Evaluation of Bleb Characteristics after Trabeculectomy and Glaucoma Implant Surgery in the Rabbit

The characteristics of the conjunctival bleb are some of the most important factors for the surgical success of glaucoma filtering surgery. To improve surgical outcome, we investigated bleb histology after 3 different glaucoma surgeries. Surgery was performed in 21 white rabbits. Rabbits were randomized to trabeculectomy or implantation with EX-PRESS or a silicone tube (each n = 7). Bleb survival, intraocular pressure (IOP), and vascularity were evaluated. At 6 weeks, eyes were enucleated for histological analysis. Postoperative IOP at 2 weeks was significantly lower in the trabeculectomy and the EX-PRESS group than in the silicone tube group (p = 0.037) but not thereafter. Postoperative bleb survival (p = 0.542) and vascularity (p = 0.988) were similar among the 3 groups. Histologically, a capsule showing mild fibroblast proliferation associated with intercellular collagen was present around the surgical site. The thickness of the bleb was similar among all experimental groups, but it was significantly greater than in controls (p < 0.05). The inflammatory area did not differ between the EX-PRESS and the silicone tube group but was significantly greater in the trabeculectomy group than in the tube group (p = 0.031). A correlation between the thickness of the bleb wall and inflammation was found (r = 0.56, p < 0.01). EX-PRESS and silicone tube implants appear to be relatively inert, with little difference in biocompatibility and bleb survival. Since some degree of inflammation was still observed histologically in the bleb, more noninvasive surgical methods and more biocompatible materials may be desirable.

Toll-like receptor 4 inhibitor protects against retinal ganglion cell damage induced by optic nerve crush in mice

Toll-like receptor 4 (TLR4) plays key roles in innate immune responses and inflammatory reactions. TAK-242 (resatorvid) is a small-molecule cyclohexene derivative that selectively inhibits TLR4 signaling pathways and suppresses inflammatory reactions. Here we investigated the protective effects of TAK-242 against optic nerve crush (ONC) which induces axonal injury like glaucoma in mice. TAK-242 was injected intravitreally immediately after ONC. The effect of TAK-242 was evaluated by measuring the number of fluorogold-labeled retinal ganglion cells (RGCs) at 10 days after ONC. Furthermore, the expression levels of phosphorylated-nuclear factor-kappa B (p-NF-κB) and phosphorylated-p38 (p-p38) were measured by Western blotting. In addition, we examined activated astrocytes by immunostaining. TAK-242 significantly abrogated the loss of RGCs associated with ONC. Moreover, the expression levels of p-NF-κB and p-p38 were significantly reduced by TAK-242 treatment. Furthermore, TAK-242 and C34, a TLR4 inhibitor, significantly reduced astrocyte activation in the ganglion cell and inner plexiform layers, compared with vehicle treatment. These findings indicate that TAK-242 inhibits not only the TLR4 signaling pathway but also astrocyte activation downstream of this pathway, suggesting that the inhibition of TLR4 signaling is a promising candidate for the treatment of glaucoma.

Astaxanthin Protects Against Retinal Damage: Evidence from In Vivo and In Vitro Retinal Ischemia and Reperfusion Models

PURPOSE

Astaxanthin exhibits various pharmacological activities, including anti-oxidative, anti-tumor, and anti-inflammatory effects, and is thought to exert a neuroprotective effect via these mechanisms. The purpose of this study was to investigate the protective effects of astaxanthin on neuronal cell death using a retinal ischemia/reperfusion model.

METHODS

In vivo, retinal ischemia was induced by 5 h unilateral ligation of the pterygopalatine artery (PPA) and the external carotid artery (ECA) in ddY mice. Astaxanthin (100 mg/kg) was administered orally 1 h before induction of ischemia, immediately after reperfusion, at 6 or 12 h after reperfusion, and twice daily for the following 4 days. Histological analysis and an electroretinogram (ERG) were performed 5 days after ischemia/reperfusion. In vitro, cell death was induced in the RGC-5 (retinal precursor cells) by oxygen-glucose deprivation (OGD), and the rates of cell death and production of intracellular reactive oxygen species (ROS) were measured using nuclear staining and a ROS reactive reagent, CM-H₂DCFDA.

RESULTS

Histological studies revealed that astaxanthin significantly reduced retinal ischemic damage and ERG reduction. In in vitro studies, astaxanthin inhibited cell death and ROS production in a concentration-dependent manner.

CONCLUSIONS

Collectively, these results indicate that astaxanthin inhibits ischemia-induced retinal cell death via its antioxidant effect. Hence, astaxanthin might be effective in treating retinal ischemic pathologies.

Protective Effects of Antiplacental Growth Factor Antibody Against Light-Induced Retinal Damage in Mice

PURPOSE

Placental growth factor (PlGF) is part of the VEGF family and is known to be involved in angiogenesis, vasopermeability, and neuroprotection. Recently, PlGF has been reported as a novel therapeutic target for wet AMD. However, there are few reports about the effect of PlGF against dry AMD. Previously, we reported that PlGF has protective effects against retinal neuronal cell damage in vitro. Therefore, we investigated the effects of PlGF against photoreceptor degeneration.

METHODS

In this study, mice were exposed to white light at 8000 lx for 3 hours to induce retinal damage, which was evaluated by recording the electroretinogram amplitude and measuring the outer nuclear layer (ONL) thickness. The mice were injected intravitreally with PlGF before light exposure, PlGF after light exposure, or anti-PlGF antibody before light exposure. RPE-choroid-sclera flat mounts were immunostained with anti-ZO-1 antibody to evaluate the disruption of retinal pigmented epithelium (RPE) cell-cell junctional integrity after light exposure. Furthermore, the expression of VEGF receptor in the retina and RPE-choroid complex after light exposure was measured using Western blot analysis.

RESULTS

Contrary to the expected outcome, PlGF treatment exacerbated the light-induced retinal functional damage and ONL thinning. In contrast, anti-PlGF treatment significantly improved the light-induced retinal degeneration. The disruption of RPE cell-cell junctional integrity after light exposure was suppressed by anti-PlGF treatment. Moreover, the VEGF receptor, which is involved in blood-retinal barrier breakdown, was up-regulated after light exposure.

CONCLUSIONS

These findings suggest that anti-PlGF antibody has protective effects against light-induced retinal degeneration in the murine retina through inhibition of RPE breakdown after light exposure. Thus, anti-PlGF antibody may be useful therapeutic agents in dry AMD.

Involvement of endoplasmic reticulum stress in optic nerve degeneration after chronic high intraocular pressure in DBA/2J mice

DBA/2J mice are one of several animal strains used for experimental models of both intraocular hypertension and glaucoma. This study investigates the relationship between endoplasmic reticulum (ER) stress and optic nerve degeneration in DBA/2J mice. Intraocular pressure (IOP) was measured in DBA/2J mice between the ages of 6 and 15 months. Optic nerve damage was assessed at 15 months of age. The nerve was immunostained with antibodies to either neurofilament heavy chain (NFH) or phosphorylated NFH (pNFH), and optic nerve damage was assessed by performing NFH- and pNFH-positive axon counts. Expression levels of the ER stress proteins 78-kDa glucose-regulated protein, also known as binding immunoglobulin protein, and C/EBP homologous protein were assayed with Western blotting. We also investigated ER stress localization in the optic nerve by double immunostaining with antibodies to ionized calcium-binding adaptor molecule 1, myelin basic protein, and glial fibrillary acidic protein (GFAP). In DBA/2J mice, IOP began to rise at 8 months of age, and retinal degeneration was detected at 15 months of age. DBA/2J mice had fewer axons than controls at 15 months of age. ER stress-related protein levels were higher in the optic nerves of DBA/2J mice and were colocalized with GFAP-positive astrocytes. Our findings suggest that ER stress plays a role in optic nerve degeneration during chronic ocular hypertension. Furthermore, ER stress may be related in some way to astrocyte activation.

Protective effect of SUN N8075, a free radical scavenger, against excessive light-induced retinal damage in mice

Although dry age-related macular degeneration (AMD) is one of the major causes of blindness, no effective therapies are developed. In this study, we investigated the effects of SUN N8075, a radical scavenger with neuroprotective properties, against light-induced retinal damage used as the model of dry AMD in mice. After dark adaption for 24 h, we exposed the mice at 8000 lx for 3 h. We evaluated the retinal damage by recording the electroretinagram (ERG) and measuring the thickness of outer nuclear layer (ONL) at 5 d after the light exposure. Retinal apoptotic cells were also detected by terminal deoxynucleotidyl transeferase mediated deoxyuridine triphosphate (dUTP) nick end labeling (TUNEL) staining, and the expression of 8-hydroxy-2-deoxyguanosine (8-OHdG) as an index for oxidative stress at 48 h after exposure to light. In ERG measurement, the intraperitoneal administration of SUN N8075 at 30 mg/kg improved the retinal dysfunction induced by the excess light exposure. In the histological evaluation, SUN N8075 inhibited the reduction of ONL thickness. In addition, SUN N8075 decreased in both numbers of TUNEL- and 8-OHdG-positive cells in ONL. These findings suggest that the systemic administration of SUN N8075 has protective effects on excess light-induced photoreceptor degeneration, via inhibition of oxidative stress.