Cell proliferation and apoptosis in stromal corneal dystrophies

The aim of our study was to evaluate corneal cell proliferation and apoptosis in cases of granular, macular and lattice dystrophy, and to provide evidence which may help to clarify whether apoptosis is a pathogenic factor in any of these dystrophies. The study group comprised 39 eyes (from 33 patients) which had undergone penetrating keratoplasty (PK) for stromal dystrophies: these comprised 12 eyes (from 9 patients, 55.5% males) with granular dystrophy, 13 eyes (12 patients, 33.3% males) with macular dystrophy, and 14 eyes (13 patients, 61.5% males) with lattice type I dystrophy. A further 4 corneal buttons from enucleated eyes of 4 patients with choroideal melanoma served as controls. Immunocytochemical analysis of Ki67 (DNAcon Kit, DakoCytomation A/S, Glostrup, Denmark) was used for evaluation of cell proliferation. Apoptosis was detected by use of the TUNEL (terminal deoxyribonucleotidyl transferase-mediated dUTP-digoxigenin nick-end labelling) assay method (Apoptag reagent, Q-Biogene, Strasbourg, France). Statistical comparisons were made using the Mann-Whitney test. No Ki67-positive cells were detected in the study-group or control corneas. In control corneas no apoptotic activity was found. In the study group the mean (normalised) apoptotic keratocyte number was 1.1+/-1.7 in granular dystrophy and 0.5+/-1.1 in lattice type I dystrophy (p = 0.36, 0.63 respectively). Compared to the controls, the difference was statistically significant only for macular dystrophy (1.6+/-1.2; p = 0.01). Keratocyte apoptosis seems to be a concomitant or pathogenic factor in macular dystrophy. However, the pathways that are triggered to result in increased apoptotic cell death remain to be clarified.