This thesis describes a programme of work designed to investigate the molecular pathways in the retinal response to hypoxia and to develop new therapeutic strategies for ischemic retinal disorders. The first hypothesis investigated was that ischaemia-induced angiogenesis can be controlled by targeting the oxygen-sensing pathway at the level of hypoxia-inducible transcription factor (HIF) translation. This was addressed by RNA interference (RNAi) in vitro and in murine oxygen-induced retinopathy (OIR). The second hypothesis investigated was that murine OIR offers a model of ischemic neurodegeneration in which to investigate endogenous mechanisms of neuroprotection and to develop novel therapeutic interventions. This was tested by evaluating the effect of OIR on the structure and function of the neuroretina, and by investigating the neuroprotective effect of erythropoietin in this model. The temporal and spatial distribution of retinal hypoxia in murine OIR was closely correlated with the distribution of HIF-α isoforms in the retina, with significant isoform-specificity in distinct cell populations. Synthetic siRNAs targeting HIF-1α and HIF-2α resulted in effective knockdown of RNA and protein in vitro with a high degree of isoform specificity. Efficient HIF-α protein knockdown in vivo was not achieved, however, despite optimisation of timing and transfection conditions. Retinal ischaemia in OIR was associated with significant dysfunction and focal degeneration of the inner neuroretina. Mild photoreceptor dysfunction was also detected. Erythropoietin deficiency in OIR resulted in an exaggerated retinal dysfunction that was reversed by exogenous supplementation. The results suggest that HIF-1α and HIF-2α have distinct roles in retinal oxygen sensing. RNAi-mediated HIF-α knockdown is effective in vitro but further development of delivery strategies is required to achieve effective knockdown in vivo. Murine OIR offers a valuable model of ischemic neurodegeneration in which to investigate endogenous responses and to evaluate novel therapeutic approaches. Endogenous expression of erythropoietin has a neuroprotective role in this model.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:625195 |
| Date | January 2009 |
| Creators | Mowat, F. |
| Publisher | University College London (University of London) |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://discovery.ucl.ac.uk/17506/ |
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