 for endothelial staining.

CONCLUSION

The expression of biomarkers was comparable in both groups. We conclude that pterygium, against common belief, might not be a localized disease process but a global ocular phenomenon where the apparently healthy tissue also has some ongoing disease process at a molecular level.

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.

Impairment of autophagy promotes human conjunctival fibrosis and pterygium occurrence via enhancing the SQSTM1-NF-κB signaling pathway

Pterygium is a common ocular disease with a high recurrence rate, characterized by hyperplasia of subconjunctival fibrovascular tissue. Autophagy, an important process to maintain cellular homeostasis, participates in the pathogenic fibrosis of different organs. However, the exact role of autophagy in pterygium pathogenesis remains unknown. Here, we found that autophagic activity was decreased in human pterygium tissues compared with adjacent normal conjunctival tissues. The in vitro model of fibrosis was successfully established using human primary conjunctival fibroblasts (ConFB) treated with transforming growth factor-β1 (TGF-β1), evidenced by increased fibrotic level and strong proliferative and invasive capabilities. The autophagic activity was suppressed during TGF-β1- or ultraviolet-induced fibrosis of ConFB. Activating autophagy dramatically retarded the fibrotic progress of ConFB, while blocking autophagy exacerbated this process. Furthermore, SQSTM1, the main cargo receptor of selective autophagy, was found to significantly promote the fibrosis of ConFB through activating the PKCι-NF-κB signaling pathway. Knockdown of SQSTM1, PKCι, or p65 in ConFB delayed TGF-β1-induced fibrosis. Overexpression of SQSTM1 drastically abrogated the inhibitory effect of rapamycin or serum starvation on TGF-β1-induced fibrosis. Collectively, our data suggested that autophagy impairment of human ConFB facilitates fibrosis via activating the SQSTM1-PKCι-NF-κB signaling cascades. This work was contributory to elucidating the mechanism of autophagy underlying pterygium occurrence.

Effects of chemokine receptor CCR7 in the pathophysiology and clinical features of the immuno-inflammatory response in primary pterygium

OBJECTIVE

Chemokine receptor 7 (CCR7) has been considered a critical biomarker in inflammation and the immune response; however, little is known about CCR7 in pterygia. This study aimed to investigate whether CCR7 participates in the pathogenesis of primary pterygia and how CCR7 affects the progression of pterygia.

METHODS

This was an experimental study. Slip-lamp photographs of 85 pterygium patients were used to measure the width, extent, and area of pterygia with computer software. Pterygium blood vessels and general ocular redness were quantitatively analyzed with a specific algorithm. The expression of CCR7 and its ligands C-C motif ligand 19 (CCL19) and C-C motif ligand 21 (CCL21) in control conjunctivae and excised pterygia collected during surgery were analyzed by quantitative real-time polymerase chain reaction (qRT-PCR) and immunofluorescence staining. The phenotype of CCR7-expressing cells was identified by costaining for major histocompatibility complex II (MHC II), CD11b or CD11c.

RESULTS

The CCR7 level was significantly increased by 9.6-fold in pterygia compared with control conjunctivae (p = 0.008). The higher the expression of CCR7 was, the more blood vessels appeared in pterygia (r = 0.437, p = 0.002) and the more general ocular redness was (r = 0.51, p < 0.001) in pterygium patients. CCR7 was significantly associated with pterygium extent (r = 0.286, p = 0.048). In addition, we found that CCR7 colocalized with CD11b, CD11c or MHC II in dendritic cells, and immunofluorescence staining showed that CCR7-CCL21 is a potential chemokine axis in pterygium.

CONCLUSIONS

This work verified that CCR7 impacts the extent of primary pterygia invading the cornea and inflammation at the ocular surface, which may provide a possibility for a further in-depth understanding of the immunological mechanism in pterygia.

Uncovering the role of transient receptor potential channels in pterygium: a machine learning approach

OBJECTIVES

We aimed at identifying the role of transient receptor potential (TRP) channels in pterygium.

METHODS

Based on microarray data GSE83627 and GSE2513, differentially expressed genes (DEGs) were screened and 20 hub genes were selected. After gene correlation analysis, 5 TRP-related genes were obtained and functional analyses of gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) were performed. Multifactor regulatory network including mRNA, microRNAs (miRNAs) and transcription factors (TFs) was constructed. The 5 gene TRP signature for pterygium was validated by multiple machine learning (ML) programs including support vector classifiers (SVC), random forest (RF), and k-nearest neighbors (KNN). Additionally, we outlined the immune microenvironment and analyzed the candidate drugs. Finally, in vitro experiments were performed using human conjunctival epithelial cells (CjECs) to confirm the bioinformatics results.

RESULTS

Five TRP-related genes (MCOLN1, MCOLN3, TRPM3, TRPM6, and TRPM8) were validated by ML algorithms. Functional analyses revealed the participation of lysosome and TRP-regulated inflammatory pathways. A comprehensive immune infiltration landscape and TFs-miRNAs-mRNAs network was studied, which indicated several therapeutic targets (LEF1 and hsa-miR-455-3p). Through correlation analysis, MCOLN3 was proposed as the most promising immune-related biomarker. In vitro experiments further verified the reliability of our in silico results and demonstrated that the 5 TRP-related genes could influence the proliferation and proinflammatory signaling in conjunctival tissue contributing to the pathogenesis of pterygium.

CONCLUSIONS

Our study suggested that TRP channels played an essential role in the pathogenesis of pterygium. The identified pivotal biomarkers (especially MCOLN3) and pathways provide novel directions for future mechanistic and therapeutic studies for pterygium.

[Correction of refractive disorders after surgical treatment of recurrent pterygium (case study)]

Lamellar keratoplasty is the most effective and safe method of surgical treatment of recurrent pterygium, providing restoration of the corneal frame and optical properties and a high anti-relapse effect due to the barrier properties of the lamellar graft. However, potential postoperative changes in the regularity of the anterior and posterior surfaces of the cornea (especially in case of advanced stage of fibrovascular tissue growth) do not always allow achieving high functional results of treatment. The article presents a clinical case that demonstrates the effectiveness and safety of excimer laser correction of refractive disorders after surgical treatment of pterygium.

Resveratrol inhibits TGF-β1-induced fibrotic effects in human pterygium fibroblasts

BACKGROUND

Resveratrol is a polyphenolic phytoalexin which has the properties of anti-oxidant, anti-inflammatory and anti-fibrotic effects. The aim of this study was to investigate the anti-fibrotic effects of resveratrol in primary human pterygium fibroblasts (HPFs) and elucidate the underlying mechanisms.

METHOD

Profibrotic activation was induced by transforming growth factor-beta1 (TGF-β1). The expression of profibrotic markers, including type 1 collagen (COL1), α-smooth muscle actin (α-SMA), and fibronectin, were detected by western blot and quantitative real-time-PCR after treatment with various concentrations of resveratrol in HPFs to investigate the anti-fibrotic effects. Relative signaling pathways downstream of TGF-β1 were detected by Western blot to assess the underlying mechanism. Cell viability and apoptosis were assessed using CCK-8 assay and flow cytometry to evaluate proliferation and drug-induced cytotoxicity. Cell migration and contractile phenotype were detected through wound healing assay and collagen gel contraction assay.

RESULTS

The expression of α-SMA, FN and COL1 induced by TGF-β1 were suppressed by treatment with resveratrol in dose-dependent manner. The Smad3, mitogen-activated protein kinase (p38 MAPK) and phosphatidylinositol-3-kinase (PI3K) / protein kinase B (AKT) pathways were activated by TGF-β1, while resveratrol attenuated those pathways. Resveratrol also inhibited cellular proliferation, migration and contractile phenotype, and induced apoptosis in HPFs.

CONCLUSIONS

Resveratrol inhibit TGF-β1-induced myofibroblast activation and extra cellular matrix synthesis in HPFs, at least partly, by regulating the TGF-β/Smad3, p38 MAPK and PI3K/AKT pathways.

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.

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.

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.

Comparison between the triamcinolone and bevacizumab subconjunctivals and changes in Interleukin-1 mRNA expression in pterygium

Objectives

Pterygium is a fibrovascular external ocular mass that grows from the conjunctiva into the cornea. The effect of subconjunctival injection of triamcinolone and bevacizumab has been inadequately investigated worldwide. This study aims to analyse the expression of IL-1 after the injection of triamcinolone and bevacizumab subconjunctiva.

Methods

All patients are randomized into three groups: the triamcinolone, bevacizumab group, and placebo groups, with 5 patients in each in group. All subjects are injected subconjunctivally one week before surgery, and then surgery is performed with the autograft technique. The main outcome measures include changes in the IL-1 mRNA expression between the triamcinolone, bevacizumab, and placebo groups.

Results

All samples are completed after one month of follow-up. The changes in blood levels of mRNA IL-1 expression are as follows: 4.81 ± 0.52 in the bevacizumab group, 3.40 ± 2.63 in the triamcinolone group, and 1.08 ± 1.48 in the placebo group (p = 0.04). In the comparison between groups, there is a significant effect between the bevacizumab and placebo groups, 3.73 ± 1.12 (p = 0.00), with no significant effect in the triamcinolone group, 1.40 ± 1.12 (p = 0.06).

Conclusion

The subconjunctival injection of bevacizumab and triamcinolone before surgery is effective in suppressing inflammation in pterygium.

Review of proteomics approach to eye diseases affecting the anterior segment

Visual impairment and blindness is a major health burden worldwide, and major ocular diseases causing visual impairment pertain to the anterior segment of the eye. Anterior segment ocular diseases are common, yet complex entities. Although many treatment options and surgical techniques are available for these ailments, the underlying cause and pathogenesis is still unclear. Finding ways to fundamentally treat these patients and rectify the underlying dysregulations leading to the disease may help cure patients completely without major complications. Proteomics approaches are a novel way to distinguish dysregulated proteins in a variety of biological tissues in a hypothesis-free manner, thus helping to find the responsible pathways leading to a certain disease. The aim of the current study is to review the available knowledge in scientific literature regarding the proteomics studies done on anterior segment eye diseases and suggest potential clinical implications to exploit the results of these studies. SIGNIFICANCE: Anterior segment ocular diseases are responsible for a major proportion of visual impairment and blindness worldwide. Although ophthalmologists have several treatment options that can alleviate or control the progression of these diseases, no definite cure is available for most of them. Moreover, because these diseases are progressive, prompt diagnosis is of utmost important. Proteomics studies enable us to identify and quantify the dysregulated proteins in a biological specimen in a hypothesis-free manner. Understanding the dysregulated protein pathways shines a light on the pathogenesis of the disease. Moreover, these dysregulated proteins may act as biomarkers to help in diagnosis and treatment follow-up. Hence, in this article we sought out to review the available scientific literature regarding the proteomics studies of anterior segment ocular diseases and to identify potential applications of proteomic studies in clinic.

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.

Effect of multiple subconjunctival conbercept injections as an adjuvant to the surgical treatment of pterygium: a prospective randomised comparative 6-month follow-up study

OBJECTIVE

To evaluate the safety and efficacy of multiple subconjunctival injections of conbercept for pterygium patients after surgery.

METHODS

As a prospective randomised interventional trial, 96 eyes from 96 patients with a tendency to recur were collected and divided randomly into conbercept and 5-fluorouracil groups on the 5th day after pterygium. All patients received three subconjunctival injections of conbercept (0.2 ml) or 5-fluorouracil (0.2 ml) on the 5th day (baseline), and 2 and 4 weeks post-operatively. The pterygium morphology, colour intensity, recurrence, and complications were recorded and analysed pre-1st injection and 1 day, 1 week, 1 month, 3 months, and 6 months post-3rd injection. Moreover, no patient was drop-out.

RESULTS

There were striking differences between the two groups on post-3rd injections 1 day, 1 week, 1 month, 3 months, and 6 months (p = 0.001, 0.002, 0.000, 0.000, and 0.002, respectively) with respect to colour intensity: the eyes in conbercept group were lighter than the 5-Fu group. On post-3rd injection 6 months, prominent disparities existed between the two groups with respect to pterygium morphology (p = 0.006) and recurrence (p = 0.002), occurred in the conbercept group prior to the 5-Fu group. Moreover, corneal abrasions were not noted in the conbercept group, which was significantly less than the 5-Fu group (17/48; p = 0.000). There was no conspicuous discrepancy between the two groups with respect to subconjunctival haemorrhage (p = 0.789) and persistent epithelial defects (p = 0.078).

CONCLUSION

Multiple subconjunctival conbercept injections as an adjunct therapy for pterygium surgery was shown to be safe, effective, and well-tolerated.

Activation of the Sphingosine 1 Phosphate-Rho Pathway in Pterygium and in Ultraviolet-Irradiated Normal Conjunctiva

Sphingosine 1 phosphate (S1P) is a bioactive lipid that regulates cellular activity, including proliferation, cytoskeletal organization, migration, and fibrosis. In this study, the potential relevance of S1P–Rho signaling in pterygium formation and the effects of ultraviolet (UV) irradiation on activation of the S1P/S1P receptor axis and fibrotic responses were investigated in vitro. Expressions of the S1P2, S1P4, and S1P5 receptors were significantly higher in pterygium tissue than in normal conjunctiva, and the concentration of S1P was significantly elevated in the lysate of normal conjunctival fibroblast cell (NCFC) irradiated with UV (UV-NCFCs). RhoA activity was significantly upregulated in pterygium fibroblast cells (PFCs) and UV-NCFCs, and myosin phosphatase–Rho interacting protein (MRIP) was upregulated, and myosin phosphatase target subunit 1 (MYPT1) was downregulated in PFCs. Fibrogenic changes were significantly upregulated in both PFCs and UV-NCFCs compared to NCFCs. We found that the activation of the S1P receptor–Rho cascade was observed in pterygium tissue. Additionally, in vitro examination showed S1P–rho activation and fibrogenic changes in PFCs and UV-NCFCs. S1P elevation and the resulting upregulation of the downstream Rho signaling pathway may be important in pterygium formation; this pathway offers a potential therapeutic target for suppressing pterygium generation.

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.

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.

Expression of Inflammatory-Related NFκB Genes in Iranian Patients with Pterygium: A Case-Control Study

Pterygium is one of the most common eye conditions without any clear etiology. Some studies have suggested an association between sun exposure and pterygium, but others have proposed the role of genetic variations in its pathogenesis. To date, no study has investigated the association of inflammatory transcription factor, NFκB genes with pterygium in the Middle East. We examined the changes in expression of 3 inflammatory related NFκB1, NFκB2, and RELA genes in patients with pterygium. Thirty patients with pterygium and 30 age and sex-matched controls were enrolled in this case-control study. None of the participants showed any clinical signs of inflammation in their conjunctiva. Demographic information was obtained and the expression levels of three genes including NFκB1, NFκB2, and RELA were measured in their conjunctiva by real-time RT-PCR using gene-specific primers. Mean expression level of NFκB1, NFκB2 and RELA genes in patients were 2.4±0.3, 1.9± 0.5, and 1.8±0.4 times higher than normal subjects, respectively. Higher levels of gene expression were observed in individuals with more outdoor activity and sun exposure. Moreover, a significant correlation was observed between the expression levels of NFκB2 and RELA genes, suggesting a possible NFκB2- RELA heterodimer formation in patients with pterygium. This study has indicated a significant association between expressions of inflammatory-related NFκB1, NFκB2 and RELA genes, and pterygium. Further studies to verify the role of inflammation in the pathogenesis of pterygium, may provide new targets for managing pterygia.

YKL-40 expression in pterygium: a potential role in the pathogenesis

PURPOSE

The aim of the study was to evaluate whether YKL-40 (chitinase 3-like 1 protein) plays a role in pterygium pathogenesis.

METHODS

We included 42 primary pterygium patients and 24 control subjects with normal bulbar conjunctiva in the study. The pterygium patients were classified into the atrophic, fleshy, and intermediate groups according to the Tan classification. We then surgically removed the primary nasal pterygium and normal bulbar conjunctiva from the patients and immunohistochemically investigated YKL-40 expression.

RESULTS

YKL-40 expression was statistically significantly higher in the epithelial, endothelial, and stromal cells of the pterygium tissues than in the control tissues (P = 0.009, P = 0.003, P = 0.002, respectively). There was no significant correlation between the pterygium subgroups and YKL-40 expression (P > 0.05).

CONCLUSIONS

We believe YKL-40 may play a significant role in pterygium pathogenesis.

Endocan Overexpression in Pterygium

PURPOSE

The aim of this study was to evaluate the possible role of endocan in the pathogenesis of pterygium.

METHODS

The study was conducted on 33 patients with primary pterygium and 20 control subjects with normal bulbar conjunctiva. Patients with pterygium were graded into 3 groups as atrophic, fleshy, and intermediate, according to the Tan classification. Primary nasal pterygia and normal bulbar conjunctivas were surgically removed. Endocan expression was immunohistochemically investigated.

RESULTS

Endocan expression in epithelial and endothelial cells was statistically significantly higher in pterygium tissues than control tissues (P = 0.001). No significant correlation was observed between pterygium classification groups and endocan expression in both epithelial and endothelial cells (P > 0.05).

CONCLUSIONS

The results suggest that endocan may have a role in the pathogenesis of pterygium.

Pathophysiology of Corneal Scarring in Persistent Epithelial Defects After PRK and Other Corneal Injuries

PURPOSE

To analyze corneal persistent epithelial defects that occurred at 3 to 4 weeks after -4.50 diopter (D) photorefractive keratectomy (PRK) in rabbits and apply this pathophysiology to the treatment of persistent epithelial defects that occur after any corneal manipulations or diseases.

METHODS

Two of 168 corneas that had -4.50 D PRK to study epithelial basement membrane regeneration developed spontaneous persistent epithelial defects that did not heal at 3 weeks after PRK. These were studied with slit-lamp photographs, immunohistochemistry for the myofibroblast marker alpha-smooth muscle actin (α-SMA), and transmission electron microscopy.

RESULTS

Myofibroblasts developed at the stromal surface within the persistent epithelial defect and for a short distance peripheral to the leading edge of the epithelium. No normal epithelial basement membrane was detectable within the persistent epithelial defect or for up to 0.3 mm behind the leading edge of the epithelium, although epithelial basement membrane had normally regenerated in other areas of the zone ablated by an excimer laser where the epithelium healed promptly.

CONCLUSIONS

A persistent epithelial defect in the cornea results in the development of myofibroblasts and disordered extracellular matrix produced by these cells that together cause opacity within, and a short distance beyond, the persistent epithelial defect. Clinicians should treat persistent epithelial defects within 10 days of non-closure of the epithelium to facilitate epithelial healing to prevent long-term stromal scarring (fibrosis). [J Refract Surg. 2018;34(1):59-64.].

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.

Expression of prostaglandin E2 receptor subtypes in human pterygium and normal conjunctiva: immunohistochemical study

PURPOSE

In the present study, we aimed to evaluate the expression of EP receptors in primary and recurrent human pterygium tissues.

METHODS

Pterygium samples were collected from 65 patients with primary pterygium and 16 patients with recurrent pterygium. Normal conjunctival tissues were collected from nasal interpalpebral area from 17 patients without systemic and any other ocular pathology. Expression of EP receptors was evaluated by immunohistochemistry. The median value for each receptor staining score (RSS) was determined in normal conjunctival specimens. In this study, RSS of > median value was defined as positive staining or high expression and ≤ median value as negative staining or weak expression in specimens. Chi-square test was used for statistical analysis, and p value of less than 0.05 was considered significant.

RESULTS

Stromal expression of EP1 was significantly higher in primary and recurrent pterygium specimens compared to normal conjunctival tissues (p = 0.007 and p = 0.002, respectively). Epithelial expressions of EP2 and EP3 were significantly lower in primary pterygium specimens compared to normal conjunctival tissues (p = 0.005 and p < 0.0001, respectively), and stromal expressions were insignificant. Stromal expression of EP4 was significantly higher in primary and recurrent pterygium specimens compared to normal conjunctival tissues (p = 0.002 and p = 0.012, respectively).

CONCLUSIONS

Expression of EP receptors has been up- or downregulated in primary and recurrent pterygium tissues, and these receptors may play a role in formation and recurrence of 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.

Efficacy of curcumin in inducing apoptosis and inhibiting the expression of VEGF in human pterygium fibroblasts

Pterygium is an inflammatory and degenerative ocular surface disease, in which the conjunctiva on the cornea grows to form a fibrous tissue in the shape of a triangle. Although pterygium surgery is used broadly in clinical practice, its high recurrence rate poses a great concern for patients and doctors. In the present study, we examined the effects of curcumin on the apoptosis and proliferation of human pterygium fibroblasts (HPFs) in an in vitro culture system. HPFs were incubated with curcumin for 24 to 72 h (5, 20, 80 or 200 µmol/l). The proliferation-inhibiting effects of curcumin were assayed by MTT assay at different time points and at various concentrations. The expression of vascular endothelial growth factor (VEGF) in each group was detected by RT-qPCR and ELISA. The apoptotic effects of curcumin were detected by flow cytometry (FCM). Treatment with curcumin at 80 µmol/l for 48 h significantly inhibited HPF proliferation. Curcumin significant induced the apoptosis of HPFs. Our findings thus suggest that curcumin suppress cell proliferation in the pterygium by inducing HPF apoptosis and inhibiting VEGF expression. Thus, curcumin has potential for use as a novel agent for the treatment of pterygium in the near future.

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.

Increased Expression of Aquaporin-1 and Aquaporin-3 in Pterygium

PURPOSE

Recent studies have shown that aquaporins (AQPs) play an important role in proliferating tumor microvessels and angiogenesis. In this study, the authors investigated the expression of aquaporin-1 (AQP1) and aquaporin-3 (AQP3) in pterygial and normal conjunctival tissues.

METHODS

Fifteen patients with pterygium were enrolled in the study. Pterygium was excised, and a conjunctival rotational flap or autograft was inserted. Normal conjunctival tissue was obtained from the flap or graft. Western blot analysis was performed to assess the expression of AQP1 and AQP3 in pterygial and normal conjunctival tissues. Tissue localization of AQP1 and AQP3 was determined by immunohistochemical analysis.

RESULTS

AQP1 and AQP3 are localized in the epithelial and subepithelial regions in pterygial and normal conjunctival tissues. Protein expression of both AQP1 and AQP3 was elevated in pterygia when compared with conjunctival tissues. The significant increase in protein expression of AQP1 was 3-fold in pterygium over normal conjunctiva (P = 0.004) and 2-fold increase in AQP3 expression of pterygium was detected (P = 0.02) according to densitometric analysis.

CONCLUSIONS

Elevated protein expression of AQP1 and AQP3 was observed in pterygial tissues when compared with normal conjunctiva. The data suggest that the increased expression of AQP1 and AQP3 in pterygial tissues may be involved in the pathogenesis of pterygia, and therefore, AQP1 and AQP3 are potential therapeutic targets for preventing or delaying the progression of the disease.

Potential regulatory molecules in the human trabecular meshwork of patients with glaucoma: immunohistochemical profile of a number of inflammatory cytokines

Glaucoma occurs when there are imbalances between the production and the drainage of the eye liquid. The vast majority of the aqueous humor leaves the eye through the trabecular meshwork (TM). The cause of hypertonicity may be due to an alteration in the thickness of the TM. In the majority of cases the molecular changes that determine primary open‑angle glaucoma (POAG) are unclear. However, it has been hypothesized that the significant increase in the extracellular matrix (ECM) of the fibrillary bands in the TM is associated with possible inflammatory conditions. In this study the tissue distribution of interleukin (IL)‑6, IL‑1β, transforming growth factor-β1 (TGF‑β1), vascular endothelial growth factor (VEGF) and tumor necrosis factor α (TNF‑α) was analyzed in TM samples from patients with POAG by immunohistochemistry. Seven specimens from patients with POAG and three control tissues were analyzed by immunohistochemistry using specific antibodies against these cytokines. Morphological changes in the TM, such as increased cell content, macrophages, fibrosis and accumulation of neutrophils, were observed by transmission electron microscopy. In human TM tissues, an evident immunoreactivity for IL‑6, IL‑1β and TNF‑α was observed in patients with POAG when compared with the control subjects, indicating that these cytokines may be correlated with disease activity. TM endothelial cells secrete a number of factors and cytokines that modulate the functions of the cells and the ECM of the conventional outflow pathway. In the TM in glaucoma, macrophages produce cytokines, including IL‑6, IL‑1β and TNF‑α, leading to an acute inflammatory response and recruitment of other immune cells, including T lymphocytes. In addition, TGF‑β1 regulates and induces the expression of IL‑6 in TM that indirectly induces angiogenesis by stimulating VEGF expression. The present results support previous evidence that suggests that growth factors and cytokines can induce ECM remodelling and alter cytoskeletal interactions in the TM.

The role of heredity in pterygium development

Several risk factors, which include heredity, ultra-violet (UV) light and chronic inflammation, contribute to pterygium development. However, there is no report integrating these factors in the pathogenesis of pterygium. The aim of this review is to describe the connection between heredity, UV, and inflammation in pterygium development. Existing reports indicate that sunlight exposure is the main factor in pterygium occurrence by inducing growth factor production or chronic inflammation or DNA damage. Heredity may be a factor. Our studies on factors in pterygium occurrence and recurrence identify that heredity is crucial for pterygium to develop, and that sunlight is only a trigger, and that chronic inflammation promotes pterygium enlargement. We propose that genetic factors may interfere with the control of fibrovascular proliferation while UV light or (sunlight) most likely only triggers pterygium development by inducing growth factors which promote vibrant fibrovascular proliferation in predisposed individuals. It also just triggers inflammation and collagenolysis, which may be promoters of the enlargement of the fibrovascular mass. Pterygium probably occurs in the presence of exuberant collagen production and profuse neovascularisation.

Vascular endothelial growth factor (VEGF), mast cells and inflammation

Vascular endothelial growth factor (VEGF) is one of the most important inducers of angiogenesis, therefore blocking angiogenesis has led to great promise in the treatment of various cancers and inflammatory diseases. VEGF, expressed in response to soluble mediators such as cytokines and growth factors, is important in the physiological development of blood vessels as well as development of vessels in tumors. In cancer patients VEGF levels are increased, and the expression of VEGF is associated with poor prognosis in diseases. VEGF is a mediator of angiogenesis and inflammation which are closely integrated processes in a number of physiological and pathological conditions including obesity, psoriasis, autoimmune diseases and tumor. Mast cells can be activated by anti-IgE to release potent mediators of inflammation and can also respond to bacterial or viral antigens, cytokines, growth factors and hormones, leading to differential release of distinct mediators without degranulation. Substance P strongly induces VEGF in mast cells, and IL-33 contributes to the stimulation and release of VEGF in human mast cells in a dose-dependent manner and acts synergistically in combination with Substance P. Here we report a strong link between VEGF and mast cells and we depict their role in inflammation and immunity.

Vascular endothelial growth factor inhibitors: investigational therapies for the treatment of psoriasis

Psoriasis is a common inflammatory autoimmune condition in which environmental factors and genetic predisposition contribute to the development of disease in susceptible individuals. Angiogenesis is known to be a key pathogenic feature of psoriasis. Local and systemic elevation of vascular endothelial growth factor (VEGF)-A has been demonstrated in the skin and plasma of patients with psoriasis and is known to correlate with improvement following some traditional psoriasis treatments. A number of VEGF inhibitors are licensed for the treatment of malignancies and eye disease and isolated case reports suggest that some individuals with psoriasis may improve when exposed to these agents. The small number of cases and lack of unified reporting measures makes it difficult to draw generalizations and underline the heterogeneity of psoriasis as a disease entity. Though not yet licensed for the treatment of psoriasis in humans, experimental data supports the potential of VEGF inhibitors to influence relevant aspects of human cell biology (such as endothelial cell differentiation) and to improve animal models of skin disease. Given the multi-factorial nature of psoriasis it is unlikely that VEGF inhibitors will be effective in all patients, however they have the potential to be a valuable addition to the therapeutic arsenal in selected cases. Current VEGF inhibitors in clinical use are associated with a number of potentially serious side effects including hypertension, left ventricular dysfunction, and gastrointestinal perforation. Such risks require careful consideration in psoriasis populations particularly in light of growing concerns linking psoriasis to increased cardiovascular risk.