title: Cystatin C in the anterior segment of rat and mouse eyes.
abstract: OBJECTIVE
  Cystatin C is a mammalian cysteine protease inhibitor. This study describes the localization of cystatin C in the anterior segment of normal rat and mouse eyes. Cysteine proteases play an important role in protein degradation (e.g. of photoreceptor outer segments in the retinal pigment epithelium) and the balance between these proteases and their specific inhibitors is therefore of great interest.
  
  
  METHODS
  Cells containing cystatin C were identified by immunohistochemistry and quantified by ELISA. Messenger RNA levels were analysed by quantitative real-time polymerase chain reaction.
  
  
  RESULTS
  Cystatin C is present at biologically significant levels in the corneal epithelium, endothelium and stromal keratinocytes, lens epithelium, epithelial cells in the ciliary processes, aqueous humour and iris stromal cells. In the rat anterior segment, the highest cystatin C concentrations were found in the ciliary epithelium.
  
  
  CONCLUSIONS
  Cystatin C is present in several cell types and is probably locally produced. The inhibitor is likely to be an important regulator of cysteine proteases in the retinal pigment epithelium, ciliary epithelium, aqueous humour, lens epithelium and in the corneal endothelium and epithelium.
authors.affiliation: Department of Ophthalmology, University of Lund, Sweden. johan.wasselius@oft.lu.se
authors.forename: Johan
authors.initials: J
authors.lastname: Wassélius
authors.forename: Katarina
authors.initials: K
authors.lastname: Håkansson
authors.forename: Magnus
authors.initials: M
authors.lastname: Abrahamson
authors.forename: Berndt
authors.initials: B
authors.lastname: Ehinger
mesh_terms: D000818:Animals; D000869:Anterior Eye Segment / Q000378:metabolism*; D055316:Cystatin C; D015891:Cystatins / Q000235:genetics / Q000378:metabolism*; D015853:Cysteine Proteinase Inhibitors / Q000235:genetics / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D004847:Epithelial Cells / Q000378:metabolism; D019084:Fluorescent Antibody Technique, Indirect; D007498:Iris / Q000378:metabolism*; D007908:Lens, Crystalline / Q000166:cytology / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D010857:Pigment Epithelium of Eye / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: C525031:Cst3 protein, mouse; C525032:Cst3 protein, rat; D055316:Cystatin C; D015891:Cystatins; D015853:Cysteine Proteinase Inhibitors; D012333:RNA, Messenger