Background
The combination of autologous mesenchymal stem cells (MSCs) and cardiac stem cells (CSCs) synergistically reduces scar size and improves cardiac function in ischemic cardiomyopathy. Whereas allogeneic (allo-)MSCs are immunoevasive, the capacity of CSCs to similarly elude the immune system remains controversial, potentially limiting the success of allogeneic cell combination therapy (ACCT).
Objective
We tested the hypothesis that ACCT synergistically promotes cardiac regeneration without provoking immunologic reactions.
Methods
Gottingen swine with experimental ischemic cardiomyopathy were randomized to receive transendocardial injections of either allo-MSC + allo-CSC (ACCT: 200 million MSCs/1 million CSCs, n=7), 200 million allo-MSC (n=8), 1 million allo-CSC (n=4), or placebo (Plasma-Lyte A, n=6)]. Swine were assessed by cardiac magnetic resonance imaging (cMR) and pressure volume catheterization. Immune response was tested by histological analyses.
Results
Both ACCT and allo-MSCs reduced scar size by −11.1±4.8%, (p=0.012) and −9.5±4.8 (p=0.047), respectively. Only ACCT, but not MSC or CSC, prevented ongoing negative remodeling by offsetting increases in chamber volumes. Importantly, ACCT exerted the greatest effect on systolic function, improving the end-systolic pressure volume relation (+0.98±0.41 mmHg/mL, p=0.016) The ACCT group had more phospho-histone H3 (pHH3)+ (a marker of mitosis) cardiomyocytes (p=0.04), and non-cardiomyocytes (p=0.0002) compared to the placebo group in some regions of the heart. Inflammatory sites in ACCT and MSC swine contained immunotolerant CD3+/CD25+/FoxP3 regulatory T cells (p<0.0001). Histologic analysis showed absent to low grade inflammatory infiltrates without cardiomyocyte necrosis.
Conclusion
ACCT demonstrates synergistic effects to enhance cardiac regeneration and left ventricular functional recovery in a swine model of chronic ischemic cardiomyopathy without adverse immunological reaction. Clinical translation to humans is warranted.