Glaucoma Model Research Articles

Analysis of vitreous by optical coherence tomography as biomarker in neurodegenerative diseases

Purpose: Neurodegeneration is multifactorial and the immune factor is key. Chronic and acute inflammation can be analysed as hyperreflective opacities in the vitreous (HOV) by optical coherence tomography (OCT) imaging. This study analyzes vitreous cellularity by OCT in two neurodegenerative diseases, chronic glaucoma (CG) and relapsing remitting multiple sclerosis (RRMS) compared to healthy individuals.Methods: Four models of CG generated in rats by episcleral veins sclerosis (EVS n = 35) or injection of biodegradable microspheres into the anterior chamber of the eye non‐loaded (Ms n = 28) and loaded with dexamethasone (Dex n = 43) and Dex‐fibronectin (DexFibro n = 44), compared to healthy rats (n = 32). In addition, patients with RRMS treated (n = 20) and healthy subjects (n = 20) were analysed. The relative intensity of vitreous/retinal pigment epithelium (VIT/RPE) obtained from OCT (for animal and human use) images was quantified. A custom program computational analysis characterizes in vivo the HOV (number and size), identified histologically as hyalocyte‐like Iba‐1+ (microglial marker) cells in animals. For humans, artificial intelligence methods and Image J software were used.Results: Both image analysis techniques identified HOV in animals with chronic glaucoma, in patients with RRMS and in healthy (both animals and humans). Chronic glaucoma models presented more HOV than healthy (decreasing from 100 ‐EVS‐ to 15 ‐healthy‐) (p < 0.05). Corticosteroid models presented an anti‐inflammatory profile (with non‐activated cells as the highest population). However, according VIT/RPE intensity, patients with RRMS treated did not show differences vs. healthy humans (p > 0.44).Conclusions: HOV analysed by OCT were identified in neurodegenerative diseases of chronic course, in outbreaks, and healthy individuals. The presence of anti‐inflammatory drugs (dexamethasone in animals) and immunemodulators (in humans) decreased the VIT/RPE intensity resembling healthy conditions.Acknowledgments: Grants MAT2017‐83858‐C2‐1 and MAT2017‐83858‐C2‐2 funded by MCIN/AEI/ 10.13039/501100011033 and by “ERDF A way of making Europe”. Grants PID2020‐113281RB‐C21 and PID2020‐113281RB‐C22 funded by MCIN/AEI/ 10.13039/501100011033. Research Group UCM920415 (InnOftal). MJR thanks for the grants M17/00213 and JR22_00057.

RNA‐binding protein ELAVL1‐mediated neuroprotection of retinal ganglion cells

Aims/Purpose: To evaluate the impact of ELAVL1 overexpression on survival and function of retinal ganglion cells (RGC) in rat glaucoma model.Methods: The study included ex vivo and in vivo approaches. Ex vivo, we used rat retinal explants to investigate, whether AAV‐ELAVL1 delivery affects the survival of RGC in the degeneration model induced by axotomy. In vivo approach investigated histology and function of RGC in rat glaucoma model. Rats received intravitreal injection of AAV‐ELAVL1, AAV‐ELAVL1(S202A) or AAV‐control. To induce chronic glaucoma, unilateral episcleral vein cauterization was performed. Animals underwent electroretinography tests (ERG) during the experiment. Collected retinas and optic nerves were processed for immunostainings, western blots, and stereology.Results: In ex vivo retinal explants culture, the RGC count was 162 ± 35, 148 ± 22 and 149 ± 28 for AAV‐ELAVL1, AAV‐ELAVL1(S202A) and control, respectively (p < 0.03). The IOP values were similar in all experimental groups, and on average, they were significantly higher than in healthy eyes (p < 0.001). In retinal histology, clear neuroprotective effect in the AAV‐ELAVL1 group was observed. After AAV therapy, both constructs (ELAVL1 and ELAVL1(S202A) showed a significant increase in protein expression in RGC, which was also associated with a significant increase in the expression of BDNF in the retinas, especially after AAV‐ELAVL1 treatment. In functional tests, the PhNR response was significantly reduced in AAV‐control glaucoma (p < 0.001). The application of AAV‐ELAVL1 treatment resulted in the preservation of RGC function at a level very similar to the situation before the induction of glaucoma.Conclusions: The AAV‐ELAVL1 approach showed a very strong neuroprotective effect in a rat glaucoma model. The neuroprotective effect is associated with antioxidant and anti‐inflammatory activity with the increase in BDNF expression, which intensifies the neuroprotective effect.

Near-infrared activated liposomes for neuroprotection in glaucoma.

Neurodegenerative diseases have a profound impact on vision, leading to conditions such as glaucoma, optic neuropathy, and diabetic retinopathy, affecting millions worldwide. These diseases are characterized by the degeneration of retinal ganglion cells (RGCs), resulting in a progressive loss of visual acuity and field, with the threat of irreversible blindness. However, existing treatments, such as eye drops, direct injections, and laser surgeries face significant challenges due to limited efficacy and potential infection. The inefficiency of traditional corneal drug delivery methods is a major obstacle in treating vision neurodegenerative diseases. To address these challenges, we developed a remotely triggered on-demand liposomal delivery system to treat glaucomatous neurodegeneration in mice. We utilized the localized surface plasmon resonance (LSPR) effect of gold nanorods (AuNRs) under near-infrared (NIR) light (808 nm) to control the release of cyclodextrin-encapsulated melatonin from thermally responsive liposomal nanocarriers in the vitreous humor. Due to the transparency of the eye's cornea, NIR light can penetrate deep tissues, enabling on-demand drug delivery to the retina. By enhancing the drug's solubility and stability through cyclodextrin encapsulation, this remotely activated melatonin/HPβCD AuNRs liposomes delivery system can decrease intraocular pressure (IOP) elevation by (24 ± 7)%, enhance the survival rate of RGCs by (77 ± 6)%, and decrease glial fibrillary acidic protein (GFAP) activation by (75 ± 6)% at depth in an acute experimental glaucoma model. This NIR-triggered drug delivery system presents the potential of a promising minimally photo-triggered therapeutic option for glaucoma treatment.

Germacrone Protects against NF-κB-Mediated Inflammatory Signaling, Apoptosis, and Retinal Ganglion Cell Survival in a Rat Glaucoma Model.

Retinal ischemia-reperfusion (I/R) is a pathological phenomenon that causes cellular destruction in several ocular disorders, so there is a need for novel possible neuroprotective drugs. Researchers have reported numerous neuroprotective effects of Germacrone (GM). Therefore, this study aimed to elucidate the underlying processes of GM that may contribute to glaucoma development. 40 healthy rats underwent retinal ischemia-reperfusion (I/R) damage. The animals were divided into control, I/R-induced, GM-1d, and GM-7d. After 7 days of I/R, mice were sacrificed and retinal tissue removed. An enzyme-linked immunosorbent assay (ELISA) was used to assess retinal Malondialdehyde (MDA) and 8-OHdG levels after oxidative injury. The Fluro-Gold (FG) labelling assay counted retinal ganglion cells (RGC) before and after labelling. DNA from retinal tissue RNA was amplified. Western blotting and real-time qRT-PCR were utilised to assess Bax, Casapses-3, Bcl-2, retinal NF-kB, and COX-2 expression. Retinal cell apoptotic mediator expression was measured by a TUNEL assay. Retinal I/R damage increases ganglion cell death. Long-term GM treatment (GM-7d) reduced NF-κB activation and raised COX-2 expression, which suggests antioxidant potential. TUNEL-positive apoptotic cells were reduced in long-term GM-treated rats. In GM-treated retinas, the Bax-Bcl-2 ratio was identical to the control group and significantly different from the I/R group. GM reduces I/R-induced retinal cell damage by inhibiting RG cell death. Seven days after GM therapy, histology showed retinal tissue loss. NF-κB signaling and intrinsic mitochondrial apoptosis are possible mechanisms that may be attenuated by GM and are attributed to a retinal protective effect.

P38 MAPK inhibitor SB202190 suppresses ferroptosis in the glutamate-induced retinal excitotoxicity glaucoma model.

JOURNAL/nrgr/04.03/01300535-202410000-00031/figure1/v/2024-02-06T055622Z/r/image-tiff Glutamate excitotoxicity has been shown to play an important role in glaucoma, and glutamate can induce ferroptosis. The p38 mitogen-activated protein kinase (MAPK) pathway inhibitor SB202190 has a potential ability to suppress ferroptosis, and its downstream targets, such as p53, have been shown to be associated with ferroptosis. However, whether ferroptosis also occurs in retinal ganglion cells in response to glutamate excitotoxicity and whether inhibition of ferroptosis reduces the loss of retinal ganglion cells induced by glutamate excitotoxicity remain unclear. This study investigated ferroptosis in a glutamate-induced glaucoma rat model and explored the effects and molecular mechanisms of SB202190 on retinal ganglion cells. A glutamate-induced excitotoxicity model in R28 cells and an N-methyl-D-aspartate-induced glaucoma model in rats were used. In vitro experiments showed that glutamate induced the accumulation of iron and lipid peroxide and morphological changes of mitochondria in R28 cells, and SB202190 inhibited these changes. Glutamate induced the levels of p-p38 MAPK/p38 MAPK and SAT1 and decreased the expression levels of ferritin light chain, SLC7A11, and GPX4. SB202190 inhibited the expression of iron death-related proteins induced by glutamate. In vivo experiments showed that SB202190 attenuated N-methyl-D-aspartate-induced damage to rat retinal ganglion cells and improved visual function. These results suggest that SB202190 can inhibit ferroptosis and protect retinal ganglion cells by regulating ferritin light chain, SAT1, and SLC7A11/Gpx4 pathways and may represent a potential retina protectant.

Chronic Glaucoma Induced in Rats by a Single Injection of Fibronectin-Loaded PLGA Microspheres: IOP-Dependent and IOP-Independent Neurodegeneration.

To evaluate a new animal model of chronic glaucoma induced using a single injection of fibronectin-loaded biodegradable PLGA microspheres (Ms) to test prolonged therapies. 30 rats received a single injection of fibronectin-PLGA-Ms suspension (MsF) in the right eye, 10 received non-loaded PLGA-Ms suspension (Control), and 17 were non-injected (Healthy). Follow-up was performed (24 weeks), evaluating intraocular pressure (IOP), optical coherence tomography (OCT), histology and electroretinography. The right eyes underwent a progressive increase in IOP, but only induced cohorts reached hypertensive values. The three cohorts presented a progressive decrease in ganglion cell layer (GCL) thickness, corroborating physiological age-related loss of ganglion cells. Injected cohorts (MsF > Control) presented greater final GCL thickness. Histological exams explain this paradox: the MsF cohort showed lower ganglion cell counts but higher astrogliosis and immune response. A sequential trend of functional damage was recorded using scotopic electroretinography (MsF > Control > Healthy). It seems to be a function-structure correlation: in significant astrogliosis, early functional damage can be detected by electroretinography, and structural damage can be detected by histological exams but not by OCT. Males presented higher IOP and retinal and GCL thicknesses and lower electroretinography. A minimally invasive chronic glaucoma model was induced by a single injection of biodegradable Ms.

Ocular pulse amplitude (OPA) in canine ADAMTS10-open-angle glaucoma (ADAMTS10-OAG).

Introduction: The role of ocular rigidity and biomechanics remains incompletely understood in glaucoma, including assessing an individual's sensitivity to intraocular pressure (IOP). In this regard, the clinical assessment of ocular biomechanics represents an important need. The purpose of this study was to determine a possible relationship between the G661R missense mutation in the ADAMTS10 gene and the ocular pulse amplitude (OPA), the difference between diastolic and systolic intraocular pressure (IOP), in a well-established canine model of open-angle glaucoma (OAG). Methods: Animals studied included 39 ADAMTS10-mutant dogs with different stages of OAG and 14 unaffected control male and female dogs between 6months and 12years (median: 3.2years). Dogs were sedated intravenously with butorphanol tartrate and midazolam HCl, and their IOPs were measured with the Icare® Tonovet rebound tonometer. The Reichert Model 30™ Pneumotonometer was used to measure OPA. Central corneal thickness (CCT) was measured via Accutome® PachPen, and A-scan biometry was assessed with DGH Technology Scanmate. All outcome measures of left and right eyes were averaged for each dog. Data analysis was conducted with ANOVA, ANCOVA, and regression models. Results: ADAMTS10-OAG-affected dogs displayed a greater IOP of 23.0 ± 7.0mmHg (mean ± SD) compared to 15.3 ± 3.6mmHg in normal dogs (p < 0.0001). Mutant dogs had a significantly lower OPA of 4.1 ± 2.0mmHg compared to 6.5 ± 2.8mmHg of normal dogs (p < 0.01). There was no significant age effect, but OPA was correlated with IOP in ADAMTS10-mutant dogs. Conclusion: The lower OPA in ADAMTS10-mutant dogs corresponds to the previously documented weaker and biochemically distinct posterior sclera, but a direct relationship remains to be confirmed. The OPA may be a valuable clinical tool to assess ocular stiffness and an individual's susceptibility to IOP elevation.

Prediction Models for Glaucoma in a Multicenter Electronic Health Records Consortium: The Sight Outcomes Research Collaborative

ObjectiveAdvances in artificial intelligence have enabled the development of predictive models for glaucoma. However, most work is single-center and uncertainty exists regarding the generalizability of such models. The purpose of this study was to build and evaluate machine learning (ML) approaches to predict glaucoma progression requiring surgery using data from a large multicenter consortium of electronic health records (EHR). DesignCohort study. Participants36,548 patients with glaucoma, as identified by ICD codes from six academic eye centers participating in the Sight OUtcomes Research Collaborative (SOURCE). MethodsWe developed machine learning models to predict whether glaucoma patients would progress to glaucoma surgery in the coming year (identified by CPT codes) using the following modeling approaches: 1) penalized logistic regression (lasso, ridge, and elastic net); 2) tree-based models (random forest, gradient boosted machines, XGBoost), and 3) deep learning models. Model input features included demographics, diagnosis codes, medications, and clinical information (intraocular pressure, visual acuity, refractive status, and central corneal thickness) available from structured EHR data. One site was reserved as an “external site” test set (N=1550); of the patients from the remaining sites, 10% each were randomly selected to be in development and test sets, with the remaining 27999 reserved for model training. Main Outcome and MeasuresEvaluation metrics included area under the receiver operating characteristic curve (AUROC) on the test set and the external site. Results6019 (16.5%) of 36,548 patients underwent glaucoma surgery. Overall, the AUROC ranged from 0.735-0.771 on the random test set and from 0.706-0.754 on the external test site, with the XGBoost and random forest model performing best, respectively. There was greatest performance decrease from the random test set to the external test site for the penalized regression models. ConclusionsML models developed using structured EHR data can reasonably predict whether glaucoma patients will need surgery, with reasonable generalizability to an external site. Additional research is needed to investigate the impact of protected class characteristics such as race or gender on model performance and fairness.

The Effects of ROCK Inhibitor on Prevention of Dexamethasone-Induced Glaucoma Phenotype in Human Trabecular Meshwork Cells.

This study investigated the effects of dexamethasone (Dex) on human trabecular meshwork (TM) cells, a model of glucocorticoid-induced glaucoma, and evaluated the impact of ripasudil (Rip) as a co-delivery or sequential dosing strategy. In vitro experiments were conducted to assess the effects of Dex and Rip on TM cells. Confocal microscopy was used to evaluate the impact of Dex and Rip on F-actin staining signals. Contractility of the TM cells upon Dex and Rip treatment mimicking co-delivery and sequential delivery was quantified using collagen gel contraction assay. Transepithelial electrical resistance (TEER) values and fluorescein isothiocyanate (FITC)-dextran permeability were also measured to assess the impact of Dex and Rip on TM cells. Dex and Rip did not exhibit cytotoxicity at the maximum tested concentration (20 µM). Dex-treated TM cells exhibited higher F-actin staining signals compared to controls, which were reduced when co-treated with Rip. Rip inhibited Dex-induced collagen gel contraction activity in both co-delivery and sequential treatments. Dex resulted in increased TEER values as the dose increased, whereas TEER values were maintained when co-treated with Rip. Co-delivery of Rip has the potential to prevent glaucoma symptoms when patients are treated with Dex. This study highlights the importance of identifying strategies to reduce the side effects of prolonged use of glucocorticoids, such as Dex, in the treatment of various diseases. This study demonstrates the potential of co-delivering ripasudil with dexamethasone to mitigate glucocorticoid-induced ocular hypertension and a secondary glaucoma that resembles primary open-angle glaucoma, providing insights for the development of novel preventive strategies in clinical care.

Intraocular pressure-lowering and retina-protective effects of exosome-rich conditioned media from human amniotic membrane stem cells in a rat model of glaucoma

Intraocular pressure-lowering and retina-protective effects of exosome-rich conditioned media from human amniotic membrane stem cells in a rat model of glaucoma

Sustained Vision Recovery by OSK Gene Therapy in a Mouse Model of Glaucoma.

Glaucoma, a chronic neurodegenerative disease, is a leading cause of age-related blindness worldwide and characterized by the progressive loss of retinal ganglion cells (RGCs) and their axons. Previously, we developed a novel epigenetic rejuvenation therapy, based on the expression of the three transcription factors Oct4, Sox2, and Klf4 (OSK), which safely rejuvenates RGCs without altering cell identity in glaucomatous and old mice after 1 month of treatment. In the current year-long study, mice with continuous or cyclic OSK expression induced after glaucoma-induced vision damage had occurred were tracked for efficacy, duration, and safety. Surprisingly, only 2 months of OSK fully restored impaired vision, with a restoration of vision for 11 months with prolonged expression. In RGCs, transcription from the doxycycline (DOX)-inducible Tet-On AAV system, returned to baseline 4 weeks after DOX withdrawal. Significant vision improvements remained for 1 month post switching off OSK, after which the vision benefit gradually diminished but remained better than baseline. Notably, no adverse effects on retinal structure or body weight were observed in glaucomatous mice with OSK continuously expressed for 21 months providing compelling evidence of efficacy and safety. This work highlights the tremendous therapeutic potential of rejuvenating gene therapies using OSK, not only for glaucoma but also for other ocular and systemic injuries and age-related diseases.

An effective pharmacological hydrogel induces optic nerve repair and improves visual function.

Irreversible eye lesions, such as glaucoma and traumatic optic neuropathy, can cause blindness; however, no effective treatments exist. The optic nerve, in particular, lacks the capacity to spontaneously regenerate, requiring the development of an effective approach for optic nerve repair, which has proven challenging. Here, we demonstrate that a combination of the small molecules 3BDO and trichostatin A (TSA)-which regulate mTOR and HDAC, respectively-packaged in thermosensitive hydrogel for 4-week-sustained release after intravitreal injection, effectively induced optic nerve regeneration in a mouse model of optic nerve crush injury. Moreover, this combination of 3BDO and TSA also protected axon projections and improved visual responses in an old mouse model (11 months old) of glaucoma. Taken together, our data provide a new, local small molecule-based treatment for the effective induction of optic nerve repair, which may represent a foundation for the development of pharmacological methods to treat irreversible eye diseases.

Influence of sex on chronic steroid-induced glaucoma: 24-Weeks follow-up study in rats

The objective was to evaluate ocular changes based on sex in steroid-induced glaucoma models in rats comparing healthy controls, over 24 weeks follow-up. Eighty-nine Long–Evans rats (38 males and 51 females) with steroid-induced glaucoma were analysed. Two steroid-induced glaucoma models were generated by injecting poly-co-lactic-glycolic acid microspheres loaded with dexamethasone (MMDEX model) and dexamethasone-fibronectin (MMDEXAFIBRO model) into the ocular anterior chamber. Intraocular pressure was measured by rebound tonometer Tonolab®. Neuroretinal function was analysed using dark- and light-adapted electroretinography (Roland consult® RETIanimal ERG), and structure was analysed using optical coherence tomography (OCT Spectralis, Heidelberg® Engineering) using Retina Posterior Pole, Retinal Nerve Fibre Layer and Ganglion Cell Layer protocols over 24 weeks. Males showed statistically (p < 0.05) higher intraocular pressure measurements. In both sexes and models neuroretinal thickness tended to decrease over time. In the MMDEX model, males showed higher IOP values and greatest percentage thickness loss in the Ganglion Cell Layer (p = 0.015). Females receiving MMDEXAFIBRO experienced large fluctuations in thickness, a higher percentage loss (on average) in Retina Posterior Pole (p = 0.035), Retinal Nerve Fibre Layer and Ganglion Cell Layer than aged-matched males, and the highest thickness loss rate by mmHg. Although no difference was found by sex in dark- and light-adapted electroretinography, increased amplitude in photopic negative response was found in MMDEX males and MMDEXAFIBRO females at 12 weeks. Although both glaucoma models used dexamethasone, different intraocular pressure and neuroretinal changes were observed depending on sex and other influential cofactors (fibronectin). Both sex and the induced glaucoma model influenced neuroretinal degeneration.

Nicotinamide Prevents Retinal Vascular Dropout in a Rat Model of Ocular Hypertension and Supports Ocular Blood Supply in Glaucoma Patients.

To investigate whether nicotinamide (NAM) modulates retinal vasculature in glaucoma. This was a prospective controlled clinical trial investigating animal and human histopathology. Participants included normotensive and ocular hypertensive rats, postmortem human ocular tissue, glaucoma patients (n = 90), and healthy controls (n = 30). The study utilized histopathology, computer-assisted retinal vasculature analysis, optical coherence tomography angiography (OCTA), and NAM treatment. The main outcome measures included retinal vascular parameters in rats as assessed by AngioTool; retinal vasculature integrity in rats and humans as assessed by histopathology, antibody-staining, and ImageJ-based measurements; and retinal perfusion density (PD) and flux index in humans as assessed by OCTA. A number of vessel parameters were altered in ocular hypertension/glaucoma compared to healthy controls. NAM treatment improved the retinal vasculature in ocular hypertensive rats, with an increase in mean vessel area, percentage area covered by vessels, total vessel length, total junctions, and junction density as assessed by AngioTool (all P < 0.05); vessel wall integrity as assessed by VE-cadherin antibody staining was also improved (P < 0.01). In humans, as assessed by OCTA, increases in PD in the optic nerve head and macula complete image (0.7%, P = 0.04 and 1.0%, P = 0.002, respectively) in healthy controls, and an increase in the temporal quadrant of the macula (0.7%, P = 0.02) in glaucoma patients was seen after NAM treatment. NAM can prevent retinal vascular damage in an animal model of glaucoma. After NAM treatment, glaucoma patients and healthy controls demonstrated a small increase in retinal vessel parameters as assessed by OCTA.

Evaluation of degeneration retinal ganglion cell loss in acute glaucoma model rats using syringe pump technique

Link of Video Abstract: https://youtu.be/vaGQXY-i4KE Introduction: Glaucoma is a neurodegenerative disorder marked by the gradual decline in function and degeneration of the retinal ganglion cells (RGCs) and their axons. The elevated intraocular pressure (IOP) is a predominant contributing factor to its onset. Employing laboratory animals to model glaucoma is a well-established strategy that serves the dual purpose of identifying disease mechanisms and developing novel neuroprotective approaches. The aim of this study was to develop a preclinical acute model of glaucoma based on controllable intraocular pressure with a syringe pump in rat Rattus norvegicus. Methods: This research was an animal-experimental study in animal model adult male Wistar rat (Rattus norvegicus), taken in May - October 2023 in an integrated laboratory Faculty of Veterinary Medicine Universitas Syiah Kuala. Total samples used in this research were 10 rats, divided into two categories which are control group (A) and treatment group (B) were given a pressure of 250 mmHg pressure in the right eye for 60 minutes. Apoptosis and degeneration of retinal ganglion cells after 8 weeks of elevated intraocular a pressure of 250 mmHg in the right eye for 60 minutes were observed by the HE staining. Result: A significant difference in IOP was noted between control group rat and treatment group rat. All rats that received treatment experienced an increase in IOP (100%). The RGC density decreased significantly in the treatment group rat (mean: 11.72 cell/field of view or lower 46.88%) compared with the control group (p =0.005). Conclusion: A pressure of 250 mmHg for 60 minutes has been proven to cause degeneration of the RGCs up to nearly 50% within a week. We tried a technique to induce increased IOP in rats as a model of acute glaucoma. Syringe pump technique can effectively induce acute ocular hypertension in rats, which causes progressive loss of retinal ganglion cells.

Myo/Nog Cells Increase in Response to Elevated Intraocular Pressure and Mitigate Ganglion Cell Death in a Mouse Model of Glaucoma

Glaucoma is one of the leading causes of blindness worldwide. Decreased aqueous humor drainage causes an increase in intraocular pressure (IOP), which in turn damages the ganglion cells of the retina and optic nerve. A mouse model of glaucoma was used to examine the behavior of Myo/Nog (M/N) cells, which were previously shown to respond to cataract surgery and retinopathy induced by hypoxia, light damage, and intravitreal injection of human retinal pigment epithelial cells. M/N cells express the skeletal-muscle-specific transcription factor MyoD, the bone morphogenetic protein inhibitor Noggin, and brain-specific angiogenesis inhibitor 1 (BAI1). Glaucoma was induced by injecting microbeads into the anterior chamber (AC) of the right eye to obstruct the flow of aqueous humor into the trabecular meshwork. IOP was elevated within three days of addition of microbeads. Loss of retinal ganglion cells (RGCs) and thinning of the ganglion cell layer–nerve fiber layer (GCL-NFL) was observed in tissue sections by day 32. The injection of microbeads resulted in an increase in BAI1-positive (+) M/N cells in the trabecular meshwork, ciliary body, canal of Schlemm, cornea, and ganglion cell layer (GCL). M/N cells ingested microbeads. The effect of further increasing the population of M/N cells on IOP and RGC loss was determined by injecting BAI1+ cells isolated from the brain into the AC of both eyes. Exogenous M/N cells prelabeled with CellTracker™ Red were found in the same tissues as the endogenous population of M/N cells in eyes with and without elevated IOP. The addition of M/N cells did not significantly reduce IOP in bead-injected eyes. However, there were significantly more RGCs and the NFL was thicker in glaucomatous eyes with M/N cell supplementation than eyes injected with phosphate-buffered saline. The numbers of RGCs and NFL thickness were similar in glaucomatous and non-glaucomatous eyes after adding M/N cells. These results demonstrate that endogenous M/N cells respond to elevated IOP in the anterior and posterior segments in response to induction of glaucoma. M/N cells’ mitigation of RGC loss may reflect a neuroprotective effect within the retina, as opposed to a significant drop in IOP.

The Inflammasome-Dependent Dysfunction and Death of Retinal Ganglion Cells after Repetitive Intraocular Pressure Spikes.

The dysfunction and selective loss of retinal ganglion cells (RGCs) is a known cause of vision loss in glaucoma and other neuropathies, where ocular hypertension (OHT) is the major risk factor. We investigated the impact of transient non-ischemic OHT spikes (spOHT) on RGC function and viability in vivo to identify cellular pathways linking low-grade repetitive mechanical stress to RGC pathology. We found that repetitive spOHT had an unexpectedly high impact on intraocular homeostasis and RGC viability, while exposure to steady OHT (stOHT) of a similar intensity and duration failed to induce pathology. The repetitive spOHT induced the rapid activation of the inflammasome, marked by the upregulation of NLRP1, NLRP3, AIM2, caspases -1, -3/7, -8, and Gasdermin D (GSDMD), and the release of interleukin-1β (IL-1β) and other cytokines into the vitreous. Similar effects were also detected after 5 weeks of exposure to chronic OHT in an induced glaucoma model. The onset of these immune responses in both spOHT and glaucoma models preceded a 50% deficit in pattern electroretinogram (PERG) amplitude and a significant loss of RGCs 7 days post-injury. The inactivation of inflammasome complexes in Nlrp1-/-, Casp1-/-, and GsdmD-/- knockout animals significantly suppressed the spOHT-induced inflammatory response and protected RGCs. Our results demonstrate that mechanical stress produced by acute repetitive spOHT or chronic OHT is mechanistically linked to inflammasome activation, which leads to RGC dysfunction and death.

ScAAV2-Mediated Expression of Thioredoxin 2 and C3 Transferase Prevents Retinal Ganglion Cell Death and Lowers Intraocular Pressure in a Mouse Model of Glaucoma.

Elevated intraocular pressure (IOP) in glaucoma causes retinal ganglion cell (RGC) loss and damage to the optic nerve. Although IOP is controlled pharmacologically, no treatment is available to restore retinal and optic nerve function. In this paper, we aimed to develop a novel gene therapy for glaucoma using an AAV2-based thioredoxin 2 (Trx2)-exoenzyme C3 transferase (C3) fusion protein expression vector (scAAV2-Trx2-C3). We evaluated the therapeutic effects of this vector in vitro and in vivo using dexamethasone (DEX)-induced glaucoma models. We found that scAAV2-Trx2-C3-treated HeLa cells had significantly reduced GTP-bound active RhoA and increased phosphor-cofilin Ser3 protein expression levels. scAAV2-Trx2-C3 was also shown to inhibit oxidative stress, fibronectin expression, and alpha-SMA expression in DEX-treated HeLa cells. NeuN immunostaining and TUNEL assay in mouse retinal tissues was performed to evaluate its neuroprotective effect upon RGCs, whereas changes in mouse IOP were monitored via rebound tonometer. The present study showed that scAAV2-Trx2-C3 can protect RGCs from degeneration and reduce IOP in a DEX-induced mouse model of glaucoma, while immunohistochemistry revealed that the expression of fibronectin and alpha-SMA was decreased after the transduction of scAAV2-Trx2-C3 in murine eye tissues. Our results suggest that AAV2-Trx2-C3 modulates the outflow resistance of the trabecular meshwork, protects retinal and other ocular tissues from oxidative damage, and may lead to the development of a gene therapeutic for glaucoma.

Efficacy of a Spearmint (Mentha spicata L.) Extract as Nutritional Support in a Rat Model of Hypertensive Glaucoma.

Glaucoma is an eye-brain axis disorder characterized by loss of retinal ganglion cells (RGCs). Although the role of intraocular pressure (IOP) elevation in glaucoma has been established, the reduction of oxidative stress and inflammation has emerged as a promising target for neuronal tissue-supporting glaucoma management. Therefore, we evaluated the effect of a proprietary spearmint extract (SPE) on RGC density, activity, and neuronal health markers in a rat model of hypertensive glaucoma. Animals were divided in four groups: untreated healthy control and three glaucomatous groups receiving orally administered vehicle, SPE-low dose, or SPE-high dose for 28 days. Ocular hypertension was induced through intracameral injection of methylcellulose at day 15. At day 29, rats underwent electroretinogram (ERG) recordings, and retinas were analyzed for RGC density and markers of neural trophism, oxidative stress, and inflammation. SPE exerted dose-dependent response benefits on all markers except for IOP elevation. SPE significantly improved RGC-related ERG responses, cell density, neurotrophins, oxidative stress, and inflammation markers. Also, in SPE-high rats, most of the parameters were not statistically different from those of healthy controls. SPE, a plant-based, polyphenolic extract, could be an effective nutritional support for neuronal tissues. These results suggest that SPE not only may be a complementary approach in support to hypotensive treatments for the management of glaucoma but may also serve as nutritional support in other ocular conditions where antioxidant, anti-inflammatory, and neuroprotective mechanism are often disrupted.

MicroRNA-93 promotes the pathogenesis of glaucoma by inhibiting matrix metalloproteinases as well as up-regulating extracellular matrix and Rho/ROCK signaling pathways

ObjectiveTo investigate the effect and potential molecular mechanism of microRNA-93 (miR-93) on retinal ganglion cells (RGCs) apoptosis as well as retinal damage in acute glaucoma mice. MethodsRGCs apoptosis were induced by oxygen-glucose deprivation and reperfusion (OGD/R). The pro-apoptotic effect of miR-93 was evaluated by transfecting miR-93 mimics or miR-93 inhibitor into OGD/R-induced RGCs. The viability and apoptosis of RGCs were determined by MTT assay and flow cytometry. Mouse model of acute glaucoma were successfully induced via high intraocular pressure (IOP), and then these model animals were randomly divided into vehicle group, miR-93 mimics group or miR-93 inhibitor group (n = 10), using healthy mice as normal control. Histopathologic changes of retinal tissue were evaluated by Hematoxylin and Eosin (H&E) staining method. Moreover, cell counts of retinal ganglion cell layer and mean thickness of different layers were also determined. Quantitative real-time PCR (qPCR) and western blotting analysis were used to detect the mRNA and protein expression levels of extracellular matrix (ECM), matrix metalloproteinases (MMPs) and Rho/ROCK signaling pathway. ResultsmiR-93 mimics significantly decreased or promoted the viability and apoptosis of OGD/R-induced RGCs, respectively. In addition, miR-93 mimics significantly exacerbated the degree of retinal tissue damage in mice with acute glaucoma, which was accompanied by a decrease in the number of ganglion cell layer (GCL) cells and the thickness of different tissue layers. Moreover, miR-93 mimics significantly increased IOP in mice with acute glaucoma. Significantly, miR-93 inhibitors significantly reversed the above changes. In addition, results of Western blot analysis showed that miR-93 mimics increased and decreased the expression of ECM-associated and MMP-associated proteins, respectively, by activating the Rho/ROCK signaling pathway. In contrast, miR-93 significantly decreased and increased the expression of ECM-associated and MMP-associated proteins, and suppressed the expression of Rho/ROCK signaling pathway-related proteins. ConclusionmiR-93 can promote the development of glaucoma by activating Rho/ROCK signaling pathway to mediate the accumulation of ECM-related proteins as well as the down-regulation of MMP-related proteins.