Clinical and Cytologic Evidence of Limbal Stem Cell Deficiency in Eyes With Long-Standing Vernal Keratoconjunctivitis

Clinical, histological and immunohistochemistry characteristics of cornea in the sequelae stage of chronic vernal keratoconjunctivitis

Purpose:

To report the clinical outcomes and histopathological and immunohistochemistry (IHC) features in eyes with the sequelae stage of vernal keratoconjunctivitis (VKC).

Methods:

Investigative study of corneal samples obtained following surgical intervention for vision restoration in four eyes of three patients with VKC. Patient 1 (an 11-year-old boy) had deep anterior lamellar keratoplasty in both eyes, Patient 2 (a 24-year-old male) underwent superficial keratectomy followed by penetrating keratoplasty, and Patient 3 (a 22-year-old male) underwent penetrating keratoplasty. The corneal samples retrieved after surgical intervention were assessed for histology features and immunohistochemistry (IHC) studies.

Results:

The grafts were clear till the follow-up of 2–18 months. Histopathology of all four corneal samples showed epithelial hyperplasia, absent Bowman layer, thick hyalinized stromal lamellae, vascularization, and chronic inflammatory cells such as lymphocytes and plasma cells. IHC showed strong expression of CK 3 in both eyes of Patient 1 and no expression in Patients 2 and 3. The marker for limbal stem cells, ABCG2, was absent in all four samples; however, p63α was expressed strongly in Patients 2 and 3, moderately in the right eye of Patient 1, and marginally expressed in the left eye of Patient 1.

Conclusion:

The eyes in the sequelae stage of VKC (having corneal scarring and 360° hypertrophied limbus) can be managed favorably with keratoplasty and amniotic membrane transplantation without allogenic/cadaveric stem cell transplantation. The expression of transient progenitor cells in the scarred corneas of VKC patients in the sequelae stage suggests that the limbal stem cell dysfunction is more likely partial and self-renewal of limbal stem cells is a plausibility in these eyes.

Adult vernal keratoconjunctivitis

PURPOSE OF REVIEW

Vernal keratoconjunctivitis (VKC) is a rare chronic self-limiting allergic inflammatory disease of the ocular surface mostly affecting young boys in their first decade of life. In the last few years a new clinical entity of VKC has been described: adult VKC. Two variants have been identified according to clinical onset: early (childhood VKC persisting beyond puberty) and late onset (arising de novo in adults) adult VKC. Several epidemiologic studies on VKC have been published from single tertiary centers but while the age distribution of VKC patients does show a small percentage of adults with the disease, detailed analysis on this small subset of adult VKC cases is lacking. In this review we describe pathogenesis, clinical features, diagnostic alternatives, and therapeutic alternatives of this highly invalidating disease.

RECENT FINDINGS

Adult variants of VKC have same clinical manifestations of classic form, but show higher inflammatory response and increased risk of chronic fibrotic sequelae.

SUMMARY

Adult VKC research could provide insights on the impact of sex hormones in the pathogenesis of allergic diseases and on the mechanisms of inflammation and fibrosis, which cause potentially vision threatening sequelae. The present review will highlight the recent developments in our understanding of this uncommon entity.

Immunopharmacology in Vernal Keratoconjunctivitis: Current and Future Perspectives

Vernal keratoconjunctivitis (VKC) is a complex and chronic, multifactorial Th2 cell-mediated chronic ocular surface inflammatory condition that typically affects predominantly male children in hot or warm climates. The primary symptom is intense ocular pruritus, often significant enough to affect activities of daily living. Clinical features differ from simple forms of allergic conjunctivitis in that they are more-or-less confined to the superior tarsus and limbus. There is also a risk of corneal involvement, which leads to irreversible vision loss in approximately 6% of patients. Right now, there is no standardized treatment protocol, and many of the currently available options are not effective in severe and recurrent cases. As such, it is imperative to understand this complex allergic immune response in order to identify future therapeutic targets. This review will focus on potential drug targets in VKC, with particular emphasis on immunomodulators and immunobiologic agents.

"Doughnut" Amniotic Membrane Transplantation With Penetrating Keratoplasty for Vernal Keratoconjunctivitis With Limbal Stem Cell Disease

PURPOSE

Severe vernal keratoconjunctivitis (VKC) can cause ocular surface disease including partial or complete limbal stem cell deficiency (LSCD), especially in early-onset and severe limbal form of VKC. We report a novel technique of doughnut amniotic membrane transplantation (AMT) along with penetrating keratoplasty (PK) for management of partial LSCD and corneal scarring in a case of severe VKC.

METHODS

Case report.

RESULTS

A 17-year-old boy, with onset of disease at 8 years of age, and development of partial LSCD and corneal scarring over a period of 9 years despite therapy, presented with profound visual loss due to dense bilateral corneal scarring. After the active allergy subsided, he underwent modified AMT (doughnut AMT) with simultaneous PK in his left eye. Histopathology of the excised button revealed conjunctival phenotype and dense corneal scarring up to the posterior stroma. At 1-year follow up, his best spectacle-corrected visual acuity was maintained at 20/30 in the operated eye, the graft was clear, and the ocular surface was stable.

CONCLUSIONS

Severe VKC can cause ocular surface disease including LSCD with corneal scarring, especially in early-onset limbal form of VKC. The modified technique of AMT (doughnut AMT) along with PK can successfully visually rehabilitate and address partial LSCD in such patients.

Histopathological Characteristics of Limbal Stem Cell Deficiency Secondary to Chronic Vernal Keratoconjunctivitis

PURPOSE

To describe the histopathological characteristics of limbal stem cell deficiency (LSCD) due to chronic vernal keratoconjunctivitis (VKC).

METHODS

This retrospective study included 14 eyes of 13 patients who underwent simple limbal epithelial transplantation for total LSCD from 2017 to 2018. The histological characteristics of the excised fibrovascular pannus were compared between 2 groups of 7 eyes, each with LSCD due to VKC and chemical burns (CB). Histological characteristics and type of inflammation were studied using special stains and immunohistochemistry. Fisher exact test was used to detect the statistical significance of the histological differences between both groups.

RESULTS

Epithelial hypertrophy, epithelial downgrowth, and eosinophilic infiltration were noted in all eyes in the VKC group (7/7, 100%). Epithelial hypertrophy was noted in 3 of the 7 (42.8%) eyes in the CB group, whereas epithelial downgrowth and eosinophilic infiltrates were absent. The average chronic inflammatory score of the pannus (5.28) was higher in VKC than in CB (3.85; P = 0.1080). The presence of goblet cells was higher in the CB group (5/7, 1.4%) than in the VKC group (3/4, 2.8%), although not statistically significant. Other histological differences between the groups were not statistically significant.

CONCLUSIONS

The histopathological features of LSCD in VKC reveal some distinctive characteristics. These include the presence of epithelial downgrowth, eosinophilic infiltration, and epithelial solid and cystic implants. Although this information may be used to establish the diagnostic criteria for VKC as the cause of LSCD, further studies are needed to elucidate the reasons behind these unique findings.

Systemic diseases and the cornea

There is a number of systemic diseases affecting the cornea. These include endocrine disorders (diabetes, Graves' disease, Addison's disease, hyperparathyroidism), infections with viruses (SARS-CoV-2, herpes simplex, varicella zoster, HTLV-1, Epstein-Barr virus) and bacteria (tuberculosis, syphilis and Pseudomonas aeruginosa), autoimmune and inflammatory diseases (rheumatoid arthritis, Sjögren's syndrome, lupus erythematosus, gout, atopic and vernal keratoconjunctivitis, multiple sclerosis, granulomatosis with polyangiitis, sarcoidosis, Cogan's syndrome, immunobullous diseases), corneal deposit disorders (Wilson's disease, cystinosis, Fabry disease, Meretoja's syndrome, mucopolysaccharidosis, hyperlipoproteinemia), and genetic disorders (aniridia, Ehlers-Danlos syndromes, Marfan syndrome). Corneal manifestations often provide an insight to underlying systemic diseases and can act as the first indicator of an undiagnosed systemic condition. Routine eye exams can bring attention to potentially life-threatening illnesses. In this review, we provide a fairly detailed overview of the pathologic changes in the cornea described in various systemic diseases and also discuss underlying molecular mechanisms, as well as current and emerging treatments.

Management of corneal complications in vernal keratoconjunctivitis: A review

Vernal keratoconjunctivitis (VKC) is a chronic, bilateral, allergic conjunctivitis with episodes of acute exacerbations. Although VKC has a self-limiting course, chronic recurrent inflammation can cause long-term visual impairment due to corneal complications including shield ulcers, infectious keratitis, keratoconus, corneal opacities, and limbal stem cell deficiency. The initial step in the management of corneal involvement is medical treatment of the acute stage of VKC and prevention of recurrences. Giant papillae not responding to medical treatment can be removed surgically in the case of corneal involvement. Shield ulcer with no inflammatory plaque usually heals with appropriate medical therapy. For shield ulcer with inflammatory plaque, however, surgical debridement with or without amniotic membrane transplantation might be necessary. Keratoconus may develop in chronic and severe VKC. An annual evaluation of these patients with corneal topography and/or tomography is essential for early detection of keratoconus and its timely management that includes collagen cross-linking and intrastromal corneal ring segment implantation. Corneal transplantation may be required in the advanced stage of keratoconus. Both penetrating keratoplasty and deep anterior lamellar keratoplasty can result in excellent visual outcomes in keratoconic eyes with concomitant VKC. Appropriate management of inflammation in the perioperative period is crucial for achieving successful outcomes after corneal transplantation. Limbal stem cell deficiency, a rare complication of long-standing and severe VKC, might be treated with living-related conjunctival limbal allograft.

Mast Cells Populate the Corneoscleral Limbus: New Insights for Our Understanding of Limbal Microenvironment

Purpose

Although stem cell activity represents a crucial feature in corneal and ocular surface homeostasis, other cells populating this region and the neighboring zones might participate and influence local microenvironment. Mast cells, the long-lived and tissue-sited immune cells, have been previously reported in corneoscleral specimens. Herein, mast cells were investigated in corneoscleral tissues and related to microenvironment protein expression.

Methods

Twenty-six (14 male/12 female; older than 60 years) human corneoscleral specimens were sectioned for light and fluorescent immunostaining (CD45, p63, Ck-3/7/12/19, tryptase/AA1, and chymase/CC1). Corneal, limbal, and conjunctival squares were produced for molecular and biochemical analysis. Statistical comparisons were carried out by ANOVA.

Results

Toluidine blue staining identified metachromatic intact or degranulated mast cells in the area below the palisades' Vogt (Ck-3/12-positive epithelium and underneath p63 immunoreactivity). Tryptase immunoreactivity was observed close to palisades' Vogt, whereas no specific signal was detected for chymase. Tryptase/AA1 transcripts were quantified in limbal and conjunctival RNA extracts, whereas no specific amplification was detected in corneal ones. Few mediators were overexpressed in limbal extracts with respect to corneal (Neural cell adhesion molecule (NCAM), Intercellular adhesion molecule 3 (ICAM3), Brain-derived Neurotrophic factor (BDNF), and neurotrophin 3 (NT3); P < 0.00083) and conjunctival (NCAM, ICAM3, and NT3; P < 0.05) protein extracts. A trend to an increase was observed for Nerve Growth Factor (NGF) in limbal extracts (P > 0.05).

Conclusions

The specific observation of tryptase phenotype and the interesting protein signature of microenvironment (adhesion molecules, growth factors, and neurotrophins), known to partake mast cell behavior, at least in other areas, would provide additional information to better understand this crucial zone in the framework of ocular surface healthiness.

Management of ocular allergy

The treatment and management of ocular allergy (OA) remain a major concern for different specialties, including allergists, ophthalmologists, primary care physicians, rhinologists, pediatricians, dermatologists, clinical immunologists, and pharmacists. We performed a systematic review of all relevant publications in MEDLINE, Scopus, and Web Science including systematic reviews and meta-analysis. Publications were considered relevant if they addressed treatments, or management strategies of OA. A further wider systematic literature search was performed if no evidence or good quality evidence was found. There are effective drugs for the treatment of OA; however, there is a lack an optimal treatment for the perennial and severe forms. Topical antihistamines, mast cell stabilizers, or double-action drugs are the first choice of treatment. All of them are effective in reducing signs and symptoms of OA. The safety and optimal dosing regimen of the most effective topical anti-inflammatory drugs, corticosteroids, are still a major concern. Topical calcineurin inhibitors may be used in steroid-dependent/resistant cases of severe allergic keratoconjunctivitis. Allergen-specific immunotherapy may be considered in cases of failure of first-line treatments or to modify the natural course of OA disease. Based on the current wealth of publications and on the collective experience, recommendations on management of OA have been proposed.

Insulin-like growth factor binding protein-7: A marker of conjunctivalization in an animal model of limbal stem cell deficiency

PURPOSE

Limbal stem cell deficiency (LSCD) is characterized by the loss of limbal epithelial stem cells, resulting in a pathological process termed 'conjunctivalization' which compromises corneal transparency, leading to blindness. Current diagnosis for LSCD is limited because reliable conjunctiva-specific biomarkers are lacking. This study sought to address this shortcoming through the serendipitous discovery of insulin-like growth factor binding protein (IGFBP)-7.

METHODS

IGFBP-7 expression was determined in normal (n=83) and conjunctivalized (n=52) mouse corneas with experimentally-induced LSCD, and in cadaveric normal human corneas (n=7) and human pterygia (n=15); a disease characterized by the invasion of a conjunctivalized, fibrovascular pannus. Clinical assessments including slit-lamp microscopy, fluorescein staining and impression cytology, and biochemical, molecular and immunological assays were also conducted.

RESULTS

Mass spectrometry of conditioned media from mouse limbal explant-derived cells revealed the presence of IGFBP-7. This factor was expressed in normal limbal and conjunctival epithelium and conjunctivalized corneas from mice with LSCD, and in human pterygium epithelium but not in normal mouse or human corneal epithelium. Four weeks after inducing LSCD, IGFBP-7 staining was increased by 2.9-fold in mouse corneas compared to steady-state, and by 1.6-fold in impression cytology specimens derived from the same mice. Notably, IGFBP-7 was detected approximately 2-weeks earlier than Muc5AC.

CONCLUSIONS

This study provides novel insights into the specificity of IGFBP-7 for the mammalian conjunctival epithelium in health and disease. A point-of-care test for IGFBP-7 could be developed to assist clinicians in early diagnosis, and in monitoring disease progression, severity and therapeutic outcomes in patients with LSCD.

Vernal keratoconjunctivitis: culmination of management using immunosuppression, surgical and prosthetic therapy over quarter century

A 22-year-old male patient presented in 1988 with active vernal keratoconjunctivitis. He was treated with topical mast cell stabilisers and corticosteroids. Chronic inflammation despite topical treatment necessitated oral immunosuppressants. Active disease came under control with this; however, the patient gradually developed limbal stem cell deficiency. He underwent bilateral pannus resection with amniotic membrane transplantation that resulted in improved ocular surface. In 2007, patient was found to have significant bilateral posterior subcapsular cataracts and underwent bilateral cataract surgery with intraocular lens implantation with good visual outcome. In 2016, he was provided with scleral lens prosthetic device, which further improved vision. At last follow-up, more than 25 years after his initial visit, his visual acuity was 20/25 in both eyes with a stable surface. With a comprehensive approach using immunosuppression, surgical therapy and scleral lens prosthetic device, chronic vernal keratoconjunctivitis can be well managed as illustrated in this case.

Corneal complications of vernal keratoconjunctivitis

PURPOSE OF REVIEW

Vernal keratoconjunctivitis (VKC) is a severe bilateral chronic allergic inflammatory disease of the ocular surface. In most of the cases, the disease is limited to the tarsal conjunctiva and to the limbus. However, in the more severe cases, the cornea may be involved, leading to potentially sight threatening complications. Prompt recognition of these complications is crucial in the management of VKC, which is one of the most severe ocular allergic diseases.

RECENT FINDINGS

A vicious cycle of inflammation occurs as a result of a set of reciprocal interactions between the conjunctiva and the cornea, which results in damage to the corneal epithelium and corneal stoma, and to the formation of shield ulcers and plaques, infectious keratitis, keratoconus, scarring, and limbal stem cell deficiency. These corneal complications can cause permanent decrease or loss of vision in children suffering from VKC.

SUMMARY

Corneal complications in VKC are the result of an on-going process of uncontrolled inflammation. Proper recognition of the corneal complications in VKC is crucial, as most of these can be managed or prevented by a combination of medical and surgical measures.