Development and characterization of a new rat ocular hypertension model induced by intracameral injection of conjunctival fibroblasts

Abstract

Glaucoma is a chronic optic neuropathy that leads to visual field loss. Elucidating the mechanisms underlying glaucoma is essential for developing new treatments, such as neuroprotective drugs. Various glaucoma models based on the induction of intraocular pressure (IOP) elevation have been established for use in glaucoma studies. However, the time-dependent pathological changes accompanying IOP elevation have not been fully elucidated. In this study, rat conjunctival fibroblasts were injected into the anterior chamber of rat eyes, and IOP elevation was induced for 28 days. Glaucomatous signs such as optic nerve head cupping, retinal thinning, glial activation and apoptotic signaling in the retina were obvious in the cell-injected eyes on the 14th day after injection. The pattern of retinal ganglion cell (RGC) loss differed by the magnitude of IOP elevation. The number of RGCs decreased by 37.5% in eyes with IOP lower than 50 mmHg (Under-50) and by 88.0% in those with IOP higher than 50 mmHg (Over-50) 28 days after cell injection. The RGC counts were correlated with IOP in the Under-50 group but not in the Over-50 group. Our model may contribute to the investigation of pathogenic mechanisms of glaucoma and the development of new glaucoma treatments.

Systemic Treatment with Nicotinamide Riboside Is Protective in Two Mouse Models of Retinal Ganglion Cell Damage

“…The average IOP of the microbead-injected eyes rose quickly on the second postoperative day, peaked at 8 days, and stayed elevated throughout the following 2–6 weeks, though NR treatment maintained elevation of IOP more so than PBS treatment ( Figure 5 A). The area under the curve (AUC) of IOP change, which takes into account IOP changes over the duration of an experiment ( Figure 5 B), was used as a reflection of ocular hypertension (OHT) [ 49 ]. The AUC significantly increased in both groups that received ocular microbead injections (111,325 ± 5060 IOP AUC for PBS+Microbeads group and 77,892 ± 1089 for NR+Microbeads group) compared to groups that did not receive any ocular injections (81,389 ± 695.4 for Naïve group and 77,892 ± 1089 for NR only group) or received ocular injection of buffer (73,836 ± 1083 for Buffer group; p < 0.05 or less for means of either microbead-injected group versus non-microbead-injected groups) ( Figure 5 C).…”

“…NR supplementation significantly delayed RGC dysfunction and RGC loss at an early stage (3 days) after ONC ( Figure 2 and Figure 3 ). Intracameral microbead injection resulted in sustained IOP elevation and RGC loss spanning two months ( Figure 5 and Figure 6 ) and the two outcomes were correlated ( Figure 7 ), mimicking prevalent forms of glaucoma [ 49 , 61 ]. NR treatment prevented RGC loss across the two-month duration of the experiment and uncoupled the correlation of RGC loss to AUC of IOP change ( Figure 5 , Figure 6 and Figure 7 ), indicating that NR treatment protected RGCs in a relatively chronic model of glaucoma.…”

“…The software gives as output an “area reading” of the selected area. An IOP higher than 50 mmHg may cause ischemic optic neuropathy, which differs from chronic glaucomatous optic neuropathy [ 49 ]. The IOP of the mock-treated mice maintained a normal range.…”

Efficacy, Drug Sensitivity, and Safety of a Chronic Ocular Hypertension Rat Model Established Using a Single Intracameral Injection of Hydrogel into the Anterior Chamber

“…In addition to the well-known and widely used methods, like gene mutation [ 20 ], other methods have become important, such as laser photocoagulation of the trabecular meshwork at the limbus [ 21 , 22 ], episcleral veins injection of hypertonic saline [ 6 , 7 ], occlusion of the episcleral veins by cauterization or suture ligation [ 9 , 23 ], and injection of microbead [ 11 , 24 , 25 ] or hyaluronic acid into the anterior chamber [ 13 ]. Other new rodent COH models, such as circumlimbal suture [ 26 ] and intracameral injection of conjunctival fibroblasts [ 27 ], have also been reported in recent years. However, various challenges also exist with the currently available rodent models.…”

“…This approach avoided introducing foreign materials into the eye, yet the rate of ocular complications was high (71% of eyes showed developed hyphema and 29% showed suture breakage, slippage, or conjunctival tear), with a success rate of only around 50% [ 26 ]. Recently, a novel approach to reliably induce chronic IOP elevation in rats using injection of conjunctival fibroblasts was introduced by Ayumi and colleagues [ 27 ]. The authors were inspired by the clinical occurrence of epithelial downgrowth into the anterior chamber, which is often observed during invasive ocular surgery with a wide corneal incision.…”