Müller cells as players in retinal degeneration and edema

Role of inflammation in a rat model of radiation retinopathy

Radiation retinopathy (RR) is a major side effect of ocular tumor treatment by plaque brachytherapy or proton beam therapy. RR manifests as delayed and progressive microvasculopathy, ischemia and macular edema, ultimately leading to vision loss, neovascular glaucoma, and, in extreme cases, secondary enucleation. Intravitreal anti-VEGF agents, steroids and laser photocoagulation have limited effects on RR. The role of retinal inflammation and its contribution to the microvascular damage occurring in RR remain incompletely understood. To explore cellular and vascular events after irradiation, we analyzed their time course at 1 week, 1 month and 6 months after rat eyes received 45 Gy X-beam photons. Müller glial cells, astrocytes and microglia were rapidly activated, and these markers of retinal inflammation persisted for 6 months after irradiation. This was accompanied by early cell death in the outer retina, which persisted at later time points, leading to retinal thinning. A delayed loss of small retinal capillaries and retinal hypoxia were observed after 6 months, indicating inner blood‒retinal barrier (BRB) alteration but without cell death in the inner retina. Moreover, activated microglial cells invaded the entire retina and surrounded retinal vessels, suggesting the role of inflammation in vascular alteration and in retinal cell death. Radiation also triggered early and persistent invasion of the retinal pigment epithelium by microglia and macrophages, contributing to outer BRB disruption. This study highlights the role of progressive and long-lasting inflammatory mechanisms in RR development and demonstrates the relevance of this rat model to investigate human pathology.

Association between choroidal thickness and diabetic macular edema: a meta-analysis

AIMS

To evaluate the association between subfoveal choroidal thickness (SFCT) and diabetic macular edema (DME).

DESIGN

A systematic review and meta-analysis.

METHODS

A retrospective or prospective study comparing SFCT in diabetic retinopathy (DR) patients with and without DME was included. The data were collected from published studies retrieved from PubMed, Web of Science, Embase, Ovid Medline, and Cochrane Library. The final search was conducted on July 2, 2023. Heterogeneity was assessed using I2 statistics, and a random-effects model was used for the meta analysis. This study calculated the weighted mean difference (WMD) and 95% confidence interval (CI) for SFCT.

RESULTS

A total of 26 relevant studies were identified, involving a combined sample size of 3201 eyes (1302 DR-DME eyes and 1899 DR-no DME eyes). The results showed no significance between DR-DME and DR-no DME (WMD = - 3.57 μm; 95% CI -26.54 to 19.41 μm; P = 0.76). Sub-analysis based on nonproliferative diabetic retinopathy (NPDR) and proliferative diabetic retinopathy (PDR) subgroups showed that the SFCT of NPDR-DME was significantly thinner than that of NPDR-no DME eyes (WMD = - 19.80 μm; 95% CI - 34.55 to - 5.04 μm; P = 0.009), while there was no significance in SFCT between PDR-DME and PDR-no DME (WMD = - 26.45 μm; 95% CI - 104.00 to 51.11 μm; P = 0.50).

CONCLUSION

The SFCT was thinner in NPDR-DME eyes compared to NPDR-no DME eyes. Thinning SFCT might cause retinal hypoxia, and play an important role in DME occurrence. Additionally, this study highlights the importance of considering DR grades and treatment history when evaluating SFCT between DME and no DME.

Purinergic P2X7 receptor involves in anti-retinal photodamage effects of berberine

Berberine (BBR) is a Chinese herb with antioxidant and anti-inflammatory properties. In a previous study, we found that BBR had a protective effect against light-induced retinal degeneration in BALB/c mice. The purinergic P2X7 receptor (P2X7R) plays a key role in retinal degeneration via inducing oxidative stress, inflammatory changes, and cell death. The aim of this study was to investigate whether BBR can induce protective effects in light damage experiments and whether P2X7R can get involved in these effects. C57BL/6 J mice and P2X7 knockout (KO) mice on the C57BL/6 J background were used. We found that BBR preserved the outer nuclear layer (ONL) thickness and retinal ganglion cells following light stimulation. Furthermore, BBR significantly suppressed photoreceptor apoptosis, pro-apoptotic c-fos expression, pro-inflammatory responses of Mϋller cells, and inflammatory factors (TNF-α, IL-1β). In addition, protein levels of P2X7R were downregulated in BBR-treated mice. Double immunofluorescence showed that BBR reduced overexpression of P2X7R in retinal ganglion cells and Mϋller cells. Furthermore, BBR combined with the P2X7R agonist BzATP blocked the effects of BBR on retinal morphology and photoreceptor apoptosis. However, in P2X7 KO mice, BBR had an additive effect resulting in thicker ONL and more photoreceptors. The data suggest that the P2X7 receptor is involved in retinal light damage, and BBR inhibits this process by reducing histological impairment, cell death, and inflammatory responses.

Acetazolamide Challenge Changes Outer Retina Bioenergy-Linked and Anatomical OCT Biomarkers Depending on Mouse Strain

Purpose

The purpose of this study was to test the hypothesis that optical coherence tomography (OCT) bioenergy-linked and anatomical biomarkers are responsive to an acetazolamide (ACZ) provocation.

Methods

C57BL/6J mice (B6J, a strain with relatively inefficient mitochondria) and 129S6/ev mice (S6, a strain with relatively efficient mitochondria) were given a single IP injection of ACZ (carbonic anhydrase inhibitor) or vehicle. In each mouse, the Mitochondrial Configuration within Photoreceptors based on the profile shape Aspect Ratio (MCP/AR) index was determined from the hyper-reflective band immediately posterior to the external limiting membrane (ELM). In addition, we tested for ACZ-induced acidification by measuring contraction of the external limiting membrane-retinal pigment epithelium (ELM-RPE) thickness; the hyporeflective band (HB) signal intensity at the photoreceptor tips was also examined. Finally, the nuclear layer thickness was measured.

Results

In response to ACZ, MCP/AR was greater-than-vehicle in B6J mice and lower-than-vehicle in S6 mice. ACZ-treated B6J and S6 mice both showed ELM-RPE contraction compared to vehicle-treated mice, consistent with dehydration in response to subretinal space acidification. The HB intensity at the photoreceptor tips and the outer nuclear layer thickness (B6J and S6), as well as the inner nuclear layer thickness of B6J mice, were all lower than vehicle following ACZ.

Conclusions

Photoreceptor respiratory efficacy can be evaluated in vivo based on distinct rod mitochondria responses to subretinal space acidification measured with OCT biomarkers and an ACZ challenge, supporting and extending our previous findings measured with light-dark conditions.

Cystoid macular edema as a complication of central retinal artery occlusion

Purpose

To describe the development of cystoid macular edema (CME) as a complication of central retinal artery occlusion (CRAO) in 2 cases.

Observations

The first patient was a 51-year-old female who presented with acute loss of vision in the left eye. Multimodal retinal imaging revealed a CRAO with a perfused cilioretinal artery. CME acutely developed one week after presentation. Cystoid spaces predominantly involved the outer nuclear layer (ONL) on optical coherence tomography (OCT) and completely resolved in two weeks. The second case was a 50-year-old man who presented with acute vision loss in the right eye for 3 weeks. Multimodal retinal imaging illustrated an acute CRAO of the right eye. Four weeks later, visual acuity spontaneously improved to 20/20 and was maintained at 20/20 for more than 2 years. After 28 months, the patient returned with a recurrent drop of vision in the right eye. Cross sectional and en face OCT revealed CME in the right eye without leakage on FA. Cystoid spaces predominantly involved the inner nuclear layer (INL) and resolved with intravitreal anti-VEGF injection combined with carbonic anhydrase inhibitor (CAI) and steroid topical drop therapy.

Conclusions and Importance

CME can rarely complicate both the acute and chronic phase of CRAO. In the acute phase, cystoid spaces were transient and confined to the ONL on OCT. While in the chronic phase, cystoid spaces were confined to the INL on OCT and angiographically silent on FA. Further studies are needed to identify the incidence, underlying pathophysiology and visual prognosis of CME in cases of CRAO.

The role of retinal glial cells and related factors in macular edema

Macular edema (ME) has emerged as a leading cause of visual impairment, representing a critical clinical manifestation and complication associated with many eye diseases. In the occurrence and development of ME, retinal glial cells like Müller cells and microglial cells play vital roles. Moreover, growth factor and cytokines associated with them, such as vascular endothelial growth factor (VEGF), pigment epithelium-derived factor (PEDF), hypoxia-inducible factor-1α (HIF-1α), angiopoietin-like protein 4 (ANGPTL4), interleukin-6(IL-6), interleukin-8 (IL-8), monocyte chemoattractant protein-1 (MCP-1), prostaglandin, etc., also take part in the pathogenesis of ME. Changes in these cytokines can lead to retinal angiogenesis, increased vascular permeability, blood-retinal barrier (BRB) breakdown, and fluid leakage, further causing ME to occur or deteriorate. Research on the role of retinal glial cells and related cytokines in ME will provide new therapeutic directions and effective remedies. This article is a literature review on the role of Müller cells, microglial cells and related factors in ME pathogenesis.

Protocol for the treatment of cystoid macular edema secondary to retinitis pigmentosa and other inherited retinal dystrophies

Inherited retinal dystrophies (IRD) are the leading cause of legal blindness in the working population. Cystic macular edema (CME) is one of the treatable causes of visual loss, affecting up to 50% of the patients. A bibliographic review has been carried out combining "inherited retinal dystrophy", "retinitis pigmentosa", "macular oedema" and a diagnostic-therapeutic protocol according to the levels of evidence and recommendations of the "US Agency for Healthcare Research and Quality". This protocol has been discussed in the monthly meetings of the XAREA DHR group with the participation of more than 25 ophthalmologists, creating a consensus document. The etiology of CME is multifactorial: dysfunction of the blood-retinal barrier, retinal pigment epithelium, and Müller cells, inflammation, and vitreous traction. OCT is the test of choice for the diagnosis and follow-up of CME associated with IRD. The drugs with the highest degree of scientific evidence are carbonic anhydrase inhibitors (IAC). Intravitreal corticosteroids, anti-VEGF, and vitrectomy with peeling of the internal limiting membrane do not have sufficient evidence. A treatment scheme is proposed for the CME in IRD in adults, another for pediatric patients and another for IRD and cataract surgery. Oral and topical IACs are effective in the treatment of CME secondary to IRD. Treatment with corticosteroids, anti-VEGF, and vitrectomy are second-line options. Randomized clinical trials are required to establish the therapeutic scale in these patients.

The glucocorticoid receptor as a master regulator of the Müller cell response to diabetic conditions in mice

Diabetic retinopathy (DR) is considered a primarily microvascular complication of diabetes. Müller glia cells are at the centre of the retinal neurovascular unit and play a critical role in DR. We therefore investigated Müller cell-specific signalling pathways that are altered in DR to identify novel targets for gene therapy. Using a multi-omics approach on purified Müller cells from diabetic db/db mice, we found the mRNA and protein expression of the glucocorticoid receptor (GR) to be significantly decreased, while its target gene cluster was down-regulated. Further, oPOSSUM TF analysis and ATAC- sequencing identified the GR as a master regulator of Müller cell response to diabetic conditions. Cortisol not only increased GR phosphorylation. It also induced changes in the expression of known GR target genes in retinal explants. Finally, retinal functionality was improved by AAV-mediated overexpression of GR in Müller cells. Our study demonstrates an important role of the glial GR in DR and implies that therapeutic approaches targeting this signalling pathway should be aimed at increasing GR expression rather than the addition of more ligand.

Clostridium perfringens Type D Epsilon Toxin Causes Blood-Retinal Barrier Microvascular Damage and Diffuse Retinal Vasogenic Oedema

Clostridium perfringens type D epsilon toxin (ETX) causes severe retinal microvascular endothelial injury in the rat. The resulting blood-retinal barrier (BRB) breakdown leads to increased vascular permeability, which was detected immunohistochemically by the extravasation of plasma albumin as a vascular tracer, and ensuing severe, diffuse, vasogenic retinal oedema. This microvascular damage was also confirmed by a loss of endothelial barrier antigen, a marker of an intact BRB in rats. Since similar microvascular lesions are found in EXT-exposed laboratory rodent and sheep brains, and the BRB resembles the BBB, they are also likely to occur in the eyes of naturally epsilon-intoxicated sheep and goats, but this remains to be determined. Moreover, while retinal oedema is a common and important component of many human and veterinary ocular disorders, more effective treatments are required. Accordingly, the retinal vasogenic oedema reliably and reproducibly induced by ETX in rats provides a useful model in which to study the pathogenesis of retinal oedema development and evaluate its prevention or amelioration by putative pharmacological interventions.

The prevalence and presentation patterns of microcystic macular oedema: a systematic review and meta-analysis of 2128 glaucomatous eyes

We conducted this research to determine the prevalence rate and presentation patterns with microcystic macular oedema (MMO) in glaucoma patients. The protocol was pre-registered on PROSPERO ( CRD42022316367 ). PubMed, Scopus, Web of Science, EMBASE, ProQuest, EBSCOHost, CENTRAL, clinicaltrials.gov, and Google Scholar were searched for articles reporting MMO in glaucoma patients. The primary outcome was the prevalence of MMO, while secondary outcomes included the comparison between MMO and non-MMO in terms of patients' characteristics (age, gender), glaucoma stage, and ocular parameters (axial length (AL), intraocular pressure, mean deviation, spherical equivalent). Data are reported as mean difference (MD) or log odds ratio (logOR) along with their corresponding 95% confidence intervals (CI) for continuous and dichotomous outcomes, respectively. The quality of included studies was assessed using the NIH tool, and the certainty of evidence was assessed using GRADE framework. Ten studies (2128 eyes) were included, revealing an overall prevalence rate of MMO of 8% (95%CI: 5-12%). When compared to non-MMO group, MMO was associated with lower age (MD = -5.91; 95%CI: -6.02: -5.20), greater risk of advanced glaucoma stage (LogOR=1.41; 95%CI: 0.72: 2.09), and lower mean deviation of the visual field (MD = -5.00; 95%CI: -7.01: -2.99). No significant difference was noted between both groups in terms of gender, axial length, or spherical equivalent. Three studies had good quality while seven had poor quality. MMO is a prevalent observation in glaucoma patients and is associated with patients' age and stage of the disease. However, the certainty of evidence remains very low.

Liraglutide intervention improves high-glucose-induced reactive gliosis of Müller cells and ECM dysregulation

Reactive gliosis of Müller cells plays an important role in the pathogenesis of diabetic retinopathy (DR). Liraglutide, a glucagon-like peptide-1 receptor (GLP-1R) agonist, has been shown to improve DR by inhibiting reactive gliosis. However, the mechanism of inhibition has yet to be elucidated. This study investigated the effects of liraglutide on Müller glia reactivity in the early stages of DR and the underlying mechanisms. Proteomics combined with bioinformatics analysis, HE staining, and immunofluorescence staining revealed ganglion cell loss, reactive gliosis of Müller cells, and extracellular matrix (ECM) imbalance in rats with early stages of DR. High glucose (HG) exposure up-regulated GFAP and TNF-α expression and down-regulated ITGB1 expression and FN1 content in extracellular fluid in rMC1 cells, thereby promoting reactive gliosis. GLP-1R knockdown and HG+DAPT inhibition experiments show that liraglutide balances ECM levels by inhibiting activation of the Notch1/Hes1 pathway and ameliorates high-glucose-induced Müller glia reactivity. Thus, the study provides new targets and ideas for improvement of DR in early stages.

Effect of Air Tamponade among Patients with Epiretinal Membranes and Intraretinal Cystoid Changes Undergoing Vitrectomy with Membrane Peeling - A Prospective Randomized Trial

BACKGROUND

The effect of air tamponade among patients undergoing vitrectomy with membrane peeling for removal of epiretinal membranes (ERM) is controversially discussed. The aim of the present study was to analyze differences in outcomes between air tamponade and balanced salt solution (BSS) in a study population with preoperative intraretinal cystoid changes.

PATIENTS AND METHODS

This randomized study included patients scheduled for pars plana vitrectomy with membrane peeling owing to ERM and intraretinal cystoid changes. Air tamponade or BSS at the end of surgery was applied according to preoperative randomization. Optical coherence tomography and best-corrected distance visual acuity (DCVA) measurements were performed before surgery, 5 days after surgery, and 3 months after surgery.

RESULTS

From 96 patients included, 85 eyes had full follow-up and could be included for analysis. Median improvement of DCVA was + 16 EDTRS letters (IQR: 8 to 22) among patients with BSS, while it was + 13 EDTRS letters (IQR: 8 to 17) among patients with air tamponade. There was a trend for better improvement of DCVA when BSS was left at the end of surgery, compared to air tamponade, but not reaching statistical significance.

CONCLUSIONS

There were no statistically significant differences concerning resorption of preoperative intraretinal cystoid changes, improvement of visual acuity, and final DVCA between air tamponade and BSS.

Morphological changes of foveal cysts as a predictor for visual response to anti-vascular endothelial growth factor treatments in diabetic macular edema : Degenerative cyst in DME

PURPOSE

To investigate morphological changes of intraretinal cyst in association with visual acuity following treatment for diabetic macular edema.

METHODS

This retrospective study enrolled 105 eyes from 105 treatment naïve patients with diabetic macular edema following anti-vascular endothelial growth factor injections. Best-corrected visual acuity (BCVA) and optical coherence tomography (OCT) data were obtained at baseline, 1, 3, 6, and 12 months. The width and height of the largest intraretinal cyst (IRC) at all different visits were measured and were correlated to final visual acuity by receiver operating characteristic curve. The exudative feature was defined by the presence of hard exudates. Multivariate logistic regression was used to select the independent predictor for visual outcomes.

RESULTS

Intraretinal cyst width but not the cyst height after treatment at 1 month independently predicted final visual loss of ten letters or more (multivariate P = 0.009). The optimal cutoff value was 196 um with a sensitivity of 0.889 and a specificity of 0.656. Eyes with large IRC width using this cutoff were consistently larger than those with small IRC width through 12 months (P = 0.008, Mann-Whitney U test). Small IRC width < 196 um at 1 month was more likely to coexist with exudative feature (P = 0.011, Fisher's exact test). Among baseline factors, large IRC width predicted IRC width ≥ 196 um at 1 month (multivariate P < 0.001).

CONCLUSION

Cyst morphology following intravitreal injection predicts visual outcomes. Eyes with IRC width ≥ 196 um after treatment at 1 month tends to be more degenerative, and less likely to coexist with exudative feature.

Multi-ancestry GWAS analysis identifies two novel loci associated with diabetic eye disease and highlights APOL1 as a high risk locus in patients with diabetic macular edema

Diabetic retinopathy (DR) is a common complication of diabetes. Approximately 20% of DR patients have diabetic macular edema (DME) characterized by fluid leakage into the retina. There is a genetic component to DR and DME risk, but few replicable loci. Because not all DR cases have DME, we focused on DME to increase power, and conducted a multi-ancestry GWAS to assess DME risk in a total of 1,502 DME patients and 5,603 non-DME controls in discovery and replication datasets. Two loci reached GWAS significance (p<5x10-8). The strongest association was rs2239785, (K150E) in APOL1. The second finding was rs10402468, which co-localized to PLVAP and ANKLE1 in vascular / endothelium tissues. We conducted multiple sensitivity analyses to establish that the associations were specific to DME status and did not reflect diabetes status or other diabetic complications. Here we report two novel loci for risk of DME which replicated in multiple clinical trial and biobank derived datasets. One of these loci, containing the gene APOL1, is a risk factor in African American DME and DKD patients, indicating that this locus plays a broader role in diabetic complications for multiple ancestries. Trial Registration: NCT00473330, NCT00473382, NCT03622580, NCT03622593, NCT04108156.

Unilateral retinitis pigmentosa associated with cystoid macular oedema

Retinitis pigmentosa (RP) is the most common inherited cause of blindness in the developed world, characterized by night blindness, reduced central vision and constricted visual field; however, unilateral RP is extremely rare. Macular complications such as cystoid macular oedema (CME), macular holes and vitreoretinal interface alterations, such as epiretinal membranes, have been reported in advanced stages. We describe a patient with unilateral RP presenting with CME, a rare occurrence.

Risk factors for microcystic macular oedema in glaucoma

BACKGROUND/AIMS

To identify clinical characteristics and factors associated with microcystic macular edema (MME) in patients with primary open-angle glaucoma (POAG).

METHODS

We included 315 POAG eyes between 2010 and 2019 with good-quality macular volume scans that had reliable visual fields (VF) available within 6 months in this observational retrospective cohort study. Eyes with retinal pathologies except for epiretinal membrane (ERM) were excluded. The inner nuclear layer was qualitatively assessed for the presence of MME. Global mean deviation (MD) and Visual Field Index (VFI) decay rates, superior and inferior MD rates and pointwise total deviation rates of change were estimated with linear regression. Logistic regression was performed to identify baseline factors associated with the presence of MME and to determine whether MME is associated with progressive VF loss.

RESULTS

25 out of 315 eyes (7.9%) demonstrated MME. The average (±SD) age and MD in eyes with and without MME was 57.2 (±8.7) versus 62.0 (±9.9) years (p=0.02) and -9.8 (±5.7) versus -4.9 (±5.3) dB (p<0.001), respectively. Worse global MD at baseline (p=0.001) and younger age (p=0.02) were associated with presence of MME. ERM was not associated with the presence of MME (p=0.84) in this cohort. MME was not associated with MD and VFI decay rates (p>0.49).

CONCLUSIONS

More severe glaucoma and younger age were associated with MME. MME was not associated with faster global VF decay in this cohort. MME may confound monitoring of glaucoma with full macular thickness.

An Overview towards Zebrafish Larvae as a Model for Ocular Diseases

Despite the obvious morphological differences in the visual system, zebrafish share a similar architecture and components of the same embryonic origin as humans. The zebrafish retina has the same layered structure and cell types with similar metabolic and phototransduction support as humans, and is functional 72 h after fertilization, allowing tests of visual function to be performed. The zebrafish genomic database supports genetic mapping studies as well as gene editing, both of which are useful in the ophthalmological field. It is possible to model ocular disorders in zebrafish, as well as inherited retinal diseases or congenital or acquired malformations. Several approaches allow the evaluation of local pathological processes derived from systemic disorders, such as chemical exposure to produce retinal hypoxia or glucose exposure to produce hyperglycemia, mimicking retinopathy of prematurity or diabetic retinopathy, respectively. The pathogenesis of ocular infections, autoimmune diseases, or aging can also be assessed in zebrafish larvae, and the preserved cellular and molecular immune mechanisms can be assessed. Finally, the zebrafish model for the study of the pathologies of the visual system complements certain deficiencies in experimental models of mammals since the regeneration of the zebrafish retina is a valuable tool for the study of degenerative processes and the discovery of new drugs and therapies.

Evaluation of acute effects of pulmonary involvement and hypoxia on retina and choroid in coronavirus disease 2019: An optic coherence tomography study

PURPOSE

We investigated the acute subclinical choroidal and retinal changes caused by Coronavirus Disease 2019 (COVID-19) in patients with and without pulmonary involvement, using spectral domain optic coherence tomography.

METHODS

This prospective case-control study included COVID-19 patients: 50 with pulmonary involvement and 118 with non-pulmonary involvement. All patients were examined 1 month after recovering from COVID-19. The changes were followed using optic coherence tomography parameters such as choroidal and macular thickness and retinal nerve fibre layer and ganglion cell complex measurements.

RESULTS

All choroidal thicknesses in the pulmonary involvement group were lower than in the non-pulmonary involvement group and the subfoveal choroidal thickness differed significantly (p=0.036). Although there were no significant differences between the central and average macular thicknesses in the two groups, they were slightly thicker in the pulmonary involvement group (p=0.152 and p=0.180, respectively). A significant decrease was detected in the pulmonary involvement group in all ganglion cell complex segments, except for the outer nasal inferior segment (p<0.05). In addition, a thinning tendency was observed in all retinal nerve fibre layer quadrants in the pulmonary involvement group compared to the non-pulmonary involvement group.

CONCLUSION

In COVID-19 patients with pulmonary involvement, subclinical choroidal and retinal changes may occur due to hypoxia and ischemia in the acute period. These patients may be predisposed to ischemic retinal and optic nerve diseases in the future. Therefore, COVID-19 patients with pulmonary involvement should be followed for ophthalmological diseases.

CRB1-Associated Retinal Dystrophies: Genetics, Clinical Characteristics, and Natural History

PURPOSE

To analyze the clinical characteristics, natural history, and genetics of CRB1-associated retinal dystrophies.

DESIGN

Multicenter international retrospective cohort study.

METHODS

Review of clinical notes, ophthalmic images, and genetic testing results of 104 patients (91 probands) with disease-causing CRB1 variants. Macular optical coherence tomography (OCT) parameters, visual function, fundus characteristics, and associations between variables were the main outcome measures.

RESULTS

The mean age of the cohort at the first visit was 19.8 ± 16.1 (median 15) years, with a mean follow-up of 9.6 ± 10 years. Based on history, imaging, and clinical examination, 26 individuals were diagnosed with retinitis pigmentosa (RP; 25%), 54 with early-onset severe retinal dystrophy / Leber congenital amaurosis (EOSRD/LCA; 52%), and 24 with macular dystrophy (MD; 23%). Severe visual impairment was most frequent after 40 years of age for patients with RP and after 20 years of age for EOSRD/LCA. Longitudinal analysis revealed a significant difference between baseline and follow-up best-corrected visual acuity in the 3 subcohorts. Macular thickness decreased in most patients with EOSRD/LCA and MD, whereas the majority of patients with RP had increased perifoveal thickness.

CONCLUSIONS

A subset of individuals with CRB1 variants present with mild, adult-onset RP. EOSRD/LCA phenotype was significantly associated with null variants, and 167_169 deletion was exclusively present in the MD cohort. The poor OCT lamination may have a degenerative component, as well as being congenital. Disease symmetry and reasonable window for intervention highlight CRB1 retinal dystrophies as a promising target for trials of novel therapeutics.

Characterizing macular edema in retinitis pigmentosa through a combined structural and microvascular optical coherence tomography investigation

The aim of the study was to characterize macular edema (ME) in retinitis pigmentosa (RP) by means of quantitative optical coherence tomography (OCT)-based imaging. The study was designed as observational, prospective case series, with 1-year follow-up. All RP patients underwent complete ophthalmologic assessment, including structural OCT, OCT angiography, and microperimetry (MP). The primary outcome was the characterization through quantitative OCT-based imaging of RP eyes complicated by ME. A total of 68 RP patients' eyes (68 patients) and 68 eyes of 68 healthy controls were recruited. Mean BCVA was 0.14 ± 0.17 LogMAR at baseline and 0.18 ± 0.23 LogMAR at 1-year follow-up (p > 0.05). Thirty-four eyes (17 patients; 25%) showed ME, with a mean ME duration of 8 ± 2 months. Most of the eyes were characterized by recurrent ME. The ME was mainly localized in the inner nuclear layer in all eyes. LogMAR BCVA was similar in all RP eyes, whether with or without ME, although those with ME were associated with higher vessel density values, as well as thicker choroidal layers, than those without ME. In conclusion, the inner retina is closely involved in the pathogenesis of ME. The impairment of retinal-choroidal exchanges and Müller cell disruption might be a major pathogenic factor leading to the onset of ME in RP.

The Role of Inflammation and Therapeutic Concepts in Diabetic Retinopathy-A Short Review

Diabetic retinopathy (DR) as a microangiopathy is the most common complication in patients with diabetes mellitus (DM) and remains the leading cause of blindness among adult population. DM in its complicated pathomechanism relates to chronic hyperglycemia, hypoinsulinemia, dyslipidemia and hypertension-all these components in molecular pathways maintain oxidative stress, formation of advanced glycation end-products, microvascular changes, inflammation, and retinal neurodegeneration as one of the key players in diabetes-associated retinal perturbations. In this current review, we discuss the natural history of DR with special emphasis on ongoing inflammation and the key role of vascular endothelial growth factor (VEGF). Additionally, we provide an overview of the principles of diabetic retinopathy treatments, i.e., in laser therapy, anti-VEGF and steroid options.

Electroacupuncture ameliorates inflammatory response induced by retinal ischemia-reperfusion injury and protects the retina through the DOR-BDNF/Trkb pathway

Objectives: Retinal ischemia-reperfusion injury (RIRI) is the common pathological basis of many ophthalmic diseases in the later stages, and inflammation is the primary damage mechanism of RIRI. Our study aimed to assess whether electroacupuncture (EA) has a protective effect against RIRI and to elucidate its related mechanisms. Methods: A high-intraocular pressure (HIOP) model was used to simulate RIRI in Wistar rats. EA was applied to the EA1 group [Jingming (BL1) + Shuigou (GV26)] and the EA2 group [Jingming (BL1) + Hegu (LI4)] respectively for 30 min starting immediately after the onset of reperfusion and repeated (30 min/time) at 12 h and then every 24 h until days 7 after reperfusion. The pathological changes in the retina were observed by H and E staining after HIOP. Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining was utilized to observe retinal cell apoptosis. The mRNA expression of IL1-β, TNF-α, IL-4, IL-10, δ-opioid receptor (DOR), brain-derived neurotrophic factor (BDNF), and tropomyosin-related kinase B (TrkB) in the retina was measured by quantitative real-time PCR. Results: HIOP caused structural disorders of the retina, decreased RGCs, and increased retinal cell apoptosis. At 1 and 3 days of RIRI, retinal apoptotic cells in the EA group were significantly reduced, while there was no distinct difference in the EA group compared with the HIOP group at 7 days of RIRI. Compared with that in the HIOP group, the expression of anti-inflammatory factors, DOR and TrkB was increased, and the expression of pro-inflammatory factors was decreased in the EA group. In contrast, HIOP had no appreciable effect on BDNF expression. Conclusion: EA at Jingming (BL1) and Shuigou (GV26) or at Jingming (BL1) and Hegu (LI4) may inhibit RIRI induced inflammation through activating the DOR-BDNF/TrkB pathway to protect the retina, especially the pair of Jingming (BL1) and Shuigou (GV26) has better inhibitory effects on inflammation.

Ocular Complications of Radiotherapy in Uveal Melanoma

Uveal melanoma is the most common primary malignant intraocular tumor in adults. Radiation therapy has replaced enucleation and is now the preferred treatment in most cases. Nonetheless, around 70% of patients develop radiation-related complications, some of which are vision-threatening. The objective of this review is to present the most important complications associated with radiotherapy in the treatment of uveal melanoma and their pathogenesis, incidence, risk factors, and available preventive and therapeutic measures. The most common complications are cataracts, with a reported incidence ranging from 4% to 69%, and radiation retinopathy, reported in 5-68% of cases. Radiation-related complications are responsible for approximately half of secondary enucleations, the leading cause being neovascular glaucoma. A poor visual outcome is mainly associated with the presence of radiation retinopathy and radiation optic neuropathy. Therapeutic options are available for the majority of complications with the notable exception of optic neuropathy. However, many studies report a final visual acuity of less than 20/200 in more than 60% of treated eyes. Reducing complication rates can be achieved by lowering the dose of radiation, with the use of eccentric, customized plaques and careful planning of the irradiation delivery in order to protect structures vital to vision and by associating radiation therapy with other methods with the aim of reducing tumor volume.

Retinal TRP channels: Cell-type-specific regulators of retinal homeostasis and multimodal integration

Transient receptor potential (TRP) channels are a widely expressed family of 28 evolutionarily conserved cationic ion channels that operate as primary detectors of chemical and physical stimuli and secondary effectors of metabotropic and ionotropic receptors. In vertebrates, the channels are grouped into six related families: TRPC, TRPV, TRPM, TRPA, TRPML, and TRPP. As sensory transducers, TRP channels are ubiquitously expressed across the body and the CNS, mediating critical functions in mechanosensation, nociception, chemosensing, thermosensing, and phototransduction. This article surveys current knowledge about the expression and function of the TRP family in vertebrate retinas, which, while dedicated to transduction and transmission of visual information, are highly susceptible to non-visual stimuli. Every retinal cell expresses multiple TRP subunits, with recent evidence establishing their critical roles in paradigmatic aspects of vertebrate vision that include TRPM1-dependent transduction of ON bipolar signaling, TRPC6/7-mediated ganglion cell phototransduction, TRP/TRPL phototransduction in Drosophila and TRPV4-dependent osmoregulation, mechanotransduction, and regulation of inner and outer blood-retina barriers. TRP channels tune light-dependent and independent functions of retinal circuits by modulating the intracellular concentration of the 2nd messenger calcium, with emerging evidence implicating specific subunits in the pathogenesis of debilitating diseases such as glaucoma, ocular trauma, diabetic retinopathy, and ischemia. Elucidation of TRP channel involvement in retinal biology will yield rewards in terms of fundamental understanding of vertebrate vision and therapeutic targeting to treat diseases caused by channel dysfunction or over-activation.

Diabetic Macular Edema: Current Understanding, Molecular Mechanisms and Therapeutic Implications

Diabetic retinopathy (DR), with increasing incidence, is the major cause of vision loss and blindness worldwide in working-age adults. Diabetic macular edema (DME) remains the main cause of vision impairment in diabetic patients, with its pathogenesis still not completely elucidated. Vascular endothelial growth factor (VEGF) plays a pivotal role in the pathogenesis of DR and DME. Currently, intravitreal injection of anti-VEGF agents remains as the first-line therapy in DME treatment due to the superior anatomic and functional outcomes. However, some patients do not respond satisfactorily to anti-VEGF injections. More than 30% patients still exist with persistent DME even after regular intravitreal injection for at least 4 injections within 24 weeks, suggesting other pathogenic factors, beyond VEGF, might contribute to the pathogenesis of DME. Recent advances showed nearly all the retinal cells are involved in DR and DME, including breakdown of blood-retinal barrier (BRB), drainage dysfunction of Müller glia and retinal pigment epithelium (RPE), involvement of inflammation, oxidative stress, and neurodegeneration, all complicating the pathogenesis of DME. The profound understanding of the changes in proteomics and metabolomics helps improve the elucidation of the pathogenesis of DR and DME and leads to the identification of novel targets, biomarkers and potential therapeutic strategies for DME treatment. The present review aimed to summarize the current understanding of DME, the involved molecular mechanisms, and the changes in proteomics and metabolomics, thus to propose the potential therapeutic recommendations for personalized treatment of DME.

Ocular Lymphatic and Glymphatic Systems: Implications for Retinal Health and Disease

Clearance of ocular fluid and metabolic waste is a critical function of the eye in health and disease. The eye has distinct fluid outflow pathways in both the anterior and posterior segments. Although the anterior outflow pathway is well characterized, little is known about posterior outflow routes. Recent studies suggest that lymphatic and glymphatic systems play an important role in the clearance of fluid and waste products from the posterior segment of the eye. The lymphatic system is a vascular network that runs parallel to the blood circulatory system. It plays an essential role in maintenance of fluid homeostasis and immune surveillance in the body. Recent studies have reported lymphatics in the cornea (under pathological conditions), ciliary body, choroid, and optic nerve meninges. The evidence of lymphatics in optic nerve meninges is, however, limited. An alternative lymphatic system termed the glymphatic system was recently discovered in the rodent eye and brain. This system is a glial cell-based perivascular network responsible for the clearance of interstitial fluid and metabolic waste. In this review, we will discuss our current knowledge of ocular lymphatic and glymphatic systems and their role in retinal degenerative diseases.

Inward rectifier potassium (Kir) channels in the retina: living our vision

Channel proteins are vital for conducting ions throughout the body and are especially relevant to retina physiology. Inward rectifier potassium (Kir) channels are a class of K+ channels responsible for maintaining membrane potential and extracellular K+ concentrations. Studies of the KCNJ gene (that encodes Kir protein) expression identified the presence of all of the subclasses (Kir 1-7) of Kir channels in the retina or retinal-pigmented epithelium (RPE). However, functional studies have established the involvement of the Kir4.1 homotetramer and Kir4.1/5.1 heterotetramer in Müller glial cells, Kir2.1 in bipolar cells, and Kir7.1 in the RPE cell physiology. Here, we propose the potential roles of Kir channels in the retina based on the physiological contributions to the brain, pancreatic, and cardiac tissue functions. There are several open questions regarding the expressed KCNJ genes in the retina and RPE. For example, why does not the Kir channel subtype gene expression correspond with protein expression? Catching up with multiomics or functional "omics" approaches might shed light on posttranscriptional changes that might influence Kir subunit mRNA translation within the retina that guides our vision.

Non-vasogenic cystoid maculopathies

Besides cystoid macular edema due to a blood-retinal barrier breakdown, another type of macular cystoid spaces referred to as non-vasogenic cystoid maculopathies (NVCM) may be detected on optical coherence tomography but not on fluorescein angiography. Various causes may disrupt retinal cell cohesion or impair retinal pigment epithelium (RPE) and Müller cell functions in the maintenance of retinal dehydration, resulting in cystoid spaces formation. Tractional causes include vitreomacular traction, epiretinal membranes and myopic foveoschisis. Surgical treatment does not always allow cystoid space resorption. In inherited retinal dystrophies, cystoid spaces may be part of the disease as in X-linked retinoschisis or enhanced S-cone syndrome, or occur occasionally as in bestrophinopathies, retinitis pigmentosa and allied diseases, congenital microphthalmia, choroideremia, gyrate atrophy and Bietti crystalline dystrophy. In macular telangiectasia type 2, cystoid spaces and cavitations do not depend on the fluid leakage from telangiectasia. Various causes affecting RPE function may result in NVCM such as chronic central serous chorioretinopathy and paraneoplastic syndromes. Non-exudative age macular degeneration may also be complicated by intraretinal cystoid spaces in the absence of fluorescein leakage. In these diseases, cystoid spaces occur in a context of retinal cell loss. Various causes of optic atrophy, including open-angle glaucoma, result in microcystoid spaces in the inner nuclear layer due to a retrograde transsynaptic degeneration. Lastly, drug toxicity may also induce cystoid maculopathy. Identifying NVCM on multimodal imaging, including fluorescein angiography if needed, allows guiding the diagnosis of the causative disease and choosing adequate treatment when available.

Association Between Fluid Volume in Inner Nuclear Layer and Visual Acuity in Diabetic Macular Edema

PURPOSE

In diabetic macular edema (DME), the correlation between visual acuity (VA) and central subfield thickness (CST) is weak. We hypothesize that fluid volume (FV) in the inner nuclear layer (INL) may correlate more strongly with VA.

DESIGN

Retrospective, cross-sectional study.

METHODS

One eye each of diabetic patients with DME was included. We measured intraretinal fluid volume that was detected by automated fluid detection algorithm on 3- × 3-mm optical coherence tomography angiogram volume scans. The detected fluid was subdivided into inner FV, bounded by the INL, and outer FV, the fluid between the outer border of INL to the ellipsoid zone.

RESULTS

We enrolled 125 patients with DME (60 women; mean age, 61 years). The mean detected inner FV was 0.013 mm³ in 109 eyes (87%). The mean detected outer FV was 0.042 mm³ in 124 eyes (99%). Univariate analysis demonstrated that the VA significantly correlated with the inner FV (P < .0001), whole macular FV (P = .010), and CST (P = .036). Multivariate analysis demonstrated that the inner FV was the only significant factor (β = -0.41, P = .004). These correlations were consistent when the treatment-naïve group (n = 33) and the eyes without previous laser treatments (n = 93) were analyzed separately. The area under the receiver operating characteristic curve of inner FV for VA of 20/32 or worse was significantly higher than that for CST (0.66 vs 0.54, P = .018).

CONCLUSIONS

The inner FV has a stronger association with VA than other OCT biomarkers in DME and may be more clinically useful.

The Mineralocorticoid receptor signal could be a new molecular target for the treatment of diabetic retinal complication

BACKGROUND

Activation of the mineralocorticoid receptor (MR) is involved in the pathophysiology of diabetic vascular complications. In recent years, it has been indicated that the MR expressed in retinal Müller cells plays an important role in regulating the potassium and water balance in the retina. Therefore, it has also been speculated that abnormal MR signaling contributes to edematous diseases of the retina.

RESEARCH DESIGN AND METHODS

We examined the effect of high-glucose conditions on MR protein and mRNA levels in human retinal Müller cells and changes in cell size in vitro. We also investigated MR transcriptional activity and signaling in high-glucose conditions.

RESULTS

The MR protein increased by 2.2-fold with high-glucose treatment. Additionally, high-glucose treatment induced Müller cell swelling. Aldosterone-induced MR transcriptional activity was enhanced in high-glucose conditions, resulting in the upregulation of αENaC, AQP4 and Kir4.1 mRNA. Treatment with an MR antagonist led to the suppression of aldosterone-induced cell swelling, MR transcriptional activity and upregulation of the target genes in high-glucose conditions.

CONCLUSIONS

High glucose induces Müller cell swelling through activation of MR signaling, which could be associated with aggravation of macular edema. Thus, Müller cell swelling and diabetic macular edema may represent a target for treatment with MR antagonists.

Regulations of Retinal Inflammation: Focusing on Müller Glia

Retinal inflammation underlies multiple prevalent retinal diseases. While microglia are one of the most studied cell types regarding retinal inflammation, growing evidence shows that Müller glia play critical roles in the regulation of retinal inflammation. Müller glia express various receptors for cytokines and release cytokines to regulate inflammation. Müller glia are part of the blood-retinal barrier and interact with microglia in the inflammatory responses. The unique metabolic features of Müller glia in the retina makes them vital for retinal homeostasis maintenance, regulating retinal inflammation by lipid metabolism, purine metabolism, iron metabolism, trophic factors, and antioxidants. miRNAs in Müller glia regulate inflammatory responses via different mechanisms and potentially regulate retinal regeneration. Novel therapies are explored targeting Müller glia for inflammatory retinal diseases treatment. Here we review new findings regarding the roles of Müller glia in retinal inflammation and discuss the related novel therapies for retinal diseases.

Associated factors and surgical outcomes of microcystoid macular edema and cone bouquet abnormalities in eyes with epiretinal membrane

PURPOSE

To investigate the associated features and the surgical outcomes in eyes with microcystoid macular edema (MME) and cone bouquet abnormalities (CBA) undergoing epiretinal membrane (ERM) peeling.

METHODS

Retrospective study including patients who underwent pars-plana vitrectomy for idiopathic ERM. Factors associated with MME and CBA at baseline and their regression were identified with logistic regression models. Postoperative visual acuity was evaluated with linear mixed models from baseline to 12 months. Risk factors for new or worsened macular edema (ME) were explored with a Cox regression model.

RESULTS

187 eyes were included; 30 eyes (16%) had MME; 53 eyes (28%) had CBA preoperatively. MME was associated with severe ERM stage (odds ratio (OR) [95% confidence interval (CI)] = 3.6[1.3-12.7], p=0.02); CBA inversely correlated with ectopic inner foveal layer thickness (OR [95% CI] = 0.97[0.97-0.99] for each 1-μm EIFL increase, p=0.006). Eyes with MME had worse visual acuity after ERM peeling (p=0.01) and were at risk of ME worsening (hazard ratio [95% CI] = 2.22[1.01-5.16], p=0.04). Older age was associated with MME persistence (OR [95%CI] = 2.46[1.06-6.82] for each 10-year increase, p=0.04). No significant associations were found for CBA.

CONCLUSION

While CBA had no prognostic consequences, MME was associated with suboptimal visual recovery and less efficient control of inflammation after surgery. Degeneration of Müller cells may have an alleged role, and further imaging and functional tests are warranted.

Aqueous Humor Biomarkers of Retinal Glial Cell Activation in Patients With or Without Age-Related Cataracts and With Different Stages of Diabetic Retinopathy

Purpose

To clarify the expression of biomarkers of retinal glial cell activation in the aqueous humor (AH) of patients with and without age-related cataracts (ARCs) at different stages of diabetic retinopathy (DR).

Methods

Patients were stratified by the presence of ARCs and then grouped by the presence of diabetes mellitus (DM), nonproliferative DR (NPDR), proliferative DR (PDR), and controls. Water channel aquaporin 1 (AQP1), water channel aquaporin 4 (AQP4), inwardly rectifying potassium channel 4.1 (Kir4.1), and glial fibrillary acidic protein (GFAP) were assayed in AH samples by ELISAs.

Results

We enrolled 82 patients. The AQP1 concentration was higher in AH from cataract control patients than in control patients without cataracts (P < 0.05). The APQ1 concentration was also higher in patients with DM, NPDR, and PDR than in controls (P < 0.05). The concentrations of AQP4 and GFAP were significantly increased in patients with NPDR and PDR (P < 0.05) but not in patients with DM. Kir4.1 concentration was significantly decreased in patients with NPDR and PDR (P < 0.05), but the decrease in patients with DM did not reach significance. There were no differences in AQP4, Kir4.1, and GFAP between patients with and without ARCs.

Conclusions

Increased AQP1 in AH may be a biomarker for ARCs in patients without diabetes and a biomarker for retinal glial cell activation in patients with diabetes without cataracts. AQP4, Kir4.1, and GFAP levels in AH suggested that retinal glial cell activation was affected by the progression of DR.

The role of inflammation and neurodegeneration in diabetic macular edema

The pathogenesis of diabetic macular edema (DME) is complex. Persistently high blood glucose activates multiple cellular pathways and induces inflammation, oxidation stress, and vascular dysfunction. Retinal ganglion cells, macroglial and microglial cells, endothelial cells, pericytes, and retinal pigment epithelium cells are involved. Neurodegeneration, characterized by dysfunction or apoptotic loss of retinal neurons, occurs early and independently from the vascular alterations. Despite the increasing knowledge on the pathways involved in DME, only limited therapeutic strategies are available. Besides antiangiogenic drugs and intravitreal corticosteroids, alternative therapeutic options tackling inflammation, oxidative stress, and neurodegeneration have been considered, but none of them has been currently approved.

Targeting Plasma Kallikrein With a Novel Bicyclic Peptide Inhibitor (THR-149) Reduces Retinal Thickening in a Diabetic Rat Model

Purpose

To investigate the effect of plasma kallikrein (PKal)-inhibition by THR-149 on preventing key pathologies associated with diabetic macular edema (DME) in a rat model.

Methods

Following streptozotocin-induced diabetes, THR-149 or its vehicle was administered in the rat via either a single intravitreal injection or three consecutive intravitreal injections (with a 1-week interval; both, 12.5 µg/eye). At 4 weeks post-diabetes, the effect of all groups was compared by histological analysis of Iba1-positive retinal inflammatory cells, inflammatory cytokines, vimentin-positive Müller cells, inwardly rectifying potassium and water homeostasis-related channels (Kir4.1 and AQP4, respectively), vascular leakage (fluorescein isothiocyanate-labeled bovine serum albumin), and retinal thickness.

Results

Single or repeated THR-149 injections resulted in reduced inflammation, as depicted by decreasing numbers and activation state of immune cells and IL-6 cytokine levels in the diabetic retina. The processes of reactive gliosis, vessel leakage, and retinal thickening were only significantly reduced after multiple THR-149 administrations. Individual retinal layer analysis showed that repeated THR-149 injections significantly decreased diabetes-induced thickening of the inner plexiform, inner nuclear, outer nuclear, and photoreceptor layers. At the glial-vascular interface, reduced Kir4.1-channel levels in the diabetic retina were restored to control non-diabetic levels in the presence of THR-149. In contrast, little or no effect of THR-149 was observed on the AQP4-channel levels.

Conclusions

These data demonstrate that repeated THR-149 administration reduces several DME-related key pathologies such as retinal thickening and neuropil disruption in the diabetic rat. These observations indicate that modulation of the PKal pathway using THR-149 has clinical potential to treat patients with DME.

OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY IN PATIENTS WITH RETINITIS PIGMENTOSA-ASSOCIATED CYSTOID MACULAR EDEMA

PURPOSE

To investigate the microstructure of cystoid macular edema (CME) in retinitis pigmentosa (RP) and the associated vascular changes using optical coherence tomography (OCT) angiography.

METHODS

In this retrospective study, we included 42 eyes of 21 patients with RP and age-similar normally sighted controls who underwent both OCT and optical coherence tomography angiography. Using OCT, spatial distribution of CME and the retinal layer, which CME located, was examined. Optical coherence tomography angiography images of the superficial capillary plexus and deep capillary plexus were obtained. Foveal and parafoveal flow densities in each layer and foveal avascular zone area were measured.

RESULTS

Of the 42 eyes with RP, 32 had CME. All CMEs were located in the inner nuclear layer and limited to the parafovea. The outer nuclear layer/ganglion cell layer was involved in 12 eyes (37.5%). Compared with RP without CME, RP with CME (RP-CME) did not show significant differences in flow density or extent of vascular disruption within the superficial capillary plexus, deep capillary plexus, or foveal avascular zone areas.

CONCLUSION

RP-CME was mostly located in the inner nuclear layer of the parafoveal macula, without vascular disruption in optical coherence tomography angiography. Our findings may support the hypothesis that the pathogenesis of RP with CME differs from retinal vascular CME triggered by compromised deep capillary plexus.

Of men and mice: Human X-linked retinoschisis and fidelity in mouse modeling

X-linked Retinoschisis (XLRS) is an early-onset transretinal dystrophy, often with a prominent macular component, that affects males and generally spares heterozygous females because of X-linked recessive inheritance. It results from loss-of-function RS1 gene mutations on the X-chromosome. XLRS causes bilateral reduced acuities from young age, and on clinical exam and by ocular coherence tomography (OCT) the neurosensory retina shows foveo-macular cystic schisis cavities in the outer plexiform (OPL) and inner nuclear layers (INL). XLRS manifests between infancy and school-age with variable phenotypic presentation and without reliable genotype-phenotype correlations. INL disorganization disrupts synaptic signal transmission from photoreceptors to ON-bipolar cells, and this reduces the electroretinogram (ERG) bipolar b-wave disproportionately to photoreceptor a-wave changes. RS1 gene expression is localized mainly to photoreceptors and INL bipolar neurons, and RS1 protein is thought to play a critical cell adhesion role during normal retinal development and later for maintenance of retinal structure. Several independent XLRS mouse models with mutant RS1 were created that recapitulate features of human XLRS disease, with OPL-INL schisis cavities, early onset and variable phenotype across mutant models, and reduced ERG b-wave to a-wave amplitude ratio. The faithful phenotype of the XLRS mouse has assisted in delineating the disease pathophysiology. Delivery to XLRS mouse retina of an AAV8-RS1 construct under control of the RS1 promoter restores the retinal structure and synaptic function (with increase of b-wave amplitude). It also ameliorates the schisis-induced inflammatory microglia phenotype toward a state of immune quiescence. The results imply that XLRS gene therapy could yield therapeutic benefit to preserve morphological and functional retina particularly when intervention is conducted at earlier ages before retinal degeneration becomes irreversible. A phase I/IIa single-center, open-label, three-dose-escalation clinical trial reported a suitable safety and tolerability profile of intravitreally administered AAV8-RS1 gene replacement therapy for XLRS participants. Dose-related ocular inflammation occurred after dosing, but this resolved with topical and oral corticosteroids. Systemic antibodies against AAV8 increased in dose-dependent fashion, but no antibodies were observed against the RS1 protein. Retinal cavities closed transiently in one participant. Technological innovations in methods of gene delivery and strategies to further reduce immune responses are expected to enhance the therapeutic efficacy of the vector and ultimate success of a gene therapy approach.

Evaluation of retinal inflammatory biomarkers after intravitreal steroid implant and Ranibizumab injection in diabetic macular edema

PURPOSE

To compare the efficacy of intravitreal (IV) ranibizumab (IVR) injection with IV dexamethasone implant (IVDEX) in treatment naive diabetic macular edema (DME) patients with inflammatory component.

MATERIALS AND METHODS

Treatment naive DME eyes with subfoveal neurosensorial detachment (SND) and hyperreflective spots (HRS) were treated either three loading doses of IVR (18 eyes) or one dose of IVDEX (19 eyes). Central macular thickness (CMT), height of SND, the number of HRSs scattered on the individual retinal layers and photoreceptor integrity were assessed using spectral domain- optical coherence tomography scans over 3-months follow-up.

RESULTS

The mean change in best-corrected visual acuity (BCVA) was -0.11 ± 0.08 logMAR in IVDEX group and -0.04 ± 0.06 logMAR in IVR group at 1-month (p = 0.011). IVDEX group showed statistically significant more increase in BCVA compared to those receiving IVR injections at 2-months (p = 0.004) and 3-months (p = 0.017) visits. Compared to baseline, the number of total HRSs and the number of HRSs at each individual inner retinal layer significantly decreased in both groups at all follow-up visits. However, IVDEX group showed more decrease in the total number of HRSs at 2- and 3-months (p < 0.001 at 2-months, and p = 0.006 at 3-months) and in the mean number of HRSs located at inner nuclear layer-outer plexiform layer level (p = 0.016 at 1-month, p < 0.001 at 2-months, and p < 0.001 at 3-months). After treatment, the number of HRSs on the outer nuclear layer showed some non-significant increase in both groups.

CONCLUSION

HRSs tended to migrate from inner retina to the outer retina in DME eyes by treatment. Dexamethasone seemed to be more effective option in such cases with inflammatory component.

Effect of Periocular Triamcinolone Acetonide on Prevention of Postsurgical Intraretinal Cystoid Changes after Vitrectomy with Membrane Peeling

BACKGROUND

Newly developed intraretinal cystoid changes after vitrectomy with membrane peeling for removal of epiretinal membranes have the potential to lead to worse postsurgical results compared to patients without. The aim of the present study was to evaluate the feasibility of additional periocular application of triamcinolone acetonide as a routine adjunct at the end of vitrectomy with membrane peeling, and to compare the presence of postsurgical intraretinal cystoid changes in the first 3 months after surgery among patients with idiopathic epiretinal membranes to a historical group of patients that did not receive triamcinolone acetonide.

PATIENTS AND METHODS

The medical records of 41 eyes of 41 patients that underwent 23 G or 25 G pars plana vitrectomy with membrane peeling for removal of epiretinal membranes and additional periocular triamcinolone acetonide application at the end of surgery were retrospectively reviewed. Optical coherence tomography findings during routine follow-ups at 3 - 5 days, 1 month, and 3 months and visual acuity at 3 months after surgery were evaluated and compared to preoperative findings. Furthermore, postsurgical intraocular pressure was assessed.

RESULTS

Periocular triamcinolone acetonide at the end of surgery was well tolerated among all patients. In total, 10% of patients had an increased intraocular pressure at least at one follow-up. Best-corrected visual acuity improved in 91% of patients with idiopathic epiretinal membranes with a mean improvement of + 3 ± 2 lines (Snellen) and was comparable to a historic group of patients (p = 0.307). Early transient macular edema could not be detected in any of the patients, while there were cases with this pathology in the historic group of patients, but neither occurrence of newly developed intraretinal cystoid changes nor macular thickness at 3 months after surgery were significantly different between patients with and without triamcinolone acetonide (p = 0.385 and p = 0.879).

CONCLUSIONS

Periocularly applied triamcinolone acetonide at the end of vitrectomy with membrane peeling was well tolerated and showed prevention of early transient macular edema but did not prevent the development of new postoperative intraretinal cystoid changes.

Evaluation of non-exudative microcystoid macular abnormalities secondary to retinal vein occlusion

Purpose

We aimed to investigate non-exudative microcystoid macular abnormalities for visual and anatomical outcome in patients with retinal vein occlusion (RVO) with and without glaucomatous optic neuropathy (GON).

Methods

Medical records of 124 eyes (105 patients) with RVO were reviewed and analyzed. Eyes demonstrating microcystoid macular abnormalities were divided into 2 groups, those with evidence of glaucoma (group A) and those without glaucoma (group B). Best-corrected visual acuity (BCVA), the prevalence and number of microcystoid macular abnormalities, and number of intravitreal anti-vascular endothelial growth factor (anti-VEGF) injections were compared at baseline and follow-up.

Results

Seventy-one out of 105 eyes (67.6%) with RVO displayed microcystoid macular abnormalities. Thirty-eight out of 71 eyes (53.5%) presented with concomitant glaucoma (group A), while the remaining 33 eyes (42.6%) had no history of glaucoma (group B). At the end of the follow-up period, mean BCVA was worse in group A versus group B (20/80 versus 20/40, respectively; p = .003). The mean number of anti-VEGF injections was 10.1 ± 9.2 in group A versus 5.9 ± 6.9 in group B (p = .03).

Conclusion

Eyes with RVO and concomitant glaucoma exhibited a significantly higher number of microcystoid macular abnormalities and worse BCVA versus eyes with RVO without glaucoma.

Quantitative analysis of retinal vessel density and thickness changes in diabetes mellitus evaluated using optical coherence tomography angiography: a cross-sectional study

Background

Diabetic retinopathy is the most common microvascular complication of diabetes; however, early changes in retinal microvessels are difficult to detect clinically, and a patient’s vision may have begun to deteriorate by the time a problem is identified. Optical coherence tomography angiography (OCTA) is an innovative tool for observing capillaries in vivo. The aim of this study was to analyze retinal vessel density and thickness changes in patients with diabetes.

Methods

This was a retrospective, observational cross-sectional study. Between August 2018 and February 2019, we collected OCTA data from healthy participants and diabetics from the First Affiliated Hospital of Harbin Medical University. Analyzed their retinal vessel density and thickness changes.

Results

A total of 97 diabetic patients with diabetes at different severity stages of diabetic retinopathy and 85 controls were involved in the experiment. Diabetic patients exhibited significantly lower retinal VD (particularly in the deep vascular complexes), thickening of the neurosensory retina, and thinning of the retinal pigment epithelium compared with controls. In the control group, nondiabetic retinopathy group and mild diabetic retinopathy group, superficial VD was significantly correlated with retinal thickness (r = 0.3886, P < 0.0001; r = 0.3276, P = 0.0019; r = 0.4614, P = 0.0024, respectively).

Conclusions

Patients with diabetes exhibit ischemia of the retinal capillaries and morphologic changes in vivo prior to vision loss. Therefore, OCTA may be useful as a quantitative method for the early detection of diabetic retinopathy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12886-021-01988-2.

VEGF Mediates Retinal Müller Cell Viability and Neuroprotection through BDNF in Diabetes

To investigate the mechanism of vascular endothelial growth factor (VEGF) and brain-derived neurotrophic factor (BDNF) in Müller cell (MC) viability and neuroprotection in diabetic retinopathy (DR), we examined the role of VEGF in MC viability and BDNF production, and the effect of BDNF on MC viability under diabetic conditions. Mouse primary MCs and cells of a rat MC line, rMC1, were used in investigating MC viability and BDNF production under diabetic conditions. VEGF-stimulated BDNF production was confirmed in mice. The mechanism of BDNF-mediated MC viability was examined using siRNA knockdown. Under diabetic conditions, recombinant VEGF (rVEGF) stimulated MC viability and BDNF production in a dose-dependent manner. rBDNF also supported MC viability in a dose-dependent manner. Targeting BDNF receptor tropomyosin receptor kinase B (TRK-B) with siRNA knockdown substantially downregulated the activated (phosphorylated) form of serine/threonine-specific protein kinase (AKT) and extracellular signal-regulated kinase (ERK), classical survival and proliferation mediators. Finally, the loss of MC viability in TrkB siRNA transfected cells under diabetic conditions was rescued by rBDNF. Our results provide direct evidence that VEGF is a positive regulator for BDNF production in diabetes for the first time. This information is essential for developing BDNF-mediated neuroprotection in DR and hypoxic retinal diseases, and for improving anti-VEGF treatment for these blood-retina barrier disorders, in which VEGF is a major therapeutic target for vascular abnormalities.

Defining inclusion criteria and endpoints for clinical trials: a prospective cross-sectional study in CRB1-associated retinal dystrophies

Purpose

To investigate the retinal structure and function in patients with CRB1‐associated retinal dystrophies (RD) and to explore potential clinical endpoints.

Methods

In this prospective cross‐sectional study, 22 patients with genetically confirmed CRB1‐RD (aged 6–74 years), and who had a decimal best‐corrected visual acuity (BCVA) ≥ 0.05 at the last visit, were studied clinically with ETDRS BCVA, corneal topography, spectral‐domain optical coherence tomography (SD‐OCT), fundus autofluorescence, Goldmann visual field (VF), microperimetry, full‐field electroretinography (ERG) and full‐field stimulus testing (FST). Ten patients were from a genetic isolate (GI).

Results

Patients had retinitis pigmentosa (n = 19; GI and non‐GI), cone‐rod dystrophy (n = 2; GI) or macular dystrophy (n = 1; non‐GI). Median age at first symptom onset was 3 years (range 0.8–49). Median decimal BCVA in the better and worse‐seeing eye was 0.18 (range 0.05–0.83) and 0.08 (range light perception‐0.72), respectively. Spectral‐domain optical coherence tomography (SD‐OCT) showed cystoid maculopathy in 8 subjects; inner retinal thickening (n = 20), a well‐preserved (para)foveal outer retina (n = 7) or severe (para)foveal outer retinal atrophy (n = 14). All retinal layers were discernible in 13/21 patients (62%), with mild to moderate laminar disorganization in the others. Nanophthalmos was observed in 8 patients (36%). Full‐field stimulus testing (FST) provided a subjective outcome measure for retinal sensitivity in eyes with (nearly) extinguished ERG amplitudes.

Conclusions

Despite the generally severe course of CRB1‐RDs, symptom onset and central visual function are variable, even at advanced ages. Phenotypes may vary within the same family. Imaging and functional studies in a prospective longitudinal setting should clarify which endpoints may be most appropriate in a clinical trial.

Prospects for the application of Müller glia and their derivatives in retinal regenerative therapies

Neural cell death is the main feature of all retinal degenerative disorders that lead to blindness. Despite therapeutic advances, progression of retinal disease cannot always be prevented, and once neuronal cell damage occurs, visual loss cannot be reversed. Recent research in the stem cell field, and the identification of Müller glia with stem cell characteristics in the human eye, have provided hope for the use of these cells in retinal therapies to restore vision. Müller glial cells, which are the major structural cells of the retina, play a very important role in retinal homeostasis during health and disease. They are responsible for the spontaneous retinal regeneration observed in zebrafish and lower vertebrates during early postnatal life, and despite the presence of Müller glia with stem cell characteristics in the adult mammalian retina, there is no evidence that they promote regeneration in humans. Like many other stem cells and neurons derived from pluripotent stem cells, Müller glia with stem cell potential do not differentiate into retinal neurons or integrate into the retina when transplanted into the vitreous of experimental animals with retinal degeneration. However, despite their lack of integration, grafted Müller glia have been shown to induce partial restoration of visual function in spontaneous or induced experimental models of photoreceptor or retinal ganglion cell damage. This improvement in visual function observed after Müller cell transplantation has been ascribed to the release of neuroprotective factors that promote the repair and survival of damaged neurons. Due to the development and availability of pluripotent stem cell lines for therapeutic uses, derivation of Müller cells from retinal organoids formed by iPSC and ESC has provided more realistic prospects for the application of these cells to retinal therapies. Several opportunities for research in the regenerative field have also been unlocked in recent years due to a better understanding of the genomic and proteomic profiles of the developing and regenerating retina in zebrafish, providing the basis for further studies of the human retina. In addition, the increased interest on the nature and function of cellular organelle release and the characterization of molecular components of exosomes released by Müller glia, may help us to design new approaches that could be applied to the development of more effective treatments for retinal degenerative diseases.

Anti-VEGF therapy prevents Müller intracellular edema by decreasing VEGF-A in diabetic retinopathy

Background

Although vascular endothelial growth factor A (VEGF-A) is known to play a key role in causing retinal edema, whether and how VEGF-A induces intracellular edema in the retina still remains unclear.

Methods

Sprague-Dawley rats were rendered diabetic with intraperitoneal injection of streptozotocin. Intravitreal injection of ranibizumab was performed 8 weeks after diabetes onset. rMC-1 cells (rat Müller cell line) were treated with glyoxal for 24 h with or without ranibizumab. The expression levels of inwardly rectifying K⁺ channel 4.1 (Kir4.1), aquaporin 4 (AQP4), Dystrophin 71 (Dp71), VEGF-A, glutamine synthetase (GS) and sodium-potassium-ATPase (Na⁺-K⁺-ATPase) were examined using Western blot. VEGF-A in the supernatant of the cell culture was detected with ELISA. The intracellular potassium and sodium levels were detected with specific indicators.

Results

Compared with normal control, protein expressions of Kir4.1 and AQP4 were down-regulated significantly in diabetic rat retinas, which were prevented by ranibizumab. The above changes were recapitulated in vitro. Similarly, the intracellular potassium level in glyoxal-treated rMC-1 cells was increased, while the intracellular sodium level and Na⁺-K⁺-ATPase protein level remained unchanged, compared with control. However, ranibizumab treatment decreased intracellular sodium, but not potassium.

Conclusion

Ranibizumab protected Müller cells from diabetic intracellular edema through the up-regulation of Kir4.1 and AQP4 by directly binding VEGF-A. It also caused a reduction in intracellular osmotic pressure.

Long-term multimodal imaging characterization of persistent retinal neovascularization using DL-alpha-aminoadipic acid in pigmented and white rabbits

PURPOSE

Intravitreal (IVT) injection of DL-alpha-aminoadipic acid (AAA) is a new animal model for retinal neovascularization (RNV) reported in rabbits. This study performs longitudinal multimodal imaging for up to 1 year to evaluate DL-AAA RNV in both New Zealand white (NZW) rabbits and Dutch-Belted pigmented (DBP) rabbits.

METHOD

Detailed characterization and quantification of this model were performed in these two strains in 32 eyes by optical coherence tomography (OCT), fundus photography, and fluorescein angiography (FA) for up to 16 weeks following DL-AAA administration in 32 eyes and up to 52 weeks in 5 eyes. H & E histology was also performed in these two strains 8 weeks after injection of DL-AAA.

RESULT

RNV was successfully generated using 50 μL 80 mM DL-AAA solution for DBP rabbits and 80 μL 80 mM DL-AAA for NZW rabbits. The incidence of persistent vascular leakage is 100% (15/15) for DBP rabbits and 70.6% (12/17) for NZW rabbits at 16 weeks. Complications with NZW rabbits ultimately decreased the efficiency in NZW rabbits to 58.8% (10/17) of NZW rabbits getting persistent (to 16 weeks) vascular leakage without ocular complications as compared with 100% (15/15) in DBP rabbits. Five eyes (2 DBP and 3 NZW) were selected from those demonstrating RNV at 16 weeks and were monitored for up to 52 weeks. All 5 demonstrated persistent RNV to 52 weeks. Quantification of the mean leakage area (MLA) in DBP rabbits is more accurate than in NZW rabbits since the reduced contrast between the leakage and background in NZW rabbits makes it more challenging to quantify.

CONCLUSION

DL-AAA can induce persistent and quantifiable RNV in both DBP and NZW rabbits. DBP rabbits have a higher success rate, lower required volume of DL-AAA, and more accurate method for quantification that could be more desirable.

MICROSTRUCTURAL CHANGES IN CYSTOID MACULAR EDEMA IN RETINITIS PIGMENTOSA AFTER INTRAVITREAL DEXAMETHASONE IMPLANT INJECTION

PURPOSE

To evaluate microstructural changes in cystoid macular edema in retinitis pigmentosa after intravitreal dexamethasone implant injection.

METHODS

In an extended cohort of a randomized trial of intravitreal dexamethasone implant for the management of retinitis pigmentosa-associated cystoid macular edema, microstructural changes during six months after the treatment were evaluated using spectral-domain optical coherence tomography.

RESULTS

Forty-two eyes were included, and all had cystoid space in the inner nuclear layer (INL) at baseline. No eyes showed subretinal fluid, and 28.6% showed hyperreflective foci. Among 38 eyes with cystoid space both in the INL and outer nuclear layer/Henle's layer, 13 (34.2%) showed complete resolution and 12 (31.6%) showed cystoid space only in the INL at 2 months after injection, whereas others showed persistent cystoid space in both layers. After complete resolution, cystoid space recurrence was earlier in the INL than in the outer nuclear layer/Henle's layer. Multivariable analysis showed that greater cystoid space area in the INL and outer nuclear layer/Henle's layer, presence of macular leakage, and longer intact external limiting membrane at baseline were associated with greater cystoid space area decrease after the treatment.

CONCLUSION

Resolution and recurrence pattern of retinitis pigmentosa-associated cystoid macular edema after dexamethasone treatment showed that the INL is the primary layer of cystic change, and this suggests its pathogenesis is most likely caused by Müller cell dysfunction.

Cell Surface Profiling of Retinal Müller Glial Cells Reveals Association to Immune Pathways after LPS Stimulation

Retinal Müller glial cells (RMG) are involved in virtually every retinal disease; however, the role of these glial cells in neuroinflammation is still poorly understood. Since cell surface proteins play a decisive role in immune system signaling pathways, this study aimed at characterizing the changes of the cell surface proteome of RMG after incubation with prototype immune system stimulant lipopolysaccharide (LPS). While mass spectrometric analysis of the human Müller glia cell line MIO-M1 revealed 507 cell surface proteins in total, with 18 proteins significantly more abundant after stimulation (ratio ≥ 2), the surfaceome of primary RMG comprised 1425 proteins, among them 79 proteins with significantly higher abundance in the stimulated state. Pathway analysis revealed notable association with immune system pathways such as “antigen presentation”, “immunoregulatory interactions between a lymphoid and a non-lymphoid cell” and “cell migration”. We could demonstrate a higher abundance of proteins that are usually ascribed to antigen-presenting cells (APCs) and function to interact with T-cells, suggesting that activated RMG might act as atypical APCs in the course of ocular neuroinflammation. Our data provide a detailed description of the unstimulated and stimulated RMG surfaceome and offer fundamental insights regarding the capacity of RMG to actively participate in neuroinflammation in the retina.

Anti-Inflammatory (M2) Response Is Induced by a sp2-Iminosugar Glycolipid Sulfoxide in Diabetic Retinopathy

Diabetic retinopathy (DR) is one of the most common complications of Diabetes Mellitus (DM) and is directly associated with inflammatory processes. Currently, neuro-inflammation is considered an early event in DR and proceeds via microglia polarization. A hallmark of DR is the presence of retinal reactive gliosis. Here we report the beneficial effect of (S_S,1R)-1-docecylsulfiny-5N,6O-oxomethylidenenojirimycin ((Ss)-DS-ONJ), a member of the sp²-iminosugar glycolipid (sp²-IGL) family, by decreasing iNOS and inflammasome activation in Bv.2 microglial cells exposed to pro-inflammatory stimuli. Moreover, pretreatment with (Ss)-DS-ONJ increased Heme-oxygenase (HO)-1 as well as interleukin 10 (IL10) expression in LPS-stimulated microglial cells, thereby promoting M2 (anti-inflammatory) response by the induction of Arginase-1. The results strongly suggest that this is the likely molecular mechanism involved in the anti-inflammatory effects of (S_S)-DS-ONJ in microglia. (S_S)-DS-ONJ further reduced gliosis in retinal explants from type 1 diabetic BB rats, which is consistent with the enhanced M2 response. In conclusion, targeting microglia polarization dynamics in M2 status by compounds with anti-inflammatory activities offers promising therapeutic interventions at early stages of DR.

Regulation of Endothelium-Reticulum-Stress-Mediated Apoptotic Cell Death by a Polymethoxylated Flavone, Nobiletin, Through the Inhibition of Nuclear Translocation of Glyceraldehyde 3-Phosphate Dehydrogenase in Retinal Müller Cells

In the early stages of diabetic retinopathy (DR), subtle biochemical and functional alterations occur in Müller cells, which are one of the components of the blood-retinal barrier (BRB). Müller cells are the principal glia of the retina and have shown a strong involvement in the maintenance of homeostasis and the development of retinal tissue. Their functional abnormalities and eventual loss have been correlated with a decrease in the tight junctions between endothelial cells and a consequent breakdown of the BRB, leading to the development of DR. We demonstrated that the endothelium reticulum (ER) triggers Müller cell death and that nuclear accumulation of glyceraldehyde 3-phosphate dehydrogenase is closely associated with ER-induced Müller cell death. In addition, induction of ER stress in Müller cells increased vascular endothelial growth factor expression but decreased pigment-epithelium-derived factor (PEDF) expression in Müller cells. We found that nobiletin, a polymethoxylated flavone from citrus explants, exerts protective action against ER-stress-induced Müller cell death. In addition, nobiletin was found to augment PEDF expression in Müller cells, which may lead to the protection of BRB integrity. These results suggest that nobiletin can be an attractive candidate for the protection of the BRB from breakdown in DR.