Abstract
Purpose: :
The purpose of this study was to elucidate the detailed expression pattern of angiogenesis–related factors in the transitional zone between corneal epithelium (CE) and conjunctival epithelium (CJE). We focused on factors with significantly higher gene expression in the CE than CJE.
Methods: :
We compared the relative gene expression of 36 angiogenesis–related factors in the human CE and CJE using the introduced amplified fragment–length polymorphism (iAFLP) method. For factros with significantly higher expression in the CE, we examined the expression patterns in the CE, limbal epithelium (LE), and CJE using real–time PCR, in situ hybridization, immunohistochemistry, and immunoelectron–microscopy.
Results: :
Only thrombospondin–1 (TSP–1) exhibited significantly higher expression in the CE. In situ hybridization showed TSP–1 transcripts in the basal cells of the CE and LE, and real–time PCR revealed they were significantly up–regulated compared to that of the CJE . Immunohistochemistry revealed that TSP–1 was strongly expressed in the basal region of the CE; its expression was faint in the LE and absent in the CJE. Immunoelectron–microscopy revealed that the CE and LE demonstrated TSP–1 labeling just below the epithelium and in the basal region of basal cells. The labelling in the LE was less than that of the CE. There was little or no labeling in the CJE.
Conclusions: :
In the human ocular surface epithelium, basal cells of the CE and LE, but not the CJE, synthesize TSP–1. In contrast to the LE, TSP–1 accumulates in Bowman’s layer just below the CE; its unique distribution may be related to corneal avascularity and integrity. Investigations on the role of TSP–1 in the ocular surface epithelium are needed.
Keywords: cornea: basic science • neovascularization • cornea: epithelium