Retinal Ganglion Cell Injury Research Articles

Silencing of circular RNA‑ZYG11B exerts a neuroprotective effect against retinal neurodegeneration.

Ischemic retinal diseases are the major cause of vision impairment worldwide. Currently, there are no available treatments for ischemia-induced retinal neurodegeneration. Circular RNAs (circRNAs) have emerged as important regulators of several biological processes and human diseases. The present study investigated the role of circRNA-ZYG11B (circ-ZYG11B; hsa_circ_0003739) in retinal neurodegeneration. Reverse transcription quantitative polymerase chain reaction (RT-qPCR) demonstrated that circZYG11B expression was markedly increased during retinal neurodegeneration in vivo and in vitro. Cell Counting Kit-8, TUNEL and caspase-3 activity assays revealed that silencing of circZYG11B was able to protect against oxidative stress- or hypoxic stress-induced retinal ganglion cell (RGC) injury. Furthermore, immunofluorescence staining and hematoxylin and eosin staining revealed that silencing of circZYG11B alleviated ischemia/reperfusion-induced retinal neurodegeneration, as indicated by reduced RGC injury and decreased retinal reactive gliosis. In addition, luciferase reporter, biotin-coupled miRNA capture and RNA immunoprecipitation assays revealed that circZYG11B could regulate RGC function through circZYG11B/microRNA-620/PTEN signaling. Clinically, RT-qPCR assays demonstrated that circZYG11B expression was markedly increased in the aqueous humor of patients with glaucoma. In conclusion, circZYG11B may be considered a promising target for the diagnosis and treatment of retinal ischemic diseases.

The Effect of Aging on Retinal Function and Retinal Ganglion Cell Morphology Following Intraocular Pressure Elevation.

Aging and elevated intraocular pressure (IOP) are two major risk factors for glaucomatous optic neuropathy; a condition characterized by the selective, progressive injury, and subsequent loss of retinal ganglion cells (RGCs). We examined how age modified the capacity for RGCs to functionally recover following a reproducible IOP elevation (50 mmHg for 30 min). We found that RGC functional recovery (measured using electroretinography) was complete by 7 days in 3-month-old mice but was delayed in 12-month-old mice until 14 days. At the 7-day recovery endpoint when RGC function had recovered in young but not older eyes, we examined RGC structural responses to IOP-related stress by analyzing RGC dendritic morphology. ON-RGC cell volume was attenuated following IOP elevation in both young and older mice. We also found that following IOP elevation OFF-RGC dendritic morphology became less complex per cell volume in young mice, an effect that was not observed in older eyes. Our data suggest that adaptations in OFF-RGCs in young eyes were associated with better functional recovery 7 days after IOP elevation. Loss of RGC cellular adaptations may account for delayed functional recovery in older eyes.

Transcriptional control of retinal ganglion cell death after axonal injury

Injury to the axons of retinal ganglion cells (RGCs) is a key pathological event in glaucomatous neurodegeneration. The transcription factors JUN (the target of the c-Jun N-terminal kinases, JNKs) and DDIT3/CHOP (a mediator of the endoplasmic reticulum stress response) have been shown to control the majority of proapoptotic signaling after mechanical axonal injury in RGCs and in other models of neurodegeneration. The downstream transcriptional networks controlled by JUN and DDIT3, which are critical for RGC death, however, are not well defined. To determine these networks, RNA was isolated from the retinas of wild-type mice and mice deficient in Jun, Ddit3, and both Jun and Ddit3 three days after mechanical optic nerve crush injury (CONC). RNA-sequencing data analysis was performed and immunohistochemistry was used to validate potential transcriptional signaling changes after axonal injury. This study identified downstream transcriptional changes after injury including both neuronal survival and proinflammatory signaling that were attenuated to differing degrees by loss of Ddit3, Jun, and Ddit3/Jun. These data suggest proinflammatory signaling in the retina might be secondary to activation of pro-death pathways in RGCs after acute axonal injury. These results determine the downstream transcriptional networks important for apoptotic signaling which may be important for ordering and staging the pro-degenerative signals after mechanical axonal injury.

Long Non-Coding RNAs in Retinal Ganglion Cell Apoptosis.

Traumatic optic neuropathy or other neurodegenerative diseases, including optic nerve transection, glaucoma, and diabetic retinopathy, can lead to progressive and irreversible visual damage. Long non-coding RNAs (lncRNAs), which belong to the family of non-protein-coding transcripts, have been linked to the pathogenesis, progression, and prognosis of these lesions. Retinal ganglion cells (RGCs) are critical for the transmission of visual information to the brain, damage to which results in visual loss. Apoptosis has been identified as one of the most essential modes of RGC death. Emerging evidence suggests that lncRNAs can regulate RGC degeneration by directly or indirectly modulating apoptosis-associated signaling pathways. This review presents a comprehensive overview of the role of lncRNAs in RGC apoptosis at transcriptional, post-transcriptional, translational, and post-translational levels, emphasizing on the potential mechanisms of action. The current limitations and future perspectives of exploring the connection between lncRNAs and RGC apoptosis have been summarized. Understanding the intricate molecular interaction network of lncRNAs and RGC apoptosis will open new avenues for theidentification of novel diagnostic biomarkers, therapeutic targets, and molecules for prognostic evaluation of diseases related to RGC injury.

Human Umbilical Cord Blood-Derived CD133+CD34+ Cells Protect Retinal Endothelial Cells and Ganglion Cells in X-Irradiated Rats through Angioprotective and Neurotrophic Factors.

Radiation retinopathy (RR) is a common complication following radiation therapy of globe, head, and neck malignancies, and is characterized by microangiopathy, neuroretinopathy, and the irreversible loss of visual function. To date, there is no effective treatment for RR. Stem cells have been clinically used to treat retinal degeneration. CD133+CD34+ cells from human umbilical cord blood (hUCB-CD133+CD34+ cells), a subpopulation of hematopoietic stem cells, were applied to determine their protective efficacy on irradiated rat retinas. After X-ray irradiation on the retinas, rats were intravitreally injected with hUCB-CD133+CD34+ cells. Transplantation of hUCB-CD133+CD34+ cells prevented retinal dysfunction 2 weeks post-operation and lasted at least 8 weeks. CD133+CD34+ cells were distributed along the retinal vessel and migrated to the ganglion cell layer. Moreover, grafted CD133+CD34+ cells reduced the apoptosis of endothelial and ganglion cells in irradiated rats and increased the number of survived CD31+ retinal endothelial cells and Brn3a+ ganglion cells at 2 and 4 weeks, respectively, post-operation. Co-culturing of CD133+CD34+ cells or supernatants with irradiated human retinal microvascular endothelial cells (hRECs) in vitro, confirmed that CD133+CD34+ cells ameliorated hREC apoptosis caused by irradiation. Mechanistically, we found that angioprotective mediators and neurotrophic factors were secreted by CD133+CD34+ cells, which might attenuate irradiation-induced injury of retinal endothelial cells and ganglion cells. hUCB-CD133+CD34+ cell transplantation, as a novel treatment, protects retinal endothelial and ganglion cells of X-irradiated rat retinas, possibly through angioprotective and neurotrophic factors.

Acteoside attenuates hydrogen peroxide-induced injury of retinal ganglion cells via the CASC2/miR-155/mTOR axis.

BackgroundLoss of retinal ganglion cells (RGCs), which eventually leads to optic nerve atrophy and vision loss, is the main cause of glaucoma and traumatic optic neuropathy. Acteoside is the effective component of Yunnan Kudingcha, which has been reported to exert neuroprotective effects and protects RGCs from injury. However, the underlying mechanisms of acteoside in RGC injury remain largely elusive.MethodsHuman RGCs was treated with hydrogen peroxide (H2O2). The expression of miR-155 and lncRNA CASC2 in RGC-5 cells was measured by RT-qPCR. The viability of RGCs was determined by the MTT assay. Flow cytometry and TUNEL staining were used to detect cell apoptosis. The malondialdehyde (MDA) content and superoxide dismutase (SOD) activity were determined using ELISA kits. The mTOR and autophagic proteins were measured by western blot.ResultsWe identified the expression of miR-155 was upregulated in H2O2-treated RGCs, and enhanced miR-155 promoted RGC autophagy and apoptosis. Acteoside administration reduced miR-155 expression and abolished miR-155-mediated RGC injury. The expression of CASC2 was decreased in H2O2-treated RGCs. Acteoside administration could increase CASC2 expression and CASC2 overexpression reverses the effect of miR-155 overexpression on acteoside treatment-RGCs. Mechanistically, we discovered that highly expressed miR-155 promoted RGC autophagy and apoptosis via the mTOR pathway. In addition, acteoside attenuated RGC autophagy and apoptosis via the miR-155/mTOR axis. Together, these results identify a mechanism by which acteoside attenuates H2O2-induced RGC apoptosis and autophagy via the CASC2/miR-155/mTOR axis.ConclusionsActeoside protects RGC-5 cells against H2O2-induced cell injury via the CASC2/miR-155/mTOR axis. These results provide new insights for early medical interventions in patients with glaucoma.

Construction and analysis of mRNA, lncRNA, and transcription factor regulatory networks after retinal ganglion cell injury

Retinal ganglion cell (RGC) injury is a critical pathological feature of several optic neurodegenerative diseases. The regulatory mechanisms underlying RGC injury remain poorly understood. Recent evidence has highlighted the important roles of long noncoding RNAs (lncRNAs) in degenerative neuropathy but few studies have focused on lncRNAs associated with RGC injury. In this study, we analyzed dysregulated lncRNAs associated with RGC injury, their potential regulatory functions, and the molecular mechanisms underlying the regulation of lncRNAs and transcription factors (TFs). We analyzed lncRNA and mRNA profiles in the GSE142881 dataset associated with RGC injury and identified 1049 differentially expressed genes (DEGs), with 18 differentially expressed (DE) TFs among 883 DE mRNAs and 312 DE lncRNAs. The predicted DE lncRNAs and DE mRNAs were used to construct a lncRNA-mRNA co-expression network. Functional enrichment analysis was performed to explore the functions of the lncRNAs and mRNAs. The co-expression network between DE lncRNAs and DE mRNAs was highly enriched in inflammatory and immune-related pathways, indicating that they play role in the process of RGC injury. Among the DE mRNAs, we screened 18 DE TFs, including activating transcription factor 3 (ATF3), associated with RGC injury. Co-expression analysis predicted that 13 lncRNAs were potential binding targets of ATF3. The screening of the potential targets of these 13 lncRNAs showed that they were also significantly enriched in functional pathways associated with inflammation and apoptosis. After analysis, we constructed the mRNA-ATF3-lncRNA regulatory network after RGCs injury. In summary, we identified the gene module associated with immune and inflammatory responses after optic nerve injury and constructed a regulatory network of lncRNA-TF-mRNA. The results indicate that lncRNAs, by binding to TFs, can regulate downstream genes and function during RGC injury. The results provide a foundation for further studies of the mechanism of RGC injury and provide insight into the clinical diagnosis and investigation direction of neurodegenerative diseases such as traumatic optic neuropathy and glaucoma.

Peroxisome Proliferator-Activated Receptor α Activation Protects Retinal Ganglion Cells in Ischemia-Reperfusion Retinas.

Background and Objective: Retinal ischemia-reperfusion (IR) leads to massive loss of retinal ganglion cells (RGC) and characterizes several blind-causing ophthalmic diseases. However, the mechanism related to retinal IR is controversial, and a drug that could prevent the RGC loss caused by IR is still lacking. This study aimed to investigate the role of endogenous retinal peroxisome proliferator-activated receptor (PPAR)α and the therapeutic effect of its agonist, fenofibric acid (FA), in IR-related retinopathy.Materials and Methods: Fenofibric acid treatment was applied to the Sprague–Dawley rats with IR and retinal cell line 28 cells with oxygen-glucose deprivation (OGD) (an in vitro model of IR). Western blotting, real-time PCR, and immunofluorescence were used to examine the expression levels of PPARα, glial fibrillary acidic protein (GFAP), and cyclooxygenase-2 (COX2). Hematoxylin and eosin (HE) staining, propidium iodide (PI) staining, retrograde tracing, and flash visual-evoked potential (FVEP) were applied to assess RGC injury and visual function.Results: Retinal IR down-regulated PPARα expression in vitro and in vivo. Peroxisome proliferator-activated receptor α activation by FA promoted survival of RGCs, mitigated thinning of the ganglion cell complex, and decreased the latency of positive waves of FVEPs after IR injury. Further, FA treatment enhanced the expression of endogenous PPARα and suppressed the expression of GFAP and COX2 significantly.Conclusion: Peroxisome proliferator-activated receptor α activation by FA is protective against RGC loss in retinal IR condition, which may occur by restoring PPARα expression, inhibiting activation of glial cells, and suppressing retinal inflammation. All these findings indicate the translational potential of FA in treating IR-related retinopathy.

Bone Marrow Stromal Cells (BMSCs) Inhibit Retinal Ganglion Cell Apoptosis and Alleviate Inflammation Through Up-Regulation of MicroRNA-43 and Brain-Derived Neurotrophic Factor in Glaucoma

Glaucoma is a leading cause of vision loss mainly due to retinal ganglion cells (RGC) loss. MicroRNAs (miRNAs) are highlighted as potential biomarkers in diseases. This study aims to investigate the role of miR-43 and BMSCs in the RGC apoptosis and glaucoma.RGCs were transfected with miR-43 inhibitors and mimics, and then co-cultured with BMSCs. RT-qPCR analysis was conducted to determine miR-43 expression, whilst Western blot, and flow cytometry were carried out to assess the role of miR-43 in apoptosis and inflammation. The interaction between miR-43 and BDNF, a neurotrophic factor, was detected by dual-luciferase reporter gene assay. Overexpression of miR-43 promoted RGC proliferation and decreased apoptosis. Furthermore, miR-43 overexpression diminished the contents of apoptosis- and inflammatory-related factors, and elevated the expression of BDNF. Down-regulation of BDNF exerted similar effect as down-regulation of miR-43, enhancing apoptosis and aggravating inflammation. Importantly, BMSC treatment reversed the in vitro inhibitory effect of si-BDNF on RGC with enhancement of miR-43 expression. Mechanically, miR-43 was indicated to target BDNF in glaucoma. Collectively, miR-43 delivered by BMSCs plays an important role in the inflammatory injury and abnormal apoptosis of RGC by regulating the expression of BDNF. These findings might help development of new treatment for glaucoma and provide a promising biomarker for diagnosis and treatment.

Interplay between M\xfcller cells and microglia aggravates retinal inflammatory response in experimental glaucoma

BackgroundGlaucoma, the leading cause of irreversible blindness, is a retinal neurodegenerative disease, which results from progressive apoptotic death of retinal ganglion cells (RGCs). Although the mechanisms underlying RGC apoptosis in glaucoma are extremely complicated, an abnormal cross-talk between retinal glial cells and RGCs is generally thought to be involved. However, how interaction of Müller cells and microglia, two types of glial cells, contributes to RGC injury is largely unknown.MethodsA mouse chronic ocular hypertension (COH) experimental glaucoma model was produced. Western blotting, immunofluorescence, quantitative real-time polymerase chain reaction (q-PCR), transwell co-culture of glial cells, flow cytometry assay, ELISA, Ca2+ image, and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) techniques were employed to investigate the interaction of Müller cells and microglia, and its underlying mechanisms in COH retina.ResultsWe first showed that Müller cell activation in mice with COH induced microglia activation through the ATP/P2X7 receptor pathway. The activation of microglia resulted in a significant increase in mRNA and protein levels of pro-inflammatory factors, such as tumor necrosis factor-α and interleukin-6. These inflammatory factors in turn caused the up-regulation of mRNA expression of pro-inflammatory factors in Müller cells through a positive feedback manner.ConclusionsThese findings provide robust evidence, for the first time, that retinal inflammatory response may be aggravated by an interplay between activated two types of glial cells. These results also suggest that to reduce the interplay between Müller cells and microglia could be a potential effective strategy for preventing the loss of RGCs in glaucoma.

Senescence marker protein 30 (SMP30) protects against high glucose-induced apoptosis, oxidative stress and inflammatory response in retinal ganglion cells by enhancing Nrf2 activation via regulation of Akt/GSK-3β pathway

Senescence marker protein 30 (SMP30) is an aging-related protein that participates in the regulation of tissue damage under various pathological conditions. However, the role of SMP30 in mediating high glucose (HG)-induced injury of retinal ganglion cells (RGCs) has not been fully determined. We found that SMP30 expression declined during HG stimulation in RGCs. Cellular functional studies showed that the up-regulation of SMP30 dramatically prohibited HG-evoked apoptosis, oxidative stress and inflammatory response in RGCs. Mechanism research reported that SMP30 overexpression led to the enhancement of nuclear factor erythroid 2-related factor (Nrf2) activation in HG-stimulated RGCs. Moreover, SMP30 overexpression enhanced the phosphorylation of Akt and glucogen synthase kinase-3β (GSK-3β), and the suppression of Akt markedly abolished SMP30-mediated Nrf2 activation in HG-stimulated RGCs. Additionally, the suppression of Nrf2 substantially reversed SMP30-overexpression-induced anti-HG injury effects in RGCs. Overall, these findings suggest that SMP30 protects against HG injury of RGCs by potentiating Nrf2 through regulation of the Akt/GSK-3β pathway. Our work underscores that SMP30/Akt/GSK-3β/Nrf2 may exert a vital role in mediating the injury of RGCs during diabetic retinopathy.

The Lack of Amyloidogenic Activity Is Persistent in Old WT and APPswe/PS1ΔE9 Mouse Retinae.

We have previously reported that vision decline was not associated with amyloidogenesis processing in aging C57BL/6J wild-type (WT) mice and in a mouse model of Alzheimer’s disease, the APPswe/PS1ΔE9 transgenic mouse model (APP/PS1). This conclusion was drawn using middle-aged (10–13 months old) mice. Here, we hypothesized that compared with hippocampal and cortical neurons, the weak amyloidogenic activity of retinal neurons may result in a detectable release of amyloid β (Aβ) only in aged mice, i.e., between 14 and 24 months of age. The aim of the present study was thus to follow potential activity changes in the amyloidogenic and nonamyloidogenic pathways of young (4 months) and old (20–24 months) WT and APP/PS1 mice. Our results showed that in spite of retinal activity loss reported by electroretinogram (ERG) recordings, the level of amyloid beta precursor protein (APP) and its derivatives did not significantly vary in the eyes of old vs. young mice. Strikingly, the ectopic expression of human APPswe in APP/PS1 mice did not allow us to detect Aβ monomers at 23 months. In contrast, Aβ was observed in hippocampal and cortical tissues at this age but not at 4 months of life. In contrast, optic nerve transection-induced retinal ganglion cell injury significantly affected the level of retinal APP and the secretion of soluble APP alpha in the vitreous. Collectively, these results suggest that the amyloidogenic and nonamyloidogenic pathways are not involved in visual function decline in aging mice. In WT and APP/PS1 mice, it is proposed that retinal neurons do not have the capacity to secrete Aβ in contrast with other cortical and hippocampal neurons.

Sulfiredoxin-1 protects retinal ganglion cells from high glucose-induced oxidative stress and inflammatory injury by potentiating Nrf2 signaling via the Akt/GSK-3β pathway

Sulfiredoxin-1 (Srxn1) has been acknowledged as a remarkable pro-survival factor in the protection of cells against stress-induced damage. The persistent exposure of retinal ganglion cells (RGCs) to high glucose (HG) in diabetes induces cellular damage, which contributes to the onset of diabetic retinopathy, a severe complication of diabetes. So far, little is known about the role of Srxn1 in regulating HG-induced injury of RGCs. The goals of this work were to evaluate the possible relevance of Srxn1 in the modulation of HG-induced apoptosis, oxidative stress and inflammation of RGCs in vitro. Our data showed that HG exposure caused a marked decrease in Srxn1 expression in RGCs. The up-regulation of Srxn1 markedly decreased HG-evoked apoptosis, reactive oxygen species (ROS) generation and pro-inflammatory cytokine release in RGCs. On the contrary, the depletion of Srxn1 rendered RGCs more susceptible to HG-induced injury. Further data demonstrated that Srnx1 enhanced the activation of nuclear factor erythroid-2 (E2)-related factor 2 (Nrf2) signaling in HG-exposed RGCs associated with up-regulating the phosphorylation of Akt and glucogen synthase kinase-3β (GSK-3β). Notably, the inhibition of Akt abolished Srnx1-overexpression-mediated Nrf2 activation, while GSK-3β inhibition reversed Srnx1-depletion-mediated inactivation of Nrf2. In addition, Nrf2 inhibition partially abrogated Srnx1-mediated protective effects against HG-induced injury of RGCs. In summary, these data demonstrate that the overexpression of Srxn1 protects RGCs from the HG-induced injury of RGCs by enhancing Nrf2 signaling via modulation of Akt/GSK-3β axis. Our work highlights that the Srxn1-mediated Akt/GSK-3β/Nrf2 axis may exert a possible role in regulating RGC injury of diabetic retinopathy.

Comparison of Glaucoma-Relevant Transcriptomic Datasets Identifies Novel Drug Targets for Retinal Ganglion Cell Neuroprotection.

Glaucoma is a leading cause of blindness and is characterized by the progressive dysfunction and irreversible death of retinal ganglion cells. We aimed to identify shared differentially expressed genes (DE genes) between different glaucoma relevant models of retinal ganglion cell injury using existing RNA-sequencing data, thereby discovering targets for neuroprotective therapies. A comparison of DE genes from publicly available transcriptomic datasets identified 12 shared DE genes. The Comparative Toxicogenomics Database (CTD) was screened for compounds targeting a significant proportion of the identified DE genes. Forty compounds were identified in the CTD that interact with >50% of these shared DE genes. We next validated this approach by testing select compounds for an effect on retinal ganglion cell survival using a mouse retinal explant model. Folic acid, genistein, SB-431542, valproic acid, and WY-14643 (pirinixic acid) were tested. Folic acid, valproic acid, and WY-14643 demonstrated significant protection against retinal ganglion cell death in this model. The increasing prevalence of open access-omics data presents a resource to discover targets for future therapeutic investigation.

Simple RGC: ImageJ Plugins for Counting Retinal Ganglion Cells and Determining the Transduction Efficiency of Viral Vectors in Retinal Wholemounts

Simple RGC consists of a collection of ImageJ plugins to assist researchers investigating retinal ganglion cell (RGC) injury models in addition to helping assess the effectiveness of treatments. The first plugin named RGC Counter accurately calculates the total number of RGCs from retinal wholemount images. The second plugin named RGC Transduction measures the co-localisation between two channels making it possible to determine the transduction efficiencies of viral vectors and transgene expression levels. The third plugin named RGC Batch is a batch image processor to deliver fast analysis of large groups of microscope images. These ImageJ plugins make analysis of RGCs in retinal wholemounts easy, quick, consistent, and less prone to unconscious bias by the investigator. The plugins are freely available from the ImageJ update site https://sites.imagej.net/Sonjoonho/.

7,8-Dihydroxyflavone protects retinal ganglion cells against chronic intermittent hypoxia-induced oxidative stress damage via activation of the BDNF/TrkB signaling pathway.

Chronic intermittent hypoxia (CIH) plays a key role in the complications of obstructive sleep apnea (OSA), which is strongly associated with retinal and optic nerve diseases. Additionally, the brain-derived neurotrophic factor (BDNF)/tropomyosin receptor kinase B (TrkB) signaling pathway plays an important protective role in neuronal injury. In the present study, we investigated the role of 7,8-dihydroxyflavone (7,8-DHF) in regulating CIH-induced injury in mice retinas and rat primary retinal ganglion cells (RGCs). C57BL/6 mice and in vitro primary RGCs were exposed to CIH or normoxia and treated with or without 7,8-DHF. The mice eyeballs or cultured cells were then taken for histochemistry, immunofluorescence or biochemistry, and the protein expression of the BDNF/TrkB signaling pathway analysis. Our results showed that CIH induced oxidative stress (OS) in in vivo and in vitro models and inhibited the conversion of BDNF precursor (pro-BDNF) to a mature form of BDNF, which increased neuronal cell apoptosis. 7,8-DHF reduced the production of reactive oxygen species (ROS) caused by CIH and effectively activated TrkB signals and downstream protein kinase B (Akt) and extracellular signal-regulated kinase (Erk) survival signaling pathways, which upregulated the expression of mature BDNF. ANA-12 (a TrkB specific inhibitor) blocked the protective effect of 7,8-DHF. In short, the activation of the BDNF/TrkB signaling pathway alleviated CIH-induced oxidative stress damage of the optic nerve and retinal ganglion cells. 7,8-DHF may serve as a promising agent for OSA related neuropathy.

Traumatic Optic Neuropathy Is Associated with Visual Impairment, Neurodegeneration, and Endoplasmic Reticulum Stress in Adolescent Mice.

Traumatic brain injury (TBI) results in a number of impairments, often including visual symptoms. In some cases, visual impairments after head trauma are mediated by traumatic injury to the optic nerve, termed traumatic optic neuropathy (TON), which has few effective options for treatment. Using a murine closed-head weight-drop model of head trauma, we previously reported in adult mice that there is relatively selective injury to the optic tract and thalamic/brainstem projections of the visual system. In the current study, we performed blunt head trauma on adolescent C57BL/6 mice and investigated visual impairment in the primary visual system, now including the retina and using behavioral and histologic methods at new time points. After injury, mice displayed evidence of decreased optomotor responses illustrated by decreased optokinetic nystagmus. There did not appear to be a significant change in circadian locomotor behavior patterns, although there was an overall decrease in locomotor behavior in mice with head injury. There was evidence of axonal degeneration of optic nerve fibers with associated retinal ganglion cell death. There was also evidence of astrogliosis and microgliosis in major central targets of optic nerve projections. Further, there was elevated expression of endoplasmic reticulum (ER) stress markers in retinas of injured mice. Visual impairment, histologic markers of gliosis and neurodegeneration, and elevated ER stress marker expression persisted for at least 30 days after injury. The current results extend our previous findings in adult mice into adolescent mice, provide direct evidence of retinal ganglion cell injury after head trauma and suggest that axonal degeneration is associated with elevated ER stress in this model of TON.

Carboxymethylated chitosan alleviated oxidative stress injury in retinal ganglion cells via IncRNA-THOR/IGF2BP1 axis.

Glaucoma is an advanced nerve disorder described by the deterioration of axon and RGCs. CMCS has been previously used as an anti-apoptotic and anti-oxidant agent. The current study aimed to explore the protective impact of CMCS against H2O2-induced injury in glaucoma in vitro. The relative expression of lncRNA THOR and the protein expression of IGF2BP1 in H2O2-induced RGC-5 cells were detected by RT-PCR and western blot methods respectively. The cell viability was measured using MTT assay while apoptosis rate was measured by flow cytometry. Moreover, ROS level was measured using ROS assay kit. Furthermore, the relations between THOR and IGF2BP1 were determined by using RNA pull-down. The expression of THOR was reduced in H2O2-induced RGCs. Also, RGCs viability was inhibited while the level of ROS and cell apoptosis were enhanced. CMCS treatment considerably enhanced the expression of THOR and IGF2BP1 protein and cell viability but reduced ROS level and cell apoptosis. Moreover, IGF2BP1 protein was positively regulated by lncRNA THOR. CMCS protected the RGCs from oxidative stress via regulating lncRNA THOR/IGF2BP1. CMCS enhanced the cell viability and reduced the cell apoptosis and ROS level and protected RGCs from oxidative stress via lncRNATHOR/IGF2BP1 pathway, potentially suggesting a new therapeutic strategy for the treatment of glaucoma.

CircRNA expression profile and functional analysis in retinal ischemia-reperfusion injury

Retinal ischemia-reperfusion (I/R) is involved in the pathogenesis of many vision-threatening diseases. circRNAs act as key players in gene regulation and human diseases. However, the global circRNA expression profile in retinal I/R injury has not been fully uncovered. Herein, we established a murine model of retinal I/R injury and performed circRNA microarrays to identify I/R-related circRNAs. 1265 differentially expressed circRNAs were identified between I/R retinas and normal retinas. Notably, the detection of cWDR37 level in aqueous humor could discriminate glaucoma patients from cataract patients (AUC = 0.9367). cWdr37 silencing protected against hypoxic stress- or oxidative stress-induced retinal ganglion cell (RGC) injury. cWdr37 silencing alleviated IR-induced retinal neurodegeneration as shown by increased NeuN staining, reduced retinal reactive gliosis, and decreased retinal apoptosis. Collectively, this study provides a novel insight into the pathogenesis of retinal I/R injury. cWdr37 is a promising target for the diagnosis or treatment of I/R-related ocular diseases.

Targeted delivery of LM22A-4 by cubosomes protects retinal ganglion cells in an experimental glaucoma model

Glaucoma, a major cause of irreversible blindness worldwide, is associated with elevated intraocular pressure (IOP) and progressive loss of retinal ganglion cells (RGCs) that undergo apoptosis. A mechanism for RGCs injury involves impairment of neurotrophic support and exogenous supply of neurotrophic factors has been shown to be beneficial. However, neurotrophic factors can have widespread effects on neuronal tissues, thus targeting neurotrophic support to injured neurons may be a better neuroprotective strategy. In this study, we have encapsulated LM22A-4, a small neurotrophic factor mimetic, into Annexin V-conjugated cubosomes (L4-ACs) for targeted delivery to injured RGCs in a model of acute IOP elevation, which is induced by acute IOP elevation. We have tested cubosomes formulations that encapsulate from 9% to 33% LM22A-4. Our data indicated that cubosomes encapsulating 9% and 17% LM22A-4 exhibited a mixture of Pn3m/Im3m cubic phase, whereas 23% and 33% showed a pure Im3m cubic phase. We found that 17% L4-ACs with Pn3m/Im3m symmetries showed better in-situ and in-vitro lipid membrane interactions than the 23% and 33% L4-ACs with Im3m symmetry. In vivo experiments showed that 17% L4-ACs targeted the posterior retina and the optic nerve head, which prevented RGCs loss and improved functional outcomes in a mouse model of acute IOP elevation. These results provide evidence that Annexin V-conjugated cubosomes-based LM22A-4 delivery may be a useful targeted approach to prevent the progression of RGCs loss in glaucoma. Statement of significanceRecent studies suggest that the therapy of effectively delivering neurotrophic factors to the injured retinal ganglion cells (RGCs) could promote the survival of RGCs in glaucoma. Our present work has for the first time used cubosomes as an active targeted delivery system and have successfully delivered a neuroprotective drug to the damaged RGCs in vivo. Our new cubosomal formulation can protect apoptotic cell death in vitro and in vivo, showing that cubosomes are a promising drug carrier system for ocular drug delivery and glaucoma treatment. We have further found that by controlling cubosomes in Pn3m phase we can facilitate delivery of neuroprotective drug through apoptotic membranes. This data, we believe, has important implications for future design and formulation of cubosomes for therapeutic applications.