Abstract 382: Cardiogenicity and Regenerative Potential of Cardiac-derived Stem Cells Isolated from Adult Human and Porcine Endomyocardial Biopsy Specimens
Percutaneous endomyocardial biopsy specimens from 70 adult patients grown in primary culture developed multi-cellular clusters known as cardiospheres, which were plated to yield cardiosphere-derived cells (CDCs). Most CDCs were CD105+ (99.1±0.2%), with significant pluralities that were c-Kit+ (17.0±6.0%), CD90+ (36.1±7.8%), CD34+ (6.4±0.9%), and CD31+ (10.8±3.7%). These cells were also largely MDR1-, CD133−, CD45−, and negative for a cocktail of blood lineage markers. Two distinct subpopulations were identified by FACS analysis: c-Kit+ CDCs and CD90+ CDCs. The mesenchymal-like CD105+ CD90+ subpopulation may provide physical or secretory support to the c-Kit+ sub-population during CDC expansion. Human CDCs also expressed α-sarcomeric actin and von Willebrand factor most prominently in small, proliferating cells. Human and porcine CDCs co-cultured with neonatal rat ventricular myocytes cycled calcium in sync with neighboring myocytes, demonstrated nodal- and ventricular-like action potentials, exhibited endogenous inward sodium currents, inwardly rectifying potassium currents, and L-type calcium currents when transduced with the β-subunit of the L-type calcium channel. To assess regenerative potential, human CDCs were injected into the border zone of acute myocardial infarcts in immunodeficient mice, with histological examination and echocardiographic left ventricular function as endpoints. CDC-injected animals showed no deterioration of LV function from 2 days post-MI (LVEF=45.2±4.8%) to 3 weeks post-MI (LVEF=42.8±3.3%, n=11), in contrast to fibroblast-injected animals (LVEF=42.8±4.3% at 2 days vs. 24.7±1.9% at 3 weeks post-MI, p<0.01, n=7). CDCs engrafted and migrated into the infarct zone and surrounding viable tissue. After 3 weeks, the CDC-treated group had a higher percentage of viable myocardium within the infarct zone as compared to the fibroblast-treated control group (24.7±1.2% vs 16.4±1.9%, p<0.01) and a higher LVEF as compared to the fibroblast-treated group (p<0.01). CDCs within the viable myocardium could be found expressing α-sarcomeric actin and von Willebrand factor. We conclude that CDCs are cardiogenic, produce cardiac regeneration and improve heart function in a mouse infarct model.