Retinotopic glial alterations on the Superior Colliculus in an experimental model of glaucoma

BORDONE MP; PASQUINI LA; ROSENSTEIN RE

Orlando, Florida

Congreso; 2014 ARVO Annual Meeting; 2014

Association for Research in Vision and Ophthalmology (ARVO)

Purpose:The Superior Colliculus (SC) is a primary projection site of the rat retina, and its superficial layer contains a complete retinal topographical representation. We have developed an experimental model of glaucoma in rat through intracameral injections of chondroitin sulfate (CS), which mimics central features of human glaucoma. The aim of this work was to study the effects of ocular hypertension on the SC structure. Methods:Male Wistar rats were weekly injected with vehicle or CS in the eye anterior chamber. The number of retinal ganglion cells (RGC) was assessed by Brn3a immunohistochemistry. Anterograde transport was examined by an intravitreal injection of cholera toxin β-subunit (CTB). In the SC, immunohistochemical analysis for Iba1, ED1, and GSA (microglia), platelet-derived growth factor receptor-α (PDGFRα), receptor-interacting protein (RIP), O1, and myelin basic protein (MBP) (oligodendrocytes), GFAP (astrocytes), RGC axonal terminal marker vesicular glutamate transporter 2 (Vglut2) and neuron specific protein (NeuN) was performed. Lipids in the SC were assessed by Red Oil staining. In addition, the number of TUNEL(+) was assessed in the SC. Results:At 6 weeks of ocular hypertension, a significant decrease in the anterograde transport to the SC, and an increase of Iba1, RIP and O1 levels, Iba1(+) and PDGFRα(+) cell number in the lateral portion of the SC, without changes in RGC number, were observed. At 15 weeks of treatment, Brn3a(+) cell number significantly decreased, CTB transport to the SC was completely abolished, RIP and O1 levels remained increased, and the microglial response augmented and progressed through the medial SC, accompanied by the presence of ED1-phagocytic cells. The number of TUNEL(+) cells in the SC significantly increased at 6 and 15 weeks of ocular hypertension. In contrast, Vglut2 immunoreactivity and NeuN(+) cell number remained unchanged. A pronounced astroglial response (GFAP) was evident in the whole SC at 15 (but not 6) weeks of hypertension. MBP immunoreactivity was unchanged at both time points, but there was an apparent loss in Red Oil staining at 15 weeks of ocular hypertension. Conclusions:These results suggest a retinotopic misconnection between the retina and the SC accompanied by early apoptotic events and oligodendrocyte and microglial response in the lateral SC at early stages of ocular hypertension.