Abstract
Abstract: :
Purpose:To test the hypothesis that the aberrant cells on the posterior corneal surface of patients with posterior polymorphous corneal dystrophy (PPCD OMIM, #122000) express proliferative markers and that these cells display corneal epithelial characteristics. Methods:Corneal buttons from four PPCD patients who underwent transplantation and four normal control corneas were used for experiments. Cryosections of 6–8 µm were fixed and indirect immunofluorescent staining was performed. The specimens were stained with antibodies against the proliferation marker Ki–67 and a panel of cytokeratins: CK4, CK14, CK 7, CK18, CK19, CK10/13, and evaluated under a fluorescent microscope (400x). The number of positive cells was scored using a scale from N0 to N4 (N0: 0%, N1: 1–25%, N2: 26–50%, N3: 51–75%, N4: 76–100%). The intensity of the signal was scored as follows: 0– no staining, 1– mild, 2 – moderate, 3 – intense, and 4 – very intense staining. Results:Control epithelium expressed CK 4 (N4/3 superficial and suprabasal layers), CK14 (N4/3 basal and suprabasal layers), CK19 (N1/2), and CK3/12 (N4/2). PPCD epithelium showed the same staining, as did the controls. The endothelial cells of all control corneas were negative for Ki–67 staining. The aberrant PPCD endothelial cells showed N1/2 positivity. The endothelium of all control specimens was negative for all tested cytokeratins. The aberrant PPCD endothelium revealed strong positive staining for cytokeratins 7, 18 and 19 (N4/4) and weak positivity for cytokeratins 4 (N1/2) and 14 (N1/1). PPCD endothelium was completely negative for cytokeratin CK10/13. The cytoplasm of the stromal cells was negative in all examined corneas. Conclusions:We demonstrated that the abnormal endothelium of PPCD patients expresses not only cytokeratins that are abundant (CK4, CK14) or weakly present (CK19) in control corneal epithelium, but also cytokeratins (CK 7, CK 18) not normally present in corneal epithelium. On the other hand, the cytokeratin pair CK10/13, present in the normal corneal epithelium, was not observed in the aberrant PPCD endothelium.
Keywords: cornea: endothelium • immunohistochemistry • cornea: epithelium