The alternative complement pathway drives neuroinflammation and neurodegeneration in mouse models of glaucoma and optic nerve injury.

Glaucoma is a leading cause of irreversible blindness, characterized by progressive retinal ganglion cell (RGC) loss and optic nerve degeneration. Mitochondrial dysfunction plays a central role in this neurodegeneration, yet effective targeted therapies remain limited. Here, we identify the mitochondrial scaffold A-kinase anchoring protein 1 (AKAP1) as a critical regulator of RGC resilience and axon regeneration. AKAP1 expression is diminished in human glaucomatous retinas and experimental glaucoma models, correlating with elevated intraocular pressure, disrupted mitochondrial dynamics, oxidative stress, and synaptic instability. Restoration of AKAP1 via adeno-associated virus serotype 2-mediated gene therapy preserves RGC survival, promotes mitochondrial fusion and cristae integrity, enhances ATP production, and mitigates oxidative and apoptotic stress in mouse models of glaucoma and optic nerve injury. Transcriptomic profiling of AKAP1 knockout retinas reveals widespread dysregulation of mitochondrial and synaptic gene networks. Mechanistically, AKAP1 stabilizes synapses by promoting mitochondrial biogenesis, modulating calcium/calmodulin-dependent kinase II and synapsin phosphorylation, maintaining synaptophysin expression, and suppressing complement component C1q expression, thereby preventing early synaptic loss in glaucomatous neurodegeneration. Moreover, restoring AKAP1 expression facilitates axonal regeneration, preserves the central visual pathway, and maintains visual function. Collectively, these findings establish AKAP1 as a master regulator of mitochondrial and synaptic homeostasis and axonal regeneration and a promising therapeutic target for vision preservation in glaucomatous neurodegeneration.One Sentence SummaryAKAP1 protects retinal ganglion cells and preserves vision by restoring mitochondrial and synaptic health in experimental glaucoma models.

PurposeGlaucoma is characterized by progressive retinal ganglion cell (RGC) death and optic nerve degeneration. Chemokines are a family of small, secreted proteins that mediate cell-cell communication, an essential process for maintaining microenvironmental homeostasis and regulating pathophysiological changes in multicellular organisms. However, the contribution of retina-derived chemokines to RGC loss in glaucoma remains poorly understood.MethodsWe reanalyzed a publicly available retinal bulk RNA sequencing dataset from a mouse model of glaucoma to identify differentially expressed chemokines. A mouse model of microbead-induced glaucoma and primary RGCs and astrocytes were used to assess the role of the C–X–C motif chemokine ligand 10 (CXCL10)/C–X–C motif chemokine receptor 3 (CXCR3) axis in disease.ResultsSeveral chemokines were significantly upregulated during disease progression, including CXCL10, previously implicated in neurodegeneration. In the microbead model, CXCL10 expression increased markedly by day 5 post-injection. At 6 weeks, deletion of CXCR3, the receptor for CXCL10, significantly prevented RGC loss and axonal degeneration without affecting intraocular pressure (IOP). Visual function, assessed by pattern electroretinography and visual acuity, was preserved in CXCR3-deficient mice. Mechanistically, CXCL10/CXCR3 signaling upregulated complement component 3 (C3) in astrocytes and C3a receptor (C3aR) in RGCs, driving toxic astrocyte–RGC crosstalk. Gene therapy using intravitreal injection of adeno-associated virus-mediated dominant-negative CXCL10 or pharmacological blockade of C3aR effectively reduced RGC loss.ConclusionsCXCL10/CXCR3 signaling is a key mediator of RGC loss in glaucoma. Targeting this pathway, along with its upregulated C3/C3aR axis, represents a promising IOP–independent therapeutic strategy for glaucoma.

To investigate the apoptosis in retinal ganglion cells (RGCs) and insulin-like growth factor 1 receptor (IGF-1R) in the retina following optic nerve crush. Healthy Wistar rats (N = 70) were divided into two groups: a normal control group and an optic nerve injury group. Immunohistochemistry and flow cytometry were performed to detect the expression of IGF-1R and to measure the apoptosis of RGCs, respectively. Immunohistochemistry revealed that at 1 hr after optic nerve injury, IGF-1R immunoreactivity began to increase and reached a maximal level at 24 hr (p < 0.05), where it remained elevated up to 14 days after injury. RGC apoptosis in the normal control group was 0.53%, while the apoptosis rate in the optic nerve injury group increased over time. The apoptosis rate in the optic nerve injury group was 1.4% at 1 hr, 4.4% at 6 hr, 5.2% at 12 hr and reached a maximal level (8.5%) at 24 hr. Subsequently, the rate declined to 1.9% 7 days after injury and 0.9% 2 weeks after injury. The IGF-1R immunereactivity in the retina increased after optic nerve injury. IGF-1R may regulate the apoptosis and regeneration of RGCs at different stages after optic nerve injury.

Glaucoma is a multifactorial blinding disease with a major inflammatory component ultimately leading to apoptotic retinal ganglion cell (RGC) death. Pharmacological treatments lowering intraocular pressure can help slow or prevent vision loss although the damage caused by glaucoma cannot be reversed. Recently, nutritional approaches have been evaluated for their efficacy in preventing degenerative events in the retina although mechanisms underlying their effectiveness remain to be elucidated. Here, we evaluated the efficacy of a diet supplement consisting of forskolin, homotaurine, spearmint extract, and vitamins of the B group in counteracting retinal dysfunction in a mouse model of optic nerve crush (ONC) used as an in vivo model of glaucoma. After demonstrating that ONC did not affect retinal vasculature by fluorescein angiography, we determined the effect of the diet supplement on the photopic negative response (PhNR) whose amplitude is strictly related to RGC integrity and is therefore drastically reduced in concomitance with RGC death. We found that the diet supplementation prevents the reduction of PhNR amplitude (p < 0.001) and concomitantly counteracts RGC death, as in supplemented mice, RGC number assessed immunohistochemically is significantly higher than that in non-supplemented animals (p < 0.01). Major determinants of the protective efficacy of the compound are due to a reduction of ONC-associated cytokine secretion leading to decreased levels of apoptotic markers that in supplemented mice are significantly lower than in non-supplemented animals (p < 0.001), ultimately causing RGC survival and ameliorated visual dysfunction. Overall, our data suggest that the above association of compounds plays a neuroprotective role in this mouse model of glaucoma thus offering a new perspective in inflammation-associated neurodegenerative diseases of the inner retina.

Retinal ganglion cells, a crucial component of the central nervous system, are often affected by irreversible visual impairment due to various conditions, including trauma, tumors, ischemia, and glaucoma. Studies have shown that the optic nerve crush model and glaucoma model are commonly used to study retinal ganglion cell injury. While these models differ in their mechanisms, both ultimately result in retinal ganglion cell injury. With advancements in high-throughput technologies, techniques such as microarray analysis, RNA sequencing, and single-cell RNA sequencing have been widely applied to characterize the transcriptomic profiles of retinal ganglion cell injury, revealing underlying molecular mechanisms. This review focuses on optic nerve crush and glaucoma models, elucidating the mechanisms of optic nerve injury and neuron degeneration induced by glaucoma through single-cell transcriptomics, transcriptome analysis, and chip analysis. Research using the optic nerve crush model has shown that different retinal ganglion cell subtypes exhibit varying survival and regenerative capacities following injury. Single-cell RNA sequencing has identified multiple genes associated with retinal ganglion cell protection and regeneration, such as Gal , Ucn , and Anxa2 . In glaucoma models, high-throughput sequencing has revealed transcriptomic changes in retinal ganglion cells under elevated intraocular pressure, identifying genes related to immune response, oxidative stress, and apoptosis. These genes are significantly upregulated early after optic nerve injury and may play key roles in neuroprotection and axon regeneration. Additionally, CRISPR-Cas9 screening and ATAC-seq analysis have identified key transcription factors that regulate retinal ganglion cell survival and axon regeneration, offering new potential targets for neurorepair strategies in glaucoma. In summary, single-cell transcriptomic technologies provide unprecedented insights into the molecular mechanisms underlying optic nerve injury, aiding in the identification of novel therapeutic targets. Future researchers should integrate advanced single-cell sequencing with multi-omics approaches to investigate cell-specific responses in retinal ganglion cell injury and regeneration. Furthermore, computational models and systems biology methods could help predict molecular pathways interactions, providing valuable guidance for clinical research on optic nerve regeneration and repair.

Experimental studies have yielded a wealth of information related to the pathological mechanism of optic nerve injury. However, there is no suitable animal model to study intracranial optic nerve injury. To establish an experimental model of acute optic nerve injury. We established an animal model of acute intracranial optic nerve injury using the classic pterional approach in cats and investigated electrophysiological and ultrastructural changes. We applied immunohistochemical staining to examine the expression of glial fibrillary acid protein, neurofilament protein, myelin basic protein pre- and post-injury. We successfully established an animal model of acute intracranial optic nerve injury. The pathological processes of acute optic nerve injury may involve the following series of steps. Direct mechanical injury of the optic nerve leads to the death of oligodendrocytes in the optic nerve, which consequently results in optic nerve demyelination. Following optic nerve injury, the astrocytes in the injured area die and produce excitatory amino acids, which have an adverse effect on neurons, resulting in the proliferation and activation of astrocytes. The astrocytes can absorb the glutamic acid and transform it into atoxic glutamine. The glutamic acid can then injure retinal ganglion cells, resulting in the reduction of neurofilament proteins in the axons. We believe that the application of the pterional approach to establish optic nerve injury animal models has both a clinical and theoretical basis.

JOURNAL/nrgr/04.03/01300535-202502000-00034/figure1/v/2024-05-28T214302Z/r/image-tiff Several studies have found that transplantation of neural progenitor cells (NPCs) promotes the survival of injured neurons. However, a poor integration rate and high risk of tumorigenicity after cell transplantation limits their clinical application. Small extracellular vesicles (sEVs) contain bioactive molecules for neuronal protection and regeneration. Previous studies have shown that stem/progenitor cell-derived sEVs can promote neuronal survival and recovery of neurological function in neurodegenerative eye diseases and other eye diseases. In this study, we intravitreally transplanted sEVs derived from human induced pluripotent stem cells (hiPSCs) and hiPSCs-differentiated NPCs (hiPSC-NPC) in a mouse model of optic nerve crush. Our results show that these intravitreally injected sEVs were ingested by retinal cells, especially those localized in the ganglion cell layer. Treatment with hiPSC-NPC-derived sEVs mitigated optic nerve crush-induced retinal ganglion cell degeneration, and regulated the retinal microenvironment by inhibiting excessive activation of microglia. Component analysis further revealed that hiPSC-NPC derived sEVs transported neuroprotective and anti-inflammatory miRNA cargos to target cells, which had protective effects on RGCs after optic nerve injury. These findings suggest that sEVs derived from hiPSC-NPC are a promising cell-free therapeutic strategy for optic neuropathy.

BackgroundGlaucoma is a leading neurodegenerative disease affecting over 70 million individuals worldwide. Early pathological events of axonal degeneration and retinopathy in response to elevated intraocular pressure (IOP) are limited and not well-defined due to the lack of appropriate animal models that faithfully replicate all the phenotypes of primary open angle glaucoma (POAG), the most common form of glaucoma. Glucocorticoid (GC)-induced ocular hypertension (OHT) and its associated iatrogenic open-angle glaucoma share many features with POAG. Here, we characterized a novel mouse model of GC-induced OHT for glaucomatous neurodegeneration and further explored early pathological events of axonal degeneration in response to elevated IOP.MethodsC57BL/6 J mice were periocularly injected with either vehicle or the potent GC, dexamethasone 21-acetate (Dex) once a week for 10 weeks. Glaucoma phenotypes including IOP, outflow facility, structural and functional loss of retinal ganglion cells (RGCs), optic nerve (ON) degeneration, gliosis, and anterograde axonal transport deficits were examined at various stages of OHT.ResultsProlonged treatment with Dex leads to glaucoma in mice similar to POAG patients including IOP elevation due to reduced outflow facility and dysfunction of trabecular meshwork, progressive ON degeneration and structural and functional loss of RGCs. Lowering of IOP rescued Dex-induced ON degeneration and RGC loss, suggesting that glaucomatous neurodegeneration is IOP dependent. Also, Dex-induced neurodegeneration was associated with activation of astrocytes, axonal transport deficits, ON demyelination, mitochondrial accumulation and immune cell infiltration in the optic nerve head (ONH) region. Our studies further show that ON degeneration precedes structural and functional loss of RGCs in Dex-treated mice. Axonal damage and transport deficits initiate at the ONH and progress toward the distal end of ON and target regions in the brain (i.e. superior colliculus). Most of anterograde transport was preserved during initial stages of axonal degeneration (30% loss) and complete transport deficits were only observed at the ONH during later stages of severe axonal degeneration (50% loss).ConclusionsThese findings indicate that ON degeneration and transport deficits at the ONH precede RGC structural and functional loss and provide a new potential therapeutic window for rescuing neuronal loss and restoring health of damaged axons in glaucoma.

Establishing a cat model of acute optic nerve injury

Targeting HDAC3 in the DBA/2J spontaneous mouse model of glaucoma

Simple SummaryGlaucoma is a leading cause of blindness worldwide, and increased age and intraocular pressure (IOP) are the major risk factors. Glaucoma is characterized by the death of nerve cells and the loss of optic nerve fibers. Recently, evidence has accumulated indicating that proteins in the environment of nerve cells, called the extracellular matrix (ECM), play an important role in glaucomatous neurodegeneration. Depending on its constitution, the ECM can influence either the survival or the death of nerve cells. Thus, the aim of our study was to comparatively explore alterations of various ECM molecules in the retina and optic nerve of aged control and glaucomatous mice with chronic IOP elevation. Interestingly, we observed elevated levels of blood vessel and glial cell-associated ECM components in the glaucomatous retina and optic nerve, which could be responsible for various pathological processes. A better understanding of the underlying signaling mechanisms may help to develop new diagnostic and therapeutic strategies for glaucoma patients.Glaucoma is a neurodegenerative disease that is characterized by the loss of retinal ganglion cells (RGC) and optic nerve fibers. Increased age and intraocular pressure (IOP) elevation are the main risk factors for developing glaucoma. Mice that are heterozygous (HET) for the mega-karyocyte protein tyrosine phosphatase 2 (PTP-Meg2) show chronic and progressive IOP elevation, severe RGCs loss, and optic nerve damage, and represent a valuable model for IOP-dependent primary open-angle glaucoma (POAG). Previously, evidence accumulated suggesting that glaucomatous neurodegeneration is associated with the extensive remodeling of extracellular matrix (ECM) molecules. Unfortunately, little is known about the exact ECM changes in the glaucomatous retina and optic nerve. Hence, the goal of the present study was to comparatively explore ECM alterations in glaucomatous PTP-Meg2 HET and control wild type (WT) mice. Due to their potential relevance in glaucomatous neurodegeneration, we specifically analyzed the expression pattern of the ECM glycoproteins fibronectin, laminin, tenascin-C, and tenascin-R as well as the proteoglycans aggrecan, brevican, and members of the receptor protein tyrosine phosphatase beta/zeta (RPTPβ/ζ) family. The analyses were carried out in the retina and optic nerve of glaucomatous PTP-Meg2 HET and WT mice using quantitative real-time PCR (RT-qPCR), immunohistochemistry, and Western blot. Interestingly, we observed increased fibronectin and laminin levels in the glaucomatous HET retina and optic nerve compared to the WT group. RT-qPCR analyses of the laminins α4, β2 and γ3 showed an altered isoform-specific regulation in the HET retina and optic nerve. In addition, an upregulation of tenascin-C and its interaction partner RPTPβ/ζ/phosphacan was found in glaucomatous tissue. However, comparable protein and mRNA levels for tenascin-R as well as aggrecan and brevican were observed in both groups. Overall, our study showed a remodeling of various ECM components in the glaucomatous retina and optic nerve of PTP-Meg2 HET mice. This dysregulation could be responsible for pathological processes such as neovascularization, inflammation, and reactive gliosis in glaucomatous neurodegeneration.

Complement in Glomerular Disease

Sirt6 protects retinal ganglion cells and optic nerve from degeneration during aging and glaucoma

To evaluate the efficacy and safety of attenuated Herpes simplex virus 1 (HSV-1) vector expressing oncomodulin (OCM) for treatment of mechanical optic nerve injury in rats. The proliferation characteristics and OCM expression of the recombinant HSV-1 vector (1716-OCM) was assessed in cultured Vero cells. Twelve-week-old SD rats were randomly divided into control group, 1716-OCM injection group and wild-type virus corneal infection group, and at 7, 14, 30 and 60 days post-infection (3 rats in each group at each time point), the expressions of OCM and HSV-1 structural protein gB in the retina and the hypothalamus of the rats were detected using immunofluorescence assay. Another 20 rats were randomized into sham operation group, PBS treatment group, 1716-OCM infection group and 1716-OCM infection with cAMP sensitization group (n=5), and in the latter 3 groups, rat models of optic nerve injury models were established followed by intravitreal injection of PBS, 1716-OCM or cAMP as indicated. At 45 days after the treatments, the rats were examined for visual electrophysiological function using FVEP method, and the number of retinal ganglion cells (RGCs) and the expression of myelin basic protein in the optic nerve were detected using immunofluorescence assay. The recombinant 1716-OCM vector was capable of mediating effective expression of OCM in Vero cells in vitro, but its proliferation rate was much lower than that of the wild-type virus. In SD rats, the recombinant virus could mediate the expression of OCM in the RGC layer and choroid layer of the eyes without inducing significant structural damage of the eyes as compared with the wild-type virus. In rat models of optic nerve injury, 1716-OCM combined with cAMP significantly promoted the survival of retinal RGCs (P= 0.007) and inhibited demyelination of the optic nerve (P=0.03) as compared with the mock treatment. FVEP analysis showed that 1716-OCM combined with cAMP significantly promoted the recovery of the peak amplitude of ΔN1-P1 in the rats (P < 0.0001). Attenuated recombinant 1716-OCM vector can mediate OCM expression in the retina of rats, and in rat models of mechanical optic nerve injury, intravitreal injection of 1716-OCM combined with cAMP can effectively alleviate optic nerve injuries.

Study on the deformations of the lamina cribrosa during glaucoma.