Abstract 2035: Adult Pluripotent Stem Cells: In Vitro Studies And Cell Engraftment In A Porcine Model Of Myocardial Infarction
Background: Since adult myocardium has limited regenerative capacity, the use of stem cells to regenerate infarcted myocardium is of great interest. The goals of this study were 1) to isolate a population of human Pluripotent Stem Cells (hPPSCs) from adult skeletal muscle able to differentiate along a cardiac lineage in vitro; 2) to evaluate a cell delivery method and retention in vivo; and 3) to determine the functional effect of hPPSCs following MI.
Methods: We developed an in vitro cardiac differentiation assay and analyzed hPPSC protein and gene expression before and after differentiation via immunoblotting, immunocytochemistry and RT-PCR. To track hPPSCs in vivo, we labeled cells with ferromagnetic particles and DiI. Yorkshire swine (25– 40 kg, n=11) underwent MI and reperfusion using a balloon inflation technique. Animals were treated with cyclosporine A and randomized into 3 groups to receive hPPSCs (group A) or vehicle control (group B) 2w after MI or hPPSCs immediately after MI (group C). Cells were delivered percutaneously, directly in and around the infarcted myocardium using a StilettoTM Endocardial Direct Injection Catheter System. Cardiac MRIs were performed using 1.5T magnet (in vivo) to measure infarct size at baseline and 2 months, and 4.7T (in vitro) to visualize engraftment. Sections from infarct and border zone were analyzed by Prussian blue staining (10 section/block) using a scoring system: 0= none, 1= 1–10, 2= 11–50, and 3= >50 cells/section.
Results: PPSCs expressed cardiac-specific isoforms of troponins and members of the GATA family of transcription factors after in vitro differentiation. Two months after MI, infarction size diminished in group C (from 17.6±2.7% to 5.8±0.8%) whereas smaller changes were observed for group A (from 10.4±2.7% to 8.4±8.7%) and group B (from 11.7±6.2% to 8.5±3%). MRI demonstrated the presence of ferromagnetic particles in border zones of infarcted areas. Histological analysis revealed an average engraftment score of 1.18 and 1.30 for groups A and C respectively.
hPPSCs derived from adult skeletal muscle can develop along a cardiac lineage in vitro.
hPPSCs are retained within the myocardium for at least 2 months after infarction.
Direct delivery of PPSCs appears to reduce infarct size.