Ocular Surface Microbial Flora in Patients with Chronic Limbal Stem Cell Deficiency Undergoing Cultivated Oral Mucosal Epithelial Transplantation

Severity Classification of Limbal Stem Cell Failure Due to Steven Johnson Syndrome in the Light of the Classification Consensus of Limbal Stem Cell Deficiency

OBJECTIVES

To examine and to understand the limbal stem-cell deficiency (LSCD) because of Steven-Johnson syndrome (SJS) in line with the new classification system for the first time in the literature.

METHODS

Medical records of patients with LSCD because of SJS were reviewed retrospectively. In addition to demographic data and ophthalmologic or systemic findings, anterior segment photographs of the patients were reviewed retrospectively. Limbal stem-cell deficiency severity was graded according to the classification published by the Limbal Stem Cell Working Group.

RESULTS

Twenty-four eyes of 14 patients with eye involvement secondary to SJS were included in the study. The mean age of the patients was 36.09±16.70 (9-58) years and the female-to-male ratio was 11:3. The anterior segment photographs of the patients were evaluated by two independent masked observers. Limbal stem-cell deficiency severity was graded according to the classification published by Deng et al. Corneal opacity was divided into three stages according to the area of involvement. Corneal opacity was classified as Stage I if the central 5 mm region of the cornea was not affected, as Stage II if the central 5 mm region of the cornea was affected, and as Stage III if the entire corneal surface was affected. Limbal involvement was classified as Stage A if it was below 50%, as Stage B if it was between 50% and 100%, and as Stage C if it was 100%.

CONCLUSION

This is the first study in the literature to describe and classify LSCD because of SJS, according to the new LSCD classification. Consistent with the results, LSCD follows a bimodal distribution. Most patients demonstrated severe (Stage III-32.14%) or mild (Stage IA-21.42%) LSCD.

The Ocular Microbiome in Stevens-Johnson Syndrome

The ocular surface microbiome is an essential factor that maintains ocular surface homeostasis. Since the ocular surface is continuously exposed to the external environment, its microbiome, tears, and local immunity are vital for maintaining normal conditions. Additionally, this microbiome helps prevent pathogen colonization, which commonly leads to opportunistic infection. The abnormal ocular surface microbiome has previously been reported in several conditions, including dry eyes, allergy, blepharitis, graft-versus-host disease (GVHD), and Stevens-Johnson syndrome (SJS). Several approaches were applied to identify the ocular microbiome, including conventional culture techniques and molecular sequencing techniques. By using 16s rRNA sequencing, alterations in the type, proportion, and composition of bacterial communities, described by alpha (α)-and beta (β)-diversity, were observed in SJS patients compared to the healthy group. Conventional culture techniques indicated a higher number of positive bacterial cultures in the SJS group, with a predominance of gram-positive cocci and gram-positive bacilli. Besides, there are increased variations and multiple detections of bacterial genera. Taken together, SJS causes structural changes in the ocular surface and significantly affects its microbiome. Further studies into the area of temporal relationship, metagenomics, proteomics, and metabolomics analysis of the microbiome will lead to a better understanding of this disease. Finally, the treatment using prebiotics and probiotics to re-establish the normal ocular ecosystem and bring back a healthy ocular surface await confirmation.

Ocular Surface Microbiome in Health and Disease

The ocular surface is exposed continuously to the environment and, as a consequence, to a variety of different microbes. After the results of the Human Microbiome Project became publicly available, international research groups started to focus interest on exploring the ocular surface microbiome and its physiopathological relationship to the eye. For example, numerous research studies the existence of the ocular surface's bacterial flora, typically gathering cultures from healthy patients and finding few variations in the bacterial species. More recently, culture-independent methods, including 16S ribosomal ribonucleic acid (rRNA) gene sequencing, are being used to define the ocular microbiome. These newer methods suggest that the microbial communities have a greater diversity than previously reported. These communities seem to serve an immune-modulating function and maintain relationships with other microbes and organs, even distant ones. This review summarizes the literature exploring the ocular microbiome, both in health and in different diseases.

Ex vivo cultivated oral mucosal epithelial cell transplantation for limbal stem cell deficiency: a review

Destruction or dysfunction of limbal epithelial stem cells (LESCs) leads to unilateral or bilateral limbal stem cell deficiency (LSCD). Fifteen years have passed since the first transplantation of ex vivo cultivated oral mucosal epithelial cells (COMET) in humans in 2004, which represents the first use of a cultured non-limbal autologous cell type to treat bilateral LSCD. This review summarizes clinical outcomes from COMET studies published from 2004 to 2019 and reviews results with emphasis on the culture methods by which grafted cell sheets were prepared.