Limbal Stem Cell Deficiency in the Context of Autoimmune Polyendocrinopathy

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.

Limbal stem cell diseases

The function of limbal stem/progenitor cells (LSCs) is critical to maintain corneal epithelial homeostasis. Many external insults and intrinsic defects can be deleterious to LSCs and their niche microenvironment, resulting in limbal stem cell dysfunction or deficiency (LSCD). Ocular comorbidities, frequent in eyes with LSCD, can exacerbate the dysfunction of residual LSCs, and limit the survival of transplanted LSCs. Clinical presentation and disease evolution vary among different etiologies of LSCD. New ocular imaging modalities and molecular markers are now available to standardize the diagnosis criteria and stage the severity of the disease. Medical therapies may be sufficient to reverse the disease if residual LSCs are present. A stepwise approach should be followed to optimize the ocular surface, eliminate the causative factors and treat comorbid conditions, before considering surgical interventions. Furthermore, surgical options are selected depending on the severity and laterality of the disease. The standardized diagnostic criteria to stage the disease is necessary to objectively evaluate and compare the efficacy of the emerging customized therapies.

Limbal stem cell defficiency associated with primary adrenocortical insufficiency

Objective: To report a female patient with bilateral limbal stem cell deficiency (LSCD) due to primary adrenocortical insufficiency (PAI).

Methods: Case report

Results: A 40-year-old female patient had blurry vision, foreign body sensation, tearing, and photophobia for several years. On examination, corneal epithelial haze, surface irregularity, and superficial neovascularization were observed. There was a dull and irregular reflex from the conjunctivalized corneal surface. Medical history revealed that she had a diagnosis of PAI for 11 years and received hormone replacement (fludrocortisone acetate) therapy. With the clinical presentation and examination, the diagnosis was compatible with LSCD. Frequent ocular lubricant and topical steroid drops were initially started and topical cyclosporine treatment was planned for the long term. After 3 weeks, there was no corneal superficial neovascularization and epithelial haze, peripheral stromal haze was still observed.

Conclusion: LSCD may rarely be associated with PAI. In patients with LSCD, systemic evaluation should be made to rule out PAI.

Limbal epithelial cell therapy: past, present, and future

The cornea, the clear window at the front of the eye, transmits light to the retina to enable vision. The corneal surface is renewed by stem cells located at the peripheral limbal region. These cells can be destroyed by a number of factors, including chemical burns, infections, and autoimmune diseases, which result in limbal stem cell deficiency (LSCD), a condition that can lead to blindness. Established therapy for LSCD based on ex vivo expanded limbal epithelial cells is currently at a stage of refinement. Therapy for LSCD is also rapidly evolving to include alternative cell types and clinical approaches as treatment modalities. In the present perspectives chapter, strategies to treat LSCD are discussed and advances in this important field of regenerative medicine are highlighted.

Spontaneous T cell mediated keratoconjunctivitis in Aire-deficient mice

BACKGROUND/AIMS

Patients with autoimmune polyendocrinopathy-candiasis-ectodermal dystrophy (APECED) develop severe keratoconjunctivitis, corneal scarring and visual loss, but the precise pathogenesis is unknown. This study evaluated the ocular surface immune cell environment, conjunctival goblet cell density and response to desiccating environmental stress of the autoimmune regulatory (Aire) gene knockout murine model of APECED.

METHODS

Aire-deficient and wild type (WT) mice were subjected to desiccating stress from a drafty, low-humidity environment and pharmacological inhibition of tear secretion for 5 days. Immune cell populations (CD4(+), CD8(+), CD11b(+), CD45(+)) and goblet cell density were measured in ocular surface tissues and meibomian glands, and compared with baseline values.

RESULTS

Greater CD4(+) T cell populations were observed in the conjunctival epithelium of Aire-deficient mice (p<0.001) compared with WT. Aire-deficient mice also had greater numbers of CD4(+), CD8(+), and CD11b(+) cells in the peripheral cornea at baseline and following desiccating stress. The meibomian glands of Aire-deficient mice demonstrated greater CD4(+), CD8(+), CD45(+) and CD11b(+) cells at baseline (p<0.001) and following desiccating stress. Conjunctival goblet cell density was lower at baseline and following desiccating stress in Aire-deficient compared with WT mice (p<0.001).

CONCLUSION

Aire-deficiency leads to infiltration of CD4(+) and CD8(+) T cells on the ocular surface and meibomian glands, which is accompanied by goblet cell loss. Desiccating stress promotes this proinflammatory milieu. Immune-mediated mechanisms play a role in the severe blepharitis and keratoconjunctivitis in the murine model of APECED.