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J.A. Wasselius, K. Håkansson, M. Abrahamson, B. Ehinger; Cystatin C in the Anterior Segment of Rat and Mouse Eye . Invest. Ophthalmol. Vis. Sci. 2003;44(13):417.
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Purpose: Cystatin C is a mammalian protease inhibitor regulating certain cysteine proteases. Little is known about cystatin C in the anterior segment of the eye. This study describes its localization in the anterior segment of rat and mouse eyes. Methods: In normal adult rat and mouse eyes, cystatin C-containing cells were identified by immunohistochemistry. The inhibitor was quantified in anterior segment tissues by ELISA, and its production sites were assessed by quantitative mRNA analyses, using real-time RT-PCR. Results: Cystatin C is present in the subcapsular epithelium of the lens, the epithelium, the endothelium and the stromal keratinocytes of the cornea, the epithelial cells on the ciliary processes as well as in cells in the iris. Cystatin C appears to be present in the entire cytoplasm of these cells. The highest levels of cystatin C were found in the ciliary body, and at levels comparable with those in the retina. The levels of cystatin C mRNA were also the highest in the ciliary body, in accordance with the protein analyses. Conclusions: Cystatin C is produced by, and present in, several of the well-defined epithelial cell types of the anterior segment of rat and mouse eye. The protein concentration, as measured by ELISA, as well as the mRNA concentration (measured by RT-PCR), were highest in the ciliary body, suggesting that the epithelial cells of the ciliary processes may produce and secrete relatively large amounts of cystatin C to the aqueous humor. From there, it may be taken up by lens epithelial cells or corneal endothelial cells, or it may act as a cysteine protease regulator in the aqueous pathways.
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