The Key Role of VEGF in the Cross Talk between Pterygium and Dry Eye and Its Clinical Significance

Unravelling the molecular tapestry of pterygium: insights into genes for diagnostic and therapeutic innovations

Pterygium, an ocular surface disorder, manifests as a wing-shaped extension from the corneoscleral limbus onto the cornea, impacting vision and causing inflammation. With a global prevalence of 12%, varying by region, the condition is linked to UV exposure, age, gender, and socioeconomic factors. This review focuses on key genes associated with pterygium, shedding light on potential therapeutic targets. Matrix metalloproteinases (MMPs), especially MMP2 and MMP9, contribute to ECM remodelling and angiogenesis in pterygium. Vascular endothelial growth factor (VEGF) plays a crucial role in angiogenesis and is elevated in pterygium tissues. B-cell lymphoma-2, S100 proteins, DNA repair genes (hOGG1, XRCC1), CYP monooxygenases, p53, and p16 are implicated in pterygium development. A protein-protein interaction network analysis highlighted 28 edges between the aforementioned proteins, except for VEGF, indicating a high level of interaction. Gene ontology, microRNA and pathway analyses revealed the involvement of processes such as base excision repair, IL-17 and p53 signalling, ECM disassembly, oxidative stress, hypoxia, metallopeptidase activity and others that are essential for pterygium development. In addition, miR-29, miR-125, miR-126, miR-143, miR-200, miR-429, and miR-451a microRNAs were predicted, which were shown to have a role in pterygium development and disease severity. Identification of these molecular mechanisms provides insights for potential diagnostic and therapeutic strategies for pterygium.

Risk factors for pterygium: Latest research progress on major pathogenesis

A pterygium is a wedge-shaped fibrovascular growth of the conjunctiva membrane that extends onto the cornea, which is the outer layer of the eye. It is also known as surfer's eye. Growth of a pterygium can also occur on the either side of the eye, attaching firmly to the sclera. Pterygia are one of the world's most common ocular diseases. However, the pathogenesis remains unsolved to date. As the pathogenesis of pterygium is closely related to finding the ideal treatment, a clear understanding of the pathogenesis will lead to better treatment and lower the recurrence rate, which is notably high and more difficult to treat than a primary pterygium. Massive studies have recently been conducted to determine the exact causes and mechanism of pterygia. We evaluated the pathogenetic factors ultraviolet radiation, viral infection, tumor suppressor genes p53, growth factors, oxidative stress, apoptosis and neuropeptides in the progression of the disease. The heightened expression of TRPV1 suggests its potential contribution in the occurrence of pterygium, promoting its inflammation and modulating sensory responses in ocular tissues. Subsequently, the developmental mechanism of pterygium, along with its correlation with dry eye disease is proposed to facilitate the identification of pathogenetic factors for pterygia, contributing to the advancement of understanding in this area and may lead to improved surgical outcomes.

A New Approach: Determination of the Safe Surgical Margin in Pterygium Surgery

PURPOSE

In this retrospective study, we aimed to determine the safe surgical limit for excision of pterygium tissue. Therefore, we aimed to prevent excessive or incomplete normal conjunctival tissue excision during surgery in the coming years.

METHODS

Autografted pterygium surgery was performed between January 2015 and April 2016, and the excised pterygium tissue was examined histopathologically. The files of 44 patients, who had not previously undergone any ocular surgery, who did not have an inflammatory disease and who continued to be checked for at least 1 year, were retrospectively examined. The distance (P-DSEM) from the excised pterygium tissue to the surgical excision margin was measured by a pathologist. Postoperative recurrence rates were evaluated according to this value. In this way, the clean surgical margin was determined.

RESULTS

The mean age of the participants was 44.77 ± 12.70, and the mean follow-up time was 55.61 ± 16.38 months. Recurrence developed in 5 out of 44 patients (11.4%). The average recurrence duration was 51 ± 13.87 days. Distance to the average surgical margin was 3.88 ± 0.91 mm. The surgical distances of 5 patients with recurrence were 2, 2.5, 2, 3, and 3 mm, respectively. It was determined that recurrence was less as the distance (P-DSEM) from the tissue to the surgical excision margin increased (p = 0.001).

CONCLUSIONS

We found that the recurrence rate in pterygium surgery was linked to the clean surgical margin. When planning pterygium surgery, we believe that determining the amount of tissue to be excised before surgery will reduce recurrence rates.

ZD6474 Attenuates Fibrosis and Inhibits Neovascularization in Human Pterygium by Suppressing AKT-mTOR Signaling Pathway

Purpose: To investigate the antifibrotic effect of ZD6474 in human pterygium fibroblasts (HPFs) and angiogenesis in human umbilical vein endothelial cells (HUVECs) compared with mitomycin C (MMC). Methods: Pterygium and tenon fibroblasts were isolated from patients undergoing surgery to culture HPFs and human tenon fibroblasts (HTFs). The effects of ZD6474 on HPF, HTF, and HUVEC proliferation and migration were detected using CCK8 and wound-healing assays, respectively. Fibrosis and epithelial-mesenchymal transformation (EMT) were evaluated by western blotting [transforming growth factor beta (TGF-β)1/2 and snail] and immunofluorescence (vimentin and α-smooth muscle actin). The antiangiogenic effect of ZD6474 on HUVECs was assessed using a tube formation assay. To determine the potential mechanism, the expression of phosphorylated AKT (p-AKT) and phosphorylated mTOR (p-mTOR) was evaluated by treatment with ZD6474 via western blotting. Results: ZD6474 robustly inhibited the proliferation and migration of HPFs rather than HTFs compared with those in the MMC group (**P < 0.01). In HPFs, fibrosis and EMT (vimentin, TGF-β1/2, and snail) were significantly reversed by ZD6474. MMC (>50 μg/mL) significantly reduced HTF viability, whereas ZD6474 (<5 μM/mL) did not decrease HTF viability. HUVEC proliferation and migration were clearly decreased, and tube formation was notably interrupted by ZD6474. Activation of p-AKT and p-mTOR was inhibited by ZD6474 treatment of HPFs and HUVECs. Conclusion: ZD6474 is more effective than MMC in reducing fibrosis and EMT in HPFs. In addition, ZD6474 was less toxic to HTFs. ZD6474 also exhibited antiangiogenic effects in HUVECs. This study may aid in the development of novel agents to prevent pterygium recurrence after pterygium excision.

Application of artificial intelligence models for detecting the pterygium that requires surgical treatment based on anterior segment images

Background and aim

A pterygium is a common ocular surface disease, which not only affects facial appearance but can also grow into the tissue layer, causing astigmatism and vision loss. In this study, an artificial intelligence model was developed for detecting the pterygium that requires surgical treatment. The model was designed using ensemble deep learning (DL).

Methods

A total of 172 anterior segment images of pterygia were obtained from the Jiangxi Provincial People's Hospital (China) between 2017 and 2022. They were divided by a senior ophthalmologist into the non-surgery group and the surgery group. An artificial intelligence model was then developed based on ensemble DL, which was integrated with four benchmark models: the Resnet18, Alexnet, Googlenet, and Vgg11 model, for detecting the pterygium that requires surgical treatment, and Grad-CAM was used to visualize the DL process. Finally, the performance of the ensemble DL model was compared with the classical Resnet18 model, Alexnet model, Googlenet model, and Vgg11 model.

Results

The accuracy and area under the curve (AUC) of the ensemble DL model was higher than all of the other models. In the training set, the accuracy and AUC of the ensemble model was 94.20% and 0.978, respectively. In the testing set, the accuracy and AUC of the ensemble model was 94.12% and 0.980, respectively.

Conclusion

This study indicates that this ensemble DL model, coupled with the anterior segment images in our study, might be an automated and cost-saving alternative for detection of the pterygia that require surgery.

Changes in Tears Monocyte Chemoattractant Protein-1 Level After External Dacryocystorhinostomy in Primary Acquired Nasolacrimal Duct Obstruction

BACKGROUND

The authors aimed to define tears monocyte chemoattractant protein-1 (MCP-1) changes after external dacryocystorhinostomy surgery.

MATERIALS AND METHODS

Tears samples were collected with a Schirmer strip and stored in Eppendorf tubes at -80°C. At the end of the study, the papers were cut into small pieces and incubated with phosphate-buffered saline solution. Monocyte chemoattractant protein-1 levels were determined by using an enzyme-linked immunosorbent assays kit.

RESULTS

The MCP-1 levels were 498.66±101.35, 576.40±149.78, 422.53±85.94, and 436.96±81.38 ng/L before surgery, in the first week, the first, and third months after surgery, respectively. Its level significantly increased in the first week compared with the preoperative level ( P <0.001). There was a prominent decrease in the postoperative first month ( P <0.001). In the third postoperative month, the mean MCP-1 level was not significantly increased compared with the postoperative first month ( P =0.196).

CONCLUSION

The tears MCP-1 level was significantly decreased after external dacryocystorhinostomy surgery.

Porcine Corneas Incubated at Low Humidity Present Characteristic Features Found in Dry Eye Disease

Dry eye is a multifactorial disease that affects the ocular surface and tear fluid. Current treatment options include lubricant eye drop application several times a day. However, these eye drops often cause local side effects like ocular allergies or blurred vision after the application. To test new treatment options, a robust dry eye model is needed. Here, a porcine ex vivo model was established by means of incubation of porcine corneas in low humidity (LH) and characterized by histological damage evaluation, epithelial thickness and by relevant dry eye markers, such as interleukin 1 beta (IL-1β), nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), occludin and galectin-3. In the dry eye model proposed, an increased secretion of IL-1β was observed, as well as an upregulation of NF-κB, occludin and galectin-3 mRNA expression. Moreover, the model presented a higher rate of cell death in comparison to the controls. These effects could be reversed with successful treatment of dexamethasone (dexa) and partially reversed with hyaluronic acid (HA) containing eye drops. Furthermore, medium-molecular-weight HA stimulated an increase in IL-1β in the model proposed. In conclusion, this dry eye model mimics the in vivo condition and hence allows for animal-free testing of novel dry eye treatments.

Rapid 3D bioprinting of a multicellular model recapitulating pterygium microenvironment

Pterygium is an ocular surface disorder with high prevalence that can lead to vision impairment. As a pathological outgrowth of conjunctiva, pterygium involves neovascularization and chronic inflammation. Here, we developed a 3D multicellular in vitro pterygium model using a digital light processing (DLP)-based 3D bioprinting platform with human conjunctival stem cells (hCjSCs). A novel feeder-free culture system was adopted and efficiently expanded the primary hCjSCs with homogeneity, stemness and differentiation potency. The DLP-based 3D bioprinting method was able to fabricate hydrogel scaffolds that support the viability and biological integrity of the encapsulated hCjSCs. The bioprinted 3D pterygium model consisted of hCjSCs, immune cells, and vascular cells to recapitulate the disease microenvironment. Transcriptomic analysis using RNA sequencing (RNA-seq) identified a distinct profile correlated to inflammation response, angiogenesis, and epithelial mesenchymal transition in the bioprinted 3D pterygium model. In addition, the pterygium signatures and disease relevance of the bioprinted model were validated with the public RNA-seq data from patient-derived pterygium tissues. By integrating the stem cell technology with 3D bioprinting, this is the first reported 3D in vitro disease model for pterygium that can be utilized for future studies towards personalized medicine and drug screening.

Decreased retinal microvasculature densities in pterygium

AIM

To investigate the retinal vascular network alterations in eyes of patients with pterygium.

METHODS

Totally 18 left eyes from 18 female pterygium patients and 18 left eyes from 18 female healthy control subjects were enrolled. Optical coherence tomography angiography (OCTA) images were generated of the superficial retinal layer and deeper retinal layer of the macular retina for each eye. The microvascular (MIR) and macrovascular (MAR) densities were calculated and MIR, MAR, and total microvascular (TMI) density was compared in the healthy control and pterygium groups.

RESULTS

In pterygium group, in the superficial retinal layer, the vascular density in superficial MIR, superior right (SR), inferior right (IR), right (R), superficial central annuli (SC)1, SC2, and SC3 decreased significantly in the macular area (P<0.05). Furthermore, the vascular density in all those decreased regions except R, was significantly and negatively correlated with the disease course (r=-0.6038 to -0.7762, P=0.0008), and the area size of pterygium (r=-0.6043 to -0.9508, P<0.05). For the deeper retinal layer, the density of deep total microvessel (DTMI), deeper MIR, SR, IR, R, DC2, and DC3 decreased significantly in macular area of pterygium patients (P<0.05). Furthermore, the vascular density in all those decreased regions was significantly and negatively correlated with the disease course (r=-0.6901 to -0.7795, P=0.0015), and the area size of pterygium (r=-0.6043 to -0.9563, P<0.05). No statistically significant differences and correlation was found in other region density (|r|<0.47, P>0.05).

CONCLUSION

OCTA findings suggest that pterygium patients present with decreased retinal MIR density, and the major vascular alterations occurr mainly on the bitamporal side. The vascular density of the superficial SC1, SC2, SC3 adjacent to the foveal and deep layer of DC2, DC2 regions, significantly decreased.

Efficacy of bevacizumab in the treatment of pterygium: An updated meta-analysis of randomized controlled trials

Recurrence is the most common problem following pterygium surgery. Whether bevacizumab can prevent pterygium recurrence is controversial. To address this point, we carried out a meta-analysis of randomized controlled trials evaluating the efficacy and safety of bevacizumab in the treatment of pterygium. We searched the PubMed, EMBASE, Cochrane Library, Web of Science, Chinese Biomedical Literature, China National Knowledge Infrastructure, and Wan fang databases up to September 20, 2020 for relevant articles. We used the Cochrane assessment tool to evaluate the methodologic quality of the included studies, and calculated the relative risk (RR) and 95% confidence interval (CI) of the reported recurrence and complication rates. A total of 17 studies including 1124 patients with 1144 eyes were included in the meta-analysis. The combined results showed that bevacizumab significantly reduced the recurrence rate of pterygium after surgery (RR = 0.652, 95% CI: 0.504-0.845, Z = 3.24, P = 0.001) and was not significantly associated with the occurrence of postoperative complications compared to control treatments (RR = 0.832, 95% CI: 0.604-1.145, Z = 1.13, P = 0.259). A subgroup analysis showed that the rate of pterygium recurrence was significantly lower with bevacizumab than in the control group at a dose of 2.5 mg (RR = 0.47, 95% CI: 0.24-0.91) administered by subconjunctival injection (RR = 0.54, 95% CI: 0.39-0.75) after a follow-up time of ≤ 6 months (RR = 0.63, 95% CI: 0.45-0.88). Thus, bevacizumab can reduce the risk of pterygium recurrence after surgery, and does not differ from placebo or other drug treatments in terms of the risk of complications.

Pterygium-The Good, the Bad, and the Ugly

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

Lack of HPV in pterygium with no evidence of autoinoculation and the role of cytokines in pterygium with dry eye

This study evaluated human papillomavirus's (HPV) role in pterygium pathogenesis, its autoinoculation from genitalia to ocular surface, potential cytokines involved, and crosstalk cytokines between pterygium and dry eye (DE). This cross-sectional study enrolled 25 healthy controls (HCs) and 116 pterygium patients. Four subgroups of pterygium and DE were used in cytokine evaluations. Conjunctival and pterygium swabs and first-void urine samples (i.e., genitalia samples) were collected for HPV DNA detection using real-time polymerase chain reaction. Tear cytokines interleukin (IL)-6, IL-18, and vascular endothelial growth factor (VEGF) in tears were evaluated. No HPV DNA was detected in conjunctival or pterygium swabs. No association was found between HPV DNA in urine samples and that from conjunctival or pterygium swabs. Tear VEGF levels were significantly higher in pterygium patients than in HCs, with no markedly different levels between primary and recurrent pterygia. Tear IL-6, IL-18, and tear VEGF were significantly higher in participants with DE, regardless of pterygium status. In conclusion, HPV infection was not a pathogenic factor of pterygia. The hypothesis of HPV transmitting from the genitals to ocular surfaces was nullified. Tear VEGF was involved in both pterygia and DE, whereas tear IL-6 and IL-18 played roles only in DE.

Exploring the Molecular Mechanisms of Pterygium by Constructing lncRNA-miRNA-mRNA Regulatory Network

Purpose

This research explores the aberrant expression of the long non-coding RNA (lncRNA), microRNA (miRNA), and messenger RNA (mRNA) in pterygium. A competitive endogenous RNA (ceRNA) network was constructed to elucidate the molecular mechanisms in pterygium.

Methods

We obtained the differentially expressed mRNAs based on three datasets (GSE2513, GSE51995, and GSE83627), and summarized the differentially expressed miRNAs (DEmiRs) and differentially expressed lncRNAs (DELs) data by published literature. Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway, protein-protein interaction (PPI), and gene set enrichment analysis (GSEA) analysis were performed. DEmiRs were verified in GSE21346, and the regulatory network of hub mRNAs, DELs, and DEmiRs were constructed.

Results

Overall, 40 upregulated and 40 downregulated differentially expressed genes (DEGs) were obtained. The KEGG enrichment showed the DEGs mainly involved in extracellular matrix (ECM)-receptor interaction, focal adhesion, and PI3K-Akt signaling pathway. The GSEA results showed that cornification, keratinization, and cornified envelope were significantly enriched. The validation outcome confirmed six upregulated DEmiRs (miR-766-3p, miR-184, miR-143-3p, miR-138-5p, miR-518b, and miR-1236-3p) and two downregulated DEmiRs (miR-200b-3p and miR-200a-3p). Then, a ceRNA regulatory network was constructed with 22 upregulated and 15 downregulated DEmiRs, 4 downregulated DELs, and 26 upregulated and 33 downregulated DEGs. The network showed that lncRNA SNHG1/miR-766-3p/FOS and some miRNA-mRNA axes were dysregulated in pterygium.

Conclusions

Our study provides a novel perspective on the regulatory mechanism of pterygium, and lncRNA SNHG1/miR-766-3p/FOS may contribute to pterygium development.