Abstract 16420: Human Cardiac Stem Cells (hCSCs) Carrying the Mother DNA Constitute a Novel Class of Resident Stem Cells With Markedly Superior Growth Reserve
Cell therapy for the failing heart requires recognition of the most powerful cell for myocardial regeneration. Here, we established whether hCSCs divide by symmetric and asymmetric DNA segregation, and whether these patterns of growth result in stem cells with distinct function. Cell multiplication by non-random DNA partitioning would prevent genetic mutations and preserve cell growth. Therefore, hCSCs were isolated from 24 samples and labeled by BrdU; BrdU-positive and negative cells reflected random and non-random chromatid segregation, respectively. Single cell clones were then obtained in Terasaki plates; 137 of 1,885 clones showed only 1 BrdU-positive hCSC, indicating that 7% of founder hCSCs divided retaining the mother DNA. Non-random DNA segregation was confirmed by detecting BrdU in one set of anaphase chromosomes only. An inverse relationship was found between hCSCs carrying the mother DNA and age; this stem cell class decreased linearly in patients 1 to 80 years of age. In these clones, hCSCs with the new DNA were negative for p16INK4a, p53 and ATM kinase, suggesting that cell growth was maintained in this hCSC pool as well. However, differences existed in the growth behavior of hCSCs dividing by random and non-random DNA segregation. At 7 and 12 days after plating, the number of clonal cells formed by hCSCs with old DNA was 1.8-and 4.1-fold higher than in clones generated by hCSCs with new DNA, respectively; telomere length in hCSCs with mother DNA was one kbp longer and telomerase activity was significantly higher. Cell karyotype did not change in long-term cultures of both hCSC classes. hCSCs were transfected with a plasmid containing siRNA for left-right dynein motor protein (LRD). Control hCSCs were transduced with scrambled siRNA. Downregulation of LRD in founder hCSCs led to clones formed exclusively by cells which divided by symmetric chromatid segregation and carried only new DNA. Conversely, 5% of clones from control hCSCs showed single BrdU bright cells, reflecting the expected number of hCSCs that replicated by asymmetric chromatid segregation. In conclusion, hCSCs which divide by non-random DNA partitioning form a younger stem cell progeny with superior growth reserve and potentially greater reparative capacity for the damaged heart.
- © 2011 by American Heart Association, Inc.