In situ detection of apoptosis in normal pressure glaucoma: A preliminary examination

Retinal ganglion cell (RGC) neurons are believed to die via apoptosis in hu man primary and secondary open-angle glaucoma. Previous studies have relied solely on the TUNEL. (terminal deoxynucleotidyl transferase-mediated deoxy uridine triphosphate [UTP]-biotin nick end-labeling) method of deterioratin g DNA fragmentation to identify apoptotic nuclei. However, it is now cleat that the TUNEL. method cannot distinguish between tile single- and double-s trand DNA breaks that can be a feature of both apoptosis and necrosis. We h ave developed a double fluorescent labeling method that simultaneously comb ines in situ end-labeling (ISEL) to detect DNA fragmentation followed by st aining with a cyanine dye, YOYO-1, to visualize apoptotic chromatin condens ation. This allows for the unequivocal identification of an apoptotic nucle us. Our preliminary data obtained from one case of normal pressure glaucoma suggests that RGC neurons may die via apoptosis when intraocular pressure is not elevated. (C) 2001 by Elsevier Science Inc. All rights reserved.