Christian van Oterendorp

Treatment of optic neuritis with erythropoietin (TONE): a randomised, double-blind, placebo-controlled trial—study protocol

Introduction Optic neuritis leads to degeneration of retinal ganglion cells whose axons form the optic nerve. The standard treatment is a methylprednisolone pulse therapy. This treatment slightly shortens the time of recovery but does not prevent neurodegeneration and persistent visual impairment. In a phase II trial performed in preparation of this study, we have shown that erythropoietin protects global retinal nerve fibre layer thickness (RNFLT-G) in acute optic neuritis; however, the preparatory trial was not powered to show effects on visual function. Methods and analysis Treatment of Optic Neuritis with Erythropoietin (TONE) is a national, randomised, double-blind, placebo-controlled, multicentre trial with two parallel arms. The primary objective is to determine the efficacy of erythropoietin compared to placebo given add-on to methylprednisolone as assessed by measurements of RNFLT-G and low-contrast visual acuity in the affected eye 6 months after randomisation. Inclusion criteria are a first episode of optic neuritis with decreased visual acuity to ≤0.5 (decimal system) and an onset of symptoms within 10 days prior to inclusion. The most important exclusion criteria are history of optic neuritis or multiple sclerosis or any ocular disease (affected or non-affected eye), significant hyperopia, myopia or astigmatism, elevated blood pressure, thrombotic events or malignancy. After randomisation, patients either receive 33 000 international units human recombinant erythropoietin intravenously for 3 consecutive days or placebo (0.9% saline) administered intravenously. With an estimated power of 80%, the calculated sample size is 100 patients. The trial started in September 2014 with a planned recruitment period of 30 months. Ethics and dissemination TONE has been approved by the Central Ethics Commission in Freiburg (194/14) and the German Federal Institute for Drugs and Medical Devices (61-3910-4039831). It complies with the Declaration of Helsinki, local laws and ICH-GCP. Trial registration number NCT01962571.

Retrograde Neurotrophic Signaling in Rat Retinal Ganglion Cells Is Transmitted via the ERK5 but Not the ERK1/2 Pathway

PURPOSE Neurotrophic deprivation is considered an important event in glaucomatous retinal ganglion cell (RGC) death. However, the mitogen-activated protein kinase (MAPK) pathway transmitting axonal neurotrophic signals in RGC has not been identified. We investigated the involvement of ERK5 and ERK1/2 in retrograde axonal neurotrophic signaling in rats. METHODS Adult Sprague-Dawley rats were used. Retinal immunostaining for ERK5 and MEK5 was performed. Levels of total and phosphorylated ERK5 and ERK1/2 were analyzed in retinal lysate by quantitative Western blotting. The effects of age, brain-derived neurotrophic factor (BDNF) stimulation at RGC soma (intravitreal injection) or axon ending (superior colliculus [SC] injection), axonal tyrosine kinase receptor (Trk) receptor inhibition with genistein, and acute axonal damage by optic nerve transection (ONT) were investigated at time points from 24 hours to 5 days. RESULTS ERK5 and MEK5 were present in RGCs and glial cells. Phospho-ERK5 levels increased in retina and decreased in brain with age (n = 4; P = 0.039). Phosphorylation of ERK5 but not ERK1/2 was increased or decreased by SC injection of BDNF or genistein, respectively (BDNF at 48 hours [p-ERK5: P = 0.01; p-ERK1/2: P = 0.55, n = 8]; genistein at 48 hours [p-ERK5: P = 0.01; p-ERK1/2: P = 0.5, n = 5]). ONT showed a similar trend. BDNF stimulation at the RGC soma increased both p-ERK5 and p-ERK1/2 (P = 0.035 and P = 0.032, respectively; n = 6; at 48 hours). CONCLUSIONS ERK5 is present in RGCs. Retina and brain p-ERK5 levels develop differently with age. The response of ERK5 but not ERK1/2 to BDNF stimulation or inhibition at the RGC axon ending indicates that retrograde neurotrophic signals in the rat optic nerve may be mediated by the ERK5 pathway.

The Antiproliferative Effect of Bevacizumab on Human Tenon Fibroblasts Is Not Mediated by Vascular Endothelial Growth Factor Inhibition.

Purpose Vascular endothelial growth factor-signaling in human tenon fibroblasts (hTFs) has recently become a target for antifibrotic treatment in glaucoma filtration surgery. The anti-VEGF antibody bevacizumab (BVC) has been shown to increase filtration bleb size. Given the relatively high concentration of BVC needed to obtain an effect, we investigated whether BVC acts through VEGF inhibition or via non-antigen-dependent ways. Methods Human tenon fibroblast primary cultures were obtained from strabismus surgery subjects. Under low (0.2%) and high (10%) serum conditions, cells were incubated with BVC, ranibizumab (RNB), aflibercept (AFB), or rituximab (RTX) at different concentrations. Total number of cells and number of dead or proliferating (5-bromo-2-deoxy-uridine-positive) cells were assessed after 24 hours. Concentrations of VEGF-A in cell culture media was measured with ELISA. Intracellular IgG was detected with immunostaining and Western blot analysis. Results In quiescent hTF culture (0.2% serum) the addition of 5 mg/mL BVC induced widespread cell death. Under proliferative conditions (10% serum), BVC reduced the number of proliferating cells. No such effect was observed with 2.5 mg/mL BVC or with 10 mg/mL AFB or 2.5 mg/mL RNB, although they were equally effective in binding free VEGF-A in the culture media. Instead, the CD20 antibody RTX, which did not bind VEGF, induced hTF death and inhibited proliferation in a BVC-comparable fashion. Bevacizumab, AFB, and RTX were detected intracellularly in a concentration-dependent manner. Conclusions The cell death-inducing and antiproliferative effect of 5 mg/mL BVC appeared not to depend on VEGF inhibition. Our data question a direct role of VEGF for hTF survival and proliferation.

Automated detection of Schlemm's canal in spectral-domain optical coherence tomography

Recent advances in optical coherence tomography (OCT) technology allow in vivo imaging of the complex network of intra-scleral aqueous veins in the anterior segment of the eye. Pathological changes in this network, draining the aqueous humor from the eye, are considered to play a role in intraocular pressure elevation, which can lead to glaucoma, one of the major causes of blindness in the world. Through acquisition of OCT volume scans of the anterior eye segment, we aim at reconstructing the three dimensional network of aqueous veins in healthy and glaucomatous subjects. A novel algorithm for segmentation of the three-dimensional (3D) vessel system in human Schlemms canal is presented analyzing frames of spectral domain OCT (SD-OCT) of the eyes surface in either horizontal or vertical orientation. Distortions such as vertical stripes are caused by the superficial blood vessels in the conjunctiva and the episclera. They are removed in the discrete Fourier domain (DFT) masking particular frequencies. Feature-based rigid registration of these noise-filtered images is then performed using the scale invariant feature transform (SIFT). Segmentation of the vessels deep in the sclera originating at or in the vicinity of or having indirect connection to the Schlemms canal is then performed with 3D region growing technique. The segmented vessels are visualized in 3D providing diagnostically relevant information to the physicians. A proof-of-concept study was performed on a healthy volunteer before and after a pharmaceutical narrowing of Schlemms canal. A relative decreases 17% was measured based on manual ground truth and the image processing method.

Functional assessment of the aqueous humour distal outflow pathways in bovine eyes using time-of-flight magnetic resonance tomography

ABSTRACT The major part of the aqueous humor leaves the eye through the “conventional outflow pathway”, consisting of the trabecular meshwork, Schlemms canal, collector channels, an intrasceral plexus and the episcleral veins. While the trabecular meshwork is well characterized, little is known about anatomical and functional features of the peripheral outflow tract beyond Schlemms canal. The emergence of minimally‐invasive glaucoma surgery directly targeting the outflow resistance in the trabecular meshwork has elicited growing interest in these structures. We used time‐of‐flight magnetic resonance imaging in ex vivo bovine eyes to map fluid flow under physiological conditions. We were able to identify the peripheral outflow vessels solely by the signal detected from the fluid flow inside their lumina. A question of clinical relevance is, whether localized opening of the trabecular meshwork leads to only localized or to a 360° increase in intrascleral flow. To address this, a goniotomy ab interno was performed in 3 eyes and the flow signal intensity was quantified sectorially. A significant increase in fluid flow was observed in the sector distal to the goniotomy (p = 0.0005) but not in the other sectors (p = 0.1). As a proof of concept we demonstrated that TOF‐MRI based detection of flow in the peripheral aqueous outflow tract is feasible. The functional link observed between trabecular meshwork sectors and their distal outflow tract sectors may be relevant for minimally‐invasive glaucoma surgery in humans. HighlightsMR time of flight imaging was applied to ex vivo bovine eyes.Fluid flow in collector channels and intrascleral aqueous veins could be detected.Sectorial goniotomy lead to increased flow only in the corresponding scleral sector.