Limbal epithelial stem-microenvironmental alteration leads to pterygium development

Abstract

Maintenance of tissue homeostasis relies on the accurate regulation of tissue specific stem cell activity which is governed by the dynamic interaction between the positive and negative feedback modulating mechanism of stem cell microenvironmental niche. Alteration or deregulation of the "stem-microenvironmental networking" provokes disease development. Limbal epithelial stem cells (LESC) are the initiator hierarchy that maintains corneal integrity. Compartmentalization of LESC within the limbal vicinity provides an opportunity to understand the stem-microenvironmental relationship. The purpose of this study was to determine the microenvironmental alteration associated with LESCs fate in pterygium condition in comparison with healthy state. Clinical observations evaluated the ocular surface disorder with respect to corneal vascularization, tear film abnormality, and thickening of limbal area in pterygium patients. Structural alteration of limbal stem/progenitor cells and its neighboring niche components were observed using histology and scanning electron microscopy. Receptor overexpression of TGFβ-R1, EGF-R1, and IL6-Rα and alteration of IL2-Rα expression pointed toward aberration of "stem-microenvironmental networking" in the limbal vicinity during disease development. Increased cell proliferation index along with TERT, Cyclin-D1, and PCNA over-expression in limbal part of pterygium epithelial cells indicated increased cellular proliferation and disturbed homeostatic equilibrium. We postulate that pterygium is associated with limbal microenvironmental anomaly where the resident epithelial cells became hyperproliferative.