Abstract 552: Biological Properties and Regenerative Potential, in vitro and in vivo, of Human Cardiac Stem Cells Isolated from Each of the Four Chambers of the Adult Human Heart
The fact that the mammalian adult heart harbors resident stem cells has opened a new exciting field for cardiac biology and pathophysiology. Yet, many questions remain to be answered before exploiting the clinical potential of these cells. To this end, human myocardial samples were obtained during cardiac surgery or percutaneous LV catheterization from 19 patients with stable angina, cTnIneg unstable angina and mitral regurgitation. Ages ranged from 43 to 65 yrs. Biopsies were minced and explants from each of the four chambers were cultured to allow migration and expansion of the cells from the explants. The cells in the “halo” around the explants were then sorted to isolate human c-kitpos cells (hCSCs) that were analyzed for the expression of ‘stemness’ genes by real time RT-PCR, western blot, immunohistochemistry and FACS. All the human clones of c-kitpos CSCs obtained so far express high levels of c-kit, MDR-1, CD133, Oct-4, Nanog, Bmi-1, TERT, Wnt-1, β-catenin, Notch-1, and Hedgehog. Very few of these cells were Isl-1pos and they scored negative for CD34, CD45 and CD31. These cells cloned with high efficiency and some have undergone more than 62 passages without evidence of “crisis” or culture senescence. Thus, a clone can generate over 5x109 cells. After these passages cells remain TERTpos, have normal telomere length and do not express molecular markers of senescence. hCSCs form cardiospheres and differentiate into cardiomyocytes, vascular smooth muscle and endothelial cells. When grown in medium conditioned by TGF-β, BMP-2 and Wnt-5, hCSCs down-regulate stemness genes and selectively differentiate into beating cardiomyocytes. Importantly, when injected into infarcted nu/nu rat hearts, they form histological and functional human myocardium. At the level of analysis performed so far, there are no detectable differences among the isolated cells that can be attributed to the chamber of origin. In conclusion, the phenotype of hCSCs is similar to the one previously described for rodent CSCs. hCSCs can be successfully and routinely isolated from small myocardial samples from all four cardiac chambers, expanded to large numbers and maintained undifferentiated or differentiated in culture, as desired.