Impact of High Glucose Exposure on Induction of Apoptosis and Its Implication on Developing Retina of Zebrafish Embryos

The objective was to study the effects of high glucose on the morphological changes and to observe the expression of apoptosis regulatory proteins in the developing retina in vivo using zebrafish embryos. Wild-type male and female zebrafish were allowed for normal mating and the fertilized eggs were collected and exposed to hyperglycemic conditions (25 mM D-glucose) for 96 h. The embryos were subjected to various morphological and histological analyses in a time-dependent manner. The embryos showed morphological defects such as body curvature, abnormal eye shape, and low pigmentation of the eye in the high glucose-induced embryos compared to the control. Histomorphometry studies using H&E-stained slides showed increased thickness of GCL and INL and thinning of the IPL in the retina of high glucose-exposed embryos when compared to its time-matched control. Furthermore, the TUNEL assay and modified trichrome staining indicated apoptosis of many cells in the high glucose-induced group compared to the control. Immunohistochemistry findings revealed that expression of BAX, caspase 3, and caspase 9 was increased with decreased expression of Bcl-2 in the high glucose-treated group compared to control. From the present data, it is concluded that gestational exposure to high glucose stimulates apoptotic cell in the developing retinal layers via activating the pro-apoptotic and repressing the anti-apoptotic proteins.