Abstract
Purpose: :
To investigate apoptosis of rat model of oxygen-induced retinopathy (OIR).
Methods: :
Neonatal Sprague-Dawley rats were exposed to daily cycles of 80% oxygen (20.5 h), ambient air (0.5 h), and progressive return to 80% oxygen (3 h) until postnatal day 12 (P12), then the rats were placed in ambient air until P18. Rat pups in room air (RA) were used as controls. At P4, P8, P12, P13 and P18, the retinas were fixed for immunohistochemistry or collected for RT-PCR and Western blot analyses. Caspase-3 and cleaved caspase-3 were measured by Western blot. CHOP, BiP and sXBP mRNA which were markers for endoplasmic reticulum (ER) stress were measured by RT-PCR. Statistical analyses were performed with Kruskal-Wallis test and Mann-Whitney U-test. For immunohistochemistry, retinal tissues were stained with caspase-3 antibody and isolectin GS-IB4.
Results: :
P4, P12 and P18 of sXBP mRNA in OIR were higher than in RA (p<0.05). However, BiP and CHOP mRNA were same in OIR and RA. Caspase-3 and cleaved caspase-3 gradually decreased from P4 to P18 in both groups , and those in OIR were higher than in RA at each time point . In immunohistochemistry, cells stained with isolectin GS-IB4 seemed to co-localize with caspase-3.
Conclusions: :
Apoptosis remains through P4 to P18 in OIR. sXBP in OIR was higher than in RA, considering this model has ER stress. CHOP did not increase in OIR. The results indicate that other pathways (ie: mitochondria and / or death regands) except for ER stress may occur apoptosis in this model. Vascular endothelial cells seem to be the one of the apoptotic cells in OIR model.
Keywords: retinal neovascularization • apoptosis/cell death • retinal development