Wright, Matthew James; (1999) In vivo myocardial gene transfer: Optimization and evaluation of gene transfer models and vectors. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

In Vivo Myocardial Gene Transfer: Optimization and Evaluation of Gene Transfer Models and Vectors Background: Acute myocardial infarction and its sequelae are recognised as the most common cause of mortality and morbidity in industrialised nations, and are predicted to continue to rise well into the 21st century. One of the most promising treatments that may be applied in the future is gene therapy. In order for this to become a reality a number of steps have to be mastered, with the initial problem being efficient and safe delivery of genetic material to the adult myocardium. Aim: This thesis examines in vivo myocardial gene transfer using a number of different gene transfer vectors and different models of vector delivery to the adult myocardium. Methods: In vivo gene transfer was attempted by two basic models of vector delivery, either direct intramyocardial injection or percutaneous transluminal intracoronary delivery. There are a number of different gene transfer vectors for use in either the heart or other organ systems, with differing properties. In order to perform rational experiments in the future a number of different vectors, including recombinant adenovirus, recombinant herpes simplex virus, recombinant adeno-associated virus, cationic liposomes, integrin targeting peptides and naked DNA, were tested in the direct intramyocardial injection model of gene transfer. Intracoronary infusion of the best vector from the direct comparison studies was used to improve this model of vector delivery. Gene transfer efficiency was determined by expression of an encoded reporter gene, with histological assessment of toxicity of the different vectors. Results: Direct intramyocardial injection of recombinant viral vectors resulted in gene transfer, with recombinant adenovirus being the most efficient, recombinant herpes simplex virus was both less efficient and more toxic to the myocardium, with subsequent shorter expression of the transgene. Transgene expression following direct intramyocardial injection of recombinant adeno- associated virus was delayed, until 21-28 days post gene transfer, in accordance with the lifecycle of the virus, however no toxicity was observed. Intracoronary infusion of lipoplexes and, contrary to previous work, recombinant adenovirus was inefficient. However, development of a closed chest model of myocardial infarction demonstrated that a false positive appearance of gene transfer is seen following infarction. Conclusions: Gene transfer using either recombinant adenoviral or recombinant adeno-associated virus offer 2 contrasting vectors for gene delivery, with the toxicity profile of the latter vector allowing direct intramyocardial injection of the vector, whereas the more efficient, but also more toxic recombinant adenovirus is best employed using high-pressure intracoronary delivery.

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