Retinal ganglion cell apoptotic pathway in glaucoma: Initiating and downstream mechanisms

Visual Field Prognosis From Macula and Circumpapillary Spectral Domain Optical Coherence Tomography

Purpose

To explore the structural-functional loss relationship from optic-nerve-head- and macula-centred spectral-domain (SD) Optical Coherence Tomography (OCT) images in the full spectrum of glaucoma patients using deep-learning methods.

Methods

A cohort comprising 5238 unique eyes classified as suspects or diagnosed with glaucoma was considered. All patients underwent ophthalmologic examination consisting of standard automated perimetry (SAP), macular OCT, and peri-papillary OCT on the same day. Deep learning models were trained to estimate G-pattern visual field (VF) mean deviation (MD) and cluster MD using retinal thickness maps from seven layers: retinal nerve fiber layer (RNFL), ganglion cell layer and inner plexiform layer (GCL + IPL), inner nuclear layer and outer plexiform layer (INL + OPL), outer nuclear layer (ONL), photoreceptors and retinal pigmented epithelium (PR + RPE), choriocapillaris and choroidal stroma (CC + CS), total retinal thickness (RT).

Results

The best performance on MD prediction is achieved by RNFL, GCL + IPL and RT layers, with R2 scores of 0.37, 0.33, and 0.31, respectively. Combining macular and peri-papillary scans outperforms single modality prediction, achieving an R2 value of 0.48. Cluster MD predictions show promising results, notably in central clusters, reaching an R2 of 0.56.

Conclusions

The combination of multiple modalities, such as optic-nerve-head circular B-scans and retinal thickness maps from macular SD-OCT images, improves the performance of MD and cluster MD prediction. Our proposed model demonstrates the highest level of accuracy in predicting MD in the early-to-mid stages of glaucoma.

Translational Relevance

Objective measures recorded with SD-OCT can optimize the number of visual field tests and improve individualized glaucoma care by adjusting VF testing frequency based on deep-learning estimates of functional damage.

Remyelination-oriented clemastine treatment attenuates neuropathies of optic nerve and retina in glaucoma

As one of the top causes of blindness worldwide, glaucoma leads to diverse optic neuropathies such as degeneration of retinal ganglion cells (RGCs). It is widely accepted that the level of intraocular pressure (IOP) is a major risk factor in human glaucoma, and reduction of IOP level is the principally most well-known method to prevent cell death of RGCs. However, clinical studies show that lowering IOP fails to prevent RGC degeneration in the progression of glaucoma. Thus, a comprehensive understanding of glaucoma pathological process is required for developing new therapeutic strategies. In this study, we provide functional and histological evidence showing that optic nerve defects occurred before retina damage in an ocular hypertension glaucoma mouse model, in which oligodendroglial lineage cells were responsible for the subsequent neuropathology. By treatment with clemastine, an Food and Drug Administration (FDA)-approved first-generation antihistamine medicine, we demonstrate that the optic nerve and retina damages were attenuated via promoting oligodendrocyte precursor cell (OPC) differentiation and enhancing remyelination. Taken together, our results reveal the timeline of the optic neuropathies in glaucoma and highlight the potential role of oligodendroglial lineage cells playing in its treatment. Clemastine may be used in future clinical applications for demyelination-associated glaucoma.

Molecular pathways in experimental glaucoma models

Glaucoma is a complex and progressive disease that primarily affects the optic nerve axons, leading to irreversible vision loss. Although the exact molecular mechanisms underlying glaucoma pathogenesis are not fully understood, it is believed that except increased intraocular pressure, a combination of genetic and environmental factors play a role in the development of the disease. Animal models have been widely used in the study of glaucoma, allowing researchers to better understand the underlying mechanisms of the disease and test potential treatments. Several molecular pathways have been implicated in the pathogenesis of glaucoma, including oxidative stress, inflammation, and excitotoxic-induced neurodegeneration. This review summarizes the most important knowledge about molecular mechanisms involved in the glaucoma development. Although much research has been done to better understand the molecular mechanisms underlying this disease, there is still much to be learned to develop effective treatments and prevent vision loss in those affected by glaucoma.

The concept of gene therapy for glaucoma: the dream that has not come true yet

Gene therapies, despite of being a relatively new therapeutic approach, have a potential to become an important alternative to current treatment strategies in glaucoma. Since glaucoma is not considered a single gene disease, the identified goals of gene therapy would be rather to provide neuroprotection of retinal ganglion cells, especially, in intraocular-pressure-independent manner. The most commonly reported type of vector for gene delivery in glaucoma studies is adeno-associated virus serotype 2 that has a high tropism to retinal ganglion cells, resulting in long-term expression and low immunogenic profile. The gene therapy studies recruit inducible and genetic animal models of optic neuropathy, like DBA/2J mice model of high-tension glaucoma and the optic nerve crush-model. Reported gene therapy-based neuroprotection of retinal ganglion cells is targeting specific genes translating to growth factors (i.e., brain derived neurotrophic factor, and its receptor TrkB), regulation of apoptosis and neurodegeneration (i.e., Bcl-xl, Xiap, FAS system, nicotinamide mononucleotide adenylyl transferase 2, Digit3 and Sarm1), immunomodulation (i.e., Crry, C3 complement), modulation of neuroinflammation (i.e., erythropoietin), reduction of excitotoxicity (i.e., CamKIIα) and transcription regulation (i.e., Max, Nrf2). On the other hand, some of gene therapy studies focus on lowering intraocular pressure, by impacting genes involved in both, decreasing aqueous humor production (i.e., aquaporin 1), and increasing outflow facility (i.e., COX2, prostaglandin F2α receptor, RhoA/RhoA kinase signaling pathway, MMP1, Myocilin). The goal of this review is to summarize the current state-of-art and the direction of development of gene therapy strategies for glaucomatous neuropathy.

PRESERFLO MicroShunt implantation versus trabeculectomy for primary open-angle glaucoma: a two-year follow-up study

BACKGROUND

To compare the intermediate-term efficacy of PRESERFLO (PF) MicroShunt implantation with trabeculectomy (TE) in patients with primary open-angle glaucoma, focusing on longitudinal changes of functional and structural parameters.

METHODS

This retrospective comparative study included 104 eyes of 104 patients who underwent TE and 83 eyes of 83 patients that underwent PF implantation between January 2019 and December 2020, with a minimum follow-up of two years. Baseline and postoperative intraocular pressure (IOP), number of IOP-lowering medications, visual field mean defect (MD) and peripapillary retinal nerve fibre layer (RNFL) thickness measured using optical coherence tomography were assessed and compared between groups.

RESULTS

Baseline characteristics (age, sex, IOP, number of IOP-lowering medications, MD, RNFL thickness) were comparable between the two groups (all P > 0.05). During the two-year of follow-up, mean IOP decreased from 24.09 ± 1.15 mmHg and 21.67 ± 0.77 mmHg to 11.37 ± 1.13 mmHg (P < 0.001) and 15.50 ± 1.54 mmHg (P = 0.028), and the mean number of IOP-lowering medications decreased from 3.25 ± 0.14 and 3.51 ± 0.14 to 0.53 ± 0.14 (P < 0.001) and 1.06 ± 0.43 (P < 0.001) in the TE and PF groups, respectively. MD remained stable [- 11.54 ± 0.93 dB and - 11.17 ± 1.66 to - 10.67 ± 0.91 dB (P = 0.226) and - 10.40 ± 4.75 dB (P = 0.628) in the TE and PF groups, respectively] but RNFL thickness decreased continuously during follow-up [62.79 ± 1.94 µm and 62.62 ± 2.05 µm to 57.41 ± 1.81 µm (P < 0.001) and 60.22 ± 1.98 µm (P = 0.182) in the TE and PF groups, respectively].

CONCLUSION

PF implantation is comparably effective in the intermediate term in lowering IOP and reducing the use of IOP-lowering medications over a two-year follow-up period. Although visual field defects were stable, RNFL continued to decrease during postoperative follow-up.

Signalling pathways and cell death mechanisms in glaucoma: Insights into the molecular pathophysiology

Glaucoma is a complex multifactorial eye disease manifesting in retinal ganglion cell (RGC) death and optic nerve degeneration, ultimately causing irreversible vision loss. Research in recent years has significantly enhanced our understanding of RGC degenerative mechanisms in glaucoma. It is evident that high intraocular pressure (IOP) is not the only contributing factor to glaucoma pathogenesis. The equilibrium of pro-survival and pro-death signalling pathways in the retina strongly influences the function and survival of RGCs and optic nerve axons in glaucoma. Molecular evidence from human retinal tissue analysis and a range of experimental models of glaucoma have significantly contributed to unravelling these mechanisms. Accumulating evidence reveals a wide range of molecular signalling pathways that can operate -either alone or via intricate networks - to induce neurodegeneration. The roles of several molecules, including neurotrophins, interplay of intracellular kinases and phosphates, caveolae and adapter proteins, serine proteases and their inhibitors, nuclear receptors, amyloid beta and tau, and how their dysfunction affects retinal neurons are discussed in this review. We further underscore how anatomical alterations in various animal models exhibiting RGC degeneration and susceptibility to glaucoma-related neuronal damage have helped to characterise molecular mechanisms in glaucoma. In addition, we also present different regulated cell death pathways that play a critical role in RGC degeneration in glaucoma.

Suppressing DNMT3a Alleviates the Intrinsic Epigenetic Barrier for Optic Nerve Regeneration and Restores Vision in Adult Mice

The limited regenerative potential of the optic nerve in adult mammals presents a major challenge for restoring vision after optic nerve trauma or disease. The mechanisms of this regenerative failure are not fully understood1,2. Here, through small-molecule and genetic screening for epigenetic modulators3, we identify DNA methyltransferase 3a (DNMT3a) as a potent inhibitor of axon regeneration in mouse and human retinal explants. Selective suppression of DNMT3a in retinal ganglion cells (RGCs) by gene targeting or delivery of shRNA leads to robust, full-length regeneration of RGC axons through the optic nerve and restoration of vision in adult mice after nerve crush injury. Genome-wide bisulfite and transcriptome profiling in combination with single nucleus RNA-sequencing of RGCs revealed selective DNA demethylation and reactivation of genetic programs supporting neuronal survival and axonal growth/regeneration by DNMT3a deficiency. This was accompanied by the suppression of gene networks associated with apoptosis and inflammation. Our results identify DNMT3a as the central orchestrator of an RGC-intrinsic mechanism that limits optic nerve regeneration. Suppressing DNMT3a expression in RGCs unlocks the epigenetic switch for optic nerve regeneration and presents a promising therapeutic avenue for effectively reversing vision loss resulted from optic nerve trauma or diseases.

Keratin8 Deficiency Aggravates Retinal Ganglion Cell Damage Under Acute Ocular Hypertension

Purpose

Keratin 8/18 (KRT8/18), paired members of the intermediate filament family, have shown vital functions in regulating physiological activities more than supporting the mechanic strength for cells and organelles. However, the KRT8/18 presence in retinal ganglion cells (RGCs) and functions on neuroprotection in a mouse model of acute ocular hypertension (AOH) are unknown and worthy of exploration.

Methods

We identified the existence of KRT8/18 in normal human and mouse retinas and primary RGCs. KRT8/18 levels were detected after AOH modeling. The adeno-associated virus (AAV) system was intravitreally used for selective KRT8 knockdown in RGCs. The histological changes, the loss and dysfunction of RGCs, and the gliosis in retinas were detected. The markers of cell apoptosis and MAPK pathways were investigated.

Results

KRT8/18 existed in all retinal layers and was highly expressed in RGCs, and they increased after AOH induction. The KRT8 knockdown in RGCs caused no histopathological changes and RGC loss in retinas without AOH modeling. However, after the KRT8 deficiency, AOH significantly promoted the loss of whole retina and inner retina thickness, the reduction, apoptosis, and dysfunction of RGCs, and the glial activation. Besides, downregulated Bcl-2 and upregulated cleaved-Caspase 3 were found in the AOH retinas with KRT8 knockdown, which may be caused by the increased phosphorylation level of MAPK pathways (JNK, p38, and ERK).

Conclusions

The KRT8 deficiency promoted RGC apoptosis and neurodegeneration by abnormal activation of MAPK pathways in AOH retinas. Targeting KRT8 may serve as a novel treatment for saving RCGs from glaucomatous injuries.

Cell-Based Therapies for Glaucoma

Glaucomatous optic neuropathy (GON) is the major cause of irreversible visual loss worldwide and can result from a range of disease etiologies. The defining features of GON are retinal ganglion cell (RGC) degeneration and characteristic cupping of the optic nerve head (ONH) due to tissue remodeling, while intraocular pressure remains the only modifiable GON risk factor currently targeted by approved clinical treatment strategies. Efforts to understand the mechanisms that allow species such as the zebrafish to regenerate their retinal cells have greatly increased our understanding of regenerative signaling pathways. However, proper integration within the retina and projection to the brain by the newly regenerated neuronal cells remain major hurdles. Meanwhile, a range of methods for in vitro differentiation have been developed to derive retinal cells from a variety of cell sources, including embryonic and induced pluripotent stem cells. More recently, there has been growing interest in the implantation of glial cells as well as cell-derived products, including neurotrophins, microRNA, and extracellular vesicles, to provide functional support to vulnerable structures such as RGC axons and the ONH. These approaches offer the advantage of not relying upon the replacement of degenerated cells and potentially targeting earlier stages of disease pathogenesis. In order to translate these techniques into clinical practice, appropriate cell sourcing, robust differentiation protocols, and accurate implantation methods are crucial to the success of cell-based therapy in glaucoma. Translational Relevance: Cell-based therapies for glaucoma currently under active development include the induction of endogenous regeneration, implantation of exogenously derived retinal cells, and utilization of cell-derived products to provide functional support.

Influence of Cilioretinal Arteries on Flow Density in Glaucoma Patients Measured Using Optical Coherence Tomography Angiography

It has long been speculated whether the presence of a cilioretinal artery (CRA) can influence the development of glaucomatous damage in patients with open-angle glaucoma. Studies involving healthy patients have shown a change in flow density (FD) depending on the presence of a CRA. Similarly, studies that compared the optical coherence tomography angiography (OCTA) results of healthy controls and glaucoma cohorts identified a reduction in FD in certain retinal layers for glaucoma patients. These observations raise the question of whether FD is altered in glaucoma patients depending on the presence of CRA, with possible implications for the progression of glaucomatous damage. In this prospective study, 201 eyes of 134 primary and secondary open-angle glaucoma patients who visited the Department of Ophthalmology at the University of Muenster Medical Center, Germany were included. The patients were allocated to different groups according to the presence of CRAs and the level of glaucoma severity. The FD results obtained using OCTA for the CRA and non-CRA groups were compared. While FD differed noticeably between the CRA and non-CRA cohorts in the deep macular plexus, no differences in FD were observed between the two groups when adjusted for glaucoma severity. In both the CRA and non-CRA eyes, increasing glaucoma severity correlated most strongly with a reduction in peripapillary FD. Our results suggest that the presence of CRAs does not significantly affect retinal perfusion in glaucoma patients.

Activation of retinal glial cells contributes to the degeneration of ganglion cells in experimental glaucoma

Elevation of intraocular pressure (IOP) is a major risk factor for neurodegeneration in glaucoma. Glial cells, which play an important role in normal functioning of retinal neurons, are well involved into retinal ganglion cell (RGC) degeneration in experimental glaucoma animal models generated by elevated IOP. In response to elevated IOP, mGluR I is first activated and Kir4.1 channels are subsequently inhibited, which leads to the activation of Müller cells. Müller cell activation is followed by a complex process, including proliferation, release of inflammatory and growth factors (gliosis). Gliosis is further regulated by several factors. Activated Müller cells contribute to RGC degeneration through generating glutamate receptor-mediated excitotoxicity, releasing cytotoxic factors and inducing microglia activation. Elevated IOP activates microglia, and following morphological and functional changes, these cells, as resident immune cells in the retina, show adaptive immune responses, including an enhanced release of pro-inflammatory factors (tumor neurosis factor-α, interleukins, etc.). These ATP and Toll-like receptor-mediated responses are further regulated by heat shock proteins, CD200R, chemokine receptors, and metabotropic purinergic receptors, may aggravate RGC loss. In the optic nerve head, astrogliosis is initiated and regulated by a complex reaction process, including purines, transmitters, chemokines, growth factors and cytokines, which contributes to RGC axon injury through releasing pro-inflammatory factors and changing extracellular matrix in glaucoma. The effects of activated glial cells on RGCs are further modified by the interplay among different types of glial cells. This review is concluded by presenting an in-depth discussion of possible research directions in this field in the future.

RAGE and its ligand amyloid beta promote retinal ganglion cell loss following ischemia-reperfusion injury

Introduction

Glaucoma is a progressive neurodegenerative disease associated with age. Accumulation of amyloid-beta (Aß) proteins in the ganglion cell layer (GCL) and subsequent retinal ganglion cell (RGC) loss is an established pathological hallmark of the disease. The mechanism through which Aß provokes RGC loss remains unclear. The receptor for the advanced glycation end product (RAGE), and its ligand Aß, have been shown to mediate neuronal loss via internalizing Aß within the neurons. In this study, we investigated whether the RAGE-Aß axis plays a role in RGC loss in experimental glaucoma.

Methods

Retinal ischemia was induced by an acute elevation of intraocular pressure in RAGE^-/- and wild-type (WT) control mice. In a subset of animals, oligomeric Aß was injected directly into the vitreous of both strains. RGC loss was assessed using histology and biochemical assays. Baseline and terminal positive scotopic threshold (pSTR) were also recorded.

Results

Retinal ischemia resulted in 1.9-fold higher RGC loss in WT mice compared to RAGE^-/- mice (36 ± 3% p < 0.0001 vs. 19 ± 2%, p = 0.004). Intravitreal injection of oligomeric Aß resulted in 2.3-fold greater RGC loss in WT mice compared to RAGE^-/- mice, 7-days post-injection (55 ± 4% p = 0.008 vs. 24 ± 2%, p = 0.02). We also found a significant decline in the positive scotopic threshold response (pSTR) amplitude of WT mice compared to RAGE^-/- (36 ± 3% vs. 16 ± 6%).

Discussion

RAGE^-/- mice are protected against RGC loss following retinal ischemia. Intravitreal injection of oligomeric Aß accelerated RGC loss in WT mice but not RAGE^-/-. A co-localization of RAGE and Aß, suggests that RAGE-Aß binding may contribute to RGC loss.

S1PR1 signaling attenuates apoptosis of retinal ganglion cells via modulation of cJun/Bim cascade and Bad phosphorylation in a mouse model of glaucoma

Glaucoma is a complex neurodegenerative disease characterized by optic nerve damage and apoptotic retinal ganglion cell (RGC) death, and is the leading cause of irreversible blindness worldwide. Among the sphingosine 1-phosphate receptors (S1PRs) family, S1PR1 is a highly expressed subtype in the central nervous system and has gained rapid attention as an important mediator of pathophysiological processes in the brain and the retina. Our recent study showed that mice treated orally with siponimod drug exerted neuroprotection via modulation of neuronal S1PR1 in experimental glaucoma. This study identified the molecular signaling pathway modulated by S1PR1 activation with siponimod treatment in RGCs in glaucomatous injury. We investigated the critical neuroprotective signaling pathway in vivo using mice deleted for S1PR1 in RGCs. Our results showed marked upregulation of the apoptotic pathway was associated with decreased Akt and Erk1/2 activation levels in the retina in glaucoma conditions. Activation of S1PR1 with siponimod treatment significantly increased neuroprotective Akt and Erk1/2 activation and attenuated the apoptotic signaling via suppression of c-Jun/Bim cascade and by increasing Bad phosphorylation. Conversely, deletion of S1PR1 in RGCs significantly increased the apoptotic cells in the ganglion cell layer in glaucoma and diminished the neuroprotective effects of siponimod treatment on Akt/Erk1/2 activation, c-Jun/Bim cascade, and Bad phosphorylation. Our data demonstrated that activation of S1PR1 in RGCs induces crucial neuroprotective signaling that suppresses the proapoptotic c-Jun/Bim cascade and increases antiapoptotic Bad phosphorylation. Our findings suggest that S1PR1 is a potential therapeutic target for neuroprotection of RGCs in glaucoma.

An Altered Neurovascular System in Aging-Related Eye Diseases

The eye has a complex and metabolically active neurovascular system. Repeated light injuries induce aging and trigger age-dependent eye diseases. Damage to blood vessels is related to the disruption of the blood-retinal barrier (BRB), altered cellular communication, disrupted mitochondrial functions, and exacerbated aggregated protein accumulation. Vascular complications, such as insufficient blood supply and BRB disruption, have been suggested to play a role in glaucoma, age-related macular degeneration (AMD), and Alzheimer's disease (AD), resulting in neuronal cell death. Neuronal loss can induce vision loss. In this review, we discuss the importance of the neurovascular system in the eye, especially in aging-related diseases such as glaucoma, AMD, and AD. Beneficial molecular pathways to prevent or slow down retinal pathologic processes will also be discussed.

Using Computational Drug-Gene Analysis to Identify Novel Therapeutic Candidates for Retinal Neuroprotection

Retinal cell death is responsible for irreversible vision loss in many retinal disorders. No commercially approved treatments are currently available to attenuate retinal cell loss and preserve vision. We seek to identify chemicals/drugs with thoroughly-studied biological functions that possess neuroprotective effects in the retina using a computational bioinformatics approach. We queried the National Center for Biotechnology Information (NCBI) to identify genes associated with retinal neuroprotection. Enrichment analysis was performed using ToppGene to identify compounds related to the identified genes. This analysis constructs a Pharmacome from multiple drug-gene interaction databases to predict compounds with statistically significant associations to genes involved in retinal neuroprotection. Compounds with known deleterious effects (e.g., asbestos, ethanol) or with no clinical indications (e.g., paraquat, ozone) were manually filtered. We identified numerous drug/chemical classes associated to multiple genes implicated in retinal neuroprotection using a systematic computational approach. Anti-diabetics, lipid-lowering medicines, and antioxidants are among the treatments anticipated by this analysis, and many of these drugs could be readily repurposed for retinal neuroprotection. Our technique serves as an unbiased tool that can be utilized in the future to lead focused preclinical and clinical investigations for complex processes such as neuroprotection, as well as a wide range of other ocular pathologies.

miR-181d-5p Protects against Retinal Ganglion Cell Death after Blunt Ocular Injury by Regulating NFIA-Medicated Astrocyte Development

Background

Traumatic optic neuropathy (TON) refers to damage to the optic nerve resulting from direct and indirect trauma to the head and face. One of the important pathological processes in TON is the death of retinal ganglion cells (RGCs), but the cause of RGCs death remains unclear. We aimed to explore the mechanisms of RGCs death in an experimental TON model.

Methods

Optic nerve crush injury was induced in ten New Zealand white rabbits. On the 1st, 3rd, 7th, 14th, and 28th days after the operation, the retinal tissues of the rabbits were observed pathologically by hematoxylin-eosin staining. The expression of POU-homeodomain transcription factor Brn3a and glial fibrillary acidic protein (GFAP) was measured by immunofluorescence to evaluate the number of RGCs and astrocytes, respectively. miRNA expression and protein levels were assessed by RT-qPCR and western blot methods, respectively. Finally, the malondialdehyde content, superoxide dismutase activity, and proinflammatory factor levels were measured by ELISA. Western blot and dual-luciferase reporter assays were used to elucidate the relationship between miR-181d-5p and nuclear factor I-A (NFIA).

Results

Blunt ocular trauma increased oxidative stress and apoptosis and reduced ganglion cell layer (GCL) density. The expression of miR-181d-5p was decreased in retinal tissues, and its overexpression relieved RGCs death, astrocyte development, oxidative stress, and inflammation of the retina, which were reversed by NFIA overexpression.

Conclusion

miR-181d-5p can protect against the deterioration of TON by inhibiting RGCs death, astrocyte development, oxidative stress, and inflammation by targeting NFIA. This study provides new insight into early medical intervention in patients with TON.

Two Year Functional and Structural Changes-A Comparison between Trabeculectomy and XEN Microstent Implantation Using Spectral Domain Optical Coherence Tomography

The aim of this study was to analyze retinal nerve fiber layer (RNFL) thickness after trabeculectomy (TE) versus XEN microstent implantation (XEN) in primary open-angle glaucoma (POAG) cases naïve to prior incisional glaucoma surgery. We examined 119 consecutive glaucoma patients retrospectively, who received a TE or XEN for medically uncontrolled POAG. Intraocular pressure (IOP), amount of IOP-lowering medication, mean deviation of standard automated perimetry and peripapillary RNFL thickness were evaluated during the first 24 months after surgery. Fifty eyes were treated with TE and 69 eyes with XEN. Mean IOP decreased from 25.1 ± 0.8 to 13.3 ± 0.6 mm Hg (p < 0.01) and mean number of IOP-lowering eye drops from 3.2 ± 0.2 to 0.4 ± 0.1 (p < 0.01) 24 months after TE. In 69 eyes undergoing XEN, mean IOP dropped from 24.8 ± 0.6 to 15.0 ± 0.4 mm Hg (p < 0.01) and medication from 3.0 ± 0.1 to 0.6 ± 0.1 (p < 0.01) during the 24 months follow-up. Mean deviation of standard automated perimetry remained stable in TE (8.5 ± 0.7 to 8.1 ± 0.8 dB; p = 0.54) and XEN group (11,0 ± 0.5 to 11.5 ± 0.5 dB; p = 0.12) after 24 months, while mean RNFL thickness further deteriorated in the TE (−2.28 ± 0.65 µm/year) and XEN (−0.68 ± 0.34 µm/year) group. Postoperative RNFL loss develops after TE and XEN despite effective and significant lowering of IOP and amount of IOP-lowering medication. RNFL loss was more pronounced in the first year after glaucoma surgery.

Surgical Menopause Impairs Retinal Conductivity and Worsens Prognosis in an Acute Model of Rat Optic Neuropathy

Deficiency of estradiol during the menopausal period is an important risk factor for neurodegenerative diseases, including various optic neuropathies. The aim of this study was to evaluate the impact of surgical menopause on the function and survival ratio of RGCs in the rat model of ONC (optic nerve crush). We used eight-week-old female Long Evans rats, divided into two main groups depending on the time between ovariectomy procedure (OVA) and euthanasia (two weeks vs. seven weeks), and subgroups—OVA, OVA + ONC, or ONC. Retinal function was assessed with electroretinography (ERG). RGC loss ratio was evaluated using immunolabelling and counting of RGCs. Seven weeks after OVA, the menopause morphologically affected interneurons but not RGC; however, when the ONC procedure was applied, RGCs appeared to be more susceptible to damage in case of deprivation of estrogens. In our analysis, PhNR (photopic negative responses) were severely diminished in the OVA + ONC group. A deprivation of estrogens in menopause results in accelerated retinal neurodegeneration that firstly involves retinal interneurons. The lack of estrogens increases the susceptibility of RGCs to insults.

Recent developments of neuroprotective agents for degenerative retinal disorders

Retinal degeneration is a debilitating ocular complication characterized by the progressive loss of photoreceptors and other retinal neurons, which are caused by a group of retinal diseases affecting various age groups, and increasingly prevalent in the elderly. Age-related macular degeneration, diabetic retinopathy and glaucoma are among the most common complex degenerative retinal disorders, posing significant public health problems worldwide largely due to the aging society and the lack of effective therapeutics. Whilst pathoetiologies vary, if left untreated, loss of retinal neurons can result in an acquired degeneration and ultimately severe visual impairment. Irrespective of underlined etiology, loss of neurons and supporting cells including retinal pigment epithelium, microvascular endothelium, and glia, converges as the common endpoint of retinal degeneration and therefore discovery or repurposing of therapies to protect retinal neurons directly or indirectly are under intensive investigation. This review overviews recent developments of potential neuroprotectants including neuropeptides, exosomes, mitochondrial-derived peptides, complement inhibitors, senolytics, autophagy enhancers and antioxidants either still experimentally or in clinical trials. Effective treatments that possess direct or indirect neuroprotective properties would significantly lift the burden of visual handicap.

Retinal ganglion cell loss in an ex vivo mouse model of optic nerve cut is prevented by curcumin treatment

Retinal ganglion cell (RGC) loss is a pathologic feature common to several retinopathies associated to optic nerve damage, leading to visual loss and blindness. Although several scientific efforts have been spent to understand the molecular and cellular changes occurring in retinal degeneration, an effective therapy to counteract the retinal damage is still not available. Here we show that eyeballs, enucleated with the concomitant optic nerve cut (ONC), when kept in PBS for 24 h showed retinal and optic nerve degeneration. Examining retinas and optic nerves at different time points in a temporal window of 24 h, we found a thinning of some retinal layers especially RGC's layer, observing a powerful RGC loss after 24 h correlated with an apoptotic, MAPKs and degradative pathways dysfunctions. Specifically, we detected a time-dependent increase of Caspase-3, -9 and pro-apoptotic marker levels, associated with a strong reduction of BRN3A and NeuN levels. Importantly, a powerful activation of JNK, c-Jun, and ERK signaling (MAPKs) were observed, correlated with a significant augmented SUMO-1 and UBC9 protein levels. The degradation signaling pathways was also altered, causing a significant decrease of ubiquitination level and an increased LC3B activation. Notably, it was also detected an augmented Tau protein level. Curcumin, a powerful antioxidant natural compound, prevented the alterations of apoptotic cascade, MAPKs, and SUMO-1 pathways and the degradation system, preserving the RGC survival and the retinal layer thickness. This ex vivo retinal degeneration model could be a useful method to study, in a short time window, the effect of neuroprotective tools like curcumin that could represent a potential treatment to contrast retinal cell death.

Role of Oxidative Stress in Ocular Diseases Associated with Retinal Ganglion Cells Degeneration

Ocular diseases associated with retinal ganglion cell (RGC) degeneration is the most common neurodegenerative disorder that causes irreversible blindness worldwide. It is characterized by visual field defects and progressive optic nerve atrophy. The underlying pathophysiology and mechanisms of RGC degeneration in several ocular diseases remain largely unknown. RGCs are a population of central nervous system neurons, with their soma located in the retina and long axons that extend through the optic nerve to form distal terminals and connections in the brain. Because of this unique cytoarchitecture and highly compartmentalized energy demand, RGCs are highly mitochondrial-dependent for adenosine triphosphate (ATP) production. Recently, oxidative stress and mitochondrial dysfunction have been found to be the principal mechanisms in RGC degeneration as well as in other neurodegenerative disorders. Here, we review the role of oxidative stress in several ocular diseases associated with RGC degenerations, including glaucoma, hereditary optic atrophy, inflammatory optic neuritis, ischemic optic neuropathy, traumatic optic neuropathy, and drug toxicity. We also review experimental approaches using cell and animal models for research on the underlying mechanisms of RGC degeneration. Lastly, we discuss the application of antioxidants as a potential future therapy for the ocular diseases associated with RGC degenerations.

Hydrogen Sulfide Reduces Ischemia and Reperfusion Injury in Neuronal Cells in a Dose- and Time-Dependent Manner

Background: The ischemia-reperfusion injury (IRI) of neuronal tissue, such as the brain and retina, leads to possible cell death and loss of function. Current treatment options are limited, but preliminary observations suggest a protective effect of hydrogen sulfide (H₂S). However, the dosage, timing, and mechanism of inhaled H₂S treatment after IRI requires further exploration. Methods: We investigated possible neuroprotective effects of inhaled H₂S by inducing retinal ischemia–reperfusion injury in rats for the duration of 1 h (120 mmHg), followed by the administration of hydrogen sulfide (H₂S) for 1 h at different time points (0, 1.5, and 3 h after the initiation of reperfusion) and at different H₂S concentrations (120, 80, and 40 ppm). We quantified the H₂S effect by conducting retinal ganglion cell counts in fluorogold-labeled animals 7 days after IRI. The retinal tissue was harvested after 24 h for molecular analysis, including qPCR and Western blotting. Apoptotic and inflammatory mediators, transcription factors, and markers for oxidative stress were investigated. Histological analyses of the retina and the detection of inflammatory cytokines in serum assays were also performed. Results: The effects of inhaled H₂S were most evident at a concentration of 80 ppm administered 1.5 h after IRI. H₂S treatment increased the expression of anti-apoptotic Bcl-2, decreased pro-apoptotic Bax expression, reduced the release of the inflammatory cytokines IL-1β and TNF-α, attenuated NF-κB p65, and enhanced Akt phosphorylation. H₂S also downregulated NOX4 and cystathionine β-synthase. Histological analyses illustrated a reduction in TNF-α in retinal ganglion cells and lower serum levels of TNF-α in H₂S-treated animals after IRI. Conclusion: After neuronal IRI, H₂S mediates neuroprotection in a time- and dose-dependent manner. The H₂S treatment modulated transcription factor NF-κB activation and reduced retinal inflammation.

Functional Monitoring after Trabeculectomy or XEN Microstent Implantation Using Spectral Domain Optical Coherence Tomography and Visual Field Indices-A Retrospective Comparative Cohort Study

Simple Summary

Primary open-angle glaucoma leads to a loss of retinal ganglion cells and a reduction in the retinal nerve fiber layer thickness, consequently leading to the development and growth of visual field defects. In its final stages, this results in visual loss and irreversible blindness if not treated adequately. A reduction in the intraocular pressure by means of medication and/or surgery is the only known treatment option for slowing, or at best, arresting disease progression. This study demonstrates that trabeculectomy and XEN microstent implantation are nearly equally effective techniques for reducing intraocular pressure and stabilizing visual acuity and pre-developed visual field defects over a follow-up period of 24 months after surgery. However, further analysis using spectral domain optical coherence tomography revealed that disease progression occurs in terms of further retinal nerve fiber layer loss after both trabeculectomy and XEN microstent implantation.

Abstract

The aim of this study was to compare the efficacy of trabeculectomy (TE), single XEN microstent implantation (solo XEN) or combined XEN implantation and cataract surgery (combined XEN) in primary open-angle glaucoma cases, naïve to prior surgical treatment, using a monocentric retrospective comparative cohort study. Intraocular pressure (IOP) and the number of IOP-lowering drugs (Meds) were monitored during the first 24 months after surgery. Further disease progression was monitored using peripapillary retinal nerve fiber layer (RNFL) thickness examinations using spectral domain optical coherence tomography (OCT) as well as visual acuity (VA) and visual field (VF) tests. In the TE group (52 eyes), the mean IOP decreased from 24.9 ± 5.9 to 13.9 ± 4.2 mmHg (p < 0.001) and Meds decreased from 3.2 ± 1.2 to 0.5 ± 1.1 (p < 0.001). In the solo XEN (38 eyes) and the combined XEN groups, the mean IOP decreased from 24.1 ± 4.7 to 15.7 ± 3.0 mmHg (p < 0.001) and 25.4 ± 5.6 to 14.7 ± 3.2 mmHg (p < 0.001), while Meds decreased from 3.3 ± 0.8 to 0.8 ± 1.2 (p < 0.001) and 2.7 ± 1.2 to 0.4 ± 1.0 (p < 0.001), respectively. The VF and VA indices showed no sign of further deterioration, the RNFL thickness further decreased in all treatment groups after surgery. TE and XEN led to comparable reductions in IOP and Meds. Although the VA and VF indices remained unaltered, the RNFL thickness continuously decreased in all treatment groups during the 24-month follow-up.

Role of mammalian target of rapamycin in regulating HIF-1α and vascular endothelial growth factor signals in glaucoma

Hypoxia inducible factor subtype 1α (HIF-1α) in retinal tissues is involved in the development of glaucoma. This study examined the role played by mammalian target of rapamycin (mTOR) in regulating expression of HIF-1α and its downstream pathway, vascular endothelial growth factor (VEGF). Glaucoma was induced by chronic elevation of intraocular pressure using laser burns in rats. ELISA and western blot analysis were employed to determine the levels of HIF-1α, VEGF and mTOR in retinal tissues of eyes with high intraocular pressure. In results, HIF-1α, VEGF and VEGF receptor subtype 2 were increased in laser eyes. The p-mTOR, mTOR-mediated phosphorylation of 4E-binding protein 4, p70 ribosomal S6 protein kinase 1 were also amplified in retina of laser eyes. Blocking mTOR using rapamycin attenuated HIF-1α-VEGF pathways, accompanied with downregulation of apoptotic Caspase-3. Our data revealed potential signalling pathways engaged in the development of glaucoma, including the activation of mTOR and HIF-1α-VEGF mechanism.

Adenosine receptors as promising targets for the management of ocular diseases

The ocular drug discovery arena has undergone a significant improvement in the last few years culminating in the FDA approvals of 8 new drugs. However, despite a large number of drugs, generics, and combination products available, it remains an urgent need to find breakthrough strategies and therapies for tackling ocular diseases. Targeting the adenosinergic system may represent an innovative strategy for discovering new ocular therapeutics. This review focused on the recent advance in the field and described the numerous nucleoside and non-nucleoside modulators of the four adenosine receptors (ARs) used as potential tools or clinical drug candidates.

Outcome of a single XEN microstent implant for glaucoma patients with different types of glaucoma

BACKGROUND

The aim of this retrospective study was to compare the efficacy and safety profile of a single XEN-microstent in different types of primary and secondary open angle glaucoma.

METHODS

A single XEN microstent was implanted in patients with primary open-angle glaucoma (POAG), normal-tension glaucoma (NTG), pseudoexfoliation glaucoma (PEX) and secondary glaucoma (Sec.Gl). The intraocular pressure (IOP), the active substances of the applied IOP-lowering drugs, the best corrected visual acuity (BCVA) and the mean deviation (MD) of the perimetry were measured at baseline and at regular follow-ups, scheduled at 2 days and 1, 3, 6 and 12 months after surgery.

RESULTS

153 eyes were included in this analysis. 113 eyes were affected by POAG (74%), 5 eyes by NTG (3%), 22 eyes by PEX (14%) and 13 eyes by Sec. Gl (9%). Mean IOP decreased in all treatment groups during the 12 months of follow-up (complete group: 23.9 ± 7.4 to 15.4 ± 5.1 mmHg (p < 0.01); POAG: 22.8 ± 6.5 to 15.1 ± 4.6 mmHg (p < 0.01); NTG: 16.6 ± 3.4 to 11.6 ± 2.2 mmHg (p < 0.05); PEX: 28.0 ± 7.9 to 17.1 ± 6.6 mmHg (p < 0.01); Sec.Gl: 28.9 ± 13.9 to 15.5 ± 6.9 mmHg (p < 0.05)). In the 153 eyes the average number of IOP-lowering drugs applied decreased from 2.6 ± 1.2 to 0.8 ± 1.3 12 months after surgery (p < 0.01). BCVA and mean deviation of automated standard perimetry remained stable in all groups during follow-up.

CONCLUSION

As in eyes suffering from POAG, IOP and number of IOP-lowering drugs applied can be effectively reduced by XEN implantation in eyes suffering from NTG, PEX and secondary glaucoma while leaving BCVA and visual field unchanged.

TRIAL REGISTRATION

Trial was registered at DRKS (registration number: DRKS00020800 , Registered 25.February 2020 - Retrospectively registered).

Influences of Hypomagnesemia on Optic Nerve and Retinal Vascular Structure Determined Using Optical Coherence Tomography (OCT) Angiography

Purpose: To evaluate the effects of low blood magnesium levels on the optic nerve, retina, and retinal vascular structure.Methods: This observational and cross-sectional study was conducted between June 2019 and May 2020 with participants aged 20-39 years, who had a visual acuity of ≥20/20, the axial length of 22-24.5 mm, refractive defect spherical equivalent of ≤±3D, and intraocular pressure of ≤21 mm Hg. All participants had a complaint of twitching in their eyes. The participants with normal serum magnesium levels constituted the control group, and patients with hypomagnesemia constituted the patient group. Updated AngioScan software (Navis ver. 1.8.0.) of Nidek's RS-3000 Advance system was used to analyze the spectral domain-optical coherence tomography (SD-OCT) and optical coherence tomography-angiography (OCT-A) images.Results: A total of 100 right eyes of 100 individuals was included in the study. The mean retinal nerve fiber layer (RNFL) thickness was 108.52 ± 12.46 μm in the control group, and 97.3 ± 9.7 μm in the hypomagnesemia group (P < .001). In the control group, the global superficial capillary plexus (SCP) and deep capillary plexus (DCP) vessel densities (VDs) were 41.92 ± 2.29, and 37.54 ± 3.83, respectively. In the patient group, the global SCP and DCP VDs were 37.66 ± 3.14, and 32.95 ± 5.57, respectively. The SCP and DCP VD percentages were significantly lower in the patient group. The mean foveal avascular zone (FAZ) area, perimeter and circularity index (CI) were 0.32 ± 0.13 mm², 2.89 ± 0.59 mm, and 0.52 ± 0.09, respectively, for the control group and 0.38 ± 0.11 mm², 2.99 ± 0.64 mm, and 0.38 ± 0.1, respectively, for the patient group. The FAZ area and perimeter were significantly higher (P = .013 and P = .001) and FAZ CI was significantly lower (P < .001) in the patients with hypomagnesemia.Conclusion: Our study revealed that OCT and OCT-A measurements may be used in the determination of the optic nerve and retinal vascular structure changes in hypomagnesemia.

PROGNOSIS OF POSTOPERATIVE PROGRESSION OF GLAUCOMA OPTIC NEUROPATHY AT PRIMARY OPEN-ANGLE GLAUCOMA

Search for new informative markers and methods of prognosis prediction glaucomatous optic neuropathy (GON) in primary open-angle glaucoma (POAG) is an urgent task. We have established efficiency surgical treatment of POAG, but the progression of GON is observed in 10–15 % patients. It is known that the main mechanism of GON is apoptotic death retinal ganglion cells, a marker of which is recognized as tumour necrosis factor-α (TNFα), Fas-ligand (FasL) and a soluble form of the Fas-receptor (sFas/APO-1). The aim of the study: to find out the possibility of using apoptosis factors (TNFα, FasL and sFas/APO-1) to predict postoperative progression of GON at POAG. Methods. 69 patients (69 eyes) with POAG stage I–III were examined, who underwent trabeculectomy with implantation of an Ex-Press shunt. In intraocular fluid (IOF) markers of apoptosis was determined by the method enzyme-linked immunosorbent assay. Repeated ophthalmological examination was performed in 1 year. The control group consisted of 25 patients who were operated on about phacoemulsification of cataracts. For statistical and regression analysis used software package GLZ (Statistica 10, StatSoft, Inc. USA) and module of analysis of operational characteristics of regression models – ROC-diagrams (MedCalc 18.9.1, MedCalc Software, Belgium). Results. Multivariate regression analysis showed that the progression of GON determine the content in IOF of TNFα and sFas/Apo-1 before surgery and intraocular pressure after three months. Based on these indicators, it is calculated satisfactory model of GON progression prediction with 95.4 % accuracy. One-factor logistic regression analysis proved the influence of the content of TNFα, FasL and sFas/Apo-1 for the presence or absence of progression of GON during the year after operations: direct dependence took place for TNFα and FasL and inverse – for sFas/Apo-1. The critical limits of the content in the IOF markers are calculated apoptosis, in which the progression of GON is unmistakably predicted during year after surgery. Conclusions. The obtained results prove the significant influence of the studied markers apoptosis on the progression of GON after surgery. Direct pathogenetic influence belongs to TNFα and FasL.

Long Non-coding RNA MALAT1 Alleviates the Elevated Intraocular Pressure (Eiop)-induced Glaucoma Progression via Sponging miR-149-5p

Background: Glaucoma is an optic neuropathic disease and contributed to the irreversible blindness caused by the slow death of retinal ganglion cells (RGCs). Long non-coding RNA (lncRNA) metastasis associated lung adenocarcinoma transcript 1 (MALAT1) was reported to be aberrantly expressed in diverse diseases, including glaucoma. However, the mechanism of MALAT1 in glaucoma was still undefined.Methods: The levels of MALAT1, microRNA-149-5p (miR-149-5p) in RGCs cultured under elevated pressure were measured by quantitative real-time polymerase chain reaction (qRT-PCR). The putative target of MALAT1 was predicted by starBase v2.0 online database, and dual luciferase reporter assay, RNA immunoprecipitation (RIP) assay and RNA pull-down assay were performed to verify this interaction. The cell viability of RGCs was measured by Cell Counting Kit-8 (CCK-8) assay. The apoptotic rate was evaluated via flow cytometry. The protein levels of apoptosis-related proteins (Bax, B-cell lymphoma 2 (Bcl-2)) and Cleaved caspase 3 were assessed by Western blot.Results: The level of MALAT1 was significantly down-regulated, and the level of miR-149-5p was distinctly up-regulated in RGCs under pressure in a dose-dependent manner. Functionally, MALAT1 overexpression or miR-149-5p inhibitor alleviated the inhibitory effect on cell viability and the promoted effect on apoptotic rate of RGCs in EIOP. The interaction between MALAT1 and miR-149-5p was predicted by starBase v2.0 online database, and dual luciferase reporter assay, RIP assay and RNA pull-down assay validated the interaction. Combined with the loss and gain experiment results, miR-149-5p was negatively interacted with MALAT1. Furthermore, miR-149-5p mimics mitigated the promoted impact on cell viability and the suppressive impact on apoptotic rate by targeting MALAT1.Conclusion: MALAT1 promoted cell proliferation and inhibited cell apoptosis of RGCs via targeting miR-149-5p in glaucoma in vitro, which might shed light on the mechanism of glaucoma pathogenesis.

Comparing the efficacy of trabeculectomy and XEN gel microstent implantation for the treatment of primary open-angle glaucoma: a retrospective monocentric comparative cohort study

The aim of this study was to compare the efficacy and safety profile of XEN microstent implantation with trabeculectomy (TET) in a comparable group of open-angle glaucoma cases in a retrospective, monocentric, single-surgeon setting. Each treatment group consisted of 100 eyes of 100 patients. At regular follow-up visits during the first 12 months after surgery, the following assessments were conducted and compared: intraocular pressure (IOP), number of IOP-lowering medications applied, best-corrected visual acuity (BCVA) and visual field testing. In both groups mean IOP was significantly reduced (p < 0.001). Mean IOP dropped from 24.8 ± 7.8 to 14.8 ± 4.0 mmHg in the TET and from 24.5 ± 6.7 to 16.6 ± 4.8 mmHg in the XEN group. The number of active compounds in the prescribed medication dropped from 3.3 ± 1.2 to 1.3 ± 1.4 in the TET and from 3.0 ± 1.1 to 1.4 ± 1.5 in the XEN group. BCVA and mean defect of static automated perimetry did not show a change of statistical significance in either group. Complications were more frequent after TET (p = 0.005) while postoperative needling was more frequent in the XEN group (p = 0.021). TET and XEN led to a significant reduction of IOP and IOP-lowering medication, while BCVA and visual field indices remained mostly unaltered over a 12-month postsurgical follow-up.

Ganglion Cell Layer Thinning in Alzheimer's Disease

The main advantages of optical retinal imaging may allow researchers to achieve deeper analysis of retinal ganglion cells (GC) in vivo using optical coherence tomography (OCT). Using this device to elucidate the impact of Alzheimer’s disease (AD) on retinal health with the aim to identify a new AD biomarker, a large amount of studies has analyzed GC in different stages of the disease. Our review highlights recent knowledge into measuring retinal morphology in AD making distinctive between whether those studies included patients with clinical dementia stage or also mild cognitive impairment (MCI), which selection criteria were applied to diagnosed patients included, and which device of OCT was employed. Despite several differences, previous works found a significant thinning of GC layer in patients with AD and MCI. In the long term, an important future direction is to achieve a specific ocular biomarker with enough sensitivity to reveal preclinical AD disorder and to monitor progression.

Effect of palmitoylethanolamide on inner retinal function in glaucoma: a randomized, single blind, crossover, clinical trial by pattern-electroretinogram

Glaucoma is a neurodegenerative disease, our study aimed to evaluate the potential effects of Palmitoylethanolamide (PEA) supplementation on RGCs function by PERG examination, and to record effects on intraocular pressure, visual field and quality of life. It was a single centre, randomized, prospective, single blind, two treatment, two period crossover study on stable glaucoma patients on topical monotherapy comparing current topical therapy alone or additioned with PEA 600 mg one tablet a day. At baseline, at 4 and at 8 months, all patients underwent to complete ophthalmic examination, pattern electroretinogram, visual field, and quality of life evaluation. 40 patients completed the study: mean age 66.6 ± 7.6 years; 21 (52.5%) male; 35 POAG (87.5%). At baseline, most patients had an early visual field defect, the IOP was well controlled. At the end of the PEA 600 mg supplementation, a significantly higher (mean 0.56 μV, 95% CI 0.30–0.73, p < 0.001) in the P50-wave amplitude was observed; in the PEA period a significantly lower IOP (− 1.6 mmHg, 95% CI − 2 to 1.2, p < 0.001) and higher quality of life scores (+ 6.7, 95% CI 4–9.9, p < 0.001) were observed. Our study is the first to show promising effects of PEA on PERG and on quality of life in glaucoma patients.

Neuroprotective effects of low-dose G-CSF plus meloxicam in a rat model of anterior ischemic optic neuropathy

Non-arteritic anterior ischemic optic neuropathy (NAION) causes a sudden loss of vision and lacks effective treatment. Granulocyte colony-stimulating factor (G-CSF) provides neuroprotection against the experimental optic nerve injuries but also induce leukocytosis upon typical administration. We found synergetic neuroprotective effects of meloxicam and low dose G-CSF without leukocytosis in a rat model of anterior ischemic optic neuropathy (rAION). The WBC counts in the low-dose G-CSF-plus meloxicam-treated group were similar to the sham-operated group. Combination treatment of low-dose G-CSF plus meloxicam preserved RGCs survival and visual function, reduced RGC apoptosis and the macrophages infiltration, and promote more M2 phenotype of macrophage/microglial transition than the low-dose GCSF treatment or the meloxicam treatment. Moreover, the combination treatment induced higher serine/threonine kinase 1 (Akt1) expression. The combination treatment of low-dose G-CSF plus meloxicam lessened the leukocytotic side effect and provided neuroprotective effects via Akt1 activation in the rAION model. This approach provides crucial preclinical information for the development of alternative therapy in AION.

Natural Plant Extract Berbamine Is a Potent Inhibitor of Cell Growth and Survival of Human Tenon's Fibroblasts

INTRODUCTION

Post-trabeculectomy scarring due to excessive proliferation of human Tenon's fibroblasts (HTFs) often led to operation failure. Developing a new anti-fibrosis drug with high efficacy to inhibit HTF cell growth will greatly improve the effectiveness of trabeculectomy.

OBJECTIVE

This study aims to investigate the effect of berbamine (BBM) treatment on the cell growth and survival of HTFs.

METHODS

Cultured human fetal Tenon's fibroblasts (HFTFs) were treated with or without different concentrations of BBM. Cell morphology was observed with a phase contrast microscope. A CCK-8 method and Ki67 immunofluorescence were used to determine cell viability and cell proliferation. A scratch test was used to study cell migration. Flow cytometry and TUNEL staining were performed to detect cell apoptosis. The expression of BAX/BCL-2, ERK, and AKT/mTOR pathway components was determined by Western blotting.

RESULTS

BBM treatment disrupted HFTF normal morphology and inhibited its cell growth in a dose-dependent manner. Ki67 immunofluorescence and scratch assay showed BBM suppressed HFTF cell proliferation and migration. Importantly, BBM dose-dependently increased the BAX/BCL-2 ratio and induced apoptosis in HFTF cells. Western blotting showed BBM significantly inhibited the ERK and AKT/mTOR pathway, and PTEN inhibition ameliorated the inhibitory effect of BBM on cell viability and survival in HFTFs.

CONCLUSIONS

BBM potently inhibits the cell growth and survival of HTFs through AKT/mTOR and has the potential to serve as an anti-fibrosis drug after trabeculectomy.

Elevated Intraocular Pressure Causes Abnormal Reactivity of Mouse Retinal Arterioles

Objective

Glaucoma is a leading cause of severe visual impairment and blindness. Although high intraocular pressure (IOP) is an established risk factor for the disease, the role of abnormal ocular vessel function in the pathophysiology of glaucoma gains more and more attention. We tested the hypothesis that elevated intraocular pressure (IOP) causes vascular dysfunction in the retina.

Methods

High IOP was induced in one group of mice by unilateral cauterization of three episcleral veins. The other group received sham surgery only. Two weeks later, retinal vascular preparations were studied by video microscopy in vitro. Reactive oxygen species (ROS) levels and expression of hypoxia markers and of prooxidant and antioxidant redox genes as well as of inflammatory cytokines were determined.

Results

Strikingly, responses of retinal arterioles to stepwise elevation of perfusion pressure were impaired in the high-IOP group. Moreover, vasodilation responses to the endothelium-dependent vasodilator, acetylcholine, were markedly reduced in mice with elevated IOP, while no differences were seen in response to the endothelium-independent nitric oxide donor, sodium nitroprusside. Remarkably, ROS levels were increased in the retinal ganglion cell layer including blood vessels. Expression of the NADPH oxidase isoform, NOX2, and of the inflammatory cytokine, TNF-α, was increased at the mRNA level in retinal explants. Expression of NOX2, but not of the hypoxic markers, HIF-1α and VEGF-A, was increased in the retinal ganglion cell layer and in retinal blood vessels at the protein level.

Conclusion

Our data provide first-time evidence that IOP elevation impairs autoregulation and induces endothelial dysfunction in mouse retinal arterioles. Oxidative stress and inflammation, but not hypoxia, appear to be involved in this process.

Therapeutic Effects of Puerarin Against Anterior Ischemic Optic Neuropathy Through Antiapoptotic and Anti-Inflammatory Actions

Purpose

This study investigated the therapeutic effects of puerarin (PR) on a rat model of anterior ischemic optic neuropathy (rAION).

Methods

The neuroprotective effects of PR on rAION were evaluated using flash visual-evoked potentials (FVEP), retrograde labeling of retinal ganglion cells (RGCs), TUNEL assay of the retina, optical coherence tomography (OCT) images of optic nerve width, and ED1 staining of the optic nerve (ON). The inflammatory response of ON and Akt signaling pathways were analyzed through Western blot. M2 polarization was determined by immunostaining and immunoblotting in ONs.

Results

In FVEP analysis, the amplitude of P1-N2 and the RGC density in the PR-treated group were 2.3- and 1.6-fold higher than those in the PBS-treated group, respectively (P < 0.05). The number of apoptotic RGC in the PR-treated group was 2.8-fold lower than that in the PBS-treated group. OCT images demonstrated that PR treatment-reduced ON edema in the acute phase compared to PBS treatment (P < 0.05). Macrophage infiltration was reduced by 5.2-fold by PR treatment compared with the PBS treatment (P < 0.05). PR treatment inhibited the levels of iNOS, IL-1β, and TNF-α, induced the levels of IL-10, Arg1, and Fizz1 in the rAION model. The levels of p-Akt1 and C/EBPβ in the PR-treated group increased by 3.4-fold and 5.89-fold compared with those in the PBS-treated group (P < 0.05). Inhibition of Akt activation reduced the number of M2 macrophage in the PR-treated group (P < 0.05).

Conclusions

PR treatment provided the neuroprotective effects in the rAION model, which may lead to new clinical applications.

The effects of intravitreal H2 S application on apoptosis in the retina and cornea in experimental glaucoma model

One of the most important causes of visual loss (blindness) is glaucoma, which occurs due to the degeneration of the ganglion cells in retina. It has been shown that hydrogen sulphide (H₂ S) acts an antioxidant, neuroprotective and neuromodulator and provides protection against oxidative stress and apoptosis. This study aims to examine through which apoptotic pathway H₂ S acts in experimental glaucoma model. Twenty-two male wistar albino rats were used in this study. Group 1 (n = 6, control group): Intravitreal saline was given in the third week without inducing ocular hypertension (OHT) with laser photocoagulation. Group 2 (n = 8): After the induction of OHT with laser photocoagulation, intravitreal saline was given in the third week. Group 3 (n = 8): After the induction of OHT with laser photocoagulation, intravitreal H₂ S's donor sodium hydrosulphide (NaSH) 100 nmol/L was given in the third week. At the end of the 6th week, the eyes of the rats were sacrified under anaesthesia and extracted and then routine tissue follow-up was undertaken. Besides haematoxylin & eosin (H&E) staining, Bax, Bcl-2, p53 and caspase-3 activation were examined immunohistochemically in the retina and the cornea. This showed that ocular hypertension caused apoptosis through the intrinsic pathway, due to Bax and caspase-3 activation, in both retina and cornea, and that this led to DNA damage due to p53 activation. Also, we found that H₂ S exposure in glaucoma distinctly suppressed Bax, caspase-3 and p53 activations in retina but that it has a limited effect on the cornea. According to these results, glaucoma caused apoptosis in the retina through intrinsic pathway, and the damage to the retina could be compensated partially by H₂ S but would have limited on the cornea.

Possible therapeutic effect of magnesium in ocular diseases

Magnesium (Mg2+) is one of the major elements required to maintain normal metabolism and ionic balances in ocular tissues. The physiological role of Mg2+ is mediated through maintaining the Na+-K+-ATPase on membrane, favoring energy-generating reactions, replication of DNA and protein synthesis. Despite the wide availability of this element, hypomagnesemia has been associated with many human ailments. Recent studies highlighted the association of hypomagnesemia and, thereby, supplementation of Mg2+ in the management of eye diseases. Glaucoma, senile cataract and diabetic retinopathy were associated with low level of extracellular Mg2+. The neurovascular protective effects of Mg2+ mediated through activation of endothelial nitric oxide synthase and inhibition of endothelin-1 eventually result in vasodilatation of retinal vessels. Mg2+ can maintain the lens sodium pump activity and antioxidant status and block the calcium channels and release of glutamate in nerve endings. Furthermore, it can prevent the apoptosis of retinal ganglion cells. All these effects contribute to its being a pharmacological agent against ocular diseases. However, clinical trials are scant. This article discusses the role of Mg2+ as a possible therapeutic agent in the management of glaucoma, cataract and diabetic retinopathy.

Topographic correlation and asymmetry analysis of ganglion cell layer thinning and the retinal nerve fiber layer with localized visual field defects

Purpose

To evaluate the accuracy of the measurement of the ganglion cell layer (GCL) of the posterior pole analysis (PPA) software of the Spectralis spectral-domain (SD) optical coherence tomography (OCT) device (Heidelberg Engineering, Inc., Heidelberg, Germany), the asymmetry of paired GCL sectors, the total retinal thickness asymmetry (RTA), and the peripapillary retinal nerve fiber layer (pRNFL) test to discriminate between healthy, early and advanced glaucoma eyes.

Methods

Three hundred eighteen eyes of 161 individuals with reliable visual fields (VF) were enrolled in this study. All participants were examined using the standard posterior pole and the pRNFL protocols of the Spectralis OCT device. VF impairment was graded in hemifields, and the GCL sectors were correlated with this damage. Thicknesses of each GCL, the GCL map deviation asymmetry and the pRNFL were compared between control and glaucomatous eyes. The area under the receiver operating characteristic curve (AUC) of these analyses was assessed.

Results

Fourteen of the 16 sectors of the GCL and pRNFL were significantly thinner in eyes with glaucoma than in control eyes (p<0.006). Similarly, the GCL map deviation showed a significant difference between these eyes and both the control eyes as well as the eyes with early glaucoma (p = 0.001 and p = 0.039, respectively). The highest values of AUC to diagnose both early and advanced glaucoma corresponded to the average pRNFL analysis and the GCL map deviation (AUC>0.823, p<0.040 and AUC>0.708, p<0.188, respectively).

Conclusions

Although 16 central sectors of the GCL observed with PPA showed good correlation with VF damage, the pRNFL and the GCL map deviation were more effective for discrimination of glaucomatous damage.

Effect of Resveratrol on In Vitro and In Vivo Models of Diabetic Retinophathy: A Systematic Review

A large number of preclinical studies suggest the involvement of resveratrol in the prevention and treatment of eye diseases induced by oxidative stress and inflammation. We tested the hypothesis that resveratrol influences many pathways of in vitro and in vivo models of diabetic retinopathy through a systematic literature review of original articles. The review was conducted in accordance with the PRISMA guidelines. A literature search of all original articles published until April 2019 was performed. The terms “resveratrol” in combination with “retina”, “retinal pathology”, “diabetic retinopathy” and “eye” were searched. Possible biases were identified with the adopted SYRCLE’s tool. Eighteen articles met inclusion/exclusion criteria for full-text review. Eleven of them included in vitro experiments, 11 studies reported in vivo data and 3 studies described both in vitro and in vivo experiments. Most of the in vivo studies did not include data that would allow exclusion of bias risks, according to SYRCLE’s risk of bias tool. Both in vitro and in vivo data suggest anti-apoptotic, anti-inflammatory and anti-oxidative actions of resveratrol in models of diabetic retinopathy. However, results on its anti-angiogenic effects are contradictory and need more rigorous studies.

Potential role of P2X7 receptor in neurodegenerative processes in a murine model of glaucoma

Glaucoma is a common cause of visual impairment and blindness, characterized by retinal ganglion cell (RGC) death. The mechanisms that trigger the development of glaucoma remain unknown and have gained significant relevance in the study of this neurodegenerative disease. P2X7 purinergic receptors (P2X7R) could be involved in the regulation of the synaptic transmission and neuronal death in the retina through different pathways. The aim of this study was to characterize the molecular signals underlying glaucomatous retinal injury. The time-course of functional, morphological, and molecular changes in the glaucomatous retina of the DBA/2J mice were investigated. The expression and localization of P2X7R was analysed in relation with retinal markers. Caspase-3, JNK, and p38 were evaluated in control and glaucomatous mice by immunohistochemical and western-blot analysis. Furthermore, electroretinogram recordings (ERG) were performed to assess inner retina dysfunction. Glaucomatous mice exhibited changes in P2X7R expression as long as the pathology progressed. There was P2X7R overexpression in RGCs, the primary injured neurons, which correlated with the loss of function through ERG measurements. All analyzed MAPK and caspase-3 proteins were upregulated in the DBA/2J retinas suggesting a pro-apoptotic cell death. The increase in P2X7Rs presence may contribute, together with other factors, to the changes in retinal functionality and the concomitant death of RGCs. These findings provide evidence of possible intracellular pathways responsible for apoptosis regulation during glaucomatous degeneration.

Voluntary running delays primary degeneration in rat retinas after partial optic nerve transection

Running is believed to be beneficial for human health. Many studies have focused on the neuroprotective effects of voluntary running on animal models. There were both primary and secondary degeneration in neurodegenerative diseases, including glaucoma. However, whether running can delay primary or secondary degeneration or both of them was not clear. Partial optic nerve transection model is a valuable glaucoma model for studying both primary and secondary degeneration because it can separate primary (mainly in the superior retina) from secondary (mainly in the inferior retina) degeneration. Therefore, we compared the survival of retinal ganglion cells between Sprague-Dawley rat runners and non-runners both in the superior and inferior retinas. Excitotoxicity, oxidative stress, and apoptosis are involved in the degeneration of retinal ganglion cells in glaucoma. So we also used western immunoblotting to compare the expression of some proteins involved in apoptosis (phospho-c-Jun N-terminal kinases, p-JNKs), oxidative stress (manganese superoxide dismutase, MnSOD) and excitotoxicity (glutamine synthetase) between runners and non-runners after partial optic nerve transection. Results showed that voluntary running delayed the death of retinal ganglion cells vulnerable to primary degeneration but not those to secondary degeneration. In addition, voluntary running decreased the expression of glutamine synthetase, but not the expression of p-JNKs and MnSOD in the superior retina after partial optic nerve transection. These results illustrated that primary degeneration of retinal ganglion cells might be mainly related with excitotoxicity rather than oxidative stress; and the voluntary running could down-regulate excitotoxicity to delay the primary degeneration of retinal ganglion cells after partial optic nerve transection.

The Role of Endogenous Neuroprotective Mechanisms in the Prevention of Retinal Ganglion Cells Degeneration

Retinal neurons are not able to undergo spontaneous regeneration in response to damage. A variety of stressors, i.e., UV radiation, high temperature, ischemia, allergens, and others, induce reactive oxygen species production, resulting in consecutive alteration of stress-response gene expression and finally can lead to cell apoptosis. Neurons have developed their own endogenous cellular protective systems. Some of them are preventing cell death and others are allowing functional recovery after injury. The high efficiency of these mechanisms is crucial for cell survival. In this review we focus on the contribution of the most recently studied endogenous neuroprotective factors involved in retinal ganglion cell (RGC) survival, among which, neurotrophic factors and their signaling pathways, processes regulating the redox status, and different pathways regulating cell death are the most important. Additionally, we summarize currently ongoing clinical trials for therapies for RGC degeneration and optic neuropathies, including glaucoma. Knowledge of the endogenous cellular protective mechanisms may help in the development of effective therapies and potential novel therapeutic targets in order to achieve progress in the treatment of retinal and optic nerve diseases.

Did you choose appropriate tracer for retrograde tracing of retinal ganglion cells? The differences between cholera toxin subunit B and Fluorogold

Cholera toxin subunit B (CTB) and Fluorogold(FG) are two widely utilized retrograde tracers to assess the number and function of retinal ganglion cells (RGCs). However, the relative advantages and disadvantages of these tracers remain unclear, which may lead to their inappropriate application. In this study, we compared these tracers by separately injecting the tracer into the superior Colliculi (SC) in rats, one or 2 weeks later, the rats were sacrificed, and their retinas, brains, and optic nerves were collected. From the first to second week, FG displayed a greater number of labeled RGCs and a larger diffusion area in the SC than CTB; The number of CTB labeled RGCs and the diffusion area of CTB in the SC increased significantly, but there was no distinction between FG; Furthermore, CTB exhibited more labeled RGC neurites and longer neurites than FG, but no difference was evident between the same trace; The optic nerves labeled using CTB were much clearer than those labeled using FG. In conclusion, both CTB and FG can be used for the retrograde labeling of RGCs in rats at 1 or 2 weeks. FG achieves retrograde labeling of a greater number of RGCs than CTB, whereas CTB better delineates the morphology of RGCs. Furthermore, CTB seems more suitable for retrograde labeling of some small, non-image forming nuclei in the brain to which certain RGC subtypes project their axons.

CD200Fc Attenuates Retinal Glial Responses and RGCs Apoptosis After Optic Nerve Crush by Modulating CD200/CD200R1 Interaction

To explore the hypothesis that CD200Fc, a CD200R1 agonist with anti-inflammatory properties, will inhibit retinal glial cells hyperactivation and retinal ganglion cells (RGCs) apoptosis after optic nerve injury. CD200Fc was immediately administered after optic nerve crush (ONC) once by intravitreal injection. Rats were euthanized at 5 days after ONC. The density of RGCs was counted by immunostaining of retina flat mounts for Brn3a. TUNEL assay, immunoblotting analysis of ionized calcium-binding adapter molecule 1(iba1) (microglia marker) and glial fibrillary acidic protein (GFAP) (astrocytes and Müller cells marker), RT-PCR analysis of cyclooxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS), monocyte chemotactic protein 1 (MCP-1), tumor necrosis factor-α (TNF-α), interleukin (IL)-8 and IL-10, ELISA measure protein levels of inflammatory cytokines and western blot analysis of CD200 and CD200R1 were evaluated. CD200Fc treatment suppressed ONC-induced RGCs loss through inhibition of RGCs apoptosis. Additionally, expression of glial cells activation markers GFAP and iba1 and production of pro-inflammatory cytokines (COX-2, iNOS, MCP-1, TNF-α, IL-8) were decreased in CD200Fc treated animals after ONC. Meanwhile, anti-inflammatory cytokine IL-10 was increased by CD200Fc treatment in ONC-induced rat retina. Finally, we found that CD200Fc significantly inhibited ONC-induced increased in expression of CD200 and raised the already high basal CD200R1 expression in the rat retina after ONC. Our results demonstrated that the anti-inflammatory effects of CD200Fc in ONC rats model through inhibited the activation of retinal glial cells via the interaction between CD200 and CD200R1, and the neuroprotective effects of CD200Fc on RGCs thought inhibited its apoptosis.