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. Methods: Form-deprivation myopia was induced in the right eyes of two-day-old chicks by the application of translucent occluders. Following 10 days of deprivation, occluders were removed and chicks were provided unrestricted vision for an additional 1–7 days (recovery). After one and four days of recovery, chicks were sacrificed, retina, RPE, and choroid were isolated, and mRNA was subjected to microarray analysis using a chicken immune system 4000 gene microarray. In addition, whole eyes and isolated ocular tissues (retina and RPE, choroid, sclera, and extraocular muscle) of treated and control eyes were subjected to real-time PCR, immunohistochemistry, and western blot analyses to verify gene expression results. Results: Following one day of recovery, only one gene, avian thymic hormone (ATH) was highly upregulated (+12.3 fold). ATH gene and protein expression were confirmed in the retina and choroid as well as in the sclera and extraocular muscle. A significant increase in ATH protein was detected in choroids from treated eyes following four days of recover

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. Scleral sulfated glycosaminoglycan synthesis was assessed on punches of sclera obtained immediately after extraction of suprachoroidal fluid for permeability measurements or after incubation with suprachoroidal fluid by measuring the amount of 35 SO 4 incorporated into glycosaminoglycans over a period of 4 hours at 37°C. Suprachoroidal fluid was subjected to size fractionation and proteinase digestion to characterize the bioactive fractions from recovering and control chick eyes. RESULTS. Recovery from prior form deprivation was associated with a significant increase in choroidal permeability, compared with that of myopic eyes and contralateral control eyes, and was coincident with a significant decrease in scleral sulfated glycosaminoglycan synthesis rates in treated eyes compared with contralateral control eyes. Suprachoroidal fluid isolated from recovering chick eyes significantly inhibited scleral glycosaminoglycan synthesis compared with suprachoroidal fluid from control eyes (-54%; P Ͻ 0.01; ANOVA). Preliminary characterization of suprachoroidal fluid suggested that all inhibitory activity in suprachoroidal fluid fractions specific to recovering eyes is present in molecular weight fractions of less than 10 kDa. CONCLUSIONS. The results of this study suggest that increased choroidal permeability coincides with a decrease in the rate of scleral glycosaminoglycan synthesis during recovery from myopia. The authors speculate that increased choroidal permeability may represent a mechanism for controlling the rate of delivery of bioactive factors to the sclera to regulate the rate of glycosaminoglycan synthesis in the posterior sclera. (Invest Ophthalmol Vis Sci

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. For examining the effect of melatonin on ocular growth, chicks were maintained on a 12-hour light-dark cycle and were monocularly form-vision deprived in one eye with a translucent occluder for 5 days. During the 5-day treatment period, chicks were injected systemically during the early dark period with melatonin (0.6 mg) or 2% ethanol vehicle control. Ocular dimensions of normal and deprived eyes were examined by high frequency A-scan ultrasound. RESULTS. Immunocytochemical analysis of chick ocular tissues revealed the cellular distribution of the Mel 1a receptor subtype in the cornea, choroid, sclera, and retina. Western blot and slot blot analyses demonstrated that all three receptors were present in these tissues and they demonstrated distinct diurnal rhythms of protein expression in the retina-RPE-choroid, with peak levels of Mel 1a and Mel 1b occurring during the night and peak levels of Mel 1c during the day. Systemic administration of melatonin resulted in significant changes in anterior chamber depth, vitreous chamber depth, and choroidal thickness of form-deprived and/or control eyes. CONCLUSIONS. Results of this study show that all three melatonin receptor subtypes are expressed in retinal and extraretinal ocular tissues of the chick eye. The finding that administration of melatonin alters the growth of several ocular tissues in both control and form-deprived eyes suggests that melatonin, acting through specific melatonin receptors in ocular tissues, plays a role in ocular growth and development. This conclusion suggests that the action of melatonin, combined with expression of melatonin receptors, is involved in the regulation of the diurnal rhythm of ocular growth. (Invest Ophthalmol Vis Sci

Region-specific differential corneal and scleral mRNA expressions of MMP2, TIMP2, and TGFB2 in highly myopic-astigmatic chicks

2017-2018 > Academic research: refereed > Publication in refereed journal201805 bcrcVersion of RecordPublishe