Objective We studied gene regulation in the retina after hypoxia and reoxygenation with 21% or 100% oxygen. In retinal cells VEGF production is regulated by HIF-1α. VEGF receptor-2 (VEGFR2) is strongly expressed by retinal neuronal cells and plays a role in retinal neuroprotection.
Methods Newborn piglets (12–36 h) underwent hypoxia until base excess was −20 mmol/L or mean arterial blood pressure was <20 mmHg. They were randomly assigned for resuscitation with 21% or 100% oxygen for 15 min and then ventilation with room air for 45 min, or to receive 100% oxygen for 60 min. Retinal tissue was sampled after 15 and 60 min in the first two groups, and after 30 and 60 min in the third group. After isolation, the tissue was immediately snap frozen in liquid nitrogen and stored by −70°C until analysis. RNA was isolated from retinal tissue and gene expression levels for vascular endothelial growth factor a (VEGFa), VEGFR1, VEGFR2 and HIF-1α were determined by RT-PCR.
Results Hypoxia and reoxygenation with 100% oxygen vs room-air for 15 or 30 min both gave a down regulation of VEGFR2 (p = 0.04). HIF-1α was down regulated after 60 min reoxygenation with 100% oxygen vs room air, but also vs 15 min 100% oxygen exposure and then room air (p = 0.04).
Conclusion Hyperoxia by resuscitation alters gene expression in retinal cells. The down regulation in VEGFR2 expression after 100% oxygen could indicate less neuroprotection.