BACKGROUND Both bone marrow-derived mesenchymal stem cells (MSCs) and c-kit+ cardiac stem cells (CSCs) improve left ventricular remodeling in porcine models and clinical trials. We previously showed, using xenogeneic (human) cells in immunosuppressed animals with acute ischemic heart disease, that these 2 cell types act synergistically in combination. OBJECTIVES To more accurately model the clinical situation, we tested whether the combination of autologous MSCs and CSCs produced greater improvement of cardiac performance than MSCs alone in a nonimmunosuppressed porcine model of chronic ischemic cardiomyopathy. METHODS Three months after ischemia/reperfusion infusion injury, Gottingen mini-swine were injected transendocardially with MSCs alone (n = 6) or in combination with cardiac-derived CSCs (n = 8), MSCs, or placebo (vehicle; n = 6). Cardiac functional and anatomic parameters were assessed by cardiac magnetic resonance at baseline and before and after therapy. RESULTS Both groups of cell-treated animals exhibited significantly reduced scar size (MSCs: −44.1 ± 6.8%; CSC/MSC: −37.2 ± 5.4%; placebo: −12 ± 4.2%; p < 0.0001), increased viable tissue, and improved wall motion relative to placebo 3 months post-injection. Ejection fraction (EF) improved (MSCs: +2.9 ± 1.6; CSC/MSC: +6.9 ± 2.8; placebo: +2.5 ± 1.6 EF units; p = 0.0009), as did stroke volume, cardiac output, and diastolic strain, but only in the combination-treated animals, which also exhibited increased cardiomyocyte mitotic activity. CONCLUSIONS These findings illustrate that interactions between MSCs and CSCs enhance cardiac performance more than MSCs alone, establish the safety of autologous cell combination strategies, and support the development of second-generation cell therapeutic products.

Sustainable and reproducible large animal models that closely replicate the clinical sequelae of myocardial infarction (MI) are important for the translation of basic science research into bedside medicine. Swine are well accepted by the scientific community for cardiovascular research, and they represent an established animal model for preclinical trials for US Food and Drug Administration (FDA) approval of novel therapies. Here we present a protocol for using porcine models of MI created with a closed-chest coronary artery occlusion-reperfusion technique. This creates a model of MI encompassing the anteroapical, lateral and septal walls of the left ventricle. This model infarction can be easily adapted to suit individual study design and enables the investigation of a variety of possible interventions. This model is therefore a useful tool for translational research into the pathophysiology of ventricular remodeling and is an ideal testing platform for novel biological approaches targeting regenerative medicine. This model can be created in approximately 8–10 h.

BackgroundIntramyocardial injection of mesenchymal stem cells (MSCs) in chronic ischemic cardiomyopathy is associated with reverse remodeling in experimental models and humans. Here, we tested the hypothesis that allogeneic MSC therapy drives ventricular remodeling by producing durable and progressive scar size reduction in ischemic cardiomyopathy.Methods and ResultsGottingen swine (n=12) underwent left anterior descending coronary artery myocardial infarction (MI), and 3 months post‐MI animals received either intramyocardial allogeneic MSC injection (200 mol/L cells; n=6) or left ventricle (LV) catheterization without injection (n=6). Swine were followed with serial cardiac magnetic resonance imaging for 9 months to assess structural and functional changes of the LV. Intramyocardial injection was performed using an integrated imaging platform combining electroanatomical mapping unipolar voltage and 3‐dimensional cardiac magnetic resonance imaging angiography–derived anatomy to accurately target infarct border zone injections. MSC‐treated animals had a 19.62±2.86% reduction in scar size at 3 months postinjection, which progressed to 28.09±2.31% from 3 to 6 months postinjection (P<0.0001). MSC‐treated animals had unchanged end‐diastolic volume (EDV; P=0.08) and end‐systolic volume (ESV; P=0.28) from preinjection to 6 months postinjection, whereas controls had progressive dilatation in both EDV (P=0.0002) and ESV (P=0.0002). In addition, MSC‐treated animals had improved LV sphericity index. Percentage change in infarct size correlated with percentage change in EDV (r=0.68; P=0.01) and ESV (r=0.77; P=0.001). Ejection fraction increased from 29.69±1.68% to 35.85±2.74% at 3 months post‐MSC injection and progressed to 39.02±2.42% 6 months postinjection (P=0.0001), whereas controls had a persistently depressed ejection fraction during follow‐up (P=0.33).ConclusionIntramyocardial injection of allogeneic MSCs leads to a sustained and progressive reduction in infarct size, which in turn drives reverse remodeling and increases in ejection fraction. These findings support ongoing biological activity of cell therapy for substantial periods and suggest optimal end points for future clinical trials.

BACKGROUND Pim1 kinase plays an important role in cell division, survival, and commitment of precursor cells towards a myocardial lineage, and overexpression of Pim1 in ckit+ cardiac stem cell (CSC) enhances their cardioreparative properties. OBJECTIVES We sought to validate the effect of Pim1-modified CSCs in a translationally relevant large animal preclinical model of myocardial infarction (MI). METHODS Human CSCs (hCSCs, n = 10), hckit+ CSCs overexpressing Pim1 (Pim1+; n = 9), or placebo (n = 10) were delivered by intramyocardial injection to immunosuppressed Yorkshire swine (n = 29) 2 weeks after MI. Cardiac magnetic resonance and pressure volume loops were obtained before and after cell administration. RESULTS Whereas both hCSCs reduced MI size compared to placebo, Pim1+ cells produced a ~3-fold greater decrease in scar mass at 8 weeks post-injection compared to hCSCs (−29.2 ± 2.7% vs. −8.4 ± 0.7%; p < 0.003). Pim1+ hCSCs also produced a 2-fold increase of viable mass compared to hCSCs at 8 weeks (113.7 ± 7.2% vs. 65.6 ± 6.8%; p < 0.003), and a greater increase in regional contractility in both infarct and border zones (both p < 0.05). Both CSC types significantly increased ejection fraction at 4 weeks but this was only sustained in the Pim1+ group at 8 weeks compared to placebo. Both hCSC and Pim1+ hCSC treatment reduced afterload (p=0.02 and p=0.004, respectively). Mechanoenergetic recoupling was significantly greater in the Pim1+ hCSC group (p = 0.005). CONCLUSIONS Pim1 overexpression enhanced the effect of intramyocardial delivery of CSCs to infarcted porcine hearts. These findings provide a rationale for genetic modification of stem cells and consequent translation to clinical trials.