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Katerina Jirsova, Sarka Kalasova, Stanislava Merjava; Proteinase Inhibitor Pi-9 Is Expressed In Human Corneal Endothelial Cells. Invest. Ophthalmol. Vis. Sci. 2011;52(14):6440.
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To determine whether proteinase inhibitor 9 (PI-9, known as well as SERPINB 9), which is characteristic of the human mesothelial cell phenotype, is expressed in normal and pathological adult corneas.
Cryosections as well as endothelial, epithelial and conjunctival imprints of human cadaverous corneo-scleral discs and pathological corneas explanted because of corneal melting, rejection or keratitis were used. The expression of PI-9 was examined using fluorescent and enzymatic immunohistochemistry. The staining intensity was assessed using fluorescent or light microscopy, and the percentage of positive cells was calculated from at least two hundred cells. mRNA levels were determined by qRT-PCR.
Weak or moderate immunostaining for PI-9 was observed in the corneal, limbal and conjunctival epithelium of the control tissues, particularly in the superficial and suprabasal layers. The corneal endothelium revealed weak to moderate positivity in approximately 60% of the cells. The staining was localized in the cytoplasm, mostly under the cytoplasmatic membrane. The expression of PI-9 was confirmed using qRT-PCR. Increased numbers and staining intensity of PI-9-positive cells were seen detected in specimens obtained from melted cornea, as well as from corneas suffering from keratitis. In pathological specimens PI-9 was present in stromal infiltrates, where CD8 protein was localized as well.
The expression of PI-9 was analyzed/examined/studied in the normal human cornea as well as in pathological corneas. The presence of this inhibitor of granzyme B and caspases may be involved in maintaining the immunological privilege of the cornea as well as participating in local inflammation.
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