The effect of ginkgo biloba on the rat retinal ganglion cell survival in the optic nerve crush model

Addressing neurodegeneration in glaucoma: Mechanisms, challenges, and treatments

Glaucoma is the leading cause of irreversible blindness globally. The disease causes vision loss due to neurodegeneration of the retinal ganglion cell (RGC) projection to the brain through the optic nerve. Glaucoma is associated with sensitivity to intraocular pressure (IOP). Thus, mainstay treatments seek to manage IOP, though many patients continue to lose vision. To address neurodegeneration directly, numerous preclinical studies seek to develop protective or reparative therapies that act independently of IOP. These include growth factors, compounds targeting metabolism, anti-inflammatory and antioxidant agents, and neuromodulators. Despite success in experimental models, many of these approaches fail to translate into clinical benefits. Several factors contribute to this challenge. Firstly, the anatomic structure of the optic nerve head differs between rodents, nonhuman primates, and humans. Additionally, animal models do not replicate the complex glaucoma pathophysiology in humans. Therefore, to enhance the success of translating these findings, we propose two approaches. First, thorough evaluation of experimental targets in multiple animal models, including nonhuman primates, should precede clinical trials. Second, we advocate for combination therapy, which involves using multiple agents simultaneously, especially in the early and potentially reversible stages of the disease. These strategies aim to increase the chances of successful neuroprotective treatment for glaucoma.

Optic Nerve Neuroprotection in Glaucoma: A Narrative Review

In recent years, researchers have been interested in neuroprotective therapies as a cutting-edge therapeutic strategy to treat neurodegenerative disorders by shielding the brain system from harmful events. Millions of individuals worldwide suffer from glaucoma, an ocular neurodegenerative disease characterized by gradual excavation of the optic nerve head, retinal axonal damage, and consequent visual loss. The pathology's molecular cause is still mostly unknown, and the current treatments are not able to alter the disease's natural progression. Thus, the modern approach to treating glaucoma consists of prescribing medications with neuroprotective properties, in line with the treatment strategy suggested for other neurodegenerative diseases. For this reason, several naturally derived compounds, including nicotinamide and citicoline, have been studied throughout time to try to improve glaucoma management by exploiting their neuroprotective properties. The purpose of this review is to examine the naturally derived compounds that are currently utilized in clinical practice for neuroprotection in glaucomatous patients based on scientific data, emphasizing these compounds' pivotal mechanism of action as well as their proven therapeutic and neuroprotective benefits.

Novel frontiers in neuroprotective therapies in glaucoma: Molecular and clinical aspects

In the last years, neuroprotective therapies have attracted the researcher interests as modern and challenging approach for the treatment of neurodegenerative diseases, aimed at protecting the nervous system from injuries. Glaucoma is a neurodegenerative disease characterized by progressive excavation of the optic nerve head, retinal axonal injury and corresponding vision loss that affects millions of people on a global scale. The molecular basis of the pathology is largely uncharacterized yet, and the therapeutic approaches available do not change the natural course of the disease. Therefore, in accordance with the therapeutic regimens proposed for other neurodegenerative diseases, a modern strategy to treat glaucoma includes prescription of drugs with neuroprotective activities. With respect to this, several preclinical and clinical investigations on a plethora of different drugs are currently ongoing. In this review, first, the conceptualization of the rationale for the adoption of neuroprotective strategies for retina is summarized. Second, the molecular aspects highlighting glaucoma as a neurodegenerative disease are reported. In conclusion, the molecular and pharmacological properties of most promising direct neuroprotective drugs used to delay glaucoma progression are examined, including: neurotrophic factors, NMDA receptor antagonists, the α2-adrenergic agonist, brimonidine, calcium channel blockers, antioxidant agents, nicotinamide and statins.

Treatment of Glaucoma with Natural Products and Their Mechanism of Action: An Update

Glaucoma is one of the leading causes of irreversible blindness. It is generally caused by increased intraocular pressure, which results in damage of the optic nerve and retinal ganglion cells, ultimately leading to visual field dysfunction. However, even with the use of intraocular pressure-lowering eye drops, the disease still progresses in some patients. In addition to mechanical and vascular dysfunctions of the eye, oxidative stress, neuroinflammation and excitotoxicity have also been implicated in the pathogenesis of glaucoma. Hence, the use of natural products with antioxidant and anti-inflammatory properties may represent an alternative approach for glaucoma treatment. The present review highlights recent preclinical and clinical studies on various natural products shown to possess neuroprotective properties for retinal ganglion cells, which thereby may be effective in the treatment of glaucoma. Intraocular pressure can be reduced by baicalein, forskolin, marijuana, ginsenoside, resveratrol and hesperidin. Alternatively, Ginkgo biloba, Lycium barbarum, Diospyros kaki, Tripterygium wilfordii, saffron, curcumin, caffeine, anthocyanin, coenzyme Q10 and vitamins B3 and D have shown neuroprotective effects on retinal ganglion cells via various mechanisms, especially antioxidant, anti-inflammatory and anti-apoptosis mechanisms. Extensive studies are still required in the future to ensure natural products' efficacy and safety to serve as an alternative therapy for glaucoma.

Diterpene Ginkgolides Meglumine Injection inhibits apoptosis induced by optic nerve crush injury via modulating MAPKs signaling pathways in retinal ganglion cells

ETHNOPHARMACOLOGICAL RELEVANCE

Diterpene Ginkgolides Meglumine Injection (DGMI) is made of extracts from Ginkgo biloba L, including Ginkgolides A, B, and K and some other contents, and has been widely used as the treatment of cerebral ischemic stroke in clinic. It can be learned from the "Compendium of Materia Medica" that Ginkgo possesses the effect of "dispersing toxin". The ancient Chinese phrase "dispersing toxin" is now explained as elimination of inflammation and oxidative state in human body. And it led to the original ideas for today's anti-oxidation studies of Ginkgo in apoptosis induced by optic nerve crush injury.

AIM OF THE STUDY

To investigate the underlying molecular mechanism of the DGMI in retinal ganglion cells (RGCs) apoptosis.

MATERIALS AND METHODS

TUNEL staining was used to observe the anti-apoptotic effects of DGMI on the adult rat optic nerve injury (ONC) model, and flow cytometry and hoechst 33,342 staining were used to observe the anti-apoptotic effects of DGMI on the oxygen glucose deprivation (OGD) induced RGC-5 cells injury model. The regulation of apoptosis and MAPKs pathways were investigated with Immunohistochemistry and Western blotting.

RESULTS

This study demonstrated that DGMI is able to decrease the conduction time of F-VEP and ameliorate histological features induced by optic nerve crush injury in rats. Immunohistochemistry and TUNEL staining results indicated that DGMI can also inhibit cell apoptosis via modulating MAPKs signaling pathways. In addition, treatment with DGMI markedly improved the morphological structures and decreased the apoptotic index in RGC-5 cells. Mechanistically, DGMI could significantly inhibit cell apoptosis by inhibiting p38, JNK and Erk1/2 activation.

CONCLUSION

The study shows that DGMI and ginkgolides inhibit RGCs apoptosis by impeding the activation of MAPKs signaling pathways in vivo and in vitro. Therefore, the present study provided scientific evidence for the underlying mechanism of DGMI and ginkgolides on optic nerve crush injury.

Ginkgo Biloba affects microvascular morphology: a prospective optical coherence tomography angiography pilot study

PURPOSE

To analyze the vascular morphology changes after consumption of Ginkgo biloba in healthy volunteers by optical coherence tomography angiography (OCTA).

METHODS

Sixty healthy volunteers without systemic and ocular disease were included in this prospective pilot study. After receiving the informed consent of the volunteers, Ginkgo biloba extract (120 mg oral capsule) was administered to sixty volunteers for 4 weeks, once a day in the morning. The main outcome measures were the difference between before and after four-week of consumption in best-corrected visual acuity (BCVA), retinal nerve fiber layer (RNFL) and subfoveal choroidal thickness (sfCT) with optical coherence tomography; whole, foveal, parafoveal and perifoveal regions' superior and deep macular vascular plexus vessel density, foveal avascular zone area (FAZ), FAZ perimeter (PERIM), vessel density in a 300 µm wide region around FAZ (FD-300), choroidal and outer retinal flow area, radial peripapillary capillary (RPC) vascular density of whole, inside the disc, peripapillary and four quadrants with OCTA.

RESULTS

The study group consisted of sixty eyes of 32 women and 28 men with a mean age of 20.57 ± 1.16 years. In post-consumption measurements, peripapillary and superior, inferior, temporal quadrant RPC vascular density (%) was statistically significantly higher than pre-consumption measurements (p 0.020, p 0.021, p 0.008 and p 0.014, respectively). No significant difference was observed for BCVA, sfCT, other macular or RPC vascular density and flow area OCTA parameters between measurements.

CONCLUSION

Four-week consumption of Ginkgo biloba leads to vascular morphological changes in RPC. Further clinical studies are needed to demonstrate its use and effects/benefits in glaucoma, optic neuropathy and other diseases affecting the optic nerve.

Natural Products: Evidence for Neuroprotection to Be Exploited in Glaucoma

Glaucoma, a leading cause of irreversible blindness worldwide, is an optic neuropathy characterized by the progressive death of retinal ganglion cells (RGCs). Elevated intraocular pressure (IOP) is recognized as the main risk factor. Despite effective IOP-lowering therapies, the disease progresses in a significant number of patients. Therefore, alternative IOP-independent strategies aiming at halting or delaying RGC degeneration is the current therapeutic challenge for glaucoma management. Here, we review the literature on the neuroprotective activities, and the underlying mechanisms, of natural compounds and dietary supplements in experimental and clinical glaucoma.

Effect of dietary modification and antioxidant supplementation on intraocular pressure and open-angle glaucoma

Primary open-angle glaucoma (POAG) is an age-dependent, intraocular pressure (IOP)-related degeneration of the retinal ganglion cells (RGC). At present, IOP is the only modifiable factor that has been identified to prevent glaucomatous vision loss. Though the pathogenesis of glaucomatous optic neuropathy is still not well understood, increasing evidence suggests oxidative stress may contribute to the induction and progression of glaucoma. Furthermore, antioxidant use may be protective against glaucoma through various mechanisms, including reducing IOP, preserving vascular health, and preventing ganglion cell loss. This article provides a comprehensive review of the effect of oxidative stress, diet, and antioxidant therapy on IOP and open-angle glaucoma.

[Antioxidant nutraceuticals for glaucoma]

Glaucoma is the leading cause of irreversible blindness in the world. Intraocular pressure (IOP) is currently the only proven modifiable risk factor for POAG. IOP-independent mechanisms contributing to the development of glaucomatous neurodegeneration include oxidative stress, excitotoxicity, mitochondrial dysfunction, and impaired ocular blood flow. In this regard, there has recently been growing interest in the use of various antioxidant dietary supplements as neuroprotective therapy for glaucoma. The issue of the effectiveness and safety of these biologically active additives is an urgent scientific problem reflected in numerous studies. This article reviews current concepts of oxidative/nitrosative stress, the role of reactive oxygen species (ROS)/reactive nitrogen (Nr) and their participation in the development of POAG, as well as experimental models and clinical studies using essential fatty acids, natural compounds and a number of other antioxidant substances that can counteract oxidative stress in glaucoma.

Ginkgo Biloba Extract in Ophthalmic and Systemic Disease, With a Focus on Normal-Tension Glaucoma

Glaucoma is a neurodegenerative eye disease that results in retinal ganglion cell loss and ultimately loss of vision. Elevated intraocular pressure (IOP) is the most common known risk factor for retinal ganglion cell damage and visual field loss, and the only modifiable risk factor proven to reduce the development and progression of glaucoma. This has greatly influenced our approach and assessment in terms of diagnosis and treatment. However, as many as ≥50% of patients with progressive vision loss from primary open angle glaucoma without IOP elevation (≤22 mm Hg) have been reported in the United States and Canada; 90% in Japan and 80% in Korea. Extensive research is currently underway to identify the etiology of risk factors for glaucoma other than or in addition to elevated IOP (so-called "normal-tension" glaucoma; NTG) and use this knowledge to expand available treatment options. Currently, Food and Drug Administration-approved medications for glaucoma exclusively target elevated IOP, suggesting the need for additional approaches to treatment options beyond the current scope as the definition of glaucoma changes to encompass cellular and molecular mechanisms. This review focuses on alternative medical approaches, specifically Ginkgo Biloba extract, as a potential treatment option for normal-tension glaucoma.

Neuroprotective Effect of Ginkgo Biloba Extract Against Hypoxic Retinal Ganglion Cell Degeneration In Vitro and In Vivo

Hypoxia-induced oxidative stress and disturbed microvascular circulation are both associated with pathogenesis of glaucoma. Ginkgo biloba extract (GBE) has been reported to have positive pharmacological effects on oxidative stress and impaired vascular circulation. This study aimed to investigate the neuroprotective effect of GBE against hypoxic injury to retinal ganglion cells (RGCs) both in vitro and in vivo. The rat RGC line was used, and oxidative stress was induced by hydrogen peroxide (H₂O₂) in vitro. EGb 761, a standardized GBE, or vehicle was applied to RGCs. Hypoxic optic nerve injury in vivo was induced by clamping the optic nerve of rats with a "microserrefine clip" with an applicator, which was applied without crushing the optic nerve. This method is different from "optic nerve crush model" and does not involve elevation of intraocular pressure, and may serve as a possible normal tension glaucoma animal model. EGb 761 at various concentrations or vehicle was administered intraperitoneally. RGC density was measured to estimate the survival both in vitro and in vivo. The survival of RGCs was significantly (P < .001) higher upon treatment with 1 or 5 μg/mL of EGb 761 compared with vehicle after oxidative stress in vitro. RGC density upon treatment with EGb 761 of 100 mg/kg (1465.6 ± 175 cells/mm²) or 250 mg/kg (1307.6 ± 213 cells/mm²) was significantly higher (P < .01, P < .05, respectively) than that obtained with vehicle (876.3 ± 136 cells/mm²) in vivo. Our results suggest that GBE has neuroprotective effect on RGCs against hypoxic injury both in vitro and in vivo.

Dietary Antioxidants, Macular Pigment, and Glaucomatous Neurodegeneration: A Review of the Evidence

Primary open-angle glaucoma (POAG) is a leading cause of irreversible blindness worldwide, and the prevalence is projected to increase to 112 million worldwide by 2040. Intraocular pressure is currently the only proven modifiable risk factor to treat POAG, but recent evidence suggests a link between antioxidant levels and risk for prevalent glaucoma. Studies have found that antioxidant levels are lower in the serum and aqueous humor of glaucoma patients. In this review, we provide a brief overview of the evidence linking oxidative stress to glaucomatous pathology, followed by an in-depth discussion of epidemiological studies and clinical trials of antioxidant consumption and glaucomatous visual field loss. Lastly, we highlight a possible role for antioxidant carotenoids lutein and zeaxanthin, which accumulate in the retina to form macular pigment, as evidence has emerged supporting an association between macular pigment levels and age-related eye disease, including glaucoma. We conclude that the evidence base is inconsistent in showing causal links between dietary antioxidants and glaucoma risk, and that prospective studies are needed to further investigate the possible relationship between macular pigment levels and glaucoma risk specifically.

Nutritional supplementation in the treatment of glaucoma: A systematic review

Current treatment strategies for glaucoma are limited to halting disease progression and do not restore lost visual function. Intraocular pressure is the main risk factor for glaucoma, and intraocular pressure-lowering treatment remains the mainstay of glaucoma treatment, but even successful intraocular pressure reduction does not stop the progression of glaucoma in all patients. We review the literature to determine whether nutritional interventions intended to prevent or delay the progression of glaucoma could prove to be a valuable addition to the mainstay of glaucoma therapy. A total of 33 intervention trials were included in this review, including 21 randomized controlled trials. These suggest that flavonoids exert a beneficial effect in glaucoma, particularly in terms of improving ocular blood flow and potentially slowing progression of visual field loss. In addition, supplements containing forskolin have consistently demonstrated the capacity to reduce intraocular pressure beyond the levels achieved with traditional therapy alone; however, despite the strong theoretical rationale and initial clinical evidence for the beneficial effect of dietary supplementation as an adjunct therapy for glaucoma, the evidence is not conclusive. More and better quality research is required to evaluate the role of nutritional supplementation in glaucoma.

Ginkgo biloba and its potential role in glaucoma

PURPOSE OF REVIEW

This study will review the research on the effect of ginkgo biloba extract (GBE) on patients with glaucoma.

RECENT FINDINGS

GBE appears to increase ocular blood flow in those with glaucoma. However, data on visual field outcomes are inconclusive.

SUMMARY

GBE has been shown to have antioxidant and vascular effects, making it potentially effective in treating glaucoma. Published data are limited but show an increase in ocular blood flow after GBE administration. Conclusive evidence is lacking regarding the effect of GBE on clinical outcomes in glaucoma patients such as visual field performance.

Rational Basis for Nutraceuticals in the Treatment of Glaucoma

BACKGROUND

Glaucoma, the second leading cause of blindness worldwide, is a chronic optic neuropathy characterized by progressive retinal ganglion cell (RGC) axons degeneration and death. Primary open-angle glaucoma (OAG), the most common type, is often associated with increased intraocular pressure (IOP), however other factors have been recognized to partecipate to the patogenesis of the optic neuropathy. IOP-independent mechanisms that contribute to the glaucoma-related neurodegeneration include oxidative stress, excitotoxicity, neuroinflammation, and impaired ocular blood flow. The involvement of several and diverse factors is one of the reasons for the progression of glaucoma observed even under efficient IOP control with the currently available drugs.

METHODS

Current research and online content related to the potential of nutritional supplements for limiting retinal damage and improving RGC survival is reviewed.

RESULTS

Recent studies have suggested a link between dietary factors and glaucoma risk. Particularly, some nutrients have proven capable of lowering IOP, increase circulation to the optic nerve, modulate excitotoxicity and promote RGC survival. However, the lack of clinical trials limit their current therapeutic use. The appropriate use of nutraceuticals that may be able to modify the risk of glaucoma may provide insight into glaucoma pathogenesis and decrease the need for, and therefore the side effects from, conventional therapies.

CONCLUSION

The effects of nutrients with anti-oxidant and neuroprotective properties are of great interest and nutraceuticals may offer some therapeutic potential although a further rigorous evaluation of nutraceuticals in the treatment of glaucoma is needed to determine their safety and efficacy.

Mangiferin Protects Retinal Ganglion Cells in Ischemic Mouse Retina via SIRT1

PURPOSE

To investigate whether mangiferin can increase the viability of retinal ganglion cells (RGCs) in ischemic mouse retina, and to determine the possible mechanism of neuroprotection.

METHODS

C57BL/6J mice underwent constant elevation of intraocular pressure for 60 min and received saline or mangiferin (30 mg/kg) intraperitoneally once daily until sacrifice. HIF-1α, GFAP and SIRT1 expression was assessed at 1, 4, and 7 days after retinal ischemia. Bax and Bcl-2 expression was also analyzed at 1 and 4 days. RGC survival was assessed by labeling flat-mounted retinas with Brn3a at 2 weeks after retinal ischemia. The effect of co-treatment with mangiferin and sirtinol (SIRT1 inhibitor) was also evaluated.

RESULTS

The expression of HIF-1α and GFAP was upregulated in saline-treated retinas within 7 days after ischemia. Mangiferin treatment suppressed this upregulation. The expression of SIRT1 was downregulated in saline-treated ischemic retinas. This downregulation was reversed by mangiferin treatment, resulting in a significant difference from saline-treated ischemic retinas. In mangiferin-treated ischemic retinas, Bax expression was downregulated, whereas Bcl-2 expression was upregulated in comparison with saline-treated ischemic retinas. Mangiferin treatment protected ischemic retinas against RGC loss. Treatment of sirtinol decreased the neuroprotective effect of mangiferin.

CONCLUSIONS

Our findings suggest that mangiferin has a neuroprotective effect on RGC through downregulation of HIF-1a and GFAP, and upregulation of SIRT1 in ischemic mouse retinas. We suggest that mangiferin might be a potential neuroprotective agent against RGC loss under oxidative stress.

Natural compounds and retinal ganglion cell neuroprotection

Glaucoma, the second leading cause of blindness in the world, is a chronic optic neuropathy often associated with increased intraocular pressure and characterized by progressive retinal ganglion cell (RGC) axons degeneration and death leading to typical optic nerve head damage and distinctive visual field defects. Although the pathogenesis of glaucoma is still largely unknown, it is hypothesized that RCGs become damaged through various insults/mechanisms, including ischemia, oxidative stress, excitotoxicity, defective axonal transport, trophic factor withdrawal, and neuroinflammation. In this review, we summarize the potential benefits of several natural compounds for RGCs neuroprotection.

Cellular responses following retinal injuries and therapeutic approaches for neurodegenerative diseases

Retinal neurodegenerative diseases like age-related macular degeneration, glaucoma, diabetic retinopathy and retinitis pigmentosa each have a different etiology and pathogenesis. However, at the cellular and molecular level, the response to retinal injury is similar in all of them, and results in morphological and functional impairment of retinal cells. This retinal degeneration may be triggered by gene defects, increased intraocular pressure, high levels of blood glucose, other types of stress or aging, but they all frequently induce a set of cell signals that lead to well-established and similar morphological and functional changes, including controlled cell death and retinal remodeling. Interestingly, an inflammatory response, oxidative stress and activation of apoptotic pathways are common features in all these diseases. Furthermore, it is important to note the relevant role of glial cells, including astrocytes, Müller cells and microglia, because their response to injury is decisive for maintaining the health of the retina or its degeneration. Several therapeutic approaches have been developed to preserve retinal function or restore eyesight in pathological conditions. In this context, neuroprotective compounds, gene therapy, cell transplantation or artificial devices should be applied at the appropriate stage of retinal degeneration to obtain successful results. This review provides an overview of the common and distinctive features of retinal neurodegenerative diseases, including the molecular, anatomical and functional changes caused by the cellular response to damage, in order to establish appropriate treatments for these pathologies.

Expression of insulin-like growth factor 1 receptor in rat retina following optic nerve injury

PURPOSE

To investigate the apoptosis in retinal ganglion cells (RGCs) and insulin-like growth factor 1 receptor (IGF-1R) in the retina following optic nerve crush.

METHODS

Healthy Wistar rats (N = 70) were divided into two groups: a normal control group and an optic nerve injury group. Immunohistochemistry and flow cytometry were performed to detect the expression of IGF-1R and to measure the apoptosis of RGCs, respectively.

RESULTS

Immunohistochemistry revealed that at 1 hr after optic nerve injury, IGF-1R immunoreactivity began to increase and reached a maximal level at 24 hr (p < 0.05), where it remained elevated up to 14 days after injury. RGC apoptosis in the normal control group was 0.53%, while the apoptosis rate in the optic nerve injury group increased over time. The apoptosis rate in the optic nerve injury group was 1.4% at 1 hr, 4.4% at 6 hr, 5.2% at 12 hr and reached a maximal level (8.5%) at 24 hr. Subsequently, the rate declined to 1.9% 7 days after injury and 0.9% 2 weeks after injury.

CONCLUSION

The IGF-1R immunereactivity in the retina increased after optic nerve injury. IGF-1R may regulate the apoptosis and regeneration of RGCs at different stages after optic nerve injury.

Botanical compounds: effects on major eye diseases

Botanical compounds have been widely used throughout history as cures for various diseases and ailments. Many of these compounds exhibit strong antioxidative, anti-inflammatory, and antiapoptotic properties. These are also common damaging mechanisms apparent in several ocular diseases, including age-related macular degeneration (AMD), glaucoma, diabetic retinopathy, cataract, and retinitis pigmentosa. In recent years, there have been many epidemiological and clinical studies that have demonstrated the beneficial effects of plant-derived compounds, such as curcumin, lutein and zeaxanthin, danshen, ginseng, and many more, on these ocular pathologies. Studies in cell cultures and animal models showed promising results for their uses in eye diseases. While there are many apparent significant correlations, further investigation is needed to uncover the mechanistic pathways of these botanical compounds in order to reach widespread pharmaceutical use and provide noninvasive alternatives for prevention and treatments of the major eye diseases.

Effect of Ginkgo biloba extract on endotoxin-induced labyrinthitis

OBJECTIVE

There are no reports on the therapeutic effect of Ginkgo biloba extract (GBE) on otitis media-induced labyrinthitis. The present study examined whether GBE can protect against cochlear damage induced by intratympanic instillation of lipopolysaccharide (LPS)-induced labyrinthitis.

MATERIALS AND METHODS

Experiments were performed in 20 healthy young male guinea pigs. The control group (n=10) received an intratympanic instillation of LPS (20 μl, 3mg/ml). The experimental group (n=10) received intratympanic instillation of LPS immediately after instillation of GBE (10mg/kg) and then experimental groups received GBE (100mg/kg) by intraperitoneal injection every day for 3 days. Instillation of LPS or LPS immediately after GBE was done in the right ear; the untreated left ear was considered normal. Physiological and morphological changes were evaluated.

RESULTS

Statistical analysis of treatment of GBE revealed significantly less hearing loss than LPS group (p<0.05). The ratio of the value of cochlear blood flow (CBF) compared to untreated left side was significantly higher in the GBE treated group than in the LPS-treated group (p<0.05). This result indicated the recovery of CBF in GBE treated group compared to LPS treated group. In the LPS group, scanning electron microscopy revealed hair cell damage with edema. Missing stereocilia in the third layer of the outer hair cell was revealed. However, both the inner hair cells and the outer hair cells had normal appearance in the GBE group. LPS group showed that cochlear Evans blue extravasation was increased strongly in the stria vascularis, spiral limbus, and in the spiral ligament compared with the GBE treated group.

CONCLUSION

GBE significantly minimizes cochlear damage against LPS-induced otitis media with labyrinthitis in a guinea pig model. GBE has potential as an adjunctive therapy to antibiotics in the treatment of acute otitis media with complicated labyrinthitis.

Neuroprotective effect of intravitreal cell-based glucagon-like peptide-1 production in the optic nerve crush model

PURPOSE

To examine the effect of intraocularly produced glucagon-like peptide-1 (GLP-1) on the survival rate of retinal ganglion cells in an optic nerve crush model.

METHODS

Forty-one Sprague--Dawley rats were divided into a study group (21 animals) in which 4 beads with 3000 genetically modified cells to produce GLP-1 were intravitreally implanted into the right eye; a saline control group (n = 12) with intravitreal saline injection; and a GLP-1 negative bead control group (n = 8) in which 4 beads with 3000 cells without GLP-1 production were intravitreally implanted. The right optic nerves of all animals were crushed in a standardized manner. After labeling the retinal ganglion cells by injecting 3% fluorogold into the superior colliculus, the animals were sacrificed, and the ganglion cells were counted on retinal flat mounts.

RESULTS

The retinal ganglion cell density of the right eyes was significantly higher in the study group (median: 2081 cells/mm(2) ; range: 1182-2953 cells/mm(2) ) than in the GLP-1 bead negative control group (median: 1328 cells/mm(2) ; range: 1007-2068 cells/mm(2) ; p = 0.002) and than in the saline control group (median: 1777 cells/mm(2) ; range: 1000-2405 cells/mm(2) ; p = 0.07). Correspondingly, the survival rate (ratio of retinal ganglion cell density of right eye/left eye) was significantly higher in the study group (median: 0.72; range: 0.40-1.04) than in the GLP-1 bead negative control group (median: 0.44; range: 0.36-0.68; p = 0.003) and than in the saline control group (median: 0.56; range: 0.36-0.89; p = 0.03).

CONCLUSION

Glucagon-like peptide-1 produced by intravitreally implanted cell beads was associated with a higher survival rate of retinal ganglion cells after an experimental optic nerve crush in rats.