The bottleneck stent model for chronic myocardial ischemia and heart failure in pigs.

A large animal model of chronic myocardial ischemia and heart failure is crucial for the development of novel therapeutic approaches. In this study we developed a novel percutaneous one- and two-vessel model for chronic myocardial ischemia using a stent coated with a polytetrafluoroethylene tube formed in a bottleneck shape. The bottleneck stent was implanted in the proximal left anterior descending (LAD) or proximal circumflex artery (LCX), or in both proximal LCX and mid LAD 1 wk later (2-vessel model), and pigs were followed for 4-5 wk. Ejection fraction (EF), infarct size, collateral growth, and myocardial perfusion were assessed. Pigs were given antiarrhythmic medication to prevent sudden death. The occlusion time of the bottleneck stent and the timing of myocardial infarction could be modulated by the duration of antiplatelet medication. Fractional flow reserve measurements and positron emission tomography imaging showed severe ischemia after bottleneck stenting covering over 50% of the left ventricle in the proximal LAD model. Complete coronary occlusion was necessary for significant collateral growth, which mostly had occurred already during the first wk after the stent occlusion. Dynamic and competitive collateral growth patterns were observed. EF declined from 64 to 41% in the LCX model and to 44% in the LAD model 4 wk after stenting with 12 and 21% infarcted left ventricle in the LCX and LAD models, respectively. The mortality was 32 and 37% in the LCX and LAD models but very (71%) high in the two-vessel disease model. The implantation of a novel bottleneck stent in the proximal LAD or LCX is a novel porcine model of reversible myocardial ischemia (open stent) and ischemic heart failure (occluded stent) and is feasible for the development of new therapeutic approaches.

Amphiphilic phthalocyanines in polymeric micelles: a supramolecular approach toward efficient third-generation photosensitizers.

In this paper we describe a straightforward supramolecular strategy to encapsulate silicon phthalocyanine (SiPc) photosensitizers (PS) in polymeric micelles made of poly(ε-caprolactone)-b-methoxypoly(ethylene glycol) (PCL-PEG) block copolymers. While PCL-PEG micelles are promising nanocarriers based on their biocompatibility and biodegradability, the design of our new PS favors their encapsulation. In particular, they combine two axial benzoyl substituents, each of them carrying either three hydrophilic methoxy(triethylenoxy) chains (1), three hydrophobic dodecyloxy chains (3), or both kinds of chains (2). The SiPc derivatives 1 and 2 are therefore amphiphilic, with the SiPc unit contributing to the hydrophobic core, while lipophilicity increases along the series, making it possible to correlate the loading efficacy in PCL-PEG micelles with the hydrophobic/hydrophilic balance of the PS structure. This has led to a new kind of third-generation nano-PS that efficiently photogenerates 1O2, while preliminary in vitro experiments demonstrate an excellent cellular uptake and a promising PDT activity.

Macrophage selective photodynamic therapy by meta-tetra(hydroxyphenyl)chlorin loaded polymeric micelles: A possible treatment for cardiovascular diseases.

Selective elimination of macrophages by photodynamic therapy (PDT) is a new and promising therapeutic modality for the reduction of atherosclerotic plaques. m-Tetra(hydroxyphenyl)chlorin (mTHPC, or Temoporfin) may be suitable as photosensitizer for this application, as it is currently used in the clinic for cancer PDT. In the present study, mTHPC was encapsulated in polymeric micelles based on benzyl-poly(ε-caprolactone)-b-methoxy poly(ethylene glycol) (Ben-PCL-mPEG) using a film hydration method, with loading capacity of 17%. Because of higher lipase activity in RAW264.7 macrophages than in C166 endothelial cells, the former cells degraded the polymers faster, resulting in faster photosensitizer release and higher in vitro photocytotoxicity of mTHPC-loaded micelles in those macrophages. However, we observed release of mTHPC from the micelles in 30min in blood plasma in vitro which explains the observed similar in vivo pharmacokinetics of the mTHPC micellar formulation and free mTHPC. Therefore, we could not translate the beneficial macrophage selectivity from in vitro to in vivo. Nevertheless, we observed accumulation of mTHPC in atherosclerotic lesions of mice aorta's which is probably the result of binding to lipoproteins upon release from the micelles. Therefore, future experiments will be dedicated to increase the stability and thus allow accumulation of intact mTHPC-loaded Ben-PCL-mPEG micelles to macrophages of atherosclerotic lesions.

Vascular oligonucleotide transfer facilitated by a polymer-coated stent.

To evaluate the potential of clinically used phosphorylcholine (PC)-coated stents for their ability to load and release small decoy oligonucleotides (ODNs). Stents were loaded with 41 +/- 6 microg ODNs. Ex vivo deployment of ODN-loaded stents in explanted rabbit aortas showed significant vascular ODN transfer, with 18 +/- 12% of intimal or medial cell nuclei containing ODNs. In proof-of-principle in vivo experiments (using the double-injury rabbit model) there was no difference in fluorescent signal intensity between animals receiving ODNloaded stents or controls. However, a significant increase in signal intensity was detected in the kidneys of animals receiving ODN-loaded stents. PC-coated stents can be loaded with ODNs. Despite successful ex vivo ODN deposition and nuclear uptake in the vessel wall, in vivo vascular ODN transfer was not achieved. Rapid intravascular release of ODN before implantation and potential vascular barriers for gene transfer are most likely responsible for the currently unsatisfactory in vivo release kinetics.

Nonviral gene delivery methods in cardiovascular diseases.

Nonviral gene delivery methods with naked plasmids and various plasmid carrier complexes have been used for intravascular, intramuscular and periadventitial gene delivery to cardiovascular system. Efficacy, homogenity and quality of the nonviral gene delivery complexes can be significantly affected by the way they are produced. This chapter presents basic methods to produce nonviral gene delivery complexes and describes common models to test their properties in cardiovascular applications in vivo.

Targeted delivery via avidin fusion protein: intracellular fate of biotinylated doxorubicin derivative and cellular uptake kinetics and biodistribution of biotinylated liposomes.

In this study, avidin-biotin technology was combined with a multifunctional drug carrier modality i.e. liposomes to achieve an active and versatile targeting approach. The anti-cancer drug doxorubicin (DOX) was modified with direct biotinylation (B-DOX) (Allart et al., 2003), or encapsulated in biotinylated sterically stabilized pH-sensitive liposomes (BL-DOX), and targeted to the lentiviral vector transduced cells expressing an avidin fusion protein on the cell membrane (Lehtolainen et al., 2003; Lesch et al., 2009). The direct biotinylation of doxorubicin improved cell internalization in rat glioma (BT4C) cells expressing avidin fusion protein receptor but cell toxicity was reduced by 78-fold due to impaired nuclear localization. In contrast, liposomal formulations restored the biological activity of the DOX in several cell lines. However, mainly due to uptake via non-specific pathways the active targeting of BL-DOX was negligible in both in vitro and in vivo studies. Active targeting with multifunctional drug carrier systems is challenging and further studies will be needed to optimize the properties of targeted drug carrier and receptor expression systems.

Safety profile of plasmid/liposomes and virus vectors in clinical gene therapy.

Despite of more than 500 gene therapy trials worldwide very little systematic safety information is available from gene therapy. Safety information was collected from 146 consecutive patients who participated in three randomized, controlled phase II gene therapy trials in cardiovascular diseases and malignant glioma using adenoviruses, plasmid/liposomes and retrovirus packaging cells. Total follow-up time of the patients was 78794 days which equals 1.5 years per patient. The main outcome measures were serious adverse events, other adverse events and changes in general laboratory parameters. Except fever and increases in CRP values plasmid/liposomes were safe and well tolerated. The incidence of serious adverse events in adenovirus-treated patients was 0.9 and 4.0/10000 patient days in cardiovascular and malignant glioma trials as compared to 0.5 and 2.1 in randomized control patients, respectively. Transient fever, leukopenia and increases in CRP and liver enzymes were detected in virus-treated patients. No deaths from side effects or no new cancers were associated with gene therapy. It is concluded that gene therapy, like any other therapy, is associated with side effects which depend on the administered vector, dose, and route of delivery and properties of the transgene. However, given the limitations of this study and length of the follow-up, the safety profile of gene therapy seems to be acceptable for the treatment of severe human diseases.

The use of low-molecular-weight PEIs as gene carriers in the monkey fibroblastoma and rabbit smooth muscle cell cultures.

BACKGROUND: Polyethylenimines (PEIs) and cationic polymers have been used successfully in gene delivery. In earlier reports, only large PEIs (MW>10 000) have shown significant transfection efficiency. In the present study, the roles of small PEIs (MW 700 and 2000) were studied as additional compounds to see if they can improve gene delivery with cationic liposomes. METHODS: The TKBPVlacZ expression plasmid was transfected in the CV1-P (monkey fibroblastoma) and SMC (rabbit smooth muscle) cell lines using various combinations of PEIs (MW 700, 2000, and 25 000) and Dosper liposomes. The transfection efficiency was determined with the fluorometric ONPG (o-nitrophenol-beta-D-galactopyranoside) assay and histochemical X-gal staining. The toxicity of the transfection reagents was estimated by the MTT [3-(4,5-dimethylthiazolyl-2)-2,5-diphenyl tetrazolium bromide] assay. RESULTS: Transfection of TKBPVlacZ plasmid by the small PEIs (MW 700 and 2000) combined with Dosper liposomes was associated with high expression of the lacZ reporter gene in the CV1-P and SMC cell lines. The transfection efficiencies of the low-molecular-weight PEI/liposome combinations were several fold higher than those of PEIs or liposomes alone. PEI/liposome combinations had no toxicity on the cell lines tested. CONCLUSIONS: The low-molecular-weight PEIs could be used successfully for gene delivery when combined with the cationic liposomes, resulting in a synergistic increase of the transfection efficiency in both cell lines studied.

Increased vascularity detected by digital subtraction angiography after VEGF gene transfer to human lower limb artery: a randomized, placebo-controlled, double-blinded phase II study.

Vascular endothelial growth factor (VEGF) gene therapy may be useful for the treatment of lower-limb ischemia. The objectives of this study were to evaluate safety and angiographic and hemodynamic responses of local catheter-mediated VEGF gene therapy in ischemic lower-limb arteries after percutaneous transluminal angioplasty (PTA). For this study, we recruited patients with chronic lower-limb ischemia and atherosclerotic infrainguinal occlusion or stenosis suitable for PTA. In the study, 18 patients received 2x10(10) plaque-forming units (pfu) VEGF-adenovirus (VEGF-Ad), 17 patients received VEGF-plasmid/liposome (VEGF-P/L; 2000 microg of VEGF plasmid, 2000 microl of DOTMA:DOPE), and 19 control patients received Ringer's lactate at the angioplasty site. Digital subtraction angiography (DSA) was used to evaluate vascularity before, immediately after, and 3 months after the PTA. Clinical follow-up data, basic laboratory tests, and ankle-brachial index (ABI) were evaluated. Primary endpoint was DSA analysis of vascularity, and secondary endpoints were restenosis rate, Rutherford class, and ABI after 3 months follow-up. No major gene transfer-related side effects or differences in laboratory tests were detected between the study groups. However, anti-adenovirus antibodies increased in 61% of the patients treated with VEGF-Ad. For the primary endpoint, follow-up DSA revealed increased vascularity in the VEGF-treated groups distally to the gene transfer site (VEGF-Ad P=0.03, VEGFP/L P=0.02) and in the VEGF-Ad group in the region of the clinically most severe ischemia (P=0.01). As for the secondary endpoints, mean Rutherford class and ABI showed statistically significant improvements in the VEGF-Ad and VEGF-P/L groups, but similar improvements were also seen in the control patients. We conclude that catheter-mediated VEGF gene therapy is safe and well tolerated. Angiography demonstrated that VEGF gene transfer increased vascularity after PTA in both VEGF-Ad- and VEGF-P/L-treated groups.