Effects of Ischaemia on the Neuroretina and Retinal Blood Vessels

Sammanfattning: Identification of the intracellular signal transduction pathways activated in retinal ischaemia may be important in revealing novel pharmacological targets. The retinal blood vessels are key organs in circulatory failure, and in this work the retinal vasculature was therefore examined separately from the neuroretina. The porcine eye has a typical primate-like architecture and is similar to the human eye regarding its size and retinal blood supply. The arteries in the porcine eye are large enough to allow dissection, and can be used for both functional and molecular analysis. Therefore, the first aim of this work was to set up and evaluate a porcine model of pressure-induced retinal ischaemia-reperfusion injury. The second aim was to study the intracellular signal transduction pathways activated in retinal ischaemia, including mitogen-activated protein kinases (MAPKs), protein kinase C (PKC), tumour necrosis factor (TNF), hypoxia-inducible factor (HIF) and vascular endothelial growth factor (VEGF). The results show that the porcine model of retinal ischaemia-reperfusion was successfully established, and that retinal blood vessels and the neuroretina could be studied separately. The retinal circulation was completely obstructed at an intra ocular pressure of 80 mmHg, and fluorescein angiography during reperfusion showed how the circulation was restored. Changes were seen in multifocal electroretinograms following the ischaemic insult, showing decreased amplitudes and increased implicit times. Pyknotic cell nuclei count, TUNEL-positive cells and glial fibrillary acidic protein mRNA expression were increased as a result of ischaemia, suggesting retinal injury and glial cell activation. The expression of signalling pathways including MAPKs, PKC, TNF, HIF and VEGF was altered in both the neuroretina and retinal arteries, in a way that is typical of ischaemia. These are intracellular signalling molecules that may be important in the development of retinal injury following ischaemia, and may thus be interesting targets for the development of pharmacological therapeutic agents.