Ascorbic acid export from human donor lenses: Is the lens a source of ascorbic acid in the ocular humors?

In previous work, we have shown that the lens acts a reservoir of the antioxidant glutathione (GSH), capable of exporting this antioxidant into the ocular humors and potentially protecting the tissues of the eye that interface with these humors from oxidative stress. In this study, we have extended this work by examining whether the lens acts as a source of ascorbic acid (AsA) to maintain the high levels of AsA known to be present in the ocular humors either by the direct export of AsA into the humors and/or by functioning as a recycling site for AsA, via the direct uptake of oxidised ascorbate (DHA) from the humors, its regeneration to AsA in the lens and then its subsequent export back into the humors. To test this, human lenses of varying ages were cultured for 1 h under hypoxic conditions and AsA/DHA levels measured in the media and in the lens. Human lenses were also cultured in compartmentalised chambers to determine whether efflux of AsA/DHA occurs at the anterior or posterior surface. Immunohistochemistry was performed on human donor lenses and sections labelled with antibodies against GLUT1, a putative DHA uptake transporter. Vitreous humor was collected from patients undergoing vitrectomy who either had a natural clear lens, an artificial intraocular implant (IOL) or a cataractous lens, and AsA/DHA and GSH and oxidised GSH (GSSG) measured. We found that cultured human donor lenses released both AsA and DHA into the media. Culturing of lenses in a compartmentalised chamber revealed that AsA and DHA efflux occurs at both surfaces, with relatively equal amounts of AsA and DHA released from each surface. The posterior surface of the lens was shown to express the GLUT1 transporter. Analysis of vitreous samples from patients undergoing vitrectomy revealed that vitreous GSH and AsA levels were similar between the natural lens group, IOL and cataractous lens group. Taken together, while human donor lenses were shown to export AsA and DHA into the surrounding media, the amount of AsA and DHA released from donor lenses was low and not sufficient to sustain the high levels of total AsA normally present in the humors. This suggests that although the lens is not the main source for maintaining high levels of AsA in the ocular humors, the lens may help to support local AsA levels close to the lens.

INTERNAL DRAINAGE OF SUBRETINAL FLUID DURING CHANDELIER-ASSISTED SCLERAL BUCKLING.

PURPOSE: To describe the surgical technique of internal drainage of subretinal fluid as an adjunct to chandelier-assisted scleral buckling for the repair of rhegmatogenous retinal detachment. METHODS: The technique of internal drainage with a sharp needle or cannula through a trocar is described and shown in a Supplemental Digital Content 1 (see Video, http://links.lww.com/ICB/A87). RESULTS: Three patients (3 eyes) underwent scleral buckling for rhegmatogenous retinal detachment repair. Subretinal fluid was drained using the internal drainage approach in all cases. All three patients had successful reattachment of retina with improvement in visual function. No complications were reported related to vitreous loss, retinal incarceration, or redetachment following primary surgery. CONCLUSION: Internal drainage of subretinal fluid during chandelier-assisted scleral buckling is a useful technique that can be considered for repairing rhegmatogenous retinal detachment.

Better visual outcome associated with early vitrectomy in the management of endophthalmitis.

AIMS: To examine the role of early vitrectomy in the management of endophthalmitis from all causes. METHODS: Retrospective study of 290 consecutive subjects diagnosed with endophthalmitis at Auckland District Health Board between 1 January 2006 and 31 July 2019. Main outcome measure was visual acuity at 9-month follow-up and proportion of subjects with severe vision loss (≤20/200). RESULTS: Median age at presentation was 70.4 years and 151 subjects (52.1%) were women. Cataract surgery was the most common cause of endophthalmitis in 92 subjects (31.7%) followed by intravitreal injection in 57 (19.7%), endogenous endophthalmitis in 48 subjects (16.6%), non-surgical trauma in 42 subjects (14.5%), glaucoma surgery in 24 subjects (8.3%), vitrectomy in 22 subjects (7.6%) and corneal in 5 subjects (1.7%). Culture was positive in 136 (46.9%) with gram-positive organisms most common (76.5%). Early vitrectomy was performed in 82 subjects (28.3%). Median visual acuity at 9 months was 20/100 (IQR 20/30 to light perception), and severe vision loss occurred in 100 (43.5%). Retinal detachment occurred in 35 eyes (12.1%) and 26 eyes were enucleated. On multivariate analysis, younger age, poor presenting visual acuity and culture-positive endophthalmitis were associated with worse outcomes, and early vitrectomy was associated with better outcomes. CONCLUSIONS: Early vitrectomy (within 24 hours) is associated with better visual outcomes at 9 months, while younger age, poor presenting visual acuity and culture-positive endophthalmitis are associated with poorer visual acuity outcomes.

Chronic orbital inflammatory disease and optic neuropathy associated with long-term intranasal cocaine abuse: 2 cases and literature review.

Orbital inflammatory disease and secondary optic neuropathy is a rare but devastating complication of long-term intranasal cocaine abuse. We describe 2 patients with a history of intranasal cocaine consumption who presented with subacute onset of unilateral vision loss from optic neuropathy and limitation of abduction in the affected eye. Magnetic resonance imaging findings included an orbital mass in combination with absent nasal septum and partial destruction of the paranasal sinuses. Biopsies and histopathologic examination of the nasal cavity and the orbital mass revealed chronic inflammation. Both patients were treated with oral corticosteroids, ocular movements completely normalized but no improvement of visual acuity was noted. Intranasal cocaine abuse can cause orbital complications from chronic sinonasal inflammatory disease and these patients are at risk to develop optic neuropathy. Optic neuropathy may be caused by compression, infiltration, or ischaemia.

Correction: CD34 Promotes Pathological Epi-Retinal Neovascularization in a Mouse Model of Oxygen-Induced Retinopathy.

[This corrects the article DOI: 10.1371/journal.pone.0157902.].

Refractive outcomes after phacovitrectomy surgery.

PURPOSE: To evaluate the refractive accuracy of intraocular lens (IOL) power calculation after phacovitrectomy. SETTING: Eye Hospital Zonnestraal and Department of Ophthalmology Academic Medical Center, Amsterdam, the Netherlands. DESIGN: Retrospective comparative case series. METHODS: Refraction results 1 month after phacovitrectomy or phacoemulsification were compared with predicted refractions calculated using the IOLMaster 500 and the Haigis formula. Indications for vitrectomy were macular pucker, macular hole, vitreous floaters, vitreous hemorrhage, and vitreomacular traction. Enrolled eyes had an axial length (AL) between 20.13 mm and 29.43 mm. RESULTS: The phacovitrectomy group comprised 133 eyes (133 patients) and the phacoemulsification group, 132 eyes (132 patients). The refractive outcomes after phacovitrectomy (-0.06 diopter [D] ± 0.50 [SD]) and phacoemulsification (-0.08 ± 0.47 D) were comparable (P = .74). The final postoperative refraction was within ±1.00 D of the preoperative refractive target in 94.9% and 94.6% of phacovitrectomy cases and phacoemulsification cases, respectively. Subgroup analysis found no increased risk for refractive surprises after gas tamponade or in eyes with an AL of 26.00 mm or greater. CONCLUSIONS: Standard IOL power calculation used in regular phacoemulsification surgery was accurate in phacovitrectomy procedures in eyes with a wide range of AL and a wide range of vitrectomy indications. No tendency toward a myopic shift was found. FINANCIAL DISCLOSURE: Dr. Lapid-Gortzak is a clinical investigator for, speaker for, and consultant to Alcon Laboratories, Inc., Hanita Lenses, a speaker for Santen Pharmaceutical Co., and a consultant to Sanoculis and Orca Surgical. None of the authors has a financial or proprietary interest in any material or method mentioned.

CD34 Promotes Pathological Epi-Retinal Neovascularization in a Mouse Model of Oxygen-Induced Retinopathy.

The sialomucins CD34 and podocalyxin (PODXL) are anti-adhesive molecules expressed at the luminal membrane of endothelial cells of small blood vessels and facilitate vascular lumen formation in the developing mouse aorta. CD34 transcript and protein levels are increased during human angiogenesis, its expression is particularly enriched on endothelial tip cell filopodia and CD34 is a marker for tip cells in vitro. Here, we investigated whether CD34 merely marks endothelial tip cells or has a functional role in tip cells and angiogenesis. We assessed that silencing CD34 in human microvascular endothelial cells has little effect on endothelial cell migration or invasion, but has a significant effect on vascular-endothelial growth factor-induced angiogenic sprouting activity in vitro. In vivo, the absence of CD34 reduced the density of filopodia on retinal endothelial tip cells in neonatal mice, but did not influence the overall architecture of the retinal vascular network. In oxygen-induced retinopathy, Cd34-/- mice showed normal intra-retinal regenerative angiogenesis but the number of pathological epi-retinal neovascular tufts were reduced. We conclude that CD34 is not essential for developmental vascularization in the retina, but its expression promotes the formation of pathological, invasive vessels during neovascularization.

NF-κB-inducing kinase is a key regulator of inflammation-induced and tumour-associated angiogenesis.

Angiogenesis is essential during development and in pathological conditions such as chronic inflammation and cancer progression. Inhibition of angiogenesis by targeting vascular endothelial growth factor (VEGF) blocks disease progression, but most patients eventually develop resistance which may result from compensatory signalling pathways. In endothelial cells (ECs), expression of the pro-angiogenic chemokine CXCL12 is regulated by non-canonical nuclear factor (NF)-κB signalling. Here, we report that NF-κB-inducing kinase (NIK) and subsequent non-canonical NF-κB signalling regulate both inflammation-induced and tumour-associated angiogenesis. NIK is highly expressed in endothelial cells (ECs) in tumour tissues and inflamed rheumatoid arthritis synovial tissue. Furthermore, non-canonical NF-κB signalling in human microvascular ECs significantly enhanced vascular tube formation, which was completely blocked by siRNA targeting NIK. Interestingly, Nik(-/-) mice exhibited normal angiogenesis during development and unaltered TNFα- or VEGF-induced angiogenic responses, whereas angiogenesis induced by non-canonical NF-κB stimuli was significantly reduced. In addition, angiogenesis in experimental arthritis and a murine tumour model was severely impaired in these mice. These studies provide evidence for a role of non-canonical NF-κB signalling in pathological angiogenesis, and identify NIK as a potential therapeutic target in chronic inflammatory diseases and tumour neoangiogenesis.

Endothelial tip cells in ocular angiogenesis: potential target for anti-angiogenesis therapy.

Endothelial tip cells are leading cells at the tips of vascular sprouts coordinating multiple processes during angiogenesis. In the developing retina, tip cells play a tightly controlled, timely role in angiogenesis. In contrast, excessive numbers of tip cells are a characteristic of the chaotic pathological blood vessels in proliferative retinopathies. Tip cells control adjacent endothelial cells in a hierarchical manner to form the stalk of the sprouting vessel, using, among others, the VEGF-DLL-Notch signaling pathway, and recruit pericytes. Tip cells are guided toward avascular areas by signals from the local extracellular matrix that are released by cells from the neuroretina such as astrocytes. Recently, tip cells were identified in endothelial cell cultures, enabling identification of novel molecular markers and mechanisms involved in tip cell biology. These mechanisms are relevant for understanding proliferative retinopathies. Agents that primarily target tip cells can block pathological angiogenesis in the retina efficiently and safely without adverse effects. A striking example is platelet-derived growth factor, which was recently shown to be an efficacious additional target in the treatment of retinal neovascularization. Here we discuss these and other tip cell-based strategies with respect to their potential to treat patients with ocular diseases dominated by neovascularization.

CD34 marks angiogenic tip cells in human vascular endothelial cell cultures.

The functional shift of quiescent endothelial cells into tip cells that migrate and stalk cells that proliferate is a key event during sprouting angiogenesis. We previously showed that the sialomucin CD34 is expressed in a small subset of cultured endothelial cells and that these cells extend filopodia: a hallmark of tip cells in vivo. In the present study, we characterized endothelial cells expressing CD34 in endothelial monolayers in vitro. We found that CD34-positive human umbilical vein endothelial cells show low proliferation activity and increased mRNA expression of all known tip cell markers, as compared to CD34-negative cells. Genome-wide mRNA profiling analysis of CD34-positive endothelial cells demonstrated enrichment for biological functions related to angiogenesis and migration, whereas CD34-negative cells were enriched for functions related to proliferation. In addition, we found an increase or decrease of CD34-positive cells in vitro upon exposure to stimuli that enhance or limit the number of tip cells in vivo, respectively. Our findings suggest cells with virtually all known properties of tip cells are present in vascular endothelial cell cultures and that they can be isolated based on expression of CD34. This novel strategy may open alternative avenues for future studies of molecular processes and functions in tip cells in angiogenesis.

Mechanisms of ocular angiogenesis and its molecular mediators.

Angiogenesis is defined as the formation of new blood vessels from the existing vasculature. It is a highly coordinated process occurring during development of the retinal vasculature, ocular wound healing, and in pathological conditions. Complex interactions are involved between non-vascular and microvascular cells, such as endothelial cells and pericytes, via several angiogenic growth factors and inhibitors. Of these growth factors, vascular endothelial growth factor (VEGF) has emerged as the single most important causal agent of angiogenesis in health and disease in the eye. During the angiogenic process, endothelial cells shift from a homogeneous quiescent population into a population of heterogeneous phenotypes, each with a distinct cellular fate. So far, three angiogenic specialized phenotypes have been identified: (1) 'tip cells', which pick up guidance signals and migrate through the extracellular matrix; (2) 'stalk cells', which proliferate, form junctions, produce extracellular matrix, and form a lumen, and (3) 'phalanx cells', which do not proliferate, but align and form a smooth monolayer. Eventually, a robust mature new blood vessel is formed which is capable of supplying blood and oxygen to tissues. Pathological angiogenesis is a key component of several irreversible causes of blindness. In most of these conditions, angiogenesis is part of a wound healing response culminating, via an angiofibrotic switch, in fibrosis and scar formation which leads to blindness. Currently, VEGF-A antagonists are standard care in the treatment of exudative age-related macular degeneration, and have been found to be a valuable additional treatment strategy in several other vascular retinal diseases.

Rubella virus-associated uveitis in a nonvaccinated child.

PURPOSE: To report presumed Fuchs heterochromic uveitis (FHU) associated with Rubella virus (RV)-specific intraocular antibody production in a child who was not vaccinated against rubella. DESIGN: Observational case report. METHODS: We examined a 13-year-old boy with chronic anterior uveitis complicated by mature cataract. Two aqueous humor (AH) samples taken with an interval of four weeks were analyzed for intraocular antibody production against RV by calculation of the Goldmann-Witmer coefficient. RESULTS: The patient showed all the clinical signs for FHU: iris atrophy, stellate keratic precipitates, and cataract. Analysis of the AH demonstrated intraocular antibody production against RV in two sequential samples. CONCLUSIONS: The data show that RV-associated uveitis can already present during childhood. Moreover, this finding suggests that nonvaccinated children may be at risk to develop uveitis after RV infection.