Resveratrol, an Inhibitor Binding to VEGF, Restores the Pathology of Abnormal Angiogenesis in Retinopathy of Prematurity (ROP) in Mice: Application by Intravitreal and Topical Instillation.

Retinopathy of prematurity (ROP) is a severe eye disease leading to blindness. Abnormal vessel formation is the pathological hallmark of neovascular ROP. In forming vessels, vascular endothelial growth factor (VEGF) is an important stimulator. The current anti-ROP therapy has focused on bevacizumab, a monoclonal antibody against VEGF, and pazopanib, a tyrosine kinase inhibitor on the VEGF receptor (VEGFR). Several lines of evidence have proposed that natural compounds may be more effective and safer for anti-VEGF function. Resveratrol, a common natural compound, binds to VEGF and blocks its interaction with VEGFR, thereafter suppressing angiogenesis. Here, we evaluate the efficacy of intravitreal injection, or topical instillation (eye drops), of resveratrol into the eyes of mice suffering from oxygen-induced retinopathy, i.e., developing ROP. The treatment of resveratrol significantly relieved the degree of vascular distortion, permeability and hyperplasia; the efficacy could be revealed by both methods of resveratrol application. In parallel, the treatments of resveratrol inhibited the retinal expressions of VEGF, VEGFR and CD31. Moreover, the applied resveratrol significantly relieved the damage caused by oxygen radicals through upregulating the level of superoxide dismutase (SOD) and downregulating the level of malondialdehyde (MDA) in the retina. Taken together, the potential therapeutic benefit of resveratrol in pro-angiogenic diseases, including retinopathy, can be considered.

Partially Differentiated Neuroretinal Cells Promote Maturation of the Retinal Pigment Epithelium.

Purpose: Many studies have demonstrated the ability of the retinal pigment epithelium (RPE) to foster the maturation of the developing retina. Few studies have examined the reciprocal effects of developing retina on the RPE. Methods: RPE isolated from human fetal RPE or differentiated from human stem cells was cultured on Transwell filter inserts. Retinal progenitor cells (RPCs) were differentiated from human stem cells and cultured on a planar scaffold composed of gelatin, chondroitin sulfate, hyaluronic acid, and laminin-521. Cultures were analyzed by quantitative RT-PCR, immunofluorescence, immunoblotting, and transepithelial electrical resistance (TER). Results: RPCs initially differentiated into several retina-like cell types that segregated from one another and formed loosely organized layers or zones. With time, the presumptive photoreceptor and ganglion cell layers persisted, but the intervening zone became dominated by cells that expressed glial markers with no evidence of bipolar cells or interneurons. Co-culture of this underdeveloped retinoid with the RPE resulted in a thickened layer of recoverin-positive cells but did not prevent the loss of interneuron markers in the intervening zone. Although photoreceptor inner and outer segments were not observed, immunoblots revealed that co-culture increased expression of rhodopsin and red/green opsin. Co-culture of the RPE with this underdeveloped retinal culture increased the TER of the RPE and the expression of RPE signature genes. Conclusions: These studies indicated that an immature neurosensory retina can foster maturation of the RPE; however, the ability of RPE alone to foster maturation of the neurosensory retina is limited.

Update on Intraocular Lens Formulas and Calculations.

Investigators, scientists, and physicians continue to develop new methods of intraocular lens (IOL) calculation to improve the refractive accuracy after cataract surgery. To gain more accurate prediction of IOL power, vergence lens formulas have incorporated additional biometric variables, such as anterior chamber depth, lens thickness, white-to-white measurement, and even age in some algorithms. Newer formulas diverge from their classic regression and vergence-based predecessors and increasingly utilize techniques such as exact ray-tracing data, more modern regression models, and artificial intelligence. This review provides an update on recent literature comparing the commonly used third- and fourth-generation IOL formulas with newer generation formulas. Refractive outcomes with newer formulas are increasingly more and more accurate, so it is important for ophthalmologists to be aware of the various options for choosing IOL power. Historically, refractive outcomes have been especially unpredictable in patients with unusual biometry, corneal ectasia, a history of refractive surgery, and in pediatric patients. Refractive outcomes in these patient populations are improving. Improved biometry technology is also allowing for improved refractive outcomes and surgery planning convenience with the availability of newer formulas on various biometry platforms. It is crucial for surgeons to understand and utilize the most accurate formulas for their patients to provide the highest quality of care.

A biodegradable scaffold enhances differentiation of embryonic stem cells into a thick sheet of retinal cells.

Retinal degeneration is a leading cause of blindness in developed countries. Stem cells can be differentiated into retinal organoids to study mechanisms of retinal degeneration, develop therapeutic agents, and potentially serve as replacement tissues. The spherical nature of these retinoids limits their utility, because the investigator lacks ready access to both sides of the neo-tissue. For tissue-replacement, spherical retinoids are unable to interact simultaneously with the host retinal pigment epithelium and remaining neurosensory retina. To attempt making a planar retinoid, we developed a biodegradable scaffold that simulates the extracellular matrix of the neurosensory retina. Human embryonic stem cells were seeded on the scaffold. Differentiation into retinal cells was confirmed by quantitative RT-PCR, confocal immunocytochemistry, and immunoblotting. The scaffold favored differentiation into retinal cell types over other anterior forebrain cells, but retinal lamination was rudimentary. The cultures elicited a minimal immune response when implanted into the subretinal space of a mouse model of retinal degeneration. The implants survived for at least 12 weeks, but there was evidence of cytoplasmic transfer rather than implantation into the outer nuclear layer (photoreceptor layer). However, some implanted cells migrated to the inner layers of the retina and established elaborate arbors of neurites.

Effects of diabetic retinopathy on the barrier functions of the retinal pigment epithelium.

Diabetic retinopathy is a debilitating microvascular complication of diabetes mellitus. A rich literature describes the breakdown of retinal endothelial cells and the inner blood-retinal barrier, but the effects of diabetes on the retinal pigment epithelium (RPE) has received much less attention. RPE lies between the choroid and neurosensory retina to form the outer blood-retinal barrier. RPE's specialized and dynamic barrier functions are crucial for maintaining retinal health. RPE barrier functions include a collection of interrelated structures and activities that regulate the transepithelial movement of solutes, including: diffusion through the paracellular spaces, facilitated diffusion through the cells, active transport, receptor-mediated and bulk phase transcytosis, and metabolic processing of solutes in transit. In the later stages of diabetic retinopathy, the tight junctions that regulate the paracellular space begin to disassemble, but there are earlier effects on the other aspects of RPE barrier function, particularly active transport and metabolic processing. With advanced understanding of RPE-specific barrier functions, and more in vivo-like culture models, the time is ripe for revisiting experiments in the literature to resolve controversies and extend our understanding of how diabetes affects the outer blood-retinal barrier.

Feasibility of retinal screening in a pediatric population with type 1 diabetes mellitus.

PURPOSE: To study the feasibility of using a nonmydriatic camera to screen children with type 1 diabetes mellitus (DM1) as young as 2 years for diabetic retinopathy. METHODS: Prospective pilot imaging study involving children with DM1 aged 2 to 17 years. The screening consisted of: (1) intake form; (2) measurement of blood pressure, pulse, and oximetry; (3) assessment of visual acuity (SIMAV, Padova, Italy); and (4) nonmydriatic color imaging (Canon CX-1 45° 15.1 megapixel camera; Canon Corp., Tokyo, Japan). Images were assessed for signs of diabetic retinopathy and graded for quality on a scale of 1 to 5 by two clinicians. Kappa coefficient was calculated to determine inter-observer agreement. RESULTS: One hundred four of 106 (98%) children underwent imaging (mean age: 11.1 years, 51% male, 88% white). One (1%) child had nonproliferative diabetic retinopathy and 2 (1.9%) had incidental findings. Only 62% of children had an eye examination within the past year, with children with DM1 for more than 5 years significantly more likely to have done so (P = .03). Children who had an eye examination within the past year were significantly older than their counterparts (P = .01). Images of high quality (grades 4 and 5) were acquired in 178 (86%) eyes, and images of some clinical value (grades ≥ 2) were obtained in 207 (99.5%) eyes. Inter-observer agreement for image quality was 0.896. CONCLUSIONS: The feasibility of using a nonmydriatic camera to screen children as young as 2 years for changes related to diabetic eye disease was demonstrated. Nonmydriatic imaging may supplement standard dilated clinical ophthalmology examinations for select patient populations.

C-Abl inhibitor imatinib enhances insulin production by ß cells: c-Abl negatively regulates insulin production via interfering with the expression of NKx2.2 and GLUT-2.

Chronic myelogenous leukemia patients treated with tyrosine kinase inhibitor, Imatinib, were shown to have increased serum levels of C-peptide. Imatinib specifically inhibits the tyrosine kinase, c-Abl. However, the mechanism of how Imatinib treatment can lead to increased insulin level is unclear. Specifically, there is little investigation into whether Imatinib directly affects ß cells to promote insulin production. In this study, we showed that Imatinib significantly induced insulin expression in both glucose-stimulated and resting ß cells. In line with this finding, c-Abl knockdown by siRNA and overexpression of c-Abl markedly enhanced and inhibited insulin expression in ß cells, respectively. Unexpectedly, high concentrations of glucose significantly induced c-Abl expression, suggesting c-Abl may play a role in balancing insulin production during glucose stimulation. Further studies demonstrated that c-Abl inhibition did not affect the major insulin gene transcription factor, pancreatic and duodenal homeobox-1 (PDX-1) expression. Of interest, inhibition of c-Abl enhanced NKx2.2 and overexpression of c-Abl in ß cells markedly down-regulated NKx2.2, which is a positive regulator for insulin gene expression. Additionally, we found that c-Abl inhibition significantly enhanced the expression of glucose transporter GLUT2 on ß cells. Our study demonstrates a previously unrecognized mechanism that controls insulin expression through c-Abl-regulated NKx2.2 and GLUT2. Therapeutic targeting ß cell c-Abl could be employed in the treatment of diabetes or ß cell tumor, insulinoma.

Optic disc drusen in a child: diagnosis using noninvasive imaging tools.

PURPOSE: To describe a case of bilateral optic nerve head drusen (ONHD) in a pediatric patient and the complementary use of advanced noninvasive imaging techniques to confirm this diagnosis. CASE REPORT: A 15-year-old female adolescent with type 1 diabetes and no ocular history was seen at a routine screening without complaints. Visual acuity was 20/20 bilaterally, and visual fields using frequency doubling technology (Zeiss Humphrey Systems, Dublin, CA) were within normal limits. Fundus photography (CX-1 Mydriatic/Non-Mydriatic Hybrid Digital Retinal Camera, Canon, Toyko, Japan) showed slight elevation of the left disc margin, with lack of physiologic cup, elevation of the inferior neuroretinal rim, and no swelling of the nerve fiber layer. Fundus autofluorescence image of the left eye showed hyperfluorescence in the inferior optic disc. Red/green/blue channel separation analysis using the blue channel (Eye-Q software, Canon, Irvine, CA) showed elevation of the nerve fiber layer without obscuration of small vessels surrounding the left optic disc. Embossed technique highlighted the drusen in the left disc. B-scan ultrasound (Eye Cubed, Ellex, Adelaide, Australia) showed a hyperechoic focus on the optic disc with posterior shadowing and corresponding spike on A-scan in both eyes, indicative of bilateral drusen. Optical coherence tomography (RTVue, Optovue, Fremont, CA) showed an elevation in the ONH corresponding to the drusen. CONCLUSIONS: The complementary use of noninvasive imaging modalities such as fundus autofluorescence, red/green/blue separation, B-scan, and optical coherence tomography is important in confirming the diagnosis of ONHD in pediatric patients. They allow us to rule out more serious conditions and avoid unnecessary, costly, and invasive investigative procedures, relieving young patients and their families of potential financial and emotional burdens.