Cytokine-Induced Calgranulin C Expression in Keratocytes

The authors have identified a corneal stromal protein (CO-Ag) that may be involved in the pathogenesis of Moorenʹs ulcer. The CO-Ag cDNA sequence is identical to that of human neutrophil calgranulin C (CaGC). This study sought to demonstrate expression of the CaGC gene in the human cornea and in corneal keratocytes after cytokine stimulation.In situhybridization and immunohistochemistry were used to localize CaGC mRNA and protein in normal and diseased human corneas, including a specimen with Moorenʹs ulcer. Cultured bovine keratocytes were stimulated with IL-1α or TNF-α, and reverse transcription polymerase chain reaction (RT–PCR) was performed to amplify CaGC cDNA from cytokine-stimulated keratocytes and unstimulated controls. Southern blotting verified the specificity of the RT–PCR amplification products.In situhybridization detected human CaGC mRNA in the stroma of corneas with Fuchsʹ dystrophy, postinfection corneas, and a cornea with Moorenʹs ulcer. In cultured bovine keratocytes, peak levels of CaGC mRNA were reached 6 h after cytokine stimulation. Southernblots with an oligonucleotide probe specific forCaGC detected the RT–PCR products of expected sizes (273 bp) and confirmed that the amplifiedCO-Ag sequence was identical to that of CaGC. These studies are the first to demonstrate the presence of CaGC in the human cornea and the ability of stromal keratocytes to produce CaGC (CO-Ag). The up-regulation of CaGC gene expression by corneal keratocytes due to proinflammatory cytokines from trauma or inflammation may induce autoimmunity that ultimately results in Moorenʹs ulceration.