Proliferative Retinopathy: Study of the Contribution of Neuroglial Alterations and Development of gene Therapy Approaches.

Abstract

Diabetic retinopathy (DR) is the most common cause of acquired blindness in developed countries, with a high prevalence in diabetic patients. The development of new effective therapies requires further investigations on disease pathogenesis and good animal models are essential to this end and to assay the potential efficacy of new experimental therapies. The TgIGF-I mice is a good model of retinopathy, developing many of the retinal vascular alterations observed in human diabetic patients._x000D_ To fully characterize the eye pathology of the TgIGF-I, the first part of this work was focused in the study of the alterations of neurons and glial cells in the retinas of these mice. We found that TgIGF-I retinas showed a progressive decline in their electroretinographic responses that resulted in significantly impaired neuronal functionality in old animals. Gliosis and microgliosis were also detected in transgenic retinas at early ages. Gliosis is associated with the loss of essential neuron-supportive functions performed by Müller cells. We found that transgenic retinas showed changes in normal retinal metabolism, such as alterations in the glutamate metabolism, signs of oxidative stress and impaired potassium buffering, that may underlie neuronal dysfunction in transgenic retinas, which could be exacerbated by the increased production of pro-inflammatory cytokines. _x000D_ Thus, the second part of this work was dedicated to the study of the efficacy of a gene therapy approach aimed at counteracting neovascularization and neurodegeneration. Adeno-associated (AAV) vectors of serotype 2 were chosen to overexpress Pigmented Epithelium Derived Factor (PEDF), a protein with potent antiangiogenic and neuroprotective properties. AAV2-mediated PEDF gene transfer led to long-term production of PEDF and to a striking inhibition of intravitreal neovascularization, normalization of retinal capillary density, and prevention of retinal detachment. This was parallel to a reduction in the intraocular levels of Vascular Endothelial Growth Factor (VEGF), that was consistent with a downregulation of downstream effectors of angiogenesis. These results demonstrate long-term efficacy of AAV-mediated PEDF overexpression in counteracting retinal neovascularization and provide evidence towards the use of this strategy to treat angiogenesis in DR and other chronic proliferative retinal disorders.

Date of Award	31 May 2012
Original language	English
Supervisor	Maria Fatima Bosch Tubert (Director) & Virginia Haurigot Mendoça (Director)