Involvement of microglia in early axoglial alterations of the proximal optic nerve induced by experimental glaucoma

ROSENSTEIN RE; GONZÁLEZ FLEITAS MF; PASQUINI LA; BOSCO A; SANDE PH; DORFMAN D; BORDONE MP

Seattle

Congreso; ARVO Annual Meeting 2016; 2016

PurposeThe progressive degeneration of optic nerve (ON) axonsand retinal ganglion cells (RGCs) in glaucoma is accompanied by glial cell alterations.Wehave developed an experimental model of glaucoma through weekly intracameralinjections of chondroitin sulfate (CS). The aim of this work was to studytheinvolvement of microglial reactivity on the early axoglial alterations of theON in a rat glaucoma model induced by CS.MethodsAdult male Wistarratsreceivedweekly intracameral injections of vehicle or CS up week 15. RGC numberwas analyzed by Brn3a-immunoreactivity. Anterograde transport was examinedafter an intravitreal injection of β-subunit cholera toxin (CTB). Iba1 and ED1(microglial markers), glial fibrillary acidic protein (GFAP, astrocytes), myelinationstatus (luxol fast blue, LFB), and axons (phosphorylated neurofilament heavychain (pNFH))were analyzed in the ON. The involvement of microglial reactivity inON alterations was examined by a daily treatment with minocycline (30 mg/kg,i.p.)for 2 weeks, starting at 4 weeks of intracameralinjections of vehicle orCS.ResultsA significant decrease in Brn3a(+) cell number wasobserved in eyes injected with CS for 10 and 15 (but not 6) weeks.A clearreduction in CTB staining was evident in the superior colliculus (SC) and thelateral geniculate nucleus (LGN) contralateral to CS-injected eyes for 6 and 15weeks.In the ON from eyes that were hypertensive for 6 weeks, a disruption ofCTB transport occurred at the ON proximal myelinated portion. A significantdecrease in pNFH-immunoreactivity,an increase in Iba1(+), ED1(+), and GFAP(+)area, and signs of demyelination were observed at 6 and 15 weeks of ocularhypertension. Minocyclinedid not affect IOP in vehicle-or CS-injected eyes, butit prevented the increase in Iba-1(+), ED-1(+), and GFAP(+) area, and thedecrease inpNFH-immunoreactivity and LFB staining induced by 6 weeks of ocularhypertension. Moreover, minocycline preserved CTB anterograde transport fromthe retina to the SC and LGN.ConclusionThese results support the targeting of microglialreactivity to prevent the early axoglial alterations in the proximal ON.