Immunohistochemical expression of Fas ligand (FasL) and neprilysin (neutral endopeptidase/CD10) in keratoconus.

Recent evidence demonstrated a correlation between apoptosis and neprilysin expression. The aim of this study was to investigate the immunohistochemical expression of Fas ligand (FasL) and neprilysin in keratoconic corneas in comparison to normal cadaver corneas to evaluate if such molecules play a role in the pathogenesis of keratoconus. We studied the expression of FasL and neprilysin in corneal specimens removed during penetrating keratoplasty in 15 cases with keratoconus and compared them with 5 normal cadaver corneas. In keratoconus, FasL was expressed in epithelium, endothelium and sub-Bowman's stroma only, while neprilysin was expressed in epithelium, endothelium and all stromal layers. All normal corneas showed weak expression of both markers in basal epithelial layer only. In keratoconus, corneal epithelium with higher expression of FasL may evoke apoptosis in keratocytes, while neprilysin could prevent possible rescue of keratocytes from apoptosis.