Expression of small leucine-rich proteoglycans during experimental fungal keratitis

Abstract

Purpose: To investigate the expression of members of the small leucine-rich proteoglycan family and related leucine-rich repeat proteins during the inception and progression of experimental keratomycosis.

Methods: Scarified corneas of BALB/c mice were topically inoculated with Candida albicans and monitored daily over 1 week for corneal opacification. A murine gene microarray compared infected corneas to controls 1 day postinoculation (PI). Real-time reverse transcriptase polymerase chain reaction determined small leucine-rich proteoglycan gene levels in infected and mock-infected corneas at 1, 3, and 7 days PI and in normal corneas. Immunostaining localized keratocan protein in murine corneas.

Results: Eyes with C. albicans keratitis rapidly developed corneal inflammation with opacification. Microarray showed that genes for biglycan, asporin, lumican, fibromodulin, osteomodulin, keratocan, osteoglycin, and chondroadherin were significantly (P < 0.01) downregulated more than 2-fold at the onset of fungal keratitis. By real-time reverse transcriptase polymerase chain reaction, the gene encoding keratocan was initially downregulated 137-fold and remained downregulated 2.5-fold at 1 week. Genes coding for lumican, osteomodulin, and fibromodulin were downregulated 4- to 9-fold 1 day after fungal inoculation and returned to normal levels by 3 days PI. Immunofluorescence demonstrated that keratocan was present throughout the corneal stroma of normal mice and mock-infected controls but was markedly less during early fungal keratitis.

Conclusions: Transcriptional levels of keratocan and other proteoglycans decrease during the initial stages of C. albicans keratitis. Alterations in the stromal extracellular matrix may contribute to the acute inflammatory response of corneal infection.