Reactive microglia and infiltrating peripheral monocytes have been implicated in many neurodegenerative diseases of the retina and CNS. However, their specific contribution in retinal degeneration remains unclear. We recently showed that peripheral monocytes that infiltrate the retina after ocular injury in mice become permanently engrafted into the tissue, establishing a proinflammatory phenotype that promotes neurodegeneration. In this study, we show that microglia regulate the process of neuroglia remodeling during ocular injury, and their depletion results in marked upregulation of inflammatory markers, such as , , and in the retina, and abnormal engraftment of peripheral CCR2 CX3CR1 monocytes into the retina, which is associated with increased retinal ganglion cell loss, retinal nerve fiber layer thinning, and pigmentation onto the retinal surface. Furthermore, we show that other types of ocular injuries, such as penetrating corneal trauma and ocular hypertension also cause similar changes. However, optic nerve crush injury-mediated retinal ganglion cell loss evokes neither peripheral monocyte response in the retina nor pigmentation, although peripheral CX3CR1 and CCR2 monocytes infiltrate the optic nerve injury site and remain present for months. Our study suggests that microglia are key regulators of peripheral monocyte infiltration and retinal pigment epithelium migration, and their depletion results in abnormal neuroglia remodeling that exacerbates neuroretinal tissue damage. This mechanism of retinal damage through neuroglia remodeling may be clinically important for the treatment of patients with ocular injuries, including surgical traumas.
The Wnt signaling pathway plays a pivotal role in vascular morphogenesis in various organs including the eye. Wnt ligands and receptors are key regulators of ocular angiogenesis both during the eye development and in vascular eye diseases. Wnt signaling participates in regulating multiple vascular beds in the eye including regression of the hyaloid vessels, and development of structured layers of vasculature in the retina. Loss-of-function mutations in Wnt signaling components cause rare genetic eye diseases in humans such as Norrie disease, and familial exudative vitreoretinopathy (FEVR) with defective ocular vasculature. On the other hand, experimental studies in more prevalent vascular eye diseases, such as wet age-related macular degeneration (AMD), diabetic retinopathy (DR), retinopathy of prematurity (ROP), and corneal neovascularization, suggest that aberrantly increased Wnt signaling is one of the causations for pathological ocular neovascularization, indicating the potential of modulating Wnt signaling to ameliorate pathological angiogenesis in eye diseases. This review recapitulates the key roles of the Wnt signaling pathway during ocular vascular development and in vascular eye diseases, and pharmaceutical approaches targeting the Wnt signaling as potential treatment options.
Despite advances in therapy for rheumatic diseases, hydroxychloroquine remains almost universally recommended for the treatment of systemic lupus erythematosus (SLE), and is often used in the management of other rheumatic diseases such as rheumatoid arthritis (RA). However, the major dose-limiting toxicity of hydroxychloroquine is retinopathy that can lead to loss of vision. New highly sensitive screening methods can identify early stages of retinopathy, and studies that include these modalities have indicated a substantially higher prevalence of hydroxychloroquine retinopathy than was previously recognized, resulting in revisions to ophthalmology guidelines and the recommendation of a low dose of hydroxychloroquine for many patients. However, the efficacy of low-dose hydroxychloroquine for treating SLE and other rheumatic diseases is unknown. Further studies are required to establish the effectiveness and retinal safety of the latest hydroxychloroquine treatment recommendations.
Previous studies have demonstrated that ocular injury can lead to prompt infiltration of bone-marrow-derived peripheral monocytes into the retina. However, the ability of these cells to integrate into the tissue and become microglia has not been investigated. Here we show that such peripheral monocytes that infiltrate into the retina after ocular injury engraft permanently, migrate to the three distinct microglia strata, and adopt a microglia-like morphology. In the absence of ocular injury, peripheral monocytes that repopulate the retina after depletion with colony-stimulating factor 1 receptor (CSF1R) inhibitor remain sensitive to CSF1R inhibition and can be redepleted. Strikingly, consequent to ocular injury, the engrafted peripheral monocytes are resistant to depletion by CSF1R inhibitor and likely express low CSF1R. Moreover, these engrafted monocytes remain proinflammatory, expressing high levels of MHC-II, IL-1β, and TNF-α over the long term. The observed permanent neuroglia remodeling after injury constitutes a major immunological change that may contribute to progressive retinal degeneration. These findings may also be relevant to other degenerative conditions of the retina and the central nervous system.
BACKGROUND: To evaluate changes in image sharpness across ultrawide field (UWF) images and the effect of phase-plate adjustment on image contrast and extent of visible retinal area (VRA). METHODS: This was a single site evaluation of 200° UWF images acquired with phase-plate adjustment (California, Optos, plc) and without (200TX, Optos, plc). Images were acquired using standardized protocol. VRA was manually outlined on each image and quantified using customized software. Mean image sharpness was evaluated using an automated method within the full VRA of each image and within the peripheral region of the VRA. The VRA and image sharpness were evaluated and compared between the two devices. RESULTS: Twenty eyes of 10 healthy volunteers were evaluated. Devices with and without phase-plate adjustment produced a similar extent of VRA. Eye steering increased VRA in devices with and without phase-plate adjustment by 39.3% and 34.3%, respectively. Regardless of gaze direction, mean sharpness of the full VRA was reduced in peripheral area with or without phase-plate adjustment. Compared to images without phase-plate adjustment, use of phase-plate adjustment reduced the loss of peripheral image sharpness in all fields (-4.2 to -26.0%; p < 0.001 all fields). The sharpness of the peripheral area for on-axis images was 61.5% higher with phase-plate adjustment. CONCLUSIONS: The use of phase-plate adjustment does not alter the extent of VRA. However, for on-axis images the loss of sharpness in the periphery is 4.5-fold less with phase-plate adjustment, potentially reducing the need to steer images and improving lesion detection in these areas.
PURPOSE: To investigate systemic and ocular determinants of peripapillary retinal nerve fiber layer thickness (pRNFLT) in the European population. DESIGN: Cross-sectional meta-analysis. PARTICIPANTS: A total of 16 084 European adults from 8 cohort studies (mean age range, 56.9±12.3-82.1±4.2 years) of the European Eye Epidemiology (E3) consortium. METHODS: We examined associations with pRNFLT measured by spectral-domain OCT in each study using multivariable linear regression and pooled results using random effects meta-analysis. MAIN OUTCOME MEASURES: Determinants of pRNFLT. RESULTS: Mean pRNFLT ranged from 86.8±21.4 μm in the Rotterdam Study I to 104.7±12.5 μm in the Rotterdam Study III. We found the following factors to be associated with reduced pRNFLT: Older age (β = -0.38 μm/year; 95% confidence interval [CI], -0.57 to -0.18), higher intraocular pressure (IOP) (β = -0.36 μm/mmHg; 95% CI, -0.56 to -0.15), visual impairment (β = -5.50 μm; 95% CI, -9.37 to -1.64), and history of systemic hypertension (β = -0.54 μm; 95% CI, -1.01 to -0.07) and stroke (β = -1.94 μm; 95% CI, -3.17 to -0.72). A suggestive, albeit nonsignificant, association was observed for dementia (β = -3.11 μm; 95% CI, -6.22 to 0.01). Higher pRNFLT was associated with more hyperopic spherical equivalent (β = 1.39 μm/diopter; 95% CI, 1.19-1.59) and smoking (β = 1.53 μm; 95% CI, 1.00-2.06 for current smokers compared with never-smokers). CONCLUSIONS: In addition to previously described determinants such as age and refraction, we found that systemic vascular and neurovascular diseases were associated with reduced pRNFLT. These may be of clinical relevance, especially in glaucoma monitoring of patients with newly occurring vascular comorbidities.
Endogenous vascular endothelial growth factor (VEGF-A) can protect retinal ganglion cells (RGC) from stress-induced cell death in ocular hypertensive glaucoma. To exploit the neuroprotective function of VEGF-A for therapeutic application in ocular disorders such as glaucoma while minimizing unwanted vascular side effects, we engineered two novel VEGF variants, eVEGF-38 and eVEGF-53. These variants of the diffusible VEGF-A isoform VEGF121 are expressed as dimeric concatamers and remain tethered to the cell membrane, thus restricting the effects of the engineered VEGF to the cells expressing the protein. For comparison, we tested a Myc-tagged version of VEGF189, an isoform that binds tightly to the extracellular matrix and heparan sulfate proteoglycans at the cell surface, supporting only autocrine and localized juxtacrine signaling. In human retinal endothelial cells (hREC), expression of eVEGF-38, eVEGF-53, or VEGF189 increased VEGFR2 phosphorylation without increasing expression of pro-inflammatory markers, relative to VEGF165 protein and vector controls. AAV2-mediated transduction of eVEGF-38, eVEGF-53, or VEGF189 into primary mouse RGC promoted synaptogenesis and increased the average total length of neurites and axons per RGC by ~ 12-fold, an increase that was mediated by VEGFR2 and PI3K/AKT signaling. Expression of eVEGF-38 in primary RGC enhanced expression of genes associated with neuritogenesis, axon outgrowth, axon guidance, and cell survival. Transduction of primary RGC with any of the membrane-associated VEGF constructs increased survival both under normal culture conditions and in the presence of the cytotoxic chemicals HO (via VEGFR2/PI3K/AKT signaling) and N-methyl-D-aspartate (via reduced Ca influx). Moreover, RGC number was increased in mouse embryonic stem cell-derived retinal organoid cultures transduced with the eVEGF-53 construct. The novel, engineered VEGF variants eVEGF-38 and eVEGF-53 show promise as potential therapeutics for retinal RGC neuroprotection when delivered using a gene therapy approach.
Retinopathy of prematurity (ROP) is characterized by abnormal retinal neovascularization in response to vessel loss. Platelets regulate angiogenesis and may influence ROP progression. In preterm infants, we assessed ROP and correlated with longitudinal postnatal platelet counts (n = 202). Any episode of thrombocytopenia (<100 × 109/l) at ≥30 weeks postmenstrual age (at onset of ROP) was independently associated with severe ROP, requiring treatment. Infants with severe ROP also had a lower weekly median platelet count compared with infants with less severe ROP. In a mouse oxygen-induced retinopathy model of ROP, platelet counts were lower at P17 (peak neovascularization) versus controls. Platelet transfusions at P15 and P16 suppressed neovascularization, and platelet depletion increased neovascularization. Platelet transfusion decreased retinal of vascular endothelial growth factor A (VEGFA) mRNA and protein expression; platelet depletion increased retinal VEGFA mRNA and protein expression. Resting platelets with intact granules reduced neovascularization, while thrombin-activated degranulated platelets did not. These data suggest that platelet releasate has a local antiangiogenic effect on endothelial cells to exert a downstream suppression of VEGFA in neural retina. Low platelet counts during the neovascularization phase in ROP is significantly associated with the development of severe ROP in preterm infants. In a murine model of retinopathy, platelet transfusion during the period of neovascularization suppressed retinopathy.
PURPOSE: To describe a case of a central retinal vein occlusion in a young patient with a history of eosinophilic pneumonia. METHODS: A retrospective case report of a 45-year-old woman with acute painless vision loss for 9 days after multiple episodes of eosinophilic pneumonia and thalamic stroke. Fluorescein angiography, spectral domain optical coherence tomography, and clinical examination were performed. She was then treated with intravitreal bevacizumab and pan-retinal photocoagulations. RESULTS: Retinal examination revealed tortuosity and dilatation of all branches of the central retinal vein and flame-shaped hemorrhages in all four quadrants of the right eye associated with cystoid macular edema, optic disc edema, and cotton wool spots. The left eye had mild venous dilatation and tortuosity with a few dot retinal hemorrhages in the far temporal periphery. The cystoid macular edema resolved after one intravitreal injection of bevacizumab and remained resolved at the most recent follow-up. Fluorescein angiography at the most recent follow-up revealed vasculitis in the far periphery of the nontreated eye. CONCLUSION: Central retinal vein occlusion in young patients is a rare condition often presenting as a manifestation of an underlying inflammatory or hematological disorder. Combined anti-vascular endothelial growth factor treatment and pan-retinal photocoagulation may have resolved the associated cystoid macular edema in this case, although continued observation is necessary.
Buskin A, Zhu L, Chichagova V, Basu B, Mozaffari-Jovin S, Dolan D, Droop A, Collin J, Bronstein R, Mehrotra S, Farkas M, Hilgen G, White K, Pan K-T, Treumann A, Hallam D, Bialas K, Chung G, Mellough C, Ding Y, Krasnogor N, Przyborski S, Zwolinski S, Al-Aama J, Alharthi S, Xu Y, Wheway G, Szymanska K, McKibbin M, Inglehearn CF, Elliott DJ, Lindsay S, Ali RR, Steel DH, Armstrong L, Sernagor E, Urlaub H, Pierce E, Lührmann R, Grellscheid S-N, Johnson CA, Lako M. Disrupted alternative splicing for genes implicated in splicing and ciliogenesis causes PRPF31 retinitis pigmentosa. Nat Commun 2018;9(1):4234.Abstract
Mutations in pre-mRNA processing factors (PRPFs) cause autosomal-dominant retinitis pigmentosa (RP), but it is unclear why mutations in ubiquitously expressed genes cause non-syndromic retinal disease. Here, we generate transcriptome profiles from RP11 (PRPF31-mutated) patient-derived retinal organoids and retinal pigment epithelium (RPE), as well as Prpf31 mouse tissues, which revealed that disrupted alternative splicing occurred for specific splicing programmes. Mis-splicing of genes encoding pre-mRNA splicing proteins was limited to patient-specific retinal cells and Prpf31 mouse retinae and RPE. Mis-splicing of genes implicated in ciliogenesis and cellular adhesion was associated with severe RPE defects that include disrupted apical - basal polarity, reduced trans-epithelial resistance and phagocytic capacity, and decreased cilia length and incidence. Disrupted cilia morphology also occurred in patient-derived photoreceptors, associated with progressive degeneration and cellular stress. In situ gene editing of a pathogenic mutation rescued protein expression and key cellular phenotypes in RPE and photoreceptors, providing proof of concept for future therapeutic strategies.