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| August 2005 | Inside IOVS | Volume 46/8 |
Graft-Versus-Host Disease of the Lacrimal Gland in an Animal Model
Hassan et al. (p. 2692) have developed a mouse model of lacrimal gland graft-versus-host disease (GVHD). Their findings closely parallel those of human disease and reveal that GVHD may affect the lacrimal gland early in the course of the disease. The implications of this finding may prompt early intervention to prevent severe dry eyes, commonly found in patients after bone marrow transplantation.
Retinal Shapes in Myopic Eyes
Using magnetic resonance imaging, Atchison et al. (p. 2698) found that both emmetropic and myopic retinas are oblate in shape, that is, they steepen away from the vertex. Myopic eyes are less oblate than emmetropic eyes. This finding is relevant to theories implicating the peripheral retina in myopia development.
Hypoxia and VEGF Promote PEDF MMP-Mediated Proteolysis
Several neovascular ocular diseases triggered by oxygen deprivation are associated with decreased levels of pigment epithelium-derived factor (PEDF), the principal antiangiogenic and neurotrophic protein of the eye. Notari et al. (p. 2736) show that hypoxia and VEGF can decrease PEDF protein at a post-translational level by increasing PEDF proteolysis mediated by MMPs. They demonstrate that PEDF is a substrate for MMP-2 and MMP-9 and that MMP-mediated proteolytic degradation abolishes its neurotrophic and antiangiogenic activities. Their results reveal a novel post-translational mechanism for downregulating PEDF, which provides a model for molecular players that control the hypoxia-provoked increases in VEGF/PEDF ratio, angiogenesis and/or neuronal death.
Secret Mission of the Superior Oblique
Like other extraocular muscles, the superior oblique has orbital and global layers. While orbital layers of other muscles move their pulleys, the superior oblique's trochlea is attached to immobile bone. Using magnetic resonance imaging and histology in humans and monkeys, Kono et al. (p. 2790) have now demonstrated that an extension of the superior oblique's orbital layer travels through the trochlea to change positions of rectus pulleys. This anatomy allows the superior oblique not only to twist the eye around the line of sight as long known, but also to coordinate this eye twist with changes in pulling directions of rectus muscles.
Hypophosphorylated sCD44 in POAG Aqueous Humor and Cell Death
Primary open-angle glaucoma (POAG) is a common neurodegenerative disease, and the aqueous humor of patients with POAG has increased concentration of the ectodomain of CD44, i.e., soluble CD44 (sCD44). In the study of Knepper et al. (p. 2829), a novel, hypophosphorylated form of sCD44 was identified in POAG aqueous humor. Since a hypophosphorylated sCD44 was cytotoxic to TM and RGC cells in vitro, a hypophosphorylated sCD44 in POAG aqueous humor is a possible protein candidate for the cause of cell death in POAG. The presence of hypophosphorylated sCD44 clearly distinguished POAG from normal aqueous humor, suggesting a specific pathophysiology and a biochemical hallmark of the disease.
The Receptor for Advanced Glycation End Products in Early Diabetic Retinopathy
Barile et al. (p. 2916) investigated the role of the receptor for advanced glycation endproducts (RAGE) and its AGE ligands in a mouse model of early diabetic retinopathy. RAGE was primarily localized to Müller cells, and AGE ligands accumulated within the extracellular matrix including the internal limiting membrane of diabetic retina. Attenuation of the amplified RAGE axis reduced the neural perturbations and vascular disease of early diabetic retinopathy. The study suggests that the accelerated glycation that occurs in diabetes mellitus is a relevant therapeutic target for retinopathy and that the Müller cell is worthy of further investigation in the pathogenesis of diabetic retinopathy.
Preschool Vision Screening by Nurse Screeners and Lay Screeners
Results of Phase II of the Vision In Preschoolers (VIP) Study (p. 2639) showed that nurse screeners and lay screeners achieved similar accuracy when administering two of the best-performing preschool vision screening tools (Retinomax Autorefractor and SureSight Vision Screener). Lay screeners were also able to achieve good results on a modified version of the Lea Symbols Visual Acuity Test. These results support use of trained lay people as preschool vision screeners.
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