The activities of team 3 involved important R&D projects with industrial partners (Technological Research Team-ERT). Another characteristic of the team associated with Paris 13 and Paris 7 Universities is the multidisciplinary expertise that covers chemistry, engineering, radiology, surgery, medical imaging and cardiology, allowing the involvement of different fields together in common projects. Original projects were thus developed in particular in cardiovascular tissue engineering (drug, gene, cell therapies), tools for in vitro diagnostic, and contrast agents for molecular imaging.

Biopolymers for therapeutic treatments: cell-, gene- and drug-delivery systems

Biotherapies with polymeric active drugs: Much of our research using potential polymeric drugs has used sulfated polysaccharides such as fucoidan, a sulfated polysaccharide from brown seaweeds for PN1 interaction (team 1) or as an inhibitor of extracellular matrix degradation. We have also demonstrated that low molecular weight fucoidan (LMWF) promotes revascularization in rat critical hindlimb ischemia, and in vitro tube formation in matrigel and VEGF165-induced EC chemotaxis, but not proliferation. LMWF binds with high affinity to VEGF165 and its receptors, but not to VEGF121. The effects of LMWF were much more pronounced than those of LMW heparin. Other effects of this polysaccharide and other biomimetic polysaccharides will be investigated for their interactions with chimiokines (SDF-1, RANTES), by integration in our team of 4 experienced members from EA3410 (University Paris 13, Bobigny).

3D-scaffolds for cell transplantation: Tissue engineering using biomatrices to generate three-dimensional constructs has emerged as an attractive strategy for delivering drugs and/or cells to regenerate damaged tissue, for instance in the treatment of myocardial infarction. During the last four years, our work allowed to prepare new 3D scaffolds for cell transplantation since the efficacy of cell engraftment by injection of a cell suspension is very low. We have evidenced the cytocompatibility of 3D-pullulan hydrogels according to a patented process. We have obtained films, dics and tubes for various applications (C. Levisage, CR1 Inserm recruited in 2006). Using a crosslinking process in aqueous solution, homogeneous, transparent, and easy to-handle pullulan gels were obtained. Discs for cell culture were obtained and molds were used to obtained tubular scaffolds (two Masters per year and 2 PhD students). We have also evaluated the effectiveness of a small-diameter polysaccharide-based tubular scaffold as an alternative arterial replacement. In a parallel work, mechanical properties of native arteries and scaffolds are investigated (I. Bataille and N Assoul). In Wistar adult rats, grafts as infrarenal aortic bypass withstood aortic blood pressure and exhibited physiological blood flow until 2 months post-surgery. Harvested grafts evidenced neointima formation on the luminal surface without intimal hyperplasia or aneurysm formation. This 2 mm polysaccharide-based material is a promising graft for implantation. Synthetic biocompatible hybrid meshes with suitable properties for tissue repair are also under investigation (Pr A. Pelle, Agence Biomedecine 2007), as well as biocompatible copolymers for stent coating (T. Avramoglou+1 PhD).

Cationized matrices for gene delivery: Cationized hydrogels are potential biomaterials to enhance the efficiency of local arterial gene transfer strategies. This project under the direction of Pr L. Feldman was carried out with 2 PhD students, one master student per year, and granted twice by Fondation de l’Avenir. A water-soluble cationic polysaccharide (DEAE-pullulan) was synthesized and the complexation of DNA was evidenced with DEAE-pullulan, but not with neutral pullulan. Using a plasmid vector (pSEAP), SEAP activity on SMCs was 150-fold higher than with pSEAP alone or pSEAP with neutral pullulan. 3 D discs were also obtained by chemical crosslink in less than a minute. Such DEAE-pullulan 3D matrices can be loaded with plasmid DNA, and protected it from DNase I degradation. Incubation of SMCs with pSEAP-loaded DEAE-pullulan discs resulted in significant gene transfer without cell toxicity. In addition, cationized pullulan tubular hydrogels were also demonstrated having a high affinity for plasmid DNA. The project for the following years will be devoted to the use of these new biomaterials to enhance the efficiency of local arterial gene transfer (plasmid DNA and siRNA) by coating on stents. For this purpose, we have already evaluated in collaboration with team 2 the effect of matrix metalloproteinase 2 (MMP2) inhibition in SMCs in vitro and ex vivo using small interfering RNA (siRNA). Our results demonstrated that in vitro MMP2-siRNA transfection markedly inhibits MMP2 gene expression and SMC migration and that ex vivo delivery of MMP2-siRNA in balloon-injured arteries reduced pro-MMP2 activity in neointimal cells. In vivo experiments are now required.