Identification of RALDH2 as a visually regulated retinoic acid synthesizing enzyme in the chick choroid.

Purpose: All-trans-retinoic acid (atRA) has been implicated in the local regulation of scleral proteoglycan synthesis in vivo. The purpose of the present study was to identify the enzymes involved in the synthesis of atRA during visually guided ocular growth, the cells involved in modulation of atRA biosynthesis in the choroid, and the effect of choroid-derived atRA on scleral proteoglycan synthesis.

Methods: Myopia was induced in White leghorn chicks by form deprivation for 10 days, followed by up to 15 days of unrestricted vision (recovery).

Increased hyaluronan synthase-2 mRNA expression and hyaluronan accumulation with choroidal thickening: response during recovery from induced myopia.

Purpose: Several studies have convincingly shown that in chicks, compensation for imposed focus involves immediate changes in choroid thickness. The molecular events associated with choroidal thickening and the regulation of the choroidal response are largely unknown.

Methods: Form-deprivation myopia was induced in the right eyes of 2-day-old chicks by the application of translucent occluders for 10 days and was followed by unrestricted vision for an additional 1 to 20 days (recovery).

Melatonin receptor expression in Xenopus laevis surface corneal epithelium: diurnal rhythm of lateral membrane localization.

Purpose: Melatonin receptors are seven-pass G protein-coupled receptors located in many tissues throughout the body, including the corneal epithelium (CE), and relay circadian signals to the target cells. The purpose of this study was to determine more precisely the cellular distribution of the melatonin receptors in the surface cells of the CE of Xenopus laevis, and to examine the relative distribution of melatonin receptor subtype expression at different times during the circadian cycle.

Methods: Cryostat sections and whole corneas of adult Xenopus laevis were processed for immunocytochemistry using antibodies specific for each of the three melatonin receptor subtypes (Mel1a, Mel1b, and Mel1c).

Ocular expression of avian thymic hormone: changes during the recovery from induced myopia.

Purpose: Several studies suggest that postnatal ocular growth is under the control of factors within the eye that regulate the rate of scleral extracellular matrix remodeling and the rate of ocular elongation. A microarray analysis was employed to identify some of the factors involved in the regulation of visually guided ocular growth. Gene expression was compared in the retina-retinal pigmented epithelium (RPE)-choroid of chick eyes that were decelerating in the rate of ocular growth ("recovering" from myopia) as compared with contralateral control eyes.

Inhibition of human scleral fibroblast cell attachment to collagen type I by TGFBIp.

Purpose: Transforming growth factor beta-induced protein (TGFBIp; 68 kDa) is a secreted extracellular matrix (ECM) protein that has been demonstrated to regulate cell attachment in a variety of cell types. The sclera synthesizes and secretes TGFBIp, which may function to facilitate scleral ECM remodeling events associated with myopia development. Here the authors report that human scleral fibroblasts (HSFs) express TGFBI and that its protein product, TGFBIp, mediates an effect on cell attachment.

Choroidal regulation of scleral glycosaminoglycan synthesis during recovery from induced myopia.

Purpose: The present study was undertaken to examine the relationship between choroidal permeability and scleral glycosaminoglycan synthesis rates during the development of and recovery from form deprivation myopia.

Methods: Form deprivation myopia was induced in chicks for 10 days and was followed by a period of unrestricted vision for 0 to 15 days (recovery). Choroidal permeability was quantified by measuring albumin leakage from choroidal blood vessels into suprachoroidal fluid using Evans blue.

Small leucine rich repeat proteoglycans (SLRPs) in the human sclera: identification of abundant levels of PRELP.

Purpose: The small leucine rich proteoglycan (SLRP) family is made up of several members which are thought to guide matrix assembly and organization through protein:protein and/or protein:carbohydrate interactions. In order to better characterize the composition of the scleral extracellular matrix, gene and protein expression of several members of the SLRP family were evaluated in the human sclera from donors aged 2-93 years of age.

Methods: Semi-quantitative and quantitative RT-PCR analyses were performed on RNA isolated from human donor sclera using primers for decorin, fibromodulin, PRELP (proline arginine rich end leucine-rich protein), biglycan, chondroadherin, and lumican.

Melatonin receptors in chick ocular tissues: implications for a role of melatonin in ocular growth regulation.

Purpose: The influences of diurnal rhythms involving a variety of ocular parameters are implicated in the development of myopia. The purpose of this study was to determine the expression of the melatonin receptor subtype proteins in chick ocular tissues and to examine the role of the circadian signaling molecule melatonin in normal ocular growth and the exaggerated ocular growth associated with the development of myopia.

Methods: Expression of the Mel(1a), Mel(1b), and Mel(1c) melatonin receptor proteins in ocular tissues was examined by Western blot analyses, slot blot analyses, and immunocytochemistry.

The sclera and myopia.

Myopia is a very common ocular problem, affecting perhaps one billion people worldwide. Most myopia is produced by lengthening of the vitreous chamber of the ocular globe. High myopia is characterized by scleral thinning and localized ectasia of the posterior sclera.

Interaction of lumican with aggrecan in the aging human sclera.

Purpose: Lumican is a keratan sulfate proteoglycan originally identified in cornea, but present in a variety of connective tissues where it presumably regulates collagen fibril formation and organization. The present study was designed to describe the chemical nature of lumican core protein in the aging human sclera.

Methods: Western blot analyses, immunohistochemistry, and immunoaffinity chromatography were used to detect and purify the lumican core protein from tissue extracts from human donors 6 to 89 years of age.

Microarray analysis of gene expression in human donor sclera.

Purpose: To develop gene expression profiles of human sclera to allow for the identification of novel, uncharacterized genes in this tissue-type, and to identify candidate genes for scleral disorders.

Methods: Total RNA was isolated from 6 donor sources of human sclerae, and reverse transcribed into cDNA using a T7-(dT) 24 primer. The resulting cDNA was in vitro transcribed to produce biotin-labeled cRNA, fragmented, and mixed with hybridization controls before a 16 h hybridization step with oligonucleotide probes on 6 Affymetrix U95A chips.

Identification of genes expressed in a human scleral cDNA library.

Purpose: Clones established from a human scleral cDNA library were systematically sequenced. Public database sequence comparisons were performed to generate a profile of genes expressed in the human sclera and identify candidate genes for inherited diseases with scleral involvement.

Methods: A directionally cloned pCMV-PCR cDNA library was constructed from RNA isolated from scleras of human donor eyes with known plano refractive history.

Melatonin receptor expression in the cornea and sclera.

The scornea and sclera have been shown to exhibit circadian rhythms in cellular proliferation, wound healing and extracellular matrix synthesis. The distribution of melatonin Mel1a and Mel1c receptors was examined in the cornea and sclera of the Xenopus laevis eye in order to determine whether melatonin may potentially influence the growth and/or development of these ocular tissues. Sections of adult X.

Altered collagen fibril formation in the sclera of lumican-deficient mice.

Purpose: To better understand the role of lumican (corneal keratan sulfate proteoglycan) in the scleral extracellular matrix, collagen fibril size, shape, and organization were evaluated in the sclera of wild-type mice and in mice homozygous or heterozygous for a null mutation in the lumican gene. METHODS. Anterior and posterior sclera from 6-month-old wild-type (lum+/lum+) and lumican-deficient mice (lum+/lum- and lum-/lum-) were analyzed by transmission electron microscopy.