Endothelial progenitor cells in pterygium pathogenesis

Are Periocular and Systemic Allergy Conditions Risk Factors for Pterygium?

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Comparative Transcriptomic Analysis to Identify the Important Coding and Non-coding RNAs Involved in the Pathogenesis of Pterygium

Pterygium is a common ocular surface disease characterized by abnormal fibrovascular proliferation and invasion, similar to tumorigenesis. The formation of tumors is related to a change in the expression of various RNAs; however, whether they are involved in the formation and development of pterygium remains unclear. In this study, transcriptome analysis of messenger RNAs (mRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs) of paired pterygium and normal conjunctiva was performed to explore key genes regulating the development of pterygium. In total, 579 mRNAs, 275 lncRNAs, and 21 circRNAs were differentially expressed (DE) in pterygium compared with paired conjunctival tissues. Functional enrichment analysis indicated that DE RNAs were associated with extracellular matrix organization, blood vessel morphogenesis, and focal adhesion. Furthermore, through protein-protein interaction network and mRNA-lncRNA co-expression network analysis, key mRNAs including FN1, VCAM1, and MMP2, and key lncRNAs including MIR4435-2HG and LINC00968 were screened and might be involved in the pathogenesis of pterygium. In addition, several circRNAs including hsa_circ_0007482 and hsa_circ_001730 were considered to be involved in the pterygium development. This study provides a scientific basis for elucidating the pathogenesis of pterygium and will be beneficial for the development of preventive and therapeutic strategies.

Evaluation of the systemic inflammation in patients with pterygium: Monocyte-to- high-density lipoprotein cholesterol ratio and hematologic indexes of inflammation

PURPOSE:

The purpose of this study is to evaluate systemic inflammation in patients with pterygium using the monocyte-to-high-density lipoprotein cholesterol ratio (MHR) and hematologic indexes of inflammation.

METHODS:

Thirty-one patients with primary pterygium and 31 age-and sex-matched healthy participants were enrolled in this retrospective study. The MHR, neutrophil-to-lymphocyte ratio (NLR), monocyte-to-lymphocyte ratio, platelet-to-lymphocyte ratio, eosinophil-to-lymphocyte ratio, monocyte-to-eosinophil ratio, mean platelet volume-to-platelet count ratio, platelet distribution width, and red cell distribution width were compared between the two groups.

RESULTS:

There was not a statistically significant difference in terms of the MHR between the pterygium group and the control group (P = 0.693). The NLR was higher in the pterygium group than in the control group (P = 0.028). In the other hematologic indexes, there were no statistically significant differences between the two groups (P > 0.05 for all).

CONCLUSION:

The MHR is not associated with the presence of pterygium. An increased NLR in patients with pterygium may be an indicator of systemic inflammation.

Does systemic inflammation play a role in patients with pterygium?

PURPOSE

To compare parameters of systemic inflammation and serum lipid levels in patients with pterygium versus healthy individuals.

METHODS

Thirty-five patients with pterygium and 30 healthy individuals were enrolled as two respective groups in a retrospective study. The participants' complete blood count (CBC) parameters and levels of serum total cholesterol, low-density lipoprotein, high-density lipoprotein (HDL), and triglycerides (TG) were obtained from digital records and compared. Their neutrophil/lymphocyte, platelet/lymphocyte, and monocyte/HDL ratios were calculated and compared as well. As secondary outcomes, longitudinal length (LL), basal length (BL), and total area (TA) of pterygium among the patients were quantitatively measured by using ImageJ software. Correlations between serum parameters and pterygium measurements were analyzed.

RESULTS

Although between-group differences in CBC parameters and the ratios were not statistically significant, HDL levels were significantly lower (p = 0.014) and TG levels significantly higher (p = 0.031) among patients with pterygium than among the controls. A positive correlation was detected between the patient's age and the pterygium's BL (p = 0.002, r = 0.516), LL (p = 0.00, r = 0.547), and TA (p = 0.00, r = 0.515). Neutrophil levels negatively correlated with LL (p = 0.025, β = - 0.308) and TA (p = 0.002, β = - 0.420).

CONCLUSION

Local instead of systemic inflammation should be considered in the management of pterygium. Besides, decreased HDL levels may indicate systemic oxidative stress in patients with the condition.

Management of primary pterygium with intra-lesional injection of 5 flurouracil and bevacizumab (Avastin)

BACKGROUND

To assess the efficacy of combined 5FU and Avastin injections in the treatment of primary pterygium METHODS: Sixteen eyes with primary pterygium received intralesional 5 fluorouracil and Avastin (2.5-5 mg) injections every 2 weeks for a maximum of five injections. Fourteen eyes of 14 patients received five injections, one eye received three injections and one eye received two injections. All eyes were followed at monthly intervals for 3 months after last injection. Tissue was obtained by surgical excision of primary pterygium from four eyes who received injections and three eyes with primary pterygium who did not receive injections (control) and subjected to immunohistological examination for beta fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGF), epidermal growth factor (EGF), von-Willebrand factor (vWF), lymphatic vessel endothelial hyaluronan receptor (LYVE-1) and collagen-I.

RESULTS

Pterygium progression was arrested in all patients. Sixty-two percent of patients had improvement of redness while 89% had reduced thickness of the lesion. VEGF, bFGF, EGF, vWF, LYVE-1 and collagen-I were all reduced in the injected samples.

CONCLUSIONS

The injection of 5 fluorouracil and Avastin act synergistically to arrest progression and induce atrophy in primary pterygium. This is related to the effect of agents on fibroblasts, collagen, and vascular tissues. Such medical intervention is a safe and viable option in the management of primary pterygium though excision of residual tissue is still required in some cases. Longer follow up is needed to ascertain whether this will reduce the recurrence rate following excision.

Association between Serum Immnunoglobulin E and Pterygium: A Population-Based Study from South Korea

PURPOSE

Several studies have shown that pterygium is associated with inflammation, angiogenesis, and fibrosis. However, it should be acknowledged that not enough is known about the association between immunoglobulin E (IgE) and pterygium. The present study was conducted to test the hypothesis that elevated serum IgE is associated with a greater prevalence of pterygium.

MATERIAL AND METHODS

A cross-sectional study was performed using data of 1,548 participants aged 30 years or older who were enrolled in the Korea National Health and Nutrition Examination Survey conducted in 2010. Multivariable logistic regression analysis was used to examine the relationship between pterygium and allergic conditions, including total serum IgE and allergen-specific serum IgE levels, after adjusting for potential confounding factors.

RESULTS

Participants with pterygium were more likely have increased IgE level (p = 0.009). After adjusting for potential confounders, the odds ratio (OR) for pterygium was greater in participants with higher total serum IgE levels (OR = 1.63; p = 0.047). Multivariable-adjusted ORs of pterygium across the tertile of increasing IgE were 1.00 (reference), 1.18, and 1.45, (P for linear trend = 0.038). Although the ORs for the upper two tertiles of cockroach and dog allergen-specific IgE were higher than those for the lowest tertile, allergen-specific serum IgE showed no clear association with pterygium.

CONCLUSIONS

Increased total serum IgE concentration is independently related to pterygium after adjusting for confounding factors. To the best of our knowledge, this study is the first research that reveals an association between serum IgE and pterygium.

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.

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.

Evaluation of stem cell components in retrocorneal membranes

The purpose of this study was to elucidate the origin and cellular composition of retrocorneal membranes (RCMs) associated with chemical burns using immunohistochemical staining for primitive cell markers. Six cases of RCMs were collected during penetrating keratoplasty. We examined RCMs with hematoxylin and eosin (H&E), periodic acid-Schiff (PAS) staining and immunohistochemical analysis using monoclonal antibodies against hematopoietic stem cells (CD34, CD133, c-kit), mesenchymal stem cells (beta-1-integrin, TGF-β, vimentin, hSTRO-1), fibroblasts (FGF-β, α-smooth muscle actin), and corneal endothelial cells (type IV collagen, CD133, VEGF, VEGFR1). Histologic analysis of RCMs revealed an organized assembly of spindle-shaped cells, pigment-laden cells, and thin collagenous matrix structures. RCMs were positive for markers of mesenchymal stem cells including beta-1-integrin, TGF-β, vimentin, and hSTRO-1. Fibroblast markers were also positive, including FGF-β and α-smooth muscle actin (SMA). In contrast, immunohistochemical staining was negative for hematopoietic stem cell markers including CD34, CD133 and c-kit as well as corneal endothelial cell markers such as type IV collagen, CD133 except VEGF and VEGFR1. Pigment-laden cells did not stain with any antibodies. The results of this study suggest that RCMs consist of a thin collagen matrix and fibroblast-like cells and may be a possible neogenetic structure produced from a lineage of bone marrow-derived mesenchymal stem cells.

Anterior segment uses of bevacizumab

PURPOSE OF REVIEW

A significant recent advancement in the treatment of neovascularization of the anterior segment of the eye is the development of antivascular endothelial growth factor (anti-VEGF) therapeutic agents.We present a review of the current knowledge on anti-VEGF therapy with bevacizumab for anterior segment neovascularization.

RECENT FINDINGS

A review of the recent peer-reviewed literature reveals an increasing number of experimental and clinical studies on the use of Avastin in both human and animal eye models. Although the numbers are still relatively small, the evidence suggests that bevacizumab may be effective in the treatment of corneal and iris neovascularization. Its effect on primary and recurrent pterygium is more controversial. In general, achievement of vessels regression is usually partial, and recurrence may occur after cessation of treatment. Response to treatment is affected by the chronicity of vessels, their extent, the cause for blood vessels formation, and the route of administration.

SUMMARY

Effective short-term response together with high patient tolerance to local bevacizumab therapy offer encouraging results for the management of anterior segment neovascular disorders. Although statistically significant regression of vessels has been documented in many studies, the clinical significance of this finding is still a subject of debate.

Single and multiple injections of subconjunctival ranibizumab for early, recurrent pterygium

Purpose

To assess the effect of single versus multiple subconjunctival ranibizumab injections in patients with an early pterygium recurrence.

Setting

Single-center, academic practice.

Study population

Nine patients with early pterygium recurrence.

Observational procedure

Subconjunctival ranibizumab (0.5 mg/0.05 mL) was administered adjacent to pterygium recurrence. Group 1 (n = 5) received one injection; group 2 (n = 4) received three injections (time points 0, 2, and 4 weeks) with the ability to retreat as needed.

Main outcome measures

Effect of ranibizumab on conjunctival hyperemia and corneal neovascular area over a 6-month follow-up period.

Results

In the single injection group, a decrease in conjunctival hyperemia was noted in all patients on postinjection day 1. At follow up, hyperemia grade fluctuated, although all patients had less hyperemia than at baseline. In the recurrent injection group, the median number of injections was 8.5 (range 7 to 9) over the 6 months. In spite of the repeated injections, the pattern of conjunctival hyperemia was similar to that of the single injection group. In group 1, corneal neovascularization remained relatively unchanged over the 6-month period in four patients and decreased in one patient by 24%. In group 2, corneal neovascularization increased in one patient by 39%, remained stable in one patient, and decreased in two patients by 34% and 44%.

Conclusion

This is the first study to evaluate the role of ranibizumab in the treatment of an early pterygium recurrence and the first to compare multiple versus single injections. Recurrent injections did not appear to be superior to a single injection with regards to conjunctival hyperemia.

A randomized controlled trial of intralesional bevacizumab injection on primary pterygium: preliminary results

PURPOSE

To evaluate the efficacy and safety of intralesional injection of bevacizumab on primary pterygium treatment.

METHODS

In this randomized controlled trial, each primary pterygium patient was randomized to receive either an intralesional injection of bevacizumab 2 mg (1 mg/0.04 mL) or a combination of topical antihistamine (antazoline HCl 0.05%) and vasoconstrictor (tetrahydrozoline HCl 0.04%) as a control. The main outcome measurements were symptoms and signs (including eye irritation, epiphora, redness, amount of discharge, inflammation and elevation of pterygium, and percentage of corneal pterygium area).

RESULTS

A total of 74 pterygium eyes in 66 patients were randomized and allocated into a treatment group (N = 34) and a control group (N = 40). In the treatment group, there was a statistically significant reduction of symptoms (including irritation, photophobia, epiphora, redness, discharge, and blurred vision) and signs (inflammation and corneal pterygium area) compared with the baseline, up to at least 6 months. Between the treatment and control groups, no significant differences were found for all visits with respect to the (1) symptoms, (2) signs, and (3) percentage of corneal pterygium.

CONCLUSIONS

Intralesional bevacizumab may have a therapeutic effect on symptoms and signs of primary pterygium for at least 6 months (ie, the follow-up period), with no serious ocular or systemic adverse effects.

[Expression of embryonic markers in pterygium derived mesenchymal cells]

BACKGROUND

Destruction of the limbal epithelium barrier is the most important mechanism of pterygium formation (conjunctiva proliferation, encroaching onto the cornea). It is thought to arise from activated and proliferating limbal epithelial stem cells. The objective of this study is to evaluate the presence of undifferentiated mesenchymal cells (stem cells) in cultured cells extracted from human pterygium.

MATERIAL AND METHODS

Cells from 6 human pterygium were isolated by explantation and placed in cultures with amniomax medium. Once the monolayer was reached the cells were seeded onto 24 well microplates. The cells were studied in the second sub-culture. The immunohistochemical expression of different embryonic stem cell markers, OCT3/4 and CD9, was analysed. The differentiated phenotypes were characterised with the monoclonal antibodies anti-CD31, α-actin and vimentin.

RESULTS

All the cell populations obtained from pterygium showed vimentin expression. Less than 1% of the cells were positive for CD31 and α-actin markers. The majority of the cell population was positive for OCT3/4 and CD9.

CONCLUSIONS

The cell population obtained from pterygium expressed mesenchymal cell phenotype and embryonic markers, such us OCT3/4 and CD9. This undifferentiated population could be involved in the large recurrence rate of this type of tissue after surgery.

Phase I study of subconjunctival ranibizumab in patients with primary pterygium undergoing pterygium surgery

PURPOSE

To evaluate the safety and tolerability of ranibizumab given via subconjunctival injection in patients with primary pterygium undergoing pterygium surgery with autograft placement.

DESIGN

Prospective, open-label pilot study.

METHODS

SETTING

Single-center, academic practice.

STUDY POPULATION

Ten patients with primary pterygia.

OBSERVATIONAL PROCEDURE

Subconjunctival ranibizumab (0.5 mg/0.05 mL) administered at the limbus, adjacent to pterygium either 3 days prior to surgery (Group 1, n = 5) or at the time of surgery (Group 2, n = 5). Patients prospectively followed for 6 months after injection.

MAIN OUTCOME MEASURES

Safety and tolerability of subconjunctival ranibizumab as determined by patient reporting, clinical examination, and masked observer interpretation of slit-lamp photographs.

RESULTS

The median age at presentation was 59 years (range 33 to 71 years); 60% of patients were male. Five patients were randomly assigned to be injected with 0.05 mg ranibizumab via subconjunctival injection 3 days prior to surgery; an additional 5 patients were injected with ranibizumab at the time of surgery. All 10 patients tolerated the injection well. The conjunctival autograft remained intact in the 9 patients whose grafts were secured with sutures. There was dehiscence of the autograft in the 1 patient whose graft was secured with fibrin glue. No other safety concerns arose after 6 months of follow-up. Three pterygium recurrences were noted at 6 months (all patients in Group 1). All remaining patients had a normal surgical bed appearance.

CONCLUSIONS

The data from this small pilot study suggest that 1 subconjunctival injection of ranibizumab in conjunction with pterygium surgery is well tolerated.

Efficacy of topical bevacizumab for inhibiting growth of impending recurrent pterygium

PURPOSE

To evaluate clinical outcome(s) and complication(s) of topical bevacizumab (avastin) in patients with impending recurrent pterygium.

PATIENTS AND METHODS

This prospective clinical trial included 54 consecutive patients (54 eyes), who underwent pterygium surgery with bare sclera and mitomycin, and who were diagnosed with impending recurrent pterygium. Of the 54 patients, 26 received eye drops containing bevacizumab (5 mg/ml) twice a day and betamethasone four times daily for 1 week. In the other 28 patients, betamethasone alone was administered four times daily for 1 week. Follow-up times were 3-6 mos.

RESULTS

All patients in both groups failed, i.e., fibrovascular tissue (pterygia) eventually extended onto the cornea. However, in patients receiving topical bevacizumab, the mean progression of fibrovascular tissue extension during the first week, first month, and third month of follow-up was significantly less than that in the control group (p < 0.01). The mean duration for invasion of cornea in study group patients was significantly longer than that for control group patients (p < 0.01).

CONCLUSION

Short-term use of topical bevacizumab seems to be a safe and effective means for delaying recurrence of impending recurrent pterygia.

The change of cytokines in tear and blood after different pterygium operation

Pterygium is an invasion of altered ocular tissue into the cornea. Bone marrow-derived stem cells have been reported to be involved in wound healing under chemotactic factors after pterygium removal and pain may act as a trigger signal. We evaluated the change of systemic and local chemotactic factors that could affect the mobilization and migration of BMSCs to the wound bed after conventional bare sclera pterygium excision. We also applied temporary amniotic membrane patch after pterygium removal, and compared the changes of cytokines with those of conventional bare sclera excision group. Substance-P (SP), vascular endothelial growth factor (VEGF), and stem cell factor (SCF) were measured in plasma and tear using ELISA and migrating CD34(+) cells by flow cytometry. The results showed that post-operative pain was much reduced (p<0.05), and SP, VEGF and SCF kept consistently lower levels in plasma after temporary amniotic membrane application. Circulating CD34(+) cells increased slightly in the temporary amniotic membrane patch group compared with marked increase in the bare sclera group. Thus, the application of a temporary amniotic membrane after pterygium removal might be an effective therapeutic means by controlling pain and excessive infiltration of bone marrow-derived stem cells.

Subconjunctival bevacizumab injection for corneal neovascularization in recurrent pterygium

PURPOSE

We report on the use of subconjunctival bevacizumab on corneal vessel density in recurrent pterygia.

METHODS

The charts of 5 patients with recurrent pterygium, who received subconjunctival injections of bevacizumab (2.5 mg/0.1 ml) were retrospectively reviewed. Ophthalmic evaluation included Snellen visual acuity (VA), tonometry and complete examination before the injection and at 1 week and 1 and 3 months thereafter. Digital photographs of the eyes were analyzed by image analysis software to determine the area of cornea covered by new vessels as a percentage of the total corneal area.

RESULTS

No ocular or systemic adverse events were observed. No change in visual acuity was noted in any patient following the injection. The mean change in corneal vascularization after one bevacizumab injection was 0.03%+/-0.45, while after two injections the change was 0.025%+/-0.19 (both not statistically different than zero, t-test).

CONCLUSIONS

Short-term results suggest that subconjunctival bevacizumab is well tolerated but does not cause regression of corneal vessels in recurrent pterygium.