Dose-response to cytoskeletal-antigen specific immunoliposome therapy for preservation of myocardial viability and function in langendorff instrumented rat hearts

Targeting regenerative exosomes to myocardial infarction using cardiac homing peptide

Rationale: Cardiac stem cell-derived exosomes have been demonstrated to promote cardiac regeneration following myocardial infarction in preclinical studies. Recent studies have used intramyocardial injection in order to concentrate exosomes in the infarct. Though effective in a research setting, this method is not clinically appealing due to its invasive nature. We propose the use of a targeting peptide, cardiac homing peptide (CHP), to target intravenously-infused exosomes to the infarcted heart. Methods: Exosomes were conjugated with CHP through a DOPE-NHS linker. Ex vivo targeting was analyzed by incubating organ sections with the CHP exosomes and analyzing with fluorescence microscopy. In vitro assays were performed on neonatal rat cardiomyocytes and H9C2 cells. For the animal study, we utilized an ischemia/reperfusion rat model. Animals were treated with either saline, scramble peptide exosomes, or CHP exosomes 24 h after surgery. Echocardiography was performed 4 h after surgery and 21 d after surgery. At 21 d, animals were sacrificed, and organs were collected for analysis. Results: By conjugating the exosomes with CHP, we demonstrate increased retention of the exosomes within heart sections ex vivo and in vitro with neonatal rat cardiomyocytes. In vitro studies showed improved viability, reduced apoptosis and increased exosome uptake when using CHP-XOs. Using an animal model of ischemia/reperfusion injury, we measured the heart function, infarct size, cellular proliferation, and angiogenesis, with improved outcomes with the CHP exosomes. Conclusions: Our results demonstrate a novel method for increasing delivery of for treatment of myocardial infarction. By targeting exosomes to the infarcted heart, there was a significant improvement in outcomes with reduced fibrosis and scar size, and increased cellular proliferation and angiogenesis.

Liposomes for cardiovascular targeting

Liposome-based pharmaceuticals used within the cardiovascular system are reviewed in this article. The delivery of diagnostic and therapeutic agents by plain liposomes and liposomes with surface-attached targeting antibodies or polyethylene glycol to prolong their circulation time and accumulation at vascular injuries, ischemic zones or sites of thrombi are also discussed. An overview of the advantages and disadvantages of liposome-mediated in vitro, ex vivo and in vivo targeting is presented, including discussion of the targeting of liposomes to pathological sites on the blood vessel wall and a description of liposomes that can be internalized by endothelial cells. Diagnostic liposomes used to target myocardial infarction and the relative importance of liposome size, targetability of immunoliposomes and prolonged circulation time on the efficiency of sealing hypoxia-induced plasma membrane damage to cardiocytes are discussed as a promising approach for therapy. The progress in the use of targeted liposomal plasmids for the transfection of hypoxic cardiomyocytes and myocardium is presented. Stent-mediated liposomal-based drug delivery is also reviewed briefly.

Cytoskeletal-antigen specific immunoliposomes: preservation of myocardial viability

Pathological conditions such as hypoxia and inflammation can lead to the development of cell membrane-lesions. The presence of these membrane-lesions leads to egress of intracellular macromolecules as well as exposure of intracellular microenvironment to the extracellular milieu resulting in necrotic cell death. An intracellular structure that becomes exposed to the extracellular environment is myosin, a cytoskeletal antigen. We had hypothesized that cell viability can be preserved in nascent necrotic cells if the cell membrane lesions were sealed and the injurious conditions removed. Cell membrane lesion sealing and preservation of cell viability were achieved by the application of Cytoskeletal-antigen Specific ImmunoLiposomes (CSIL) as molecular "Band-Aid" that initially plugs the holes with subsequent sealing of the lesions. Anti-myosin antibody was chosen as the cytoskeleton-antigen specific antibody to develop CSILs, because antimyosin antibody is highly specific for targeting myosin exposed through myocardial cell membrane lesions in various cardiomyopathies. Liposomes are biocompatible lipid bilayer vesicles that have been used in many biological applications for several decades. This chapter will be limited to the description of CSIL therapy to ex vivo studies in adult mammalian hearts. Due to page limitations, cell culture, gene delivery and in vivo studies will not be included. Therapeutic efficacy of CSIL in preservation of myocardial viability as well as function (by left ventricular developed pressure measurements) as assessed in globally ischemic Langendorff instrumented hearts is both dose and time dependent. This approach of cell membrane lesion repair and sealing may have broader applications in other cell systems.