Résumé :
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Gene transfer is an interesting therapeutic approach for inherited muscular dystrophies with no curative treatment currently available. Nevertheless, DNA does not freely cross the membranes as it is a hydrophilic, negatively charge macromolecule, rendering thus formulation of nucleic acids a major concern. Synthetic vectors appear as a promising approach and particularly polymer based formulations. Among those, Polyethyleneimine (PEI), a polymer exhibiting a high density of positive charges and amphiphilic Tetronic 304 and Pluronic L64, displaying few or no charges, seem of particular interest to transfer DNA. Our work has focused on determining the influence of several formulation parameters on the organization of polymer/DNA systems. We have studied the correlation between these modifications and the toxicity and efficiency of the systems in vivo. Complexation of PEI with DNA is leading to small nanoparticles displaying relatively strong interactions. After in vivo administration, PEI/DNA complexes exhibited a high toxicity towards skeletal muscle. Amphiphilic polymers associated to DNA are generating more complex systems displaying weaker interactions. In vivo, no lesions were detected with amphiphilic polymers based formulations. Moreover, these formulations allowed significant improvement of gene transfer to the skeletal muscle with reference to naked DNA, even at low DNA doses. Our experiments highlighted the role of the medium and the temperature to optimize in vivo efficiency of Pluronic L64 vectors. Moreover, these findings could be correlated to modifications of the supramolecular organization of these systems depending on the conditions utilized. Our studies have emphasized the interest of amphiphilic polymers displaying few or no charges to transfer DNA in the skeletal muscle. The supramolecular organization of Pluronic L64 based formulations, as well as the interactions between polymer and DNA, is strongly dependent on the temperature and the medium used. These modifications have a direct impact on the in vivo efficiency of such vectors.
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