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Wnt signaling induces neurite outgrowth in mouse retinal ganglion cells
摘要： Wingless-type (Wnt) signaling pathways mediate axonal growth and remodeling in the embryonic optic nerve, brain and spinal cord. Recent studies demonstrated that the canonical Wnt/β-catenin signaling pathway also induces axonal regeneration after injury in the optic nerve of adult animals. However, the molecular mechanisms of Wnt-mediated axonal growth are not well understood. Additionally, because Wnt signaling is stimulated in neurons as well as neighboring non-neuronal cells, the cell type(s) responsible for Wnt-induced axonal regeneration are not known. The objectives of this study were to investigate potential mechanisms and target cells of Wnt3a stimulated neurite growth using primary retinal ganglion cell (RGC) cultures. We demonstrated that Wnt3a ligand induced dose-dependent increases in average neurite length and number of neurites in RGCs. QPCR analysis of candidate mediators showed that Wnt3a-dependent neurite growth was associated with lower expression of Ripk1 and Ripk3 genes. Additionally, inhibiting Ripk1 signaling with Necrostatin-1s led to increased neurite number per cell but not increased neurite length. Therefore, Ripk signaling may be involved in mediating the effects of Wnt3a on neurite number but Ripk activity does not seem to be required for Wnt3a-dependent regulation of neurite length. This study shows that RGCs are direct cellular targets of Wnt3a-induced axonal growth, and we identified a novel association between Wnt signaling and Rip kinases in neurite formation.
关键词： retina,Ripk1,axon,retinal ganglion cell,neurite growth,Wnt signaling
更新于2025-11-21 11:24:58
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The molecular chaperone sigma 1 receptor mediates rescue of retinal cone photoreceptor cells via modulation of NRF2
摘要： Sigma 1 receptor (Sig1R), a putative molecular chaperone, has emerged as a novel therapeutic target for retinal degenerative disease. Earlier studies showed that activation of Sig1R via the high-affinity ligand (+)-pentazocine ((+)-PTZ) induced profound rescue of cone photoreceptor cells in the rd10 mouse model of retinitis pigmentosa; however the mechanism of rescue is unknown. Improved cone function in (+)-PTZ-treated mice was accompanied by reduced oxidative stress and normalization of levels of NRF2, a transcription factor that activates antioxidant response elements (AREs) of hundreds of cytoprotective genes. Here, we tested the hypothesis that modulation of NRF2 is central to Sig1R-mediated cone rescue. Activation of Sig1R in 661W cone cells using (+)-PTZ induced dose-dependent increases in NRF2-ARE binding activity and NRF2 gene/protein expression, whereas silencing Sig1R significantly decreased NRF2 protein levels and increased oxidative stress, although (+)-PTZ did not disrupt NRF2-KEAP1 binding. In vivo studies were conducted to investigate whether, in the absence of NRF2, activation of Sig1R rescues cones. (+)-PTZ was administered systemically for several weeks to rd10/nrf2+/+ and rd10/nrf2-/- mice. Through post-natal day 42, cone function was significant in rd10/nrf2+/+, but minimal in rd10/nrf2-/- mice as indicated by electroretinographic recordings using natural noise stimuli, optical coherence tomography and retinal histological analyses. Immunodetection of cones was limited in (+)-PTZ-treated rd10/nrf2-/-, though considerable in (+)-PTZ-treated rd10/nrf2+/+mice. The data suggest that Sig1R-mediated cone rescue requires NRF2 and provide evidence for a previously-unrecognized relationship between these proteins.
关键词： retinitis pigmentosa,NRF2-KEAP1,retinal neuroprotection,retina,rd10 mouse,NRF2-Neh luciferase assay,oxidative stress
更新于2025-11-21 11:08:12
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In Vivo Fluorescence Retinal Imaging Following AAV2-Mediated Gene Delivery in the Rat Retina
摘要： PURPOSE. The purpose of this study was to evaluate longitudinal gene expression patterns by in vivo retinal imaging using a modified custom-built confocal laser-scanning microscope in experimental rats after intravitreal injection of recombinant adeno-associated virus 2 (rAAV2-green fluorescent protein [GFP]). METHODS. Ten 9-week-old Wistar rats were divided into two groups: experimental group (group 1) that received a rAAV2-GFP intravitreal injection and control group (group 2) that received a vehicle. After anesthesia using a Zoletil intraperitoneal injection, 8 μL rAAV2-GFP in group 1 or vehicle in group 2 was injected intravitreally using a 33-G Hamilton syringe. In vivo fluorescence retinal images were acquired under anesthesia at 2, 4, 6, and 13 days after rAAV or vehicle delivery. RESULTS. Differences in GFP fluorescence were identified starting from day 2 after the intravitreal injection of rAAV2-GFP in group 1. Between days 4 and 6, the intensity and area of fluorescence in the retina began to increase and peaked at day 13. Based on the pattern of GFP expression, the axon of the nerve fiber layer ganglion cell was identified. In group 2, eyes treated with the vehicle showed a small amount of autofluorescence in a limited area for up to 2 weeks, with no increase in intensity during this period. CONCLUSIONS. In vivo retinal imaging confirmed gene expression within 2 weeks after the intravitreal injection of rAAV2-GFP. Gene transfer and expression in the rat retina occurs quickly in 2 days and appears to peak within 2 weeks of gene delivery. In vivo retinal imaging may be a useful noninvasive tool to continuously monitor gene expression in the retina over time.
关键词： gene therapy,image analysis,retina
更新于2025-11-21 11:08:12
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Assessment of Different Sampling Methods for Measuring and Representing Macular Cone Density Using Flood-Illuminated Adaptive Optics
摘要： PURPOSE. To describe a standardized flood-illuminated adaptive optics (AO) imaging protocol suitable for the clinical setting and to assess sampling methods for measuring cone density. METHODS. Cone density was calculated following three measurement protocols: 50 × 50-μm sampling window values every 0.5° along the horizontal and vertical meridians (fixed-interval method), the mean density of expanding 0.5°-wide arcuate areas in the nasal, temporal, superior, and inferior quadrants (arcuate mean method), and the peak cone density of a 50 × 50-μm sampling window within expanding arcuate areas near the meridian (peak density method). Repeated imaging was performed in nine subjects to determine intersession repeatability of cone density. RESULTS. Cone density montages could be created for 67 of the 74 subjects. Image quality was determined to be adequate for automated cone counting for 35 (52%) of the 67 subjects. We found that cone density varied with different sampling methods and regions tested. In the nasal and temporal quadrants, peak density most closely resembled histological data, whereas the arcuate mean and fixed-interval methods tended to underestimate the density compared with histological data. However, in the inferior and superior quadrants, arcuate mean and fixed-interval methods most closely matched histological data, whereas the peak density method overestimated cone density compared with histological data. Intersession repeatability testing showed that repeatability was greatest when sampling by arcuate mean and lowest when sampling by fixed interval. CONCLUSIONS. We show that different methods of sampling can significantly affect cone density measurements. Therefore, care must be taken when interpreting cone density results, even in a normal population.
关键词： cone photoreceptor density,retina,adaptive optics
更新于2025-09-23 15:23:52
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Adeno-Associated Viral Gene Therapy for Inherited Retinal Disease
摘要： Inherited retinal diseases (IRDs) are a group of rare, heterogenous eye disorders caused by gene mutations that result in degeneration of the retina. There are currently limited treatment options for IRDs; however, retinal gene therapy holds great promise for the treatment of different forms of inherited blindness. One such IRD for which gene therapy has shown positive initial results is choroideremia, a rare, X-linked degenerative disorder of the retina and choroid. Mutation of the CHM gene leads to an absence of functional Rab escort protein 1 (REP1), which causes retinal pigment epithelium cell death and photoreceptor degeneration. The condition presents in childhood as night blindness, followed by progressive constriction of visual fields, generally leading to vision loss in early adulthood and total blindness thereafter. A recently developed adeno-associated virus-2 (AAV2) vector construct encoding REP1 (AAV2-REP1) has been shown to deliver a functional version of the CHM gene into the retinal pigment epithelium and photoreceptor cells. Phase 1 and 2 studies of AAV2-REP1 in patients with choroideremia have produced encouraging results, suggesting that it is possible not only to slow or stop the decline in vision following treatment with AAV2-REP1, but also to improve visual acuity in some patients.
关键词： gene therapy,choroideremia,AAV2-REP1,retina
更新于2025-09-23 15:23:52
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RefMoB, a Reflectivity Feature Model-Based Automated Method for Measuring Four Outer Retinal Hyperreflective Bands in Optical Coherence Tomography
摘要： PURPOSE. To validate a model-driven method (RefMoB) of automatically describing the four outer retinal hyperreflective bands revealed by spectral-domain optical coherence tomography (SDOCT), for comparison with histology of normal macula; to report thickness and position of bands, particularly band 2 (ellipsoid zone [EZ], commonly called IS/OS). METHODS. Foveal and superior perifoveal scans of seven SDOCT volumes of five individuals aged 28 to 69 years with healthy maculas were used (seven eyes for validation, five eyes for measurement). RefMoB determines band thickness and position by a multistage procedure that models reflectivities as a summation of Gaussians. Band thickness and positions were compared with those obtained by manual evaluators for the same scans, and compared with an independent published histological dataset. RESULTS. Agreement among manual evaluators was moderate. Relative to manual evaluation, RefMoB reported reduced thickness and vertical shifts in band positions in a band-specific manner for both simulated and empirical data. In foveal and perifoveal scans, band 1 was thick relative to the anatomical external limiting membrane, band 2 aligned with the outer one-third of the anatomical IS ellipsoid, and band 3 (IZ, interdigitation of retinal pigment epithelium and photoreceptors) was cleanly delineated. CONCLUSIONS. RefMoB is suitable for automatic description of the location and thickness of the four outer retinal hyperreflective bands. Initial results suggest that band 2 aligns with the outer ellipsoid, thus supporting its recent designation as EZ. Automated and objective delineation of band 3 will help investigations of structural biomarkers of dark-adaptation changes in aging.
关键词： age-related macular degeneration,retina,ellipsoid,segmentation,optical coherence tomography,photoreceptors,interdigitation,reflectivity,retinal pigment epithelium
更新于2025-09-23 15:23:52
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Retinal Neuroprotection From Optic Nerve Trauma by Deletion of Arginase 2
摘要： Our previous studies have implicated expression of the mitochondrial isoform of the arginase enzyme arginase 2 (A2) in neurovascular injury during ischemic retinopathies. The aim of this study was to characterize the specific involvement of A2 in retinal injury following optic nerve crush (ONC). To accomplish this, wild-type (WT) or A2 knockout (A2?/?) mice were subjected to ONC injury. The contralateral eye served as sham control. Quantitative RT-PCR and western blot were used to evaluate mRNA and protein expression. Retinal ganglion cell (RGC) survival was assessed in retinal whole mounts. Axonal sprouting was determined by anterograde transport of Cholera Toxin B (CTB). These analyses showed increased A2 expression following ONC. Numbers of NeuN-positive neurons as well as Brn3a- and RBPMS-positive RGC were decreased in the WT retinas at 14 days after ONC as compared to the sham controls. This ONC-induced neuronal loss was diminished in the A2?/? retinas. Similarly, axonal degeneration was ameliorated by A2 deletion whereas axon sprouting was enhanced. Significant retinal thinning was also seen in WT retinas at 21 days after ONC, and this was blocked in A2?/? mice. Cell death studies showed an increase in TUNEL positive cells in the RGC layer at 5 days after ONC in the WT retinas, and this was attenuated by A2 deletion. ONC increased glial cell activation in WT retinas, and this was significantly reduced by A2 deletion. Western blotting showed a marked increase in the neurotrophin, brain derived neurotrophic factor (BDNF) and its downstream signaling in A2?/? retinas vs. WT after ONC. This was associated with increases in the axonal regeneration marker GAP-43 in A2?/? retinas. Furthermore, A2?/? retinas showed decreased NLRP3 inflammasome activation and lower interleukin (IL-) 1β/IL-18 levels as compared to WT retinas subjected to ONC. Collectively, our results show that deletion of A2 limits ONC-induced neurodegeneration and glial activation, and enhances axonal sprouting by a mechanism involving increases in BDNF and decreases in retinal inflammation. These data demonstrate that A2 plays an important role in ONC-induced retinal damage. Blockade of A2 activity may offer a therapeutic strategy for preventing vision loss induced by traumatic retinal injury.
关键词： optic nerve crush,retinal ganglion cells,retina,brain derived neurotrophic factor,neuroprotection,arginase 2
更新于2025-09-23 15:23:52
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Fovea-sparing rhegmatogenous retinal detachments: impact of clinical factors including time to surgery on visual and anatomic outcomes
摘要： Purpose Evaluate the impact of time to surgery and other clinical factors on visual and anatomic outcomes following surgical repair of fovea-sparing rhegmatogenous retinal detachments (RRD). Methods Visual and anatomic outcomes were analyzed for their association with clinical factors, including lens status, preoperative visual acuity (VA), contralateral RRD, RRD symptom duration, time to surgery, single-operation anatomic success, number of quadrants involved, posterior RRD extent, RRD extent closest to the fovea, number of retinal breaks, quadrants with retinal breaks, and surgery performed Saturday or Sunday versus Monday–Friday. Results Medical records of 423 eyes with fovea-sparing RRD repaired with pneumatic retinopexy (PR), scleral buckle (SB), pars plana vitrectomy (PPV), and PPV with SB (PPV/SB) were included. Sixty-seven percent and 89% were operated within 24 and 72 h of RRD presentation, respectively. Single-operation anatomic success rates were 59%, 89%, 84%, and 92% for PR, SB, PPV, and PPV/SB interventions, respectively. Final anatomic success was 100%. Three clinical factors correlated with faster time to surgery: shorter symptom duration (p < 0.02), RRD superior location (p = 0.001), and posterior extension into the macula (p = 0.01). The time to surgery did not correlate with visual or anatomic outcomes. Two clinical factors positively correlated with postoperative vision: preoperative VA (r > 0.25, p < 0.04) and single-operation anatomic success (p < 0.04). Surgeries performed on Monday through Friday (n = 411) were associated with better anatomic outcomes compared with the limited number performed on Saturday or Sunday (n = 12) (p = 0.005), although a greater proportion of operated cases over the weekend were PR. Conclusions In the context of the current series, time to surgery did not correlate with visual or anatomic outcomes following the surgical repair of fovea-sparing RRDs. Preoperative VA and single-operation anatomic success correlated with improved visual outcome.
关键词： Retina,Retinal detachment,Vitreoretinal surgery
更新于2025-09-23 15:23:52
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Relationship between retinal vessel diameter with both retinal nerve fibre layer thickness and optic nerve head parameters in middle‐aged Caucasians: the Northern Finland Birth Cohort Eye study
摘要： Purpose: To study the normal relationship between retinal vessel diameter (RVD) with retinal nerve fibre layer (RNFL) thickness and optic nerve head (ONH) parameters in a cohort of middle-aged Caucasians. Methods: We investigated 3070 individuals (6140 eyes). Central retinal arteriolar equivalent (CRAE) and central retinal venular equivalent (CRVE) were measured in the right eye using a semi-automated computer-assisted program. Retinal nerve fibre layer (RNFL) thickness and ONH parameters were assessed with Heidelberg retinal tomography (HRT). Results: Data from 2217 persons were analysed including RNFL, CRAE, CRVE, sex, body mass index, mean arterial pressure, diabetes status, smoking status, optic disc area, rim area, spherical refraction and intraocular pressure. A larger RVD was associated with a thicker mean global RNFL thickness especially in global and inferior segments of the retina and with larger optic discs. Each 10 lm increase in the retinal arteriolar calibre was associated with a 5.58 lm increase in mean global RNFL thickness; the corresponding value for a 10 lm increase in venular calibre was 3.79 lm (p < 0.001 for both). Retinal venular calibre displayed consistent associations with RNFL thickness in both genders (p < 0.001 for all), whereas the association of arteriolar calibre and RNFL was more prominent in men (p < 0.001). Conclusion: We found strong associations between larger RVD and thicker RNFL in all subjects. This study helps to clarify the association between RVD, RNFL thickness and ONH parameters and provides normal values for middle-aged Caucasians that will help in future studies investigating the role of vascular aetiology in systemic and eye diseases.
关键词： optic nerve head,retina,IVAN,Heidelberg retinal tomography,central retinal venular equivalent,central retinal arteriolar equivalent
更新于2025-09-23 15:23:52
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Functional Diversity in the Retina Improves the Population Code
摘要： Within a given brain region, individual neurons exhibit a wide variety of different feature selectivities. Here, we investigated the impact of this extensive functional diversity on the population neural code. Our approach was to build optimal decoders to discriminate among stimuli using the spiking output of a real, measured neural population and compare its performance against a matched, homogeneous neural population with the same number of cells and spikes. Analyzing large populations of retinal ganglion cells, we found that the real, heterogeneous population can yield a discrimination error lower than the homogeneous population by several orders of magnitude and consequently can encode much more visual information. This effect increases with population size and with graded degrees of heterogeneity. We complemented these results with an analysis of coding based on the Chernoff distance, as well as derivations of inequalities on coding in certain limits, from which we can conclude that the beneficial effect of heterogeneity occurs over a broad set of conditions. Together, our results indicate that the presence of functional diversity in neural populations can enhance their coding fidelity appreciably. A noteworthy outcome of our study is that this effect can be extremely strong and should be taken into account when investigating design principles for neural circuits.
关键词： retina,neural coding,discrimination error,mutual information,functional diversity,Chernoff distance,population code,heterogeneity
更新于2025-09-23 15:23:52