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Kayla Titialii, Ann C Morris; Embryonic hyperglycemia is linked to a reduction in photoreceptor cells and increase in oxidative stress in the retina. Invest. Ophthalmol. Vis. Sci. 2019;60(9):3844.
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© ARVO (1962-2015); The Authors (2016-present)
Poor blood glucose regulation in Type I and II diabetes has been linked to various long-term complications in adults such as diabetic retinopathy. Yet, little is known about the effects of embryonic hyperglycemia on retinal development. Previously, we showed that hyperglycemia can be induced in zebrafish embryos by exposure to glucose and dexamethasone, which results in a reduction in differentiated photoreceptor cells in larval zebrafish. In this study, we determined the mechanism for the effect of hyperglycemia on retinal photoreceptor development.
All animal procedures were performed in accordance with guidelines established by the ARVO Statement for the Use of Animals in Ophthalmic and Vision Research. TaC:GFP, GFAP:GFP, and XOPS:GFP transgenic zebrafish embryos were exposed to 50mM glucose +/- 10µM dexamethasone or mannitol from 10 until 120 hours post fertilization (hpf). Reactive oxygen species (ROS) were visualized in live, treated larvae using an ROS probe from Invitrogen. Following live imaging, larval heads were fixed in paraformaldehyde, and bodies were homogenized for a glucose assay from Biovision. The fixed heads were processed for sectioning and immunohistochemistry to label and quantify rod and cone photoreceptors, Müller glia, and TUNEL+ apoptotic cells. Each treatment was performed a minimum of three times, with 25 animals per treatment group.
Treatment with 50mM glucose + 10µM dexamethasone from 10 until 120 hpf, reliably produced larvae with at least 2.5-fold increased whole-body glucose concentration compared to control larvae. Hyperglycemia was associated with a significant reduction in rod and cone photoreceptor cells, changes in cone outer segment morphology, and increase in ROS production in the outer nuclear layer. We also observed an increase in retinal cell apoptosis in hyperglycemic retinas. Intriguingly, Müller glia cell number in hyperglycemic retinas was increased compared to control-treated retinas.
Our results suggest that embryonic hyperglycemia results in abnormal photoreceptor development via ROS production and increased cell death, which is accompanied by changes in Müller glia cell number. The similarities between humans and zebrafish with respect to retinal structure and cell metabolism will allow us to study the mechanism of these effects, which will aid in the development of therapeutic strategies.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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