Generating ESC-Derived RGCs for Cell Replacement Therapy.

In several ocular diseases, degeneration of retinal neurons can lead to permanent blindness. Transplantation of stem cell (SC)-derived RGCs has been proposed as a potential therapy for RGC loss. Although there are reports of successful cases of SC-derived RGC transplantation, achieving long-distance regeneration and functional connectivity remains a challenge. To address these hurdles, retinal organoids are being used to study the regulatory mechanism of stem cell transplantation. Here we present a modified protocol for differentiating human embryonic stem cells (ESCs) into retinal organoids and transplanting organoid-derived RGCs into the murine eyes.

Effect of brimonidine on visual indices in patients with acute optic neuritis: A single blind randomized clinical trial.

PURPOSE: This study investigates brimonidine's potential effect on visual functions, particularly contrast sensitivity (CS), an indicator of retinal ganglion cell function. METHODS: In this single-blind, randomized clinical trial, 60 patients (aged 23-56) with first-episode acute optic neuritis within seven days of symptom onset were randomly assigned to brimonidine or control groups. The intervention group received brimonidine three times daily for three months, while the control group received synthetic tears with the same dosage and frequency. Primary outcomes were changes in CS, visual acuity (VA), and color vision at one and three months post-treatment. Repeated measures ANOVA was used to assess statistically significant and partial eta squared (η2) values, mean differences, and clinically significance important were reported. RESULTS: All participants completed the study without complications. VA improved significantly in both groups by follow-up end (p < 0.001), with significant improvement from first to third month only in the brimonidine group (p < 0.001). The mean VA difference between groups was not statistically and clinically significant. CS showed statistically significant improvement within both groups (p < 0.001) and between groups (p < 0.001), with a large effect size (partial η2 = 0.28). The mean CS difference between groups (14.5) was clinically considerable. No significant changes in color vision were observed between groups (p = 0.96). CONCLUSION: Brimonidine significantly improved contrast sensitivity compared to placebo and was well-tolerated. Its neuroprotective effects suggest it may be beneficial in treating optic neuritis and preserving retinal ganglion cell function. TRIAL REGISTRATION: Prospectively registered at Iranian Clinical Trial Registration; Registration date 3 December 2022; Registration number: IRCT20221127056631N1.

Axon guidance during mouse central nervous system regeneration is required for specific brain innervation.

Reconstructing functional neuronal circuits is one major challenge of central nervous system repair. Through activation of pro-growth signaling pathways, some neurons achieve long-distance axon regrowth. Yet, functional reconnection has hardly been obtained, as these regenerating axons fail to resume their initial trajectory and reinnervate their proper target. Axon guidance is considered to be active only during development. Here, using the mouse visual system, we show that axon guidance is still active in the adult brain in regenerative conditions. We highlight that regenerating retinal ganglion cell axons avoid one of their primary targets, the suprachiasmatic nucleus (SCN), due to Slit/Robo repulsive signaling. Together with promoting regeneration, silencing Slit/Robo in vivo enables regenerating axons to enter the SCN and form active synapses. The newly formed circuit is associated with neuronal activation and functional recovery. Our results provide evidence that axon guidance mechanisms are required to reconnect regenerating axons to specific brain nuclei.

Retinal waves in adaptive rewiring networks orchestrate convergence and divergence in the visual system.

Spontaneous retinal wave activity shaping the visual system is a complex neurodevelopmental phenomenon. Retinal ganglion cells are the hubs through which activity diverges throughout the visual system. We consider how these divergent hubs emerge, using an adaptively rewiring neural network model. Adaptive rewiring models show in a principled way how brains could achieve their complex topologies. Modular small-world structures with rich-club effects and circuits of convergent-divergent units emerge as networks evolve, driven by their own spontaneous activity. Arbitrary nodes of an initially random model network were designated as retinal ganglion cells. They were intermittently exposed to the retinal waveform, as the network evolved through adaptive rewiring. A significant proportion of these nodes developed into divergent hubs within the characteristic complex network architecture. The proportion depends parametrically on the wave incidence rate. Higher rates increase the likelihood of hub formation, while increasing the potential of ganglion cell death. In addition, direct neighbors of designated ganglion cells differentiate like amacrine cells. The divergence observed in ganglion cells resulted in enhanced convergence downstream, suggesting that retinal waves control the formation of convergence in the lateral geniculate nuclei. We conclude that retinal waves stochastically control the distribution of converging and diverging activity in evolving complex networks.

Retinal waves consist of spontaneous neural activity that propagates across the retina during neural development. We simulate the intermittent spread of retinal waveforms originating from a designated node in an adaptively rewiring neural network model. Adaptive rewiring models simulate, in a highly abstracted manner, how brains may achieve their complex topologies during development. This way, we aim to uncover basic principles of neural maturation in the visual system. Namely, we seek to shed light onto how retinal waves might be responsible for the differentiation of immature neurons into specific cell types (e.g., retinal ganglion cells, amacrine cells) and how these waves shape the connectivity structure in the visual system.

Specific retinal neurons regulate context-dependent defensive responses to visual threat.

While encountering a visual threat, an animal assesses multiple factors to choose an appropriate defensive strategy. For example, when a rodent detects a looming aerial predator, its behavioral response can be influenced by a specific environmental context, such as the availability of a shelter. Indeed, rodents typically escape from a looming stimulus when a shelter is present; otherwise, they typically freeze. Here we report that context-dependent behavioral responses can be initiated at the earliest stage of the visual system by distinct types of retinal ganglion cells (RGCs), the retina's output neurons. Using genetically defined cell ablation in mature mice, we discovered that some RGC types were necessary for either escaping (alpha RGCs) or freezing (intrinsically photosensitive RGCs) in response to a looming stimulus but not for both behaviors; whereas other RGC types were not required for either behavior (direction-selective RGCs preferring vertical motion). Altogether, our results suggest that specific RGC types regulate distinct behavioral responses elicited by the same threatening stimulus depending on contextual signals in the environment. These findings emphasize the unique contribution of early visual pathways to evolutionally conserved behavioral reactions.

Neuronal and glial cell alterations involved in the retinal degeneration of the familial dysautonomia optic neuropathy.

Familial dysautonomia (FD) is a rare genetic neurodevelopmental and neurodegenerative disorder. In addition to the autonomic and peripheral sensory neuropathies that challenge patient survival, one of the most debilitating symptoms affecting patients' quality of life is progressive blindness resulting from the steady loss of retinal ganglion cells (RGCs). Within the FD community, there is a concerted effort to develop treatments to prevent the loss of RGCs. However, the mechanisms underlying the death of RGCs are not well understood. To study the mechanisms underlying RGC death, Pax6-cre;Elp1loxp/loxp male and female mice and postmortem retinal tissue from an FD patient were used to explore the neuronal and non-neuronal cellular pathology associated with the FD optic neuropathy. Neurons, astrocytes, microglia, Müller glia, and endothelial cells were investigated using a combination of histological analyses. We identified a novel disruption of cellular homeostasis and gliosis in the FD retina. Beginning shortly after birth and progressing with age, the FD retina is marked by astrogliosis and perturbations in microglia, which coincide with vascular remodeling. These changes begin before the onset of RGC death, suggesting alterations in the retinal neurovascular unit may contribute to and exacerbate RGC death. We reveal for the first time that the FD retina pathology includes reactive gliosis, increased microglial recruitment to the ganglion cell layer (GCL), disruptions in the deep and superficial vascular plexuses, and alterations in signaling pathways. These studies implicate the neurovascular unit as a disease-modifying target for therapeutic interventions in FD.

Thorny and Tufted Retinal Ganglion Cells Express the Transcription Factor Forkhead Proteins Foxp1 and Foxp2 in Marmoset (Callithrix jacchus).

The transcription factor forkhead/winged-helix domain proteins Foxp1 and Foxp2 have previously been studied in mouse retina, where they are expressed in retinal ganglion cells named F-mini and F-midi. Here we show that both transcription factors are expressed by small subpopulations (on average less than 10%) of retinal ganglion cells in the retina of the marmoset monkey (Callithrix jacchus). The morphology of Foxp1- and Foxp2-expressing cells was revealed by intracellular DiI injections of immunofluorescent cells. Foxp1- and Foxp2-expressing cells comprised multiple types of wide-field ganglion cells, including broad thorny cells, narrow thorny cells, and tufted cells. The large majority of Foxp2-expressing cells were identified as tufted cells. Tufted cells stratify broadly in the middle of the inner plexiform layer. They resemble broad thorny cells but their proximal dendrites are bare of branches and the distal dendrites branch frequently forming dense dendritic tufts. Double labeling with calretinin, a previously established marker for broad thorny and narrow thorny cells, showed that only a small proportion of ganglion cells co-expressed calretinin and Foxp1 or Foxp2 supporting the idea that the two markers are differentially expressed in retinal ganglion cells of marmoset retina.

Impact of Glaucomatous Ganglion Cell Damage on Central Visual Function.

Glaucoma, a leading cause of irreversible blindness, is characterized by the progressive loss of retinal ganglion cells (RGCs) and subsequent visual field defects. RGCs, as the final output neurons of the retina, perform key computations underpinning human pattern vision, such as contrast coding. Conventionally, glaucoma has been associated with peripheral vision loss, and thus, relatively little attention has been paid to deficits in central vision. However, recent advancements in retinal imaging techniques have significantly bolstered research into glaucomatous damage of the macula, revealing that it is prevalent even in the early stages of glaucoma. Thus, it is an opportune time to explore how glaucomatous damage undermines the perceptual processes associated with central visual function. This review showcases recent studies addressing central dysfunction in the early and moderate stages of glaucoma. It further emphasizes the need to characterize glaucomatous damage in both central and peripheral vision, as they jointly affect an individual's everyday activities.

Retinal ganglion cell vulnerability to pathogenic tau in Alzheimer's disease.

Accumulation of pathological tau isoforms, especially hyperphosphorylated tau at serine 396 (pS396-tau) and tau oligomers, has been demonstrated in the retinas of patients with mild cognitive impairment (MCI) and Alzheimer's disease (AD). Previous studies have noted a decrease in retinal ganglion cells (RGCs) in AD patients, but the presence and impact of pathological tau isoforms in RGCs and RGC integrity, particularly in early AD stages, have not been explored. To investigate this, we examined retinal superior temporal cross-sections from 25 patients with MCI (due to AD) or AD dementia and 16 cognitively normal (CN) controls, matched for age and gender. We utilized the RGC marker ribonucleic acid binding protein with multiple splicing (RBPMS) and Nissl staining to assess neuronal density in the ganglion cell layer (GCL). Our study found that hypertrophic RGCs containing pS396-tau and T22-positive tau oligomers were more frequently observed in MCI and AD patients compared to CN subjects. Quantitative analyses indicated a decline in RGC integrity, with 46-55% and 55-56% reductions of RBPMS+ RGCs (P<0.01) and Nissl+ GCL neurons (P<0.01-0.001), respectively, in MCI and AD patients. This decrease in RGC count was accompanied by increases in necroptotic-like morphology and the cleaved caspase-3 apoptotic marker in RGCs of AD patients. Furthermore, there was a 2.1 to 3.1-fold increase (P<0.05-0.0001) in pS396-tau-laden RGCs in MCI and AD patients, with a greater abundance observed in individuals with higher Braak stages (V-VI), more severe clinical dementia ratings (CDR=3), and lower mini-mental state examination (MMSE) scores. Strong correlations were noted between the decline in RGCs and the total amount of retinal pS396-tau and pS396-tau+ RGCs, with pS396-tau+ RGC counts correlating significantly with brain neurofibrillary tangle scores (r= 0.71, P= 0.0001), Braak stage (r= 0.65, P= 0.0009), and MMSE scores (r= -0.76, P= 0.0004). These findings suggest that retinal tauopathy, characterized by pS396-tau and oligomeric tau in hypertrophic RGCs, is associated with and may contribute to RGC degeneration in AD. Future research should validate these findings in larger cohorts and explore noninvasive retinal imaging techniques that target tau pathology in RGCs to improve AD detection and monitor disease progression.

A p75 neurotrophin receptor-sparing nerve growth factor protects retinal ganglion cells from neurodegeneration by targeting microglia.

BACKGROUND AND PURPOSE: Retinal ganglion cells (RGCs) are the output stage of retinal information processing, via their axons forming the optic nerve (ON). ON damage leads to axonal degeneration and death of RGCs, and results in vision impairment. Nerve growth factor (NGF) signalling is crucial for RGC operations and visual functions. Here, we investigate a new neuroprotective mechanism of a novel therapeutic candidate, a p75-less, TrkA-biased NGF agonist (hNGFp) in rat RGC degeneration, in comparison with wild type human NGF (hNGFwt). EXPERIMENTAL APPROACH: Both neonate and adult rats, whether subjected or not to ON lesion, were treated with intravitreal injections or eye drops containing either hNGFp or hNGFwt. Different doses of the drugs were administered at days 1, 4 or 7 after injury for a maximum of 10 days, when immunofluorescence, electrophysiology, cellular morphology, cytokine array and behaviour studies were carried out. Pharmacokinetic evaluation was performed on rabbits treated with hNGFp ocular drops. RESULTS: hNGFp exerted a potent RGC neuroprotection by acting on microglia cells, and outperformed hNGFwt in rescuing RGC degeneration and reducing inflammatory molecules. Delayed use of hNGFp after ON lesion resulted in better outcomes compared with treatment with hNGFwt. Moreover, hNGFp-based ocular drops were less algogenic than hNGFwt. Pharmacokinetic measurements revealed that biologically relevant quantities of hNGFp were found in the rabbit retina. CONCLUSIONS AND IMPLICATIONS: Our data point to microglia as a new cell target through which NGF-induced TrkA signalling exerts neuroprotection of the RGC, emphasizing hNGFp as a powerful treatment to tackle retinal degeneration.

Diminished light sensitivities of ON alpha retinal ganglion cells observed in a mouse model of hyperglycemia.

This study aimed to investigate potential functional changes in retinal ganglion cells (RGCs) in a mouse model of hyperglycemia and explore possible therapeutic approaches. Hyperglycemia resembling type 1 diabetes mellitus (DM) was induced in C57BL/6 mice through intraperitoneal injection of streptozotocin (STZ). Blood glucose levels were confirmed to be elevated after 1 week and 4 weeks of injection. Mice with blood glucose levels above 350 mg/mL after 4 weeks of one-dose STZ injection were considered hyperglycemic. The light sensitivity of ON alpha (α) retinal ganglion cells (RGCs), not OFF αRGCs, was reduced in the hyperglycemic mouse model. The number of apoptotic cells, RGCs, and amacrine cells (ACs) remained unaffected at this stage. Similarly, the eletroretinogram (ERG) and optokinetic test results showed no significant differences. The application of picrotoxin (PTX) to block GABA receptors could increase the light sensitivity of ON αRGCs by 1 log unit in hyperglycemic mice. The results show that ON αRGCs may be more susceptible to microenvironmental changes caused by hyperglycemia than OFF αRGCs. This decline in light sensitivity may occur before cell apoptosis during the early stages of the hyperglycemic mouse model but has the potential to be reversed.

Rotenone-Induced Optic Nerve Damage and Retinal Ganglion Cell Loss in Rats.

Rotenone is a mitochondrial complex I inhibitor that causes retinal degeneration. A study of a rat model of rotenone-induced retinal degeneration suggested that this model is caused by indirect postsynaptic N-methyl-D-aspartate (NMDA) stimulation triggered by oxidative stress-mediated presynaptic intracellular calcium signaling. To elucidate the mechanisms by which rotenone causes axonal degeneration, we investigated morphological changes in optic nerves and the change in retinal ganglion cell (RGC) number in rats. Optic nerves and retinas were collected 3 and 7 days after the intravitreal injection of rotenone. The cross-sections of the optic nerves were subjected to a morphological analysis with axon quantification. The axons and somas of RGCs were analyzed immunohistochemically in retinal flatmounts. In the optic nerve, rotenone induced axonal swelling and degeneration with the incidence of reactive gliosis. Rotenone also significantly reduced axon numbers in the optic nerve. Furthermore, rotenone caused axonal thinning, fragmentation, and beading in RGCs on flatmounts and decreased the number of RGC soma. In conclusion, the intravitreal injection of rotenone in rats induced morphological abnormities with a reduced number of optic nerve axons and RGC axons when the RGC somas were degenerated. These findings help elucidate the pathogenesis of optic neuropathy induced by mitochondrial dysfunction.

FK962 protects retinal ganglion cell under hypoxia/reoxygenation: Possible involvement of glial cell line-derived neurotrophic factor signaling pathway.

Loss of retinal ganglion cells (RGCs) is the cause of visual impairment and blindness in glaucoma. Previously, our studies showed that FK962 (N-[1-acetylpiperidin-4-yl]-4-fluorobenzamide) promoted neurite elongation in rat RGCs and trigeminal ganglion (TG) cells. In TG cells, glial cell line-derived neurotrophic factor (GDNF) is known to be involved in the mechanism. The purpose of the present study is to investigate whether, 1) FK962 shows an RGC-protective effect under hypoxia/reoxygenation (H/R) and 2) GDNF is involved in the neuroprotective mechanism of FK962. Rat primary retinal cells were cultured under 24-h hypoxia/24-h reoxygenation conditions, with or without FK962, recombinant GDNF, GDNF antibody and RET receptor tyrosine kinase inhibitor, GSK3179106. Cells were co-immunostained with RBPMS and Neurofilament 200 as a RGC marker, and the number of survived RGCs was counted. Results showed H/R treatment decreased the number of survived RGCs. FK962 promoted RGC survival under H/R by a bell-shaped dose response, with the highest RGC-protective effect of 10-8 M. The protective effect was the same level with 10-12 M exogenous GDNF. Addition of GDNF antibody or GSK3179106 counteracted the neuroprotective effect of FK962. From these results, it is suggested that FK962 ameliorates RGC death under H/R, possibly via a GDNF signaling pathway.

DJ-1 regulates mitochondrial function and promotes retinal ganglion cell survival under high glucose-induced oxidative stress.

Purpose: This study aimed to investigate the antioxidative and neuroprotective effects of DJ-1 in mitigating retinal ganglion cell (RGC) damage induced by high glucose (HG). Methods: A diabetic mouse model and an HG-induced R28 cell model were employed for loss- and gain-of-function experiments. The expression levels of apoptosis and oxidative stress-related factors, including Bax, Bcl-2, caspase3, Catalase, MnSOD, GCLC, Cyto c, and GPx-1/2, were assessed in both animal and cell models using Western blotting. Retinal structure and function were evaluated through HE staining, electroretinogram, and RGC counting. Mitochondrial function and apoptosis were determined using JC-1 and TUNEL staining, and reactive oxygen species (ROS) measurement. Results: In the mouse model, hyperglycemia resulted in reduced retinal DJ-1 expression, retinal structural and functional damage, disrupted redox protein profiles, and mitochondrial dysfunction. Elevated glucose levels induced mitochondrial impairment, ROS generation, abnormal protein expression, and apoptosis in R28 cells. Augmenting DJ-1 expression demonstrated a restoration of mitochondrial homeostasis and alleviated diabetes-induced morphological and functional impairments both in vivo and in vitro. Conclusion: This study provides novel insights into the regulatory role of DJ-1 in mitochondrial dynamics, suggesting a potential avenue for enhancing RGC survival in diabetic retinopathy.

Inhibition of angiogenesis by the secretome from iPSC-derived retinal ganglion cells with Leber's hereditary optic neuropathy-like phenotypes.

The blood supply in the retina ensures photoreceptor function and maintains regular vision. Leber's hereditary optic neuropathy (LHON), caused by the mitochondrial DNA mutations that deteriorate complex I activity, is characterized by progressive vision loss. Although some reports indicated retinal vasculature abnormalities as one of the comorbidities in LHON, the paracrine influence of LHON-affected retinal ganglion cells (RGCs) on vascular endothelial cell physiology remains unclear. To address this, we established an in vitro model of mitochondrial complex I deficiency using induced pluripotent stem cell-derived RGCs (iPSC-RGCs) treated with a mitochondrial complex I inhibitor rotenone (Rot) to recapitulate LHON pathologies. The secretomes from Rot-treated iPSC-RGCs (Rot-iPSC-RGCs) were collected, and their treatment effect on human umbilical vein endothelial cells (HUVECs) was studied. Rot induced LHON-like characteristics in iPSC-RGCs, including decreased mitochondrial complex I activity and membrane potential, and increased mitochondrial reactive oxygen species (ROS) and apoptosis, leading to mitochondrial dysfunction. When HUVECs were exposed to conditioned media (CM) from Rot-iPSC-RGCs, the angiogenesis of HUVECs was suppressed compared to those treated with CM from control iPSC-RGCs (Ctrl-iPSC-RGCs). Angiogenesis-related proteins were altered in the secretomes from Rot-iPSC-RGC-derived CM, particularly angiopoietin, MMP-9, uPA, collagen XVIII, and VEGF were reduced. Notably, GeneMANIA analysis indicated that VEGFA emerged as the pivotal angiogenesis-related protein among the identified proteins secreted by health iPSC-RGCs but reduced in the secretomes from Rot-iPSC-RGCs. Quantitative real-time PCR and western blots confirmed the reduction of VEGFA at both transcription and translation levels, respectively. Our study reveals that Rot-iPSC-RGCs establish a microenvironment to diminish the angiogenic potential of vascular cells nearby, shedding light on the paracrine regulation of LHON-affected RGCs on retinal vasculature.

Retinal Input Is Required for the Maintenance of Neuronal Laminae in the Ventrolateral Geniculate Nucleus.

Retinal ganglion cell (RGC) axons provide direct input into several brain regions, including the dorsal lateral geniculate nucleus (dLGN), which is important for image-forming vision, and the ventrolateral geniculate nucleus (vLGN), which is associated with nonimage-forming vision. Through both activity- and morphogen-dependent mechanisms, retinal inputs play important roles in the development of dLGN, including the refinement of retinal projections, morphological development of thalamocortical relay cells (TRCs), timing of corticogeniculate innervation, and recruitment and distribution of inhibitory interneurons. In contrast, little is known about the role of retinal inputs in the development of vLGN. Grossly, vLGN is divided into two domains, the retinorecipient external vLGN (vLGNe) and nonretinorecipient internal vLGN (vLGNi). Studies previously found that vLGNe consists of transcriptionally distinct GABAergic subtypes distributed into at least four adjacent laminae. At present, it remains unclear whether retinal inputs influence the development of these cell-type-specific neuronal laminae in vLGNe. Here, we elucidated the developmental timeline for these laminae in the mouse vLGNe, and results indicate that these laminae are specified at or before birth. We observed that mutant mice without retinal inputs have a normal laminar distribution of GABAergic cells at birth; however, after the first week of postnatal development, these mutants exhibited a dramatic disruption in the laminar organization of inhibitory neurons and clear boundaries between vLGNe and vLGNi. Overall, our results show that while the formation of cell-type-specific layers in mouse vLGNe does not depend on RGC inputs, retinal signals are critical for their maintenance.

Caveolin-1 protects retinal ganglion cells in glaucoma by reducing TLR4 and activating the Akt/PTEN signaling pathway.

Glaucoma is a degenerative disease characterized by retinal ganglion cell (RGC) death and visual impairment caused by elevated intraocular pressure (IOP). Elevated IOP can activate microglia, which participate in ganglion cell injury. Based on the study of caveolin-1 (Cav-1) in glaucoma, we aimed to explore the effect and mechanism of Cav-1 on RGC apoptosis in mice with acute ocular hypertension (AOH). AOH mice were established, and Cav-1 was intravitreally injected. Retinal microglia and RGCs were isolated from neonatal mice. TUNEL staining, hematoxylin-eosin staining, immunohistochemistry, flow cytometry, PCR and western blotting were used to observe the effect of Cav-1 on RGCs and mouse retinas. The thickness of the whole retina and the inner retinal sublayer decreased significantly, retinal cell apoptosis increased after AOH injury, and Cav-1 treatment reversed the effect of AOH injury. In addition, Cav-1 treatment promoted the conversion of proinflammatory M1 microglia to anti-inflammatory M2 microglia. Microglia and RGCs were isolated from neonatal mice. Cav-1 protects RGCs from OGD/R-induced injury by changing the polarization status of retinal microglia in vitro. Further studies revealed that Cav-1 activated the Akt/PTEN signaling pathway and inhibited TLR4. Our study provides evidence that Cav-1 may be a promising therapeutic target for glaucoma.

Increased Pan-Type, A1-Type, and A2-Type Astrocyte Activation and Upstream Inflammatory Markers Are Induced by the P2X7 Receptor.

This study asked whether the P2X7 receptor was necessary and sufficient to trigger astrocyte polarization into neuroinflammatory activation states. Intravitreal injection of agonist BzATP increased gene expression of pan-astrocyte activation markers Gfap, Steap4, and Vim and A1-type astrocyte activation markers C3, Serping1, and H2T23, but also the Cd14 and Ptx3 genes usually associated with the A2-type astrocyte activation state and Tnfa, IL1a, and C1qa, assumed to be upstream of astrocyte activation in microglia. Correlation analysis of gene expression suggested the P2X7 receptor induced a mixed A1/A2-astrocyte activation state, although A1-state genes like C3 increased the most. A similar pattern of mixed glial activation genes occurred one day after intraocular pressure (IOP) was elevated in wild-type mice, but not in P2X7-/- mice, suggesting the P2X7 receptor is necessary for the glial activation that accompanies IOP elevation. In summary, this study suggests stimulation of the P2X7R is necessary and sufficient to trigger the astrocyte activation in the retina following IOP elevation, with a rise in markers for pan-, A1-, and A2-type astrocyte activation. The P2X7 receptor is expressed on microglia, optic nerve head astrocytes, and retinal ganglion cells (RGCs) in the retina, and can be stimulated by the mechanosensitive release of ATP that accompanies IOP elevation. Whether the P2X7 receptor connects this mechanosensitive ATP release to microglial and astrocyte polarization in glaucoma remains to be determined.

Mitochondria in Retinal Ganglion Cells: Unraveling the Metabolic Nexus and Oxidative Stress.

This review explored the role of mitochondria in retinal ganglion cells (RGCs), which are essential for visual processing. Mitochondrial dysfunction is a key factor in the pathogenesis of various vision-related disorders, including glaucoma, hereditary optic neuropathy, and age-related macular degeneration. This review highlighted the critical role of mitochondria in RGCs, which provide metabolic support, regulate cellular health, and respond to cellular stress while also producing reactive oxygen species (ROS) that can damage cellular components. Maintaining mitochondrial function is essential for meeting RGCs' high metabolic demands and ensuring redox homeostasis, which is crucial for their proper function and visual health. Oxidative stress, exacerbated by factors like elevated intraocular pressure and environmental factors, contributes to diseases such as glaucoma and age-related vision loss by triggering cellular damage pathways. Strategies targeting mitochondrial function or bolstering antioxidant defenses include mitochondrial-based therapies, gene therapies, and mitochondrial transplantation. These advances can offer potential strategies for addressing mitochondrial dysfunction in the retina, with implications that extend beyond ocular diseases.

Relationship Between Changes in the Expression Levels of miR-134 and E2F6 in Mediating Control of Apoptosis in NMDA-Induced Glaucomatous Mice.

OBJECTIVE: This investigation was to determine the relationship between changes in the expression levels of miR-134 and the E2F transcription factor 6 (E2F6) in mediating control of apoptosis in N-methyl-D-aspartate (NMDA)-induced glaucomatous mice. METHODS: Morphological and structural changes were quantitatively analyzed along with apoptosis in the retinal ganglion cell (RGC) layer, internal plexiform layer and RGCs. Glaucomatous RGCs were transfected, and cell viability and apoptosis were examined. The targeting relationship between miR-134 and E2F6 was analyzed, as well as their expression pattern. RESULTS: Intravitreal injection of NMDA induced a significant reduction in the number of RGCs and thinning of IPL thickness. miR-134 was highly expressed and E2F6 was lowly expressed in glaucoma mice. Suppression of miR-134 or E2F6 overexpression inhibited apoptosis in the glaucomatous RGCs and instead their proliferative activity. MiR-134 targeted inhibition of E2F6 expression. Suppressing rises in E2F6 expression reduced the interfering effect of miR-134 on glaucomatous RGC development. CONCLUSION: Depleting miR134 expression increases, in turn, E2F6 expression levels and in turn reduces glaucomatous RGC apoptosis expression.