A subacute model of glaucoma based on limbal plexus cautery in pigmented rats

Abstract

Glaucoma is a neurodegenerative disorder characterized by the progressive functional impairment and degeneration of the retinal ganglion cells (RGCs) and their axons, and is the leading cause of irreversible blindness worldwide. Current management of glaucoma is based on reduction of high intraocular pressure (IOP), one of its most consistent risk factors, but the disease proceeds in almost half of the patients despite such treatments. Several experimental models of glaucoma have been developed in rodents, most of which present shortcomings such as high surgical invasiveness, slow learning curves, damage to the transparency of the optic media which prevents adequate functional assessment, and variable results. Here we describe a novel and simple method to induce ocular hypertension in pigmented rats, based on low-temperature cauterization of the whole circumference of the limbal vascular plexus, a major component of aqueous humor drainage and easily accessible for surgical procedures. This simple, low-cost and efficient method produced a reproducible subacute ocular hypertension with full clinical recovery, followed by a steady loss of retinal ganglion cells and optic axons, accompanied by functional changes detected both by electrophysiological and behavioral methods.

Neuroprotective Gene Therapy by Overexpression of the Transcription Factor MAX in Rat Models of Glaucomatous Neurodegeneration

“…In the present study, we tested the neuroprotective effect of rAAV2- MAX ex vivo and extended our study of neuroprotection to in vivo rat models of RGC degeneration, induced either by optic nerve crush (ONC) or by an ocular hypertension (OHT) model of limbal plexus cautery. 44 Our results provide proof of principle for rAAV2- MAX as a tool for neuroprotective gene therapy in glaucoma through prevention of RGC degeneration and preservation of optic nerve axons.…”

“…To test for neuroprotection in an experimental setting more akin to human glaucoma, we examined the effects of MAX overexpression in a model of subacute OHT, produced by limbal plexus cautery in rats. 44 One-month-old rats received intravitreal injections of 3 µL rAAV2- MAX or rAAV2- GFP (10 9 vg/µL) and were subject to OHT 1 month later. Increased IOP, typically observed between D1 and D5 in this model, was not altered by either injection of rAAV2 or overexpression of the transgene and progressively returned to normal values at D7 (see Supplementary Fig.…”

“…The procedure followed the protocol described in Lani et al 44 Briefly, rats at 2 months old were deeply anesthetized with an intramuscular injection of ketamine hydrochloride (75 mg/kg) and xylazine hydrochloride (5 mg/kg), as well as topical eye anesthesia with proxymetacaine hydrochloride 0.5%. A low-temperature ophthalmic cautery (Bovie Medical Corporation, Clearwater, FL, USA) was used to cauterize the limbal plexus in a 360° ring around the cornea, visualized through a stereomicroscope at 40× magnification.…”

“…The procedure followed the protocol described in Lani et al 44 The cornea was topically anesthetized with a drop of proxymetacaine hydrochloride 0.5%, and the active electrode (a stainless-steel needle 0.25 × 15 mm; Hansol Medical Co., Seoul, Republic of Korea) was inserted carefully at the temporal periphery of the transitional zone. The reference and ground electrodes were stainless-steel needles (0.4 × 37 mm; Chalgren Enterprises, Gilroy, CA, USA), positioned subcutaneously into the ipsilateral temporal canthus and the left hindlimb, respectively.…”