Abstract
Abstract: :
Purpose: Erythropoietin (EPO) has been reported to have neuroprotective effects in ischemic models involving brain neurons. The aim of this study was to evaluate the effects of a single intravitreal dose of EPO on intraocular pressure (IOP) and retinal apoptotic activity in a cautery–induced rat glaucoma model. Methods: Three episcleral veins were cauterized in the right eye of adult male Sprague Dawley rats. The intact left eyes served as controls. The animals were randomly divided into one of three treatment groups: cautery only, cautery with EPO treatment, and cautery with PBS injection. A single dose of 5ul EPO (200ng) or the same volume of PBS was delivered intravitreally into the eye prior to the cautery procedure. Intraocular pressures were measured (Tonopen XL) before surgery and on days 7, 14, and 21 post–operatively. The retinal ganglion cells (RGCs) were labeled retrogradely by FluoroGold (FG), injected into the superior colliculus in the rat brain 7 days before eye enucleation. The FG–labeled RGCs were examined in whole flat–mounted retinas and automatically quantified using the KS 400 program with fluorescence microscopy. The extent of apoptosis in retina was assessed by the TUNEL assay in cryo–sections. Results: The mean IOP in normal SD rats was 23.18 + 2.8 mmHg. The IOP level was elevated 23∼32% from baseline in both cautery and cautery with PBS groups on day 7, but increased only13% in the cautery with EPO group. No other significant difference in IOP was observed among the groups at the other time intervals. The number of RGCs in whole–mounted retinas did not differ in EPO treated eyes on day 21 when compared to eyes in the PBS–treated and cautery only groups. On day 21 in all 3 groups, apoptosis was not readily detected in the RGC layer, while the TUNEL positive reactions were seen primarily in the nuclei of the INL and ONL cells. Conclusions: Our preliminary results suggest that a single intravitreal dose of EPO may limit IOP elevation in experimental glaucomatous eyes and last for a minimum of 7 days. Further studies are needed to optimize the dose and duration of EPO delivery in exploring its potential neuroprotective properties in glaucomatous optic neuropathy.
Keywords: intraocular pressure • apoptosis/cell death • retina