Expression of p27(KIP1) and cyclin D1, and cell proliferation in human pterygium

Z-shaped incision without epithelial resection in pterygium surgery

AIM

To introduce a novel surgical technique using a Z-shaped incision without epithelial resection in ophthalmic pterygia.

METHODS

This was a prospective study. During pterygium surgery, all proliferative tissues were separated from the cornea and conjunctiva without resection of the tissues. The unaffected conjunctiva was incised in a Z-shape. The upper (or lower) conjunctival flap was sutured to the lower (or upper) normal conjunctiva on the limbal sclera, while the proliferative tissue was sutured to the upper conjunctiva (or lower) near the fornix.

RESULTS

Ten patients with pterygia were eligible for this study. Eight patients with primary pterygia and 2 with recurrent pterygia were included. The age of patients at surgery ranged from 47 to 90y (average: 71.9y). Five patients each showed right and left-sided pterygia. The postoperative follow-up periods were from 8 to 78mo (average: 25.0mo). The surgery was successfully conducted and wounds were favorably reconstructed in all patients. The proliferative tissues sutured to the normal conjunctiva showed palor and attenuated neovessles, and never showed re-growth after surgery. Nine patients did not show recerrence. Recerrent pterygium was noted in 1 patient, but additional treatments were not required.

CONCLUSION

The procedure involves the reconstruction of pterygial tissue and normal conjunctiva using a Z-shaped incision. The scleral limbal wound can be covered with non-affected conjunctiva without any excision of conjunctival epithelia in patients with primary or recurrent pterygia.

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.

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

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

Cellular components of the idiopathic epiretinal membrane

Idiopathic epiretinal membrane (iERM) is a fibrocellular proliferation on the inner surface of the retina, which leads to decreased visual acuity and even central visual loss. As iERM is associated to advanced age and posterior vitreous detachment, a higher prevalence is expected with increasing life expectancy and aging of the global population. Although various cell types of retinal and extra-retinal origin have been described in iERMs (Müller glial cells, astrocytes, hyalocytes, retinal pigment epithelium cells, myofibroblasts, and fibroblasts), myofibroblasts have a central role in collagen production and contractile activity. Thus, myofibroblast differentiation is considered a key event for the iERM formation and progression, and fibroblasts, Müller glial cells, hyalocytes, and retinal pigment epithelium have been identified as myofibroblast precursors. On the other side, the different cell types synthesize growth factors, cytokines, and extracellular matrix, which have a crucial role in ERM pathogenesis. In the present review, the major cellular components and their functions are summarized, and their possible roles in the iERM formation are discussed. By exploring in detail the cellular and molecular aspects of iERM, we seek to contribute for better understanding of this fibrotic disease and the origin of myofibroblasts, which may eventually drive to more targeted therapeutic approaches.

Green Tea Catechins Attenuate Human Primary Pterygium Cell Survival and Migration Via Modulation of ERK p42/p44 and p38 Pathways

Pterygium belongs to an ocular surface disease with triangular-shaped hyperplastic growth, characterized by conjunctivalization, inflammation, and connective tissue remodeling. We previously demonstrated neoplastic-like properties of pterygium cells. Green tea catechin, (-)-epigallocatechin gallate (EGCG), has been shown to possess antitumorigenic properties; herein, we aimed to determine the effects of green tea catechins on human primary pterygium cell survival and migration and compared to that on patients' conjunctival cells. Both human primary pterygium and conjunctival cells expressed EGCG receptor, the 67 kDa laminin receptor. Seven-day treatment of green tea extract (Theaphenon E; 16.25 μg/mL) and EGCG (25 μM) attenuated pterygium cell proliferation by 16.78% (p < 0.001) and 24.09% (p < 0.001) respectively, without significantly influencing conjunctival cells. Moreover, green tea extract (16.25 μg/mL) and EGCG (25 μM) treatments also hindered pterygium cell migration by 35.22% (p < 0.001) and 25.20% (p = 0.019), respectively, but not conjunctival cells. Yet, green tea extract and EGCG treatments did not significantly induce pterygium cell apoptosis. Furthermore, green tea extract and EGCG treatments significantly increased the phosphorylation of p38 protein but reduced the phosphorylation of p42/p44 protein in pterygium cells. In summary, this study revealed that green tea extract and EGCG attenuated human primary pterygium cell survival and migration in vitro without damaging conjunctival cells, suggesting a novel potential therapeutic approach for primary pterygium treatment.

A case of pterygium-like proliferation containing postoperative limbal dermoid remnants: a clinicopathological study

BACKGROUND

This study reports a case of pterygium-like proliferation containing postoperative limbal dermoid remnants and its clinicopathological features.

CASE PRESENTATION

A 79-year-old Japanese woman, with a history of congenital limbal dermoid resection at age 12, presented with a pterygium-like tissue growth in the left eye. Its temporal location and marked thickness with abundant fatty droplets were atypical of primary pterygium. We performed pterygium surgery and ocular surface reconstruction. Pathological findings included squamous metaplasia, neovessels, and elastic degeneration, as well as prominent subepithelial and stromal accumulation of collagen fibers, adipose tissue formation, and presence of a peripheral nerve corresponded with the frequent findings of limbal dermoid. Ki67, a marker for cell proliferation, was immunopositive in pterygial epithelial cells and neovascular endothelial cells, but not in dermoid components.

CONCLUSIONS

Although the pathological finding of degenerative elastic fibers indicated the common feature of ultraviolet-induced pterygium, clinical appearances were atypical possibly due to modification with dermoid remnants.

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

PURPOSE

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSION

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

Overexpression of fractalkine and its histopathological characteristics in primary pterygium

PURPOSE

This study aimed to evaluate the differences in the expressions of fractalkine in normal bulbar conjunctiva and primary pterygium tissues.

METHODS

The study included 48 patients who had been operated on for primary pterygium. Histopathologically, the presence of epithelial atypia, epithelial hyperplasia, goblet cell hyperplasia, epithelial lymphocytic exocytosis, stromal inflammation, mast cell count, and stromal vascularity were evaluated in the primary pterygium tissues. An immunohistochemical fractalkine stain was applied to the primary pterygium tissue samples and normal bulbar conjunctival tissue samples.

RESULTS

Primary pterygium and normal bulbar conjunctival tissue samples were histopathologically analyzed. Epithelial atypia, epithelial hyperplasia, epithelial lymphocytic exocytosis, stromal inflammation, stromal vascularity, and mast cell count were found to be significantly higher in the primary pterygium (p = 0.001, p = 0.002, p = 0.024, p = 0.007, p = 0.024, and p = 0.013, respectively). When evaluated in terms of fractalkine expression, the epithelial, vascular endothelial, and inflammatory cells were significantly higher in the primary pterygium (p ≤ 0.001, p = 0.002, p = 0.001, respectively). Moreover, compared to the normal bulbar conjunctiva, Ki-67 expression was significantly higher in the primary pterygium tissue samples.

CONCLUSION

Fractalkine might play a key role in the etiopathogenesis of pterygium. Fractalkine may be important in developing new treatment approaches.

How to minimize pterygium recurrence rates: clinical perspectives

The main treatment for pterygium is surgical removal. However, pterygium surgery is concerned with high rates of postoperative recurrence. Predicting factors of recurrence are not fully understood, yet, but they probably depend on a multitude of patient-related, clinical, and/or surgical factors. Several adjuvant treatments have been proposed to reduce postoperative pterygium recurrence, including different antimetabolites, antiangiogenetic factors, and radiation therapy. The purpose of this review is to collect the current evidence regarding application and limits of different therapeutic approaches for preventing postoperative recurrence of pterygium, giving insights and perspectives for better management of this disease. In the light of the current evidence, pterygium surgery cannot disregard wound coverage with conjunctival autografting or rotational flap combined with adjuvant treatments. The rotational flap technique is associated with shorter surgical time rates and prevents graft displacement and necrosis, given its vascular pedicle. Amniotic membrane may still be reserved in case of great conjunctival defects or insufficient conjunctiva. Repeated subconjunctival antivascular endothelial growth factor injections can be considered as an effective and safe adjuvant treatment. Moreover, management of postoperative pain is crucial. Innovative treatment strategies will probably target different molecular pathways, considering recent findings regarding pterygium pathogenesis, to improve better understanding and develop universally shared guidelines. Great importance shall be dedicated to the identification of novel molecular biomarkers and favoring factors of recurrence, in order to achieve a customized surgical treatment for each patient and obtain maximal reduction of postoperative recurrence.

Pterygial body epithelium domination of pterygial proliferation with TCF4 as a potential key factor

AIM

To characterize the proliferative capacity of pterygial epithelium in different regions (head, neck and body) of pterygium and explore the function of transcription factor 4 (TCF4) in pterygium proliferation.

METHODS

Thirty pterygium tissues and 10 normal conjunctival tissues were obtained from Zhongshan Ophthalmic Center (ZOC) and Guangdong Eye Bank, respectively. Proliferative capacity of head, neck and body in pterygial epithelium was measured using clonal analysis, fold growth analysis and expression profile of proliferative markers revealed by immunofluorescent staining and real-time PCR. The expression of TCF4 was highlighted by double immunofluorescent staining with other proliferation related markers such as proliferating cell nuclear antigen (PCNA) and ATP-binding cassette sub-family G member 2 (ABCG2).

RESULTS

The proliferative potential of pterygial epithelium was higher than that of normal conjunctival epithelium. High expression levels of proliferative markers (P63α, PCNA and ABCG2) in pterygial body epithelium were observed in immunofluorescent staining and real-time PCR (P<0.05). Also, epithelial cells isolated from pterygial body demonstrated higher proliferative capacity in clonal analysis and fold growth analysis, than those isolated from the head and neck regions. The TCF4 expression in pterygial epithelium was similar to other proliferative markers (P63α, PCNA and ABCG2), as higher in pterygial body than head and neck. Moreover, TCF4 showed coexpression with other proliferation-related markers (PCNA and ABCG2) in the double immunofluorescent staining experiment.

CONCLUSION

The proliferative capacity in pterygial body epithelium is prominent than the head and neck regions, and upregulated TCF4 may be associated with enhanced proliferation in the pterygium.

MiR-21 promotes pterygium cell proliferation through the PTEN/AKT pathway

Purpose

To evaluate the effect of the overexpression of miR-21 on the properties of pterygium and examine whether miR-21 promotes the proliferation of pterygium cells through targeting the PTEN/AKT signaling pathway.

Methods

Information regarding patient gender, age, and pterygium severity was gathered. Expression of miR-21 was obtained through examination of excised pterygium tissues and superior conjunctiva tissues with real-time PCR. Human pterygium fibroblasts (HPFs) were obtained from pterygium surgery and subjected to primary culture. The HPF cell lines were divided into a negative control group, an miR-21 inhibitor group, and an miR-21 inhibitor + VO-Ohpic trihydrate group, and then the cell viability and apoptosis and the expression of PTEN and AKT were examined.

Results

Fifty-eight subjects with unilateral primary pterygium were included. An increase in the miR-21 levels in pterygium tissue was evident compared with that in the paired normal conjunctival tissues (independent-samples t test, p<0.01). As the severity of the pterygium increased, the miR-21 levels increased (p=0.004, rs=0.373, Spearman's rank correlation coefficient). The miR-21 inhibitor suppressed the proliferation and induced apoptosis of HPF cells through increasing the PTEN expression, and further decreasing the expression of p-AKT, which could be reversed by the PTEN inhibitor VO-Ohpic trihydrate.

Conclusions

Aberrant miR-21 overexpression in the pterygium could target PTEN, which contributes to abnormal proliferation of the HPF cells through depressing the PTEN/AKT pathway. The results also suggested the potential of miR-21 and the PTEN/AKT pathway as a novel therapeutic strategy for pterygium.

Current approaches and future directions in the management of pterygium

Pterygium, a common ocular surface disorder, has a complex pathophysiology that may mimic tumorigenesis. There is altered expression of cell cycle/proliferation-related factors in pterygium tissues. Therefore, similar to cancer treatments, the management of pterygium ought to be multifactorial based on the patient's condition. Current therapeutic methods for pterygium are focused on surgical resection in conjunction with antimetabolite use, in addition tissue graft is usually performed in the context of the avoidance of bare sclera. However, future directions in the management of pterygia will likely focus on genetic approaches. This perspective views the pathogenesis of pterygium, its existing therapies as well as current and future challenges in its treatment.

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

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

Cultivation and characterization of pterygium as an ex vivo study model for disease and therapy

PURPOSE

Development of ex vivo model to study pathogenesis, inflammation and treatment modalities for pterygium.

METHODS

Pterygium obtained from surgery was cultivated (3 months). Gravitational attachment method using viscoelastic facilitated adherence of graft and outgrowing cells. Medium contained serum as the only growth supplement with no use of scaffolds. Surface profiling of the multi-layered cells for hematopoietic- and mesenchymal stem cell markers was performed. Examination of cells by immunohistochemistry using pluripotency, oxidative stress, stemness, migration and proliferation, epithelial and secretory markers was performed. The effect of anti-proliferative agent Mitomycin C upon secretion of pro-inflammatory cytokines IL-6 and IL-8 was assessed.

RESULTS

Cells showed high expression of migration- (CXCR4), secretory- (MUC1, MUC4) and oxidative damage- (8-OHdG) markers, and low expression of hypoxia- (HIF-1α) and proliferation- (Ki-67) markers. Moderate and low expression of the pluripotency markers (Vimentin and ΔNp63) was present, respectively, while the putative markers of stemness (Sox2, Oct4, ABCG-2) and epithelial cell markers- (CK19, CK8-18) were weak. The surface marker profile of the outgrowing cells revealed high expression of the hematopoietic marker CD47, mesenchymal markers CD90 and CD73, minor or less positivity for the hematopoietic marker CD34, mesenchymal marker CD105, progenitor marker CD117 and attachment protein markers while low levels of IL-6 and IL-8 secretion ex vivo, were inhibited upon Mitomycin C treatment.

CONCLUSION

Ex vivo tissue engineered pterygium consists of a mixture of cells of different lineage origin, suitable for use as a disease model for studying pathogenesis ex vivo, while opening possibilities for new treatment and prevention modalities.

Molecular Basis of Pterygium Development

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

EphB4 expression in pterygium is associated with microvessel density

OBJECTIVE

Angiogenesis is a key component of the pathogenesis process of pterygium, which is the growth of fibrovascular tissue on the cornea. It has been reported that EphB4, a receptor tyrosine kinase of the ephrin-Eph system, plays important role in vascular development during embryogenesis and tumor angiogenesis and is potentially involved in ocular angiogenesis. The aim of this study is to investigate the role of EphB4 in pterygia.

METHODS

Fifteen pterygium samples and their paired upper bulbar conjunctiva were evaluated for expression of EphB4 and CD31 by using immunohistochemical staining. The expression level of the mRNA of EphB4 gene in 7 pterygia and matched upper bulbar conjunctiva was evaluated by using a quantitative real-time RT-PCR analysis. Microvessel density (MVD) was assessed with antibody that targets CD31.

RESULTS

EphB4 protein was high expressed in the epithelium and stroma of pterygia compared to those in upper bulbar conjunctiva. Immunohistochemical staining showed that pterygia presented with statistically significant higher average count of microvessel compared to normal conjunctivae (28.24 ± 6.79 vs 11.09 ± 2.96 per high power field, P < 0.001). MVD values in stroma of the pterygium and normal conjunctiva presented a significant correlation with EphB4 staining (P < 0.001). Compared with autologous upper bulbar conjunctiva grafts, the expression of the EphB4 mRNA was increased in pterygia in 4 paired samples, including those 3 recurrent ones.

CONCLUSION

The expression of EphB4 in pterygium was significantly related with the increased MVD and may be involved in angiogenesis. EphB4 protein is a potential target for treatment of pterygium.

SERPINA3K plays antioxidant roles in cultured pterygial epithelial cells through regulating ROS system

We recently demonstrated that SERPINA3K, a serine proteinase inhibitor, has antioxidant activity in the cornea. Here we investigated the antioxidant effects of SERPINA3K on the pterygial, which is partially caused by oxidative stress in pathogenesis. The head part of primary pterygial tissue was dissected and then cultured in keratinocyte serum-free defined medium (KSFM). The cultured pterygial epithelial cells (PECs) were treated with SERPINA3K. The cell proliferation and migration of PECs were measured and analyzed. Western blot and quantitative real-time polymerase chain reaction (PCR) assay were performed. It showed that SERPINA3K significantly suppressed the cell proliferation of PECs in a concentration-dependent manner, compared with cultured human conjunctival epithelial cells. SERPINA3K also inhibited the cell migration of PECs. Towards its underlying mechanism, SERPINA3K had antioxidant activities on the PECs by significantly inhibiting NADPH oxidase 4 (NOX4), which is an important enzyme of ROS generation, and by elevating the levels of key antioxidant factors of ROS: such as NAD(P)H dehydrogenase (quinone 1) (NQO1), NF-E2–related factor-2 (NRF2) and superoxide dismutases (SOD2). Meanwhile, SERPINA3K down-regulated the key effectors of Wnt signaling pathway: β-catenin, nonphospho-β-catenin, and low-density lipoprotein receptor-related protein 6 (LRP6). We provided novel evidence that SERPINA3K had inhibitory effects on pterygium and SERPINA3K played antioxidant role via regulating the ROS system and antioxidants.

MiRNA-221 negatively regulated downstream p27Kip1 gene expression involvement in pterygium pathogenesis

PURPOSE

MiRNAs are small noncoding RNAs that have been implicated in tumor development. They regulate target gene expression either by mRNA degradation or by translation repression. Activation of β-catenin has been linked to pterygium progression. Here, we hypothesize that β-catenin-associated miRNA, miRNA-221, and downstream p27Kip1 gene expression are correlated with the pathogenesis of pterygium.

METHODS

We collected 120 pterygial and 120 normal conjunctival samples for this study. Immunohistochemistry and real-time reverse transcription (RT)-PCR were performed to determine β-catenin protein localization, miR-221, and p27Kip1 gene expression. Pterygium cell line (PECs) cell models were used to confirm the effect of β-catenin, miR-221, and p27Kip1 gene in the proliferation of pterygium cells.

RESULTS

Seventy-two (60.0%) pterygial specimens showed high miR-221 expression levels, which was significantly higher than the control groups (13 of 120, 10.8%, p<0.0001). MiR-221 expression was significantly higher in β-catenin-nuclear/cytoplasmic-positive groups than in β-catenin membrane-positive and negative groups (p=0.001). We also found that p27Kip1 gene expression in pterygium was negatively correlated with miR-221 expression (p=0.002). In the clinical association, miR-221 expression was significantly higher in the fleshy and intermediate groups than in the atrophic group (p=0.007). The association of miR-221, p27Kip1 and proliferation of pterygium were also confirmed in the PECs model.

CONCLUSIONS

Our study demonstrated that activation of β-catenin in pterygium may interact with miR-221, resulting in p27Kip1 gene downregulation that influences pterygium pathogenesis.

Increased importin 13 activity is associated with the pathogenesis of pterygium

PURPOSE

We previously reported that importin 13 (IPO13), a member of the importin-β family of nuclear import proteins, regulates nuclear import of the glucocorticoid receptor in airway epithelial cells, IPO13 serves as a potential marker for corneal epithelial progenitor cells, and IPO13 is associated with corneal cell proliferation. Here we investigated the role of IPO13 in the pathogenesis of pterygium and the underlying mechanism including interaction with other cell proliferation-related factors: keratin 17 (K17), a lesional protein and a member of the type I keratins, and c-Jun, a protein of the activator protein-1 complex.

METHODS

Tissue samples were collected from primary pterygia, recurrent pterygia, and normal conjunctiva to perform the following experiments: immunohistochemical measurement of IPO13 and K17. Pterygium epithelial cells (PECs) were cultured in keratinocyte serum-free defined medium to examine the expression of IPO13 and K17. Lentivirus-mediated silencing and overexpression IPO13 testing was conducted, and K17 alternation was evaluated with western blot and immunostaining. In addition, the translocation of c-Jun (a K17 regulator) was further examined after IPO13 was silenced.

RESULTS

IPO13 activity was significantly increased in the basal layer of the epithelium of the pterygium. In cultured PECs, overexpression or knockdown of the IPO13 gene increased or decreased PEC proliferation, respectively. IPO13 was colocalized with K17 in the epithelium of the pterygium, and overexpression or knockdown of the IPO13 gene induced upregulation or downregulation of K17 expression in PECs, respectively. In addition, silencing of the IPO13 gene blocked nuclear translocation of c-Jun.

CONCLUSIONS

We provided novel evidence that IPO13 may contribute to the pathogenesis of pterygium via modulation of K17 and c-Jun.

Immunohistochemical detection of Hsp90 and Ki-67 in pterygium

BACKGROUND

To examine the immunohistochemical expression of heat shock protein 90 (Hsp90) and Ki-67 protein in human pterygium.

MATERIALS AND METHODS

Tissues obtained during pterygium surgery of 15 patients who underwent the bare-sclera procedure and 10 normal conjunctivae were studied. All of these pterygia were primary ones. Recurrent pterygia were excluded. Normal bulbar conjunctivas (2 x 2 mm) were obtained from the nasal region close to the limbus from patients during their cataract and retina surgeries. Immunohistochemical detection of Hsp90 and Ki67 was done using the streptavidin-biotin method in paraffin embedded tissue sections.

RESULTS

The percentage of cells stained for Hsp90 was greater for pterygium epithelium (76 ± 10.8) than for normal conjunctiva (1.4 ± 0.8). In each pterygium sample more than 60% of cells were positive. The differences in positive cells between normal and pterygium epithelium were highly significant for Hsp90 (P < 0,001).Pterygium epithelium also showed a higher percentage of cells that stained for Ki67 (10.1 ± 9.5) than for normal conjunctiva (2.1 ± 1.9). The differences in positive cells were also statistically significant for Ki67 (P < 0.01). Although there were significant differences in the majority of samples observed. It was noted that in some samples there was no difference between normal and pterygium epithelium for Ki67.

CONCLUSION

Our results indicate an abnormal expression of Hsp90 and ki-67 in pterygium samples when compared to normal conjunctiva.The finding of abnormal expression of levels of Hsp90 in pterygium samples can stimulate new research into pterygium and its recurrence.

VIRTUAL SLIDES

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1128478792898812.

Expression of vascular endothelial growth factor C in human pterygium

Vascular endothelial growth factor C (VEGF-C) and its receptor VEGFR-3 mediate lymphangiogenesis. In this study, we analyzed the expression of VEGF-C and VEGFR-3 as well as lymphatic vessels in the pterygium and normal conjunctiva of humans. Fifteen primary nasal pterygia and three normal bulbar conjunctivas, surgically removed, were examined in this study. The lymphatic vessel density (LVD) and blood vessel density were determined by the immunolabeling of D2-40 and CD31, markers for lymphatic and blood vessels, respectively. VEGF-C and VEGFR-3 expression in pterygial and conjunctival tissue proteins was detected by Western blotting and were evaluated using immunohistochemistry. The LVD was significantly higher in the pterygium than normal conjunctiva (p < 0.05). Western blot demonstrated high-level expression of VEGF-C and VEGFR-3 in the pterygium compared with normal conjunctiva. VEGF-C immunoreactivity was detected in the cytoplasm of pterygial and normal conjunctival epithelial cells. The number of VEGF-C-immunopositive cells in pterygial epithelial cells was significantly higher than in normal conjunctival cells (p < 0.05). VEGFR-3 immunoreactivity was localized in the D2-40-positive lymphatic endothelial cells. The present findings suggest the potential role of VEGF-C in the pathogenesis and development of a pterygium through lymphangiogenesis and the VEGF-C/VEGFR-3 pathway as a novel therapeutic target for the human pterygium.

WW Domain Containing Transcription Regulator regulates human conjunctiva epithelial cell proliferation via inhibiting TGFβ signaling pathway [corrected]

PURPOSE

To investigate the role of Tafazzin (TAZ) protein in regulating the proliferation of normal human conjunctiva epithelial cells and epithelial cells from pterygium tissue.

METHODS

Conjunctiva epithelial cells were cultured in keratinocytes growth medium and treated with transformation growth factor β (TGFβ) to analyze the expression and translocation of TAZ protein by immunostaining and BrdU analysis. Immortalized conjunctiva epithelial cells (NHC) were treated with TGFβ, targeting siRNA, TGFβ receptor antibody or TGFβ receptor inhibitor, to study the involvement of TAZ and TGFβ signaling pathway in conjunctiva cell proliferation by cell adhesion assay. Conjunctiva tissues from a normal human eye and an eye with pterygium disease were collected for histological analyses and western blot to evaluate the TAZ protein expression in vivo.

RESULTS

TAZ expression was upregulated in mitotic conjunctiva epithelial cells, proliferating conjunctiva epithelial cells, TGFβ treated conjunctiva epithelial cells and human pterygium epithelium. TAZ siRNA induced less conjunctiva epithelial cell growth. Moreover, TGFβ receptor antibody and TGFβ receptor inhibitor rescued this anti-proliferative effect of TAZ siRNA.

CONCLUSIONS

TAZ is involved in human conjunctiva epithelial cells proliferation via regulating TGFβ signaling pathway.

Expression of cell proliferation and apoptosis biomarkers in pterygia and normal conjunctiva

PURPOSE

To analyze the expression of apoptosis and cell proliferation molecules in pterygium tissues of Chinese patients.

METHODS

Thirty-three pterygia were surgically removed using the bare sclera procedure, and 23 normal bulbar conjunctivas were also obtained. Formalin-fixed, paraffin-wax-embedded tissues were analyzed by immunohistochemistry with anti- proliferating cell nuclear antigen (PCNA), K(i)-67 (a proliferating cell marker), mutant p53 (mP53), Bcl-2 associated X-protein (BAX), B-cell lymphoma gene 2 (Bcl-2), and caspase-3 antibodies. Terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling assay (TUNEL) analysis was used to analyze the apoptotic cells.

RESULTS

Our study revealed that the positive rate of PCNA and K(i)-67 significantly increased in the pterygium samples compared to the normal conjunctiva samples. In the molecules involved in apoptosis, the results showed that the positive rate of Bcl-2 and mP53 significantly increased in the pterygium samples. However, no difference was found between the pterygium and normal conjunctiva samples in the expression of Bax and caspase-3. Through TUNEL analysis, apoptotic cells were seen in the entire width of the epithelial layer in normal conjunctivas but were found mainly confined to the outer layer of the epithelial cells in pterygia.

CONCLUSIONS

The finding of high levels of cellular proliferation and low levels of cellular apoptosis in pterygia confirmed that both cell apoptosis and proliferation are known to play an important role in human pterygium pathogenesis.

Tissue factor expression in human pterygium

PURPOSE

A pterygium shows tumor-like characteristics, such as proliferation, invasion, and epithelial-mesenchymal transition (EMT). Previous reports suggest that tissue factor (TF) expression is closely related to the EMT of tumor cells, and subsequent tumor development. In this study, we analyzed the expression and immunolocalization of TF in pterygial and normal conjunctival tissues of humans.

METHODS

Eight pterygia and three normal bulbar conjunctivas, surgically removed, were used in this study. Formalin-fixed, paraffin-embedded tissues were submitted for immunohistochemical analysis with anti-TF antibody. Double staining immunohistochemistry was performed to assess TF and alpha-smooth muscle actin (α-SMA) or epidermal growth factor receptor (EGFR) expression in the pterygia.

RESULTS

Immunoreactivity for TF was detected in all pterygial tissues examined. TF immunoreactivity was localized in the cytoplasm of basal, suprabasal, and superficial epithelial cells. The number of TF-immunopositive cells in pterygial epithelial cells was significantly higher than in normal conjunctival epithelial cells (p<0.001). TF immunoreactivity was detected in α-SMA-positive or -negative pterygial epithelial cells. EGFR immunoreactivity was detected in pterygial epithelium, which was colocalized with TF.

CONCLUSIONS

These results suggest that TF plays a potential role in the pathogenesis and development of a pterygium, and that TF expression might be involved through EMT-dependent and -independent pathways.

CyclinD1 protein expressed in pterygia is associated with β-catenin protein localization

BACKGROUND

The Wnt (Wg/Wnt) signaling cascade plays an important role in tumorigenesis. Our previous report indicated that aberrant localization of β-catenin proteins was a feature of pterygia. Therefore, this study aimed to analyze the association of β-catenin protein and expression of a downstream gene, cyclin D1, in pterygial tissues.

METHODS

Using immunohistochemistry, β-catenin and cyclin D1 protein expression was studied, in 150 pterygial specimens and 30 normal conjunctivas.

RESULTS

Seventy-three (48.7%) and 60 (40.0%) pterygial specimens tested positive for β-catenin and cyclin D1 protein expression, respectively. Cyclin D1protein expression was significantly higher in β-catenin-nuclear/cytoplasmic positive groups than in β-catenin membrane positive and negative groups (p < 0.0001). In addition, cyclin D1 expression was significantly higher in the fleshy group than in the atrophic and intermediate groups (p = 0.006).

CONCLUSIONS

Our study demonstrated that β-catenin expressed in nuclei/cytoplasm increases cyclinD1 protein expression, which invokes pterygial cell proliferation.

E-cadherin promoter hypermethylation may contribute to protein inactivation in pterygia

PURPOSE

Our recent reports indicated that the molecular changes of pterygia are similar to tumor cells. We believe that pterygia may have a similar mechanism in oncogenesis. Many studies have revealed that E-cadherin associated protein expression decreases in many tumors and pterygia. E-cadherin may be a marker for both tumor metastasis and prognosis. However, no studies have examined the reason for E-cadherin protein inactivation in pterygia. Therefore, this study aimed to analyze the association of E-cadherin promoter hypermethylation with protein inactivation in pterygial tissues.

METHODS

E-cadherin methylation-status and the expression of E-cadherin and beta-catenin protein were studied using methylation-specific PCR and immunohistochemistry, respectively, on 120 pterygial specimens and 30 normal conjunctivas.

RESULTS

Hypermethylation of E-cadherin gene promoter was detected in 32 (26.7%) of the 120 pterygial specimens. A total of 79 (65.8%) pterygial specimens tested positive for E-cadherin protein expression and 41 (34.2%) specimens tested negative. The E-cadherin staining was limited to the membrane of the epithelial layer. There was a reverse correlation between E-cadherin gene promoter hypermethylation and E-cadherin protein expression (p<0.0001). Aberrant localization of beta-catenin was higher in the E-cadherin negative group than in E-cadherin positive group.

CONCLUSIONS

Our study demonstrates E-cadherin gene promoter hypermethylation were associated with low or absent expression of E-cadherin. Moreover, loss of E-cadherin protein may contribute to aberrant localization of beta-catenin. These data provide evidence that methylation exists in pterygia and may play a role in their development.

Study of the expression of CD30 in pterygia compared to healthy conjunctivas

PURPOSE

The pterygium is characterized by a fibrovascular neoformation from the bulbar conjunctiva into the cornea. The recent discovery that abnormal markers associated with tumor diseases are identified in the pterygium strengthens the theory that the pterygium is a tumor-like disease rather than a degenerative disease. The CD30 molecule has been identified in neoplastic and normal epithelial proliferating cells. The aim of this study was to determine the expression of the CD30 molecule in the pterygium.

METHODS

Immunohistochemical staining using an antibody to CD30 and to the Ki-67 nuclear antigen was performed on 25 pterygial specimens and 10 healthy conjunctivas.

RESULTS

Strong immunostaining against CD30 was observed in all pterygium specimens, in contrast to the healthy conjunctivas that showed weak immono-positivity in only three cases. The staining was diffused, predominantly to the basal epithelium. The Ki-67 antigen was observed in the nucleus of the basal epithelium of the pterygial specimens, and no staining was observed in the healthy conjunctiva. When serial sections were stained with CD30 and Ki-67, the cells that expressed CD30 also expressed Ki-67.

CONCLUSIONS

The present study identified for the first time the existence of CD30 molecules in the basal epithelium of a pterygium. The fact that the positivity to Ki-67 in the basal epithelium of the pterygium correlated with the CD30 reactivity suggested that this protein could be associated with the uncontrolled cell proliferation of the epithelium in this pathology. The CD30 molecule could therefore be a suitable target to be inhibited using chimerical antibodies in pterygium diseases.

Phosphorylation of CREB, a cyclic AMP responsive element binding protein, contributes partially to lysophosphatidic acid-induced fibroblast cell proliferation

Lysophospholipids regulate a wide array of biological processes including cell survival and proliferation. In our previous studies, we found that in addition to SRE, CRE is required for maximal c-fos promoter activation triggered by lysophosphatidic acid (LPA). c-fos is an early indicator of various cells into the cell cycle after mitogenic stimulation. However, role of CREB activation in LPA-stimulated proliferation has not been elucidated yet. Here, we investigate how LPA induces proliferation in Rat-2 fibroblast cell via CREB activation. We found that total cell number and BrdU-positive cells were increased by LPA. Moreover, levels of c-fos mRNA and cyclin D1 protein were increased via LPA-induced CREB phosphorylation. Furthermore, LPA-induced Rat-2 cell proliferation was decreased markedly by ERK inhibitor (U0126) and partially by MSK inhibitor (H89). Taken together, these results suggest that CREB activation could partially up-regulate accumulation of cyclin D1 protein level and proliferation of LPA-stimulated Rat-2 fibroblast cells.

Immunolocalisation of E-cadherin and beta-catenin in human pterygium

AIM

The pterygium represents an invasion of a wing of altered ocular surface tissue into the normal cornea. The head itself is slightly elevated and white, which is the only site of firm adhesion to the globe. The mechanisms of cell proliferation and adhesion in pterygium epithelium, however, are unknown. The aim of this study was to analyse the expression of cell adhesion molecules in pterygium tissues.

METHODS

Six pterygia were surgically removed using the bare-sclera procedure, and two normal corneas and a normal bulbar conjunctiva were also obtained. Formalin-fixed, paraffin-embedded tissues were analysed by immunohistochemistry with anti-E-cadherin and beta-catenin antibodies.

RESULTS

Immunoreactivity for E-cadherin was not detected in the normal cornea and conjunctiva. In contrast, all corneal and conjunctival epithelial cells showed a weak homogeneous immunoreaction for beta-catenin on the cell membrane. In the pterygium head, the thickness was relatively marked compared with the body, and normal conjunctival and corneal epithelia. E-cadherin as well as beta-catenin was heterogeneously expressed in the cell membrane and cytoplasm of a variety of epithelial cells, whereas the expression was less marked in the body. Several epithelial cells showed intense nuclear immunoreactivity for beta-catenin. Immunoreactivity of beta-catenin, but not E-cadherin, was detected in only a few stromal cells, which were less marked than in epithelial cells.

CONCLUSION

It is suggested that E-cadherin and beta-catenin are concentrated in pterygium tissue, and are possibly involved with epithelial proliferation and adhesion.