Hyperproliferative Corneal Epithelium Expresses Proinflammatory Molecules That Recruit Neutrophils to the Cornea of corn1 Mice

Abstract

Purpose:: Corneal disease-1 (corn1) mice are deficient in destrin (actin depolymerizing factor) and develop corneal epithelial hyperproliferation, followed by corneal stromal neovascularization. Gene expression studies identified factors associated with angiogenesis and inflammatory cell chemotaxis as upregulated in the cornea of corn1 mice. These include Cxcl5, which is angiogenic and plays a role in leukocyte chemotaxis, and Ceacam1, also an angiogenic factor. Neutrophil invasion was observed in corn1 cornea just prior to the initiation of neovascularization. The purpose of this study was to determine the expression pattern of these molecules and the effect of CXCL5 and other ligands for its receptor, Interleukin 8 receptor beta (IL8RB), on the recruitment of neutrophils or neovascularization in corn1 cornea.

Methods:: We tested the expression pattern of CXCL5 and CEACAM1 by immunohistochemical analyses in wild type and corn1 cornea. We generated corn1 mice homozygous or heterozygous for the targeted allele of Il8rb (corn1/corn1 Il8rb+/- and corn1/corn1 Il8rb-/-). Inflammatory cells and blood vessels were labeled by immunohistochemical methods. We quantified the number of neutrophils in corneal sections as well as the neovascularization in whole mount corneas.

Results:: Immunohistochemical analyses demonstrate that CXCL5 and CEACAM1 are both upregulated in corn1 epithelium at the onset of neovascularization. Both proteins are also expressed by neutrophils recruited to the corn1 cornea. The absence of the IL8RB receptor in corn1 mice resulted in a 66% decrease in the number of neutrophils recruited to the cornea. Neovascularization was not inhibited in mice with a reduced number of neutrophils in the cornea.

Conclusions:: The epithelial layer of the cornea in corn1 mice spontaneously expresses angiogenic and chemotactic factors. Ligands of the IL8RB receptor, including CXCL5, play a major role in neutrophil recruitment to corn1 cornea but are not necessary for neovascularization.

Keywords: cornea: basic science • inflammation • neovascularization